BRPI0315677B1 - MIMO WLAN SYSTEM - Google Patents

Description

"MIMO WLAN System" BACKGROUND

Field The present invention is generally related to data communication and more specifically to a wireless local area network (WLAN) multi-input and multi-output (MIMO) communication system.

Background Wireless communication systems are widely deployed to provide various types of communication, such as voice, packet data, and so on. Such systems may be multiple access systems capable of supporting communication with multiple users sequentially or simultaneously by sharing available system resources. Examples of multiple access systems include code division multiple access (CDMA), time division multiple access (TDMA), and frequency division multiple access (FDMA) systems.

Wireless Local Area Networks (WLANs) are also widely deployed to enable communication between wireless electronic devices (for example, computers} over a wireless link. A WLAN can employ access points {or base stations) that operate as hubs and provide connectivity to wireless devices. Access points can also connect (or "bridge") to WLAN with wired LANs, thus allowing wireless devices to access LAN resources F, m a wireless communication system Radio frequency (RF) modulated signal from a transmitting unit can reach a receiving unit through various propagation paths Characteristics of propagation paths typically vary over time due to various factors such as fading and multipathing. diversity against detrimental effects of path and improve performance, multiple transmitting and receiving antennas may be used.If propagation paths between transmitting and receiving antennas are linearly independent (that is, transmission over a path is not formed as a linear combination). broadcasts of the other routes), which is generally true, at least to some degree, so o The likelihood of receiving a data transmission correctly increases as the number of antennas grows. In general, diversity increases and performance improves as the number of transmitting and receiving antennas grows.

A MIMO system employs multiple (NT) transmitting antennas and multiple (NP;) receiving antennas for data transmission. A MIMO channel formed by NT transmitting antennas and NR receiving antennas can be decomposed into Ms spatial channels, with Ns £ min. Each of the Ms space channels corresponds to one dimension. The MIMO system can provide better performance (for example, higher transmission capacity and / or greater reliability) if the additional dimensions created by the multiple transmitter and receiver antennas are used.

Resources for a given communication system are typically limited by various restrictions and regulatory requirements and other practical considerations. However, the system may be required to support a number of endpoints, provide multiple services, achieve certain performance goals, and so on.

There is therefore a demand in the area for a MIMO WLAN system capable of supporting multiple users and providing high system performance.

SUMMARY Described herein is a multi-access MIMO WLAN system having various capabilities and capable of high performance. In one embodiment, the system employs MIMO and Frequency Division Orthogonal Multi-Multiplexing (OFDM) to achieve high throughput, combat detrimental path effects, and provide other benefits. Each access point in the system can support multiple user terminals. Resource allocation in downlink and uplink depends on user terminal requirements, channel conditions, and other factors.

Also provided herein is a channel structure that supports efficient downlink and uplink transmissions. The channel structure comprises various transport channels that can be used for various functions, such as system parameter signaling and resource assignment, downlink and uplink data transmissions, random system access, and so on. Various attributes of such transport channels can be configured, which allows the system to easily adapt to changing channel and load conditions. Multiple transmission modes and rates are supported by the MIMO WLAN system for high transmission capacity when supported by channel conditions and user terminal capabilities. Rates can be set based on estimates of channel conditions and can be independently selected for downlink and uplink. Different transmission modes may also be used depending on the number of antennas on the user terminals and channel conditions. Each transmission mode is associated with different spatial processing at the transmitter and receiver and can be selected for use under different operating conditions. Spatial processing facilitates data transmission from multiple transmitting antennas and / or data reception with multiple receiver antennas for higher diversity and / or transmission capacity.

In one embodiment, the MIMO WLAN system uses a single frequency band for downlink and uplink, which share the same operating band using time division duplexing (TDD). For a TDD system, downlink and uplink channel responses are reciprocal. Calibration techniques are provided herein to determine and account for differences in frequency responses of the transmit / receive chains at the access point and user terminals. Also described herein are techniques for simplifying spatial processing at the access point and user terminals by taking advantage of the reciprocal nature of downlink and uplink and calibration. ft also provided a pilot structure with various types of pilots used for different functions. As an example, a beacon pilot can be used for frequency and system acquisition, a MIMO pilot can be used for channel estimation, a directed reference (ie a directed pilot) can be used for better estimation. channel and a carrier pilot can be used for phase tracking. Various control loops are also provided for proper system operation. Rate control can be done independently on downlink and uplink. Power control may be performed for certain transmissions (eg fixed rate services). Timing control can be used for uplink transmissions to account for different propagation delays from user terminals located throughout the system. Random access techniques are also provided to allow user terminals to access the system. These techniques support multiple user terminal access to the system, quick acknowledgment of system access attempts, and agile downlink / uplink resource allocation.

The various aspects and embodiments of the invention will be described in more detail below.

BRIEF DESCRIPTION OF DRAWINGS

The features and nature of the present invention will become clearer from the following detailed description when taken in conjunction with the drawings, in which similar numerical references identify corresponding items and in which: Figure 1 shows a MIMO WLAN system; Figure 2 shows a layer structure for the MIMO WLAN system;

Figures 3Ά, 3B and 3C show a TDD-TDM frame structure, an FDD-TDM frame structure and an FDD-CDM frame structure, respectively; Figure 4 shows the TDD-TDM frame structure with five BCH, FCCH, FCH, RCH and RACH transport channels;

Figures 5A to 5G show various protocol data unit (PDU) formats for the five transport channels; Figure 6 shows a structure for an FCH / RCH packet; Figure 7 shows one access point and two user terminals;

Figures 8A, 9A and 10A show three transmitter units for diversity, spatial multiplexing and beam steering modes, respectively;

Figures 8B, 9B, and 1GB show three TX diversity processors for diversity, spatial multiplexing, and beam steering modes, respectively; Figure 8C shows an OFDM modulator; Figure 8D shows an OFDM symbol; Figure 11A shows a framing unit and shuffler with a TX data processor; Figure 11B shows an encoder and a repeat / punch unit within the TX data processor; Figure 11C shows another TX data processor that can be used * for spatial multi-taxation mode;

Figures 12A and 12B show a state diagram for operation of a user terminal; Figure 13 shows a timeline for KACH;

Figures 14A and 14B show processes for controlling downlink and uplink transmission rates, respectively; Figure 15 shows the operation of a power control loop; and Figure 16 shows a process for adjusting the uplink timing of a user terminal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The term "exemplary" is used herein to mean "serving as an example, case, or illustration". Any design or embodiment described herein as "exemplary" should not necessarily be considered as preferred or advantageous over other embodiments or schemes. I. General System Figure 1 shows a MIMO WLAN 100 system that supports multiple users and is capable of implementing various aspects and embodiments of the invention. The MTMQ WLAN 100 system includes multiple access points (APs) 110 that support communication to multiple user terminals (UTs) 120.

For simplicity, only two access points 110 are shown in Figure 1. An access point is generally a fixed station that is used for communication with user terminals. An access point may also be referred to as a base station or some other terminology.

User terminals 120 may be dispersed throughout the system. Each user terminal can be a fixed or mobile terminal that can communicate with the access point. A user terminal may also be referred to as a mobile station, a remote station, an access terminal, a user equipment (UE), a wireless device, or some other terminology. Each user terminal can communicate with one or possibly multiple access points via downlink and / or uplirtk at any time. Downlink (ie the direct .link) refers to the transmission from the access point to the user terminal, while uplínk (ie the reverse link) refers to the transmission from the user terminal to the access point. .

In Figure 1, access point 110a communicates with user terminals 120a through 120f and access point 110b communicates with user terminals 120f through 120k. Depending on the specific design of system 100, an access point may communicate with multiple user terminals simultaneously (for example across multiple code channels or subbands) or sequentially (for example across multiple time partitions). . At any time, a user terminal may receive downlink transmissions from one or multiple access points. Downlink transmission from each access point may include overhead data intended to be received by multiple user terminals, user-specific data intended to be received by specific user terminals, other data types, or any combination of such data. . Overhead data may include pilot, page and broadcast messages, system parameters, and so on. The MIMO WLAN system is based on a centralized controller network architecture. In this way, a system controller 130 couples to access points 110 and can also couple to other systems and networks. As an example, system controller 130 may be coupled to a packet data network (PDN), a wired local area network (LAN), a wide area network {WAN}, the Internet, and a public telephone network. (PSTN), a cellular communication network, and so on. System controller 130 may be designed to perform various functions, such as (1) coordinating control for access points coupled to it, (2) data routing between such access points, (3) access and control of communication with the user terminals served by such access points or so on. The MIMO WLAN system may be able to provide high transmission capacity with significantly greater coverage than conventional WLAN systems. The MIMO WLAN system can support synchronous, asynchronous and synchronous data / voice services. The MIMO WLAN system can be designed to provide the following features: • High reliability of service • Guaranteed quality of service (QoS) • High instantaneous data rates • High spectral efficiency • Extended range The MIMO WLAN system can be operated in several frequency bands (for example, the 2.4 GHz or 3.x GHz U-NII bands), subject to the bandwidth and emission restrictions specific to the selected operating band. The system is designed to support outdoor and indoor deployments with a typical maximum cell size and 1 km or less. The system supports fixed terminal applications, although some modes of operation may also support portable and limited mobility operation. 1. MIMO, MISO and SIMQ.

In a specific embodiment, and as described throughout the specification, each access point is equipped with four transmitting and receiving antennas for transmitting and receiving data, wherein the same four antennas are used for transmitting and receiving. The system also supports the case where the device's transmitting and receiving antennas (for example, access point, user terminal} are not shared, although such a setting typically provides worse performance than when antennas are shared. WLAN may also be designed such that each access point is equipped with some other number of transmitter / receiver antennas Each user terminal may be equipped with a single transmitter / receiver antenna or multiple transmitter / receiver antennas for transmitting and receiving. The number of antennas employed by each type of user terminal may depend on several factors such as, for example, the services to be supported by the user terminal (for example, voice, data, or both}, considerations regarding at cost, regulatory restrictions, safety issues, and so on.

For a given multi-antenna access point pairing and multi-antenna user terminal pairing, a MIMO channel is formed by the MT transmitting antennas and NK receiving antennas available for use for data transmission. Different MIMO channels are formed between the access point and different user terminals of multiple antennas. Each MIMO · channel can be decomposed into Nspace channels, with Mg <min {NT, NP}. Ng data streams can be transmitted through the space channels. Spatial processing is required at a receiver and may or may not be performed at a transmitter in order to transmit multiple data streams through the spatial channels.

The Ns space channels may or may not be octagonal to each other. This depends on a number of factors, such as (1} whether or not spatial processing was performed on the transmitter to obtain orthogonal spatial channels and (2) whether or not spatial processing on the transmitter and receiver was successful in orthogone 1ization. If no spatial processing is performed on the transmitter, then the N spatial channels can be formed with N transmitting antennas and are probably not orthogonal to each other.

Ng spatial channels can be orthogonalized by decomposing into a channel response matrix for the MINO channel as described below. Each space channel is referred to as a MIMO channel autode if the Ng space channels are orthogonized using decomposition, which requires spatial processing at both the transmitter and receiver as described below. In such a case, the N data streams may be transmitted orthogonevally through the autodode Ns. However, an automode usually refers to a theoretical framework. Nspace channels typically are not completely orthogonal to each other due to several reasons. As an example, spatial channels would not be orthogonal if (1) the transmitter is unaware of the MIMO channel, or (2) the transmitter and / or receiver have an imperfect estimate of the MIMO channel. For simplicity, in the following description, the term "eigenmode" is used to denote the case when an attempt is made to orthogonalize the space channels using decomposition, even though the attempt may not be completely successful. due, for example, to an imperfect channel estimate.

For a given number (for example, four} antennas on the access point, the number of space channels available to each user terminal depends on the number of antennas employed by that user terminal and the characteristics of the wireless MIMO channel that couples the Access Point Antennas and User Terminal Antennas If a user terminal is equipped with an antenna, then the four antennas on the access point and the single antenna on the user terminal form a multi-input and output channel. -tmicâ (MISO) for downlink or single-channel and multiple-output (SIMO) channel for uplink The MIMO WLAN system can be designed to support multiple transmission modes. Transmission Modes Supported by an Exemplary MIMO WLAN System Scheme ♦ Table 1 For simplicity, the term "diversity" refers to the diversity of transmission in the following description, unless otherwise noted. Available transmission modes for downlink and uplink for each user terminal depend on the number of antennas employed on the user terminal. Table 2 lists the transmission modes available for different types of downlink and uplink terminals, assuming multiple (for example, four) antennas on the access point.

Table 2 For downlink, all transmission modes except spatial multi-mode can be used for single antenna user terminals and all transmission modes can be used for multi-antenna user terminals. For uplink, all transmission modes can be used for multi-antenna user terminals, whereas single antenna user terminals use SIMO mode to transmit data from the only available antenna, h receiving diversity (ie receiving a data transmission with multiple receiver antennas) can be used for SIMO, diversity and beam steering modes. The MIMO WLAN system can also be designed to support various other modes of transmission and this falls within the scope of the invention. As an example, a beam forming node can be used for data transmission via a single autode using so much information. amplitude as phase to auto mode (rather than just phase information, which is all that is used by beam steering mode). As another example, a "non-directed" spatial multiplexing mode may be defined whereby the transmitter simply transmits multiple data streams from multiple transmitting antennas (without any spatial processing), and the receiver performs the spatial processing necessary to isolate and retrieve data streams sent from multiple transmitting antennas. As a further example, a "multi-user" spatial multiplexing mode may be defined whereby the access point transmits multiple data streams from multiple (spatially processed) transmitting antennas to multiple user terminals concurrently via downlink. As a further example, a spatial multiplexing mode may be defined whereby the transmitter performs spatial processing to attempt to orthogonalize the multiple streams of data sent through the multiple transmitting antennas (but may not be completely successful due to imperfect channel estimation). ), and the receiver performs the spatial processing necessary to isolate and retrieve data streams sent from multiple transmitting antennas. Thus, spatial processing for transmission of multiple data streams across multiple spatial channels can be performed (1) on both the transmitter and receiver, (2) the receiver only, or (3) the transmitter only. Different spatial multiplexing modes may be used depending, for example, on access point and user terminal capacities, available channel state information, system requirements, and so on.

In general, access points and user terminals can be designed with any number of transmitting and receiving antennas. For clarity, specific embodiments and designs will be described below whereby each access point is equipped with four transmitter / receiver antennas and each user terminal is equipped with four or less transmitter / receiver antennas.

2. OFDM

In one embodiment, the MIMO WLAN system employs OFDM to effectively partition the total system bandwidth into a number of orthogonal (NF) subbands. Such subbands are also referred to as tones, bins, or frequency channels. With Orthogonal Frequency Division Multiplexing (OFDM), each subband is associated with a respective subcarrier that can be modulated with data. For a MIMO system that uses OFDM, each spatial channel of each subband can be considered as an independent transmission channel where the complex gain associated with each subband is effectively constant across the subband bandwidth.

In one embodiment, the system bandwidth is partitioned into 64 orthogonal subbands (ie, Kt- = 64), which receive indices from -32 to +31. Of these 64 subbands, 48 subbands (for example, with indexes of ± {1, ..., 6, 8, 20, 22, ..., 26}) are used for data, 4 subbands ( for example, with indexes of ± {7, 21}) are used for pilot and possibly signaling, the DC subband (with index of 0) is not used and the remaining subbands are also not used and serve as sub- Guard bands. Such an OFDM subband structure is described in more detail in a document for the IEEE 802.11a standard entitled "Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: High-speed Physical Layer in the 5 GHz Bana ", of September 1999, which is publicly available and is incorporated herein by reference. Different subband numbers and various other OFDM subband structures can also be implemented for the MIMO WLAN system and this falls within the scope of the invention. As an example, all 53 subbands with indexes from -26 to 126 can be used for data transmission. As another example, a 128 subband structure, a 256 subband structure or a subband structure with another number of subbands may be used. For clarity, the MIMO WLAN system will be described below with the 64 subband structure described above.

For OFDM, the data to be transmitted through each subband is first modulated (ie mapped to symbols) using a specific modulation scheme selected for use for such subband. Zeros are provided for unused subbands. For each symbol period, the modulation symbols and zeros for all Np subbands are transformed to the time domain using a fast inverse Fourier transform (IFFT) to obtain a transformed symbol containing Np samples in the domain. of time. The duration of each transformed symbol is inversely related to the bandwidth of each subband. In a scheme specific to the MIMO WLAN system, the system bandwidth is 20 KHz. The bandwidth of each subband is 312.5 kHz and the duration of each transformed symbol is 3.2 ps. OFDM can provide certain advantages, such as the ability to combat frequency selective fading, which is characterized by different channel gains and different frequencies of the total system bandwidth. Frequency selective fading is known to cause intersymbol interference (ISI}, which is a phenomenon whereby each symbol in a received signal acts as a distortion to subsequent symbols in the received signal.) ISI distortion degrades performance by impairing the ability to detect correctly received symbols, frequency selective fading can be conveniently counteracted with OFDM by repeating a portion of (or appending a cyclic prefix a) each transformed symbol to form a corresponding OFDM symbol, which is then transmitted. of the cyclic prefix (ie the amount to repeat) for each OFDM symbol depends on the spread or diversity of wireless channel delays In particular, to effectively combat ISI, the cyclic prefix must be longer than the maximum delay spread expected from the wireless channel.

In one embodiment, cyclic prefixes of different lengths may be used for OFDM symbols, depending on the expected delay spread. For the specific MIMO WLAN system described above, a cyclic prefix of 400 ns (8 samples) or 800 ns (16 samples) can be selected for use for OFDM symbols. A "short" OFDM symbol uses the 40C ns cyclic prefix. and has a duration of 3.6 ps. A "long" OFDM symbol uses the 800 ns cyclic prefix and has a duration of 4.0 με. Short OFDM symbols may be used if the maximum expected delay spread is 400 ns or less, while long OFDM symbols may be used if the delay spread is greater than 400 ns. Different cyclic prefixes may be selected for use for different transport channels and the cyclic prefix may also be dynamically selected as described below. Higher system transmission capacity may be achieved by using the shorter cyclic prefix when possible, since more shorter duration OPDM symbols can be transmitted during a given fixed time interval. The MIMO WLAN system can also be designed not to use OFDM and this falls within the scope of the invention. 3, Layer Structure Figure 2 illustrates a layer structure 200 that can be used for the MIMO WLAN system. Layer structure 200 includes (1) upper layer applications and protocols that roughly correspond to Layer 3 and higher of the ISO / OSI reference model (upper layers), (2) protocols and services that correspond to Layer 2 (the (3) protocols and services that correspond to Layer 1 (the physical layer).

The upper layers include various applications and protocols, such as signaling services 212, data services 214, voice services 216, circuit data applications, and so forth. Signaling is typically provided in the form of messages and data is typically provided in the form of packets. Top-tier services and applications originate and terminate messages and packets according to the semantics and tone of the communication protocol between the access point and the user terminal. The upper layers use the services provided by Layer 2, Layer 2 supports the delivery of messages and packets generated by the upper layers. In the embodiment shown in Figure 2, Layer 2 includes a Link Access Control (LAC) 220 sublayer and a Medium Access Control (MAC) sublayer 230. The LAC sublayer implements a data link protocol that provides the correct transport and delivery of messages generated by the upper layers. The LAC sublayer uses the services provided by the MAC sublayer and Layer 1. The MAC sublayer is responsible for transporting messages and packets using the services provided by Layer 1. The MAC sublayer controls access to Layer 1 resources by applications and services on upper layers, the MAC sublayer may include a radio protocol (RLP) 232, which consists of a relay mechanism that can be used to provide greater reliability for packet data. Layer 2 provides layer 1 protocol data units to Layer 1. Layer 1 comprises physical layer 240 and supports the transmission and reception of radio signals between the access point and the user terminal. The physical layer performs the coding, interleaving, modulation, and spatial processing for the various transport channels used to send messages and packets generated by the upper layers. In the present embodiment, the physical layer includes a multiplexing sublayer 242 which multiplexes PDUs processed for multiple transport channels to the appropriate frame format. Layer 1 provides data in frame units. Figure 2 shows a specific embodiment of a layer structure that can be used for the MIMO WLAN system. Various other suitable layer structures may also be designed and used for the MIMO WLAN system and this falls within the scope of the invention. The functions performed by each layer will be described in more detail later, as appropriate. 4. Transport Channels Various services and applications may be supported by the MIMO WLAN system. In addition, other data required for proper system operation may be required to be sent by the access point or exchanged between the access point and user terminals. Several transport channels can be defined for the MIMO WLAN system to carry various types of data. Table 3 lists an exemplary set of transport channels and also provides a brief description of each transport channel.

As shown in Table 3, the channels d · ;. ' Downlink transports used by the access point include, BCH, FCCH and · FCH. The upl mk transport channels used by user terminals include RA.CH and RCH.

Each of such transport channels will be described in more detail below.

The transport channels listed in Table 3 represent a specific embodiment of a channel structure that can be used for the MIMO WLAN system. A smaller number of transport channels, or an additional and / or different number of transport channels can also be set for use by the MIMO WLAN system. For example, certain functions may be supported by transport channels specific to certain functions (eg pilot channels, paging, power control, and sync channel). Thus other channel structures with different sets of transport channels may be supported. defined and used for the MIMO WLAN system and this falls within the scope of the invention. 5. Frame Structures Several frame structures can be defined for transport channels. The specific frame structure to be used for the MIMO WLAN system depends on a number of factors, such as (1) whether the same or different frequency bands are used for downiink and uplink and (2) the scheme of multiplexing used to multiplex transport channels.

If only one frequency band is available, then downiink and uplink can be transmitted through different phases of a frame using time division duplexing (TDD) as described below. If two frequency bands are available, then downiink and uplink can be transmitted across different frequency bands using frequency division duplexing (FDD).

For both TDD and FDD, transport channels can be multiplexed together using Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Frequency Division Multiplexing (FDM), and so on. For TDM, each transport channel is assigned to a different part of a frame. For CDH, transport channels are transmitted concomitantly, but each transport channel is channeled by a different channel code, similar to that performed in a code division multiple access (CDMA) system. For FDM, each transport channel is assigned to a different part of the frequency band for the link. Table 4 lists the various frame structures that can be used to port transport sprockets. Each of such frame structures will be described in more detail below. For clarity, frame structures are described for the set of transport channels listed in Table 3.

Table 4 Figure 3A illustrates one embodiment of a TDD-TDM 300a frame structure that can be used if a single frequency band is used for downlirsk and uplink. Data transmission occurs on TDD frame units. Each TDD frame can be defined as covering a particular time duration. Frame duration can be selected based on a number of factors, such as, for example, (1) the bandwidth of the operating band, the expected size of the transport channel PDUs, and so on. Generally, a shorter frame duration may provide reduced delays. However, a longer frame duration may be more efficient since header and overhead may represent a smaller fraction of the frame. In a specific embodiment, each TDD frame has a duration of 2 ms.

Each TDD frame is partitioned into a dcwni ink phase and an uplink phase. The downlink phase is further partitioned into three segments for the three downlink transport channels - BCH, FCCH and FCH. The uplink phase is further partitioned into two segments for two uplink transport channels - RCÜ and RACH. The segment for each transport channel may be defined as having either a fixed duration or a variable duration that may change from frame to frame. In one embodiment, the BCH segment is defined as having a fixed duration and the FCCH, FCH, RCH, and RACH segments are defined as having variable durations. The segment for each transport channel may be used to carry one or more protocol data units (PDUs) for such a transport channel. In the specific embodiment shown in Figure 3A, a BCH PDU is transmitted in. a first segment 310, an FCH PDU is transmitted in. a second segment 320 and one or more FCH PDUs are transmitted on a third segment 330 of the downlink phase. In the uplink phase, one or more RCH PDUs are transmitted in a fourth segment 340 and one or more RACH PDUs are transmitted in a fifth segment 350 of the TDD frame.

Frame structure 300a .represents. a specific arrangement of the various transport channels within a TDD frame. Such an arrangement may provide certain benefits, such as reduced delays for downlink and uplink data transmission. The BCH is transmitted first in the TDD frame as it carries system parameters that can be used for other transport link PDUs within the same TDD frame. The t'CCH is then transmitted since it carries channel assignment information indicating which user terminals are designated to receive downlink data via the FCH and which user terminals are designated to transmit uplink data via the FCH. RCH within the current TDD frame. Other TDD-TDM frame structures that can be used for the MIMO MLM system can also be defined and this falls within the scope of the invention. Figure 3B illustrates one embodiment of an FDD-TDM 300b frame structure that can be used if downlink and uplink are transmitted using separate frequency bands. Downlink data is transmitted in a downlink frame 302a and uplink data is transmitted in an uplink frame 302b. Each downlink and uplink frame can be defined as covering a specific time duration (eg 2 ms). For simplicity, downlink and uplink frames can be set to have the same duration and can also be set to being aligned at frame boundaries. However, different frame durations and / or non-aligned (ie offset) frame boundaries can also be used for downlink and uplink.

As shown in Figure 3R, the downlink frame is partitioned into three segments for the three downlink transport channels. The uplink frame is partitioned into two segments for both uplink transport links. The segment for each transport channel may be defined as having a fixed or variable duration and may be used to carry one or more PDUs for such transport channel.

