RU2473170C2 - Transfer of pilot signal and data in mimo system applying subband multiplexing - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: invention relates to a system of multiple access with frequency division with a single carrier (SC-FDMA), which uses an interlaced FDMA (IFDMA) or a limited FDMA, multiple transmitters may send their control signals using multiplexing with time division (TDM), multiplexing with code division (CDM), frequency multiplexing with interlacing (IFDM), or limited frequency multiplexing (LFDM). Control signals from these transmitters in this case are orthogonal to each other. A receiver performs complementary demultiplexing for control signals sent by transmitters. The receiver may receive a channel estimate for each transmitter, using a method of minimum mean-square error (MMSE) or a method of least squares. The receiver may receive overlapping data transfers sent on one and the same frequency-time unit by multiple transmitters and may perform spatial processing for the receiver with matrices of a space filter, in order to identify such data transfers. The receiver may receive matrices of the space filter on the basis of channel estimates for transmitters and using methods of conversion to zero, MMSE, or combination of maximum ratio.

EFFECT: support of simultaneous transfer for larger quantity of terminals in a system of multiple access.

28 cl, 21 dwg

Description

Priority claim under 35 U.S.C §119

This patent application claims the priority of provisional application No. 60/691701 "PILOT AND DATA TRANSMISSION IN A QUASI-ORTHOGONAL SINGLE-CARRIER FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM", filed June 16, 2005, provisional application No. 60/702033 "PILOT AND DATA TRANSMISSION IN A QUASI-ORTHOGONAL SINGLE-CARRIER FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM "filed July 22, 2005 and provisional application No. 60/710366," PILOT AND DATA TRANSMISSION IN A QUASI-ORTHOGONAL SINGLE-CARRIER FREQUENCY DIVISCION MULTIPLE 2005, August 22, 2005 hereto, and hereby expressly incorporated herein by reference.

Technical field

This disclosure relates generally to communications, and more specifically to the transmission of a pilot signal and data in a wireless communication system.

State of the art

A multiple access system can simultaneously communicate with multiple terminals on the forward and reverse links. A forward link (or downlink information transfer) refers to communication from base stations to terminals, and a reverse link (or uplink) refers to communication from terminals to base stations. Many terminals can simultaneously transmit data on the reverse link and / or receive data on the forward link. This is often achieved by multiplexing multiple data transmissions on each communication link orthogonal to each other in time, frequency, and / or code area. Complete orthogonality among multiple data transmissions typically is not achieved in most cases due to various factors, such as channel conditions, receiver imperfections, and so on. However, orthogonal multiplexing ensures that data transmission for each terminal minimally interacts with data transmissions for other terminals.

The number of terminals that can exchange with a multiple access system at any given moment is typically limited by the number of traffic channels available for data transmission, which in turn is limited by available system resources. For example, the number of traffic channels can be determined by the number of available sequences of orthogonal codes in a code division multiple access (CDMA) system, the number of available frequency subbands in a frequency division multiplexing (FDMA) system, the number of available time slots in a multiple access system with time division mode (TDMA), and so on. In many cases, it is desirable to allow more terminals to simultaneously communicate with the system in order to improve system capacity.

Therefore, there is a need in the art for methods for supporting simultaneous transmission for more terminals in a multiple access system.

SUMMARY OF THE INVENTION

The pilot (pilot) signal transmission, channel estimation, and spatial processing methods that support simultaneous transmissions for terminals in a single carrier frequency division multiple access (SC-FDMA) system are described below. An SC-FDMA system can use (1) interleaved FDMA (IFDMA) to transmit data and pilot in subbands that are allocated in the system’s frequency band or band, (2) limited FDMA (LFDMA) to transmit data and pilot over a group of adjacent subbands, or (3) Advanced FDMA (EFDMA) to transmit data and pilot to a plurality of groups of adjacent Sudbands. IFDMA is also called distributed FDMA, and LFDMA is also called narrowband FDMA, classic FDMA, and FDMA.

For transmitting a pilot signal, a plurality of transmitters may transmit their pilots using time division multiplexing (TDM), code division multiplexing (CDM), frequency interlace multiplexing (IFDM), or limited frequency multiplexing (LFDM), as described below. The control signals from these transmitters are orthogonal to each other, which allows the receiver to receive a higher quality channel estimate for each transmitter.

For channel estimation, the receiver performs complementary demultiplexing for pilots sent by transmitters with TDM, CDM, IFDM or LFDM. A receiver may obtain a channel estimate for each transmitter using, for example, a minimum mean square error (MMSE) method, a least squares (LS) method, or some other channel estimation method. The receiver may also perform filtering, threshold limiting, truncation, and / or connection selection to obtain an improved channel estimate.

The receiver also performs spatial processing for transmitting data received from the transmitters for the same time-frequency block. The receiver may obtain spatial filter matrices based on channel estimates for the transmitters and using, for example, Zero Methods (ZF), MMSE Methods, or Maximum Ratio Combination Methods (MRC).

Various aspects and embodiments of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and essence of the present invention will become more apparent from the detailed description set forth below when it is read in conjunction with the drawings, in which like reference characters identify like throughout the description.

Figure 1 shows a Q-FDMA system with multiple transmitters and a receiver.

2A shows an exemplary subband structure for IFDMA.

2B shows an exemplary subband structure for LFDMA.

2C shows an exemplary subband structure for EFDMA.

3A shows IFDMA, LFDMA, or EFDMA symbol generation.

3B shows IFDMA symbol generation.

Figure 4 shows a jumping frequency circuit.

5 shows a TDM pilot scheme.

6 shows a CDM pilot scheme.

7 shows a distributed / localized pilot scheme.

Fig. 8A shows distributed pilots for two IFDMA transmitters.

8B shows distributed pilots for two transmitters with LFDMA.

Fig. 9A shows localized pilots for two IFDMA transmitters.

9B shows localized pilots for two transmitters with LFDMA.

10 shows a transmission with different data durations and pilot symbol.

11 shows a process for transmitting a pilot and data in a Q-FDMA system.

12 shows a process for performing channel estimation.

13 shows H-ARQ transmission.

14 shows an H-ARQ transmission for two transmitters.

15 shows a block diagram of a transmitter.

16 shows a block diagram of a receiver.

DETAILED DESCRIPTION

The word "exemplary" is used here to mean "serve as an example, occasion, or illustration." Any embodiment or construction described herein as “exemplary” should not necessarily be construed as preferred or advantageous over other embodiments or constructions.

Pilot transmission, channel estimation, and spatial processing techniques described herein may be used for various communication systems. For example, these methods can be used for an SC-FDMA system that uses IFDMA, LFDMA or EFDMA, an orthogonal frequency division multiple access (OFDMA) system that uses orthogonal frequency division multiplexing (OFDM), other FDMA systems, and other OFDM-based systems, and so on. Modulation symbols are sent in the time domain with IFDMA, LFDMA and EFDMA and in the frequency domain with OFDM. In general, methods can be used for a system that uses one or more forward and reverse link signal multiplexing schemes. For example, a system may use (1) SC-FDMA (e.g., IFDMA, LFDMA or EFDMA) for the forward and reverse links, (2) one version of SC-FDMA (e.g., IIFDMA) for one link and another version of SC-FDMA (e.g. IFDMA) for another link, (3) MC-FDMA for the forward and reverse links, (4) SC-FDMA for one link (e.g., reverse link) and MC-FDMA (e.g. OFDMA) for another communication line (e.g., a direct communication line), or (5) some other combination of multiplexing schemes. SC-FDMA, OFDMA, some other multiplexing scheme, or combinations thereof, can be used for each link to achieve the desired performance. For example, SC-FDMA and OFDMA may be used for a given link with SC-FDMA used for some subbands and OFDMA used on other subbands. It may be desirable to use SC-FDMA on the reverse link to achieve low PAPR and ease amplifier power requirements for terminals. It may be desirable to use OFDMA on the forward link to potentially achieve a higher system capacity.

The methods described herein can be used to transmit information on the downlink or uplink. The methods can also be used for (1) an orthogonal multiple access system in which all users within a given cell or sector are orthogonal in time, frequency and / or code, and (2) a quasi-orthogonal multiple access system in which many users within one and the same cell or sector can transmit simultaneously on the same frequency at the same time. For clarity, much of what is described below is for the SC-FDMA quasi-orthogonal system, which is also called the Q-FDMA system. The Q-FDMA system supports spatial division multiple access (SDMA), which uses multiple antennas located at different points to support simultaneous transmissions for multiple users.

1 shows a Q-FDMA system 100 with multiple (M) transmitters 110a-110m and a receiver 150. For simplicity, each transmitter 110 is equipped with a single antenna 134, and the receiver 150 is equipped with multiple (R) antennas 152a-152r. For a forward link, each transmitter 110 may be part of a base station, and receiver 150 may be part of a terminal. For the reverse link, each transmitter 110 may be part of a terminal, and receiver 150 may be part of a base station. A base station is, in general, a stationary station and may also be called a base transceiver system (BTS), access point, or some other terminology. The terminal may be a fixed or mobile telephone and may be a wireless device, a cellular telephone, a personal digital assistant (PDA), a wireless modem card, and so on.

At each transmitter 110, a data and pilot processor (TX) 120 encodes, interleaves, and converts the traffic data and generates data symbols, which are modulation symbols for the traffic data. The modulation symbol is a complex value for a point in the aggregate signal, for example, for M-PSK or M-QAM. The processor 120 also generates pilot symbols, which are modulation symbols for the pilot. The SC-FDMA modulator 130 multiplexes the data and pilot symbols, performs SC-FDMA modulation (for example, for IFDMA, LFDMA, or EFDMA) and generates SC-FDMA symbols. The SC-FDMA symbol may be an IFDMA symbol, an LFDMA symbol, or an EFDMA symbol. The SC-FDMA data symbol is an SC-FDMA symbol for traffic data, and the SC-FDMA pilot symbol is an SC-FDMA symbol for pilot. Transmitter module (TMTR) 132 processes (e.g., converts to analog, amplifies, filters, and frequency converts) SC-FDMA symbols and generates a modulated radio frequency (RF) signal, which is transmitted through antenna 134.

