Communication apparatus and communication method

Abstract

To improve efficiency of processing related to feedback of information by a communication device which receives a spatially multiplexed stream.SOLUTION: A communication device includes a transmitter that transmits a reference signal including a plurality of spatial streams, a reception circuit that receives second information related to a part of the plurality of spatial streams in which channel estimation is performed using the reference signal and the second information determined based on first information related to reception quality of the plurality of spatial streams is fed back, and a control circuit that performs scheduling using the second information. The second information may include information for identifying terminals allocated to the part of spatial streams among a plurality of terminals, and may be related to only the part of spatial streams among the plurality of spatial streams.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a communication device and a communication method. [Background technology]

[0002] The IEEE Task Group (TG) be is currently developing the technical specifications for 802.11be (hereinafter referred to as "11be") as the successor standard to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard, 802.11ax (hereinafter referred to as "11ax").

[0003] In 11be, for example, compared to 11ax, an increase in the maximum number of spatial streams (also called the number of spatial streams (SS) or spatial multiplexing number) in downlink (DL) multi-user multiple-input multiple output (MU-MIMO) is being discussed. Increasing the maximum number of spatial streams can improve spectrum efficiency. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] IEEE 802.11-19 / 0828r3, feedback-overhead-analysis-for-16-spatial-stream-mimo, May, 2019 [Non-patent document 2] IEEE P802.11ax D4.0, February 2019 [Non-patent document 3] IEEE Std 802.11, 2016 Summary of the Invention

[0005] However, there is room for further study on the method of controlling spatial multiplexing processing.

[0006] Non-limiting examples of the present disclosure contribute to providing a base station, a terminal, and a communication method that improve the efficiency of processing related to information feedback by a communication device that receives a spatially multiplexed stream.

[0007] A communication device according to one embodiment of the present disclosure includes a control circuit that determines a spatial stream for which second information is to be fed back based on first information regarding the reception quality of a plurality of spatial streams, and a transmission circuit that transmits the second information regarding the determined spatial stream.

[0008] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0009] According to an embodiment of the present disclosure, it is possible to improve the efficiency of processing related to information feedback by a communication device that receives a spatially multiplexed stream.

[0010] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0011] [Figure 1] Sequence diagram showing an example of beamforming using null data packet (NDP) sounding and explicit feedback [Figure 2]An example of the High Efficiency (HE) Compressed Beamforming / Channel Quality Indicator (CQI) frame action field format. [Figure 3] A sequence diagram showing an example of staggered sounding [Figure 4] FIG. 1 is a block diagram showing a configuration example of a part of an STA according to a first embodiment; [Figure 5] FIG. 1 is a block diagram showing an example of the configuration of an AP according to a first embodiment; [Figure 6] FIG. 1 is a block diagram showing an example of the configuration of an STA according to a first embodiment; [Figure 7] FIG. 1 is a sequence diagram illustrating an example of operation of the wireless communication system according to the first embodiment. [Figure 8] Flowchart showing an example of an operation for determining feedback information according to the first embodiment [Figure 9] FIG. 1 shows an example of a system configuration according to a first embodiment. [Figure 10] FIG. 10 is a diagram showing an example of an HE Compressed Beamforming / CQI frame action field format according to Method 1-1. [Figure 11] FIG. 10 is a diagram showing an example of an HE Action field according to Method 1-2. [Figure 12] FIG. 10 is a diagram showing an example of a frame format according to Method 1-2. [Figure 13] FIG. 10 is a diagram showing an example of a BA frame format and a response signal transmission operation according to methods 1-3. [Figure 14] FIG. 10 is a diagram showing an example of a BA frame format and a response signal transmission operation according to methods 1-3. [Figure 15] Sequence diagram showing an example of operation related to methods 1-4 [Figure 16] Sequence diagram showing an example of operation related to methods 1-5 [Figure 17] A block diagram showing a configuration example of an AP according to a second embodiment. [Figure 18]FIG. 10 is a block diagram showing a configuration example of an STA according to a second embodiment. [Figure 19] FIG. 10 is a diagram showing an example of a system configuration according to a second embodiment. [Figure 20] FIG. 10 is a diagram showing an example of relative amplitude accuracy according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings.

[0013] In the 802.11 standard, for example, when space-time block coding (also called "Space-Time Block Coding (STBC)") is not performed, one modulation symbol stream is generated from one bit stream, and when space-time block coding is performed, two or more modulation symbol streams are generated from one bit stream. For example, a spatially multiplexed bit stream is called a "spatial stream," and a spatially multiplexed modulation symbol stream is called a "space-time stream (or "Space-time stream (STS)"). For example, when space-time block coding is not performed, the number of space-time streams is equal to the number of spatial streams.

[0014] In the following description, an example in which space-time block coding is not performed will be described. In other words, in the following description, spatial streams and space-time streams will not be distinguished from each other, and the term "spatial stream" will be used to mean a spatial channel used for spatial multiplexing. However, the spatial stream in the following description may be interpreted as a space-time stream when space-time block coding is performed.

[0015] [Beamforming] Downstream MU-MIMO uses beamforming technology, which can improve communication quality in the downlink.

[0016] In beamforming for DL ​​MU-MIMO, for example, weighting (also referred to as "steering," "spatial mapping," or "transmit precoding") is performed to control amplitude and phase in order to impart orthogonality to signals addressed to each user. A matrix representing this weighting (hereinafter referred to as "steering matrix") can be derived based on information about propagation paths (also referred to as "channels") estimated by beamforming.

[0017] The amount of propagation path information in DL MU-MIMO increases in proportion to, for example, the maximum number of spatial streams. Therefore, in 11be, which can increase the maximum number of spatial streams, methods for improving beamforming efficiency are being considered (see, for example, non-patent document 1).

[0018] 11ax supports a method using NDP sounding (also called an NDP feedback sequence) and explicit feedback as an example of a beamforming technique (see, for example, Non-Patent Document 2). Fig. 1 is a sequence diagram showing an example of beamforming using NDP sounding and explicit feedback.

[0019] In Fig. 1, an access point (AP, also called a "base station") transmits, for example, an NDP announcement (NDPA) to each terminal (also called a "STA (Station)"). By transmitting the NDPA, the AP notifies the STA of the transmission of the NDP.

[0020] The AP sends the NDPA followed by the NDP to the STA.

[0021] After receiving the NDP, the STA estimates the channel based on a signal (eg, a non-legacy long training field (non-legacy LTF)) included in the NDP.

[0022] Note that, for example, when a steering matrix is ​​added to a non-Legacy LTF, the STA may estimate a channel including the steering matrix (e.g., also referred to as an "effective channel") regardless of whether the received signal is NDP or non-NDP. In the following description, regardless of whether it is a channel or an effective channel, it is simply referred to as a propagation path response (also referred to as "propagation path characteristics," "channel response," "channel estimation matrix," or "channel matrix"). The STA determines feedback information to transmit to the AP in response to the NDP, for example, based on the channel estimation value.

[0023] Fig. 2 shows an example of the structure of feedback information transmitted from a STA to an AP, including a Compressed Beamforming / CQI frame Action field format.

[0024] The "HE MIMO Control" shown in Fig. 2 may include, for example, a feedback control signal. Furthermore, the "HE Compressed Beamforming Report" shown in Fig. 2 may include, for example, information such as reception quality for each spatial stream (for example, average signal-to-noise ratio (SNR)) or a feedback matrix in which the amount of information is compressed by a specified method. Furthermore, the "HE MU Exclusive Beamforming Report" shown in Fig. 2 may include, for example, information such as information on the difference between the SNR of each subcarrier and the average SNR of the spatial stream to which each subcarrier belongs.

[0025] In the following description, as an example, information such as a feedback control signal, a feedback matrix, and SNRs related to spatial streams and subcarriers included in the HE Compressed Beamforming / CQI frame Action field format shown in FIG. 2 (e.g., corresponding to second information) will be referred to as "feedback information (or also referred to as feedback signal)."

[0026] For example, if AP is NSTS If an NDP containing spatial streams is sent to a STA, the STA will RX ×N STS We can estimate a channel of size N RX indicates the number of receiving antennas of the STA. In this case, the size of the feedback matrix included in the feedback information by the STA (N r ×N c ) may be calculated, for example, according to the following formula (1):

number

[0027] The AP may perform scheduling for the STAs based on, for example, feedback information transmitted from the STAs. In scheduling, the AP may determine, for example, resource allocation information or transmission parameters for a destination STA or for each STA.

[0028] Furthermore, for example, when performing multi-user transmission (e.g., also referred to as "MU-MIMO transmission"), the AP may derive steering matrices based on feedback information received from multiple STAs. The AP may transmit downlink (DL) data (e.g., referred to as a DL MU physical layer convergence procedure protocol data unit (DL MU PPDU)) to the STAs using the steering matrices.

[0029] As another example of a beamforming technique, 802.11n supports "Staggered Sounding" (see, for example, Non-Patent Document 3).

[0030] FIG. 3 is a sequence diagram showing an example of the operation of staggered sounding.

[0031] Staggered sounding is a beamforming technique for single-user MIMO (SU-MIMO). For example, an AP transmits a signal (e.g., SU PPDU) including a data portion (e.g., also referred to as a data field) to a STA. The STA determines whether to transmit feedback information, for example, based on channel state information (CSI) / Steering Request included in the medium access control (MAC) layer of the signal transmitted from the AP. For example, when instructed to transmit feedback information (if feedback information transmission: yes), the STA feeds back a channel estimation value obtained based on a signal (e.g., non-legacy LTF) included in the signal transmitted from the AP. For example, the STA may add the channel estimation value (in other words, feedback information) to a response signal (e.g., Acknowledgement (ACK) or Block ACK (BA)) based on the feedback method instructed in the CSI / Steering Request, and transmit the response signal to the AP.

