KR100983942B1 - Communication method for use in multi-hop wireless communication system, multi-hop wireless communication system, base station apparatus, intermediate apparatus, and use equipment - Google Patents

Abstract

A transmission method for use in a multi-hop wireless communication system, the system comprising a calling device, a called device, and two or more intermediate devices, the calling device from the calling device via each intermediate device. Operable to transmit information along a series of links forming a communication path to the device, each intermediate device receiving information from the preceding device along the path and transmitting the received information to subsequent devices along the path And the system has access to a time-frequency format for use in allocating available transmission frequency bandwidths during discrete transmission intervals, the format having multiple transmission windows within such intervals. Each window occupies a different part of the segment and its part of the segment Having a frequency bandwidth profile within the available transmission frequency bandwidth for minutes, each said window being assignable to one of the devices for use in transmission during such transmission interval, and the method further comprising: one or more such transmission intervals While using the format, transmitting information along at least three consecutive said links as a set of consecutive transmitted signals on a link basis, wherein each said signal is transmitted in an available transmission window of said interval (s) and At least two of the signals are transmitted during the same transmission period, such that the information is transmitted along the consecutive links in fewer transmission periods.

Multi-hop wireless communication system, calling device, called device, intermediate device, transmission frequency bandwidth, time-frequency format, transmission interval, transmission window

Description

TECHNICAL METHOD FOR USE IN MULTI-HOP WIRELESS COMMUNICATION SYSTEM, MULTI-HOP WIRELESS COMMUNICATION SYSTEM, BASE STATION APPARATUS, INTERMEDIATE APPARATUS, AND USE EQUIPMENT}

The present invention relates to a communication system, and more particularly, to a multi-hop wireless communication system.

Recently, there is considerable interest in using multi-hop techniques in packet-based wireless and other communication systems, since such techniques will enable both an extension of coverage range and an increase in system capacity (throughput).

In a multi-hop communication system, communication signals are transmitted in a communication direction along a communication path C from the originating device to the destination device via one or more intermediate devices. 4 shows a base station BS (known as "Node-B (NB)" in the context of 3G communication systems), a relay node (RN) (known as a relay station (RS)), and a mobile station (MS). A single-cell two-hop wireless communication system having a user equipment (UE), also known as. When signals are transmitted from the base station to the destination user equipment (UE) via the downlink (DL) via the relay node (RN), the base station means the originating station (S) and the user equipment refers to the destination station (D). it means. When communication signals are transmitted from the user equipment (UE) via the relay node to the base station via the uplink (UL), the user equipment means the calling station and the base station means the called station. The relay node is an example of an intermediate apparatus I and has a receiver operable to receive data from the originating apparatus and a transmitter operable to transmit this data or a derivative thereof to the destination apparatus.

Simple analog repeaters or digital repeaters have been used as relays to improve or provide coverage in dead spots. They can operate in a different transmission frequency band than the originating station or in the absence of transmission from the originating station in order to prevent interference between the originating station transmission and the repeater transmission.

5 illustrates a number of applications for relay stations. In the case of fixed infrastructure, the coverage provided by the relay station allows mobile stations that are unable to receive a signal of sufficient strength from the base station, even in the shadow of other objects or within the normal range of the base station, to access the communication network. It may be "in-fill". Also shown is a "range extension" which allows the relay station to access when the mobile station is outside the base station's normal data transmission range. An example of the in-fill shown in the upper right of FIG. 5 is the placement of a nomadic relay station to allow for coverage extension in a building that may be located on the ground, on the ground, or below the ground.

Other applications are nomadic relay stations that provide access during an incident or emergency / disaster, resulting in a temporary cover effect. The last application, shown at the bottom right of FIG. 5, provides access to the network using a relay device deployed in the vehicle.

Relay devices may be used with advanced transmission techniques to improve the gain of the communication system, as described below.

As is well known, in the case of wireless communications, scattering or absorption occurs as it travels through space, resulting in propagation loss or "path loss", resulting in poor signal strength. Factors affecting path loss between the transmitter and receiver include transmitter antenna height, receiver antenna height, carrier frequency, clutter type (urban, suburban, rural), topographical details such as height, density, and separation. , Topography types (hills, flats). The path loss (L (dB)) between the transmitter and the receiver can be modeled by the following equation A,

Equation A

Where d (meter) is the isolation distance between the transmitter and the receiver, b (db) and n are the path loss parameters and the absolute path loss is given by l = 10 ^{(L / 10)} .