At a receiver 150 R of antennas 152a-152r receive modulated RF signals from transmitters 110a-110m, and each antenna transmits the received signal to a coupled receiver module (RCVR) 154. Each receiver module 154 processes (eg, filters, amplifies, performs inverse frequency conversion and digitizes) its received signal and provides input samples to the spatial reception (RX) processor 160. Spatial reception processor 160 estimates the channel response between each transmitter 110 and R antennas based on a pilot received from this transmitter. Spatial reception processor 160 also performs reception spatial processing for each subband used by a plurality of transmitters to extract data symbols sent by these transmitters. The spatial reception processor 160 further demultiplexes the SC-FDMA symbols received for each transmitter. An SC-FDMA demodulator 170 (Demod) performs SC-FDMA demodulation for the detected SC-FDMA symbols for each transmitter and provides data symbol estimates for that transmitter. A received (RX) data processor 172 does a reverse mapping, deinterleaving, and decodes data symbol estimates for each transmitter, and provides decoded data for that transmitter. In general, processing by receiver 150 is complementary to processing by transmitters 110a-110m.

Controllers 140a-140m and controller 180 control the operation of various processors at transmitters 110a-110m and receiver 150, respectively. Memory units 142a-142m and memory 182 store program codes and data for transmitters 110a-110m and receiver 150, respectively.

System 100 may use TFDMA, LFDMA, or EFDMA for transmission. Subband structures and symbol generation for IFDMA, LFDMA, and EFDMA are described below.

2A shows an exemplary subband structure 200 for IFDMA. The full frequency band of the BW MHz system is divided into many (K) orthogonal subbands that are given 1-K indices, where K can be any integer value. For example, K can be equal to the power of two (for example, 64, 128, 256, 512, 1024, and so on), which can simplify the conversion between the frequency and time domains. The spacing between adjacent subbands is BW / K MHz. For simplicity, the following description assumes that all K full subbands are usable for transmission. For a structure of 200 subbands, K subbands are arranged in S disjoint, or non-overlapping, (intervals).

S intervals are disjoint in that each of the K subbands belongs to only one interval. In an embodiment, the interval comprises N subbands that are uniformly distributed across K common subbands, and consecutive subbands in the interval are divided by S subbands, where K = S * N. For this embodiment, the interval u contains u subbands, S + w, 2S + u ..., (N-1) -S + u, where u {1, .. S}. Index u is the interval index, as well as the subband offset, which indicates the first subband in the interval. In general, the subband structure may include any number of intervals, each interval may contain any number of subbands, and the interval may contain the same or different numbers of subbands. In addition, N may or may not be an integer divisor for K, and N subbands may or may not be uniformly distributed in K full subbands.

2B shows an exemplary subband structure 210 for LFDMA. For a subband structure 210, K full subbands are arranged in S non-overlapping groups. In an embodiment, each group contains N subbands that are adjacent to each other, and the group v contains subbands from (v-1) · N + 1 to v · N, where v is the index of the group and v ∈ {1 ... , S}. N and S for the subband structure 210 may be the same or different from N and S for the subband structure 200. In general, a subband structure may include any number of groups, each group may contain any number of subbands, and groups may contain the same or different numbers of subbands.

2C shows an exemplary subband structure 220 for EFDMA. For a subband structure 220, K full subbands are arranged in S non-overlapping sets, with each set containing G groups of subbands. In an embodiment, K full subbands are distributed across S sets as follows. K full subbands are first divided into a plurality of frequency ranges, where each frequency range contains K ′ = K / G consecutive subbands. Each frequency range is further divided into S groups, each group contains V consecutive subbands. For each frequency range, the first V subbands are allocated to set 1, the next V subbands are allocated to set 2, and so on, and the last V subbands are allocated to set S. Set s, for s = 1 ..., S contains subbands having indices k that satisfy the following: (s-1) · V≤k modulo (K / G) <s · V. Each set contains G groups of V consecutive subbands, or a total of N = G · V subbands. In general, a subband structure may include any number of sets, each set may contain any number of groups and any number of subbands, and the sets may contain the same or different number of subbands. For each set, groups can contain the same or different numbers of subbands and can be distributed uniformly or nonuniformly across the system bandwidth.

The SC-FDMA system may also use a combination of TFDMA, LFDMA, and / or EFDMA. In an embodiment, a plurality of slots (interlaces) may be formed for each group of subbands, and each slot may be allocated to one or more users for transmission. For example, two intervals may be formed for each group of subbands, the first interval may comprise subbands with evenly numbered indices, and the second interval may comprise subbands with indices with an odd number. In another embodiment, a plurality of subband groups may be formed for each slot, and each subband group may be allocated to one or more users for transmission. For example, two groups of subbands may be formed for each interval, the first group of subbands may contain lower subbands in the interval, and the second group of subbands may contain higher subbands in the interval. IFDMA, LFDMA, EFDMA, and combinations thereof can be considered as different versions of SC-FDMA. For each version of SC-FDMA, multiple users can transmit orthogonal pilot (pilot) signals on a given set of subbands (e.g., an interval or group of subbands), dividing the set of subbands into multiple subsets and assigning each user a corresponding subset for pilot transmission.

3A shows the generation of an IFDMA symbol for one slot, an LFDMA symbol for one group of subbands, or an EFDMA symbol for one set of subbands. The original sequence of N modulation symbols to be transmitted in one symbol period on an interval, a group of subbands, or a set of subbands, is denoted as {d1, d2, d3 ..., dN} (block 310). The original sequence is converted to the frequency domain by an N-point discrete Fourier transform (DFT) to obtain a sequence of N values of the frequency domain (block 312). N frequency-domain values are mapped onto N subbands used for transmission, and K-N zero values are mapped to the remaining K-N subbands to generate a sequence of K values (block 314). The N subbands used for transmission are in the same group of adjacent subbands for LFDMA (as shown in FIG. 3A), are in the same interval as the subbands distributed across K full subbands for TFDMA (not shown in FIG. 3A), and are in one set of multiple subband groups for EFDMA (also not shown in FIG. 3A). A sequence of K values is then converted into the time domain by a K-point inverse discrete Fourier transform (IDFT) to obtain a sequence of K output samples of the time domain (block 316).

The last C sequence output samples are copied to the beginning of the sequence to form an IFDMA, LFDMA, or EFDMA symbol that contains K + C output samples (block 318). C copied samples are often called a cyclic prefix or guard interval, and C is the length of the cyclic prefix. A cyclic prefix is used to combat intersymbol interference (ISI) caused by gradual frequency selective fading, which is a frequency response that varies across the system bandwidth.

FIG. 3B shows the generation of an IFDMA symbol for one slot for a case in which N is an integer divisor of K and N subbands are uniformly distributed across K full subbands. The original sequence of N modulation symbols to be transmitted in one symbol period over N subbands in the interval u is denoted as {d ₁ , d ₂ , d ₃ ..., d _N } (block 350). The original sequence is copied S times in order to obtain an extended sequence of K modulation symbols (block 352). N Modulation Symbols are sent in the time domain and collectively occupy N subbands in the frequency domain. S copies of the original sequence result in N occupied subbands separated by S subbands, with S-1 zero power subbands separating adjacent occupied subbands. The extended sequence has a comb-like frequency spectrum that spans interval 1 in FIG. 2A.

The expanded sequence is multiplied by a sawtooth phase signal in order to obtain a frequency-converted sequence K of output samples (block 354). Each output sample in a frequency-converted sequence can be generated as follows:

where d _n is the nth modulation symbol in the extended sequence, X _n is the nth output sample in the frequency-converted sequence, and u is the index of the first subband in the interval. Phase-like multiplication of the e- ^{j2π (n-1) · (u-1) / K} phase signal in the time domain converts the comb-like frequency spectrum for the extended sequence into frequency so that the frequency-converted sequence occupies the interval u in the frequency domain. The latter From the output samples of the frequency-converted sequence are copied to the beginning of the frequency-converted sequence in order to form an IFDMA symbol that contains K + C samples of the output samples (block 356).

The IFDMA symbol is periodic in the time domain (with the exception of a sawtooth phase signal) and therefore occupies N equally divided subbands starting from subband u. S TFDMA symbols may be generated with S different subband offsets. These S TFDMA symbols must occupy different intervals and, therefore, be orthogonal to each other.

The processing that is shown in FIG. 3A can be used to generate IFDMA, LFDMA and EFDMA symbols for any values of N and K. The processing that is shown in FIG. 3B can be used to generate IFDMA symbols for the case, in which N is an integer divisor of K and N subbands are uniformly distributed over K full subbands. The generation of the TFDMA symbol in FIG. 3B does not require a discrete Fourier transform or TDFT and may thus be preferred. 3A can be used to generate TFDMA symbols if N is not an integer divisor of K or if N subbands are not evenly distributed across K subbands. Symbols TFDMA, LFDMA and EFDMA can also be generated in other ways.

K + C output samples of an SC-FDMA symbol (which may be a TFDMA, LFDMA, or EFDMA symbol) transmit K + C in sample periods, one output sample in each sample period. The SC-FDMA symbol period (or simply the symbol period) is the duration of one SC-FDMA symbol and is equal to K + C sample periods. The sampling period is also called the frame period.

As is generally used here, a set of subbands is a set of subbands, which may be an interval for TFDMA, a group of subbands for LFDMA, or a set of groups of multiple subbands for EFDMA. For the reverse link, S users can simultaneously transmit data and pilot in S sets of subbands (eg, S intervals or S groups of subbands) to the base station, without interference with each other. Many users can also share a given set of subbands, and the base station can use a spatial processing receiver in order to isolate interfering transmission on this set of subbands. For a forward link, a base station can simultaneously transmit data and a pilot (pilot) signal over S sets of subbands to S users without interference.

