HK1114704A - Systems and methods for beamforming feedback in multi antenna communication systems - Google Patents

Description

System and method for beamforming feedback in a multi-antenna communication system

Technical Field

This document relates generally to wireless communications, and more particularly to eigen-beam forming (eigen-beam forming) for wireless communication systems.

Background

Orthogonal Frequency Division Multiple Access (OFDMA) systems use Orthogonal Frequency Division Multiplexing (OFDM). OFDM is a multi-carrier modulation technique that divides the overall system bandwidth into multiple (N) orthogonal frequency subcarriers. These subcarriers may also be referred to as tones (tones), bins (bins), and frequency channels. Each subcarrier is associated with a respective subcarrier that may be modulated with data. Up to N modulation symbols may be transmitted on all N subcarriers in each OFDM symbol period. These modulation symbols are converted to the time domain using an N-point Inverse Fast Fourier Transform (IFFT) to generate a transformed symbol that contains N time-domain chips or samples.

In a frequency hopping communication system, data is transmitted on different frequency subcarriers during different time intervals, which may be referred to as "hop periods". These frequency subcarriers may be provided by orthogonal frequency division multiplexing, other multicarrier modulation techniques, or some other technique. With frequency hopping, data transmission hops from one subcarrier to another in a pseudo-random manner. Such frequency hopping provides frequency diversity and enables the data transmission to better withstand deleterious path effects such as narrowband interference, jitter, fading, and the like.

One problem that exists in most communication systems is that the receiver is located in a particular portion of the area served by the access point. In this case, when the transmitter has a plurality of transmit antennas, it is not necessary to combine signals provided from each antenna in order to provide maximum power at the receiver. In this case, problems may occur in decoding the signal received at the receiver. One way to address these problems is to use beamforming.

Beamforming is a spatial processing technique that improves the signal-to-noise ratio of a wireless link using multiple antennas. Generally, beamforming may be used at a transmitter or a receiver in a multiple antenna system. Beamforming provides a number of benefits in improving the signal-to-noise ratio, thereby further improving the decoding of the signal by the receiver.

Some types of OFDMA systems are Frequency Division Duplex (FDD) OFDMA systems. In these FDD OFDMA systems, transmissions from the access point to the access terminal and from the access terminal to the access point occupy different independent frequency bands. In FDD OFDMA systems, feedback for beamforming typically requires knowledge of the channel at the transmitter (e.g., access point), which cannot be obtained if there is not enough feedback. This feedback is typically in the form of actual beamforming weights or vectors, which require a lot of control or signaling channel resources. This reduces the data rate and increases the required overhead.

It is therefore desirable to provide feedback for more accurate beamforming while minimizing the resources required to provide feedback from the receiver to the transmitter.

Disclosure of Invention

In some embodiments, available reverse link transmission resources allocated for transmission of beamforming information are determined based on the determination of available reverse link transmission resources. In some embodiments, this may be performed by a processor or other module. Additionally, in some embodiments, this information is transmitted over the air as instructions.

In a particular embodiment, it is determined whether to transmit eigenbeam information from at least one antenna based on the channel information. In some embodiments, the channel information may be channel statistics or second order channel statistics. In other embodiments, the channel information may be instantaneous channel information.

It is understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein it is shown and described exemplary embodiments of the invention by way of illustration. It is to be understood that the disclosed embodiments may include other different embodiments and aspects, and that several of the details thereof may be modified in various respects, all without departing from the scope of the invention.

Drawings

The features, nature, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout and wherein:

fig. 1 illustrates a multiple access wireless communication system according to one embodiment;

fig. 2 illustrates a spectrum allocation scheme for a multiple access wireless communication system according to one embodiment;

fig. 3 shows a schematic block diagram of eigenbeams experienced by a receiver in a wireless communication system according to one embodiment;

fig. 4 illustrates a transmitter and a receiver in a multiple access wireless communication system according to one embodiment;

fig. 5 shows a block diagram of a transmitter system in a multiple access wireless communication system according to one embodiment;

fig. 6 shows a block diagram of a receiver system in a multiple access wireless communication system according to one embodiment;

fig. 7 illustrates a flow diagram for determining resources allocated for providing eigenbeam feedback according to one embodiment;

fig. 8 shows a flow diagram for determining whether to provide eigenbeam feedback according to another embodiment;

fig. 9 shows a flow diagram for generating eigenbeam vectors according to another embodiment; and

fig. 10 illustrates a flow diagram for generating eigenbeam feedback according to one embodiment.

Detailed Description

Referring to fig. 1, a multiple access wireless communication system according to one embodiment is shown. The multiple access wireless communication system 100 includes a plurality of cells, e.g., cells 102, 104, and 106. In the embodiment of fig. 1, each cell 102, 104, and 106 may include an access point 150 that includes multiple sectors. Multiple sectors may be formed by groups of antennas each responsible for communication with access terminals in a portion of a cell. In cell 102, antenna groups 112, 114, and 116 each correspond to a different sector. In cell 104, antenna groups 118, 120, and 122 each correspond to a different sector. In cell 106, antenna groups 124, 126, and 128 each correspond to a different sector.