The sum of the absolute path losses experienced on the indirect link (SI + ID) may be less than the path losses experienced on the direct link (SD). In other words, the following equation B can be established.

Equation B

Thus, dividing a single transmission link into two shorter transmission segments uses a nonlinear relationship between path loss versus distance. From a simple theoretical analysis of path loss using Equation A, if a signal is not transmitted directly from the originating device to the destination device, but from the originating device to the destination device via an intermediate device (e.g., a relay node), It will be appreciated that a reduction in overall path loss (and thus an improvement or gain in signal strength and data throughput) can be realized. If implemented properly, multi-hop communication systems can reduce the level of interference as well as reduce exposure to electromagnetic radiation by enabling a reduction in the transmit power of transmitters that facilitate wireless transmission. Alternatively, the reduction in overall path loss can be used to improve the received signal quality at the receiver without increasing the overall radiated transmission power required for signal transmission.

Multi-hop systems are suitable for use by multi-carrier transmission. In a multi-carrier transmission system such as frequency division multiplex (FDM), orthogonal frequency division multiplex (OFDM), or discrete multi-tone (DMT), a single data stream has N parallel subcarriers, each with its own frequency range. Is modulated by As a result, the total bandwidth (that is, the amount of data to be transmitted in a predetermined time period) is divided over a plurality of subcarriers, thereby increasing the interval of each data symbol. Since each of the subcarriers has a lower information rate, multicarrier systems take advantage of improved resistance to distortion due to the channel compared to single carrier systems. This is accomplished by ensuring that the transmission rate and hence the bandwidth of each of the subcarriers is less than the coherent bandwidth of the channel. As a result, the channel distortion experienced by the subcarriers of the signal is frequency independent and can therefore be corrected by a simple phase and amplitude correction factor. As such, channel distortion correction entities in a multi-carrier receiver can be significantly less complex than those in a single carrier receiver if the system bandwidth exceeds the coherence bandwidth of the channel.

OFDM is a modulation technique based on FDM. An OFDM system can overlap without interference due to the fact that the spectra of subcarriers are independent of each other by using a plurality of subcarrier frequencies that are orthogonal from a mathematical point of view. Orthogonality of OFDM systems increases the spectral efficiency of the system by eliminating the need for guard band frequencies. OFDM has been proposed and adopted in many wireless systems. Currently, OFDM is used in Asymmetric Digital Subscriber Line (ADSL) connections, in some wireless LAN applications (such as WiFi devices based on the IEEE 802.11a / g standard), and in wireless MAN applications such as WiMAX (based on the IEEE 802.16 standard). This is used. OFDM is often used in conjunction with channel coding and error correction techniques to produce coded orthogonal FDM (COFDM). COFDM is currently widely used in digital telecommunication systems to improve the performance of OFDM based systems in a multipath environment where variations in channel distortion can occur in both frequency carrier subcarriers and time domain symbols. The system has been used for certain types of computer networking technologies as well as video and audio broadcasts such as DVB and DAB.

In an OFDM system, a block of N modulated parallel data transmission signals is orthogonalized using an Inverse Discrete or Fast Fourier Transform algorithm (IDFT / IFFT) to form a signal known as an " OFDM symbol " in the time domain at the transmitter. To parallel subcarriers. As such, an "OFDM symbol" is a composite signal of all N subcarrier signals. OFDM symbol may be mathematically represented as the following equation (1),

Here, Δf is the subcarrier isolation distance in Hz, Ts = 1 / Δf is the symbol time period in seconds, and c _n is the modulated outgoing signals. The subcarrier vector (c ∈ C _n , c = (c ₀ , c ₁ ..c _N-1 )) in Equation 1 in which each of the outgoing signals is modulated is _N constrained from finite constellation. It is a vector of symbolization symbols. At the receiver, the received time domain signal is transformed back into the frequency domain by applying a Discrete Fourier Transform (DFT) or Fast Fourier Transform (FFT) algorithm.

Orthogonal Frequency Division Multiple Access (OFDMA) is a modified multiple access scheme of OFDM. It is effective by assigning a subset of subcarriers to individual users. This allows simultaneous transmission from several users, making the spectrum efficiency better. However, there is still a problem of enabling communication in both directions, i.e., uplink and download directions, without interference.