4 shows a frequency hopping (FH) circuitry 400 that can be used for the forward and / or reverse link. Frequency hops can provide frequency diversity and randomization of interference from other cells or sectors. If there are frequency jumps, the user can be assigned a traffic channel that is associated with a jump (switch) pattern that indicates which set (s) of subbands, if any, to use in each time slot. The jump pattern is also called the FH pattern or sequence, and the time slot is also called the jump period. The time slot is the time spent on a given set of subbands and typically spans multiple symbol periods. The jump pattern may pseudo-randomly select different sets of subbands in different time slots. Frequency diversity is achieved by allocating all or many of the S sets of subbands over a number of time slots.

In an embodiment, one channel set is defined for each communication link. Each channel set contains S traffic channels that are orthogonal to each other so that no two traffic channels are mapped to the same set of subbands in any given time slot. This avoids intra-cell / intra-sector interference among users assigned to traffic channels in the same channel set. Each traffic channel is mapped to a specific sequence of time-frequency blocks, based on a hop pattern for that traffic channel. A time-frequency block is a specific set of subbands in a particular time slot. For this embodiment, S users can be assigned S traffic channels and they must be orthogonal to each other. Multiple users can also be assigned the same traffic channel, and these overlapping users can share the same sequence of time-frequency blocks and interfere with each other all the time. In this case, pilot signals for overlapping users can be multiplexed as described below, and data transmissions for these users can be separated using spatial processing for the receiver, as also described below.

In another embodiment, a plurality of channel sets may be defined for each communication link. Each channel set contains S orthogonal traffic channels. S traffic channels in each channel set may be pseudo-random with respect to S traffic channels in each of the remaining channel sets. This randomizes the interference among users assigned to traffic channels in different channel sets.

4 shows an exemplary mapping of traffic channel 1 in each channel set into a sequence of time-frequency blocks. Traffic channels 2-S in each channel set can be mapped to vertically and cyclically shifted versions of the time-frequency block sequence for traffic channel 1. For example, traffic channel 2 in channel set 1 can be mapped to set 2 of subbands in time slot 1, set 5 subbands in time slot 2, a set of 1 subbands in time slot 3, and so on.

In general, many users can be overlapped in a deterministic way (for example, sharing the same traffic channel), in a pseudo-random way (for example, when using two pseudo-random traffic channels), or a combination of both.

1. Control signal transmission

In quasi-orthogonal SC-FDMA, multiple transmitters can transmit on a given time-frequency block. Data transmissions from these transmitters can interfere with each other and can be separated using spatial processing for the receiver, even if these data transmissions are not orthogonal to each other. The pilot transmissions from these transmitters can be made orthogonal using TDMA, CDM, TFDM, LFDM, or some other multiplexing scheme. Orthogonal pilot (pilot) signals improve channel estimation, which can in turn improve data transmission efficiency, since channel estimates are used to restore data transmissions. In general, any number of transmitters (for example, 2, 3, 4, and so on) can share a given time-frequency block. For simplicity, the following description assumes that Q = 2, and control signal transmissions from two transmitters are multiplexed on the same time-frequency block. Also, for simplicity, only control signals for TFDMA and LFDMA are described below.

5 shows a TDMA pilot scheme. Transmitters 1 and 2 transmit data and a pilot signal on the same time-frequency block, which is composed of one set of N subbands in one time slot T symbol periods, where T> 1. For the example shown in FIG. 5, transmitter 1 transmits data in periods of 1 to t-1 characters, then a pilot signal in period t of characters, and then data in periods of t + 2 to T characters. The transmitter 1 does not transmit data or a pilot signal in a period of t + 1 characters. The transmitter 2 transmits data in periods of 1 to t-1 characters, then a pilot signal in a period of t + 1 characters, and then data in periods of t + 2 to T characters. The transmitter 2 does not transmit data or a pilot signal in a period of t symbols. Data transmissions from transmitters 1 and 2 interfere with each other. The pilot signal transmissions from transmitters 1 and 2 do not interfere with each other, and therefore, an improved channel estimate can be obtained for each transmitter. Each transmitter may transmit (1) an SC-FDMA data symbol in each symbol period determined for transmitting data, and (2) an SC-FDMA pilot symbol in each symbol period determined for transmission of a pilot signal. A TFDMA pilot symbol may be generated as shown in FIGS. 3A or 3B based on a sequence of N pilot symbols. The LFDMA pilot symbol may be generated, as shown in FIG. 3A, based on a sequence of N pilot symbols.

6 shows a CDM pilot scheme. For the example shown in FIG. 6, each transmitter transmits data in periods of 1 to t-1 characters, then a pilot signal in periods of t and t + 1 characters, and then data in periods of t + 2 to T characters. Transmitters 1 and 2 transmit a pilot signal simultaneously in periods of t and t + 1 characters. Each transmitter generates an SC-FDMA pilot symbol in a conventional manner, for example, as shown in FIG. 3A or 3B. The transmitter 1 is assigned an orthogonal pilot code from {+1, +1}, its SC-FDMA pilot symbol is multiplied by +1 for a period of t symbols, and the SC-FDMA pilot symbol is multiplied by +1 for a period of t + 1 characters. The transmitter 2 is assigned an orthogonal pilot code of {+ 1, -1}, its SC-FDMA pilot symbol is multiplied by +1 for a period of t symbols, and the SC-FDMA pilot symbol is multiplied by -1 for a period of t + 1 characters. The wireless channel is assumed to be static for periods of two characters used for pilot transmission. The receiver combines the received SC-FDMA symbols for periods t and t + 1 symbols to obtain the received SC-FDMA pilot symbol for transmitter 1. The receiver subtracts the received SC-FDMA symbol in the period t + 1 symbols from the received SC-FDMA symbol in a symbol period t to obtain a received SC-FDMA pilot symbol for transmitter 2.

For the embodiments shown in FIGS. 5 and 6, two symbol periods are used for TDMA or CDM pilots from two transmitters. Each transmitter transmits its pilot signal for one symbol period for the TDMA pilot circuit and for more than two symbol periods for the CDM pilot circuit. Each transmitter may have some maximum transmit power level that may be imposed by regulatory authorities or design constraints. In this case, the CDM pilot scheme allows each transmitter to transmit its pilot signal over a longer time interval. This allows the receiver to accumulate more energy for the pilot signal and to obtain a higher channel quality estimate for each transmitter.

7 shows a distributed / localized pilot signal circuit. For the example shown in FIG. 7, each transmitter transmits data in periods of 1 to t-1 characters, then a pilot signal in period t of characters, and then data in periods of t + 1 to T characters. Both transmitters 1 and 2 transmit a pilot signal simultaneously in a period of t symbols. However, the pilot signals for transmitters 1 and 2 are multiplexed using IFDM or LFDM, as described below, and do not interfere with each other. As used herein, a distributed pilot is a pilot sent over subbands that are distributed over an interval or a group of subbands, and a limited pilot is a pilot sent over adjacent subbands in a range or group of subbands. Distributed pilots for multiple users may be orthogonally multiplexed in a predetermined interval or group of subbands using TFDM. Limited pilots for multiple users may be orthogonally multiplexed in a predetermined interval or group of subbands using LFDM.

FIG. 8A shows a distributed pilot for TFDMA transmitters 1 and 2, which are also referred to as TFDMA distributed pilots. N subbands in the interval u are given indices 1-N and are divided into two subsets. The first subset contains subbands with odd-numbered indices, and the second subset contains subbands with even-numbered indices. The subbands in each subset are separated by 2S subbands, and the subbands in the first subset are offset by S subbands from the subbands in the second subset. Transmitter 1 is assigned a first subset with N / 2 subbands, and transmitter 2 is assigned a second subset with N / 2 subbands. Each transmitter generates a TFDMA pilot symbol for the assigned subset of the subband and transmits this TFDMA symbol over the subset of the subbands.

An IFDMA symbol for a distributed pilot may be generated as follows:

1. Form the initial sequence of N / 2 symbols of the control signal.

2. Copy the original sequence 2S times to generate an extended sequence with K pilot symbols.

3. Apply a sawtooth phase signal for the interval u, as shown in equation (1), to obtain a frequency-converted sequence.

4. Apply a cyclic prefix to the frequency converted sequence to generate the IFDMA pilot symbol.

Fig. 8B shows distributed pilot signals for transmitters 1 and 2 with LFDMA, which are also called distributed pilot signals LFDMA. N subbands in the group v subbands are given indices from 1 to N and are divided into two subsets. The first subset contains subbands with odd-numbered indices, and the second subset contains subbands with even-numbered indices. The subbands in each subset are separated by two subbands, and the subbands in the first subset are offset by one subband from the subbands in the second subset. Transmitter 1 is assigned a first subset with N / 2 subbands, and transmitter 2 is assigned a second subset with N / 2 subbands. Each transmitter generates an LFDMA pilot symbol for the assigned subset of the subbands and transmits this LFDMA symbol over the subset of the subbands.

The LFDMA symbol for a distributed pilot may be generated as follows:

1. Form the original sequence with N / 2 symbols of the control signal.

2. Perform a discrete Fourier transform on the N / 2 symbols of the pilot signal to obtain N / 2 values of the frequency domain.

3. Map N / 2 frequency domain values onto N / 2 pilot subbands in the assigned subset and map zero values to K-N / 2 remaining subbands.

4. Perform a K-point IDFT for the K values of the frequency domain and zero values to obtain a sequence of K output samples of the time domain.

5. Apply a cyclic prefix to the sequence in the time domain to generate the LFDMA pilot symbol.

Alternatively, an LFDMA symbol for a distributed pilot may be generated by copying an initial sequence of N / 2 pilot symbols to generate an extended sequence of N pilot symbols that can be processed as described above for FIG. 3A.