[0032] However, for example, if the AP performs beamforming for each STA using NDP sounding and explicit feedback every time it calculates (in other words, updates) a steering matrix, the overhead of feedback information increases and transmission efficiency may decrease.

[0033] In addition, the AP may not be able to appropriately determine the timing to update the steering matrix. For example, when the change in the channel response (e.g., also referred to as channel fading) is small (e.g., when the change in the channel response is less than a threshold), the steering matrix may not need to be updated. Therefore, when the change in the channel response is less than a threshold, if beamforming is performed using NDP sounding and explicit feedback, feedback information may be transmitted unnecessarily, which may reduce transmission efficiency.

[0034] In one embodiment of the present disclosure, a method for improving transmission efficiency in spatial multiplexing transmission such as MU-MIMO transmission will be described. For example, a method for improving the efficiency of processing related to feedback of information by a communication device that receives spatially multiplexed streams will be described.

[0035] (Embodiment 1) [Configuration of Wireless Communication System] A wireless communication system according to an embodiment of the present disclosure includes at least one AP100 and a plurality of STAs 200.

[0036] For example, in DL communication (e.g., transmission and reception of DL data), the AP100 (or also referred to as a "downlink wireless transmission device") may perform DL MU-MIMO transmission to a plurality of STAs 200 (or also referred to as "downlink wireless reception devices"). Each STA 200 may generate feedback information based on, for example, a signal transmitted by DL MU-MIMO (e.g., also referred to as DL MU PPDU), and transmit the feedback information to the AP100 (e.g., uplink (UL) SU transmission or UL MU transmission).

[0037] FIG. 4 is a block diagram showing a partial configuration example of the STA 200 according to an embodiment of the present disclosure. In the STA 200 shown in FIG. 4 (e.g., corresponding to a communication device), a feedback determination unit 204 (e.g., corresponding to a control circuit) determines a spatial stream for which second information (e.g., stream information) is to be fed back based on first information regarding the reception quality of a plurality of spatial streams. A wireless transmission unit 206 (e.g., corresponding to a transmission circuit) transmits the second information regarding the determined spatial stream.

[0038] [Configuration Example of AP100] FIG. 5 is a block diagram showing a configuration example of the AP100. The AP100 shown in FIG. 5 includes, for example, a wireless reception unit 101, a decoding unit 102, a scheduling unit 103, a steering matrix generation unit 104, a data generation unit 105, a Preamble generation unit 106, and a wireless transmission unit 107.

[0039] Radio receiving section 101 receives a signal transmitted from STA 200 via an antenna, and performs radio reception processing on the received signal, such as down-conversion, A / D conversion, etc. For example, radio receiving section 101 divides the received signal after radio reception processing into a preamble section (also called a preamble signal) and a data section (also called a data signal), and outputs the divided signals to decoding section 102.

[0040] Decoding section 102 performs processing such as fast Fourier transform (FFT) on each of the preamble signal and data signal input from radio receiving section 101, for example.

[0041] The decoding unit 102 extracts, for example, a control signal (for example, a frequency bandwidth, a modulation and channel coding scheme (MCS), or an encoding method) included in the preamble signal. The decoding unit 102 also performs channel estimation using, for example, a reference signal included in the preamble signal. For example, the decoding unit 102 may generate a channel estimate matrix based on the channel estimation result. The channel estimate matrix may be, for example, N corresponding to the number of streams. ss and N, which corresponds to the number of receiving antennas of AP100. RX (N RX ×N ss ) matrix.

[0042] Decoding section 102 performs channel equalization, demodulation, and decoding of the data signal after FFT based on, for example, a control signal extracted from the preamble signal and a channel estimation matrix, and performs error detection such as cyclic redundancy check (CRC). If there is no error in the data signal (in other words, a decoding error), decoding section 102 outputs the decoded data signal to scheduling section 103 and steering matrix generation section 104. If there is an error in the data signal, decoding section 102 does not output the decoded data signal, for example.

[0043] Scheduling section 103 performs scheduling for STA 200 (in other words, in DL) based on the data signal (including, for example, a response signal or feedback information) input from decoding section 102. For example, scheduling section 103 may determine whether to perform MU-MIMO transmission. When performing MU-MIMO transmission, scheduling section 103 may determine allocation of RUs to each STA 200 (for example, users) and may determine allocation of spatial streams to each STA 200 based on the data signal input from decoding section 102. Scheduling section 103 outputs information related to the determined scheduling to steering matrix generation section 104, data generation section 105, and preamble generation section 106.

[0044] Steering matrix generation section 104 generates a steering matrix based on information related to scheduling input from scheduling section 103. The steering matrix is, for example, a matrix that imparts orthogonality to MU-MIMO signals.

[0045] Furthermore, when a data signal including feedback information (e.g., a channel estimation value or a singular vector) is input from decoding section 102, steering matrix generation section 104 may generate a new steering matrix based on the feedback information or may update a part of the steering matrix that it holds. Furthermore, when a data signal including feedback information is not input from decoding section 102, steering matrix generation section 104 may generate a steering matrix based on feedback information that it holds for each destination STA 200 (in other words, user). Furthermore, when steering matrix generation section 104 does not hold feedback information for destination STA 200, it may set, for example, a default orthogonal matrix (e.g., an identity matrix or a Hadamard matrix) as the steering matrix.

[0046] Steering matrix generation section 104 outputs information related to steering matrices applied to MU-MIMO transmission to data generation section 105 and preamble generation section 106. Steering matrix generation section 104 also stores information related to steering matrices (e.g., feedback information) in a buffer (not shown).

[0047] Data generation section 105 generates a data sequence addressed to STA 200 based on the scheduling information input from scheduling section 103. Data generation section 105 also encodes the generated data sequence based on the scheduling information. Data generation section 105 may also add information related to the steering matrix input from steering matrix generation section 104 to the encoded data sequence. Data generation section 105, for example, allocates the data sequence (e.g., the sequence to which information related to the steering matrix has been added) to a scheduled RU, performs modulation and inverse Fourier transform (IFFT) processing, and generates a data signal. Data generation section 105 outputs the generated data signal to radio transmission section 107.

[0048] Preamble generating section 106 generates a preamble signal based on the scheduling information input from scheduling section 103. For example, preamble generating section 106 may add the steering matrix input from steering matrix generating section 104 to a reference signal included in the preamble signal. Preamble generating section 106 performs modulation and IFFT processing on the preamble signal, and outputs the preamble signal to radio transmitting section 107.

[0049] The wireless transmission unit 107 generates a wireless frame (or equivalently, a packet signal) based on the data signal input from the data generation unit 105 and the Preamble signal input from the Preamble generation unit 106. The wireless transmission unit 107 performs wireless transmission processing such as D / A conversion and up-conversion to the carrier frequency on the generated wireless frame, and transmits the signal after the wireless transmission processing to the STA200 via an antenna.

[0050] <Configuration example of STA200> FIG. 6 is a block diagram showing a configuration example of the STA200. The STA200 shown in FIG. 6 includes, for example, a wireless reception unit 201, a Preamble demodulation unit 202, a data decoding unit 203, a feedback determination unit 204, a transmission signal generation unit 205, and a wireless transmission unit 206.

[0051] The wireless reception unit 201 performs wireless reception processing such as down-conversion and A / D conversion on the signal received via the antenna. The wireless reception unit 201 extracts the Preamble signal from the signal after the wireless reception processing and outputs it to the Preamble demodulation unit 202. Also, the wireless reception unit 201 extracts the data signal from the signal after the wireless reception processing and outputs it to the data decoding unit 203.

[0052] The Preamble demodulation unit 202 performs demodulation processing such as FFT on the Preamble signal input from the wireless reception unit 201, and extracts, for example, a control signal used for demodulation and decoding of the data signal from the demodulated Preamble signal. Also, the Preamble demodulation unit 202 may perform channel estimation based on the reference signal included in the Preamble signal. The Preamble demodulation unit 202 outputs the extracted control signal and the channel estimation information (for example, the channel estimation matrix) to the data decoding unit 203. Also, the Preamble demodulation unit 202 outputs the reference signal included in the Preamble signal and the channel estimation information to the feedback determination unit 204.

[0053] For example, based on the control signal and channel estimation information input from preamble demodulation section 202, data decoding section 203 performs processing such as FFT processing, channel equalization, or demodulation on the data section input from radio receiving section 201, and extracts demodulated data addressed to STA 200. Data decoding section 203 also decodes the extracted demodulated data and performs error detection such as CRC. Data decoding section 203 outputs the error result of the data signal to feedback determination section 204.

[0054] The feedback determination unit 204 determines whether or not to feed back information related to spatial streams (e.g., stream information). In other words, the feedback determination unit 204 determines, for example, a spatial stream for which stream information is to be fed back from among a plurality of spatial streams in multi-user transmission. Note that the "... determination unit" may be interchangeably read as other terms such as a "... determination unit" or a "... control unit."

[0055] For example, feedback determining section 204 generates reception quality information based on the error determination result of the data signal inputted from data decoding section 203 and the reference signal included in the preamble inputted from preamble demodulating section 202 .