In order to enable bidirectional communication between two nodes, the physical limitation that the device cannot transmit and receive simultaneously over the same resource medium by duplexing two (forward or download and reverse or uplink) communication links There are two different known methods to overcome this. First, frequency division duplexing (FDD) requires operating the two links simultaneously but over different frequency bands by subdividing the transmission medium into two separate bands, one forward link communication and the other reverse link communication. Shall be. Second, time division duplexing (TDD) allows two links to operate in the same frequency band, but at any one time it is possible to subdivide access to the transmission medium in time such that only the forward or reverse link uses the medium. in need. Both methods (FDD & TDD) have their own relative advantages, all of which are widely used in single hop wired and wireless communication systems. For example, the IEEE 802.16 standard includes both FDD and TDD modes.

As an example, FIG. 6 illustrates a single hop TDD frame structure used in the OFDMA physical layer mode of the IEEE 802.16 standard (WiMAX).

Each frame is divided into a DL subframe and a UL subframe, each of which is a separate transmission interval. They are separated by Transmit / Receive Transition Guard interval (TGT) and Receive / Transmit Transition Guard interval (RTG). Each DL subframe starts with a preamble followed by a Frame Control Header (FCH), DL-MAP, and UL-MAP.

The FCH includes a DL Frame Prefix (DLFP) for specifying the length and burst profile of the DL-MAP. The DLFP is a data structure transmitted at the beginning of each frame and contains information about the current frame, which is mapped to the FCH.

Concurrent DL assignments may be broadcast, multicast, and unicast, and they may also include assignments for other BSs than the serving BS. Concurrent ULs may be data allocations and range or bandwidth requests.

This patent application is the same applicant's agent reference numbers of P106752GB00, P106753GB00, P106754GB00, P106772GB00, P106773GB00, P106795GB00, P106796GB00, P106797GB00, P106798GB00, and P106799GB00, which describe the correlation inventions proposed by the inventors for the communication technologies. Is one of ten British patent applications filed on the same day by. The entire contents of each of the remaining nine applications are incorporated herein.

The invention is defined in the independent claims, to which reference should now be made. Preferred embodiments are described in the dependent claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred features of the present invention will be described as examples only with reference to the accompanying drawings.

When one node needs to support two independent links to two different nodes, for example when the relay station is in communication with a base station and a mobile station, it is a practical relay for existing TDD or FDD frame structures. Some change is required for realization.

Embodiments of the present invention provide a frame structure for a multi-hop communication system that is an extension of the standard TDD frame structure (see, for example, the IEEE 802.16 standard) to provide support for any number of hops in a multi-hop communication system. . This proposed frame structure has many advantages as follows.

In summary, the advantages of embodiments of the present invention are:

O Enables the configuration and operation of simple low cost relay devices that do not need to generate any control information or do scheduling.

Maximize spectral efficiency by ensuring that the BS does not have any time in the frame when the BS is idle.

Minimum latency: The frame-by-frame latency is 0 for 1 or 2 hops, 1 for 3 or 4 hops, 2 for 5 or 6 hops, and 3 for 7 or 8 hops.

O Allow the system to provide transparent operation to legacy single-hop TDD users.

By using SDMA-based techniques, the same transmission resources (frequency & time) can be used between BSs, RSs, and MSs in a cell, thereby further improving spectrum efficiency.

Scalable to any number of hops

Details of the preferred frame structure and system behavior

The proposed frame structure assumes that control information originating from the head node controlling the overall media access is receivable by all underlying nodes operating in the network. The modified frame TDD structure also assumes that legacy mobile devices without knowledge of the relay station should be able to operate in the system.

The proposed general TDD frame structure is shown in FIG.

It consists of multiple transmit and receive zones for both downlink and uplink subframes. Zone types are one of the following:

Broadcast of control related information such as B synchronization sequences, instructions, information, and details of the structure or layout of the frame

Dedicated control information transmitted in the C non-broadcast zone (ie to individual receivers or receiver groups)

T-only user-data transmission

Nine different zones are described in Table 1 below.

area
number label Explanation One P Transmit Preamble or Synchronization Sequence for Cell Identification 2 MAP Frame format description (zone boundaries, allocations within zones, etc.) 3 BS-RS / BS-MS / RS-RS / MS BS to RS transmission zone. If space division multiple access is supported (ie, the same transmission resource is available for communication with two or more entities), it is also available for BS to MS transmission. Also available for RS-to-RS or MS transmission. 4 BS-MS BS to MS transmission zone. The RS is inactive during this period, which is processing any received information and turning around before transmission. 5 BS-MS / RS-RS / MS RS to RS or MS transmission zone. It is also available for transmission by the BS to MSs that are not subject to a significant level of interference from RS transmissions. 6 MS-BS / MS-RS MS control information transmission zone. The information may be received by both RS and BS. The control information can be information or requests from the MS. 7 MS-BS /
MS / RS-RS MS or RS to RS transmission zone. It is also available for transmission to the BS by MSs that do not interfere with the RS. 8 MS-BS MS to BS transmission zone. The RS does not actively transmit or receive during this period, which is processing any received information before turn around. 9 RS-BS / MS-BS / MS / RS-RS RS to BS transmission zone. If space division multiple access is supported (ie, the same transmission resource is available for communication with two or more entities), it is also available for MS-to-BS transmission. Also available for MS or RS-to-RS communication.