As shown in FIGS. 8A and 8B, the distributed pilots for transmitters 1 and 2 occupy different subsets of the subbands and therefore do not interfere with each other. The receiver performs complementary processing to recover the distributed pilot from each transmitter, as described below.

Fig. 9A shows a restricted pilot for IFDMA transmitters 1 and 2, which are also called IFDMA restricted pilots. N subbands in the interval u are given indices 1-N and are divided into two subsets. The first subset contains 1-N / 2 subbands in the lower half of the system bandwidth, and the second subset contains N / 2 + 1 - N subbands in the upper half of the system band. The subbands in each subset are separated by S subbands. Transmitter 1 is assigned a first subset with N / 2 subbands, and transmitter 2 is assigned a second subset with N / 2 subbands. Each transmitter generates an IFDMA pilot symbol for the assigned subset of the subbands and transmits this TFDMA symbol over the subset of the subbands.

An IFDMA symbol for a restricted pilot may be generated as follows:

1. Form the initial sequence of N / 2 symbols of the control signal.

2. Duplicate the original sequence S times to generate an extended sequence with K / 2 pilot symbols.

3. Perform a DFT for K / 2 pilot symbols to obtain K / 2 frequency domain values. N / 2 values of the frequency domain are nonzero, and the remaining values of the frequency domain are zero due to duplication of S times.

4. Display K / 2 values of the frequency domain so that N / 2 non-zero values of the frequency domain are sent on the N / 2 subbands of the pilot signal in the assigned subset.

5. Display zero values on the remaining subranges.

6. Perform a K-point TDFT for the K frequency domain and zero values in order to obtain a sequence of K output samples of the time domain.

7. Apply a cyclic prefix to the sequence in the time domain to generate the IFDMA pilot symbol.

Steps 3-6 above are similar to steps performed to generate an LFDMA symbol that is allocated to K / 2 subbands from K full subbands.

9B shows a restricted pilot for LFDMA transmitters 1 and 2, which are also referred to as restricted LFDMA pilots. The N subbands in the subband group v are given indices 1-N and are divided into two subsets. The first subset contains subbands from 1 to N / 2 in the lower half of the group of subbands, and the second subset contains subbands from N / 2 + 1 to N in the upper half of the group of subbands. The subbands in each subset are adjacent to each other. Transmitter 1 is assigned a first subset with N / 2 subbands, and transmitter 2 is assigned a second subset with N / 2 subbands. Each transmitter generates an LFDMA pilot symbol for its subset of subbands and transmits this LFDMA symbol over a subset of subbands.

The LFDMA symbol for a restricted pilot may be generated as follows:

1. Form the initial sequence of N / 2 symbols of the control signal.

2. Perform DFT on N / 2 pilot symbols to obtain N / 2 frequency domain values.

3. Map N / 2 frequency domain values onto N / 2 pilot subbands in the assigned subset and map zero values to K-N / 2 remaining subbands.

4. A K-point TDFT is performed for the K frequency domain and zero values to obtain a sequence of K output samples of the time domain.

5. Apply a cyclic prefix to the time domain sequence to generate the LFDMA pilot symbol.

Steps 1-5 above serve to generate an LFDMA symbol that is allocated to N / 2 subbands from K full subbands.

For clarity, exemplary methods for generating distributed pilot signals with IFDMA and LFDMA and generating restricted pilot signals with IFDMA and LFDMA have been described above. Distributed and limited control signals can also be generated in other ways. Distributed and limited pilot signals may also be generated for EFDMA, for example, by methods similar to those described above for IFDMA and LFDMA.

8A-9B show a case in which Q = 2 and each transmitter is assigned N / 2 subbands for pilot transmission. In general, N subbands in a given time-frequency block can be allocated to Q users in any way. Q users can be allocated the same number of subbands or a different number of subbands. Each user can be allocated N / Q subbands if Q is an integer divider of N or approximately N / Q subbands if Q is not an integer divider N. For example, if N = 16 and Q = 3, then 5 transmitters can be allocated to three transmitters. 5, and 6 subbands. The TFDMA pilot symbol or LFDMA pilot symbol for each transmitter may be generated as shown in FIG. 3A using a DTF based design.

The pilot subbands may be a subset of the data subbands, as described above for FIGS. 8A-9B. In general, pilot subbands may or may not be a subset of the data subbands. In addition, the pilot subbands may have the same or different (e.g., wide) frequency division than the data subbands.

In the description above, data and SC-FDMA pilot symbols have the same duration, and each SC-FDMA data symbol and each SC-FDMA pilot symbol are transmitted in K + C sample periods. SC-FDMA pilot data and symbols of various durations may also be generated and transmitted.

10 shows a transmission circuit 1000 with other data symbol and pilot lengths. For transmission circuit 1000, each symbol of SC-FDMA data is composed of N _D output samples that transmit in N _D sample periods, and each symbol of the SC-FDMA pilot signal consists of N _p output samples that transmit in N _p sample periods, where N _D > 1, N _p > 1 and N _D ≠ Np. For example, N _D may be equal to K + C, and N _p may be equal to K / 2 + C, K / 4 + C, and so on. As a specific example, K may be 512, C may be 32, N _D may be K + C = 544, and N _p may be K / 2 + C = 288. Each SC-FDMA data symbol may be a TFDMA data symbol that may be generated as shown in FIG. 3A or 3B, an LFDMA data symbol that may be generated as shown in FIG. 3A, or an EFDMA data symbol that may be generated as shown in FIG. 3A.

As an example, the SC-FDMA pilot symbol may have half the length of the SC-FDMA data symbol (not including the cyclic prefix). In this case, there are K / 2 full “wider” subbands for pilot, with each wider subband having a width twice that of the “normal” subband for traffic data.

For a truncated LFDMA symbol, a subband group consists of N / 2 wider subbands to which indices are assigned from 1 to N / 2. Transmitter 1 may be assigned a first subset of N / 4 wider subbands with even-numbered indices, and transmitter 2 may be assigned a second subset of N / 4 wider subbands with odd-numbered indices. A truncated LFDMA symbol for a distributed pilot may be generated as follows:

1. Form the initial sequence of N / 4 symbols of the control signal.

2. Perform DTF for N / 4 pilot symbols to obtain N / 4 frequency domain values.

3. Map N / 4 values of the frequency domain onto N / 4 wider subbands in the assigned subset and map zero values to the remaining wider subbands.

4. Perform a K / 2-point IDFT for K / 2 frequency domain values and zero values to obtain a sequence of K / 2 output time-domain samples.

5. Apply a cyclic prefix to the time domain sequence to generate a truncated LFDMA pilot symbol.

For LFDMA, the pilot and data from transmitters 1 and 2 are sent on the same subband group. N / 2 wider pilot subbands occupy the same part of the system bandwidth as N normal data subbands. For IFDMA, there is no direct mapping between the wider pilot subbands and the normal data subbands for a given interval. N wider pilot subbands may be formed at two slots and allocated to four transmitters assigned to these two slots. Each of these four transmitters can be assigned N / 4 wider pilot subbands that are evenly distributed across the system bandwidth. Each transmitter may generate a shortened (abbreviated) TFDMA symbol for a distributed pilot, for example, as described above for an abbreviated LFDMA pilot symbol, except that N / 4 frequency domain values are mapped to other wider pilot subbands.

Transmission circuit 1000 may be used to reduce the amount of loss for pilot. For example, a single pilot symbol period with a duration that is shorter than the data symbol period may be allocated for pilot transmission. Transmission circuit 1000 may also be used in combination with CDM. A plurality of (L) shorter pilot symbol periods may be allocated for pilot transmission, where L is the length of the orthogonal code used for the CDM pilot.

For clarity, TDMA, CDM, distributed and limited pilot schemes have been specifically described above for the simple case of two transmitters. In general, these pilot schemes can be used for any number of transmitters. For the TDMA pilot scheme, Q transmitters may be assigned different Q symbol periods used for pilot transmission, and each transmitter may transmit its pilot signal at its assigned symbol period. For the CDM pilot scheme, Q transmitters may be assigned different Q orthogonal codes for transmitting the pilot signal, and each transmitter may transmit its pilot signal using its assigned orthogonal code. For a distributed IFDMA pilot, the interval can be divided into Q subsets, each subset contains approximately N / Q subbands that can be evenly distributed across K full subbands and separated by Q · S subbands. For a distributed LFDMA pilot, a group of subbands can be divided into Q subsets, where each subset contains approximately N / Q subbands that can be divided by Q subbands. For the limited TFDMA pilot, the interval can be divided into Q subsets, where each subset contains approximately N / Q subbands that can be distributed across K / Q subbands and separated by S subbands. For a limited LFDMA pilot, a group of subbands can be divided into Q subsets, where each subset contains approximately N / Q adjacent subbands. In general, Q may or may not be an integer divisor of N, and each transmitter may be assigned any number of subbands and any of the subbands in a given set of subbands. For distributed and limited pilot schemes, each transmitter can transmit its pilot on its assigned subset of subbands.

Pilot symbols used to generate an SC-FDMA pilot symbol may be selected from a modulation scheme such as M-PSK, M-QAM, and so on. Pilot symbols may also be obtained based on a multi-phase sequence, which is a sequence that has good temporal characteristics (e.g., a constant envelope of the time domain) and good spectral characteristics (e.g., a flat frequency spectrum). For example, pilot symbols may be generated as follows:

where P is the number of pilot symbols. P is N for the TDMA and CDM pilot scheme, which are shown in FIGS. 5 and 6, respectively, and N / 2 for the exemplary distributed and limited pilot scheme that are shown in FIGS. 8A-9B. The phase φ _n can be obtained based on any of the following:

In equation (6), Q 'and P are coprime. Equation (3) is given for the Golomb sequence, equation (4) for the P3 sequence, equation (5) for the P4 sequence, and equation (6) for the Chu sequence. The sequences P3, P4, and Chu can be of any arbitrary length.