[0056] The reception quality information may include, for example, information such as the error detection result of the desired (or desired) signal (e.g., a signal addressed to STA200), the signal to interference plus noise ratio (SINR) of the desired signal, the power value of the inter-user interference signal (e.g., a signal addressed to another STA other than STA200), the desired signal to undesired signal ratio (DUR) between the desired signal and the inter-user interference signal, the change in desired signal power or the change in inter-user interference signal power between the previous MU-MIMO signal and the current MU-MIMO signal, the change in desired signal power between the desired signal power of NDP sounding and the MU-MIMO signal, or the change in inter-user interference signal power.

[0057] Then, feedback determining section 204 determines, for example, whether or not the reception quality generated based on the reference signal satisfies a predetermined threshold (in other words, a condition).

[0058] When the reception quality satisfies a predetermined threshold, the feedback determination unit 204 may, for example, decide to feed back (in other words, transmit) the stream information. On the other hand, when the reception quality does not satisfy the predetermined threshold, the feedback determination unit 204 may, for example, decide not to transmit the stream information. For example, the feedback determination unit 204 may determine whether to feed back stream information for each of a plurality of spatial streams in multi-user transmission.

[0059] The feedback determination unit 204 generates feedback information including stream information related to the determined spatial stream, and outputs the generated feedback information to the transmission signal generation unit 205. The stream information may include, for example, information identifying the destination STA 200 of the spatial stream whose reception quality satisfies a predetermined threshold (for example, STA-ID), information identifying the spatial stream (for example, spatial stream index information), the SNR of the spatial stream, and a feedback matrix.

[0060] When feedback information is not input from the feedback determining section 204, the transmission signal generating section 205 generates, for example, a data sequence including a response signal to the AP 100. On the other hand, when feedback information is input from the feedback determining section 204, the transmission signal generating section 205 may generate a data sequence including a response signal to the AP 100 and the feedback information. The transmission signal generating section 205 allocates the generated data sequence to a predetermined frequency resource, performs modulation and IFFT processing, and generates a data signal (for example, a transmission signal). The transmission signal generating section 205 also adds a preamble to the data signal to generate a radio frame (packet signal), and outputs the signal to the radio transmitting section 206.

[0061] The wireless transmitting unit 206 performs wireless transmission processing such as D / A conversion and up-conversion to a carrier frequency on the wireless frame input from the transmission signal generating unit 205, and transmits the signal after wireless transmission processing to the AP 100 via an antenna.

[0062] [Example of AP and STA operation] Next, an example of the operation of the AP 100 and the STA 200 according to this embodiment will be described.

[0063] In this embodiment, in multi-user transmission, STA200 feeds back to AP100, for example, stream information corresponding to some of the spatial streams of the data section included in the non-NDP MU PPDU (for example, an MU PPDU including a data section described later) based on reception quality information of a reference signal (for example, LTF).

[0064] As an example, a method will be described below in which STA200 generates and feeds back feedback information based on part of stream information for a non-NDP MU PPDU transmitted by AP100 in multi-user transmission (e.g., DL MU-MIMO transmission) in 11ax.

[0065] FIG. 7 is a sequence diagram showing an example of the operation of the wireless communication system regarding DL MU-MIMO transmission.

[0066] 7 shows an example of the operation of DL MU-MIMO transmission between AP 100 and two STAs 200 (e.g., STA1 and STA2). Note that the number of STAs spatially multiplexed in DL MU-MIMO transmission is not limited to two, and may be three or more.

[0067] 7, the AP 100 transmits, for example, an NDPA to STA1 and STA2 (ST101). By transmitting the NDPA, the AP 100 notifies STA1 and STA2 that it will transmit an NDP following the NDPA.

[0068] STA1 and STA2 perform, for example, NDPA reception processing (ST102-1 and ST102-2). For example, STA1 and STA2 may acquire, based on NDPA, a control signal for compressing and feeding back propagation path information derived based on the NDP transmitted by AP 100. This control signal may include information related to feedback, such as, for example, bandwidth, frequency resource (also referred to as Resource Unit (RU)) index, feedback type, number of subcarrier groupings, or codebook size.

[0069] AP 100 transmits an NDP to, for example, STA1 and STA2 (ST103). The NDP may be transmitted, for example, via DL MUs. DL MU transmission may be, for example, DL MU-MIMO transmission or DL ​​Orthogonal Frequency-Division Multiple Access (OFDMA) transmission.

[0070] STA1 and STA2 perform, for example, reception processing of the NDP (ST104-1 and ST104-2). For example, STA1 and STA2 may perform channel estimation based on a reference signal (for example, LTF) included in the preamble portion of the NDP.

[0071] STA1 and STA2 generate, for example, feedback information (ST105-1 and ST105-2). STA1 and STA2 may generate the feedback information including information such as a feedback matrix or an average SNR for each spatial stream, based on, for example, a control signal obtained from the NDPA. The feedback matrix may include, for example, a channel estimate for each spatial stream, or a singular vector obtained by applying singular value decomposition (SVD) to the channel estimate.

[0072] The AP 100 may transmit a trigger frame to, for example, STA1 and STA2 (ST106). The AP 100 may use, for example, an NDP Feedback Report Poll trigger frame to notify the STA1 and STA2 of a control signal and transmission timing for transmitting feedback information to the UL MU. This control signal may include information regarding the transmission of the feedback information, such as bandwidth, transmit power, assigned RU, MCS, or assigned spatial stream.

[0073] STA1 and STA2 perform, for example, a process of receiving the trigger frame (ST107-1 and ST107-2). Upon receiving the trigger frame, STA1 and STA2 obtain, for example, a control signal for transmitting feedback information via UL MU-MIMO.

[0074] STA1 and STA2 transmit feedback information to AP 100, for example, based on the timing indicated by the trigger frame (ST108-1 and ST108-2). The feedback information may be transmitted by UL MU-MIMO, for example.

[0075] AP 100 receives signals (for example, UL MU-MIMO signals) transmitted from STA1 and STA2, and acquires feedback information (ST109).

[0076] AP 100 performs scheduling for STA1 and STA2 based on, for example, the feedback information (ST110). For example, when AP 100 performs DL MU-MIMO transmission to STA1 and STA2, AP 100 may generate steering matrices based on the feedback information. AP 100 may also perform null control on the steering matrices to reduce interference between the feedback information.

[0077] AP 100 transmits DL MU-MIMO signals (e.g., DL MU PPDUs) to STA1 and STA2 (ST111). For example, AP 100 may add steering matrices to the DL MU MIMO signals (e.g., the reference signal and data portion included in the preamble portion) and transmit them. AP 100 also stores the generated steering matrices in a buffer (not shown), for example.

[0078] STA1 and STA2 perform reception processing of the DL MU-MIMO signal (ST112-1 and ST112-2). For example, STA1 and STA2 perform channel estimation based on a reference signal included in the preamble section of the DL MU-MIMO signal and extract a signal addressed to each STA 200. Furthermore, STA1 and STA2 may measure the reception quality of a reference signal addressed to themselves (e.g., a "desired signal") and a reference signal addressed to another STA that is spatially multiplexed in the same RU as their own (e.g., a "multi-user interference signal"), based on the reference signal included in the preamble section of the DL MU-MIMO signal.

[0079] The reception quality may be, for example, a value such as the error determination result of the desired signal (in other words, the decoding error determination result), the SINR of the desired signal, the power value of the inter-user interference signal, the DUR between the desired signal and the inter-user interference signal, or the amount of change in the desired signal power (or the inter-user interference signal power) between the previous MU-MIMO signal and the current MU-MIMO signal.

[0080] STA1 and STA2 determine whether to transmit feedback information for each stream (in other words, feedback decision) based on, for example, the measured reception quality (ST113-1 and ST113-2).

[0081] Fig. 8 is a flowchart showing an example of feedback decision based on reception quality. In Fig. 8, as an example, information related to reception quality (e.g., corresponding to first information) includes an error decision result of the desired signal, SINR, DUR, inter-user interference signal power Pi, amount of change in desired signal power ΔPd, and amount of change in inter-user interference signal power ΔPi. Note that in Fig. 8, thresholds corresponding to each reception quality may be different values.

[0082] In FIG. 8, the input for the feedback decision process in STA 200 may include, for example, a desired signal and an inter-user interference signal for STA 200 (STA1 or STA2) (ST201).

[0083] For example, STA 200 determines whether the desired signal contains a decoding error (ST202). If the desired signal does not contain a decoding error (ST202: NO), STA 200 determines whether the SINR of the desired signal is less than a threshold (ST203).

[0084] If the SINR of the desired signal is equal to or greater than the threshold (ST203: NO), STA200 does not output feedback information (ST204). In other words, if STA200 receives a desired signal with no decoding error and an SINR equal to or greater than the threshold, it determines not to transmit feedback information.

[0085] On the other hand, if the desired signal contains a decoding error (ST202: YES) or if the SINR of the desired signal is less than the threshold (ST203: YES), STA 200 determines whether DUR is less than the threshold (ST205). If DUR is less than the threshold (ST205: YES), STA 200 outputs feedback information of the inter-user interference signal (ST206). In other words, if DUR is less than the threshold, STA 200 determines to transmit feedback information of the inter-user interference signal that causes greater interference to the desired signal.

[0086] If DUR is equal to or greater than the threshold (ST205: NO), STA 200 determines whether or not the inter-user interference signal power Pi is greater than the threshold (ST207). If the inter-user interference signal power Pi is greater than the threshold (ST207: YES), STA 200 outputs feedback information of the inter-user interference signal (ST208).

[0087] If the inter-user interference signal power Pi is equal to or less than the threshold (ST207: NO), the STA 200 determines whether the change in desired signal power ΔPd is greater than the threshold (ST209). If the change in desired signal power ΔPd is greater than the threshold (ST209: YES), the STA 200 outputs feedback information of the desired signal (ST210).