In the specific embodiment shown in Figure 3B, the downlink frame carries a BCH PDU, an FCCH PDU and one or more FCH PDUs in segments 310, 320 and 330, respectively. The uplink frame carries one or more RCH PDUs and one or more RACH PDUs in segments 340 and 350, respectively. Such a specific arrangement may provide the benefits described above (e.g. reduced delays for data transmission). Transport channels may have different PDU formats as described below. Other PDD-TDM frame structures may also be defined to be used for the MIMO WLAN system and this falls within the scope of the invention. Figure 3C illustrates one embodiment of an FDD-CDM / FDM 300c frame structure that can also be used if downlink and upiink are transmitted using separate frequency bands. Downlink data can be transmitted in a downlink frame 304a and upiink data can be transmitted in an upiink frame 304b. Downlink and upiink frames can be defined as having the same duration (for example, 2 ms) and being aligned at the frame boundaries.

As shown in Figure 3C, the three downlink transport channels are transmitted concurrently in the downlink frame and the two upiink transport channels are transmitted concurrently in the upiink frame. For CDM, the transport channels for each link are "piped" with different piping codes, which may be Walsh codes, orthogonal variable scatter factor codes (OV5F), quasi-orthogonal functions (QOF), and so on. . For FDM, the transport channels for each link receive different portions of the frequency band for the link. Different amounts of transmission power may also be set for different transport channels on each link.

Other frame structures may also be defined for downlink and upiink transport channels and this falls within the scope of the invention. In addition, you can use different frame structure types for downlink and uplink. As an example, a TDM-based frame structure can be used for downlink and a CDM-based frame structure can be used for uplink.

In the following description, it is assumed that the MIMO Ví LAN system uses a frequency band for downlink and uplink transmissions. For clarity, the TDD-TDM frame structure shown in Figure 3A is used for the MIMO WLAN system. For clarity, a specific implementation of the TDD-TDM frame structure will be described throughout the descriptive report. For such implementation, the duration of each TDD frame is fixed at 2 ms and the number of OFDM symbols per TDD frame is a function of cyclic prefix length used for OFDM symbols. The BCIf has a fixed duration of 80 ps and uses the 800 ns cyclic prefix for transmitted OFDM symbols. The remainder of the TDD frame contains 480 OFDM symbols if the 800 ns cyclic prefix is used and 533 OFDM symbols plus 1.2 ps of overtime if the 400 ns cyclic prefix is used. Excess time can be added to the guard interval at the end of the RACH segment. Other frame structures and other implementations may also be used and this falls within the scope of the invention. II. Transport Channels Transport channels are used to send various types of data and can be categorized into two groups: common transport channels and dedicated transport channels. Since dedicated and common transport channels are used for different purposes, different processing may be used for these two transport channel groups, as described in more detail below.

Common Transport Channels. Common transport channels include BtH, FCCH and RACH. Such transport channels are used for sending data to, or receiving data from, multiple user terminals. For better reliability, BCH and FCCH are transmitted by the access point using diversity mode. Through uplink, RACH is transmitted by user terminals using beam steering mode (if supported by user terminals). The BCH is operated at a fixed rate known so that user terminals can receive and process the BCH without any additional information. FCCH and RACH support multiple rates to enable greater efficiency. As used herein, each of the terms "rate" or "rate set" is associated with a particular code rate (or coding scheme) and a particular modulation scheme.

Dedicated Transport Channels. Dedicated transport channels include FCH and RCH. Such transport channels are typically used for sending specific data by user or specific user terminals. FCH and RCH can be dynamically allocated to user terminals as needed and available. FCH can also be used in a broadeast mode to send overhead, page, and broadeast messages to user terminals. In general, overhead, alert, and broadeast messages are transmitted before any user-specific data via FCH. Figure 4 illustrates an exemplary transmission over BCH, FCCH, FCH, RCH and RACH based on the TDD-TDM 300a frame structure. In such embodiment, a BCH PDU 410 and a FCCH 420 PDU are transmitted in the BCH 310 segment and in the FCCH 32 0 segment respectively. The FCH segment 330 may be used to send one or more FCH 430 PDUs, each of which may be destined for a specific user terminal or for multiple user terminals. Similarly, one or more RCH 440 PDUs may be sent by one or more user terminals in the RCH 340 segment. The beginning of each FCH / RCH PDü is indicated by an offset (F} / RCH from the end. Several RACH PDUs 450 may be sent on the RACH segment 350 by various user terminals to access the system and / or to send short messages as described below.

For clarity, transport channels will be described for the specific TDD-TDM frame structure shown in Figures 3A and 4. 1. Broadcast Channel (BCH) Dowη 1i n <RCH is used by the access point to transmit a pilot beacon, a MIMO pilot and system parameters for the user terminals. The signal pilot is used by the user terminals to capture the system's timing and frequency. The MIMO pilot is used by user terminals to estimate the MIMO channel formed by the access point antennas and their own antennas. The & M.1MO flag pilots will be described in more detail below. System parameters specify various attributes of downlink and upiink transmissions. As an example, since the durations of the FCCH, FCH, RACH, and RCH segments are variable, system parameters that specify the length of each of these segments for the current TDD frame are sent in the BCH. Figure SA illustrates one embodiment of PDU BCH 410. In such embodiment, PDU BCH 410 includes a preamble part 510 and a message part 516. The preamble part 510 also includes a signaling pilot part 512 and a pilot part MIMO 514. Part 512 carries a signaling pilot and has a fixed duration of TCp - 8 ps. Part 514 carries a MIMO pilot and has a fixed duration of IKp = 32 ps. Part 516 carries a BCH message and has a fixed duration of TBH - 40 ps. The PDü BCH duration is fixed and equal to Τ:; Ρ + TMt> + TBM = 80 ps. A preamble can be used to send one or more pilot types and / or other information. A signaling pilot comprises a specific set of modulation symbols that is transmitted from all transmitting antennas. A MIMO pilot comprises a specific set of modulation symbols that is transmitted from all transmitting antennas with different orthogonal codes, which then allows receivers to retrieve the pilot transmitted from each antenna. Different sets of modulation symbols can be used for signal and MIMO pilots. The generation of the flag and MIMO pilots will be described in more detail below. The BCH message carries system configuration information. Table 5 lists the various fields for an exemplary BCH message format.

Table 5 - BCH Message The frame counter value can be used to synchronize various rn access point processes and user terminals (eg pilot, scramble codes, coverage code, and so forth). The frame counter can be implemented by means of a 4-bit counter that cyclically restarts ("wraps around"). This counter is incremented at the beginning of each TDD frame and the counter value is included in the frame counter field. Network ID 1D identifies the identifier (ID> of the network to which the access point belongs. 0 AP ID field indicates 1D of the access point within the network ID. AP Tx Lvl and AP Rx Lvl fields indicate the maximum transmit power level and the desired receive power level at the access point, respectively The desired receive power level can be used by the user terminal to determine the uplink initial transmit power.

The FCCH length, FCH length, and RCH length fields indicate the lengths of the FCCH, FCH, and RCH segments, respectively, for the current TDD table. The lengths of such segments are given in units of OFDM symbols. The duration of OFDM symbols for the BCH is fixed at. 4.0 ps. The duration of OFDM symbols for all other transport channels (ie FCCH, FCH, RACH and RCH) is variable and depends on the selected cyclic prefix, which is specified by the cyclic prefix duration field. The FCCH rate field indicates the rate used for FCCH for the current TDD frame. The RACH length field indicates the length of the RACH segment, which is given in RACH partition units. The duration of each RACH partition is given by the RACH partition size field in OFDM symbol units. The RACH guard interval field indicates the amount of time between the last RACH partition and the beginning of the BCH segment for the next TDD frame. These various fields for RACH will be described in more detail below. The alert bit and broadcast bit will indicate whether or not alert messages and broadcast messages respectively are being sent via the FCH in the current TDD frame. These two bits can be set independently for each TDD frame. The RACH acknowledgment bit indicates whether acknowledgments for PDUs sent through RACH in previous TDD frames are or are not being sent through FCCH in the current TDD frame. The CRC field includes a CRC value for the entire BCH message. Such a CRC value can be used by user terminals to determine if the received BCH message is decoded correctly (ie, if it is good) or in error (ie, deleted). The tail bit field includes a group of zeros used to reset the convolutional encoder to a known state at the end of the BCH message.

As shown in Table 5, the BCH message includes a total of 120 bits. These 120 bits can be transmitted with 10 OFDM symbols using the processing described in detail below. Table 5 shows a specific format format for the BCH message. Other BCH message formats may also be defined and used, with fewer fields or additional and / or different fields and this falls within the scope of the invention. 2. Direct Control Channel (FCCH) - Downlink In one embodiment, the access point is capable of allocating resources for FCH and RCH on a per frame basis. FCCil is used by the access point to pass resource allocation to FCH and RCH (that is, channel assignments). Figure SB illustrates one embodiment of the FCCH 420 PDU. In such an embodiment, the PDU E 'CH includes only a part 520 for an FCCH message. The FCCH message has a variable duration that can change from frame to frame, depending on the amount of programming information being ported through the FCCH to that frame. The FCCH message length is an even number of OFDM symbols and is given by the FCCH Length field in the BCH message. The duration of messages sent using diversity mode (for example, BCH and FCCH messages) is given in. an even number of OFDM symbols, as the diversity mode transmits OFDM symbols in pairs as described below.

In one embodiment, the FCCH may be transmitted using four possible rates. The specific rate used for the FCCH PDU in each TDD frame is indicated by the FCCH PHY mode field in the BCH message. Each FCCH rate corresponds to a particular code rate and a particular modulation scheme and is also associated with a particular mode of transmission as shown in Table 26.

An FCCH message may include zero, one, or multiple information elements (). Each information element may be associated with a specific user terminal and may be used to provide information indicative of the allocation of FCH / RCB resources for such purpose. terminal, user. Table 6 lists the various fields for an exemplary FCCH message format.

Table 6 - FCCH Message

The N_IE field indicates the number of information elements included in the FCCH message sent in the current TDD frame. For each information element (TF1) included in the FCCH message, the type field of! B indicates the particular type of such IE. Several types of IE are defined for use in resource allocation for different types of transmissions, as described below. The MAC ID field identifies the specific user terminal for which the information element is intended. Each user terminal registers with the access point at the beginning of a communication session and receives a unique IP MAC sent by the access point. Such MAC ID is used to identify the user terminal during the session.

Control fields are used to pass channel assignment information to the user terminal and will be described in detail later. The fill bit field includes a sufficient number of fill bits such that the total length of the FCCH message is an even number of OFDM symbols. The FCCH CRC field includes a CRC value that can be used by user terminals to determine if the received FCCH message was decoded correctly or in error. The tail bit field includes zeros used to reset the convolutional encoder to a known state at the end of the FCCH message. Some of such fields will be described in more detail below. Several transmission modes are supported by the MIMO WLAN system for FCH and RCH as indicated in Table 1. In addition, a user terminal may be idle or active during a connection. Thus, several JE types are defined for use to allocate FCH / RCH resources for different transmission types. Table 7 lists an exemplary set of IE types.

Table ? * FCCH IE Types

For Liposals of 0, 1, and 4, resources are allocated to a specific FCH user terminal and the RCH is (in channel pairs). For IE 2 type, a minimum of resources are allocated to the user terminal in FCH and RCH to maintain the updated link estimate. An exemplary format for each type of IE will be described below. In general, rates and durations for FCH and RCH can be independently assigned to user terminals. A. IE 0 and 4 Types - Fe5xe Diversity / Steering Mode IE 0 and 4 types are used to allocate FCH / RCH resources for diversity and beam steering modes, respectively. For fixed low rate services (eg voice), the rate remains fixed for the duration of the call. For variable rate services, the rate can be independently selected for FCH and RCH. IE FCCH indicates the location of the RCH and FCH PDUs assigned to the user terminal. Table 8 lists the various fields of an IE 0 and 4 information type element. ___________Table 8 - TE FCCH Type 0 o /. ___________ The offset fields FCH and RCH indicate the time offset from the beginning of the current TDD frame to the beginning of the FCH and RCH PDUs, respectively, assigned by the information element. The rate fields FCH and RCH indicate the rates for FCH and RCH, respectively.

The preamble type fields FCH and RCH indicate the preamble size in the FCH PDUs ô RCH respectively. Table 9 lists the values for the FCH and RCH preamble type fields and the associated preamble sizes.

Table 9 - Preamble Type The time setting field RCH includes two bits used to set the uplink transmission time from the user terminal identified by the MAC ID field. Such timing adjustment is used to reduce interference in a FTDD-based frame structure such as that shown in Figure 3A} in which downlink and uplink transmissions are time division duplexed. Table 10 lists the values for the time setting field RCH and the associated actions.

Table 10 - RCH Timing Adjustment The RCH power control field: nril two bits used to adjust the uplink transmission transmit power from the identified user terminal. Such power control is used to reduce uplink interference. Table 11 lists the values for the RCH power control field and associated actions.

Table 11 - RCH Power Control Channel assignment for the identified user terminal can be provided in a number of ways. In one embodiment, the user terminal receives FCH / RCH resources for the current TDD frame only. In another embodiment, PCH / RCH resources are assigned to the terminal for each TDD frame until canceled. In another embodiment, the FCH / RCH resources are assigned to the user terminal for each nth TDD frame, which is referred to as "decimalized" programming of the TDD frames. The different assignment types can be indicated by an assignment type field in the FCCH information element. B. IE Type 1 - Spatial Multiplexing Mode IE Type 1 is used to allocate FCH / RCH resources to user terminals using spatial multiplexing mode. The rate for such user terminals is variable and can be independently selected for FCH and RCH. Table 12 lists the various fields of an exemplary IE type 1 information element.

Table 12 IE FCCH Type 1

For IE type 1, the rate for each space channel can be independently selected in PCH and RCH. The interpretation of the rates for spatial multi-mode is general in that it can specify the rate per space channel (eg , for up to four space channels for the modality presented in Table 12}. The rate is given by autode if the transmitter performs spatial processing for data transmission on the autodes. The rate is given per antenna if the transmitter simply transmits data from the transmitting antennas and the receiver performs spatial processing to isolate and retrieve the data (for non-directed spatial multiplexing mode). The information element includes the rates for all. space channels enabled and zeros for those not enabled. User terminals with fewer than four transmitting antennas set the FCH / RCH spatial charting rate fields to zero. Since the access point is equipped with four transmitter / receiver antennas, user terminals with more than four transmitter antennas can use them to transmit up to four independent data streams. Ç . IE Type 2 - How the Type 1 Type 2 is used to provide control information for user terminals operating in an idle state (described below). In one embodiment, when a user terminal is idle, the driving vectors used by the access point and user terminal for spatial processing are continuously updated so that data transmission can begin rapidly if and when resumed. Table 13 lists the various fields of a type 2 IE information element.

Table '.3 - IE FCCE Type 2

D. IE Type J Fast Confirmation RACH IE Type 3 is used to provide quick confirmation for user terminals trying to access the system through RACH. To gain system access or to send a short message to the access point, a user terminal can transmit an EDO RACH via uplink. After the user terminal sends the RACH Password, it monitors the BCH to determine if the RACH acknowledgment bit is set. This bit is set by the access point if any user terminal has successfully accessed the system and an acknowledgment is being sent to at least one user terminal on the FCCH. If this bit is set, then the user terminal processes the FCCH for confirmation sent via the FCCH. Type 3 IE information elements are sent if the access point wishes to confirm that it has correctly decoded RACH PDUs from user terminals to be allocated resources. Table 14 lists the various fields of an exemplary type 3 IE information element.

Table 14 - IE FCCH Type 3

One or multiple types of acknowledgments can be set and sent via FCCH. An example can be a quick confirmation and an assignment based confirmation. A quick acknowledgment can be used to simply confirm that the RACH PDU has been received by the access point but that no FCH / KCH resources have been assigned to the user terminal. An assignment-based commit includes assignments for the FCH and / or RCH for the current TDD frame. FCCH may be implemented in other ways and may also be transmitted in various ways. In one embodiment, the FCCH is transmitted at a single rate that is signaled in the BCH message. Such rate can be selected, for example, based on the lowest signal to noise ratios plus interference (SNRs) of all user terminals to which the FCCH is being sent in the current TDD frame. Different rates may be used for different TDD frames depending on the channel conditions of the receiving user terminals in each TDD frame.

In another embodiment, the FCCH is implemented with multiple (e.g., four) FCCH subchannels. Each FCCH subchannel is transmitted at a different rate and is associated with a different required 5NR in order to recover the subchannel. FCCH subchannels are transmitted in order from lowest rate to highest rate. Each FCCH subchannel may or may not be transmitted in a given TDD frame. The first FCCH subchannel (with the lowest rate) is transmitted first and can be received by all user terminals. Such a FCCH subchannel may indicate whether or not each of the remaining FCCH subchannels will be transmitted in the current TDD frame. Each user terminal can process the transmitted FCCH subchannels to obtain the FCCH information element. Each user terminal can terminate FCCH processing if any of these occur; {li failed to decode the current FCCH subchannel, {2} received its FCCH information element in the current FCCH subchannel, or (3) all transmitted FCCH subchannels were processed. A user terminal can terminate FCCH processing as soon as it encounters FCCH decoding failure because FCCH subchannels are transmitted at upward rates and the user terminal will probably not be able to decode subsequent FCCH subchannels transmitted at higher rates. 3. Random Access Channel (RACB) - Upllnk RACH is used by user terminals to gain access to the system and to send short messages to the access point. The operation of RACH is based on a partitioned ALOHA random access protocol, which will be described later. Figure 5C illustrates one embodiment of RACH PDU 450. In such embodiment, the RACH PDU includes a preamble portion 552 and a message portion 554. Preamble part 552 can be used to send a directed reference (i.e. a directed pilot) if the user terminal is equipped with multiple antennas. The directed reference consists of a pilot made up of a specific set of modulation symbols that is subjected to spatial processing prior to uplink transmission. Spatial processing allows the pilot to be transmitted via a specific MIMO channel autode. Processing for the directed reference will be described in more detail below. Preamble part 552 has a fixed length of at least 2 OFDM symbols. Message portion 554 carries an RACH message and has a variable duration. The duration of the RACH PDU is therefore variable.

In one embodiment, four different rates are supported for RACH. The specific rate used for each RACH message is indicated by a 2-bit RACH Data Rate Indicator (DR1), which is embedded in the preamble portion of the RACH PDU, as shown in Figure 5C. In one embodiment, four different message sizes are also supported for RACH. The size of each RACH message is indicated by a message length field included in the RACH message. Each RACH rate supports 1, 2, 3, or all 4 message sizes. Table 15 lists the four RACH rates, their associated coding and modulation parameters, and the message sizes supported by such RACH rates.

Table 15 RACH nensdqen lists short messages and access requests from the user terminal, Table 16 lists the various fields of an exemplary RACH message format and the size of each field for each of four different message sizes. .

Table 16 The message length field indicates the size of the RACH message. The MAC PDU Type field indicates the RACH message type. MAC field 1D contains the MAC ID that uniquely identifies the user terminal that sends the RACH message. During initial system access, a unique MAC ID was not assigned to the user terminal. In such a case, a MAC registration ID · (for example, a specific value reserved for registration purposes) may be included in the MAC ID field. The partition ID field indicates the initial RACH partition to which the RACH PDU was sent (RACH timing and transmission will be described later). The payload field includes the RACH message information bits. The CRC field contains a CRC value for the RACH message, and the tail bit field is used to reset the convolutional encoder for RACH. The operation of RACH in conjunction with BCH and FCCH for system access will be described in more detail below. RACH can also be implemented with a "fast" RACH {F-RACH) and a "slow" RACH (S-RACH) .F-RACH and S-RACH can be designed to efficiently support user terminals in different states. As an example, F-RACH can be used by user terminals that have registered with the system, (2} can compensate for their round-trip delays (RTDs) by properly advancing their transmission timing and { 3) achieve the required SNR for F-RACH operation 0 S-RACH may be used by user terminals that cannot use F-RACH for any reasons.

Different designs can be used for F-RACH and Ξ-RACH to facilitate quick system access whenever possible and to minimize the amount of system resources required to implement random access. As an example, F-RACH may use a shorter PDU, employ a weaker coding scheme, require F-RACH PDUs to arrive approximately time-aligned at the access point, and use a partitioned ALOHA random access scheme. S-RACH can use a longer PDU, employ a stronger coding scheme, allow RftCH S-PDUs to arrive unaligned at the access point, and use an unpartitioned ALOHA random access scheme.

For simplicity, the following description assumes that a single RACH is used for the MIMO WLAN system. 4. Direct Channel (FCH) - Downiink 0 FCH is used by the access point for user specific data transmission to specific user terminals and alert / broadeast messages for multiple user terminals. The FCH can also be used to transmit a pilot to user terminals. 0 FCH can be allocated with. frame by frame basis. Various types of FCH PDUs are provided to accommodate different uses of the FCH. Table 1? lists an exemplary set of FCH PDU types.

Table 17 - FCH PDU Types

The FCH Type 0 PDU is used to send alert / broadeast messages and user messages / packets through the FCH and includes only the message / packet. Data for a specific user terminal may be sent in the form of a message or a packet and these two terms are used interchangeably herein. The Type 1 FCH PDU is used to send user packets and includes a preamble. The Type 2 FCH PDU only includes the preamble and no message / packet and is associated with idle FCH traffic.

Figure 5D illustrates one embodiment of an FCH PDU.

430a for type 0 FCH PDU. In such an embodiment, FCH PDU 430a includes only a message portion 534a for an alert / broadcast message or a user packet. The message / packet may have variable length, which is given by the FCH message length field in the FCH PDU. The message length is given by an integer number of PHY frames (described below). The rate and mode of transmission for the alert / broadcast message are specified and described below. The rate and mode of transmission for the user packet are specified in the associated FCCH information element. Figure SE illustrates one embodiment of an FCH PDU 430b for the type 1 FCH PDU. In such an embodiment, the FCH PDU 430b includes a preamble portion 532b and a message / packet portion 534b. Preamble part 532b is used to send a MIMO pilot or a directed reference and has a variable length, which is given by the preamble field FCH in the associated FCCH information element. Part 534b is used to send an FCH packet and also has a variable length (in an integer number of PHY frames), which is given by the FCH message length field in the FCH PDU. The FCH packet is sent using the rate and mode of transmission specified by the associated FCCH information element. Figure 5F illustrates one embodiment of an FCH PDU 430c for the type 2 FCH PDU. In such embodiment, the FCH PDU 430c includes only a preamble part 532c and no message part. The length of the preamble part is indicated by FCCH ΙΕ. The Type 2 FCH PDU can be used to allow the user terminal to update its channel estimate while in idle state. Various types of FCH messages are provided to accommodate different uses of FCH. Table 18 lists an exemplary set of FCH message types.

Table 18 - FCH Message Types

An alert message {page} can be used to alert multiple user terminals and is sent using the FCH type 0 PDU. If the dc alert bit in the BCH message is set, then one or more FCH PDUs with alert messages. (or "Alert PDUs") are sent first through the FCH, Multiple alert PDUs can be sent in the same frame. Alert PDUs are transmitted using diversity mode and the lowest 0.25 bps / Hz rate to increase correct reception by user terminals.

A broadcast message can be used to send information to multiple user terminals and is sent using the FCH type 0 PDU. If the broadcast bit in the BCH message is set, then one or more FCH PDUs with broadcast messages ( or "Broadcast PDUs"} are sent via FCH immediately after any alert PDUs sent via FCH Broadcast PDUs are also transmitted using diversity mode and the lowest rate of 0.25 bps / Hz. to increase the likelihood of correct reception.

A user packet can be used to send user specific data and can be sent using the Type 1 or 2 FCH PDU. Type 1 and 2 user PDUs are sent through the FCH after any alert and broadcast PDUs sent. through the FCH. Each user PDU can be transmitted using diversity mode, beam steering, or spatial multiplexing mode. The FCCH information element specifies the rate and mode of transmission used for each user PDU sent through the FCH.

A message or packet sent through the FCH comprises an integer number of PHY frames. In one embodiment, and as described below, each PHY frame may include a CRC value that allows individual PHY frames on an FCH PDU to be checked and retransmitted if necessary. For asynchronous services, RLP can be employed for segmenting, retransmitting, and reassembling PHY frames within a given FCH PDU. In another embodiment, a CRC value is provided for each message or packet instead of each PHY frame. Figure 6 illustrates one embodiment of the structure for an FCH 534 packet. The FCH packet comprises an integer number of PHY 610 frames. Each PHY frame includes a payload field 622, a CRC field 624 and a bit field of 625. tail 626. The first PHY frame for the FCH packet also includes a header field 620 which indicates the type and duration of the message. The last PHY frame in the FCH packet also includes a fill bit field 628, which contains zero fill bits at the end of the payload to fill the last PHY frame. In one embodiment, each PHY frame comprises 6 OFDM symbols. The number of bits included in each PHY frame comprises 6 OFDM symbols. The number of bits included in each PHY frame depends on the rate used for such a PHY frame. Table 19 lists the various fields for an exemplary FCH PDU format for FCH PDUs of types 0 and 1.

Table 19 - PDÜ FCH Format

The FCH message type and FCH message length fields are sent in the header of the first PHY frame of the FCH PDU. The payload, CRC, and tail bits fields are included in each PHY frame, K the payload portion of each FCH PDU carries the information bits for the alert / broadcast message or user specific packet. Fill bits are used to fill the last PHY frame of the PDU FCH if necessary.