Pilot symbols can also be generated as follows:

The phase φ _{l, m} can be obtained based on any of the following:

Equation (8) is given for the Frank sequence, equation (9) for the sequence P1, and equation (10) for the sequence Px. The lengths for the Frank, P1, and Px sequences are bounded by P = T ² , where T is a positive integer.

11 shows a process 1100 performed by a transmitter to transmit a pilot and data in a Q-FDMA system. A set of N subbands selected from S sets of subbands is selected (block 1110). This set of subbands may comprise (1) data subbands that are used for data transmission, or (2) pilot subbands that must be shared by multiple transmitters for pilot transmission. For a distributed or limited pilot, a subset of P subbands assigned to transmit the pilot is selected, which is selected from among Q subsets of subbands formed with the assigned set of subbands (block 1112). For a TDMA or CDM pilot, the subset of the subbands assigned for pilot transmission is equal to the set of subbands assigned for transmission and P = N. For a distributed or limited pilot, Q> 1 and P may be equal to N / Q. The set of subbands and the subset of subbands can be determined in various ways depending on (1) the limited or distributed pilot is transmitted, (2) whether the system uses TFDMA, LFDMA, EFDMA, or the hybrid TFDMA / LFDMA / EFDMA, (3) whether data and SC-FDMA pilot symbols are the same or different durations, and so on. Steps 1110 and 1112 may be performed during each time slot if the Q-FDMA system uses a hopping frequency.

A pilot symbol sequence is generated, for example, based on a multi-phase sequence (block 1114). This sequence typically contains one pilot symbol for each subband used to transmit the pilot. For example, the sequence may contain N pilot symbols for TDMA or CDM with N pilot subbands or N / 2 pilot symbols for a distributed or limited pilot with N / 2 pilot subbands. Data symbols are also generated in the usual way (block 1116).

The SC-FDMA pilot symbol is generated with a sequence of pilot symbols and so that these pilot symbols occupy the subbands used for pilot transmission (block 1118). Data SC-FDMA symbols are generated with data symbols and so that these data symbols occupy the subbands used for transmission (block 1120). For the CDM pilot, a plurality of scalable SC-FDMA pilot symbols are generated based on the SC-FDMA pilot symbol and the orthogonal code assigned to the transmitter. The SC-FDMA data symbols are multiplexed with a pilot SC-FDMA symbol, for example, using TDM, as shown in FIGS. 5 or 7, or using CDM, as shown in FIG. 6 (block 1122). The multiplexed data and SC-FDMA pilot symbols are transmitted in the assigned time-frequency block (block 1124).

2. Channel Rating

Referring again to FIG. 1, in a receiver 150, a channel estimator for each receive antenna 152 estimates a channel response between each transmitter and this receive antenna. Multiple (Q) transmitters can share the same time-frequency block and can multiplex their pilots using TDM, CDM, TFDM or LFDM, as described above. Each channel estimation block performs complementary demultiplexing and obtains a channel estimate for each of the Q transmitters sharing this time-frequency block.

12 shows a process 1200 performed by a channel estimator for each receive antenna to estimate a wireless channel response (response) for each transmitter based on a pilot received from that transmitter. For clarity, channel estimation for a single time-frequency block shared by Q transmitters is described below.

The channel estimator receives the SC-FDMA symbol for the associated antenna in each symbol period and cancels the TDM or CDM performed for the pilot (block 1210). For the TDMA pilot scheme, which is shown in FIG. 5, Q received SC-FDMA pilot symbols are received in Q symbol periods from Q transmitters, and the received SC-FDMA pilot symbol for each transmitter is processed to obtain a channel estimate for this the transmitter. For the CDM pilot scheme, which is shown in FIG. 6, Q received SC-FDMA symbols containing CDM pilots from Q transmitters are multiplied by Q orthogonal codes assigned to these transmitters and accumulated to obtain Q received pilot symbols SC-FDMA signal for Q transmitters. For the distributed and limited pilot schemes, which are shown in FIGS. 7-9B, one received SC-FDMA pilot symbol can be received in one symbol period for Q transmitters, and the received SC-FDMA pilot symbol is processed to obtain channel estimate for each of the Q transmitters.

The channel estimator removes the cyclic prefix in each received SC-FDMA symbol and obtains K input samples for this received SC-FDMA symbol (block 1212). The channel estimator then performs a K-point DTF for K input samples for each received SC-FDMA symbol and obtains K received frequency-domain values for this received SC-FDMA symbol (block 1214). The channel estimator performs channel estimation for the received pilot values obtained from the received SC-FDMA pilot symbol (s). The channel estimator also provides, on the RX (receiving) spatial processor 160, the values of the received data obtained from the received SC-FDMA symbol data. For clarity, channel estimation for one transmitter m is described below.

The pilots from the Q transmitters are orthogonal to each other due to the use of TDMA, CDM, IFDM or LFDM. The received pilot values for transmitter m can be defined as:

where P _m (k) is the value of the control signal sent by the transmitter m in the subband k;

H _{m, r} (k) is the complex gain for the wireless channel between the transmitter m and the receiving antenna r for subband k;

R _r ^P (k) is the received value of the pilot signal from the receiving antenna r for subband k;

N _r (k) is the noise at the receiving antenna r for subband k, and

K _p is a subset of P subbands of control signals.

For simplicity, the noise can be thought of as additive white Gaussian noise (AWGN) with a mean of zero and a variance of N ₀ .

The K-point DTF in step 1214 provides K received values for K full subbands. Only P received pilot values for the P pilot subbands used by transmitter m are stored, and the remaining K-P received values are discarded (block 1216). P is N for TDMA and CDM pilot schemes and N / Q for distributed and limited pilot schemes. Different pilot subbands are used for TDMA, CDM, distributed and limited pilot schemes, and therefore different received pilot values are stored for different pilot schemes. In addition, different pilot subbands are used by different transmitters for a distributed and limited pilot scheme, and therefore different received pilot values are stored for different transmitters.

The channel estimator may estimate the channel frequency response for the transmitter m using various channel estimation methods, such as MMSE method, least squares (LS) method, and so on. The channel estimator obtains P channel gain estimates for the P pilot subbands used by transmitter m based on the P received pilot values for these subbands and using MMSE or LS methods (Step 1218). For the MMSE method, an initial estimate of the frequency response can be obtained based on the received pilot values, as follows:

- оценка коэффициента усиления канала между передатчиком m и приемной антенной r для субдиапазона k, и "*" обозначает комплексное сопряжение. Для способа LS, начальная оценка частотного отклика может быть получена следующим образом:Where

- an estimate of the channel gain between the transmitter m and the receiving antenna r for the subband k, and "*" indicates the complex conjugation. For the LS method, an initial estimate of the frequency response can be obtained as follows:

для n=1...,L, может быть получена, основываясь на начальной оценке частотного отклика, следующим образом:The initial frequency response estimate comprises P channel gains for P pilot subbands. The impulse response of the wireless channel can be characterized by signals L, where L can be less than P. An estimate of the impulse response of the channel for transmitter m can be obtained based on P estimates of the channel gain and using the least squares (LS) method or MMSE method (step 1220). Evaluation of the channel impulse response by the least squares method with L signals,

for n = 1 ..., L, can be obtained based on the initial estimate of the frequency response, as follows:

является вектором P×1, содержащим

или

для k∈K';Where

is a vector P × 1 containing

or

for k∈K ';

- подматрица матрицы

коэффициентов Фурье;

- submatrix of the matrix

Fourier coefficients;

является вектором L×1, содержащим

для n=1..., L; и

is an L × 1 vector containing

for n = 1 ..., L; and

“H” means conjugate transposition.

коэффициентов Фурье определена так, что (u, v)-я запись, f_u,v, определяется как:Matrix

Fourier coefficients are defined so that the (u, v) th record, f _{u, v} , is defined as:

содержит P строк

соответствующие P субдиапазонам контрольного сигнала. Каждая строка

содержит первые L элементов соответствующей строки

содержит L сигналов (отводов) оценки импульсного отклика канала способом наименьших квадратов.

contains P lines

corresponding to the P subbands of the pilot signal. Each line

contains the first L elements of the corresponding row

contains L signals (taps) for estimating the impulse response of the channel using the least squares method.

для n=1...,L, может быть получена следующим образом:Evaluation of the impulse response of the MMSE channel with L signals,

for n = 1 ..., L, can be obtained as follows:

является L×L автокорреляционной матрицей дисперсии шума и интерференции. Для AWGN,

может быть определено, как

где N₀ является дисперсией шума. P-точечное TDFT может также быть выполнено в отношении начальной оценки частотного отклика, чтобы получить оценку импульсного отклика канала с P сигналами.Where

is the L × L autocorrelation matrix of noise variance and interference. For AWGN,

can be defined as

where N ₀ is the dispersion of noise. A P-point TDFT may also be performed with respect to the initial frequency response estimate to obtain a channel impulse response estimate with P signals.

The channel estimator may perform filtering and / or post-processing on the initial frequency response estimate and / or channel impulse response estimate in order to improve the quality of the channel estimate (block 1222). Filtering can be based on a filter with a finite impulse response (FIR), a filter with an infinite impulse response (TTR), or some other type of filter. In an embodiment, the truncation can be performed so as to save only the first L signals (taps) of the channel impulse response estimate and replace the remaining signals (taps) with zeros. In another embodiment, setting a threshold value may be performed to nullify channel signals having low energy below a predetermined threshold. The threshold can be calculated based on the energy of all P signals or only the first L signals of the channel impulse response estimate. In yet another embodiment, a signal selection may be made in order to maintain B best channel signals and nullify the remaining channel signals.

The channel estimator can obtain a final estimate of the frequency response (frequency response) for N subbands in the time-frequency block by (1) padding the zeros of the impulse response of the L-signal or P-signal channel to a length N, and (2) performing N- point DTF for extended impulse response assessment (block 1224). The channel estimator may also obtain a final estimate of the frequency response for the N subbands by (1) interpolating P channel gain estimates, (2) performing the least squares approximation on the P channel gain estimates, or (3) using other approximation methods.