[0088] If the amount of change ΔPd in ​​desired signal power is equal to or less than the threshold (ST209: NO), STA200 determines whether the amount of change ΔPi in inter-user interference signal power is greater than the threshold (ST211). If the amount of change ΔPi in inter-user interference signal power is greater than the threshold (ST211: YES), STA200 outputs feedback information of the inter-user interference signal (ST212). On the other hand, if the amount of change ΔPi in inter-user interference signal power is equal to or less than the threshold (ST211: NO), STA200 does not output anything.

[0089] 8, STA 200 determines to feed back stream information related to the inter-user interference signal when, for example, the ratio of the desired signal to the inter-user interference signal (for example, DUR) is less than a threshold, or when the inter-user interference signal power or the amount of change in the inter-user interference signal power is greater than a threshold. Also, STA 200 determines to feed back stream information related to the desired signal when, for example, the amount of change in the desired signal power is greater than a threshold.

[0090] An example of the operation for determining (or deciding) the information to be fed back based on the reception quality has been described above.

[0091] In this way, STA200 (e.g., STA1 and STA2) determines the feedback of stream information based on information on the reception quality of the desired signal and the inter-user interference signal. The stream information may include, for example, information notifying the destination STA of the spatial stream, such as a STA-ID or a spatial stream index, or information indicating an estimation result, such as a feedback matrix or SNR. For example, when the desired signal and the inter-user interference signal include multiple spatial streams, STA200 may perform the above-mentioned feedback determination (in other words, checking the conditions for reception quality) for each spatial stream. Through the feedback determination, STA200 determines, from among the multiple spatial streams, a spatial stream for which stream information is to be fed back.

[0092] In FIG. 7, it is assumed, as an example, that STA1 has stream information to feed back (feedback: present), and STA2 has no stream information to feed back (feedback: absent).

[0093] 7, STA1 and STA2 transmit response signals (e.g., Block ACK) to the DL MU-MIMO signal (ST114-1 and ST114-2). Also, STA1, which transmits feedback information, acquires new carrier sense, for example, and transmits the feedback information to AP 100 (ST115-1).

[0094] Note that the stream information included in the feedback information may be, for example, information about a desired signal or information about a multi-user interference signal, as shown in Fig. 8. Alternatively, the stream information may be information about a combination of a desired signal and a multi-user interference signal. Furthermore, the stream information included in the feedback information may be, for example, information about all spatial streams whose reception quality satisfies a predetermined threshold, or information about some of the spatial streams whose reception quality satisfies a predetermined threshold.

[0095] The AP 100 performs a receiving process on the feedback information transmitted from the STA 1 (ST116). For example, the AP 100 identifies the STA to which the fed back stream information relates, based on the STA-ID or spatial stream index information included in the feedback information.

[0096] AP 100 performs scheduling processing (ST117). For example, AP 100 may update the steering matrix it holds based on newly acquired feedback information from STA1 and store the updated steering matrix in a buffer. AP 100 may also change (e.g., update) the scheduling of DL MU-MIMO transmission (e.g., RU allocation or user allocation) based on the feedback information, for example.

[0097] AP 100 transmits DL MU-MIMO signals (including DL MU PPDUs, for example) to STA1 and STA2 based on, for example, the updated steering matrices (ST118).

[0098] An example of the operation of the wireless communication system regarding DL MU-MIMO transmission has been described above.

[0099] For example, as shown in FIG. 9, assume that one AP 100 equipped with four transmitting antennas transmits an MU PPDU, to which one spatial stream (SS) is assigned each, to four STAs 200 (e.g., STA1 to STA4) equipped with one receiving antenna.

[0100] Each of STA1 to STA4 performs channel estimation based on, for example, a reference signal included in the received MU PPDU, and determines whether the reference signal satisfies a condition related to reception quality (see, for example, FIG. 8) based on the channel estimation result.

[0101] Here, the reference signals used for channel estimation include one desired signal addressed to each STA 200 and three inter-user interference signals addressed to other STAs 200. For example, when a certain STA 200 satisfies a condition regarding the reception quality of reference signals corresponding to one desired signal and one inter-user interference signal, the STA 200 transmits, to the AP 100, feedback information including stream information regarding two spatial streams corresponding to these two signals. In other words, the STA 200 does not feed back stream information regarding spatial streams corresponding to the other two signals that do not satisfy the reception quality condition. In this case, for example, the size of the feedback information (e.g., feedback matrix) transmitted by the STA 200 is 2×1 (e.g., N in Equation (1)) from Equation (1). r =2, N c =1).

[0102] Here, assuming that in FIG. 9, a STA receives an NDP transmitted under the same conditions as an MU PPDU in the above-mentioned NDP sounding, the size of the feedback information (e.g., feedback matrix) transmitted by the STA is 4×1 according to equation (1), so in this embodiment, the amount of feedback can be reduced.

[0103] Each of STA1 to STA4 shown in Fig. 9 may determine the spatial streams for transmitting feedback information through the above-mentioned operation. For example, each of STA1 to STA4 may transmit feedback information for all four spatial streams, or may transmit feedback information for some of the spatial streams. Also, for example, each of STA1 to STA4 may not need to transmit feedback information for all spatial streams.

[0104] In other words, for example, in multi-user transmission, STA1 to STA4 may feed back a portion of stream information corresponding to each of the multiple spatial streams of the data section included in the non-NDP MU PPDU based on the reception quality of the reference signal included in the non-NDP MU PPDU.

[0105] By this feedback, each of STA1 to STA4 can determine the feedback of stream information corresponding to spatial streams that satisfy the conditions regarding reception quality, and can determine not to transmit stream information corresponding to spatial streams that do not satisfy the conditions regarding reception quality. Therefore, it is possible to reduce the overhead of feedback information transmitted from each STA 200. Furthermore, it is possible to reduce the frequency of beamforming processing by NDP sounding, for example.

[0106] Furthermore, STA1 to STA4 can feed back stream information at a timing that satisfies a condition related to reception quality, in other words, at an appropriate timing for updating a steering matrix in AP 100. In other words, STA1 to STA4 can autonomously determine the timing for feeding back stream information based on reception quality.

[0107] Note that, in the example illustrated in Fig. 9, the STA 200 transmits feedback matrices related to one desired signal and one inter-user interference signal, but the feedback information is not limited to these signals (in other words, a combination of signals). For example, in Fig. 9, the STA 200 may transmit feedback matrices related to two inter-user interference signals with larger signal levels (e.g., received power) among three inter-user interference signals, without including the desired signal.

[0108] Next, methods 1-1 to 1-5 will be described as examples of the method of feeding back stream information in STA 200.

[0109] [Method 1-1] In method 1-1, the STA 200 includes stream information in a signal in a compressed beamforming / CQI frame Action field format and feeds it back to the AP 100.

[0110] FIG. 10 shows an example of a compressed beamforming / CQI frame Action field format when feeding back stream information in method 1-1.

[0111] In method 1-1, as shown in FIG. 10, STA200 includes the first index (e.g., called the "start spatial stream index (Start SS index)") among the indexes of the spatial streams corresponding to the stream information to be fed back in the Sounding Dialog Token Number field of the HE MIMO Control field.

[0112] In other words, the AP 100 and the STA 200 read the Sounding Dialog Token Number field of the HE MIMO Control as the Start SS index field.

[0113] For example, STA200 is c The STA 200 may notify the AP 100 of spatial stream index information corresponding to feedback information (e.g., feedback matrix) regarding spatial streams by the Start SS index. For example, the STA 200 may notify the AP 100 of spatial stream index information corresponding to feedback information (e.g., feedback matrix) regarding spatial streams from the Start SS index to (Start SS index + N c - N up to 1) c The feedback information may include feedback matrices corresponding to the spatial streams, and may be transmitted. Note that the feedback information may include, for example, a feedback matrix for each tone.

[0114] For example, as shown in Figure 10, c The feedback information corresponding to the spatial streams may be included in at least one of an HE Compressed Beamforming Report field and an HE MU Exclusive Beamforming Report field.

[0115] For example, in 11ax, STAs can receive data from the first spatial stream index, from 1 to N. c N up to c In contrast, in method 1-1, STA 200 feeds back information about spatial streams from the Start SS index to (Start SS index + N c - N up to 1) c In other words, in method 1-1, STA 200 can determine not to transmit information about spatial streams with spatial stream indexes from the top 1 (Start SS index-1).

[0116] Therefore, according to method 1-1, for example, the amount of feedback in the HE Compressed Beamforming Report field or the HE MU Exclusive Beamforming Report field can be reduced.

[0117] 10 may include, for example, a value obtained by copying the value of the Sounding Dialogue Token included in the NDPA. In method 1-1, for example, as shown in FIG. 7 (for example, the processing of ST111), STA 200 makes a feedback decision based on the reception quality of a reference signal included in a MU-MIMO signal, and therefore NDPA is not transmitted. Therefore, for example, by replacing the Sounding Dialogue Token Number field with the Start SS index field, STA 200 can include stream information in the compressed beamforming / CQI frame Action field format and provide feedback.

[0118] The area (for example, field) to which the Start SS index is assigned is not limited to the Sounding Dialog Token Number field, and may be, for example, another area that is not used in part or in whole during the feedback determination process.

[0119] [Method 1-2] In method 1-2, the STA 200, for example, feeds back information identifying the destination STA of the spatial stream to the AP 100. In other words, in method 1-2, the STA 200 does not feed back feedback information such as a feedback matrix or an SNR to the AP 100.