Each cell includes a plurality of access terminals that may communicate with one or more sectors of each access point. For example, access terminals 130 and 132 are in communication base 142, access terminals 134 and 136 are in communication with access point 144, and access terminals 138 and 140 are in communication with access point 146.

As can be seen in fig. 1, each access terminal 130, 132, 134, 136, 138, and 140 is located at a different portion of its respective cell than every other access terminal within the same cell. In addition, each access terminal may be a different distance from the corresponding antenna group with which it is communicating. Due to the two factors mentioned above, as well as due to environmental and other conditions in the cell, situations can arise that result in different channel conditions between each access terminal and the corresponding antenna group with which it is communicating.

As used herein, an access point may be a fixed station used for communicating with the terminals and may also be referred to as, and include some or all the functionality of, a base station, a node B, or some other terminology. An access terminal may also be referred to as, and include some or all the functionality of, a User Equipment (UE), a wireless communication device, a terminal, a mobile station, or some other terminology.

Referring to fig. 2, a spectrum allocation scheme for a multiple access wireless communication system is shown. A plurality of OFDM symbols 200 are allocated over T symbol periods and S frequency subcarriers. Each OFDM symbol 200 includes one of T symbol periods and one of S tones or frequency subcarriers.

In an OFDM frequency hopping system, one or more symbols 200 can be assigned to a given access terminal. In one embodiment of the allocation scheme shown in fig. 2, one or more hop regions of a symbol (e.g., hop region 202) are allocated to a group of access terminals for communication on the reverse link. Within each hop region, the allocation of symbols may be randomized to reduce potential interference and provide frequency diversity against deleterious path effects.

Each hop region 202 includes symbols 204 that may be assigned to one or more access terminals that are in communication with a sector of the access point and are assigned to the hop region. The position of hop region 202 within T symbol periods and S subcarriers varies with the hop sequence in each hop period or frame. In addition, the assignment of symbols 204 to the various access terminals within hop region 202 may not be the same for each hop period.

The hopping sequence can select the location of the hopping region 202 for each hopping period pseudo-randomly, or according to a predetermined sequence. The hopping sequences for different sectors of the same access point can be designed to be orthogonal to one another to avoid "intra-cell" interference between access terminals communicating with the same access point. Further, the hopping sequence for each access point can be pseudo-random with respect to the hopping sequences of neighboring access points. This may help randomize "inter-cell" interference between access terminals communicating with different access points.

In the case of reverse link communication in an FDD communication system, frequency subbands 1 through S do not overlap with any of frequency subbands 1 through S of the forward link. In the reverse link, certain symbols 204 of the hop region 202 can be assigned to pilot symbols that can be transmitted from the access terminal to the access point. In one embodiment, the symbol 204 assignment for pilot symbols should support Spatial Division Multiple Access (SDMA), where signals of different access terminals overlapping on the same hop region can be separated if there is sufficient spatial signal difference for the different access terminals due to the presence of multiple receive antennas at a sector or access point.

It should be noted that although fig. 2 depicts hop region 200 having a length of seven symbol periods, the length of hop region 200 may be any desired value and may vary in size between hop periods or between different hop regions within a given hop period.

Also, it should be noted that although the embodiment of fig. 2 is described with reference to block hopping, the location of the blocks need not change between successive hopping periods.

Referring to fig. 3, a schematic block diagram of eigenbeams experienced at a wireless communication system is shown, in accordance with one embodiment. Transmitter 300 (which may be an access point) transmits multiple symbols in a given hop period for receiver 304 (which may be an access terminal). Signals transmitted by transmitter 300 are transmitted from antenna 302_a、302_b、302_c、...、302_tTransmitted by receiver 304 at antenna 306_a、306_b、...、306_tIs received. This forms a MIMO channel between the transmitter 200 and the receiver 304. During transmission of a symbol from transmitter 300 to receiver 304, transmitter 300 eigen-beamforming the symbol. Eigenbeamforming is a technique that combines beamforming, diversity, and spatial multiplexing gains, using eigenvectors to multiply, phase shift, and/or amplitude shift symbol transmissions according to the antenna via which the symbol was transmitted.

In one embodiment, transmitter 300 is driven from antenna 302_a、302_b、302_c、...、302_tPilot symbols are transmitted and used by the receiver 304 to estimate the downlink channel and compute its correlation matrix. The receiver 304 then performs eigenvalue decomposition on the correlation matrix and provides information about the eigenvectors to the transmitter 300. In some embodiments, the receiver 304 determines which eigenvector beam pattern will yield the highest signal-to-noise ratio (SNR) or other desired signal characteristics and sends this information to the base station, which can use the eigenvector information to beamform the data signal transmission to the mobile station in a subsequent transmission.

As shown in fig. 3, the eigenbeam may have multiple (local) maxima 308 in different directions_a、308_bAnd 308_c. Other eigenbeams may have 310 in other directions_aAnd 310_bBut it hasIs lower than having a maximum value 308_a、308_bAnd 308_cAs received at receiver 304. Furthermore, the radiation pattern, and those eigenbeams with maxima, may change over time, depending on changes in channel conditions, receiver location, or other factors.