An estimate of the frequency response and / or an estimate of the channel impulse response for the wireless channel can also be obtained by other methods using other channel estimation methods.

3. Spatial multiplexing

ответа канала для каждого субдиапазона, который может быть выражен как:Referring again to FIG. 1, where a single input channel - many outputs (SIMO) is formed between a single antenna in each transmitter 110 and R antennas in receiver 150. SIMO channel for transmitter m, for m = 1 ..., M, can be characterized by the vector R × I

channel response for each subband, which can be expressed as:

, для r=1...,R, является связанным или комплексным коэффициентом усиления канала между единственной антенной в передатчике 110m и R антеннами в приемнике 150 для субдиапазона k в слоте времени t. Другой канал SIMO сформирован между каждым передатчиком и приемником. Векторы ответа канала для М передатчиков 110a-110m могут быть обозначены как

-

соответственно.Where

, for r = 1 ..., R, is the coupled or complex channel gain between a single antenna at transmitter 110m and R antennas at receiver 150 for subband k in time slot t. Another SIMO channel is formed between each transmitter and receiver. Channel response vectors for M transmitters 110a-110m may be denoted as

-

respectively.

, где “

” обозначает оператор округления сверху, который обеспечивает целочисленное значение, которое является равным или большим чем x. Если множество (Q) наборов канала используются для М передатчиков, то каждый передатчик наблюдает помехи от большинства Q-1 других передатчиков в любой заданный момент и является ортогональным к по меньшей мере M-(Q-1) другим передатчикам.If the number of transmitters selected for transmission (M) is less than or equal to the number of traffic channels in one set of channels (or M≤S), then M transmitters can be assigned different traffic channels in one set of channels. If the number of transmitters is greater than the number of traffic channels in one channel set (or M> S), then these transmitters can be assigned traffic channels from the smallest number of channel sets. The minimum number of channel sets (Q) required to support M transmitters can be defined as Q =

where “

”Denotes a rounding operator on top that provides an integer value that is equal to or greater than x. If multiple (Q) channel sets are used for M transmitters, then each transmitter observes interference from most Q-1 other transmitters at any given moment and is orthogonal to at least M- (Q-1) other transmitters.

For a Q-FDMA system, up to Q transmitters can share a given time-frequency block. For a Q-FDMA system with frequency jumps, a given transmitter transmits on different sets of subbands to different time slots and shares time-frequency blocks with other transmitters over time due to the pseudo-random nature of frequency jumps. For simplicity, the following description is for a single time-frequency block shared by transmitters from 1 to Q.

(k, t) R×Q ответа канала для каждого субдиапазона в частотно-временном блоке, которая может быть выражена как:A multi-input-many-output (MIMO) channel is formed between Q transmitters sharing the same time-frequency block and receiver 150. The MIMO channel can be characterized by a matrix

(k, t) R × Q channel response for each subband in the time-frequency block, which can be expressed as:

(k, t) для каждой антенны передатчика. Эти множество передач от передатчика с множеством антенн могут быть обработаны таким же образом, как и множество передач от множества передатчиков с единственной антенной.where K _d is the set of subbands for the time-frequency block. In general, each transmitter may be equipped with one or multiple antennas. A multi-antenna transmitter can transmit various SC-FDMA symbol streams from multiple antennas, and then should have one channel response vector per

(k, t) for each transmitter antenna. These multiple transmissions from a transmitter with multiple antennas can be processed in the same way as many transmissions from multiple transmitters with a single antenna.

Each of the Q transmitters can transmit data and pilot using TFDMA, LFDMA, or EFDMA. Receiver 150 processes the input samples from the R antennas of the receiver and receives received data values. The received data values for each subband k in each symbol period n of the time slot t can be expressed as:

(k,t,n) - вектор Q×1 с Q значениями данных, посланными Q передатчиками на субдиапазоне k в период n символа слота времени t;Where

(k, t, n) is a Q × 1 vector with Q data values sent by Q transmitters on the subband k in the period n of the symbol of the time slot t;

(k,t,n) - вектор R×1 с R принятыми значениями данных, полученными через R приемных антенн для субдиапазона k в период n символа слота времени t; и

(k, t, n) is an R × 1 vector with R received data values obtained through R receiving antennas for subband k in the period n of the symbol of the time slot t; and

(k,t,n) - вектор шума для субдиапазона k в период n символа слота времени t.

(k, t, n) is the noise vector for subband k in the period n of the symbol of the time slot t.

(k,t) ответа канала, как предполагается, является постоянной для всего слота времени и не является функцией периода n символа.For simplicity, the matrix

(k, t) of the channel response is assumed to be constant for the entire time slot and is not a function of the symbol period n.

(k,t,n) для

сформированы Q передатчиками для N субдиапазонов в каждый период n символа слота времени t. Каждый вектор

(k,t,n) содержит Q значений данных, посланных Q передатчиками на субдиапазоне k в период n символа слота времени t.N transfer vectors

(k, t, n) for

formed by Q transmitters for N subbands in each period n symbols of the time slot t. Every vector

(k, t, n) contains Q data values sent by Q transmitters on subband k in period n of the symbol of time slot t.

(k,t,n) для

получены для N субдиапазонов в каждый период n символа каждого временного слота t. Каждый вектор

(k,t,n) содержит R значений принятых данных, полученные посредством R антенн в приемнике 150 для одного субдиапазона за один период символа. Для заданного субдиапазона k, периода n символа и слота времени t, j-е значение данных в векторе

(k,t,n) умножается на j-ый вектор/столбец матрицы H(M) ответа канала для того, чтобы сгенерировать вектор

(k,t,n). Q значений данных в

(k,t,n), которые посланы различными Q передатчиками, умножают на Q столбцов

(k,t), чтобы сгенерировать Q векторов

(k,t,n) -

(k,t,n), один вектор для каждого передатчика. Вектор

(k,t,n), полученный приемником 150, составлен из линейной комбинации Q векторов

(k,t,n) -

(k,t,n), или

Каждое принятое значение данных в

(k,t,n) содержит, таким образом, компонент каждого из Q переданных значений данных в

(k,t,n). Q значений данных, посланные одновременно Q передатчиками на каждом субдиапазоне k в каждый период n символа слота времени t таким образом оказывают помехи друг на друга в приемнике 150.N receive vectors

(k, t, n) for

obtained for N subbands in each period n symbols of each time slot t. Every vector

(k, t, n) contains R values of received data obtained by R antennas at receiver 150 for one subband in one symbol period. For a given subrange k, symbol period n and time slot t, the jth data value in the vector

(k, t, n) is multiplied by the jth vector / column of the channel response matrix H (M) in order to generate a vector

(k, t, n). Q data values in

(k, t, n), which are sent by different Q transmitters, are multiplied by Q columns

(k, t) to generate Q vectors

(k, t, n) -

(k, t, n), one vector for each transmitter. Vector

(k, t, n) obtained by receiver 150 is composed of a linear combination of Q vectors

(k, t, n) -

(k, t, n), or

Each accepted data value in

(k, t, n) thus contains the component of each of the Q transmitted data values in

(k, t, n). Q data values sent simultaneously by Q transmitters on each subband k in each period n of the symbol of the time slot t thus interfere with each other in the receiver 150.

Receiver 150 may use various methods of receiver spatial processing at the receiver to separate data transmissions sent simultaneously by Q transmitters on each subband in each symbol period. These methods for spatial processing of reception at the receiver include a method of zeroing (ZF), an MMSE method, and a maximum ratio combining (MRC) method.

Receiver 150 may obtain a spatial filter matrix based on the ZF, MMSE, or MRC method, as follows:

(k,t) ответа канала для каждого субдиапазона, основываясь на контрольных сигналах, принятых от Q передатчиков. Для ясности, данное описание не предполагает никакой ошибки оценки канала. Приемник 150 затем использует матрицу

(k,t) ожидаемого ответа канала, чтобы получить матрицу пространственного фильтра. Поскольку

(k,t), как предполагается, является постоянной в слоте времени t, та же самая матрица пространственного фильтра может использоваться в течение всех периодов символа в слоте времени t.The receiver 150 may evaluate the matrix

(k, t) a channel response for each subband based on pilot signals received from Q transmitters. For clarity, this description does not imply any channel estimation error. Receiver 150 then uses a matrix

(k, t) the expected channel response to obtain a spatial filter matrix. Insofar as

(k, t) is assumed to be constant in the time slot t, the same spatial filter matrix can be used for all symbol periods in the time slot t.

The receiver 150 may perform spatial processing of the reception as follows:

(k,t) может равняться

_zf(k,t),

_mmse(k,t), или

_mrc(k,t);Where

(k, t) may equal

_zf (k, t),

_mmse (k, t), or

_mrc (k, t);

(k, t, n) is an L × 1 vector with L detected data values for subband k in the period n of the symbol of the time slot t; and

(k,t,n) - шум после пространственной обработки в приемнике.

(k, t, n) is the noise after spatial processing at the receiver.

The detected data value is an estimate of the transmitted data value.

_mmse(k,t) и пространственного фильтра MRC

_mrc(k,t) являются ненормализованными оценками значений данных в

(k,t,n). Перемножение с матрицей масштабирования

_mmse(k,t) или

_mrc (k,t) обеспечивает нормализованные оценки значений данных.Estimates from the MMSE spatial filter

_mmse (k, t) and spatial filter MRC

_mrc (k, t) are abnormal estimates of data values in

(k, t, n). Scaling matrix multiplication

_mmse (k, t) or

_mrc (k, t) provides normalized estimates of data values.