[0120] The "information identifying the destination STA of the spatial stream" may include, for example, a "STA-ID" corresponding to the STA200 assigned to the spatial stream for which feedback of stream information has been determined, or a "spatial stream index (SS index)" corresponding to the spatial stream for which feedback of stream information has been determined.

[0121] Furthermore, when STA 200 feeds back information identifying the destination STA of the spatial stream, for example, as shown in FIG. 11, a frame format according to the value of the "HE Action field" may be applied.

[0122] For example, when the value of the HE Action field is 0, the STA 200 may apply the HE Compressed Beamforming / CQI frame Action field format shown in Fig. 2. Also, when the value of the HE Action field is any one of 3 to 6, the STA 200 may apply a frame format that feeds back information that identifies the destination STA of the spatial stream.

[0123] (a) to (d) of FIG. 12 show examples of frame formats that are applied when the value of the HE Action field is 3 to 6, respectively.

[0124] FIG. 12(a) shows an example of a frame format "STA-ID feedback frame format" when the information specifying the destination STA of the spatial stream includes a STA-ID (for example, when the value of the HE Action field is 3).

[0125] 12(a) includes, for example, the STA-ID of the STA assigned to the spatial stream for which the STA 200 has decided to feed back stream information. For example, when the STA 200 feeds back stream information related to one or more spatial streams assigned to a single STA, the STA 200 may include the STA-ID of the corresponding STA in the STA-ID field shown in FIG. 12(a) and feed it back (in other words, notify) to the AP 100.

[0126] Figure 12(b) shows an example of a frame format "Continuous SS index feedback frame format" when the information identifying the destination STA of the spatial stream includes a spatial stream index (SS index) (for example, when the value of the HE Action field is 4).

[0127] The frame format shown in Fig. 12(b) includes, for example, a "Start SS index" indicating the first spatial stream index and an "End SS index" indicating the last spatial stream index of the spatial streams for which the STA 200 has decided to feed back stream information. For example, when the STA 200 feeds back stream information related to multiple spatial streams allocated across multiple STAs, the STA 200 may include the first and last indexes of the corresponding spatial stream indexes (SS index) in the Start SS index field and End SS index field shown in Fig. 12(b), respectively, and feed them back to the AP 100.

[0128] In addition, the continuous stream information notified by the Continuous SS index feedback frame format may specify multiple spatial streams across multiple STAs 200, or may specify multiple spatial streams assigned to one STA 200.

[0129] Also, in FIG. 12(b), for example, instead of the “End SS index field” indicating the end spatial stream index, a field indicating the number of spatial streams (for example, N ss field) may be set.

[0130] FIG. 12(c) shows that the information specifying the destination STA of the spatial stream includes N ss An example of the frame format "Individual SS index feedback frame format" when spatial stream indices (SS index) are included (for example, when the value of the HE Action field is 5) is shown below.

[0131] The frame format shown in FIG. 12(c) includes, for example, "N" indicating the number of spatial streams for which the STA 200 has decided to feed back stream information. ss " and N ss "SS index 1" to "SS index N" indicate the spatial stream indexes. ss " is included.

[0132] N notified by the Individual SS index feedback frame format ss The stream information may specify multiple spatial streams across multiple STAs 200, or may specify multiple spatial streams assigned to one STA 200. ss The spatial stream index (SS index) corresponding to each piece of stream information may include consecutive values ​​and non-consecutive values.

[0133] FIG. 12(d) shows that the information specifying the destination STA of the spatial stream includes N sta An example of the frame format "SS index feedback for each STA frame format" when a spatial stream index (SS index) for each STA is included (for example, when the value of the HE Action field is 6) is shown below.

[0134] The frame format shown in FIG. 12(d) includes, for example, N sta Each STA Info field includes a "STA Info field" indicating information about the spatial stream index for each STA. Each STA Info field includes, for example, a "Start SS index field" indicating the start spatial stream index and an "N" field indicating the number of spatial streams. ss field" may be included.

[0135] For example, for each STA that feeds back stream information, the STA 200 may store the start index of the corresponding spatial stream and the number of streams in the Start SS index field and N SS index field shown in FIG. 12(d). SS In other words, the STA 200 may include the stream information in the Start SS index to (Start SS index + N SS - Stream information (for example, spatial stream index) for each STA indicated by 1) is notified to the AP 100.

[0136] In FIG. 12(d), for example, N ss Instead of the field, for example, an "End SS index field" indicating the end spatial stream index may be set, as in FIG. 12(b).

[0137] Furthermore, the Category field included in FIGS. 12(a) to 12(d) may indicate, for example, the type of Action frame.

[0138] For example, upon receiving information identifying the destination STAs of the spatial streams described above, the AP 100 may update the scheduling or steering matrix of the DL MU-MIMO transmission.

[0139] For example, as shown in FIG. 8, the spatial streams for which stream information is fed back may be spatial streams (or STAs) corresponding to signals (for example, inter-user interference signals) that may cause interference to a desired signal.

[0140] Therefore, for example, AP100 may schedule the STA that sent the feedback information and the STA identified based on the stream information (e.g., STA_ID or SS index) included in the feedback information so that they are not multi-user multiplexed into the same RU.

[0141] Also, for example, the AP 100 may change the spatial stream indexes allocated for DL ​​MU-MIMO so as not to use the spatial stream indexes (or the spatial streams corresponding to the STA_ID) included in the feedback information.

[0142] In method 1-2, the feedback information includes information about the spatial stream to be fed back (in other words, information identifying the destination STA of the spatial stream), which includes information identifying index information (e.g., STA_ID or SS index). In other words, the feedback information does not include information such as a feedback matrix or SNR. Therefore, according to method 1-2, the amount of feedback can be reduced compared to when information such as a feedback matrix or SNR is fed back (e.g., the Compressed beamforming / CQI frame Action field format, which is the feedback format of 11ax).

[0143] [Method 1-3] In methods 1-3, the STA 200 transmits feedback information by including it in a response signal (for example, ACK or Block ACK) or a negative acknowledgment signal (Negative-ACK (NACK)) in response to received data (for example, MU PPDU).

[0144] FIG. 13(a) shows an example of a frame format "BA frame format" applied to the transmission of ACK (or Block ACK) and NACK in methods 1-3.

[0145] In the BA frame format shown in FIG. 13(a), for example, fixed-length feedback information is included in the "Feedback info field."

[0146] 13(b), for example, STA200 transmits a response signal (e.g., BA) (e.g., UL MU transmission) in response to the MU PPDU transmitted from AP100. At this time, for example, if STA200 has feedback information to transmit (e.g., STA1), STA200 may transmit the BA and the feedback information in a BA frame format. Also, STA200 (e.g., STA2) may not include feedback information in the Feedback info field of the BA frame format.

[0147] FIG. 14(a) shows an example of an "ACK frame format" that is applied to the transmission of ACK (or Block ACK) and NACK in methods 1-3.

[0148] The ACK frame format shown in Fig. 14(a) includes, for example, a "Feedback field" indicating variable-length feedback information. The ACK frame format shown in Fig. 14(a) also includes, for example, a "Feedback present field" indicating the presence or absence of feedback information. The Feedback present field has, for example, a fixed length.

[0149] For example, if the Feedback present field indicates the presence of feedback information in the ACK frame format, the Feedback field includes a "Feedback length field" and a "Feedback info field." The Feedback length field is, for example, a fixed-length field that indicates the length (e.g., the number of bits) of the variable-length Feedback info field. Also, for example, if the Feedback present field does not indicate the presence of feedback information in the ACK frame format, the length of the Feedback field is 0 bit.

[0150] For example, as shown in FIG. 14(b), the STA200 transmits a signal including an ACK frame format based on a BA request (BAR) transmitted from the AP100 to each STA200 (e.g., STA1 and STA2). For example, in FIG. 14(b), STA1 transmits an ACK frame format including an ACK and feedback information to the AP100. Also, for example, in FIG. 14(b), STA2 transmits an ACK frame format including an ACK to the AP100 without including feedback information.

[0151] According to method 1-3, STA 200 transmits a response signal (or a negative response signal) including feedback information (for example, stream information). Therefore, according to method 1-3, STA 200 can transmit the response signal and feedback information together to AP 100, thereby reducing the overhead of the preamble section.

[0152] [Method 1-4] In methods 1-4, the STA 200 transmits to the AP 100 a signal (hereinafter referred to as a "Trigger request") requesting transmission of a trigger frame that prompts the STA 200 to transmit feedback information. In other words, the STA 200 requests the AP 100, which is the transmission source of multiple spatial streams in multi-user transmission, to transmit a signal that triggers transmission of feedback information including stream information.

[0153] FIG. 15 is a sequence diagram showing an example in which the STA 200 transmits a Trigger request to the AP 100. In FIG.

[0154] For example, when the STA 200 (for example, STA 1) generates feedback information based on the MU PPDU received from the AP 100, the STA 200 transmits a Trigger request to the AP 100.

[0155] The timing of transmitting the Trigger request may be, for example, the timing after transmitting a response signal (for example, ACK) to the AP 100. Furthermore, the STA 200 may transmit the Trigger request to the AP 100 after newly acquiring carrier sense, for example.

[0156] In addition, STA 200 may include, for example, parameters related to the feedback information (for example, the length of the feedback information) in the Trigger request.

[0157] In addition, the STA 200 may transmit, for example, a Trigger request included in a response signal or a negative response signal.