In order to provide sufficient information for eigen-beamforming at the transmitter 300, the receiver 304 provides feedback information about the eigenvectors to the transmitter 300. In one embodiment, feedback is provided based on channel conditions. For example, in one embodiment, feedback may be provided if channel conditions have not substantially changed. In other embodiments, feedback may be provided if channel conditions have changed recently. In additional embodiments, no feedback or minimal feedback may be provided if channel conditions change frequently. In other embodiments, feedback may be provided if the channel conditions have changed recently or if the channel conditions have not substantially changed. In some embodiments, changes in channel conditions may be determined by changes in channel statistics, instantaneous channel information, or signal-to-noise ratio.

In one embodiment, the feedback may include eigenvectors calculated at the receiver 304 for the dominant eigenbeams experienced by the receiver 304. In some embodiments, information about the eigenvectors of the dominant eigenbeams is quantized according to a codebook and then the quantized bits are transmitted to the transmitter 302 that includes the codebook for reading the quantized bits.

In one embodiment, the quantization bits are based on the minimum mean square error between the codebook and the dominant eigenbeam or the dominant beam and other eigenbeams.

Feedback provided by the access terminal is used to form a preliminary beamforming matrix comprising a plurality of eigenvectors that have been fed back from the receiver to the transmitter. Due to limited reverse link resources, this preliminary beamforming matrix may not include all of the eigenvectors needed for transmission.

To form the set of eigen-beamforming vectors that provide the best available transmission characteristics, the beamforming matrix is QR decomposed to form the complete set of eigen-vectors, as follows:

V＝QR(B)

B＝[v₁v₂…v_k]is the K eigenvectors that have been fed back

B is the "preliminary" beamforming matrix. V is the "final" beamforming matrix comprising the complete set of eigenvectors.

V＝[v₁v₂…v_kv_k+1…………v_M]

v_k+1…v_MIs a pseudo-random feature vector generated from the QR decomposition.

Respective scalar representations of the beamforming vectors are applied from M_TBeamforming weights for symbols transmitted by each antenna to each access terminal. Thus, these vectors can be represented by the following equations:

equation (6)

Where M is the number of layers used for transmission. To determine how many eigenbeams should be used (order prediction) and which transmission mode should be used to obtain the maximum eigenbeamforming gain, a variety of methods may be used. If the access terminal is not scheduled, eigenbeam feedback (e.g., 7-bit or other sized feedback) may include rank information, which may be calculated based on the broadband pilot and reported along with the eigenbeam information. The control or signaling channel information sent from the access terminal, after decoding, can serve as a broadband pilot for the reverse link.

Referring to fig. 4, a transmitter and a receiver in a multiple access wireless communication system according to one embodiment are shown. In the transmitter system 410, traffic data for a number of data streams is provided from a data source 412 to a Transmit (TX) data processor 414. In one embodiment, each data stream is transmitted over a respective transmit antenna. TX data processor 414 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for that data stream to provide coded data. In some embodiments, TX data processor 414 applies beamforming weights to the symbols of the data streams based on the user to which the symbol is being transmitted. In some embodiments, beamforming weights may be generated based on eigenbeam vectors generated at the transmitter 402 and provided as feedback to the transmitter 400. Further, in case of scheduling transmission, the TX data processor 414 may select a packet format based on order information transmitted from a user.

The coded data for each data stream may be multiplexed with pilot data using OFDM techniques. The pilot data is typically a known data pattern that is processed in a known manner and may be used at the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream is then modulated (e.g., symbol mapped) based on a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for that data stream to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions performed by processor 430. As described above, in some embodiments, the packet format of one or more streams may vary depending on the order information transmitted from the user.

The modulation symbols for all data streams are then provided to a TX MIMO processor 420, which processor 420 may further process the modulation symbols (e.g., OFDM). TX MIMO processor 420 then forwards N_TN are provided by transmitters (TMTR)422a through 422t_TA stream of modulation symbols. In some embodiments, TX MIMO processor 420 applies beamforming weights to the symbols of the data streams based on the user to which the symbol is being transmitted and the antenna from which the symbol is being transmitted, based on the channel response information for the user.

Each transmitter 422 receives and processes a respective symbol stream to provide one or more analog signals, and further conditions (e.g., amplifies, filters, and upconverts) the analog signals to provide a modulated signal suitable for transmission over the MIMO channel. Then, respectively from N_TN transmitted from transmitters 422a through 422t by antennas 424a through 424t_TA modulated signal.

In the receiver system 450, the transmitted modulated signal consists of N_REach antenna 452a through 452r receives a received signal and the received signal from each antenna 452 is provided to a respective receiver (RCVR) 454. Each receiver 454 conditions (e.g., filters, amplifies, and downconverts) a respective received signal, digitizes the conditioned signal to provide samples, and further processes the samples to provide a corresponding "received" symbol stream.

RX data processor 460 then operates based on a particular receiver processing technique from N_RN are received and processed by a receiver 454_RA stream of received symbols to provide N_TA "detected" symbol stream. The processing by RX data processor 460 is described in further detail below. Each detected symbol stream includes symbols that are estimates of the modulation symbols transmitted for the corresponding data stream. The RX data processor 460 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. RX data processor 460The processing is complementary to that performed by TX MIMO processor 420 and TX data processor 414 at transmitter system 410.