(k,t) отклика канала для каждого субдиапазона в каждом временном слоте определяется набором передатчиков, использующих этот субдиапазон в этом слоте времени и содержит один или более векторов/столбцов для каждого передатчика, передающего в этом субдиапазоне в этом слоте времени. Матрица

(k,t) может содержать множество векторов для передатчика, использующего множество антенн для того, чтобы передать различные потоки на приемник 150.In general, different sets of transmitters may be assigned different sets of subbands in a given time slot, for example, as determined by their hop patterns. S sets of transmitters assigned to S sets of subband in a given time slot may contain the same or different numbers of transmitters. In addition, each set of transmitters may contain transmitters with one antenna, transmitters with multiple antennas, or a combination of both. Different sets of transmitters can also be assigned to a given set of subbands in different time slots. Matrix

The (k, t) channel response for each subband in each time slot is determined by the set of transmitters using this subband in this time slot and contains one or more vectors / columns for each transmitter transmitting in that subband in this time slot. Matrix

(k, t) may comprise multiple vectors for a transmitter using multiple antennas in order to transmit various streams to receiver 150.

_m(k,t) отклика канала. Это позволяет системе Q-FDMA обладать более высокой емкостью.As shown above, a plurality of data transmissions sent simultaneously by Q transmitters on each subband k in each symbol period n of each time slot t may be allocated by receiver 150 based on their spatial signatures, which are defined by their vectors

_m (k, t) of the channel response. This allows the Q-FDMA system to have a higher capacity.

Q-FDMA can be used for forward and reverse links. For the reverse link, multiple terminals can transmit simultaneously on the same time-frequency block to a base station with multiple antennas, which can allocate transmissions from these terminals using the spatial reception processing techniques described above. For a forward link, a multi-antenna base station can obtain channel estimates for all terminals (for example, based on the pilot signals transmitted by these terminals) and perform transmitter spatial processing for transmissions sent to these terminals. For example, the base station may perform transmitter spatial processing for terminal m as follows:

where s _m (k, t, n) is the data symbol to be sent to terminal m in subband k during the period of symbol n of time slot t; and

_m(k,t,n) - вектор R×1 с R символами передачи, которые должны быть посланы через антенны R терминалу m на субдиапазоне k в период символа n слота времени t.

_m (k, t, n) is an R × 1 vector with R transmission symbols to be sent via antennas R to terminal m on subband k during the period of symbol n of time slot t.

Equation (24) shows the spatial processing of the transmission using beamforming MRC. The base station may also perform another type of spatial processing of the transmission. For example, a base station can transmit to two users simultaneously using zero directional beamforming and can generate a beam for the first user so that another user lies at the zero of that beam and does not observe any interference from the first user.

On a forward link, a multi-antenna terminal may receive transmissions from multiple base stations. Each base station can transmit to the terminal using various hop patterns assigned to the terminal by that base station. The hop patterns assigned by various base stations to the terminal may overlap. Whenever this happens, the terminal can use receiver spatial processing to extract multiple transmissions sent simultaneously on the same subband to the same symbol period by these base stations.

Q-FDMA can also be used to improve performance during handoff. Terminal A can be transmitted from base station 1 to base station 2. During the switching of communication channels, base station 2 can receive transmission from terminal A on subbands that overlap (overlap with) the subbands assigned to another terminal B exchanging with base station 2 Base station 2 may perform spatial processing for the receiver in order to separate transmissions from terminals A and B. Base station 1 or 2 may also combine information (eg, values of detected data) received two base stations for Terminal A, which is a process known as “soft handoff” to improve performance. Base station 1 and 2 may also send an orthogonal pilot to terminal A. The network may be designed such that pilot signals for the forward link and / or reverse link in different sectors are orthogonal to each other.

Orthogonal pilots can be sent on the forward and reverse links to facilitate channel estimation. Multiple terminals sharing the same time-frequency block can send orthogonal pilots to a given base station. Many base stations can also send an orthogonal pilot signal to a given terminal, for example, during switching of communication channels. Orthogonal pilot signals may be sent using any of the pilot signal transmission schemes described herein.

4. Transmission H-ARO

The Q-FDMA system may use Hybrid Automatic Repeat Request (H-ARQ), which is also called increased redundancy (IR) transmission. With H-ARQ, the transmitter sends one or many transmissions for the data packet until the packet is correctly decoded by the receiver, or until the maximum number of transmissions is sent. H-ARQ improves reliability for data transmission and supports adaptation of the transmission rate for packets in the presence of changes in channel conditions.

13 shows H-ARQ transmission. The transmitter processes (for example, encodes and modulates) a data packet (Packet 1), and generates a plurality of (B) data blocks, which may also be called frames or subpackets. Each data block may contain sufficient information to allow the receiver to correctly decode the packet under favorable channel conditions. Data blocks B contain various redundancy information for the packet. Each data block can be sent in any number of time slots. For the example shown in FIG. 13, each data block is sent in one time slot.

The transmitter transmits the first data block (Block 1) for packet 1 in time slot 1. The receiver receives and processes (for example, demodulates and decodes) block 1, determines that packet 1 is decoded in error, and sends a negative acknowledgment (NAK) to the transmitter in the slot 2. The transmitter receives a NAK and transmits a second data block (Block 2) for packet 1 in time slot 3. The receiver receives a block 2, processes blocks 1 and 2, determines that packet 1 is still decoded with an error, and sends a NAK in the slot 4. Transmission of the unit and NAK response may continue anyway. number of times. For the example shown in FIG. 13, the transmitter transmits a data block x (Block x) for Packet 1 in the time slot t, where x≤B. The receiver receives Block x, processes Blocks 1-x for Packet 1, determines that the packet is decoded correctly, and sends back the ACK in time slot 2b. The transmitter receives the ACK and ends the transmission of Packet 1. The transmitter processes the next data packet (Packet 2) and transmits the data blocks for Packet 2 in a similar way.

13, there is a delay of one time slot for an ACK / NAK response for each block transmission. To improve channel utilization, a transmitter may transmit multiple packets in an interlaced fashion. For example, a transmitter may transmit one packet in an odd-numbered time slot, and another packet in an even-numbered time slot. More than two packets can also be interleaved for longer ACK / NAK latency.

13 shows NAK and ACK transmission. For an ACK based scheme, an ACK is sent only if the packet is decoded correctly and NAK is not sent and is assumed to be missing ACK.

14 shows H-ARQ transmissions for two frequency hopping transmitters a and b. Each transmitter can transmit a new packet starting in any time slot. Each transmitter may also transmit any number of data blocks for each packet and may transmit another packet after receiving an ACK for the current packet. Packets transmitted by each transmitter thus appear asynchronous with respect to packets transmitted by other transmitters. In frequency jumps, each transmitter transmits in a sequence of time-frequency blocks. Each transmitter may interfere with other transmitters in a pseudo-random manner if these transmitters are assigned traffic channels in different channel sets, as shown in FIG. Multiple transmitters may also interfere with each other in each time-frequency block if they are assigned the same traffic channel (not shown in FIG. 14).

The receiver receives block transmissions from the transmitters and performs receiver spatial processing for each time-frequency block with block transmissions from multiple transmitters. The receiver demodulates and decodes each packet based on all data symbol estimates obtained for all block transmissions received for that packet . For each packet that is correctly decoded, the H-ARQ transmission for this packet can be terminated, and interference due to this packet can be estimated and subtracted from the input samples or received data values for the time-frequency block (s) used by this packet . An interference estimate can be obtained, for example, by encoding and modulating the packet in the same manner as the transmitter did, and multiplying the resulting symbols by the channel estimates for the packet. The receiver can perform receiver spatial processing on symbols canceled due to interference for all time-frequency blocks used by correctly decoded packets to obtain new data symbol estimates for packets that are decoded in error and transmitted on the same time frequency blocks as correctly decoded packets. Each packet that is decoded in error and overlapping at least partially (that is, sharing any time-frequency block) with any correctly decoded packet can be demodulated and decoded based on all estimates of the data symbol for that packet.

5. Transmitter and Receiver

15 shows an embodiment of a transmitter 110m. In a data and processor (TX) and pilot processor 120m, an encoder 1512 receives traffic data, encodes each data packet based on an encoding scheme, generates an encoded packet, and splits each encoded packet into multiple data blocks. An interleaver 1514 interleaves or reorders each data block based on an interleaving scheme. A symbol mapper 1516 converts the interleaved bits in each data block into data symbols based on a modulation scheme. The pilot generator 1520 generates pilot symbols, for example, based on a multi-phase sequence. The TDM / CDM module 1522 multiplexes data symbols with pilot symbols using TDM (for example, as shown in FIG. 5 or 7) or CDM (for example, as shown in FIG. 6). Data and pilot symbols may also be multiplexed after SC-FDMA modulation.

In the controller / processor 140m, the FH generator 1542 determines a set of subbands to use for transmission in each time slot, for example, based on a hop pattern assigned to the transmitter 110m. For distributed and limited pilots, the controller / processor 140m also determines a subset of the subbands to use for pilot transmission. For example, transmitters that have been assigned traffic channels in a set of 1 channels may be assigned a first subset, transmitters that have been assigned traffic channels in a set of 2 channels may be assigned a second subset, and so on. The SC-FDMA modulator 130m generates SC-FDMA symbol data so that the data symbols are sent in the set of subbands used for transmission. The SC-FDMA modulator 130m also generates SC-FDMA pilot symbols such that pilot symbols are sent in a subset of the subbands used for pilot transmission.

FIG. 16 shows an embodiment of a receiver 150. At a receiver 150, R DTF modules 1610a through 1610r receive input samples from receiver modules 154a through 154r for R receive antennas, respectively. Each DTF module 1610 performs discrete Fourier transforms on input samples during each symbol period to obtain frequency domain values during that symbol period. R demultiplexer / channel estimator units 1620a through 1620r receive frequency domain values from DTF modules 1610a through 1610r, respectively. Each demultiplexer 1620 provides frequency domain values for data (or received data values) to K subband spatial processors 1632a-1632k.