Table 1. Descriptions of Zones

FIG. 2 illustrates the operation of the BS, RS, and MS in terms of its activity within each zone described in Table 1 when the MS is connected to the BS via two RSs RS1 & RS2. . Note that, as zones (3) and (9) are used for communication with the BS, RS1 uses zones (5) and (7) for communication with RS2. The method also allows relaying information along the first hop within the same frame. RS2 uses zones 3 and 9 for communication with any MSs (or additional RSs). If there is a third RS (RS3), it will use the zones (5) and (7) for communication with any MSs or additional RSs.

Note that the relay along the first two hops occurs within one frame. However, relaying along three hops results in additional frame delay. In the general case of N hops, it was found that the additional delay incurred through relaying is given by the following equation.

3 shows one specific implementation of the proposed frame structure in terms of how different user types can be assigned to various zone types.

In this case, there are six link types identified as (A, C-G). Table 2 below describes the zones used in each of the links in this example.

link Use of DL zone Use of UL zones Explanation (A) (1), (2), (5) (6), (7) The MS and RS are spatially separated so that there is considerable interference isolation. (C) (1), (2), (3), (5) (6), (7), (9) RS1 receives data in (3) and (7) and then transmits in (5) and (9). (D) (1), (2), (5) (6), (7) The MS communicates with the BS via RS1. Transmission to the RS occurs at the start of the UL subframe, allowing sufficient RS relay processing time. (E) (1), (2), (4) (6), (8) MSs that communicate directly with a BS that is not isolated from the RS use zones (4) & (8) to prevent RS interference from degrading link performance. (F) (1), (2), (5) (6), (7) RS1 and RS2 communicate using the same zones that RS1 uses for communication with MSs connected via RS1. (G) (1), (2), (3) (6), (9) RS2 communicates with the MS using zones (3) and (9).

Table 2. Description of Examples of Zone Use in One Cell

Embodiments of the invention may be implemented in hardware, as software modules running on one or more processors, or in a combination thereof. In other words, those skilled in the art will appreciate that a microprocessor or digital signal processor (DSP) may be used substantially to implement some or all of the functionality of the transmitter embodying the present invention. The invention may be embodied as one or more device or device programs (eg, computer programs and computer program products) for performing some or all of any of the methods described herein. Such programs embodying the present invention may be stored in computer readable media or may be, for example, in the form of one or more signals. Such signals may be data signals downloadable from an internet website, or may be provided via a carrier signal or in any other form.

1 illustrates a frame structure.

2 illustrates node activity within each zone.

3 shows an example of the use of zones within one cell.

4 illustrates a single-cell two-hop wireless communication system.

5 illustrates applications of relay stations.

6 illustrates a single hop TDD frame structure used in the OFDMA physical layer mode of the IEEE 802.16 standard.

<Explanation of symbols for the main parts of the drawings>

B: broadcast zone

C: control transmission area

T: Data transfer transmission area

Claims (12)