The channel response estimate generated by RX processor 460 may be used to perform space, space/time processing at the receiver, adjust power levels, change modulation rates or schemes, or other operations. RX processor 460 may further estimate the signal-to-noise-and-interference ratios (SNRs) of the detected symbol streams, and possibly other channel characteristics, and provides these values to a processor 470. RX data processor 460 or processor 470 may further derive an estimate of the "operating" SNR for the system. Processor 470 then provides estimated Channel State Information (CSI), which may comprise various types of information regarding the communication link and/or the received data stream. For example, the CSI may comprise only the operating SNR. The CSI is then processed by a TX data processor 438 (which also receives traffic data for a number of data streams from a data source 476), modulated by a modulator 480, conditioned by transmitters 454a through 454r, and transmitted back to transmitter system 410.

In addition, processor 470 may compute the eigenbeams experienced by receiver 402. Eigenbeams may be calculated as described with respect to fig. 3. Processor 470 may then determine the dominant eigenbeams and may provide feedback only for the dominant eigenbeams. Processor 470 may quantize the dominant eigenbeams according to a codebook known to transmitter 400. In some embodiments, 5-bit encoding may be used, as described with respect to fig. 3, to allow for a wide range of feedback. The codebook size may vary depending on the reverse link resources available for this feedback.

To determine when to feedback on the dominant eigenbeams, processor 470 may compute channel statistics and determine what changes in channel statistics have occurred between two or more consecutive transmissions to receiver 402. Based on the degree of change, it may be determined whether eigenbeam feedback is provided. In additional embodiments, the processor may determine instantaneous channel information for a particular transmission and then determine a change between instantaneous channel information for one or more previous transmissions. This information can then be used to determine whether to provide eigenbeam feedback.

At transmitter system 410, the modulated signals from receiver system 450 are received by antennas 424, conditioned by receivers 422, demodulated by a demodulator 440, and processed by a RX data processor 442 to recover the CSI reported by the receiver system. The reported CSI is then provided to processor 430 and used to: (1) determine the data rates and coding and modulation schemes to be used for the data streams, and (2) generate various controls for TX data processor 414 and TX MIMO processor 420.

At the receiver, multiple processing techniques may be used to process N_RA received signal to N_TOne transmitted symbol stream is detected. These receiver processing techniques can be grouped into two main categories: (i) spatial and space-time receiver processing techniques (also known as equalization techniques); and (ii) "successive nulling/equalization and interference cancellation" receiver processing techniques (also known as "successive interference cancellation" or "successive cancellation" receiver processing techniques).

From N_TA transmission sum N_RThe MIMO channel formed by the receiving antennas can be decomposed into N_sA separate channel, wherein N_s≤min{N_T，N_R}。N_sEach of the independent channels may also be referred to as a spatial subchannel (or a transmission channel) of the MIMO channel and corresponds to one dimension.

For a full order MIMO channel, where N_s＝N_T≤N_RFrom N_TEach of the transmit antennas transmits a separate data stream. The transmitted data streams may experience different channel conditions (e.g., different fading and multipath effects) and may achieve different signal-to-noise-and-interference ratios (SNRs) for a given transmit power. Further, where successive interference cancellation processing is used at the receiver to recover the transmitted data streams, different SNRs may be obtained for the data streams based on the particular order in which the data streams were recovered. Thus, different data streams may support different data rates depending on their achieved SNR. Due to the fact thatChannel conditions typically vary over time, as do the data rates supported by each data stream.

A MIMO design may have two modes of operation, Single Codeword (SCW) and Multiple Codeword (MCW). In the MCW mode, the transmitter can encode data transmitted on each spatial layer separately with different rates. The receiver uses Successive Interference Cancellation (SIC) algorithm, which works as follows: decoding the first layer; then extracting its base value from the received signal after coding the coded first layer again and multiplying it with the "estimated channel"; the second layer is then decoded, and so on. This "onion peeling" method indicates that each successively decoded layer observes an increasing SNR and can therefore support higher rates. MCW design using SIC achieves maximum system transmission capacity based on channel conditions without error propagation. The disadvantages of this design are caused by the burden of "managing" the rate of each spatial layer, including: (a) increased CQI feedback (one CQI needs to be provided for each layer); (b) incremental Acknowledgement (ACK) or Negative Acknowledgement (NACK) messages (one per layer); (c) complexity of hybrid arq (harq) due to each layer being able to terminate in different transmissions; (d) performance sensitivity of SIC to channel estimation errors with increased doppler and/or low SNR; and (e) increased decoding delay requirements due to each subsequent layer being decodable only after the previous layer is decoded.

In SCW mode design, the transmitter encodes the data sent on each spatial layer using the "same data rate". The receiver may use a low complexity linear receiver, such as a minimum mean square error scheme (MMSE) or Zero Frequency (ZF) receiver, or a non-linear receiver, such as a QRM, for each tone. This allows the receiver to report channel estimates only for the "best" layer and reduces the transmission overhead for providing this information.

Although fig. 4 and the associated description are directed to a MIMO system, other multiple-input single-output (MISO) and single-output multiple-input (SIMO) systems may also use the structure of fig. 4 and the structure, method, and system described with respect to fig. 3.