[0158] When the AP 100 receives a Trigger request, it transmits a Trigger frame requesting the transmission of feedback information to the STA 200 (STA1 in FIG. 15) that sent the Trigger request. The Trigger frame may be, for example, a Beamforming Report Poll. The AP 100 may also transmit the Trigger frame only when it has received Trigger requests from a predetermined number or more of STAs 200.

[0159] When the STA 200 receives the trigger frame transmitted from the AP 100, the STA 200 transmits feedback information to the AP 100 based on, for example, a control signal included in the trigger frame. The control signal included in the trigger frame may include information related to the transmission of feedback information, such as, for example, bandwidth, transmission power, assigned RU, MCS, or assigned spatial stream.

[0160] Furthermore, the AP 100 may include, for example, an additional control signal in a trigger frame (for example, a Trigger Dependent Common Info field) when the STA 200 transmits feedback information. The additional control signal may include, for example, information such as a feedback type, the number of subcarrier groupings, or a codebook size.

[0161] According to method 1-4, when feedback information is transmitted from the STA 200, the AP 100 can control the transmission timing or transmission parameters of the feedback information, thereby improving the reception quality of the feedback information.

[0162] [Method 1-5] In method 1-5, the STA 200 transmits a signal notifying the transmission of feedback information (hereinafter referred to as "Feedback present") to the AP 100. In other words, the STA 200 notifies the AP 100, which is the transmission source of multiple spatial streams in multi-user transmission, of the transmission of feedback information including stream information.

[0163] FIG. 16 is a sequence diagram showing an example of a case where the STA 200 transmits Feedback present.

[0164] For example, in FIG. 16, for an MU PPDU transmitted by AP 100, if there is significant interference from a signal addressed to STA2 to a signal addressed to STA1, STA1 may fail to decode the signal, while STA2 may succeed in decoding the signal.

[0165] At this time, STA1 may generate feedback information including stream information regarding the spatial stream corresponding to the signal addressed to STA2. In methods 1-5, STA1 transmits a Feedback present to AP 100 before transmitting the feedback information. For example, STA1 may transmit the Feedback present to AP 100 after a Short Inter-frame Space (SIFS) has elapsed since STA2 transmitted a response signal (e.g., an ACK) to AP 100.

[0166] When AP 100 receives Feedback present, it suspends transmission of MU-MIMO signals including STA1 for a certain period of time until it updates the steering matrix based on the feedback information from STA 1. In other words, AP 100 determines that even if it transmits an MU-MIMO signal addressed to STA 1 based on the steering matrix held for STA 1, there is a high possibility that decoding will fail in STA 1, and suspends signal transmission to STA 1 until the steering matrix is ​​updated.

[0167] After transmitting Feedback present, STA1 transmits feedback information. STA1 may transmit the feedback information after newly acquiring carrier sense, for example. STA1 may also include Feedback present in a response signal or a negative response signal.

[0168] According to methods 1-5, STA 200 notifies AP 100 in advance of transmitting feedback information, thereby enabling AP 100 to suppress MU-MIMO transmission based on a suboptimal steering matrix (e.g., a steering matrix before updating). As a result, AP 100 can suppress retransmissions caused by decoding errors in STA 200, thereby improving system throughput.

[0169] An example of a method for feeding back stream information in STA 200 has been described above.

[0170] As described above, in this embodiment, STA200 determines a spatial stream for feeding back stream information from among a plurality of spatial streams in multi-user transmission, and transmits the stream information corresponding to the determined spatial stream.

[0171] By transmitting this stream information (in other words, feedback), the STA 200 can transmit, for example, feedback information corresponding to a spatial stream whose actual reception quality (for example, quality measured by the STA 200) may differ from the reception quality recognized by the AP 100 to the AP 100. In other words, the STA 200 can determine not to transmit feedback information corresponding to a spatial stream whose actual reception quality and the reception quality recognized by the AP 100 are either no different or may be treated as no different. Thus, according to the present embodiment, the amount of feedback information transmitted by the STA 200 can be reduced, thereby improving transmission efficiency.

[0172] Furthermore, for example, for each spatial stream, the STA 200 can transmit feedback information to the AP 100 at a timing when the actual reception quality and the reception quality recognized by the AP 100 may differ. Therefore, according to the present embodiment, for example, it is possible to reduce the transmission of feedback information at a timing when the actual reception quality and the reception quality recognized by the AP 100 are the same or may be treated as the same, thereby improving transmission efficiency.

[0173] As described above, according to this embodiment, the transmission efficiency can be improved in spatial multiplexing transmission such as MU-MIMO transmission.

[0174] (Embodiment 2) [Configuration of Wireless Communication System] A wireless communication system according to an embodiment of the present disclosure includes at least one AP 300 and a plurality of STAs 400.

[0175] For example, in DL communication (e.g., transmission and reception of DL data), the AP 300 (or also referred to as "downlink wireless transmission device") may perform DL MU-MIMO transmission to a plurality of STAs 400 (or also referred to as "downlink wireless reception devices"). Each STA 400 may generate feedback information based on, for example, a signal transmitted by DL MU-MIMO (e.g., DL MU PPDU), and transmit the feedback information to the AP 300 (e.g., UL SU transmission or UL MU transmission).

[0176] In this embodiment, based on the reception quality of a reference signal (e.g., LTF) included in the non-NDP MU PPDU by the STA 400, the STA 400 feeds back to the AP 300 the channel coefficient regarding the spatial stream of one or some of the inter-user interference signals. The channel coefficient is, for example, one component in the channel estimation matrix represented by RX ×N ss Further, the channel coefficient is, for example, a part of the subcarriers represented by s Note that N s indicates the number of subcarriers assigned to the STA 400.

[0177] [Example of Configuration of AP 300] FIG. 17 is a block diagram showing an example of the configuration of the AP 300. In FIG. 17, the same components as those in Embodiment 1 (FIG. 5) are denoted by the same reference numerals, and the description thereof is omitted. For example, compared with the AP 100 (FIG. 5), the AP 300 includes a reference signal holding unit 301, and the operation of the steering matrix generation unit 302 (e.g., the operation regarding the channel coefficient (or reference signal)) is different.

[0178] When the reference signal is included in the data signal input from the decoding unit 102, the reference signal holding unit 301 stores the reference signal in the buffer. When the steering matrix generation unit 302 updates the steering matrix, the reference signal holding unit 301 outputs the reference signal held in the buffer to the steering matrix generation unit 302.

[0179] Here, the "reference signal" may be, for example, any of the channel coefficients included in the estimated channel estimation matrix. For example, the reference signal may use the channel coefficient related to the desired signal stream whose power is above a threshold value (for example, the maximum power). Also, the reference signal may use, for example, the channel estimation value related to a predetermined signal transmitted prior to the reference signal used for channel estimation. The predetermined signal may include, for example, Legacy-short training field (L-STF) or L-LTF, non-legacy STF. Also, the predetermined signal may be, for example, a signal sequence newly added to the Preamble section.

[0180] The steering matrix generation unit 302 generates a steering matrix based on the scheduling-related information input from the scheduling unit 103.

[0181] Also, when a data signal including feedback information (for example, normalized channel coefficients) is input from the decoding unit 102, the steering matrix generation unit 302 may newly generate a steering matrix based on the feedback information or update a part of the held steering matrix. Also, when the steering matrix generation unit 302 updates the existing steering matrix based on the feedback information, for example, it may normalize the existing steering matrix based on the reference signal input from the reference signal holding unit 301 and adjust the amplitude and phase between the feedback information.

[0182] <Configuration example of STA400> Fig. 18 is a block diagram showing an example configuration of STA 400. In Fig. 18, the same components as those in embodiment 1 (Fig. 6) are denoted by the same reference numerals, and their description will be omitted. For example, STA 400 differs from STA 200 (Fig. 6) in that it includes reference signal holding section 402 and in the operation of feedback determination section 401.

[0183] The feedback determination unit 401 determines whether or not to feed back information related to spatial streams (for example, stream information). In other words, the feedback determination unit 401 determines, for example, a spatial stream for which stream information is to be fed back from among a plurality of spatial streams in multi-user transmission.

[0184] For example, feedback determining section 401 generates reception quality information based on the error determination result of the data signal inputted from data decoding section 203 and the reference signal included in the preamble inputted from preamble demodulating section 202 .

[0185] Furthermore, the feedback determining unit 401 determines whether or not a predetermined threshold (in other words, a condition) is satisfied for each component (e.g., corresponding to a channel coefficient) of the reception quality (e.g., a channel estimation matrix) generated based on the reference signal.

[0186] When the channel coefficient satisfies a predetermined threshold, the feedback determination unit 401 determines, for example, to feed back (in other words, transmit) stream information. On the other hand, when the channel coefficient does not satisfy the predetermined threshold, the feedback determination unit 401 determines, for example, not to transmit stream information. For example, the feedback determination unit 401 may determine whether to feed back stream information for channel coefficients related to multiple spatial streams in multi-user transmission.

[0187] The feedback determining unit 401 generates feedback information including stream information corresponding to the channel coefficients related to the determined spatial streams, for example, and outputs the feedback information to the transmission signal generating unit 205 .

[0188] The feedback information may include, for example, estimated channel coefficients, spatial stream indexes for identifying the channel coefficients, receive antenna indexes, subcarrier indexes, or RU indexes. Furthermore, for example, the channel coefficients included in the feedback information may be relative values ​​with respect to a reference signal. For example, the channel coefficients fed back may be values ​​normalized by the reference signal.

[0189] For example, when a reference signal is newly determined, feedback determining section 401 adds the reference signal to feedback information. Also, when there is no reference signal component that satisfies a threshold value related to predetermined reception quality information (in other words, when there is no feedback information), feedback determining section 401 does not output a signal to transmission signal generating section 205. Also, when a reference signal is newly determined, feedback determining section 401 outputs the reference signal to reference signal holding section 402.