A PHY frame may also be defined comprising some other number of OFDM symbols (e.g., one, two, four, eight and so on). The PHY frame can be defined with an even number of OFDM symbols since OFDM symbols are transmitted in pairs for diversity mode which can be used for FCH and RCH. PHY frame size can be selected based on expected traffic such that inefficiency is minimized. In particular, if the frame size is too large, then inefficiency results from using a large PHY frame to send a small amount of data. Alternatively, if the frame size is too small, then over.head represents a larger fraction of the frame. 5. Reverse Channel (RCH) - Uplink. RCH is used by user terminals to transmit uplink and pilot data to the access point. The RCH can be allocated on a frame by frame basis. One or more user terminals may be assigned to transmit over RCH on any given TDD frame. A number of RCH PDU types are provided to accommodate different modes of operation in the RCH. Table 20 lists an exemplary set of RCH PDU types.

Table 20 - Types of RCH PDUs The type 0 RCH PDU is used to send a message or packet through the RCH and does not include a preamble. The Type 1 PDü RCH is used to send a message or packet and includes a preamble. The Type 2 RCH PDU includes a preamble and a short message and is associated with idle RCH traffic. Figure 5D illustrates one embodiment of an RCH PDU for the type 0 RCH PDU. In such an embodiment, the RCH PDU includes only a message portion 534a for a variable length RCH packet, which is given in an integer number of PfiY frames. by the RCH message length field in the RCH PDU. The rate and mode of transmission for the RCH packet are specified in the associated FCCH information element. Figure 5E illustrates one embodiment of an RCH PDU for the type 1 RCH PDU. In such an embodiment, the RCH PDU includes a preamble portion 532b and a packet portion 534b. Preamble part 532b is used to send a reference (for example, a MIMO pilot or a directed reference) and has a variable length, which is given by the preamble field RCH in the associated FCCH information element, The 534b is used to send an RCH packet and also has a variable length, which is given by the RCH message length field in the RCH PDU. The RCH packet is sent using the rate and mode of transmission specified in the associated FCCH information element. Figure 5G illustrates one embodiment of an RCH PDU 350d for the type 2 RCH PDU. In such an embodiment, the RCH PDU includes a preamble portion 532d and a message portion 536d. The preamble part S32d is used to send a reference and has a length of 1, 4, or B OFDM symbols. Part 536d is used to send a short RCH message and has a fixed length of an OFDM symbol. The short RCH message is sent using a specific rate and mode of transmission (for example, rate 1/2 or rate 1/4 and BPSK 'modulation).

A packet sent over the RCH (for type 0 and 1 PDUs) comprises an integer number of PHY frames. The structure for an RCH packet (for Del type PDUs) is shown in Figure 6 and is the same as for the FCH packet. The RCH packet comprises an integer number of PHY 610 frames. Each PHY frame includes the payload field 622, an optional CRC field 62 4, and the tail bit field 62 6. The first PHY frame in the RCH packet includes the payload field. header 620 and the last PHY frame in the packet also include the fill bit field 628. Table 21 lists the various fields for an exemplary RCH PDU format for FCH PDUs of types 0 and 1.

Table 21: RCH PDU Format (PDU Types 0 and 1} The message type, RCH, RCH message length, and FCH rate indicator fields are sent in the header of the first PHY frame of the RCH PDU, the 0 indicator field. FCH rate is used to pass FCH rate information (for example, the maximum rates supported by each of the space channels) to the access point.Table 22 lists the various fields for an example RCH PDU format to the RCH PDU Type 2, Table 22 - RCH to PDU Message Type 2 RCH The RCH request field is used by the user terminal to request additional capacity on the uplink Such short RCH message does not include a CRC and is transmitted in a single OFDM symbol 6. Dedicated Channel Activity Uncle FCH and RCH data transmission may occur independently Depending on the transmission modes selected for use for the FCH and RCH, one or multiple spatial channels (for beam and diversity steering modes) ade) can be active and used for data transmission for each dedicated transport channel. Each space channel may be associated with a specific rate.

When only FCH or only RCH has all four rates set to zero, the user terminal is idle on such a link. The idle terminal still transmits an idle PDU through the RCH. When both FCH and RCH have all four rates set to zero, both the access point and the user terminal are off (oif) and not transmitting. User terminals with fewer than four transmitting antennas set unused rate fields to zero. User terminals with more than four transmitting antennas do not use. more than four space channels for data transmission. Table 23 shows the transmission state and channel activity when the rates on all four FCH or RCH space channels (or both) are set to zero.

There may also be a situation where both RCH and FCH are idle (that is, they are not transmitting data but are still transmitting the preamble. This is referred to as the idle state.) The control fields used to support idle state user terminal are provided in a type 2 IE FCCH information element, which has been presented in Table 13. 7, Alternative Products For clarity, specific PDU types, PDU structures, message formats and so on. described below for an exemplary project.Fewer, additional and / or different types, structures and formats may also be defined for use and this falls within the scope of the invention.

In the above description, the same OFDM subframe structure is used for all transport channels. Better efficiency can be achieved by using different OFDM subband structures for different transport channels. As an example, a 64 subband structure may be used for some transport channels, a 256 subband structure may be used for some other transport channels, and so on. In addition, multiple OFDM subband structures may be used for a given transport channel.

For a given W system bandwidth, the duration of a GFDM symbol depends on the total number of subbands. If the total number of subbands is N, then the duration of each transformed symbol (without a cyclic prefix) is N / W ps (if W is given in KHz). A cyclic prefix is added to each transformed symbol to form a corresponding GFDM symbol. The length of the cyclic prefix is determined by the expected delay spread of the system. The cyclic prefix · represents overhead, which is required for each OFDM symbol in order to combat a frequency selective channel. Such overhead represents a higher percentage of the OFDM symbol if the symbol is short and a lower percentage if the symbol is long.

Since different transport channels may be associated with different traffic data types, a suitable OFDM subband structure may be selected for use for each transport channel to match the expected traffic data type. If it is expected to transmit a large amount of data on. a given transport channel, so a larger subband structure can be defined for use for the transport channel. In such a case, the cyclic prefix would represent a lower percentage of the OFDM symbol and higher efficiency could be obtained. In contrast, if a small amount of data is expected to be transmitted on a given transport channel, then a smaller subband structure can be defined for use for the transport channel. In such a case, while the cyclic prefix represents a higher percentage of the OFDM symbol, greater efficiency can still be achieved by reducing overcapacity by using a smaller size OFDM symbol. The OFDM symbol can therefore be seen as a "box car" that is used for sending data, the appropriate sized "chest car" can be selected for each transport channel depending on the amount of data. expected to send.

As an example, for the above described embodiment, the data in FCH and RCH are sent in PHY frame, each of which comprises 6 OFDM symbols. In such a case, another OFDM structure may be defined for use for the FCH and RCH. As an example, a 256 subband structure can be defined for FCH and RCH. A "large" OFDM symbol for the 256 subband structure would be approximately four times the length of a "small" OFDM symbol for the 64 subband structure but would be able to carry data four times larger. However, only one cyclic prefix is required for one large OFDM symbol, while four cyclic prefixes are required for the four equivalent small OFDM symbols. Thus, the amount of overhead for cyclic prefixes can be reduced by 75% by using the larger structure of 256 subbands.

Such a concept can be extended so that different OFDM subband structures can be used for the same transport channel. As an example, RCH supports different types of PDU, each of which may be associated with a certain size. In such a case, a larger subband structure can be used for a larger type of RCH PDU and a smaller subband structure can be used for a smaller type of RCH PDU. A combination of different subband structures can also be used for a given PDU. As an example, if a long OFDM symbol is equivalent to four short OFDM symbols, then a PDU can be sent using Ngreride large OFDM symbols and Npequeft0 small OFDM symbols, where Ngraild (>> 0 and 3 - Npequer.o> 0 .

Different OFDM subband structures are associated with OFDM symbols of different lengths. Thus, if different OFDM subband structures are used for different transport channels (and / or the same transport channel], then the FCH and RCH offsets for the FCH and PDtJs RCH should be specified with resolution and time. which is less than one OFDM symbol period In particular, the time increment for the FCH and RCH PDUs may be given in integers of the cyclic prefix length, rather than the OFDM symbol period. Transmission Modes The transport channels described above are used to send various types of data for various services and functions.Each transport channel can be designed to support one or more rates and one or more transmission modes. transmission modes are supported for transport channels Each transmission mode is associated with specific spatial processing at the transmitter and receiver as described further below. See Table 24 lists the transmission modes supported by each of the transport channels.

For diversity mode, each data symbol is transmitted redundantly across multiple transmitting antennas, multiple subbands, multiple symbol periods, or a combination thereof to achieve spatial, frequency and / or time diversity. For beam steering mode, a single space channel is used for data transmission (typically the best space channel) and each data symbol is transmitted through the single space channel using the total transmit power available to the transmitting antennas. For spatial multiplexing mode, multiple spatial channels are used for data transmission and each data symbol is transmitted through a spatial channel, where a spatial channel may correspond to an autode, a transmitting antenna and so on. Beam steering mode can be considered as a special case of spatial multiplexing mode whereby only one space channel is used for data transmission. Diversity mode can be used for common transport channels (BCH and FCCH) to downlink from access point to user terminals. Diversity mode can also be used for dedicated transport channels (FCH and RCH). Use of diversity mode in FCH and RCH can be negotiated at call establishment. Diversity mode transmits data in a "spatial mode" using a pair of antennas for each subband. The beam steering mode can be employed in RACH by user terminals with multiple transmitting antennas. A user terminal can estimate the MIMO channel based on the MIMO pilot sent through the BCH. Such channel estimation can then be used to beam RACH for system accesses. The beam steering mode may also be used for dedicated transport channels (FCH and RCH} .The beam steering mode may be able to achieve a higher signal-to-noise ratio (SNR) at the receiver than the receiver. diversity mode by exploiting the gain of antenna array in the transmitter In addition, the preamble portion of the PDU can be reduced since the directed reference includes only symbols for a single "directed" antenna. also be used for RACH Spatial multiplexing mode can be used for FCH and RCH for higher transmission capacity when supported by channel conditions Spatial multiplexing and beam steering modes are reference driven and require closed-loop control for proper operation, so a user terminal receives resources in the FCH and RCH to support spatial multiplexing mode. Other space channels can be supported on the FCH and RCH (limited by the number of antennas on the access point). 2 Encoding and Modulation Several different rates are supported for transport channels. Each rate is associated with a particular code rate and a particular modulation scheme, which collectively result in a particular spectral efficiency (or data rate). Table 25 lists the various rates supported by the system.

Each common transport channel supports one or more rates and one mode of transmission (or possibly more, as may be the case for RACH). BC.H is transmitted at a fixed rate using diversity mode, ü FCCH can be transmitted and one of four possible rates as indicated by the FCCH PHY mode field in the BCH message using diversity mode. In one embodiment, RACH may be transmitted at one of four possible rates, as indicated by the RACH DRI embedded in the RACH PDU Preamble, and each RACH message has one of four possible sizes. In another embodiment, RACH is transmitted at a single rate. Table 26 lists the encoding, modulation, and transmission parameters and message sizes supported by each community transport channel.

Table 26 - Parameters for Common Transport Channels [ί The FCCH message has variable length and is given in an even number of OFDM symbols. FCH and RCH support all rates listed in Table 25. Table 2? lists the encoding, modulation and transmission parameters and the supported FCH and RCH message sizes.

Table 27 - Parameters for FCH and RCH

Grade A; each 1/2 rate code bit is repeated in two subbands to obtain an effective 1/4 code rate. Parity bits represent redundancy bits introduced by coding and are used for error correction by the receiver. The PHY frame size in Table 27 indicates the number of code bits, modulation symbols, and GFDM symbols for each PHY frame. If 48 data subbands are used for data transmission, then each OFDM symbol includes 48 modulation symbols. For diversity and beam steering modes, a symbol stream is transmitted and the PHY frame size corresponds to the single rate employed for such symbol stream. For spatial multiplexing mode, multiple symbol streams can be sent across multiple spatial channels and the total PHY frame size is determined by the sum of the PHY frame sizes for the individual spatial channels. The · PHY frame size for each space channel is determined by the rate employed for such a space channel.

As an example, assuming that the MIMO channel is capable of supporting four space channels operating at 0.5, 1.5, 4.5, and 5.5 bps / Hz spectral efficiencies, the four rates selected for the four space channels would then be as shown in Table 28.

Table 28 - Example of Spatial Multiplexing Transmission The total size of the PHY frame is therefore either 144 +432 + 1296 + 1584 = 3456 bits of information or 288 + 576 + 1728 + 2304 = 4896 bits of code. Although each of the four space channels supports a different number of payload bits, the total PHY frame can be transmitted in 6 OFDM symbols (for example, 24 ps, assuming 4 ps per OFDM symbol). V. Physical Layer Processing Figure 7 shows a block diagram of one embodiment of an HOx access point and two 120x and 12Oy user terminals within the MIMO · WLAN system.

Through the downlink at the HQx access point, a transmit (TX) data processor 710 receives traffic data (i.e. information bits) from a data source or source 708 and signaling and other information from a 730 controller and possibly a 734 programmer. These various types of data can be sent over different transport channels. The TX 710 data processor "frames" the data (if necessary), shuffles the framed / non-framed data, encodes the scrambled data, interleaves (i.e. reorders) the encoded data, and maps the interleaved data to modulation symbols. . For simplicity, a "data symbol" refers to a modulation symbol for traffic data and a "pilot symbol" refers to a pilot modulation symbol. Shuffling randomizes the data bits. Encoding increases the reliability of data transmission. Interleaving provides time, frequency, and / or spatial diversity for the · code bits. Shuffling, coding, and modulation can be performed based on control signals provided by the 730 controller and will be described in more detail below. The TX 710 data processor provides a flow of modulation symbols for each space channel used for data transmission.

A TX 720 spatial processor receives one or more modulation symbol streams from the TX 710 data processor and performs spatial processing on the modulation symbols to provide four transmit symbol streams, one stream for each transmitting antenna. Spatial processing will be described in more detail below.

Each modulator (MQD) 722 receives and processes a respective transmission symbol stream to provide a corresponding OFDM symbol stream. Each OFDM symbol stream is further processed to provide a corresponding modulated downlink signal. The four modulated downlink signals from modulators 722a to 722d are then transmitted from four antennas 724a to 724.d, respectively.

In each user terminal 120 one or multiple antennas 752 receive the modulated downlink signals and each receiving antenna provides a signal received for a respective demodulator 754. Each demodulator 754 performs processing complementary to that performed on modulator 722 and provides symbols. received. A receiving spatial processor (RX> 780 below) spatially processes symbols received from all demoduers 754 to provide retrieved symbols, which are estimates of the modulation symbols sent by the access point.

An RX 770 data processor receives and demultiplexes the retrieved symbols to their respective transport channels. Symbols retrieved for each transport channel may be demapped, deinterleaved, decoded and scrambled to provide decoded data for such a transport channel. The decoded data for each transport channel may include retrieved packet messages, messages, signaling, and so forth, which are provided for a data warehouse 772 for storage and / or for a controller 760 for further processing. Processing by the access point 110 and terminal 120 for the downlink will be described in more detail below. Processing for upiink may be the same or different than processing for downlink.

For the downlink, on each active user terminal 120, the RX 760 space processor also estimates the downlink for channel state information (CSI). CSIs may include channel response estimates, received SNRs, and so on. The RX 770 data processor may also provide the status of each packet / frame received via the downlink. A 780 controller receives channel state and packet / frame status information and determines the feedback information to be sent back to the access point. Feedback information is processed by a TX 790 data processor and a TX 792 space processor (if present), conditioned by one or more modulators 754 and transmitted through one or more antennas 752 back to the access point.

At access point 110, transmitted upiink signals are received by antennas 724, demodulated by demodulators 722 and processed by a RX 740 space processor and an RX 742 data processor in a manner complementary to that performed at the user terminal. The feedback information retrieved is as follows; provided for controller 730 and a programmer 734. Programmer 734 uses feedback information to perform various functions, such as (1) selecting a set of user terminals for downlink and upiink data transmission, (2) selecting transmission rates and transmission mode for each user terminal selected and (3) assign the available FCH / RCH resources to the selected terminals. Programmer 734 and / or controller 730 also use information (e.g., steering vectors) obtained from upiink transmission for downünk transmission processing, as described in more detail below. Several transmission modes are supported for downlink and upiink data transmission. The processing for each of such transmission modes will be described in more detail below. 1, Diversity Mode - Transmission Processing Figure 8A shows a block diagram of one embodiment of a transmitter unit 800 capable of performing transmission processing for diversity mode. The transmitter unit 800 may be used for the transmitting part of the access point and user terminal.

Within a TX 71 Da data processor, a framing unit 808 frames the data for each packet to be transmitted via the FCH or RCH. Framing need not be done for other transport channels. Framing may be performed as illustrated in Figure 6 to generate one or more PHY frames for each user packet. An 810 scrambler a. then scrambles the framed / non-framed data for each transport channel to randomize the data.

An encoder 812 receives and encodes scrambled data according to a coding scheme selected to provide code bits. A puncture unit 814 then repeats or punctures (i.e. erases.) Some of the code bits to obtain the desired code rate. In one embodiment, encoder 812 is a 1/2 rate convolutional binary encoder, restriction length 7. A code rate of 1/4 may be obtained by repeating each code bit once. Code rates greater than 1/2 can be obtained by erasing some of the code bits from encoder 812, a specific design for framing unit 808, scrambler 810, encoder 812, and repeat / punch unit 814 will be described. further up.

An interleaver 318 then interleaves (i.e. reorders) the code bits from unit 814 based on a selected interleaving scheme. In one embodiment, each group of 48 consecutive code bits to be transmitted over a given spatial channel is spread over the 48 data carrier subbands {or simply data subbands} to provide frequency diversity. The interleaving will be described in more detail later.

A following symbol mapping unit 820 maps the interleaved data according to a particular modulation scheme to provide modulation symbols. As shown in Table 26, RPSK, 4 QAM, or 16 QAM can be used for diversity mode, depending on the rate selected. In diversity mode, the same modulation scheme is used for all data subbands. Symbol mapping can be performed by (1 j grouping B-bit sets to form B-bit values, where B> 1 and (2} map each B-bit value to a point in a signal constellation corresponding to the selected modulation scheme Each mapped signal point is a complex value and corresponds to a modulation symbol- Symbol mapping unit 820 provides a modulation symbol flow to a TX 720a diversity processor.

Once a mode, the diversity mode uses space-time transmission diversity (STTD) for dual transmission diversity on a per-band basis. STTD supports simultaneous transmission of independent symbol streams through two transmitting antennas, maintaining orthogonality in the receiver.

The STTD scheme operates as follows. Let's assume that two modulation symbols, denoted by themselves and Sj, must be transmitted over a given subband. The transmitter generates two vectors, where it denotes the complex conjugate and "r" denotes the transposed. Each vector includes two elements that must be transmitted from two transmitting antennas in a symbol period (that is, the vector ij is transmitted). from two antennas in the first symbol period and the vector * 2 is transmitted from two antennas in the next symbol period).

If the receiver is equipped with a single receiver antenna, then the received symbols may be expressed by: e> Eq (l) Where η and r2 are two symbols received in two consecutive symbol periods at the receiver; hi and h2 are the path gains from the two transmitting antennas to the receiving antenna for the subband under consideration, where the path gains are assumed to be constant in the subband and static over the 2-symbol period; and R1 and 12 are the noise associated with the two received symbols q and R2 respectively. The receiver may then derive estimates of the two transmitted symbols, and $ 2, as follows: and Eq (2) Alternatively, the transmitter may generate two vectors and transmit the two vectors sequentially in two symbol periods from two transmitting antennas. The received symbols may then be expressed by:, and the receiver may then derive estimates of the two transmitted symbols as follows: and The above description may be extended to a MIMO OFDM system with two or more transmitting antennas, Nr receiving antennas and multiple antennas. subbands. Two transmitting antennas are used for any given subband. Suppose that two modulation symbols, denoted by $ i (k) & S2 (k), must be transmitted through a given subband k. The transmitter generates two vectors or equivalently two symbol sets Each symbol set includes two elements that are to be transmitted sequentially in two symbol periods from a respective transmit antenna via the subband k {i.e. the symbol set { *, (£)} is transmitted through subband k from antenna i in two symbol periods and the {.vt (k)} symbol set is transmitted through subband ka from antenna / in the same period. of two symbols).

The symbol vectors received at the receiving antennas in the two symbol periods can be expressed by: I τ where rj (k) and £ 2 (frj are two symbol vectors received in two consecutive symbol periods through the subband k at the receiver, with each vector including Ng symbols received for the Nu receiver antennas; hii.fr) and h-, (k) are the path gain vectors of the two transmitting antennas iej to Nu receiver antennas for the subband fr , with each vector including channel gains from the associated transmitting antenna to each of the receiving Ng antennas, where the path gains are assumed to be constant within the subband and static over the 2-symbol period; and in (fr) and n2 (fr) are noise vectors associated with the two received vectors ri (k) and rj (k), respectively. The receiver may then derive estimates of the two transmitted symbols, jq (fr) and .y2 {fr}, as follows; Alternatively, the transmitter may generate two symbol sets and transmit these two symbol sets from two transmitting antennas i and j. The received symbol vectors can then be expressed by:, and The receiver can then derive estimates of the two transmitted symbols as follows: e The STTD scheme was described by SM Alamouti in a paper entitled "Simplex Transmit Divergence Technique for Wireless Communications". ", IEEE Journal on Solected Areas in Communications, Vol. 16, N-8, October 1998, pages 1451 to 1458. The STTD scheme is also described in US Patent Application Serial No. 09 / 737,602, entitled" METHOD AND SYSTEM FOR INCREASED BANDW1DTH ETHICIENCY IN M.ULTIPLE INPUT - MÜLT1PLE OUTPIJT CHANNELS "filed January 5, 2 001 and in US Patent Application No. 10 / 179,439, entitled" DIVERSITY TRANSMISSION MODES FOR MIMO QFDM CQMMED, " June 24, 2002. The STTD scheme effectively transmits a subband modulation symbol through two transmitting antennas in each symbol period. However, the STTD scheme distributes the information in each modulation symbol through two successive OFDM symbols. Thus, symbol retrieval at the receiver is based on two consecutive OFDM symbols received. The STTD scheme uses one pair of transmitting antennas for each data subband. Since the access point includes four transmitting antennas, each antenna can be selected for use for half of the 48 subbands. Table 29 lists an exemplary sub-antenna assignment scheme for the STTD scheme.

As shown in Table 29, transmitting antennas 1 and 2 are used for subbands with indices -26, -19, -13 and so on, transmitting antennas 2 and 4 are used for subbands. bands with. indicators -25, -18, -12 and so on, transmitting antennas 1 and 3 are used for subbands with indices -24, -17, -11 and so on. There are six different antenna pairings with four transmitting antennas. Each of the six antenna pairings is used for eight data subbands, which are approximately evenly spaced across the 48 data subbands. The allocation of antenna pairing for subband is such that different antennas are used for adjacent subbands, which may provide greater frequency and spatial diversity. For example, antennas 1 and 2 are used for subband -26 and antennas 3 and 4 are used for subband -25. . The antenna-subband assignment in Table 29 is such that also all four transmitting antennas are used for each code bit for the lowest 1/4 rate, which can maximize spatial diversity. For the 1/4 rate, each code bit is repeated and sent through two subbands (which is also referred to as dual subband repeat encoding). The two subbands used for each code bit are mapped to different antenna pairs so that all four antennas are used to transmit such code bit. As an example, the Del bit indices in Tab 29 correspond to the same code. bit mode for diversity mode, where the index bit 0 is transmitted from antennas 1 and 2 through subband -26 and the index bit 1 is transmitted from antennas 3 and 4 via subband band 1. As another example, bit indexes 2 and 3 in Table 29 correspond to the same code bit, where bit with index 2 is transmitted from antennas 1 and 3 in subband -17 and bit with index 3 is transmitted from antennas 2 and 4 in subband 10. The system can support other Broadcast diversity schemes and this falls within the scope of the invention. As an example, the system may support a space-frequency transmission diversity (5 FT D) which can obtain space and frequency diversity on a per sub-pair basis. An exemplary SFTD scheme operates as follows. Let's assume that two modulation symbols, denoted by s (k) and s (k + 1), are generated and mapped to two adjacent subbands of an OFDM symbol. For the SFTD, the transmitter would transmit the $ {k) symbols. s (k + 1) from two antennas in the subband ke would transmit the + symbols and from the same two antennas through the subband k \ 1. Adjacent subbands are used for the modulation symbol pair as it is assumed that the channel response is constant for the transmission of the two symbol pairs. The processing at the receiver to retrieve the modulation symbols is the same as for the scheme. STTD, except that received symbols are processed for two subbands instead of two OFDM symbol periods. Figure 8B shows a block diagram of one embodiment and a TX 720a diversity processor capable of implementing the STTD scheme for diversity mode. Within the TX 720a diversity processor, a demultiplexer 832 receives and demultiplexes the symbol stream. modulation s [n) from the TX 710a data processor for 48 subflows, denoted as Ji (n) to Sk (n), for the 48 subbands. Each modulation symbol subflow includes a modulation symbol for each symbol period, which corresponds to a symbol rate of (Teim), where Tqfdm is the duration of an OFDM symbol. Each modulation symbol subflow is provided with a respective TX 840 subband diversity processor.

Within each TX 940 subband diversity processor, a demultiplexer 842 demultiplexes the modulation symbols for the subband into two symbol sequences, with each sequence having a symbol rate of (2T0FDM) * 1 · An encoder spacetime 850 receives the two sequences of modulation symbols and, for each period of 2 symbols, uses two symbols λί and s2 in both sequences to form two sets of symbols {χ,} = jy, s]} and {xj} = \ s3 -, ¥ *} for two transmitting antennas.