Referring to fig. 5, a block diagram of a transmitter system in a multiple access wireless communication system is shown, in accordance with one embodiment. The transmitter 500 uses a rate prediction module 502, which controls a single-input single-output (SISO) encoder 504 to generate an information stream, based on the channel information.

The bits 506 are turbo encoded by the encoder module 506 and mapped to modulation symbols by the mapping module 508, wherein the mapping module 508 maps based on a Packet Format (PF)524 indicated by the rate prediction module 502. The coded symbols are then demultiplexed by a demultiplexer 510 into M layers 512, which are provided to a beamforming module 514.

The beamforming module 514 generates an N_TThe xm beamforming matrix. The matrix may be formed for each transmission on the reverse link. Each transmission may involve processing M layers and generating N_TAnd (4) each stream. The eigenbeam weights may be generated from eigenbeam feedback 524 (e.g., a quantized eigenvector sent by the access terminal to the access point). Further, as described above, the feedback may include only the dominant eigenvectors experienced at the access terminal.

After beamforming, N is added_TStreams 512 are provided to OFDM modulators 518a through 518t, which interleave the output symbol streams with pilot symbols. The OFDM processing for each of the transmission antennas 520a to 520t is performed in the same manner, and after the OFDM processing, signals are transmitted through the MIMO scheme.

In SISO encoder 504, a turbo encoder 506 encodes the data stream and, in one embodiment, uses 1/5 coding rates. It should be noted that other types of encoders and encoding rates may be used. The symbol encoder 508 maps the encoded data to constellation symbols for transmission. In one embodiment, the constellation may be a quadrature amplitude constellation. Although SISO encoders are described herein, other encoder types, including MIMO encoders, may also be used.

The rate prediction module 502 processes the CQI and/or channel estimation information, which includes rank information and may be received at the access point for each access terminal. Rank information may be provided based on the broadband pilot symbols, the hop-based pilot symbols, or both. The order information is used by rate prediction module 502 to determine the modulation rate. In one embodiment, the rate prediction algorithm may use channel estimates and/or 5-bit CQI feedback 522 at approximately every 5 milliseconds. The actual number of bits for CQI feedback 522 may vary based on design choices or parameters.

Packet formats, such as modulation rates, are determined using a variety of techniques. Exemplary techniques are described and disclosed in co-pending U.S. patent application No.11/021,791 entitled "Performance Based Rank Prediction for MIMO Design" and U.S. patent application No.11/022,347 entitled "Capacity Based Rank Prediction for MIMO Design," both of which are incorporated herein by reference as if fully set forth herein.

Referring to fig. 6, a block diagram of a receiver system in a multiple access wireless communication system is shown, in accordance with one embodiment. In fig. 6, each antenna 602a through 602t receives one or more symbols intended for receiver 600. Antennas 602a through 602t are coupled to OFDM demodulators 604a through 604t, respectively, each coupled to a hop buffer 606. OFDM demodulators 604a through 604t demodulate the OFDM received symbols into received symbol streams, respectively. Hop buffer 606 stores received symbols corresponding to a hop region in which the received symbols are transmitted.

The output of the hop buffer 606 is provided to a decoder 608, which decoder 608 may be a decoder that processes each carrier frequency of the OFDM frequency band independently. Both hop buffer 606 and decoder 608 are coupled to a channel statistics process 610 that forms eigenbeam weights that can be provided to the transmitter for subsequent transmission. In addition, channel statistics processing 610 determines channel statistics, second order channel statistics, instantaneous channel information, or signal to noise ratios for a plurality of transmissions. The channel statistics processing 610 may also determine whether a change has occurred and then transmit eigenbeam feedback. In addition, receiver 600 can determine available reverse link resources.

The demodulated information stream is then provided to a log-likelihood ratio module 612 and decoder 614, and the decoder 614 may be a turbo decoder or other decoder to match the encoder used at the access point that provides the decoded data stream for processing.

Referring to fig. 7, a flow diagram of determining resources allocated for providing eigenbeam feedback is shown, in accordance with one embodiment. At block 700, available reverse link resources are determined. The resources may be the number of symbols, available bandwidth, or other information that may be transmitted over a reverse link signaling or control channel. The determination may be made at the access point and provided to the access terminal, or the determination may be made at the access terminal based on fixed parameters or the data rate of the next forward link transmission.

Then, at block 702, a determination is made of the amount of eigenbeam feedback that is available at the access terminal. The number may be the total number of eigenbeams, the number of dominant eigenbeams, or the order of the eigenbeams. Further, the number can include order information or CQI information such that the number takes into account all or a majority of the feedback required to the access terminal.

At block 704, an indicator of resources allocated to reverse link transmission is generated. The indicator may be generated at the access point or the access terminal and then transmitted to the access terminal. Resources on the reverse link are then allocated for transmission based on the indicator, block 706.

Referring to fig. 8, a flow diagram of determining whether to provide eigenbeam feedback is shown, in accordance with another embodiment. At block 800, channel information is generated. The channel information may be instantaneous channel information or channel statistics. In some embodiments, the channel information may relate to packet error rate, fading, signal strength, channel state information, or other information. Further, channel information calculated in one or both of the frequency domain and the time domain may be used. Further, in some embodiments, second order channel statistics are used. In other embodiments, first order or higher order channel statistics are used in addition to second order channel statistics. In some embodiments, the channel information may be calculated based on pilot symbols or both pilot symbols and data symbols.