[0190] Reference signal holding section 402 stores in a buffer the reference signal input from feedback determination section 401. Furthermore, when feedback determination section 401 includes a channel coefficient in the feedback information and feeds it back, reference signal holding section 402 outputs the reference signal held in the buffer to feedback determination section 401.

[0191] [Example of AP and STA operation] Next, an example of the operation of the AP 300 and the STA 400 according to this embodiment will be described.

[0192] For example, as shown in FIG. 19, assume that one AP 300 equipped with three transmitting antennas transmits an MU PPDU to three STAs 400 (e.g., STA1, STA2, and STA3) equipped with one receiving antenna, each of which is assigned one spatial stream (SS).

[0193] At this time, the received signals at STA1 to STA3 are expressed, for example, as in the following equation (2).

number

[0194] Here, x represents a transmission signal component, y represents a reception signal component, w represents a steering matrix component, and h represents a channel estimation matrix component. For example, reception signal component y1 at STA1 is expressed as in the following equation (3).

number

[0195] The coefficients of the transmission signal components x1, x2, and x3 in equation (3) are effective channel coefficients, which are defined, for example, as equations (4), (5), and (6) below.

number

number

number

[0196] Furthermore, by using equations (4), (5) and (6), for example, the channel coefficient h 13 is expressed as the following equation (7).

number

[0197] From equation (7), the channel coefficient h 13 is, for example, a known steering matrix and effective channel coefficients (e.g., h eff11 , h eff12 and h eff13 ) and other channel coefficients h 11 and h 12 can also be derived in the same way as equation (7).

[0198] For example, assume that, based on measurement of the reference signal of the MU-PPDU received at STA1 shown in Fig. 19, the power of the reference signal corresponding to the inter-user interference signal addressed to STA2 is large (for example, equal to or greater than a threshold) and the power of the reference signal corresponding to the inter-user interference signal addressed to STA3 is small (for example, less than a threshold). In this case, for example, STA1 determines to feed back stream information related to the inter-user interference signal addressed to STA2.

[0199] For example, STA1 estimates the effective channel coefficient h related to the inter-user interference signal of STA2 from among the effective channel coefficients obtained by channel estimation. eff12 Then, STA1 normalizes the normalized effective channel coefficient h' based on the reference signal. eff12 and feedback information including the reference signal may be transmitted to the AP 300.

[0200] The AP 300 calculates the normalized effective channel coefficient h' from the feedback information received from the STA 1. eff12 and the reference signal. The AP 300 obtains the normalized effective channel coefficient h' eff12 and separates the steering matrix based on the channel estimates (e.g., the channel coefficients h 13 ) is derived.

[0201] At this time, the AP 300 may, for example, use the effective channel coefficient h eff11 is the effective channel coefficient h eff12 Therefore, the AP 300 determines that the fluctuation due to the propagation path fluctuation is small compared to the channel coefficient (for example, h 11 , h 12 and h 13 ) and a known steering matrix (e.g., w 11 , w 21 and w 31 ) to obtain the effective channel coefficients h eff11 (See, for example, equation (4)).

[0202] In addition, the AP 300 calculates, for example, the inter-user interference signal of STA3 that is not included in the feedback information as the effective channel coefficient h eff13 Since interference is sufficiently suppressed by |h eff13 You can treat it as |≒0.

[0203] In this way, the AP 300 calculates, for example, the channel coefficient h 13 Regarding the derivation of the effective channel coefficient h eff12 (e.g., the normalized effective channel coefficient h' eff12 ), and the channel coefficients h 13 The AP 300 can derive the channel coefficient h 13 Other channel coefficients may be derived in a similar manner to the derivation of .

[0204] The AP 300 may, for example, newly calculate steering matrix elements based on the derived channel coefficients. For example, the newly calculated steering matrix elements may be elements that suppress interference caused by a signal addressed to STA2 on a signal addressed to STA1.

[0205] The AP 300 then updates the steering matrix based on the calculated steering matrix components, and may adjust at least one of the phase and amplitude between the newly calculated steering matrix components and the existing steering matrix by normalizing the existing steering matrix based on the reference signal.

[0206] In this embodiment, the STA 400 generates feedback information based on, for example, channel coefficients (e.g., effective channel coefficients) related to some signals (e.g., inter-user interference signals) among channel estimates (e.g., channel estimation matrices) related to spatial streams in multi-user transmission. In other words, the STA 400 generates feedback information based on, for example, some components of the channel estimates of the spatial streams (in the above example, the effective channel coefficients h' eff12 ) to the AP 300.

[0207] By generating this feedback information, it is possible to reduce the overhead of the feedback information compared to, for example, the case where a channel estimation value is fed back for each spatial stream. For example, when the amount of feedback information is minimized, the STA 400 only needs to generate feedback information including one effective channel coefficient for each tone or group of tones, thereby reducing the overhead of the feedback information.

[0208] Furthermore, the STA 400 can directly obtain the effective channel coefficients based on, for example, a reference signal included in a non-NDP MU PPDU transmitted from the AP 300, and therefore can easily generate feedback information.

[0209] In addition, the STA 400 normalizes the effective channel coefficients by a specified value (e.g., a reference signal) and feeds back the reference signal to the AP 300. By feeding back the normalized values, the AP 300 can adjust the amplitude and phase between the feedback information and the information it holds (e.g., steering matrix components), for example, when updating a steering matrix.

[0210] Next, method 2-1 will be described as an example of a method for feeding back stream information in STA 400.

[0211] [Method 2-1] In method 2-1, the STA 400 quantizes the channel coefficients (eg, channel estimation components) normalized by the reference signal in an amplitude range narrower than the amplitude of the reference signal.

[0212] For example, a channel coefficient normalized by a reference signal indicates a relative amplitude with respect to the reference signal (in other words, a difference from the reference signal).

[0213] Fig. 20 shows an example of the range of relative amplitude corresponding to the channel coefficient. In Fig. 20, the expression range of the relative amplitude with respect to the reference signal is set to, for example, 0 to 1 / 4. For example, for the relative amplitude, one of four patterns of amplitude accuracy (in other words, granularity) is expressed by one of the values ​​0 to 3: 1 / 16, 2 / 16, 3 / 16, or 4 / 16.

[0214] In this way, STA400 may, for example, variably set the relative amplitude accuracy (in other words, the representation range) depending on the value of the normalized channel coefficient (e.g., relative amplitude), and quantize the normalized channel coefficient based on the set relative amplitude accuracy.

[0215] For example, the STA 400 may set a smaller value of the relative amplitude precision when the value of the relative amplitude is smaller (in other words, when the difference between the normalized channel coefficient and the reference signal is smaller). With this setting, for example, when the number of bits allocated to the normalized channel coefficient is fixed, the STA 400 can quantize the normalized channel coefficient with finer granularity when the value of the relative amplitude is smaller. In other words, the STA 400 can quantize the normalized channel coefficient with coarser granularity over a wider range when the value of the relative amplitude is larger.

[0216] For example, the STA 400 may include the relative amplitude accuracy (for example, one of the values ​​0 to 3 shown in FIG. 20) in the feedback information together with the channel coefficient and feed it back to the AP 300.

[0217] Furthermore, for example, when STA 400 feeds back components of inter-user interference signals for the same channel coefficients in multiple times, STA 400 may set the relative amplitude precision to be smaller for each feedback. By setting this relative amplitude precision, for example, the suppression effect of the steering matrix on the inter-user interference signals may be gradually corrected.

[0218] Method 2-1 allows the amplitude of the channel coefficient, which is a relative value, to be represented with high accuracy using fewer bits, thereby enabling AP 300 to improve the accuracy of steering matrix correction.

[0219] The embodiments of the present disclosure have been described above.

[0220] (Other embodiments) (1) Methods 1-1 to 1-5 and Method 2-1 may be combined in any two or more.

[0221] For example, when combining Method 1-1 and Method 1-2, the transmission signal fed back by the STA may include both the compressed beamforming / CQI frame Action field format and the Individual SS index feedback frame format in the data portion. In this case, as in Method 1-1, the STA 200 may notify the AP 100 of the index information of the spatial stream to be fed back using the Individual SS index feedback frame format, without replacing the Sounding Dialogue Token Number field with the Start SS index. This notification method allows, for example, the spatial stream index to be specified discretely (in other words, discontinuously), thereby reducing the amount of feedback.

[0222] Note that, here, as an example, the Individual SS index feedback frame formats of Method 1-1 and Method 1-2 are combined, but other frame formats for notifying spatial stream indexes may also be used.

[0223] (2) Methods 1-1 to 1-5 and Method 2-1 may be applied when a STA transmits feedback information to multiple APs in Multi-AP coordination.

[0224] (3) Methods 1-1 to 1-5 and Method 2-1 are not limited to transmission of feedback information for non-NDP PPDUs, and may also be applied to NDPs.

[0225] (4) When an AP controls multiple DL MU-MIMO transmissions, the AP may transmit a DL MU-MIMO signal (e.g., the User field of the preamble) including an identifier (e.g., an “MU-MIMO ID”) for identifying the MU-MIMO allocation pattern.

[0226] In this case, for example, the STA may obtain the MU-MIMO ID from the received DL MU-MIMO signal and transmit the feedback information including the MU-MIMO ID. This allows the AP to determine which DL MU-MIMO signal the feedback information corresponds to based on the MU-MIMO ID included in the feedback information.