Each symbol set includes two symbols, one symbol from each of the two sequences. The set of symbols (xj is generated by providing the symbol s first and the symbol s'2 below, where s is obtained via a switch 856a and s) is obtained by taking the conjugate of s2 with a unit 852a and slowing the symbol conjugated by a symbol period with a delay unit 854a Similarly, the {x} symbol set is generated by providing the symbol s2 first and the following symbol, where s2 is obtained by a switch 856b and -s * is obtained by taking the negative conjugate of sl with a unit 852b and delaying the conjugate symbol for a period of symbol with a delay unit 854b. xj shall be transmitted from two antennae i and j assigned to the subband as indicated in Table 29. The time slot encoder 850 provides the first set of symbols | xf | sj} for a buffer / multiplexer 870 for the first transmitting antenna i and the second co set of symbols | xy \ = \ s2 - „sj | to another buffer / multiplexer 870 to the second transmitting antenna j. The two symbols provided by the spacetime encoder 850 for each symbol period are referred to as STTD symbols.

Buffers / multiplexers 870a to 87Qd are used to accumulate and multiplex STTD symbols from all 840 diversity processors. Each buffer / multiplexer 870 receives pilot symbols and STTD symbols from the appropriate TX 840 subband diversity processors, As determined by Table 29, As an example, the buffer / multiplexer 870a receives modulation symbols for subbands -26, -24, -22, -19 and so on {that is, all subbands mapped to antenna 1), buffer / multiplexer 870b receives modulation symbols for subbands -26, -23, -20, -19, and so on (that is, all subbands mapped to antenna 2) # the 870c buffer / multiplexer receives modulation symbols for subbands -25, -24, -20, -18 and so on (ie all subbands mapped to antenna 3) and the 870d buffer / multiplexer receive modulation symbols for subbands -25, -23, -22, -18 and so on (ie all subbands mapped to antenna 4}.

Each buffcr / multiplexer 870 thereafter, for each symbol period, multiplexes four pilots, 24 STTD symbols and 36 zeros for the four pilot subbands, 24 data subbands, and 36 unused subbands, respectively, to form a sequence of 64 transmission symbols for the 64 total subbands. Although there are a total of 48 data subbands, only 24 subbands are used for each transmitting antenna for diversity mode, and the total effective number of unused subbands for each antenna is therefore 36 instead. 12. Each transmission symbol is a complex value (which can be zero for an unused subband} that is sent across a subband in a symbol period. Each buffer / multiplexer 870 provides a transmission symbol stream. x, (n) to a transmitter antenna Each transmit symbol stream comprises concatenated sequences of 64 transmit symbols, one sequence for each symbol period Referring again to Figure 8A, the TX 720a diversity processor provides four transmit streams. transmission symbols, x ^ n) ax «{n}, for four GFDM modulators 722a through 722d. Figure 8C shows a block diagram of one embodiment of an OFDM 722x modulator that can be used for each of the OFDM modulators 722a to 722d in Figure 8A. Within the OFDM 722x modulator, a Fourier inverse fast transform unit (IFFT) 852 receives a stream of transmit symbols, x, (n), and converts each sequence of 64 transmit symbols to its time domain representation. (which is referred to as a transformed symbol) using a 64-point inverse fast Fourier transform. Each transformed symbol comprises 64 time domain samples corresponding to the 64 total subbands.

For each transformed symbol, the cyclic prefix generator 854 repeats a portion of the transformed symbol to form a corresponding OFDM symbol. As mentioned above, one of two cyclic prefix lengths can be used. The cyclic prefix for. the BCH is fixed and is 800 ns. The cyclic prefix for all other transport channels can be selected (either 400 ns or 800 ns) and indicated by the cyclic prefix duration field of the BCH message. For a system with a bandwidth of 20 MHz, a sample period of 50 ns and 64 subbands, each transformed symbol has a duration of 3.2 ms (or 64x50 ns) and each OFDM symbol has a duration of 3 , 6 ms or 4.0 ms, depending on whether the 400 ns or 800 ns cyclic prefix is used for the OFDM symbol.

Figure 8D illustrates an OFDM symbol. The OFDM symbol is composed of two parts: a cyclic prefix having a duration of 400 or 800 ns (8 or 16 samples) and a transformed symbol with a duration of 3.2 μ3 (64 samples). The cyclic prefix is a copy of the last 8 or 16 samples (ie a cyclic continuation) of the transformed symbol and is inserted in front of the transformed symbol. The cyclic prefix assures them that the OFDM symbol retains its orthogonal property in the presence of multipath delay scattering thereby improving performance against detrimental effects of pathways such as multipath and channel scattering caused by selective fading. The cyclic prefix generator 854 provides an OFDM symbol stream to a 656 (TMTR) transmitter. The 856 transmitter 856 converts the OFDM symbol stream to one or more analog signals and additionally amplifies, filters, and up-converts the analog signals to generate a modulated signal suitable for transmission from an associated antenna. The baseband waveform for an OFDM symbol may be expressed by: Eq <3) Where: n denotes the symbol period {ie the symbol index OFDM); k denotes the subband index;

Nsr is the number of pilot and data subchannels; Crtik) denotes the symbol transmitted in the subband k of symbol period n; and Eq <4) where: Tcp is the duration of the cyclic prefix; T $ is the duration of the OFDM symbol; and ff is the bandwidth of each subband. 2. Spatial Multiplexing Mode - Transmission Processing h Figure 9A shows a block diagram of a transmitter unit 900 capable of processing for spatial multiplexing mode. The transmitter unit 900 is another embodiment of the transmitter portion of the access point and user terminal. For spatial multiexing mode, again assuming that four transmitting antennas and four receiving antennas are available, data can be transmitted on up to four spatial channels. A different rate may be used for each space channel depending on its transmission capacity. Each rate is associated with a particular code rate and modulation scheme as shown in Table 25. In the following description it is assumed that Ne spatial channels are selected for use for data transmission, where Ne £ Ns £ min { Ντ, Λ '#}.

Within a TX 710b data processor, framing unit 808 frames the data for each FCH / RCH packet to generate one or more PHY frames for the packet. Each PHY frame includes the number of data bits that can be transmitted on all Ne spatial channels within 6 OFDM symbols. The scrambler 810 scrambles the data for each transport channel. Encoder 812 receives and encodes scrambled data according to a selected coding scheme to provide code bits. In one embodiment, a common coding scheme is used to encode data for all Spatial Trading and different code rates for different spatial channels are obtained by punching the code bits with different punching patterns. Punching unit 814 therefore punctures the code bits to obtain the desired code rate for each space channel. Punching for the spatial multiexing mode will be described in more detail below.

A demultiplexer 816 receives and demultiplexes the code bits from punching unit 814 to provide Ne streams of code bits to the selected spatial Ne channels for use. Each code bit stream is provided for a respective interleaver 818, which interleaves the code bits in the stream through the 48 data subbands. The coding and interleaving for the spatial imitipiexation mode will be described in more detail below. Interleaved data from each interleaver 818 is provided for a respective symbol mapping unit 820.

In spatial multiplexing mode, up to four different rates may be used for the four space channels, depending on the received 5NRs obtained for such space channels. Each rate is associated with a specific modulation scheme, as shown in Table 25. Each mapping unit and symbols 820 maps the interleaved data according to a particular modulation scheme selected for the associated spatial channel to provide modulation symbols. If all four space channels are selected for use, then symbol mapping units 820a through B2Gd provide four modulation symbol streams for the four space channels for a TX 720b space processor. The TX 720b spatial processor performs spatial processing for spatial multiplexing mode. For simplicity, the following description assumes that four transmitting antennas, four receiving antennas, and 48 data subbands are used for data transmission. The data subband indices are given by the set K, where K = ± {1, 6, 8, 20, 22, 26} for the above described OFDM subband structure. The model for a MIMO-OFDM system can be expressed by: Eq (5) Where: 1 A) is a "receive" vector with four inputs for the symbols received through the four receiving antennas for subband k (i.e. is, x (k} ê is a "ransmission" vector with four inputs for the symbols transmitted from the four transmitting antennas to the subband k (i.e. HU) is a channel response matrix (Nu x AV'J for the subband k; en (A) is a additive Gaussian white noise (AWGN) for the subband k. T assumed that the noise vector π \ k) has components. with zero mean and a covariance matrix of Λη - σ'1 where I is the identity matrix and σ 'ó the noise variance, The channel response matrix Η (A) for the subband k can be Eq (6) Where the input htj {k), for ie {i, 2, 3, 4} eje {1, 2, 3, 4} is the coupling (ie the complex gain) between the transmitting antenna i and receiving antenna j for subband A For simplicity, it is assumed that the channel response arrays Η (A) for k and K are known or can be evaluated by the transmitter and receiver. The channel response matrix H [k) for each subband may be "diagonalized" to obtain the autoiodes Ag for such subband. This can be accomplished by decomposing the eigenvalue in the correlation matrix of Η (A), which is 1 (Α) = Ηη (Α) Η (Α), where HJÍ (A) denotes the conjugate transpose of H { k} „The self-decomposition of the correlation matrix R (A) can be expressed by: for A and Jt» Eq (7) Where: V (A) is a unitary matrix {Nr x Nr) whose columns are eigenvectors of R (A), that is, wherein each v, (A) is an eigenvector for an autode; and D (A) is a diagonal matrix (Nr x Nr) of eigenvalues of R (A).

A unitary matrix is characterized by the property MtfM - 1. The self vectors v, (A), for i € (1, 2, 3, 4), are also referred to as transmission direction vectors for each of the space channels. The channel response matrix H (A} can also be diagonalized using single value decomposition, which can be represented by: for ieJí, Eq (8) Where: V {A) is a matrix whose columns are right-hand vectors of H (A1; Σ (A) is a diagonal matrix containing singular values of H (A), which are positive square roots of the diagonal elements of D1A), the eigenvalues of R (A); and IJ (A) is an array whose columns are eigenvectors to the left of H (A). The singular value decomposition described by Gilbert Strang was a book entitled "Linear Algebra and Its Applications", second edition, Academic Press, 1980, as shown in equations {!) And (8), the columns of the matrix Vík} are eigenvectors. of R {k) as well as eigenvectors to the right of Η (A). The columns of the matrix \) {k) are eigenvectors of H (it) JIw {A) as well as eigenvectors to the left of Η (έ). The diagonal matrix DU} for each subband contains non-negative real values along the diagonal and zeros at all other positions. The eigenvalues of R (A) are denoted by {λ · {kl, λ2 (A), (k), λ <(k)} or f X, (k)} for i and 11, 2, 3, 4}. A. The eigenvalue decomposition can be performed independently for the channel response matrix Η (Λ) for each of the 48 data subbands to determine the four autodes for that subband (assuming each matrix H {k) is full category). The four eigenvalues for each diagonal matrix D (A) can be ordered such that (λ-, (k)> λ2 (Α)> (k) â {k)}, where λ * (k) is the largest eigenvalue and ks (k) is the smallest eigenvalue for the subband k. When the eigenvalues for each diagonal matrix D (k) are ordered, the eigenvectors (or columns,) of the associated matrix V (k) are also correspondingly ordered.

A "broadband" autode can be defined as the same-order set of all subbands after sorting (ie, the broadband m (including the m-submodes of all subbands)).

Each broadband autode is associated with a respective set of eigenvectors for all subbands. The "major" broadband automode is that associated with the largest singular value in each of the matrices! (*) After sorting.

A vector d ™ can then be formed to include the mth category eigenvalue for all 48 data subbands. Such a vector d ™ can be expressed by: Eq (9> The vector d1 includes the eigenvalues for the best or main broadband automode.

For a MIMG-GFDM system with four transmitting antennas and four receiving antennas (ie a 4x4 system), there are up to four broadband autodes.

If the noise variance rr at the receiver is constant over the entire operating band and known to the transmitter, then the SNR. The amount received for each subband of each broadband autode can be determined by dividing the eigenvalue (m) by the noise variance. For simplicity, the noise variance can be assumed to be equal to one (ie, σ ': - 1).

For multi-spatial mode, the total transmit power Pmat available to the transmitter can be distributed to broadband automodes based on various power allocation schemes. In one scheme, the total transmission power Ploiai is distributed evenly over all four broadband automodes such that Pm - ΡΙοωι / 4, where Pm is the allocated transmission power for the broadband automode m. In another scheme, the total transmission power Pt0iai is distributed to the four broadband automodes using one. proceeding by "water filling"). The "water fill" procedure distributes power such that the higher power gain broadband autodes receive larger fractions of the total transmit power, the amount of transmit power allocated to a given broadband autode determined by your received SHR, which in turn depends on the power gains (or eigenvalues) for all subbands of such a broadband auto. The "water fill" procedure can allocate zero transmission power to broadband automobiles with sufficiently poor received SNRs. The "water filling" procedure receives β = {/? ,, β2 <β3, βΑ \ for the four broadband automodes, where βΜ is a normalization factor for the broadband automode and can be expressed by : Eq (10) The normalization factor β „keeps the transmitting power allocated to the m invariable broadband automaton after channel inversion is applied as described below. As shown in equation (10), the normalization factor βΜ can be derived based on the eigenvalues in the dm vector and assuming that the noise variance is equal to one (ie, ü "= 1]. 0 procedure by" "water fill" below determines the fraction am of the total transmission power to be allocated to each broadband autode based on the set β such that spectral efficiency, or some other criterion, is optimized. transmission allocated to the broadband autode m by the "water fill" procedure can be expressed as: Bq (ll) The power allocations for the four broadband autodes can be given by a = {a ,, a ,, a4}, where the spatial multi-multiplexing mode can be selected for use if more than one value in set a is non-zero, the procedure for "water filling" is known to those skilled in the art and will not be described here.A reference describing the "water filling" has been described by Kofaert G. Galiager in "Information Theory and Reliable Communication", John Wiley & Sons, 1968, which is incorporated herein by reference.

For spatial multi-multiplexing mode, the rate for each spatial channel of the broadband auto mode can be selected with. based on the received SNR obtained by such a broadband spatial / autorood channel with its allocated transmit power of Pm. For simplicity, the following description assumes data transmission on broadband automodes. The SNR received for each broadband autode can be expressed by;

Eq (12) In one embodiment, the rate for each broadband auto mode is determined based on a table that includes the rates supported by the system and a range of SNRs for each rate. Such a table can be obtained by computer simulation, empirical measurements and so on. The particular rate to use for each broadband automode is the rate in the table with a range of SNRs covering the SNR received for the broadband automode. In another embodiment, the rate for each broadband automode is selected based on (1) the SNR received for the broadband automode, (2 3 on an SNR offset used to compensate for estimation errors, MIMO channel variability, and others. (3) a table of supported charges and their required SNRs For such an average received SNR for each broadband auto is initially computed as described above or as an average of received SNRs (in units of dBsj). for all broadband automode subbands In either case, an operating SNR is computed below as the sum of the received SNR and the SNR offset (where both are given in units of dBs). The operating rate is then compared to the required SNR for each of the rates supported by the system.The highest rate in the table with a required SNR that is less than or equal to the operating SNR is then selected for the broadband automode, h rate pa The transmission diversity mode and the beam steering mode can also be determined in a similar manner. The transmitting power Pm allocated to each broadband autode may be distributed across the 43 data subbands of such broadband automata such that the SNRs received for all subbands are approximately equal. Such uneven power allocation across the subbands is referred to as channel inversion. The transmit power Pm (k) allocated to each subband can be expressed by: Bq (13) Where β „is given by the equation í 10}.

As shown in equation (13), the transmission power Pm is distributed non-uniformly across the data subbands based on their channel power gains, which are given by the eigenvalues λ „(k), for k and K. h The power distribution is such that approximately equal incoming SNRs are obtained at the receiver for all data subbands of each broadband auto. Such channel reversal is performed independently for each of the four broadband automodes. Broadband auto channel reversal is described in more detail in US Patent Application Serial No. 10 / 229,709, entitled "CODED MIMO SYSTEMS WITII SELECT VE CHANNEL INVERSION APPLIED PER EIGEMMODÉ", filed August 27, 2002, Channel reversal can be done in several ways. For. full channel inversion, all data subbands are used for data transmission if a broadband auto mode is selected for use. For selective channel inversion, all or a subset of the available data subbands can be selected for use with each broadband autode. Selet Selective channel inversion discards weak subbands with SNR received below a particular limit and performs channel inversion only on the subbands if Selected. Selective channel inversion for each broadband autode is also described in US Patent Application Serial No. 10 / 229,209 entitled "CODED MIMO SYSTEMS WITH SELECTIVE CHANNEL INVERSION APPLIED PER EIGENMODE" filed August 27, 2002. For simplicity, the following description assumes that complete channel inversion is performed for each broadband autode selected for use. The gain to use for each subband of each broadband auto can be determined based on the. transmission power Pmik) allocated to such subband. The gm {k} gain for each data subband can be expressed by: Eq (14) A diagonal gain matrix G (k) can be defined for each subband. Such matrix G (A) includes the gains for the four autodes for the subband k along the diagonal and can be expressed by: G (A} -diag [gl (A), g2 (A), g3 [k ' i, g4 (A)].

For spatial multi-multiplexing mode, the transmission vector x (k) for each data subband can be expressed as: oara kEK, Eq (15) where: and 0 sik vector includes four modulation symbols to be transmitted via the four subband autodes and the vector x (k) includes four transmit symbols to be transmitted from the four antennas to the subband k. For the sake of simplicity, equation (15) does not include the correction factors used to compensate for differences between the transmit and receive strings at the access point and user terminal, which will be described in more detail below. Figure 9B shows a block diagram of a TX 720b spatial processor embodiment capable of spatial processing for spatial multiplexing mode. For simplicity, the following description assumes that all four broadband automodes are selected for use. However, less than four broadband automodes may also be selected for use.

Within processor 720b, a demultiplexer 332 receives the four streams of modulation symbols (denoted as Si (n) to be transmitted through the four broadband autodes, demultiplexing each stream in 48 subflows to the 48 subbands). and provides four modulation symbol subflows for each data subband to a respective TX 940 subband space processor. Each processor 940 performs the processing shown in equation (15) for a subband.

Within each TX 940 subband space processor, the four subflows of modulation symbols (denoted as $ ik) a are provided with four multipliers 942a to 942d, which receive the gains gilk), gi (k), g3 ik) eg /, {k) for the four autodes of the associated subband. Each gain gmík) can be determined based on the transmit power Pm (k) allocated for that subband / autode as shown in equation (14). Each multiplier 942 scales its modulation symbols with its gmik gain) to provide staggered modulation symbols. Multipliers 942a through 942d provide four scaled modulation symbol subflows for four beamformers 950a through 950d, respectively.

Each beamformer 950 beamforms to transmit a subflow of symbols through a one-subwoofer. Each beamformer 950 receives a subflow of symbols sm (k) and an eigenvector v *, (A) for the associated autode. In particular, beam former 950a receives eigenvector vt (A :) for the first autode, beam former 950b receives eigenvector V2 (k) for the second autode and so on. Beam formation is performed using the eigenvector for the associated autode.

Within each beam former 950, the stepped modulation symbols are provided with four multipliers 952a. 9S2d, which also receive four elements, vm, i \ k), vm /, ik), ΐ! β | 1 [ί} and vfflr4 (A), from the eigenvector Vjr, (k) for the associated autode. Each multiplier 952 thereafter multiplies the scaled modulation symbols by its eigenvector value v „rJ (k) to provide" formed beam "symbols. Multipliers 952a through 952d provide four subflows of formed beam symbols (which must be transmitted from four antennas) to adder 960a to 960d, respectively.

Each sender 960 receives the sum of four beam symbols formed for the four autodes for each symbol period to provide a preconditioned symbol for an associated transmitter antenna. Adders 960a to 96Qd provide four preconditioned symbol subflows for four transmitting antennas for buffers / multiplexers 970a to 97Qd, respectively.

Each buffer / multiplexer 970 receives pilot symbols and preconditioned symbols from the TX 940a to 94 Ok subband space processors for use for the 48 data subbands. Each buffer / multi plexifier 970 below, for each symbol period, has 4 pilot symbols, 48 preconditioned symbols and 12 zeros for 4 pilot subbands, 48 data subbands and 12 subbands. not used, respectively, to form a sequence of 64 transmission symbols for such symbol period. Each buffer / multiplexer 970 provides a transmit symbol stream x, (n) to a transmit antenna, wherein the transmit symbol stream comprises concatenated sequences of 64 transmit symbols. Transmit symbols can be scaled with correction factors to compensate for differences between the transmit / receive chains at the access point and at the user terminal as described below. Subsequent OFDM modulation for each transmission symbol stream has been described above.

Parallel symbol streams can also be transmitted from the four transmitting antennas without spatial processing at the access point using non-directed spatial multipexing mode. For such mode, the channel inversion process and beam formation by beam former 950 may be omitted. Each modulation symbol stream is further processed by OFDM and transmitted from a respective transmitting antenna. The undirected spatial multipexing mode can be used for a variety of situations, such as if the transmitter is unable to perform the spatial processing required to support beam steering based on autode decomposition. This may be because the transmitter has not performed calibration procedures, is unable to generate a sufficiently good estimate of the channel, or has no autode processing and calibration capability. For the non-directed spatial multi-mode mode, spatial multi-mode is still used to increase transmission capability but spatial processing to separate individual symbol streams is performed by the receiver.

For non-directed spatial multi-mode mode, the receiver performs spatial processing to retrieve the transmitted symbol streams. In particular, a user terminal may implement a channel correlation matrix inversion (CCMI) technique, a minimum squared mean error (ΜΜΞΕ) technique, a successive interference cancellation receiver processing technique, or some other technique. of spatial receiver processing. Such techniques are described in detail in US Patent Application Serial No. 0 9 / 993,087 entitled "MULTIPLL-ACCESS MULTIPLE-INPUT MUI.T1PLE-OUTPUT (MIMO) COMMUNICATION SYSTEM" filed November 6, 2001. The method of Untargeted spatial multiplexing can be used for downlink and uplink transmissions. The mode of mui. Multi-user spatial multiplexing supports data transmission to multiple user terminals simultaneously via downlink based on user terminal "spatial signatures". The spatial signature for a user terminal is given by a caria response vector (for each subband) between the access point antennas and each user terminal antenna. The access point can obtain spatial signatures, for example, based on the directed reference transmitted by the user terminals. The access point may process the spatial signatures for user terminals desiring data transmission to (1) select a set of user terminals for simultaneous data transmission via downlink and (2) derive targeting vectors for each of the data streams. independent data to be transmitted to the selected user terminals.

Targeting vectors for multiuser spatial multiplexing mode can be derived in various ways. Two exemplary schemes will be described below. For simplicity, the following description covers a subband and assumes that each user terminal is equipped with a single antenna.

In a first scheme, the access point obtains the direction vectors using channel inversion. The access point can select Ν „ρ single antenna user terminals for simultaneous downlink transmission. The access point obtains a 1x Nap channel response line vector for each selected user terminal and forms an N (ip x Nap channel response matrix, with the Nap nha s vectors for the Μ (ψ The following access point obtains an Hsteer matrix of Nap targeting vectors for the Nap user terminals selected as Hir, rr = .The access point may also transmit a directed reference to each selected user terminal. The user terminal processes its directed reference to estimate channel and phase gain and coherently demodulates the symbols received for its single antenna with channel gain and phase estimates to obtain retrieved symbols.

In a second scheme, the access point pre-encodes symbol streams to be sent to the user terminals such that such symbol streams suffer little cross talk at the user terminals. The harassment point can form the channel response matrix for the selected user terminals and perform QR factorization over HMtJ such that H ** = Ftnf »» * * where TtIl is a lower left triangular matrix Ttra and is a unitary matrix. The following access point pre-encodes the data symbol streams with the T.ri matrix to obtain Vop pre-coded symbol streams and further processes the pre-coded symbol streams with the unit matrix to obtain the Nap flows from symbols to transmission to. transmit to the user terminals. Again, the access point may also transmit a directed reference to each user terminal. Each user terminal uses the directed reference to coherently demodulate its received symbols to retrieve retrieved symbols.

For uplink in multiuser spatial multi-mode mode, the harassment point can retrieve Nup symbol streams simultaneously transmitted by Nap user terminals using MMSE receiver processing, successive interference cancellation, or some other receiver processing technique. The access point may estimate the uplink channel response for each user terminal and use the channel response estimate for receiver spatial processing and for programming uplink transmissions. Each single antenna user terminal can transmit an orthogonal pilot via uplink. Uplink pilots coming from user terminal NAPs may be orthogonal in time and / or frequency. Temporal orthogonality can be achieved by having each user terminal cover its uplink pilot with an orthogonal sequence assigned to the user terminal. Frequency orthoqonality can be obtained by having each user terminal transmitting its uplink pilot through a different set of subbands. Uplink transmissions from user terminals should be approximately time-aligned at the access point (for example, time-aligned within the cyclic prefix}. 3 Beam Steering Mode - Transmission Processing Ά Figure 1GA shows a diagram of blocks of a transmitter unit 1000 capable of transmitting processing for beam steering mode The transmitter unit 1000 is yet another embodiment of the transmitter portion of the access point and user terminal.

Within a TX 710c data processor, framing unit 808 frames the data for each PCH / RCH packet to generate one or more PHY frames for the packet. The following scrambler 810 scrambles the data for each transport channel. The following encoder 812 encodes the framed data according to. a coding scheme selected to provide bits of code. The punching unit 814 then punctuates the code bits to obtain the desired code rate for the broadband automode used for data transmission. The code bits from punch unit 818 are interleaved across all data subbands. The following symbol mapping unit 820 maps the interleaved data according to a selected modulation scheme to provide modulation symbols. A TX 720c space processor below performs transmission processing over the modulation symbols for beam steering mode. The beam steering mode can be used for data transmission over a space channel or broadband autode - typically that associated with the highest eigenvalues for all data subbands. The beam steering mode can be selected if the transmission power allocation for broadband automodes results in. only one entry in set α other than zero. While the spatial multiplexing mode beam forms for each of the selected subband autodes based on its eigenvector, the beam steering mode performs beam steering based on a "normalized" eigenvector. main mode of each subband for data transmission via such a single mode.