At block 802, a change in channel information is determined. The change may be between consecutive transmissions, between the current transmission and the transmission N transmissions prior to the current transmission, a time-averaged change, an average of M transmissions, or other means. In one embodiment, the variation may be calculated as an absolute value of a squared difference of channel information between a current transmission and a transmission N transmissions prior to the current transmission.

At block 804, a determination is made whether the channel between the access terminal and the access point is stable or varying. In one embodiment, this determination may be made based on whether the variation of the channel statistics is greater than or less than a threshold. In other embodiments, the determination may be made based on a rate of change between multiple determinations of channel information change. Other methods may also be used to determine whether the channel is stable or varying.

At block 806, if the channel is determined to be stable, a dominant eigenbeam is determined. Information about the dominant eigenbeams is then transmitted to the access point, block 808. The information about the dominant eigenbeams may be quantized according to a codebook. Further, it should be noted that block 806 may occur at any time prior to block 804, and may be independent of the process shown in FIG. 8. If the channel is determined to be changing, no feedback is provided, block 810.

Referring to fig. 9, a flow diagram for generating eigenbeam vectors in accordance with another embodiment is shown. In block 900, eigenbeam information provided from the terminal to the access point is read. As described above, in some embodiments, eigenbeam information may be quantized such that, at block 900, the correct information is read from the codebook for use. Furthermore, the eigenbeam information may only apply to the main eigenbeam.

At block 902, eigenbeam information is used to construct an eigenbeam forming matrix. The eigenbeamforming matrix is then decomposed, block 904. The decomposition may be a QR decomposition. Then, at block 906, eigenvectors representing beamforming weights can be generated for symbols of a next hop region to be transmitted to the access terminal.

Referring to fig. 10, a flow diagram for generating eigenbeam feedback is shown, in accordance with one embodiment. At block 1000, a forward link channel is estimated based on received symbols, e.g., pilot symbols. Then, at block 1002, a dominant eigenbeam is determined and computed based on the forward link channel estimates. At block 1004, the amount of available forward link resources is determined. The resource may be the number of symbols, available bandwidth, or other information that may be transmitted over a reverse link signaling or control channel. This determination may be made at the access point and provided to the access terminal, or the determination may be made at the access terminal based on fixed parameters or the data rate of the next forward link transmission.

In block 1006, where the reverse link resources are deemed low, a frequency average of the dominant eigenbeams is determined before being provided as feedback to the access point. The dominant eigenbeams for each desired frequency are provided as feedback to the access point, block 1008, where the reverse link resources are deemed high.

The above-described processing may be performed using TX processor 420 or 460, processor 430 or 470, and memory 432 or 472. The other processes, operations, and features described with respect to fig. 5A, 5B, and 6-10 may be implemented on any processor, controller, and/or other processing device and may be stored as computer-readable instructions (e.g., source code, object code, or other code) on a computer-readable medium.

The techniques described herein may be implemented in a variety of ways. For example, these techniques may be implemented in hardware, software, or a combination of both. For a hardware implementation, the processing units within an access point or access terminal may be implemented within one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof.

For a software implementation, the techniques described herein may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in memory units and executed by processors. The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the features, functions, operations, and embodiments disclosed herein. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features described herein.

Claims (84)

1. A wireless communications apparatus, comprising:

at least two antennas; and

a processor can determine available reverse link transmission resources and provide an indicator of the reverse link transmission resources allocated for transmission of beamforming information based on the determination of the available reverse link transmission resources.

2. The wireless communications apparatus of claim 1, wherein the processor is capable of determining the available reverse link transmission resources based upon a number of users transmitting reverse link transmissions.

3. The wireless communications apparatus of claim 2, wherein the processor is capable of transmitting a message including the indicator from the at least two antennas.

4. The wireless communications apparatus of claim 1, wherein the processor is capable of determining the available reverse link transmission resources based upon a forward link transmission to a wireless communication device.

5. The wireless communications apparatus of claim 1, wherein the processor is capable of transmitting a message including the beamforming information based on the reverse link resources of the indicator.

6. The wireless communications apparatus of claim 1, wherein the reverse link resources comprise a data channel and a control channel.

7. The wireless communications apparatus of claim 1, wherein the indicator further comprises information regarding a plurality of eigenbeams fed back on the allocated reverse link transmission resources.

8. The wireless communications apparatus of claim 1, wherein the indicator further comprises information feedback based on frequency averaged eigenbeam information.

9. The wireless communications apparatus of claim 1, wherein the wireless communications apparatus comprises an access terminal.

10. The wireless communication apparatus of claim 1, wherein the wireless communication apparatus comprises an access point.

11. The wireless communications apparatus of claim 1, wherein the indicator further comprises information feedback based on per-hop eigenbeam information.

12. The wireless communications apparatus of claim 1, wherein the indicator further comprises information feedback based on limited frequency averaged eigenbeam information.

13. An electronic device, comprising:

a memory; and

a processor, coupled to the memory, capable of determining whether to transmit eigenbeam information from at least one antenna based on channel information.