A communication method for use in a multi-hop wireless communication system comprising a base station device, an intermediate device, and user equipment, the method comprising: Transmitting preambles, frame structure information, and data to be transmitted to the intermediate apparatus; Providing a gap period between a reception period in which the preamble, the frame structure information and the data to be transmitted to the intermediate apparatus are received by the intermediate apparatus and a transmission period in which data is transmitted from the intermediate apparatus; Transmitting data from the base station apparatus to the user equipment using the gap period; Receiving, by the user equipment, the preamble and the frame structure information and the data transmitted from the base station apparatus using the gap period. Communication method comprising a. The method of claim 1, The gap period is used to transition from a receive state to a transmit state in the intermediate apparatus. A communication method for use in a multi-hop wireless communication system comprising a base station device, an intermediate device, and user equipment, the method comprising: Transmitting preamble and frame structure information from the base station apparatus; Providing a gap period between a reception period in which the intermediate apparatus receives data and a transmission period in which the intermediate apparatus transmits data to the base station apparatus; Receiving, by the user equipment, the preamble and the frame structure information from the base station apparatus; Transmitting data from the user equipment to the base station apparatus using the gap period. Communication method comprising a. The method of claim 3, The gap period is used to transition from a receive state to a transmit state in the intermediate apparatus. A multi-hop wireless communication system, A base station apparatus configured to transmit preambles, frame structure information, and data for transmission to an intermediate apparatus; The intermediate apparatus configured to receive the preamble, the frame structure information and the data to be transmitted to the intermediate apparatus in a reception period, and to transmit data in the transmission period; User equipment configured to receive the preamble and the frame structure information Including; The base station apparatus transmits data to the user equipment using a gap period between the reception period and the transmission period, and the user equipment receives the data transmitted from the base station apparatus using the gap period. -Hop wireless communication system. A multi-hop wireless communication system, A base station apparatus configured to transmit preamble and frame structure information; An intermediate apparatus configured to receive data in a reception period and to transmit data to the base station apparatus in a transmission period; User equipment configured to receive the preamble and the frame structure information Including; The user equipment transmits data to the base station apparatus using a gap period between the reception period and the transmission period, and the base station apparatus receives the data transmitted from the user equipment using the gap period. -Hop wireless communication system. A base station apparatus for use in a multi-hop wireless communication system comprising a base station apparatus, an intermediate apparatus, and user equipment, The base station apparatus is configured to transmit preamble, frame structure information and data to be transmitted to the intermediate apparatus, The intermediate apparatus is configured to receive the preamble, the frame structure information and the data to be transmitted to the intermediate apparatus in a reception period, and transmit data in the transmission period, The user equipment is configured to receive the preamble and the frame structure information, The base station apparatus transmits data to the user equipment using a gap period between the reception period and the transmission period, and the user equipment receives the data transmitted from the base station apparatus using the gap period. Base station device. A base station apparatus for use in a multi-hop wireless communication system comprising a base station apparatus, an intermediate apparatus, and user equipment, comprising: The base station apparatus is configured to transmit preamble and frame structure information, The intermediate apparatus is configured to receive data in a reception period and to transmit data to the base station apparatus in a transmission period, The user equipment is configured to receive the preamble and the frame structure information, The user equipment transmits data to the base station apparatus using a gap period between the reception period and the transmission period, and the base station apparatus receives the data transmitted from the user equipment using the gap period. Base station device. An intermediate apparatus for use in a multi-hop wireless communication system comprising a base station apparatus, an intermediate apparatus, and user equipment, The base station apparatus is configured to transmit preamble, frame structure information and data to be transmitted to the intermediate apparatus, The intermediate apparatus is configured to receive the preamble, the frame structure information and the data to be transmitted to the intermediate apparatus in a reception period, and transmit data in the transmission period, The user equipment is configured to receive the preamble and the frame structure information, The base station apparatus transmits data to the user equipment using a gap period between the reception period and the transmission period, and the user equipment receives the data transmitted from the base station apparatus using the gap period. Intermediate device. An intermediate apparatus for use in a multi-hop wireless communication system including a base station apparatus, an intermediate apparatus, and user equipment, The base station apparatus is configured to transmit preamble and frame structure information, The intermediate apparatus is configured to receive data in a reception period and to transmit data to the base station apparatus in a transmission period, The user equipment is configured to receive the preamble and the frame structure information, The user equipment transmits data to the base station apparatus using a gap period between the reception period and the transmission period, and the base station apparatus receives the data transmitted from the user equipment using the gap period. Intermediate device. A user equipment for use in a multi-hop wireless communication system comprising a base station apparatus, an intermediate apparatus, and user equipment, The base station apparatus is configured to transmit preamble, frame structure information and data to be transmitted to the intermediate apparatus, The intermediate apparatus is configured to receive the preamble, the frame structure information and the data to be transmitted to the intermediate apparatus in a reception period, and transmit data in the transmission period, The user equipment is configured to receive the preamble and the frame structure information, The base station apparatus transmits data to the user equipment using a gap period between the reception period and the transmission period, and the user equipment receives the data transmitted from the base station apparatus using the gap period. User equipment. A user equipment for use in a multi-hop wireless communication system comprising a base station apparatus, an intermediate apparatus, and user equipment, The base station apparatus is configured to transmit preamble and frame structure information, The intermediate apparatus is configured to receive data in a reception period and to transmit data to the base station apparatus in a transmission period, The user equipment is configured to receive the preamble and the frame structure information, The user equipment transmits data to the base station apparatus using a gap period between the reception period and the transmission period, and the base station apparatus receives the data transmitted from the user equipment using the gap period. User equipment.

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