The four elements of each eigenvector v <(k} for k and K for the main autode can have different magnitudes.The four preconditioning symbols obtained from the four eigenvector elements v, {k} for each subband can Therefore, the four antenna transmission vectors, each of which includes the preconditioned symbols for all data subbands for a given transmitting antenna, may have different magnitudes. each limited soybean transmitter antenna (for example, due to power amplifier limitations), then the beamforming technique may not fully utilize the total power available for each antenna. from the eigenvectors vt (A), to k and K to the main eigenvector and normalizes each eigenvector such that all four vector have equal magnitudes, the normalized eigenvector v (A) for subband k can be expressed by;

Eq (16) Where; A is a constant (for example, A = 1); and Q, {k) is the phase for the transmitting antenna subband k /, which is given by;

Eq (17) As shown in equation (17), the phase of each element in the vector v (*) is obtained from the corresponding eigenvector element Vi [k] (that is, θ, íA) is obtained from v Wherein R channel inversion can also be performed for beam steering mode so that a common rate can be used for all data subbands. The transmit power / *, (&) allocated for each data subband for beam steering mode can be expressed by: Eq OS) Where; / ?, is a normalization factor that maintains the invariable total transmission power after channel inversion is applied; F is the transmit power allocated to each of the four antennas; and m is the power gain for the subband k of the main autosode for beam steering mode. The normalization factor /? Can be expressed by: Eq (19) The transmit power F can be given as! ', · = Ptalai! 4 (ie uniform allocation of total transmit power by the four transmitting antennas) . The power gain 1, 'may be expressed by: Eq (20) Channel inversion results in power allocation from /' (&), for k and K, for the 48 data sub-bands. The gain for each data subband can then be given as g (k) = ^ /, (K).

For beam steering mode, the transmission vector x (k) for each subband can be expressed by: Eq (21) Again, for simplicity, equation (21} does not include the correction factors used to compensate. Differences between the transmission / reception chains at the end of the user period.

As shown in equation (16), the four elements of the normalized targeting vector v (fc) for each subband have equal magnitude but possibly different phases. Beam steering therefore generates a transmission vector x (Jc) for each subband, with the four elements of x (k) having the same magnitude but possibly different phases. Figure 1GB shows a block diagram of one mode of the beam. TX 720c space processor capable of performing spatial processing for beam steering mode.

Within processor 720c, a demultiplexer 1032 receives and demultiplexes the flow of modulation symbols s (n) into 48 subflexes for the 48 data subbands (denoted by s (l) to s (k)). Each symbol subflow is provided with a respective TX 1040 subband beam routing processor. Each processor 1040 performs the processing presented in equation (14) for a subband.

Within each TX 1040 subband beam routing processor, the modulation symbol subflow is provided to a multiplier 1042, which also receives the gain (*) for the associated subband. The following multiplier 1042 steps the gain modulation symbols g (k) to obtain stepped modulation symbols, which are then provided with a beam steering unit 1050. The beam steering unit 1050 also receives the eigenvector normalized v (/ r) for the associated subband. Within the beam steering unit 1050, the stepped modulation symbols are provided with four multipliers 1052a to 1052d, which also respectively receive the four elements of the normalized eigenvector v (ifc). Each multiplier 1052 multiplies its scaled modulation symbols by its normalized eigenvector value v (/ c) to provide preconditioned symbols. Multipliers 1032a through 1052d provide four preconditioned symbol subflows for buffers / multiplexers 1070a through 1070d, respectively.

Each 1070 buffer / multiplexer receives pilot symbols and preconditioned symbols from TX lG40a to 1010k subband beam steering processors for the 48 data subbands, multiplexes pilot and precondition symbols, and zeros for each symbol period and provides a transmission symbol stream x, {n} to a transmitting antenna, and subsequent OFDM modulation for each transmission symbol stream has been described above. Processing for beam steering mode is described in US Patent Application Serial No. 10 / 228,393, entitled "STE-STEERING AND BEAM-FORMING FOR WIDEBAND MIMO SYSTEMS", filed August 27, 2002. The system may It may also be designed to support a beamforming mode, whereby a data stream is transmitted through the main auode using the eigenvector instead of the standard eigenvector.

Framing For PHY Frames Figure 11A shows one embodiment of framing unit 808 that is used to frame data for each FCB / RCH packet prior to subsequent processing by the TX data processor. Such framing function can be bypassed for messages sent via BCH, FCCH and RACH. The framing unit generates an integer number of PHY squares for each FCH / RCH packet, in. each PHY frame comprises 6 OFDM symbols for the embodiment described herein.

For diversity and beam steering modes, only one space channel or broadband auto mode is used for data transmission. The rate for such a mode is known and the number of bits of information that can be sent on the payload of each frame can be computed. For the multi-spatial mode, multiple space channels may be used for data transmission. Since the rate of each space channel is known, the number of bits of information that can be sent in the payload of each PHY frame for all space channels can be computed.

As shown in Figure 11A, the information bits (denoted by:) for each FCH / RCH packet are provided to a CRC generator 1102 and a multiplexer 11 CM inside. of frame unit 808. CRC generator 1102 generates a CRC value for the bits in the header (if present) and payload fields of each PHY frame and provides CRC bits for multiplexer 1104. Multiplexer 1104 receives the information bits, CRC bits, header bits, and fill bits (for example, zeros) and provides such bits in the appropriate order, as shown in Figure 6, based on a signal from PHY frame control. The framing function can be bypassed by providing the information bits directly through the multiplexer 1104. The framed or non-framed bits (denoted by d \ d2 d $ ...) are provided to the scrambler 810. 5. Embara1harnenic In a fashion 1 At this time, the data bits for each transport channel are shuffled before encoding. Scrambling randomizes the data so that a whole long sequence of one or all zeros is not transmitted. This may reduce the change in peak to average power of the OFDM waveform. Shuffling may be omitted for one or more transport channels and may also be selectively enabled and disabled. Figure 11A also shows an embodiment of scrambler 810. In such an embodiment, scrambler 810 implements a generator polynomial: Eq (22) Other generator polynomials may also be used and this falls within the scope of the invention. * As shown in Figure 11A, scrambler 810 includes seven delay elements 1112a α 111? g coupled in series. For each clock cycle, an adder 1114 adds module 2 of two bits stored in delay elements ili2d and 1112g and provides a scramble bit for delay element 1112a.

The framed / non-framed bits (di dj d3 dA ...) are provided to an adder 1116 which also receives scrambling bits from adder 1114. Adder 1116 adds module 2 of each bit d „with a corresponding scramble bit to provide a scrambled bit qH. The scrambler 810 provides a scrambled bit sequence, which is denoted by q1 qs qA ... - The scrambler's initial state (ie, the delay element contents 1112a to 1112g) is set to a different 7-bit number. zero at the beginning of each TDD frame. The three most significant bits {MSBs} (that is, delay elements 1112e through 1112f5 are always set to one ("1") and the four least significant bits (LSBs 1 are set to the TDD frame counter as indicated). In one embodiment, a single base code is used to encode data prior to transmission such base code generates bits. All other code rates supported by the system (as listed in Table 25) can be obtained either by repeating or punching the code bits * Figure 11B shows one embodiment of encoder 812 which implements In such embodiment, the base code is a convolutional code, rate 1/2, constraint length 7 (K = 7), with generators 133 and 171 (octagonal).

Within encoder 612, a multiplexer 1120 receives and mis 1 f. , includes scrambled bits and tail bits (for example, zeros). Encoder 812 also includes six serially coupled delay elements 1122a through 1122f. Four adders 1124a through 1124d are also coupled in series and are used to implement the first generator (133). Similarly, four adders 1126a through H26d are coupled in series and are used to implement the second generator (171). The adders are also coupled to the delay elements in order to implement the two 133 and 171 generators as shown in Figure 11B.

The scrambled bits are provided to the first delay element 1122a and the adder 1124a and 1126a. For each clock cycle, adder 1124a through 1124d adds module 2 of the received bit and four previous bits stored in delay elements 1122b, 1122c, 1122e and 1122f to provide the first code bit for such a clock cycle. Similarly, adders 1126a through 1126d add modulus 2 of the received bit and four previous bits stored in delay elements 1122a, 1122b, 1122c and 1122f to provide the second code bit for such a clock cycle. Are the code bits generated by the first generator denoted as \ a? «3 <jt4 ..., and the code bits generated by the second generator are denoted as hi b2 bj hq .... The following multiplexer 1128 receives and multiplexes the two code bit streams from the two generators into a single code bit stream which is denoted as ai b \ a2 b2 ui bj bt. . . For each scrambled bit qn, two code bits a and b are generated, which results in a code rate of 1/2. Figure 11B also shows one embodiment of the repeat / punch unit 814 that can be used to generate other code rates based on the 1/2 code rate. Within unit 814, the 2/2 rate code bits from encoder 812 are provided with a repeat unit 1132 and a punch unit 1134. A. repeat unit 1132 repeats each rate code bit 1/2 once to get an effective code rate of 1/4. Punching unit 1134 erases some of the 1/2 rate code bits based on. a specific punching pattern to provide the desired code rate. Table 30 lists exemplary punching patterns that can be used for the various code rates supported by the system. Other punching patterns may also be used and this falls within the scope of the invention.

Table 30 To obtain a code rate of k / n, punch unit 1134 provides n code bits for each group of 2k 1/2 rate code bits received from encoder 812. Thus, 2k - n code bits are deleted from each group of 2A code bits. The bits to be deleted from each group are denoted by zeros in the punishment pattern. As an example, to obtain a code rate of 7/12, two bits are deleted from each group of 14 code bits from the 812 encoder, with the deleted bits being the 8- and 14Cl code bits in the group, such as denoted by the punching pattern of ”11111110111110". No punching is performed if the desired code rate is 1/2.

A multiplexer 1136 receives the code bit stream from the repeat unit 1132 and the code bit stream from the punch unit 1134. The next router 1136 provides the code bits from the repeat unit 1132 if the rate of desired code rate is 1/4 and the code bits from punch unit 1134 if the desired code rate is 1/2 or higher.

Punching codes and standards other than those described above may also be used and this falls within the scope of the invention. As an example, a turbo code, a block code, some other codes, or any combinations thereof may be used for code data. In addition, different coding schemes may be used for different transport channels. For example, convolutional encoding can be used for common transport channels and turbo encoding can be used for dedicated transport channels. 7. Interleaving In one embodiment, the code bits to be transmitted are interleaved across the 48 data subbands. For diversity and beam steering modes, a stream of code bits is transmitted and interleaved across all data subbands. For spatial multi-multiplexing mode, up to four code bit streams can be transmitted over up to four spatial channels. Interleaving can be performed separately for each space channel such that each code bit stream is interleaved across all data channel subbands used for transmitting such a stream. Table 29 shows an exemplary assignment of code bits and subbands that can be used for interleaving all transmission modes.

In one embodiment, interleaving is performed across all 48 data subbands in each interleaving interval. For such an embodiment, each group of 48 bits of code in a stream is spread over the 48 data subbands to provide frequency diversity. The 48 code bits in each group can receive indexes from D to 47. Each code bit index is associated with a respective subband. All bits of code with a particular index are transmitted in the associated subband. As an example, the first code bit (with index 0) in each group is transmitted in subband -26, the second code bit (with index 1) is transmitted in subband 1, the third code bit (with index 1). index 2) is transmitted in subband -17 and so on. Such an interleaving scheme can be used for diversity, beam steering and spatial multiplexing modes. An alternative interleaving scheme for spatial multiplexing mode will be described below. The merge can be alternatively or additionally performed over time. By way of example, after interleaving across the data subbands, the code bits for each subband may also be interleaved (e.g. by a PHY frame or a PDU) to provide temporal diversity. For spatial multiplexing mode, interleaving can also be performed across multiple spatial channels.

Additionally, interleaving can be employed across the dimensions of the QAM symbols such that the code bits forming the QAM symbols are mapped to different bit positions of the QAM symbols. 8 Table 31 shows symbol mapping for various system supported modulation schemes. For each modulation scheme (except for the BPSK), half the bits are mapped to a component in phase (I) and the other half of the bits are mapped to a quad component (Q). In one embodiment, the signal constellation for each supported modulation scheme can be set based on the Gray mapping. With Cray mapping neighboring points in the signal constellation (in both I and Q components) differ by only one bit position. Gray mapping reduces the number of bit errors for more likely error events, which corresponds to a received symbol being mapped to a location close to the correct location, in which case only one bit of code would be received in error.

Table 31 The I and Q values for each modulation scheme presented in Table 31 are scaled by a normalization factor K, mrm such that the average power of all signal points in the associated signal constellation is equal to the unit. The normalization factor for each modulation scheme is presented in Table 31. Quantified values for the normalization factors for supported modulation schemes can also be used. A modulation symbol $ from a particular signal constellation would then have the following form: where 1 and Q are the values in Table 31 for the signal constellation.

For a given PDU, modulation may be different across the PDU and may be different for multiple spatial channels used for data transmission. As an example, for the BCH PDU, different modulation schemes may be used for the signaling pilot, the MIMO pilot and the BCH message. 9. Processing for Spatial Multi-Exposure Mode For the fear of multiple spatial multiplexing, a PDU can be transmitted across multiple space channels. Various schemes can be used to process data for transmission across multiple space channels. Two processing schemes specific to the multi-spatial mode. will be described below.

In the first processing scheme, coding and punching are performed on a per channel space basis to obtain the desired code rate for each space channel. Serial Ag channels to be used for data transmission are rated from highest received to lowest SNK. Data for the entire PDU is first encoded to obtain a 1/2 rate code bit stream. The code bits are then punctured to obtain the desired code rate for each space channel. Punching can be done sequentially for the Ng space channels, from the best (ie highest SNR) to the worst {ie lowest # SNR} space channel. In particular, the punching unit first punctures for the best space channel with the highest received SNR. When the correct number of code bits have been generated for the best spatial channel, the punching unit then punches for the second best spatial channel with the next highest received SNR. This process continues until the code bits for all Ng space channels have been generated. The order for punching is from highest to lowest SNR received, regardless of the specific code rate used for each space channel.

For the example shown in Table 28, the 34 56 bits of information to be transmitted in the total PHY frame are first encoded with the 1/2 rate base code to obtain 6912 bits of code. The first 3168 code bits are punctured using the code rate punch pattern 11/16 to obtain 2304 code bits, which are provided in the PHY frame for the first space channel. The next 2592 code bits are then punctured using the code rate punch pattern 3/4 to obtain 1728 code bits, which are provided in the PHY frame for the second space channel. The next 864 bits of code are then punctured using the punching pattern for the 3/4 code rate to obtain 576 bits of code, which are provided in the PHY frame for the third spatial channel. The last 288 code bits for frame PHY are then punctured using the punching pattern for code rate 1/2 to obtain 288 code bits, which are provided in frame ΡΗΎ for the last spatial channel. four individual PHY frames are further processed and transmitted over the four space channels. Punching for the next complete PHY frame is then performed similarly. The first processing scheme may be implemented by the TX 710b data processor in Figure 9 Ά.

In the second processing scheme, coding and punching are performed for subband pairs. In addition, coding and punching occur in cycles across all selected space caries of each subband pair. Figure 11C shows a block diagram illustrating a TX 710 data processor implementing the second processing scheme. Encoder 812 performs convolutional 1/2 rate encoding of scrambled bits from scrambler 810. Each space channel receives a particular rate, which is associated with a specific combination of code rate and modulation scheme, as shown in Table 25. Let bm be the number of code bits per modulation symbol for the spatial channel m (or equivalent equivalent). , the number of code bits sent in each data channel of the space channel m} and rm the code rate used for the space channel m 0 goes ο * 'to bm depends on the size of the modulation scheme constellation used In particular, bm - 1, 2, 4, 6 and 8 for BPSK, QPSK, 16-QAM, 64-QA.M and 256-QAM, respectively.The 812 encoder provides a bit stream of rate code 1/2 for the 816 demultiplexer, the which demultiplexes the stream of code bits received in four subflows into the four spatial channels. The demultiplexer is such that the first 4ό * bitsι code bits are sent to buffer 813a for space channel 1, the next 4 £> r,> code bits are sent to buffer 813b for space channel 2 and so on. against. Each 813 buffer receives 4 bmrm code bits each time the 816 demultiplexer passes through all four spatial -1 channels. A total of h (jd - 4hm rm of nj-½ rate code bits is provided for the four buffers 813a through 813d for each cycle. The demiplexer 816 thus passes through all four positions for the four space channels every & total code bits, which is the number of code bits that can be sent in a pair of subbands using all four space channels.

Once each buffer 813 has been filled with 4hmrm code cnips for the associated space channel, the code bits in the buffer are punctured to obtain the code rate for that space channel. Since 4bmrm 1/2 rate code bits comprise an integer number of punching periods for each punching pattern, exactly 2bm code bits are provided after punching for each spatial channel m. The 2bm code bits for each space channel are below distri. bu d c s (I nter side 5 through the data subbands.

In one embodiment, interleaving is performed for each space channel in groups of 6 subbands at a time. The code bits after punching for each spatial channel can be numbered sequentially as c „for i = 0, 1, 2, .... A Cm counter may be maintained for each space channel to count each group of 6bm code bits provided by the punching unit for such a space channel. As an example, for QPSK with bm = 2, the counter would be set to C, H = 0 for code bits c0 to cu provided by the punctuation unit, Cm = 1 after code bits Cj2 to c2j, and so on. The counter value Cm for space channel m can be expressed by: C „= [iV (6fr„) Jmod8. Eq (23) To determine the sub-beat for which the code bit c is assigned, the bit index for the code bit is first determined as follows: bit index = (nnode) + 6-Cm Eq (24) The bit index is then mapped to the corresponding subband using Table 29.

For the above example, the first group of 6 bits of code cq ac \ is associated with bit indexes 0 to 5 respectively, the second group of 6 bits of code cg acn is also associated with bit indexes 0 to 5 respectively . The code bits cc and cg would be mapped to subband -26, the code bits c ·, and Ci would be mapped to subband 1, and so on, as shown in Table 29. Spatial processing can so start for this first group of 6 subbands. The third group of code bits c \ 2 to> 7 (with Cra = 1} is associated with bit indices 6 to 11 respectively and the fourth group of 6 code bits Cu to t'23 is also associated with bit indexes 6 through 11. Bits c and c: 8 would be mapped to subband -2 5, code bits ci.i and cg 'would be mapped to subband 2, and so on. Spatial processing can then begin for this next group of 6 subbands.The number 6 in the equation (24 3 comes from the fact that interleaving is performed in groups of six subbands. The operation (mod 8) in the equation. (23) stems from the fact that there are eight interleaving groups for the 48 data subbands since each cycle of demulplexer 816 shown in Figure 11C produces enough code bits to populate two subbands of each autode. bandwidth, a total of 24 cycles is required to provide the 4Bbm code bits for one OPDM symbol for each spatial channel Interaction in groups of 6 subbands at a time can reduce processing delays. In particular, spatial processing can begin each time each group of 6 subbands is available.

In other ways, interleaving can be performed for each space channel in groups of Λ! B subbands at a time, where: Vfi can be any integer (for example, Ng can be 4 8 for interleaving). over all 48 data subbands] VI Calibration For a TDD system, downlink and uplink share the same frequency band in a time division duplexed manner, in which case there is typically a high degree of correlation between downlink and uplink channel responses Such a correlation can be exploited to simplify channel estimation and spatial processing For a TDD system, each wireless link subband can be assumed to be reciprocal. that is, if Η (A} represents the channel response matrix of antenna array A for antenna array B for subband kr then a channel, reciprocal implies that the coupling of array B to arrangement A is given. transposed by Hi £), which is Hr (A5.

However, the responses (gain and phase) of the transmit and receive chains at the access point are typically different from the transmit and receive chain responses at the user terminal. A calibration can be performed to determine the difference in frequency responses of the transmit and receive strings at the access point and user terminal and to compensate for the difference so that calibrated downlink and uplink responses can be expressed in same terms. Once the transmit and receive chains are calibrated and compensated, a measurement for one link (eg the downlink) can be used to derive targeting vectors for the other link (eg the uplink).

The "effective" downlink and uplink channel responses, Mithi) and Hup {£}, which include the applicable transmit and receive chain responses at the access point and user terminal, can be expressed by: for kt K, and Eq (25) for ke K, where: T, 3p ik} and R ^ p {k) are diagonal matrices of Nv x Nap with entries for the complex gains associated with the transmission chain and reception chain, respectively, for the Nap antennas at the access point for subband k; T, JL li) and RuC [k) are Ni x NM diagonal arrays with inputs to the complex gains associated with the transmission chain and the reception chain, respectively, for the new user terminal antennas for the subband k ; and | i {À'í ó a channel response matrix of, VW x Νίψ for the downlink.

By combining the two equations into the set of equations (2b), the following equation can be obtained: Eq (26) where C left side of equation (26) represents the "true" calibrated caries response in the uplink and the right side represents the transposed of the "true" calibrated channel response in the downlink. Applying the diagonal (k) and Km (k) arrays to the effective downlink and uplink channel responses, respectively, as shown in equation (26), allows the downlink and uplink calibrated channel responses to be expressed as transposed. of each other, the diagonal matrix x \: αρ) Ka [> ik) for the access point is the ratio of the receiving chain response R ^ iA) to the response of the transmission chain Tap [k) (ie, where the ratio is taken element by element Similarly, the diagonal matrix [Nut x N i), Kat (k), for the user terminus is the ratio of the receive string response (k) to the response The transmission chain Tu [(k [, The matrices Kap ik) and Kut ik) include which may compensate for differences in the transmission and reception chains at the access point and at the user terminal. This would then allow the channel response to a link to be expressed by the channel response to. the other · link as shown in equation (26).

A calibration can be performed to determine the Kaf matrices (A; ie Km (A). Typically, the true channel response H (A) and the transmit and receive chain responses are neither known nor can be evaluated. Exactly Or Easily. In addition, downlink and uplink channel responses, H <ink) and H „p (k}, can be estimated from pilots sent via downlink and uplink, respectively, as described below. The estimates of the matrices Κ * ρ (k) and Ku, ik), which are referred to as the correction matrices Ka [t (£) and Ka (A), can then be derived based on the channel response estimates. of downlink and uplir.k, Ηώ (Α) and H, ip (A), as described below. The Kap (A) and K1 | S (*) arrays include correction factors that can compensate for differences in the transmission and reception chains at the access point and user terminal.

The "calibrated" downlink and upiink channel responses observed by the user terminal and access point, respectively, can then be expressed by: for ke K, and Eq (27) for k € K, Where Η * Αι (ί) and UP1 |! (&) Are estimates of the "true" calibrated channel response expressions in equation {26). By combining the two equations in the set of equations (27) using the exaggeration in equation (26), it can be shown that Λ ratio accuracy Μ „ρ (*)» Η ^ π (*) depends on the accuracy of matrices K ( fc) and Kul (&), which in turn typically depends on the quality of downlink and upiink channel response estimates, Hdn (i) and Η (A). Calibration can be performed using various schemes. For clarity, a specific calibration scheme will be described below. To calibrate, the user terminal initially captures the timing and frequency of the access point based on the signaling pilot transmitted through the 3CH. The following user terminal sends a message via AACH to initiate a calibration procedure with the access point. Calibration can be performed in parallel with registration / authentication.

Since the frequency responses of the transmit and receive chains at the access point and user terminal are typically flat over most of the band of interest, the phase and gain differences of the transmit and receive chains can be characterized with a small number of subbands. Calibration can be performed for 4, 8, 16, 48, or some other number of subbands, which can be specified in the message sent to Start Calibration. Calibration can also be performed for pilot subbands. Calibration constants for subbands for which calibration is not explicitly performed can be computed by interpolation between calibrated subbands. For clarity, the following assumes that calibration is performed for all data subbands.

For calibration, the access point allocates to the terminator a short timeout in the RCH to send a sufficiently long uplink MIMO pilot plus a message. The length of the uplink MIMO pilot may depend on of the number of subbands on which calibration is performed. As an example, 8 OFDM symbols may be sufficient if soybean calibration is performed for four and more subbands (for example, 20 OFDM symbols may be required for more subbands. The total transmit power is typically fixed so that if the MIKO pilot is transmitted over a small number of subbands then higher amounts of transmit power can be used for each of these subbands and the SNR for each subband is high. If the MIMO pilot is transmitted over a large number of subbands then smaller amounts of transmit power may be used for each subband and the SNR for each subband is worse. high enough, then more OFDM symbols can be sent to the MIMO pilot and integrated into the receiver to obtain a clearer total SNR for the subband.The following user terminal transmits a MIMO pilot via RC H, which is used by the access point to derive an estimate of the uplink effective channel response for each of the data subbands. Uplink channel response estimates are quantified, for example, into 12-bit complex values, with phase (!) And quadrature (Q) components, and sent to the user terminal. The user terminal also derives an estimate from. effective downlink channel response, Hdn (fc) f For each of the data subbands based on the downlink MIMO pilot sent via the BCH. When obtaining the effective uplink and downlink channel response estimates, Hih (A) and H „p (A), for all data subbands, the user terminal determines correction factors, £„ (*) < = èM, for each of the data subbands, which should be used by the access point and user terminal respectively. A correction vector k (fc) can be defined as including only the diagonal elements of Κ, ρ (Λ), and a correction vector klit (i) can be defined as including only the diagonal elements of L (*).