14. The electronic device of claim 13, wherein the channel information comprises channel statistics, and wherein the processor is capable of determining whether the channel is a stable channel or a varying channel based on the channel statistics and is capable of determining whether to transmit eigenbeam information based on whether the channel is the stable channel or the varying channel.

15. The electronic device of claim 13, wherein the channel information comprises channel statistics, and wherein the processor is capable of determining whether the channel is a stable channel or a varying channel based on whether the channel statistics vary over a period of time.

16. The electronic device of claim 13, wherein the channel information comprises channel statistics, and wherein the processor is capable of determining whether the channel is a stable channel or a varying channel based on whether a variation of the channel statistics over a period of time exceeds a threshold.

17. The electronic device of claim 13, wherein the channel information comprises channel statistics, and wherein the processor is capable of determining a number of eigenbeams for which eigenbeam information is to be transmitted based on the channel statistics.

18. The electronic device of claim 17, wherein the processor is capable of determining that a number of eigenbeams for which eigenbeam information is to be transmitted is less than a number of all eigenbeams used for transmission to the wireless communication apparatus.

19. The electronic device of claim 13, wherein the channel information comprises channel statistics, and wherein the processor is capable of determining whether to transmit frequency averaged eigenbeam information based on the channel statistics.

20. The electronic device of claim 13, wherein the channel information comprises channel statistics, and wherein the processor is capable of determining the channel statistics at predetermined time intervals.

21. The electronic device of claim 20, wherein the channel information comprises channel statistics, and wherein the processor is capable of determining a length of the predetermined time interval based on instructions received at the at least one antenna.

22. The electronic device of claim 13, wherein the eigenbeam information comprises information corresponding to one or more eigenvectors of a signal received at the wireless communication apparatus.

23. The electronic device of claim 22, wherein terms of the one or more eigenvectors are averaged over a plurality of signals received at the wireless communication apparatus.

24. The electronic device of claim 22, wherein the one or more feature vectors comprise one or more time-averaged feature vectors.

25. The electronic device of claim 22, wherein terms of the one or more eigenvectors are averaged over multiple subcarriers of the signal received at the wireless communication apparatus.

26. The electronic device of claim 22, wherein the one or more eigenvectors comprise one or more subcarrier averaged eigenvectors.

27. The electronic device of claim 13, wherein the eigenbeam information comprises information corresponding to one or more eigenvectors of a signal received at the wireless communication apparatus and eigenvalues of each of the one or more eigenvectors.

28. The electronic device of claim 13, wherein the eigenbeam information comprises information corresponding to a dominant eigenvector of a signal received at the wireless communication apparatus.

29. The electronic device of claim 13, wherein the processor is capable of quantizing the eigenbeam information according to a codebook.

30. The electronic device of claim 13, wherein the processor is capable of quantizing each complex element of the eigenbeam information using a desired number of bits.

31. The electronic device of claim 13, wherein the processor is capable of quantizing each complex element of the eigenbeam information according to a predetermined constellation.

32. The electronic device of claim 13, wherein the processor is capable of quantizing certain elements of the eigenbeam information.

33. The electronic device of claim 11, wherein the channel information comprises second order channel statistics.

34. The wireless communications apparatus of claim 11, wherein the channel information includes channel statistics, and wherein the processor determines whether to transmit eigenbeam information based on the channel statistics and received instructions.

35. The electronic device of claim 11, wherein the channel information comprises instantaneous channel information.

36. A method of resource allocation in a wireless communication system, comprising:

determining reverse link resources available at a wireless communication device;

determining an amount of resources required for beamforming feedback;

allocating beamforming feedback resources on the reverse link based on available reverse link resources.

37. The method of claim 36, wherein determining the available reverse link transmission resources comprises determining based on a number of users transmitting reverse link transmissions.

38. The method of claim 37, further comprising transmitting a message including an indicator of the allocated beamforming feedback resources.

39. The method of claim 36, wherein determining available reverse link resources comprises determining available reverse link resources based on forward link transmissions.

40. The method of claim 36, wherein the reverse link resources comprise a data channel and a control channel.

41. The method of claim 36, wherein the allocating step comprises allocating a plurality of eigenbeams to be fed back on the allocated reverse link resources.

42. The method of claim 36, wherein the allocating step comprises allocating feedback comprising frequency averaged eigenbeam information.

43. The method of claim 36, wherein the wireless communication device comprises an access terminal.

44. The method of claim 36, wherein the wireless communication device comprises an access point.

45. A method of resource allocation in a wireless communication system, comprising:

generating, at a wireless communication device, eigenbeam information;

generating channel information about a communication channel to which the wireless communication device is connected; and

determining whether to transmit the eigenbeam information based on the channel information.

46. The method of claim 45, wherein the channel information comprises channel statistics, and wherein determining whether to transmit comprises determining whether the channel is a stable channel or a varying channel based on the channel statistics.

47. The method of claim 45, wherein the channel information comprises channel statistics, and wherein determining whether the channel is the stable channel or the varying channel comprises determining based on whether the channel statistics vary over a period of time.

48. The method of claim 45, wherein the channel information comprises channel statistics, and wherein determining whether the channel is the stable channel or the varying channel comprises determining based on whether a variation of the channel statistics over a period of time exceeds a threshold.