[0227] (5) The STA may transmit the feedback information to the AP all at once, or may divide the feedback information into multiple transmission frames and transmit them to the AP.

[0228] (6) The STA may preferentially feed back at least one of the desired signal and the inter-user interference signal for which it has not transmitted feedback information for a certain period of time.

[0229] (7) In the first and second embodiments, the STA may determine the stream information to be fed back in accordance with conditions other than the reception quality in addition to the reception quality of the reference signal included in the non-NDP PPDU.

[0230] For example, the STA determines, for each spatial stream, a predetermined condition regarding the reception quality of the reference signal and a condition other than the reception quality, and feeds back information regarding the spatial stream that satisfies all the conditions.

[0231] The condition other than the reception quality may be, for example, a feedback interval. The feedback interval may be the number of non-NDP MU PPDU packets received since the STA last transmitted feedback. Alternatively, the feedback interval may be the time elapsed since the STA last transmitted feedback. If a predetermined feedback interval has elapsed, the STA transmits feedback. Alternatively, if the predetermined feedback interval has not elapsed, the STA decides not to transmit feedback.

[0232] The condition other than the reception quality may be, for example, the MCS of the data portion of the non-NDP PPDU. If the MCS level of the data portion obtained from the preamble portion of the non-NDP PPDU is higher than the default MCS level, the STA may increase the feedback frequency. Also, if the MCS level of the data portion obtained from the preamble portion of the non-NDP PPDU is lower than the default MCS level, the STA may decrease the feedback frequency.

[0233] The condition other than the reception quality may be, for example, the number of spatial streams assigned to the STA. If the assigned number of spatial streams is greater than the default assigned number of spatial streams, the STA may decrease the feedback frequency. Also, if the assigned number of spatial streams is less than the default assigned number of spatial streams, the STA may increase the feedback frequency.

[0234] The condition other than the reception quality may be, for example, an upper limit number of spatial streams to be transmitted in one feedback. When there are M spatial streams that satisfy a predetermined condition regarding the reception quality of the reference signal, the STA limits the spatial streams to be fed back based on the upper limit number N of spatial streams to be fed back (where M>N).

[0235] The condition other than the reception quality may be, for example, the minimum number of spatial streams required for feedback. The STA performs feedback only when there are N or more spatial streams that satisfy a predetermined condition regarding the reception quality of the reference signal. Furthermore, the STA determines not to transmit feedback when there are fewer than N spatial streams that satisfy a predetermined condition regarding the reception quality of the reference signal.

[0236] The conditions other than the reception quality may be determined based on the capability of the STA, for example. Alternatively, the AP may notify the STA of the conditions other than the reception quality by including them in an NDPA, a beacon, a management frame, or the like.

[0237] The STA may also control the threshold value of the reception quality information in accordance with conditions other than the reception quality.The STA may also control conditions other than the reception quality in accordance with the reception quality information.

[0238] (8) In the above embodiment, a configuration example based on the 11ax frame format has been described as an example. However, the format to which an embodiment of the present disclosure is applied is not limited to the 11ax format.

[0239] (9) In the above embodiment, the operation in DL communication has been described. However, an embodiment of the present disclosure is not limited to DL communication and may be applied to, for example, UL communication or sidelink.

[0240] (10) This disclosure can be realized by software, hardware, or software integrated with hardware. Each functional block described in the above embodiments may be partially or entirely realized as an LSI, which is an integrated circuit. Each process described in the above embodiments may be partially or entirely controlled by a single LSI or a combination of LSIs. An LSI may be composed of individual chips, or may be composed of a single chip that includes some or all of the functional blocks. An LSI may have data inputs and outputs. Depending on the level of integration, an LSI may be referred to as an IC, system LSI, super LSI, or ultra LSI. The integration method is not limited to LSIs; it may also be realized by dedicated circuits, general-purpose processors, or dedicated processors. Furthermore, a field programmable gate array (FPGA), which can be programmed after LSI fabrication, or a reconfigurable processor, which allows the connections and settings of circuit cells within an LSI to be reconfigured, may also be used. This disclosure may be realized as digital or analog processing. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or other derivative technologies, it is natural that such technology can be used to integrate functional blocks. The application of biotechnology is also a possibility.

[0241] The present disclosure may be implemented in any type of apparatus, device, or system (collectively referred to as a communications apparatus) that has a communications function. The communications apparatus may include a wireless transceiver and processing / control circuitry. The wireless transceiver may include a receiver and a transmitter, or both functions. The wireless transceiver (transmitter and receiver) may include a radio frequency (RF) module and one or more antennas. The RF module may include an amplifier, an RF modulator / demodulator, or the like. Non-limiting examples of communication devices include telephones (e.g., cell phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks), cameras (e.g., digital still / video cameras), digital players (e.g., digital audio / video players), wearable devices (e.g., wearable cameras, smartwatches, tracking devices), game consoles, digital book readers, telehealth / telemedicine devices, communication-enabled vehicles or mobile transportation (e.g., cars, airplanes, ships), and combinations of the above devices.

[0242] Communications equipment is not limited to portable or mobile equipment, but also includes non-portable or fixed equipment, devices, and systems of any kind, such as smart home devices (such as appliances, lighting equipment, smart meters or metering devices, control panels, etc.), vending machines, and any other "things" that may exist on an IoT (Internet of Things) network.

[0243] Communications include data communications via cellular systems, wireless LAN systems, communications satellite systems, etc., as well as data communications via combinations of these.

[0244] A communications apparatus also includes devices such as controllers and sensors connected or coupled to a communications device that performs the communications functions described in this disclosure, such as controllers and sensors that generate control and data signals used by the communications device to perform the communications functions of the communications apparatus.

[0245] The communication apparatus also includes infrastructure facilities, such as base stations, access points, and any other apparatus, device, or system that communicates with or controls the various apparatuses listed above, but are not limited to these.

[0246] A communication device according to one embodiment of the present disclosure includes a control circuit that determines a spatial stream for which second information is to be fed back based on first information regarding the reception quality of a plurality of spatial streams, and a transmission circuit that transmits the second information regarding the determined spatial stream.

[0247] In one embodiment of the present disclosure, the second information includes information about some of the spatial streams.

[0248] In one embodiment of the present disclosure, the second information is included in a compressed beamforming / CQI frame Action field format signal.

[0249] In one embodiment of the present disclosure, the second information includes information identifying a terminal assigned to the determined spatial stream.

[0250] In one embodiment of the present disclosure, the second information includes information identifying the determined spatial stream.

[0251] In one embodiment of the present disclosure, the second information is included in a response signal to the received data.

[0252] In one embodiment of the present disclosure, the transmission circuit requests a source of the plurality of spatial streams to transmit a signal that triggers transmission of the second information.

[0253] In one embodiment of the present disclosure, the transmission circuit transmits a signal notifying a source of the plurality of spatial streams of the transmission of the second information.

[0254] In one embodiment of the present disclosure, the second information includes a value obtained by normalizing some components of the channel estimates for each of the plurality of spatial streams by a reference signal.

[0255] In one embodiment of the present disclosure, the control circuit quantizes the normalized channel estimate component within an amplitude range narrower than the amplitude of the reference signal.

[0256] In a communication method according to one embodiment of the present disclosure, a communication device determines a spatial stream for which second information is to be fed back based on first information regarding the reception quality of a plurality of spatial streams, and transmits the second information regarding the determined spatial stream.

[0257] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2019-166253, filed on September 12, 2019, are incorporated herein by reference in their entirety. [Industrial Applicability]

[0258] One embodiment of the present disclosure is useful in wireless communication systems. [Explanation of symbols]

[0259] 100,300 AP 101,201 Radio receiver 102 Decoding unit 103 Scheduling Department 104,302 Steering matrix generator 105 Data Generation Unit 106 Preamble generation section 107,206 Radio transmitter 200,400 STA 202 Preamble demodulation section 203 Data Decoding Unit 204,401 Feedback judgment unit 205 Transmission signal generation unit 301,402 Reference signal holding section

Claims

1. a transmitter for transmitting a reference signal including a plurality of spatial streams; a receiving circuit for receiving second information relating to some spatial streams among the plurality of spatial streams for which channel estimation is performed using the reference signal and for which second information is fed back, the second information being determined based on first information relating to reception qualities of the plurality of spatial streams; a control circuit that performs scheduling using the second information; Equipped with The second information includes information identifying a terminal assigned to the part of spatial streams among a plurality of terminals, and relates to only the part of spatial streams among the plurality of spatial streams. Communication equipment.

2. the second information is included in a compressed beamforming frame / CQI Action field format signal; The communication device according to claim 1 .

3. the second information includes information identifying the determined portion of spatial streams. The communication device according to claim 1 .

4. the second information is included in a response signal to the received data; The communication device according to claim 1 .

5. the transmitter transmits a signal that triggers transmission of the second information. The communication device according to claim 1 .

6. the receiving circuit receives a signal notifying transmission of the second information. The communication device according to claim 1 .

7. the second information includes a value obtained by normalizing some components of the channel estimate values ​​of each of the plurality of spatial streams by a reference signal. The communication device according to claim 1 .

8. The communication device transmitting a reference signal including a plurality of spatial streams; receiving second information regarding some spatial streams among the plurality of spatial streams for which second information is fed back, the second information being determined based on first information regarding reception qualities of the plurality of spatial streams, wherein channel estimation is performed using the reference signal; performing scheduling based on the second information; The second information includes information identifying a terminal assigned to the determined portion of spatial streams among a plurality of terminals, and relates to only the portion of spatial streams among the plurality of spatial streams. Communication method.

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