Correction factors can be derived in a number of ways, including through matrix mouse computation and MMSE computation. These two computation methods will be described in more detail below. Other computing methods may also be used and this falls within the scope of the invention. 1. Matrix Ratio Computation To determine the correction vectors k (it) and ku, (fc) given the effective downlink and uplink channel response estimates, HdI1 (A *) and Http (A), it is initially computed. a matrix C (k) of uV (x Nap) for each given subband, as follows: for fce K, Eq (28) Where the ratio is taken element by element. Each element of C (A) can therefore be computed by: e / = {1 -ΚΡ} ’Eq (29) Where hup ,; (i) is the IJ, j) -th and 1th (1 i ηna, as 1 unit} of H>). K, {*) o the (i, j) -th and 1 nth of H (h) (c) and c, rJ ik) is the {i,}} ès element of C ik}. The correction vector k (t) for the access point is therefore equal to the average of the normalized lines of C (A). Each line of C i) is first normalized by staggering each of the Nap elements in the line with the first and then in the line. Thus, sec ', v., (Ul is the first line of C [kj, so the normalized line çt (A) can be expressed by: Eq (30) The average of the normalized lines is therefore the sum of Nul normalized lines divided by Λ'Β, which can be expressed by: wake K, Eq (31) Due to normalization, the first element of M *) is the unit. The correction vector kM (ft) for the user terminal equals the inverse average of the normalized C columns (A5 - The jth Cfk column) is first normalized by scaling each element in the column to the yth. element of the vector k (í), which is denoted as Kip,., (λ). Thus, if £ (*) = [<;, _, (*) ... c.vw is the yth column of C i Ar; , so ai (k) normalized column “A> 'can be expressed by: Eq (32) The average of the inverse of the standardized 1 column is therefore the sum of the inverse of the normalized column Nap divided by Ntφ, which can be expressed by: > ara k £ fCt Eq (33) Em. whereas the inversion of the standard columns, M *) * is effected first and first. ^ v_! · !: 1: 1 h λ.-ompíitucài MM8F ;, the 'correction actors Kjk) and! £, „(£) s · ν- from the actual uplink and downlink channel response estimates iiiki (*) 'such that the mean square error {ΜΞΕ} between the downlink calibrated channel response and the uplink calibrated channel response is minimized. Such a condition can be expressed by: for k € K, Eq (34) 0 which can also be written as: Where (í) = K: i]) (A :) since Kap (A) is a diagonal malarity . Equation (34} is subject to the constraint that the leading element of ^ (i) is set equal to unity (ie, KiPrlX5 (^) - 1). Without such a restriction, the trivial solution would be obtained with all matrix elements K (*) and KW (A) set to zero. In equation (34), a matrix Y (k) is first obtained as Y (k) = Ka) t (i) Hdn (A) - Yeah, Kut (&). The square of the absolute va \ cr is given below for each of the V · Λ · entries of matrix Y (A). The mean squared error (or the squared error, since a division by Nun · Nul is omitted) is then equal to the sum of all Ar, „- Aw squared. The MMSE computation is performed for each sub bandwidth, to obtain the correction factors Kip (A) and KBl (fc) for such subband. KM SE computation for a subband will be described below. For simplicity, the subband index, k, is omitted in the following description Also for simplicity, the elements of the downlink channel response estimation Hd | l are denoted by (av), the elements of the uplink channel responsiveness element. H are denoted by {hv), the diagonal elements of the matrix K are denoted by {u,} and the diagonal elements of the matrix K. ^ are denoted by p,}, where i = {1 Ygp} ej = {1 ... Nui), the mean square error can be rewritten from equation (34) as follows: Eq (35) Again subject to the restriction w: - 1. 0 The mean squared mean error can be obtained by making the partial derivatives of equation (35) with reference to u and v and equaling the partial derivatives to zero. The results of such operations are the following sets of equations: Eq (36a) Eq (36b) In equation (36a), m = 1, so that there is no partial derivative for such a case and the index i dc 2 to Nop. The set of {Nap + Nm - 1) equations in the sets of equations (36a; and (36b) may be more conveniently expressed in matrix form, as follows: Eq (37) Where A matrix A includes ((/ ί + Nul - 1) lines, with the first Ναρ - 1 lines corresponding to Ναρ - 1 equations from the set of equations (36a; and the last / VB / lines corresponding to Nu, equations from the set of equations (36b). the first line of matrix A is generated from the set of equations (36a) with i = 2, the second line is generated with i ~ 3 and so on, K Nap-th line of matrix A is generated from the set of equations (36b) with j - 1 and so on, and the last line is generated with j - Nu., As shown above, the entries in matrix A and the entries in the vector * can be obtained from the inputs. parent streets H>) and H, (í).

The correction factors are included in the vector j ;, which can be obtained by: y = A_li. Eq (38) The results of the MMSE computation are the K and Km correction matrices that minimize the mean square error in the downlink and uplink calibrated channel responses, as shown in equation (34). Since the matrices K and Ku! Based on estimates of downlink and uplink channel response, Hdn and H ,, P, the quality of the correction matrices K and Klil; Therefore, it depends on the quality of the channel estimates H (I1, and ÉM |,.) The MIMO pilot can be averaged at the receiver to obtain more accurate estimates for || Λ and H.

The correction matrices, K and Iul, obtained based on MM SE computation are generally better than the correction matrices obtained based on matrix ratio computation. This is especially true when some of the channel gains are small and the measurement noise can greatly degrade channel gains. 3. Post-computation A pair of correction vectors, k (A) and km (A), can be determined for each of the data subbands. Since adjacent subbands will probably: * be correlated, computation can be simplified. As an example, computation may be performed for each nth subband rather than for each subband, where n may be determined by the expected response of the transmission / reception chains. If the calibration is performed for a number smaller than the totality of the pilot and data subbands, then the correction factors for the "uncalibrated" subbands may be obtained by questioning the correction factors obtained for the sub-bands. "calibrated" bands. Several other calibration schemes can also be used to give the 1: 3, the (k) and kul (A), for the access point and the user term 1 respectively. However, the scheme described above allows "compatible" color correc tion vectors as derivatives to the access point when calibration is performed by different user terminals.

After bypass, the user terminal sends the correction vectors M *) to all the data subbands back to the access point. If the access point has already been calibrated (for example, by other user terminals), then the current correction vectors are updated with the newly received correction vectors. Thus, if the access point uses correction vectors for transm it. go the pil o t c Μ. I HO from which user terminal determines new correction vectors £ 2 (Jt), then the updated correction vectors are the product of the current and new correction vectors, ie £ .pj (*) =! Lí> i (*) · Where multiplication is element by element. Correct veto rs s and k j (A) can then be used by the access point · until they are updated again.

The correction vectors apap, (*) and k, 1 |: i2 (A) can be derived from the same user terminal or different user terminals. In one embodiment, the updated correction vectors are defined as k t (A) ~ k, (A). k ^ A), where multiplication is from element to element. In another embodiment, the updated correction vectors may be redefined as kapJ (A} = k ,,,, ^). k ^ A), where α is a pure factor used to provide the weighted average) po: eg, 0 <α <1}. If the calibration updates are. infrequent, so «next η α.τ. ρ ;; rr: i have better performance. If updates st ·: t: · combs but noisy, then a tenor value for u: ι · α ·,; . aLuai Izados kw> W correction vetoes can then. nei used by the access point until they are updated again. The access point and user terminal use their respective correction vectors k4p (A) and k ^ A), with the corresponding matrices K, p (A) and K, (t (A), for k € K, to scale the modulation symbols before transmission, as described below: The calibrated dowrilink and uplink channels that the user terminal and access point observe are in equation (27) VII. and user terminal can be tuned to a TDD system after calibration has been performed to compensate for the difference in transmission / rejection chains.As mentioned above, the down] irsk channel response is H (dn (*) = Ha, (£) &. „, (*} · The uplink cane: calibrated response is 1 '£ E ° uplink spatial cessation A deco mp os I ç. Odeva 1 cr si ng υ 1 arda rri the channel response string, uplink calibration, can be expressed by: for ke K, Eq (39) Where: üap ik ) is a unit matrix çV (ip x A "%„) of Haip's left eigenvectors (Â'j; Σ {k) is a diagonal matrix [Νίψ x, VljC} of singular values of HfMp {k ''; and Vut ik) is a unit matrix (A „f x Nül) of R.up right-hand eigenvectors [k].

Lieutenant, the singular value decomposition of the response matrix ac of the down.Link channel calibrated, licdnik}, can be expressed by: for ke K. Eq (40) The matrices V * t (k) and ti ' l {i (k) s à otaxb is m miaize sdeautov left and right indices, respectively, of Htt | n [k \. As shown in equations 39) and (4C) and based on what has been described above, the left and right eigenvector arrays for a yk are a complex conjugate of the right and left eigenvector arrays, respectively, for the another link. The matrices YUí (OV *, (*), V ',, (ã) and V ”(*) are different forms of the matrix Viní £), and the matrices n„ (4 u; wn; f (*) «t ; (*) are also different forms of the UapíAi matrix.For simplicity, a reference to the matrices U; ip (A) · and VMt; k) in the following description may also refer to their various other forms. The arrays jUap, jk) and VU | (A '; are used by the access point and the user terminal respectively for spatial processing and are thus denoted by their subscribed indexes. The eigenvectors are also often denoted as "directing" vectors. ". The user terminal can? Estimate the calibrated channel response of the downlink cox based on the MIMO pilot sent by the access point. The user terminal can then perform the oscillation 1. cr si ngu 1 sta tive sta downlink calibrated channel response rate for k and K, to force air L zdiagone 1 m and the matrix V * t (i) of the left H e dn (A) eigenvectors Such singular value decomposition can be given by H ^ (A) - VB | (A) Σ (Α) ύip (A), where the circumlex; "Λ") above each matrix indicates that it is an estimate of the actual matrix.

Similarly, the access point can estimate uplink calibrated channel response based on a MIMO pilot sent by the user terminal. The access point can then perform the singular value decomposition for the uplink Ha ,,, (A) calibrated channel response estimate for k € K to obtain the diagonal matrix t (k) and the matrix Üip ( A) of the left H ubl (A} auto ve cts of HC „P (A}. Such a decomposition of the syn value 1 can be given by 'Jma ir.atriz K.; r \ k) of i. . · Ν „χ Λ '„, ι can be defined by: for ke K. Eq (41) While active, the user terminal maintains a current estimate of the downl ink fttdn (A) calibrated channel and the Vlrt arrays. (i) of the left H Cih vectors, (A), which are used to update the matrix E-jt ·; *) - the user terminal uses the matrix (A) for spatial processing for the targeting fears of For the spatial multiplexing mode, the transmission vector xuu [£) for each subband can be expressed by: for ke K, Eq (42) Where: s ;; p {k) is a data vector with up to Ns symbol olos a s and r r a n sm.i had · a r r v e s A '„y autonomous sub-barida k; F -,; t ik) replaces V; k) in equation (15} and the signal scrambling by Çi i.k) to obtain channel inversion and emitted in equation (42) for greater simplicity; and [k) is the transmission vector for uplink for the subwoof k. At the point of access, the received vector rap (/ t) for upiink transmission can be expressed by:, for k ε K * Eq (43) Where: r..P ', k) is the vector received for the u ρ 1 inkk subband; and nuP [k) is the additive Gaussian white noise (AWGN) for the subband k, Equation f> 13 J uses the following relationships: and Cerro shown in equation ii), at the access point, uplink transmission received is transformed by li (à) Ê (í), which is the matrix Üai, ik) of left H (A) eigenvectors scaled by the diagonal matrix I (à) of singular values. User termination transmits a directed reference through uplink using the FuL matrix \ k). The directed reference is a pilot transmission via a broadband autode using either beam steering or beam forming, and will be described in more detail below. In the access point, the received directional reference received from uplink (in the absence of noise) The access point can therefore obtain an estimate of the unit matrix lü (jt) and the diagonal matrix Σ (&) based on the directed reference sent by the user terminal. can be used to estimate the unitary and diagonal matrices.

In one embodiment, to obtain an estimate of £ (i), the received vector r, lki for the reference directed to the subband k of the broadband sutomode m is initial m m 1 1 i. ρ 11 c a d o p e 1 o conjugate c omp 1 e x o ri e a pilot symbol OFDM, // (Ag), sent for the directed reference. The generation of the directed reference and the OFDM pilot symbol will be described in detail below. The result is then integrated into multiple prescriptive directional reference symbols for each bandwidth automaton to obtain a summary. of ü- ik) f! 1 (kj, qυe is a stepped left eigenvector of H (i) for a broadband mode m. Since c eigenvectors have unit power, the singular values (or a ~ [k) i in £ (&) can be estimated based on the power received from the directed reference, which can be measured for each subband of each broadband auto mode.

In another embodiment, an MKSE technique is used to obtain an estimate of end (A) based on the received vector (k) for the directed reference. The directed reference may be sent to a broadband autode at any given symbol period and may in turn be used to obtain an estimate of an eigenvector for each subband of such a broadband autoode. From this rate, the receiver is able to obtain an estimate of an eigenvector in a unit matrix for any given symbol period. Given that estimates of multiple eigenvectors for the unit matrix due to noise and other sources of degradation along the L1 path do not, the estimated eigenvectors for the. unitary matrix proves vo1men t and are not rtegonais. If the estimated vectors are then used for spatial processing of the data transmission on the other link, then any orthogonality errors in such estimated eigenvectors will vary. result in oross-taik between the autodes, which may degrade performance.

In one embodiment, the estimated eigenvectors for each unit matrix are forced to be octagonal to each other. Orthogonalization of the eigenvectors can be obtained using various techniques such as QR factorization, minimum quadratic error computation, polar decomposition, and so on. . Ot £ QR allocation decomposes an M‘T matrix (with non-octagonal columns) into an orthogonul matrix and an upper triangular matrix Rr. ·. The matrix Qr makes an octagonal base for the columns of M ‘. The non-ionic elements of R? d o o o o o o mp r 1 mie n t o d o c compone n t e s d a r Mr columns in the directions of the respective h matrix columns can be used for spatial processing in the downiink. The jQF and R? can be used to derive an extended matched filter matrix for upiínk. QR factorization can be performed by several methods, including a Gra.T.-Schmidt procedure, a Househoider transformation, and so on.

Other techniques for estimating unary and diagonal matrices based on directed reference can also be used and this falls within the scope of the invention. The harassment point can therefore estimate Cap [k) and Z (k) based on the directed reference sent by the user terminal, without having to perform the decomposition of sir.guiar value over Hαφ (k).

A normalized matched filter Map (k) matrix for the u uplink transmission from the user terminal can be expressed by: Bq (44) The fi le r: act matched the access option for the uplink access can then be expressed by :, Eq (45) Where s, r „(fc) is an estimate of the vector of modulation symbols su /, (k) transmitted by the user terminal to the multipath mode *, To dc beam steering mode , only one line from the matrix MTlk} is used to provide a j. esteem r; j <- slrr.brl 's (A) for autodod u s a dc for *; r r. srs. ·; ad a d-ics: s,. P> *. -.::+1. . '1 . ! v. IllI - ill! ’'Already 4K, ·. : · T: · o · · and · ·; · ·. a matrix Fap (k) of Λ ': x S,! r. r 11 a: * -ss.r.ar. -, ·. . fa I matrix can be expressed by: sara kí. Eq (46) A ma t r i. z d e c o rc e r K (A) is derived from the user and sent back to the access point during calibration. The matrix JU ^ ,; À ') can be obtained from, based on the direct reference sent via upimk by the user terminal. read the mean of multi-space exploration, the transmission vector * dr. (k) for the tiownlink for each data subbase shall be expressed by: for k and K 'Eq (47) Where x: lr. (Λ) è the transmission vector, sdr, (k) è the data vector for the downlink and the signal scaling by G (k) to obtain the channel inversion is again omitted for most of the imp11c id a de.

At the user terminal, the received vector r (m (icj for the transfer is dod ο κ n lir.kpo to be expressed by; for k tí K. Bq (4B) As shown in equation (46), in end-user transmission, the received downlink transmission is transformed by y_m (k) Σ (*), which is the left eigenvector matrix Vm (A) of ca tin (A) and caionadaptrate zd i aqone 1 Σ (k) dev singular values.

Urr. The standard matched filter matrix Mut. í k} for downlink transmission from the access point can be expressed by: for k and K. Eq (49) The diagonal matrix Σ (ί) and the VM matrix (*) of a u to ve t. Left-hand ones can be derived by the user terminal by performing single-value decomposition on the downlink calibrated channel response estimate (as described above). A f 1 't pod, married at the user terminal for The downlink transmission can then be expressed by; . Eq (50) 3. Spatial Processing rio______Access Point and Endpoint of its Devious channel to the system. TDD and calibration, spatial processing at the access point and at the user end can be simplified, h Table 32 summarizes the spatial processing at the access point and at the end of the user. of data.

Table 32 ·. pr: · - '· or: i> - :. t ·. ,: 1 for data reception is turr.r-cr n.ur.cuc r -: r. i · "'married filtering.

Due to the reciprocal channel, Vw (a) is both the right eigenvector matrix of Ht.Kji (Â ') (for transmission) and left eigenvectors to the UCl.,. (A) (for reception) to the terminal. user. Similarly, (k) is both the matrix and the highest rights of 1 | cd! 1 (A) (for transmission) and the left H e? P (»(for reception) eigenvectors for the decomposition point). The singular value shall only be made by the user terminal for the estimated response of the channel: calibrated from the downlink Μ & ΐη (to get \ _,. r (^) and X | A '). ü access point may derive Juápoào and Χ (Λ) as, based on the directed reference, sends it to the end user and does not need to perform single-value decomposition on the channel response estimate (ur. N. <Ht! L5, \ k). The access point and the user termini may have different versions of the ma (i) due to the clients using the access point and the user terminus to derive Σ (Α).

In addition, the matrix Ü AO; The access point based on the directed reference is typically different from that of the user terminal malice Ι ^ ιρ (k) using singular value decomposition. For simplicity, such differences are not shown in the derivation. above. ··! . Leave Direction For certain channel conditions it is best to transmit data over and only one broadband car - typically the best, or main, broadband car. This may be the case if the SNRs received for all other broadband autortodes are weak enough that better performance is obtained by using all the available transmit power on the main broadband automode. Data transmission in a broadband auto mode may be effected using beam forming or beam steering. For beam formation, the modulation symbols are spatially processed with the νω1 (λ) or ü S (A) auto vectors, for k and K, for the main broadband auto list this is, the first column of Vw (k) or U {k), after ordering,>. For beam replication, the beam symbols are spatially processed with a set of "standard" (or "saturated") eigenvectors (1 vw (A) or u (A), for ke K for the main broadband automode. For clarity, beam steering will be described below for upli nk.

For the upiink, the elements of each autovlor vw _ [(k), for k and K, for the main width can have different magnitudes. Thus, the preconditioned symbols for each subband, which are obtained by multiplying the modulation symbol for subband k by the eigenvector elements ν „η <*> for subband k, can. then have different magnitudes. Consequently, antenna transmission vectors, each of which includes preconditioned symbols for all data subbands for a given transmitting antenna, may have different magnitudes. If the transmitting power for each transmitting antenna is limited (eg due to limitations of the power amplifiers) then the beam formation may not have the full power available to the transmitter. For each antenna, the beam steering uses only the phase information from the eigenvectors, (jfc), for k and K, for the main broadband automode and normalizes each eigenvector such that all elements in the eigenvector have equal nagri i tuties. The normalized eigenvector v, i; (fr) for subband k may be expressed by: Eq (51) Where: A is a constant (eg h =), and 6j ij is the phase of the subband. band k of transmitting antenna i, which is given by: Eq (52) As shown in equation (o2;), the phase dc of each element in vector v1 ([wc obtained from the corresponding element of aulovctor v „,, (£) (that is, Θ, (k) is obtained from virtl, (*) where 5. fu rec: n r. to go. e: tn -.ie Beam no Ijpli nk The cspacia 1 processing by the end 1 uplínk beam routing user can be expressed by: sara. keK, Eq (53) Where: s i k} is the symbol i p d o ci u 1 action a s e r 1.1 a 1i s ro i t i o through the subband k; and M *) is the transmission vetcr for the subband k 0 <"1" 1 Cl 1X8 C 1 Ο Π ΓΠ.8 Π. t Ui 8 I O .1 X 8.

As shown in equation (53), the Λ? „, Elements of the normalized steering vector νΒ) (Α) for each subband have equal magnitude but possibly different phases, so beam steering generates a vector of x (A) transmission for each subband, with cs. \ rul elements of x (i) having the same magnitude and possibly different phases. The trans rn iss â: - dsup 1 i nk I received from η the point of access for beam directing can be expressed by:, for k and K, Eq (54) Where r „r (1) 6 the vector receivedUc for oup 1 in k. a b a b u - band k for beam steering.

A matched filter line vector m <rr (A) for a. upl iru <transmission using beam steering can be expressed by: wra jfc and K. Eq (55) The matched filter vector m (A) can be obtained as described below. The process: nen: the spatial (or matched filtering; rc access point for the upiink transmission received with iex direction can be expressed per; for k £ K, Eq (56) Where: (ie, Λ (* ) is the internal product of m (Λ) by its conjugate transpose); sm (Λ) is an estimation of the modulation symbol Sapik) traced by the user terminal atro. · "és do upiitk; e η, ψ ik) is the post-reached noise 6. Downlink Beam Recioting Spatial processing by the downlink beam directional access point can be expressed by: for k and K, Eq (57) Where 0, ( Ar} is the normalized eigenvector for the subband k, the qt “'d: ·' · / · ': -u; v: -.-. The eigenvector u'„,, (/ :), for the d . i · ·; -.min. m:; rijt · .; .1, similar to that of o: m.; ivs "t;”. t 11 \ up tí. Ut married filter line vector mw { £) for the next miss I give η I i 11 kusandodirecína me n. f; The beam may be expressed by: »ra kf = K, Eq (58) 0 spatialprocess 1 [or Married user interface for downlink transmission nrá: tda may be expressed by: for k € K, Eq {59} Where (this is, (A) is the internal product m, (A) by its conjugate transpose). 7 Proceed saraent o Es p ciai with I. Canal Inversion. For uplink, the transmission vector x.jp (k) for spatial multiplexing mode can be derived by terrair. a 1 of us u a r i o se g u 1 n t. and form: for ke K, Eq (60) Where G (Aj is a diagonal gain matrix for the channel inversion described above, equation (60) is similar to the equation (wool; · except that Kw (A) VltJ (A) is used in the image of V k) The elements of K af (k) V lrt (A) are provided to multipliers 352 within beamformers 950 in Figure 93. .

For uplink, the transmission vector x {k) for dc beam steering mode can be derived by the user terminal as follows: for ke K, Eq (61) Where \\. (K) is a vector with four elements having equal magnitude but phases obtained based on the action: vector vw, (A) for the main autornornate, the vector v ,, ({A) can be derived similarly to the one presented in the equations (16) and :) 17). Gain # (a) obtains the channel irons and can be derived from the form i.'ar bi.iila presented above in equations (18} to (20; except that ”is used and: n instead of equation Ps and I and mtesdev ιφ (*) are provided with multipage 1052 within the beam-steering unit? 1050 in Figure 10B.? Araodow π .11 n k., The transmission vectors are xdn (k) for spatial complexion mode can be derived by the access point as follows: for jte K. Eq (62) Equation '62; is similar to equation (15) except that qf Κ ,, (Α ·) ύ, .. (Α) is used in place of V (k) The elements of the multipliers 552 nc inside the beamformers 950 in Figure 9B.

For a dow η 1 ink, the transmission rate x A {k) for the fear of directional steering can be derived by the access bridge as follows: for k € K, Eq (63) Where M *) is a vector with four elements having equal magnitude but phases obtained with base rs :: aouvector 0 ,,,,,, (1) for the principal automaton. The gain g (k) obtains the channel inversion and can be derived similarly to that given above in equations (18) to: .2 ()}, except that it is used in place of equation (20). The elements of u,; r (k) are provided to an interior 1052 rcc multiplier of the beam steering unit 1050 in Figure 10B. VIII. Pilot Structure A pilot structure is provided with the MIKO d LAN system to allow access points and user terminals to acquire timer. Table 33 lists four pilot types and their short description for an exemplary pilot structure. Fewer types, different and / or additional pilot tops can also be used for the pilot structure.

Table 33 - Pilot Types Reference d: rneiorsadu and directed pilot are equ suits; va 1 '' rues.

In one embodiment, the pilot structure includes (1) for the downlink - a signaling pilot, a MIMO pilot, a directed reference, and a carrier pilot transmitted by the access point o; 2j paru o uplir.k a pilot KLMd, a directed reference o „o. carrier pidote transmitted by user terminal skins. The downlink signaling pilot and the MIMO pilot are sent via the BCH; tu1 as shown in Figure 5A) in each TDD frame. The beacon pilot can be used by the terms of its u ri ry for th e t u n e s and the frequency and Doppler estimation. The MIMO pilot can be used for the first time. more than u s a r i o p ara ·; 1> has an estimate of the dowr.i ir.k, ti MIMO channel; detecting uplir.k transmission driving vectors (if beam steering or spatial multi-duplexing mode is supported; and i3) deriving a matched filter for transmitting d o w η I i n k, The reference d i r e c ί. the r. Any downlink can also be used by a specified user terminal for channel estimation. "a uplink directed reference is transmitted by each active user terminal that supports beam steering mode or spatial reflection and can be used by the access point to i) derive the driving vectors for downlink transmission and { 2) derive a matched filter for uplink transmission.In general / the directed reference is only sent to / by user terminals that support the beam redirection and / or spatial connection modules, h reference sent furcior.a regardless of whether it is properly directed or (for example, due to a bad channel estimate), ie, the reference becomes orlogonal on a basis by a transmitting antenna that the di recior.amento is diagonal.