(k,t) ответа канала для каждого субдиапазона в каждом временном слоте, основываясь на векторах ответа канала для всех передатчиков, используя этот субдиапазон и временной слот. Модуль 1634 вычисления затем получает матрицу

(k,t) пространственного фильтра для каждого субдиапазона каждого временного слота, основываясь на матрице

(k,t) ответа канала для этого субдиапазона и временного слота, как описано выше. Модуль 1634 вычисления обеспечивает K матриц пространственного фильтра для K субдиапазонов в каждом временном слоте.Each channel estimator 1620 obtains a channel estimate for each transmitter based on frequency domain values for the pilot (or received pilot) obtained for that transmitter. The spatial filter matrix calculation module 1634 generates a matrix

(k, t) a channel response for each subband in each time slot, based on the channel response vectors for all transmitters using this subband and time slot. The calculation module 1634 then obtains a matrix

(k, t) spatial filter for each subband of each time slot, based on the matrix

(k, t) a channel response for this subband and time slot, as described above. Calculation module 1634 provides K spatial filter matrices for K subbands in each time slot.

K spatial sub-band processors 1632a-1632k receive received data values for subbands 1-K, respectively, from demultiplexers 1620a-1620r. Each subband spatial processor 1632 also obtains a spatial filter matrix for its subband, performs receiver spatial processing for the received data values with the spatial filter matrix, and provides detected data values. During each symbol period, K spatial processors 1632a-1632k provide K vectors of detected data values for K subbands to demultiplexer 1636 (Demux). The demultiplexer 1636 maps the values of the detected data for each transmitter to the detected SC-FDMA symbols. The detected SC-FDMA symbol for a given transmitter m is the SC-FDMA symbol that is received by receiver 150 for this transmitter with interference from other transmitters suppressed by receiver spatial processing.

An SC-FDMA demodulator 170 processes each detected SC-FDMA symbol and provides data symbol estimates to an RX (receive) processor 172. The SC-FDMA 170 demodulator can perform alignment, removal of a sawtooth phase signal for TFDMA, reverse mapping of symbols from the assigned subbands, and so on. The SC-FDMA 170 demodulator also maps the data symbol of the m transmitters to m streams based on the traffic channels assigned to these transmitters. An FH generator 1642 determines the subbands used by each transmitter based on a hop pattern assigned to that transmitter.

An RX (received) symbol processor 172 performs inverse mapping, deinterleaving, and decodes the data symbol estimates for each transmitter, and provides decoded data, as well as a decoding state, for each decoded packet. Controller 180 may generate ACK and / or NAK based on the decoding state, and may send ACK and / or NAK back to the transmitters to control the transmission of data blocks for H-ARQ.

The methods described herein can be carried out by various means. For example, these methods may be implemented in hardware, software, or a combination thereof. For hardware implementation, the processor modules used to perform the control channel transmission, channel estimation, receive spatial processing, and so on, can be implemented in one or more specialized integrated circuits (ASICs), digital signal processors (DSPs), digital processing devices Signals (DSPD), Programmable Logic Devices (PLD), Field Programmable Gate Arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices ah, other electronic units designed to perform the functions described herein, or combinations thereof.

For software implementation, the methods may be implemented by modules (eg, procedures, functions, and so on) that perform the functions described herein. Software codes may be stored in a memory module (e.g., memory module 142 or 182 in FIG. 1) and executed by a processor (e.g., controller 140 or 180). The memory module may be implemented in the processor or external to the processor.

Headings are included here for reference and assist in locating specific sections. These headings are not intended to limit the scope of the concepts described below, and these concepts may be applicable in other sections throughout the specification.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited by the embodiments shown here, but should receive the broadest possible capabilities consistent with the principles and new features disclosed herein.

Claims (28)

1. A wireless communication device, comprising:
a first processor adapted to:
select a subband from a set of subranges;
generate a first pilot symbol sequence for transmission in a subband, the pilot symbols being orthogonal and adapted to alternate with a second symbol sequence generated in the second processor; and
generate a first sequence of data symbols, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor; and
a transmitter connected to the first processor for transmitting a first pilot symbol sequence and a first data symbol sequence. 2. The apparatus of claim 1, wherein the first pilot symbol sequence is a single carrier frequency division multiple access (SC-FDMA) symbol sequence. 3. The device according to claim 1, in which the first sequence of data characters is a sequence of SC-FDMA characters. 4. A wireless communication method, comprising the steps of:
selecting a subband from a set of subbands;
generating a first pilot symbol sequence for transmission in the subband, the pilot symbols being orthogonal to the second pilot symbol sequence and adapted to alternate with a second symbol sequence generated in the second processor;
generating a first sequence of data symbols, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor; and
transmitting a first pilot symbol sequence and a first data symbol sequence. 5. The method of claim 4, wherein the first pilot symbol sequence is a SC-FDMA symbol sequence. 6. The method according to claim 4, in which the first sequence of data symbols is a sequence of SC-FDMA symbols. 7. A wireless communication device, comprising:
means for selecting a subband from a set of subbands;
means for generating a first sequence of pilot symbols for transmission in a subband, the pilot symbols being orthogonal and adapted to alternate with a second sequence of symbols generated in the second processor;
means for generating a first sequence of data symbols, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor; and
means for transmitting a first sequence of pilot symbols and a first sequence of data symbols. 8. The device according to claim 7, in which the first sequence of characters of the control signal is a sequence of SC-FDMA characters. 9. The device according to claim 7, in which the first sequence of data symbols is a sequence of SC-FDMA symbols. 10. A wireless communication device, comprising:
a first processor adapted to:
select a subband from a set of subranges;
generate a first pilot symbol sequence for transmission in a subband, the pilot symbols being orthogonal and adapted to alternate with a second symbol sequence generated in the second processor; and
generate a first sequence of data symbols, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor;
a multiplexer for multiplexing a first pilot symbol sequence with a first data symbol sequence; and
a transmitter connected to the first processor for transmitting a first pilot symbol sequence multiplexed with a first data symbol sequence. 11. The device according to claim 10, in which the first sequence of symbols of the pilot signal is a sequence of SC-FDMA symbols. 12. The device of claim 10, in which the first sequence of data characters is a sequence of SC-FDMA characters. 13. A wireless communication method, comprising the steps of:
selecting a subband from a set of subbands;
generating a first pilot symbol sequence for transmission in a subband, the pilot symbols being orthogonal to the second pilot symbol sequence and adapted to alternate with a second symbol sequence generated in the second processor;
generating a first sequence of data symbols, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor;
multiplexing a first pilot symbol sequence with a first data symbol sequence and
transmitting a first pilot symbol sequence multiplexed with a first data symbol sequence. 14. The method of claim 13, wherein the first pilot symbol sequence is a SC-FDMA symbol sequence. 15. The method of claim 13, wherein the first data symbol sequence is an SC-FDMA symbol sequence. 16. A wireless communication device, comprising:
means for selecting a subband from a set of subbands;
means for generating a first sequence of pilot symbols for transmission in a subband, the pilot symbols being orthogonal and adapted to alternate with a second sequence of symbols generated in the second processor;
means for generating a first sequence of data symbols, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor;
means for multiplexing a first sequence of pilot symbols with a first sequence of data symbols and
means for transmitting a first pilot symbol sequence multiplexed with a first data symbol sequence. 17. The device according to clause 16, in which the first sequence of characters of the control signal is a sequence of SC-FDMA characters. 18. The device according to clause 16, in which the first sequence of data characters is a sequence of SC-FDMA characters. 19. A wireless communication device, comprising:
a first processor adapted to:
select a subband from a set of subranges;
generate a first sequence of pilot symbols having a first duration for transmission in a subband, wherein the pilot symbols are orthogonal and adapted to alternate with a second symbol sequence generated in a second processor; and
generate a first sequence of data symbols having a second duration, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor;
a multiplexer for multiplexing a first pilot symbol sequence with a first data symbol sequence and
a transmitter connected to the first processor for transmitting a first pilot symbol sequence multiplexed with a first data symbol sequence. 20. The device according to claim 19, in which the first sequence of characters of the control signal is a sequence of SC-FDMA characters. 21. The device according to claim 19, in which the first sequence of data characters is a sequence of SC-FDMA characters. 22. A wireless communication method, comprising the steps of:
selecting a subband from a set of subbands;
generating a first sequence of pilot symbols having a first duration for transmission in a subband, the pilot symbols being orthogonal and adapted to alternate with a second sequence of symbols generated in the second processor;
generating a first sequence of data symbols having a second duration, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor;
multiplexing a first pilot symbol sequence with a first data symbol sequence and
transmitting a first pilot symbol sequence multiplexed with a first data symbol sequence. 23. The method of claim 22, wherein the first pilot symbol sequence is a SC-FDMA symbol sequence. 24. The method of claim 22, wherein the first data symbol sequence is an SC-FDMA symbol sequence. 25. A wireless communications device, comprising:
means for selecting a subband from the set of subbands, generating a first sequence of pilot symbols having a first duration for transmission in a subband, the pilot symbols being orthogonal and adapted to interlace with a second sequence of symbols generated in the second processor and generating a first sequence of data symbols, having a second duration, the first sequence of data symbols being non-orthogonal to the second sequence STI data symbols generated by the second processor;
means for multiplexing a first sequence of pilot symbols with a first sequence of data symbols and
means for transmitting a first pilot symbol sequence multiplexed with a first data symbol sequence. 26. The device according A.25, in which the first sequence of characters of the control signal is a sequence of SC-FDMA characters. 27. The device according A.25, in which the first sequence of data characters is a sequence of SC-FDMA characters. 28. A computer-readable medium on which a program code is recorded that supports wireless communication, comprising:
code prompting the processor to select a subband from the set of subbands;
code for causing the processor to generate a first pilot symbol sequence for transmission in a subband, the pilot symbols being orthogonal and adapted to alternate with a second symbol sequence generated in the second processor; and
code for causing the processor to generate a first sequence of data symbols, the first sequence of data symbols being non-orthogonal to the second sequence of data symbols generated in the second processor; and
code for causing the processor to control the transmission of a first pilot symbol sequence and a first data symbol sequence.

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