49. The method of claim 45, wherein the channel information comprises channel statistics, and wherein determining whether to transmit comprises determining a number of eigenbeams for which eigenbeam information is to be transmitted based on the channel statistics.

50. The method of claim 49, wherein determining the number of eigenbeams comprises determining that the number of eigenbeams is less than the number of all eigenbeams used for transmission to the wireless communication device.

51. The method of claim 45, wherein the channel information comprises channel statistics, and wherein the method further comprises determining whether to transmit frequency averaged eigenbeam information based on the channel statistics.

52. The method of claim 45, wherein the channel information comprises channel statistics, and wherein generating channel statistics comprises generating channel statistics at predetermined time intervals.

53. The method of claim 45, wherein the eigenbeam information comprises information corresponding to one or more eigenvectors of a signal received at the wireless communication apparatus.

54. The method of claim 53, further comprising averaging the one or more eigenvectors over a plurality of received signals.

55. The method of claim 53, further comprising averaging the one or more eigenvectors over multiple subcarriers of the received signal.

56. The method of claim 45, wherein the eigenbeam information comprises information corresponding to one or more eigenvectors and eigenvalues for each of the one or more eigenvectors.

57. The method of claim 45, wherein the eigenbeam information comprises information corresponding to a dominant eigenvector of the received signal.

58. The method of claim 45, further comprising quantizing the eigenbeam information according to a codebook.

59. The method of claim 45 further comprising quantizing the eigenbeam information for the eigenbeam having the smallest mean square error.

60. The method of claim 45, wherein the channel information comprises second order channel statistics.

61. The method of claim 45, wherein the channel information comprises channel statistics, and wherein determining whether to transmit eigenbeam information comprises determining whether to transmit based on the channel statistics and the received instructions.

62. The method of claim 45, wherein the channel information comprises instantaneous channel information.

63. An apparatus, comprising:

means for determining available reverse link resources;

means for determining an amount of resources required for beamforming feedback;

means for allocating beamforming feedback resources on a reverse link based on available reverse link resources.

64. The apparatus of claim 63, wherein means for determining the available reverse link transmission resources comprises means for determining based on a number of users transmitting reverse link transmissions.

65. The apparatus of claim 63, wherein determining available reverse link resources comprises determining available reverse link resources based on a forward link transmission to the apparatus.

66. The apparatus of claim 63, wherein the means for allocating comprises means for allocating a plurality of eigenbeams to be fed back on the allocated reverse link resources.

67. The apparatus of claim 63, wherein the means for allocating comprises means for allocating feedback comprising frequency averaged eigenbeam information.

68. An apparatus, comprising:

means for generating eigenbeam information;

means for generating channel information regarding a communication channel to which the apparatus is connected; and

means for determining whether to transmit the eigenbeam information based on the channel information.

69. The apparatus of claim 68, wherein the channel information comprises channel statistics, and wherein the means for determining whether to transmit comprises means for determining whether the channel is a stable channel or a varying channel based on the channel statistics.

70. The apparatus of claim 69, wherein the channel information comprises channel statistics, and wherein means for determining whether the channel is the stable channel or the varying channel comprises means for determining based on whether the channel statistics vary over a period of time.

71. The apparatus of claim 69, wherein the channel information comprises channel statistics, and wherein means for determining whether the channel is the stable channel or the varying channel comprises means for determining based on whether a variation of the channel statistics over a period of time exceeds a threshold.

72. The apparatus of claim 68, wherein the channel information comprises channel statistics, and wherein the means for determining whether to transmit comprises means for determining a number of eigenbeams for which eigenbeam information is to be transmitted based on the channel statistics.

73. The apparatus of claim 72, wherein the number of eigenbeams is less than the number of all eigenbeams used for transmission to the wireless communication apparatus.

74. The apparatus of claim 68, wherein the channel information comprises channel statistics, and the apparatus further comprises means for determining whether to transmit frequency averaged eigenbeam information based on the channel statistics.

75. The apparatus of claim 68, wherein the channel information comprises channel statistics, and wherein the means for generating channel statistics comprises means for generating channel statistics at predetermined time intervals.

76. The apparatus of claim 68, wherein the channel information comprises channel statistics, and the apparatus further comprises means for averaging the one or more eigenvectors over multiple received signals.

77. The apparatus of claim 68, wherein the channel information comprises channel statistics, and the apparatus further comprises means for averaging the one or more eigenvectors over multiple subcarriers of the received signal.

78. The apparatus of claim 68, wherein the eigenbeam information comprises information corresponding to a dominant eigenvector of the received signal.

79. The apparatus of claim 68, further comprising means for quantizing the eigenbeam information according to a codebook.

80. The apparatus of claim 66, further comprising means for quantizing each complex element of the eigenbeam information according to a predetermined constellation.

81. The electronic device of claim 68, further comprising means for quantizing certain elements of the eigenbeam information.

82. The apparatus of claim 68, wherein the channel information comprises second order channel statistics.

83. The apparatus of claim 68, wherein the channel information comprises channel statistics, and wherein the means for determining whether to transmit eigenbeam information comprises means for determining whether to transmit based on channel statistics and received instructions.

84. The apparatus of claim 68, wherein the channel information comprises instantaneous channel information.