If a user terminal is calibrated then it can transmit a directed reference through the main auto through RACH using the vector Ka, (A) vWJ, {*), for k € Kf where is the column of Vs ( (ft ·) for the main car If the user terminal is not calibrated, it can erroneously transmit a pilot through RACH using a ver.cr for ke Ad 11 vector v (*) for each subband includes Null coefie i . De i or ο ο ο ο ο ο ο ο ο ο at at at at at c c c c c c c c c c ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie ie Alt podem Alt podem podem podem podem podem podem podem podem podem podem podem podem ·· - · a psycho-random procedure. Since only the relative phases between the targeting coefficients matter, the phase of the first targeting coefficient can be set to mere {i.e. 0; ik; = D). The phases of the other steering coherencies may change for each access attempt, so that all 360 ° is covered by each direction coefficient at 360 ° / NO intervals, where Ne is The perturbation of the phases of the direction vetou elements in each RACU attempt, when using RACH in the beam steering squeegee prior to calibration, is such that the user terminal does not use it. urr, wrong recirculation vector for all access attempts. A MIMO pilot can be sent to / by user terminals that do not have steering modes that do not have a spacefeed and / or multiple space. The access point has no channel knowledge for any user terminal until the user terminal communicates directly with the r point. cesso. When a user terminal wishes to transmit damage, he or she first estimates the channel based on the pile: the MIMO transmitted through the point of access. The following terminal sends the directed reference in the preamble lo RARH when it attempts to access the system. The access point uses the RACH preamble reference for ninai detection and channel estimation.

Once the user terminator has received the same access to the system and received FCH / RCHs granted by the access point, the user terminal sends a reference (for example, a pi 1 cr .: · MIMO} at the beginning of each RCH PDU it transmits If the user terminal is using the divem: _daae mode, then the reference is sent via Fu „n without directing. In beam-beam mode or spatial multiplexing mode, then a reference is routed through the RCH to allow the access port to determine the main receiver (for beam-mode) or the set of four eigenvectors (for spatial multi-mode mode) for each of the 48 data subframes .. The directed reference allows the access point to improve its channel estimate and track the channel. lotto Si na I za do r D o w η 1 i n k The dlownlink signaling pilot is included in the first part of 3CH (as shown in Figure 5A! and 1.transmitted in each TDD frame. The signaling pilot mclu: a specific ΟΡΠΜ symbol (denoted as "B") which is transmitted from each of the four antc in the access point. The same R OFdM symbol is transmitted twice in the duration of? Symbols for the pile to flag.

In a specific embodiment, the B OFDM symbol comprises a set of 12. BPSK modulation symbols, b (k), for 12 specific subbands, which is presented in Table 31. For the sine pilot mode shown in Table 3, the OFDM symbol B comprises (1) a BPSK modulation symbol (1 + j) for the -24, -16, -4 subbands, 12, 16, 20 and 24, (2) a BPSK modulation symbol. (1 + j) pairs the "20, -12, -6, 4 and 8 subbands, and (3) zero signal values for the remaining 52 subbands.The OFDM B symbol is specifically designed to facilitate the acquisition of timing and frequency by the user terminals. However, other OFDM symbols can also be used for the signaled pilot and this 2. MIMO Downlink The downlink MIMO pilot is included in the second part of the 3CH (as shown in Figure 5A) and is also transmitted in each TDD frame. includes a specific OF DM symbol (denoted as "P") which is transmitted from each of the four antennas on the access point. ito times in the duration of 8 symbols for the pilot MIMO. However, the eight P OFDM symbols for each antenna are "covered" with a different 4-chip Waish sequence assigned to such antenna. Coverage is a process whereby a given pilot or data symbol (or a color of L pilot / data symbols of the same value) to be transmitted is multiplied by all L chi ps of an orthogonal L chip sequence. The following is a complementary process whereby the received symbols are multiplied by the L chips of the same orthogonal sequence of L chips to obtain the systemat 1 osdost: open, which are the following: a set to obtain an estimate of the pilot symbol / ransmi read data Coverage obtains orthogonality between the pilot transmissions from the transmitting antennas and allows the user terminals to distinguish individual transmitting antennas. Coverage can be achieved by correcting Walsh sequences or other orthogonal sequences.

In a specific embodiment, the OFDM P symbol comprises a set of 52 QP3K modulation symbols, p (k), for the 48 data subbands and 4 pilot subbands, which is presented in Table 34. zero signals are transmitted over the remaining 12 subbands. The OFDM P symbol comprises a unique 52 pPSra of QPSK modulation symbols which is designed to facilitate channel estimation by user terminals. Such unique word is also selected to minimize peak to average variation in pilot, transmitted MIMO. This in turn can reduce the amount of distortion and nonlinearity generated by the user terminal circuits, which can result in better accuracy for channel estimation. However, other OFDM symbols may also be used for the MI MC pilot and this falls within the scope of the invention.

In one embodiment, the four antennas at point 3 and 3 echo sequence W 1s h of four W and c; = 1111, W2 1010, W3 = 1100, and W4 = 1001 for the MIMO pilot. For a given Walsh sequence, a value of "I" indicates a symbol P 0 F DM ccra nsmit id and a value of "0" indicates that a -P OFDM symbol is transmitted thereof, ie each of the 52 symbols P modulation is inverted. Table 35 lists the OFDM symbols to be transmitted from each of the four antennas at the access point to the MIMO pilot signaling pilot. The symbols Be? OFDM are as described above.

Table 35 - Top Signal and MIMO Pilots The MIMO pilot can be used by the user terminal to estimate the downlink channel response. In particular, to retrieve the pilot sent from the access point antenna i and received by the user terminal antenna j, the pilot received by the terminal antenna j is first multiplied by the Walsh sequence assigned to the antenna / access point. . The eight GFDM symbols discovered for all eight periods of symbiosis. 1 osparaopi 1 ot ο Μ MG are accumulated, where accumulation is performed individually for each of the 32 subbands used for carry the MIMO pilot. The result of the accumulation is h (At (*), for k - ± {1, 26}, which is an estimate of the antenna-calibrated downlink channel response / access point for antenna j from the user terminal to the 32 data and pilot subbands The same pilot processing can be performed by the access point to retrieve the pilot from each access point antenna on each user terminal antenna The pilot transmitted from each antenna of the access point can be recovered by uncovering the assigned Walsh sequence for such an antenna. Pilot processing provides A '* ,, · Nul values for each of the 52 subbases, where Νίψ denotes the um antennas η op op r all access and Air denotes the number of antennas on the user terminal.The N i \\ values for each subband are the elements of dowr.lirk ca 1 ibr channel response estimation. H, W „(A) for such su bb a π da, 0 pi 1 ot οI O can also be t rans uplink m a t t e r a v e s by the user terminal for calibration and diversity mode. The same processing as described above for the user terminal to retrieve the MIMO pilot sent by the access point may also be performed by the access point to retrieve the KTMO pilot sent by the user terminate 1. 3. Directed Reference A directional reference can be transferred on the preamble portion of a PDü RACH (as shown in Figure SC) or an RCH PDU (as shown in figures SE and SG) by each terminal. of active user. A directed relay may also be transmitted in the preamble portion of a FC.H PDü (as shown in Figures SK and 5E) by the access point to an active user terminal. THE . Ref er onc ia Pirec icnj.J ΐ Ra r _Mu 11 i p 'ο κ açà of spp hi: ί 1 h reference d: n ·: i> _ r π in> .i.xpr': i: nd> - un. CFDK specific uplift 1.por; e> v mr j, <ι · »· οθ 'n imbol <·. E 'll * "Mi used for the MÍKO pilot) which is transmitted from all transmitting antennas on the user terminal (for uplink) or at the access point (for downiinki. However, the P QFPK symbol for each symbol period is processed spatially (That is, formed into a beam) with a steering vector not paired with an autode. The first symbol of the directed reference transmitted by the user terminus in the RACH preamble can be expressed by: par & k £ K \ Eq <64) Where:% {k) is the transmission vector for subband k;

Kaí (A) is the correction matrix for subband k for user termini; »I) A)) v v e,,,,,,,,,,, para para principal principal principal principal principal principal principal principal principal principal principal principal principal principal principal principal principal for the main broadband car sub-band; P ; (k) the symbol of pi 1 ot. the pa. the sub-faa r.üa k; c A '' = {-32 31J is the index set for all 64 subbands. The vectorx (k} in includes four transmission symbols for each value of k, which must be transmitted from the four antennas on the user terminal. The steering vector vltli (A) is the first column of the matrix V ui. (k) of right eigenvectors of the calibrated uplink channel response estimate H (*), where r vu,, (a) is the ith column of Vm (k) .The above described assumes that cs W !!; .res singular in Σ (Α) and the columns of VM (i) are! · .. id · .: t *>; ic 1 :: η: described 0 the second symbol of the directed reference transmitted by the user in the RACH preamble includes the data rate indicator (DRI) for the RACH PDU 0 CRI indicates the rate used for the RACH message sent in the RACH PDU 0 DRI is embedded in the second DRI mapping driven reference symbol for a specific QPSK symbol $ ari / as shown in Table 15. The .vdIi symbol is then multiplied by the pilot symbol p \ k) before performing r the spatial processing. The second symbol of the RACH-directed reference can be e r e x p r and s o p o r: mkeK '. Eq (65) As shown in equations (64: 1 and (6b)), only the autcvxlor vi (J, (£) for the main automode is used for the RACH directed reference).

A directed reference symbol transmitted p e i m t e r m i n (1 e u su r e n e · p r e ml ml); 11 ode RC Η can be expressed by: parafcer, Eq (66) Where: Sr,: n (bJ is the transmission vector for the subband π dak of the broadband automode m; the mu (k) is the targeting vector for the subbandakdoau tomo dodebanda 1 argam (that is, m- is itself in the joint of V m, (k)). ütti simbo 1 or <: rn: cron no: -0: (-: 1. r.sds t * fO.sr.ii: u by the access point ro yr ·. '-Vr ;. d. „b I- '"v, ο .. ·! - --- 1 ---: 00 ..- g: -r:, for fte Kf, Eq (67) Where:;, s>, - dA ) is the transmission vector for subband k of the broadband automode m; K ,,,, (A) is the correction matrix for subband k for the access point, and ü 'm (* ) i the steering vector tiara the subband k of the auto dc band ia irrigates m The reciprocating vector u (,,) is the same column of the eigenvector matrix li (,,). down] ir.k Hiifii (&), where:: The directed reference can be transmitted in various ways.With one mode, one or more autoveters are used for the forwarded reference. each TDD frame is dependent on the length of the directed reference, which is indicated by the preamble type fields FCH / RCH in the information element ac FCCH, Table 36 lists the automobiles. used for the preamble to the FCH and RCH for various preamble sizes for an exemplary design.

Table 36 As shown in Table 36, the directed reference is transmitted to all four autodes u and n t: r o c u e rrt u r. i c o q u a t T D D q u a n d o n t h o r r e r r, b u 1 is four or eight OFDM symbols. The directed reference transmitted by the user terminal to the nth OFDM symbol r: the preamble to kCH can be expressed by: e rc = fl, ..., LL Eq (68) Where I is the preamble size , that is, L - 4 for type 2 and L = 8 for type 3.

Similarly, the reference given in the 11th paragraph by the access point for the nth symbol 1 c CFDΜ η the preamble to a FC Η can be expressed as: for k g Kr and n - LJ. Eq (69) As shown in equations (68) and (69), the four warms are cycled in each 4-symbol period by the operation \ n mod 4) for the di- rationation vector. This scheme can be used if the channel changes faster and / or during the early part of a connection when a good connection is a good one and should be the right connection of the system.

In another embodiment, the reference will direct it to one. broadband auto mode for each TDD frame. The reference directed to four broadband autodes can go through four TDD frames. As an excmp), the displacement vectors v £ „,, (*) \ M, (A) t 'v„,, (£) can be used for the first, second, third and fourth TDD frames, respectively. I see. t: e, by the user terminal. The targeting vector may be specific to the 1.5 B s of the frame counter value in the 3CH message. This scheme allows the use of a shorter preamble part in the PDU, but may require a longer period of time to obtain a good estimate of the channel.

For both embodiments described above, the referenced reference may be transmitted across all autodes that may be used for transmission of data, even though less than four autodes are currently used (for example, because unused autodes are weak). and were discarded by the "water fill"). Transmitting the referenced reference through a currently unused autode allows the receiver to determine when the autode improves sufficiently to be selected for a c. read it ? eforõιx f i a _Di r »1ci rxna_ria_ Father a_ 1) i roc 1 onamerc r. AD 7 i For beam steering mode, the spatial processing on the transmission side is performed u η n n ü n co n ma ma ma z z a a a a a a a a a a a a a a. General transfer function with a normalized eigenvector 6 d: f o r g n t e d a n j n efer n e c e r a n c e s. 1 with a non-standardized eigenvector (i.e., a targeted reference using the standard self-propelled cor- nel for all subbands can be sent by the transmitter and used by roceprnr to der: '/ sr the married filter vectors for such subbands for beam steering mode.

For uplínk, the reference directed to οίνο o. beam direction c 'may be expressed by: for k £ K. Eq (™) At the point of harassment, the directed reference of uplínk from r e c e p ection to ο · d o d o r e c i o m e n e d e f: x c p o «d e s r expressed by:, for k and K. Eq (7I) To obtain the matched filter line vector m, r (&) for beam-directed uplínk transmission, the vector received ra „, r (i) for the directed reference is first multiplied by / > * (*). The prescribed G is then integrated over multiple directed reference symbols received to form an estimate of. The vector m 1, (£) is then the conjugate transpose of such an estimate.

While operating in beam steering mode, the user terminal may transmit multiple directed reference symbols, for example, one or more signals. o s us a n d o o u t o v e t o r r η r ma 1 i 2 a d o Ijkh u m o i s symbols using the auto vector i · ^, (k) for the main broadband auto mode and possibly one or more symbols using the autosupers for the other broadband major. Directed reference symbols wanted with v. (A) can be used by the access point to derive the married iliter vector m, 9, (A). The directed reference symbols c: erad os with yw, (a) may be used to obtain u, (A), which may then be used to derive the normalized autovector g (A) which is used for downlink beam routing. The directed reference symbols generated with the eigenvectors vut, (k) through ys, Λ. (k) for the other autodnodes request to be used by the access point to get wu ,,, (A) a v v (k) and s v s ingsigners c u rs for the autodes. Such information may then be used by the access point to determine the use of spatial telexexing mode or beam steering mode for data transmission.

For dowr.lír.k, the user terminal can derive the matched filter vector for the roughness of a and c 1 c n a m e n e t e f e i c c f f c e s and in t t m m t. i v d e r e s μ o s downlink calibrated channel. Ht, & (A). In particular, the user terminal has ΰ, (A) from the singular decay decomposition of ή ^ ίΛ (Α) and asks to derive the r m a 1 i? a d o M *). 0 end 1 user can then multiply | t ¥, (A) by H „,„ {*) to get Hcdn (A) uap (k) and can then derive mM (A) based on Hcdn (á) u (A) „Ai te en ivamonte, a directed reference may be sent by the access point using the normalized autovefor u (A) and such directed reference may be processed by the user terminal in the manner described above to obtain mjk). i. Carrier Pilot - Uplink The OFDK subband structure described herein has four pilot subbands with indices of ...... 21, -7, 7 and 21. In one embodiment, a carrier pilot is transmitted over the Four pilot subbands in all OFDM symbols that are not part of a preamble, the carrier pilot can be used by the receiver to track phase due to variations in both: ι '' move as from receiver. T stc can provide a better way of demodulating data. The carrier pilot comprises four pilot sequences, (- ι)), Pa ín), Pain], and Plft (n), which are transmitted only through the four pilot subbands. Pilot sequences can be defined by;

Eq (72) Where n is an Index for. the OFDM symbol period.

Pilot sequences can be defined based on various data sequences. In one embodiment, the pilot sequence / t-, (n) is generated based on a polynomial Gix) - .ν '- .ν' * ·· x, where the initial state is set all to one and output bits are mapped to signal values as follows; 1 uó -1 and 0 - => 1. Λ sequence of pi Icto Pciín), for. n {L, 2, ..., 127 j, may then be expressed by;

The values of "1" and "-i" in the Pc -, (n) pilot sequence may be r.apeacics for pilot symphons using a particular iT: odu scheme. As an example, using BPSK, an "I" can be mapped to 1 + / and a "-1," can be mapped to ·· (1 + /), if there are more than 12? OFDM symbols, so the pilot sequence can be repeated so that l \ -i (n) = Λ.-: (n mod 12 ') to n> 127. have a radius, the four sequences of piioo are adjusted for each transport channel. Thus, in the downline, the pilot sequences are reset to the first 0 F DM of the BC message, then will be reset to the first OFDM symbol of the FCCB message and reset to the first OFDM symbol sent. through the FCK. Hey. In another embodiment, the pilot sequences are readjusted at the beginning of each TDD frame and repeated as often as necessary. For such an embodiment, the pilot sequences may be held during the preamble portions of the BCH and FCH. For fear of diversity, the four pilot sequences are mapped to four subband / antenna pairs. a 1 oa n o o o o o o n e t in Ta b she 29. E mparticu 1 ar, Pc: · n) is used for sub-lane -21 of antenna 1, Pc ^ («} c is used for sub-butt 7 of antenna 2, Pclin) is used for the subband? 3 and Pci ín) is used for antenna 1 subband 21. Each pilot sequence is then transmitted through the associated subband and antenna.

In spatial multi-multiplexing mode, the four pilot sequences are transmitted through the main headset of their respective sub-Pandas. Spatial processing for carrier pilot symbols is similar to that performed for modulation symbols as described above. In beam steering mode, the four pilot sequences are transmitted through these respective subbands using beam steering. The beam steering for the carrier pilot symbols is also similar to that for the relocation symbols.

A specific pilot structure has been described above for the MIMO WLAN system. Other pilot structures may also be used for the system and that is if the invention is the invention. IX. System Operation Figure I2A shows one. Specific embodiment is a state diagram 1200 for the operation of a user terminal. Such a state diagram includes four states - one state beginning 1 1210, one. idle state 1220, an access state 1.230 and a connected state 124 0. Each of the states 1210, 1220, 1230, and 1240 may be associated with multiple subsides (for simplicity, they are not shown in Figure 12A). N o and s are a d o i n; ciai, c terni n a 1 of u s u á. r i o c a p t a p t the frequency and setting of the system and obtain parameters from the system through BCK. In the initial state, the user terminal can perform the following functions: • System determination - The user terminal determines e; r, which carrier frequency to pick up itself. st ema. • Frequency acquisition / terrifying the user terminal picks up the signaling pilot and adjusts its frequency and timing accordingly. • Parameter acquisition - the user terminal [reaches Frq for the associated system parameters and :. access point from which. is r e c e h i d o s i r. a d e do w n link.

Upon completion of the functions required for the initial state, the user terminal goes into sleep state.

In idle state, the user terminal periodically monitors the BCH for updated system parameters, alerts and pages being sent via the downlink, and so on. No radio resources are allocated to the user terminal in such a state. In idle state, the user terminal can perform the following functions: • If a registration is authorized, the user terminal enters the access state with only one registration action. • If transmitter / receiver calibration is authorized, the user terminal enters the access state with a calibration request. • The user terminal monitors the BCH for pages and broadcast messages sent via FCH. • If the user terminal has data to send via uplink, it enters the access state with a resource request. • The user terminal performs such maintenance procedures to update system parameters and channel scan. • The user interface can be part of the energy-saving operation mode if such mode is supported by the user terminal.

If your radio station wants your radio from the access point for any task, it goes into the access state. As an example, the user terminal may switch to the access station in response to a DST alert or indicator sent in the BCH message, for registration or calibration request, or to add dedicated resources.

In the access state, the user terminal is in the process of accessing the system. The user terminal can send short messages and / or requests to FCH / RCH resources using RACH. The RACH operation will be described in more detail below. If c terminates user is released by the access point, it goes back to sleep state. If the user terminal has resources for the link and / or link, it will switch to the connected state.

In the connected state, the user terminal receives the E / CH / RCH resources, although it would not need to separate the TD D water. The user terminal can use the allocated resources or can be idle (but keeping the connection) η the connected state The end of the user remains unconnected state until released by the bridge of this connection and without any further delay in the specified period of waiting time {ti meou11, in which case it returns to the resting state. When in the resting, accessing, or connected state, the end of the session is 11 to the first one if it is turned off or if connection is lost Figure 12B shows a specific mode of a: connected state diagram 124 0. £ m r to 1 mode, the connected state includes three substations .... one substation c configuration (seiup) 1260, an open substation 12 '0, and an idle substation 1280. The user tenenai enters its stiffness when receding a In the configuration substate, the user is in the process You need to configure the connection and Arida is not searching for the data. The configuration of the connection may include the access point estimate, rate determination, service negotiation, and so on. When e n take only the c u n c e s in c ution, the user e r min i 1. just a timer for a specified amount of time. If the timer expires before it ends'. user leaves such a substate, it goes from vol fu to idle state. The user terminal switches to the open substate when completing the connection setup.

In the open substate, the user terminal and access point exchange data via downlink and / or upJir.k. While in the open substate, the user terminal monitors the BCH for system parameters and the alert / broadeast message indication. If one, the BCH message cannot be decoded correctly within a specified number of TDD frames, the user terminal will switch from vel to initial state. The user terminal also monitors the FCCH for channel assignments, rate control, RCH timing control, and power control information. The user terminal estimates the SNR received using the signaled pilot from the BCH and the preamble of the FCH and determines the maximum rate that can be sustained with con fi dence FC H, FCH and RCH assignments for the user terminal. for each TDD frame are given by the information elements in the P3U FCCH transmitted in the current (or possibly previous) TDD frame. The user terminal may not be designated for data transmission via the FCH and / or RCH to any given TDD frame. For each TDD frame which is not used for the first time, it does not receive an FCH PDU via down Link and does not typically receive it via up 1 ink.

For each TDD frame in which the user terminal is programmed, data transmissions via dcwnlink and / or upiink are performed using the rate, transmission mode, and offset dc.tempor i. RCH (for up.link) indicated in the FCCH assignments (that is, the FCCH information elements addressed to the user terminal). The user terminal receives, d c iti o d ula and d c c o d if ica as? D ü s FCH a e 1 e e n v i a d a s. User terminations also transmit RCH PDUs, which include the preamble and the FCH data rate indicator. The user terminal adjusts the rate used in the RCH. According to 3 IR, Rate Control Information and FCCH Assignment Information - If power control is being applied for uplink transmission, then the user terminal adjusts its transmit power based on the commands. control devices included in the FCCH assignment. Data exchange may be in bursts, in which case the user terminal may enter the idle substate whenever no data is being exchanged. The user terminal enters the idle substate when so ordered by the access point. If the access point does not assign the FCH cu RCH to the user terminal without a specified number of TDD frames, then the user terminal goes from coitus to idle state and retains its MAC ID.

In the idle substation, both uplink and dowr.link are idle. Data is not sent in either direction. However, the links are maintained with the targeted referral and tracking messages. In such a substation, the access percent periodically assigns idle PDUs to the user terminal through HCK and possibly through the FCH (not necessarily simultaneously! ·. The user terminal may be able to remain in the connected state indefinitely as long as the access point periodically assign idle PDUs through dc FCH and RCH to maintain the link.

While in idle substation, the user terminal monitors the BCK. If a BCH message is not correctly decoded within a specified number of TDD frames, the user terminal returns to its initial location. The user terminal also monitors the FCCH for channel assignments, rate control, RCH timing control, and power control information. The user terminal can also estimate the received SNR and determine the maximum rate supported by the FCH. The user interface transmits an idle DU through RCH when assigned and sets the RCH request bit in the idle PDU if it has data to send. If the access point does not assign an FCH or RCH to the user terminal within one. specified number of TDD squares, and i ϊ 15 o c t e r m i n i n i n u r i o r o v i t: a r e p o u s and retains its MAC 1D.

A timeout timer can be set to a particular value upon entering any of these three substations. Such a timer would then count down if there is no activity while in substation. while in the configuration substate, active or idle, the terminal will return to the rest state if the timer i. timeout period expires and to the initial state if the connection is dropped. When idle or idle, the terminal will also return to sleep if the connection is released.

Figures 12A and 12B show a specific embodiment of a state diagram that can be used for the user terminal. Several other state diagrams with. fewer states and substations, or additional and / or different states and substations may also be used for the system and this falls within the scope of the invention. X, Random Access Rn. In one embodiment, a random access scheme is employed to allow user terminals to access the MIMO WLAM system. In one embodiment, the random access scheme is based on a partitioned Al, OH A scheme, whereby one. The user terminal streams into a randomly selected R.ACH partition to try to get the system back. The user term may not view multiple transmissions through RACH until it is accessed. obtained or the maximum number of access attempts has been reached. Several parameters for each RACH transmission can be changed to improve the likelihood of success as described below. Figure 13 illustrates a timeline for RACH which is partitioned into RACH partitions. The number of RACH partitions available for use in each TDD frame and the duration of the RACH partition are configurable parameters. A maximum of 32 RACH partitions may be available for use on each TDD frame. The guard interval between the end of the last RACH partition and the beginning of the BCH PDU for the next TDD frame is also a configurable parameter. These three parameters for RACH can change from frame to frame and are indicated by the fields of RACH length, RACH partition size, and I r. t e r v al q u a r d d S A C H gives the message of B C H.

When a user terminal wants to access the C and τη a, ε i and firstly the relevant system parameters. The following user terminal sends a RACH PDU through RACH. Such a PDü RACH includes an RACH message that contains information necessary for the access point to process the access request from the user terminal.

As an example, the RACH message includes the MAC ID assigned to the user terminal that allows the access port to identify the user terminal. A MAC record (i) (ie, no specific MAC ID value) can be set to unregistered user terminals. In such a case, the long user terminal ID may be included in the RACH message payload field along with the registration MAC ID.

As described above, the RACH PDU can be transmitted at one of four data rates, which are 1 data in Table 15. The selected rate is embedded in the PDÜ RACH preamble (as shown in Figure 5C1. The RACH PDU has also a variable length of 1, 2, i or 8 OFDM symbols (also as listed in Table 15; which is indicated in the message length field of the RACH message.

To transmit the RACH PDU, the user terminal first determines the number of RACH partitions that can be used for transmission (that is, the number of "usable" RACH partitions). This determination is made based on (1) the number of RACH partitions available in the current TDD frame, {2} the duration of each RAC1 partition, (3) the guard interval, and {4} the length of the RACH PDU to be transmitted. The RACH PDU cannot extend beyond the end of the RACH segment of the TDD. Thus, if P DU R A C H still indicates that a RAZH partition plus guard interval, then such a PDU can be transmitted to one or more later available RACH partitions. The number of RACH partitions that can be used for transmitting the RACH PDU can be available from any RA C11 partitions based on the factors mentioned above. The RACH segment includes a guard interval, which is provided to prevent uplir.k transmission from the user terminals from interfering with the next BCH segment, which is a possibility for user terminals that do not compensate for their round trip delay. The following user terminal randomly selects one of the usable RACH partitions for t. ransmi t. i r the PDU RACH. User termination 1 then transmits the RACH PDU starting at the selected RACH partition. If the user terminal is aware of the * delay: d e e v α 1t> -1 p o r o ρ o n o n o o o r e s, then 5 e 1 e p e d compensate for such a delay by appropriate adjustment of its response.

When the access point receives a RACH HDU, it checks the RACH message received using the CRC included in the message. The access point discards the RACH message "when the CRC fails. If the CRC passes, the access point sets the RACH acknowledgment bit at 3CH in the subsequent TDD frame and transmits a RACH acknowledgment through the FCCH within 2 TDD frames. There may be a delay between setting the acknowledgment bit on the BCH and sending the acknowledgment through the FCCH, which can be used to compensate for the programming delay, and so on, for example if the access point is mor. Because of RACH, it can set the acknowledgment bit on the BCH and have a delayed time delay FC CH 0 The default setting bit prevents user terminations from trying the SNOW Unsuccessful user terminals try again quickly, except during busy RACH periods.

If the user terminal is registering, then it uses the registration MAC ID (eg 0x0001). The access point responds by sending a MAC ID assignment message via the FCH. All other types of RACH transmission include the user-assigned MAC terminal of the system. The access bridge explicitly acknowledges all RACH messages received by sending acknowledgments through the FCCH using the MAC ID assigned to the user terminal.

After the user terminal submits the RACH PDU, it monitors the BCH and FCCH to determine whether or not its RACH PDU has been received and processed by the access point. User terminator 1 monitors the BCH to determine whether or not the RACH color bit in the BCH message is set. If such a bit is enabled, which indicates that an acknowledgment for this and / or other user terminals is being sent through the FCCH, then the user terminal further processes the FCCH to obtain 1E type 3 information elements containing acknowledgments. Otherwise, if c RACH acknowledgment bit is not set. then the user terminal continues to monitor the BCH or resumes its harassment procedure via RACH. G PC C H IP type 3 is a quick way to make quick access attempts. successful. Each acknowledgment information element contains MAC 11) associated with the user terminal to which the acknowledgment is sent. A quick acknowledgment is used to inform the user terminal that their access request has been received but is not associated with an FCH / RCi resource assignment. Otherwise, a confirmation based on. assignment is associated with an FCH / KCH assignment. If the user terminal receives "more than one" via the FCCK, it will go to the default. C js <„user terminal will receive a · '·' ηί !.: r.aç-e.} ..?; ···! i cm at rlbu: tion, it obtains the icçr.ms C 'information sent with the confirmation and starts using the FCH / RCH such. c orr, the attri bu 1. of the TD framework D acts 1.. () User terminal resumes the access procedure via RACH if it does not receive a confirmation to L rav is from FC CH d cr.tr odcum number specifies TDD frames after RACH PDU transmission In such a case, the user terminal may assume that the access point did not receive the RACH PDU correctly A counter is kept by the user terminal 1 to count the number of ter. Access Lables Each counter can be initialized to zero for the first access attempt and incremented by one for each subsequent access attempt. The user account will terminate the access procedure if the counter value reaches the maximum number of attempts. For each subsequent access attempt, the initial user terminal determines several parameters for each access attempt, including (1) the amount of time to wait before transmitting the RACH PDU, (2) the RACH partition to use for the PDU RACH transmission and (3) the rate for the RACH PDU. To determine the amount of time to wait, the user terminal first determines the maximum amount of time to wait for the next access attempt, which is referred to as the containment window (CW). In one embodiment, the containment window (which is given in TDD frame units) increases exponentially for each attempted access (ie, CW = 2 '' 'r;',: r ^ v'3, The containment window can also be determined based on some other function (for example, a linear function) of the number of access attempts.The amount of time to wait for the next access attempt is then randomly selected from zero and CW, 0 terminal The user will wait for such amount of time before transmitting the PDü RACH for the next access attempt.

For the next access attempt, the user terminal has the rate for the lowest r.ac that has been used for the last access attempt. The initial link 1 used for the first attempt Access range can be selected based on SNR received from pi Lee sent via BCIL Failure to receive a color. Information can be caused by the access point failing to properly receive the RACH PDU. Thus, the rate for the RACH PDU on the next access attempt is reduced to improve the likelihood of correct reception by the access point.

After waiting for the randomly selected timeout, the user terminal again randomly selects an RACH partition for RACH PDU transmission. The section of the RACH partition for such an access attempt is requested similarly to that described above for the first access attempt, except that the RACH parameters (i.e. the number of RACH partitions, duration partition and guard interval) for the TDD frame, as carried in the BCH message, are used together with the current RACH PDU length. The CUC KACH is then transmitted on the currently selected RACH partition. The access procedure described above continues until II) the user terminal receives an acknowledgment from the access point or (2} the maximum number of allowed access attempts has For each attempted access, the amount of time to be waited before transmitting the RACH PDU, the HACH partition to be used for the HACH PDU transmission and the rate for the HACH PDU can be selected as above. If acknowledgment is received, then the user terminal operates such a box indicated by acknowledgment <; isio è, it waits in idle state if a prompt acknowledgment is received, or starts using FCH / RCH if an acknowledgment is received. assignment-based; If the maximum number of allowed access attempts has been reached, then the user terminal returns to the initial study. Axis, Power, and Timing The access point programs downiiuk or uplínk transmissions via PCEL and HCH and also controls the rates for the active user terminals. In addition, the harness bridge adjusts the transmit power of certain uplmk active user terminals. Several control loops can be maintained to adjust the rate, transmission power and timing for each active user termination. 1. 5 services de_ Hl xu - 7αχ i 1 The lit point r. i «. · supte, ar tu * ·: o Lcsxa services fixed as variable in FCH and RCH. Flat rate services may have been used for voice, video, and so on. Variable rate services can be used for packet data (eg network browsing).

For FCH / RCH bare fee services, a flat rate is used for the entire connection. The best possible transport! It is used for FCH and HCH (ie, no retronsrr.ission). The access point programs a constant number of FCH / RCH PDUs per specified time interval to meet service QcS requirements. Depending on the delay requirements, the access point may not need to program an FCH / RCH PDU for each TDD frame. Power control is exercised through RCH but not FCH for fixed rate services.

For FCH / RCH rate-variable services, the rate used for FCH / RCH may change with channel conditions. For some isochronous services (eg video, audio !, QoS requirements may impose a minimum fee restriction. For such services, the programmer at the access point adjusts the FCH / RCH allocation so that a constant rate is provided. For asynchronous data services (eg network browsing, file transfer and so on), a better effort transport is provided with the retransmissions option. For such services, the rate is the maximum that can be reliably supported by channel conditions. Programming FCH / RCH PDUs for user terminals is typically a function of your QoS requirements. When there is no data to send via the linklink / uplink, a PL) is sent via FCH / HCH to keep the 1 i rk. Closed-loop power control is not exercised over FCH or RCH for variable rate services. 2 . Rate Control C rate control can be used for variable rate services operating on the FCH and RCH to adapt the FCH / RCH rate to changing channel conditions. The rates to be used for RCH and FCH can be controlled independently. In addition, in spatial mutation mode, the rate for each broadband autode of each dedicated transport channel can be independently controlled. Rate control is performed by access point cot. based on 1 imitation provided by each active user terminal. The programmer at the access point schedules data transmission and determines rate assignments for active user terminals. The maximum rate that can be supported on any of the links is 1 'dl. matrix d and resp c s t. a c a n a i p a r to all data subbands,; of the noise level observed by the receiver, (3) the quality of the channel estimation and passing: other indicators. For a TDD system,: .i channel can be considered as reciprocal for downlink and upiirik (after calibration has been performed to compensate for any differences in access point and user termination). However, such reciprocal channel does not imply that the noise floors are the same in the access tale and user terminal. Thus, for a given user terminal, the rates in FCH and RCH can be rolled independently. Closed loop rate control can be used for data transmission via one. or more space channels. Can closed loop rate control? be achieved with one or multiple meshes. An internal mesh estimates channel conditions and provides a suitable rate for each space channel used for data transmission. Channel estimation and rate selection can be performed as described above. An outer mesh can be used to estimate the quality of the diode transmission received on each space channel and to adjust the inner mesh relationship. The quality of data and transmission can be quantified by the error rate of the packets, decay measurements, and so on, or a combination thereof. As an example, the outer mesh can adjust the 5NR offset. for each space channel to get the target PER for that space channel. The outer mesh can also order the inner mesh to select a lower rate for a spatial caria if excess packet errors are detected by the spatial channel.

Dcwnlínk Rate Control Each active user terminal can estimate the downiink channel based on the MIMO pilot transmitted via the BCH in TDD frame frame * 0 access point can also transmit a directed reference on an FCH PDU sent to a user terminal specific. Using the MIMO pilot on the BCH and / or the directional reference on the FCH, the user terminal can estimate the received SNR and determine the maximum rate that can be supported on FCii. If the user terminal is operating in spatial nvultiplexing mode, then the maximum rate may be degraded for each broadband autode. Each user terminal can send back to the access point the maximum rate supported by each broadband auto (for multi-space mode}, the maximum rate supported by the main broadband auto (for beam steering mode) , or the maximum rate supported by the channel> 11 MC (for diversity mode; in the FDU RCH FCH rate indicator field. Such rates may be averaged for received SN Rs, which may be exceeded. Alternatively, the user terminal may send sufficient information (for example, received SN Rs) to allow the access point to determine the maximum rate supported by 1. The determination of whether to use beam steering diversity mode or spatial multipoint mode can be made based on the feedback from the user terminal. intended for use may increase as isolation between targeting vectors increases. h Figure 14K illustrates a process for controlling the transmission rate of the downlink to a user terminal. A BCH PDU is transmitted in the first segment of each TDD frame and includes the signaling and MIMO pilots that can be used by user terminals to estimate and track the channel. A directed reference can also be sent in the preamble of an FCH PDU sent to the user terminal. The user terminal estimates the channel based on the KlMC and / or directed reference and determines the maximum rates that can be supported by downlink. A fee is provided for each broadband bandwidth if the third time is opposed to the modulus of space exhaustion. The following user terminal sends the rate indicator expensive to FCH in the rate indicator field FCH of the FDU RCH and sends it to the access point. The programmer uses the maximum rates that the downlink can support for each active user terminal to rewrite downlink data transmission in subsequent TDD frames. Fees and other channel assignment information for the user terminal are reflected in an information element sent through the FCCH. The rate assigned to one user terminal may influence the reregulation to other user terminals. The minimum delay between user termination rate determination and usage is approximately a single TDD frame.

Using the orderly Gram-Schmidt procedure, the access point can accurately determine the maximum rates supported by the FCH directly from the RCH preamble. This can therefore greatly simplify the rate control.

Control cr. Ί _ »x_a n. Cp link Each user terminal transmits a directed reference through RACH during access to system 6: via RCH when receiving FCH / RCH resources. The access point can estimate the received SNR for each of the broadband devices based on the referenced RCH reference and determine the maximum rate supported by each broadband signal. Initially, the access point may not have a good channel estimate to allow reliable operation at or near the maximum rate supported by each broadband bus. To improve reliability, the initial rate used in FCH / RCH may be much lower than the maximum supported rate. The access point can integrate the directed reference over multiple TDD frames to get a better estimate of the cariai. If you want to estimate the channel at a later time, Figure 14B illustrates a process for controlling the rate of a transmission from uplir.k to a user terminal. When programmed for upiink transmission, the user terminal transmits an RCH PDU that includes the reference, which is used by the access point to determine the maximum upiink rate. The following programmer uses the maximum rates upiink can support for each active user terminal to schedule data transmission in upiink era. subsequent TDD frames. Fees and other channel assignment information for the user terminal are reflected in an information element sent through the FCCH. The minimum delay between rate determination by the access point and its use is approximately a single TDD frame. · Photon role The power control can be used for upiink transmissions through RCH (instead of rate control) for fixed rate services. For fixed rate services, the rate is negotiated at the onset of the call and remains fixed for the duration of the connection. Some fixed rate services may be associated with the 1Mimited mobility requirement. In a mod ally, the link is implemented for uplink to avoid interference between user terminals, but is not used for dcwnlink.

A power control mechanism is used to control the uplink transmission power of each active user terminal such that the SNR received at the access point is maintained at a level that achieves the desired quality of service. . Such a level is often referred to as the received target SNR, the operating point or setpoint. For a mobile user terminal, the early propagation loss will change as the user terminates. rivers 3 moves. The power control mechanism tracks channel changes so that the recreated SNR is maintained near the setpoint. The power control mechanism can be implemented with two power control loops - one inner loop and one outer loop. The internal machine adjusts the transmitting power of the user terminal such that the SNR received at the access point is kept close to the setpoint. The outer mesh adjusts setpoir.t for a particular level of performance, which can be quantified by a particular frame rate {FF.R} (for example, 1% FF1R), an error rate of packages; PNRê, an IBLER block error rate), an IMbRl message error rate, or some other measure. Figure 15 illustrates the operation of the ont. rol e de p o · t n n cia inte r η o p a r a u m i. cr mi n al from us u á r i o. After the user mine receives the FCH / RCH, the access point estimates the SNR received at the RCH and compares it to the setpoint. THE

The initial power scr used by the user terminal can be determined at the call establishment or is typically close to the maximum transmit power level. For each frame interval, if the received SNR exceeds the setpoint by a positive margin and only p 6 is e π t o o o o o r e r o r e r o r e n o r the terminal. that reduces its 5tn transmit power by a particular amount {for example, 1 dB} by. a to: FCCH information feed sent to such user terminal. In contrast, if 5 received SNR is more cash than the limit minus margin 8, then the access point may order the user terminal to raise its transmission rate by the particular amount. Case a 5 N R r e c e b í a. estia d e n t: r o of 1 i rr. When you have set r> hi rr, then the access point will not require a change in transmit power to the user terminal, uplink transmit power is given as the initial transmit power level plus the sum of all power adjustments received from the point of The initial setpoint used on the access point is adjusted to obtain a particular level of performance. This setpoint is adjusted by the outer mesh corr, based on FER or PER for the RCH. For example, if no frame or packet errors occur over a specified period of time, then the setpoint may be reduced by a first quantity (eg 0.1 dB). If the mean FP.R is exceeded by the occurrence of one or more frame or packet errors, then the setpoint may be raised by a second quantity (eg 1 dB). The setpoint, the hysteresis margin, and the ma ng e x t e n e s p e rc e s p o c tio n s for the power control project used for the system. Ί Tuning Arrays D n o rtin g .1 e d:: nnc> r i ng e ng r e rt e rtly used in a TDD-based frame structure when downlink and uplink share the same frequency band in a doubled split-sided manner. in powder . User terminations may be located throughout the entire system and may therefore be associated with different propagation delays to the access point.

To maximize upiink efficiency, the terrifying of the ri ns m a s d o u plin k. The user terminal can be adjusted to compensate for its propagation delay. This will therefore ensure that upiink transmissions from different user terminals arrive within one specific time window at the access point and do not interfere with each other in the upiink or downlink transmission. Figure 16 illustrates one. process for adjusting upiink vaporization of a user terminal. Initially, the user terminal sends an RftCH PDU through upiink to gain access to the system. The point of a c e s is the ri ve a sti ti vi ni ci a1 of the r e dt (and rtd) loop associated with the user terminal. The round-trip delay can be estimated based on (1) a sliding corrector used at the access point to determine the transmission znocycle and (2) the partition ID included in the RACH PDU sent by the user terminal. The following harness bridge computes one. .1 start timing advance to user endpoint based on KTD start estimate. The initial timing advance is sent to the end time before transmission through the R C H. The initial temperature control can be seen in a message via the FCH, a field of an FCCSi information element, or by some other means. The user terminal receives the initial time advance from the access point and then uses such a time advance on all subsequent uplink transmissions through RCH and RACH. If the user terminal receives FCH / RCH resources, then its timing advance can be adjusted as sent by the access point in the RCH timing setting field of an FCCH information element, the following user terminal would adjust its ro upiink transmissions through the RCH based on the current timing advance, which is equal to the timing advance initializing all timing adjustments sent by the access point to the user Lerrr.al ·. Various parts of the MIMO WLAN system and various techniques described herein may be implemented by several mere. As an example, access point and user endpoint processing may be implemented in hardwaro, software, or a combination thereof. For a hardware implementation, processing may be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PhDs), arrays. field programmable port switches (PPGAsj, processors, controllers, microcontrollers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

For a software implementation, processing may be implemented by means of modules (e.g., procedures, functions, and so forth) that perform the functions described herein. The software codes may be sibling on a memory unit (e.g., memory 732 or 782 in Figure 7) and executed by a processor (e.g., controller 30 or 80). The memory unit may be implemented within the processor or external to the processor, in which case it may be coupled in communication with the processor through various devices as is well known to those skilled in the art.

Headings are included herein for reference and to assist in locating certain sections. Such headings are not intended to limit the scope of the concepts herein, and such concepts may be applied in other sections describing them. . I see you The above description of preferred embodiments is provided to enable anyone skilled in the art to utilize the present invention. The different typifications of these embodiments will be readily apparent to those skilled in the art and the general principles herein. They may be applied to other embodiments without departing from the spirit or scope of the invention. Accordingly, the present invention should not be limited to the embodiments herein and should be given the broader scope consistent with the novel principles and features described herein.

Claims (15)

Method for transmitting signaling information in a multi-input and multi-output (MIMO) wireless communication system (100) using orthogonal frequency division multiplexing (OFDM), characterized in that it comprises the steps of: transmitting first signaling information for a first set of at least one user terminal (120) in a first coding rate and modulation scheme combination in a first subchannel of a direct control channel, wherein the first signaling information comprises an element information indicating that the first signaling information serves the first set of at least one user terminal (120); transmitting second signaling information to a second set of at least one user terminal (120) in a second coding rate and modulation scheme combination on a second direct control channel subchannel, wherein the second signaling information comprises a information element indicating that the second signaling information is for the second set of at least one user terminal (120); wherein the second coding rate and modulation scheme combination is different from the first coding rate and modulation scheme combination and wherein the second subchannel has a higher rate than the first subchannel and is transmitted after the first subchannel. Method according to claim 1, characterized in that it further comprises: transmitting third signaling information to a third set of at least one user terminal (120) in a third coding rate and modulation scheme combination. in a third direct control channel subchannel, wherein the third signaling information comprises an information element indicating that the signaling information is for the third set of at least one user terminal, wherein the third encoding rate combination and modulation scheme is different from the first and second combinations of coding rate and modulation scheme, and wherein the third subchannel has a higher rate than the second subchannel and is transmitted after the second subchannel. Method according to claim 1, characterized in that the first subchannel indicates whether or not the second subchannel is transmitted in a current frame. Equipment (110) for transmitting signaling information in a multi-input and multiple output (MIMO) wireless communication system (100) using orthogonal frequency division multiplexing (OFDM), characterized in that it comprises: devices for transmitting first signaling information to a first set of at least one user terminal (120) in a first coding rate and modulation scheme combination on a first subchannel of a direct control channel, wherein the first signaling information comprises an information element indicating that signaling information is for the first set of at least one user terminal; and devices for transmitting second signaling information to a second set of at least one user terminal (120) in a second coding rate and modulation scheme combination in a second direct control channel subchannel, wherein the second signaling information Signaling comprises an information element indicating that the second signaling information is for the second set of at least one user terminal; wherein the second coding rate and modulation scheme combination is different from the first coding rate and modulation scheme combination and wherein the second subchannel has a higher rate than the first subchannel and is transmitted after the first subchannel. Equipment according to claim 4, characterized in that it further comprises: devices for transmitting third signaling information to a third set of at least one user terminal in a third combination of coding rate and modulation scheme in a third direct control channel subchannel, wherein the third signaling information comprises an information element indicating that the signaling information is for the third set of at least one user terminal, wherein the third encoding rate combination and Modulation scheme is different from the first and second combinations of coding rate and modulation scheme, and the third subchannel has a higher rate than the second subchannel and is transmitted after the second subchannel. Equipment according to claim 4, characterized in that the first subchannel indicates whether or not the second subchannel is transmitted in a current frame. Equipment according to any one of claims 4 to 6, characterized in that: the devices for transmitting signaling information are a transmission data processor (710) and a transmitting unit (724). Method for receiving signaling information at a user terminal (120) in a multi-input and multiple output (MIMO) wireless communication system (100) using orthogonal frequency division multiplexing (OFDM), characterized in that comprising the steps of: receiving first signaling information sent in a first coding rate and modulation scheme combination on a first subchannel of a direct control channel, the first signaling information comprises a first information element indicating that the first signaling information is for a first set of at least one user terminal (120); and receiving second signaling information sent in a second coding rate and modulation scheme combination in a second subchannel of the direct control channel if the first information element indicates that the signaling information is not for the user terminal (120). ), the second signaling information comprises a second information element indicating that the second signaling information is for a second set of at least one user terminal (120), wherein the second combination of coding rate and modulation scheme is. different from the first combination of coding rate and modulation scheme and where the second subchannel has a higher rate than the first subchannel and is transmitted after the first subchannel. A method according to claim 8 further comprising: receiving third signaling information sent in a third coding rate and modulation scheme combination in a third direct control channel subchannel if the second information element indicates that the second signaling information is not for the user terminal 120, the third signaling information comprises a third information element indicating that the third signaling information is for a third set of at least one signaling terminal. where the third coding rate and modulation scheme combination is different from the first and second coding rate and modulation scheme combinations, and the third subchannel has a higher rate than the second subchannel and is transmitted after the second subchannel. A method according to claim 8 further comprising: terminating direct control channel processing by encountering decoding failure for a direct control channel subchannel. 11. User terminal (120) configured to receive signaling information in a multi-input and multiple-output (MIMO) wireless communication system (100) using orthogonal frequency division multiplexing (OFDM), characterized in that it comprises : Devices for receiving first signaling information sent in a first coding rate and modulation scheme combination in a first subchannel in a direct control channel, the first signaling information comprises a first information element indicating that the first signaling information serves a first set of at least one user terminal; and devices for receiving second signaling information sent in a second coding rate and modulation scheme combination in a second subchannel of the direct control channel, if the first information element indicates that the first signaling information is not intended for the signaling terminal. 120, the second signaling information comprises a second information element indicating that the second signaling information is for a second set of at least one user terminal (120), wherein the second coding rate and scheme combination Modulation is different from the first combination of coding rate and modulation scheme, and the second subchannel has a higher rate than the first subchannel and is transmitted after the first subchannel. User terminal (120) according to claim 11, characterized in that it further comprises: devices for receiving third signaling information sent in a third coding rate and modulation scheme combination in a third channel subchannel If the second information element indicates that the second signaling information is not for the user terminal 120, the third signaling information comprises a third information element indicating that the third signaling information is for a third party. at least one user terminal, wherein the third coding rate and modulation scheme combination is different from the first and second coding rate and modulation scheme combinations, and the third subchannel has a higher rate than the second subchannel and is transmitted after the second subchannel. User terminal (120) according to claim 11, characterized in that it further comprises: devices for terminating direct control channel processing by encountering decoding failure for a direct control channel subchannel. User terminal (120) according to any one of claims 11 to 13, characterized in that: the receiving devices are a receiving data processor (770) and an operating controller (780) for orienting the device. processing for the first and second subchannels. User terminal (120) according to claim 14, characterized in that the controller (780) is additionally operative to terminate direct control channel processing upon encountering a decoding fault for a control channel subchannel. direct.