Communication apparatus and communication method

Abstract

A communication device includes: a control circuit that determines a spatial stream to which second information is fed back on the basis of first information relating to reception quality of a plurality of spatial streams; and a transmission circuit that transmits second information relating to the determined spatial stream.

Description

[0001] This application is a divisional application of the Chinese invention patent application with the application date of July 17, 2020, application number 2020800603163, invention name “Communication device and communication method”, and the applicant is Panasonic Electric (USA) Intellectual Property Corporation. Technical Field

[0002] The present invention relates to a communication device and a communication method. Background Art

[0003] As the successor standard of 802.11ax (hereinafter referred to as "11ax"), the Task Group (TG) be is planning to formulate the technical specifications of 802.11be (hereinafter referred to as "11be"), which is the standard of 802.11 of the Institute of Electrical and Electronics Engineers (IEEE).

[0004] In 11be, for example, compared to 11ax, it is discussed to increase the maximum number of spatial streams (e.g., also called "number of spatial streams (SS)" or "number of spatial multiplexing") in downlink (DL) multi-user multiple-input multiple output (MU-MIMO). By increasing the maximum number of spatial streams, spectral efficiency can be improved.

[0005] Prior art literature

[0006] Non-patent literature

[0007] Non-patent document 1: IEEE 802.11-19 / 0828r3, feedback-overhead-analysis-for-16-spatial-stream-mimo, May, 2019

[0008] Non-patent document 2: IEEE P802.11ax D4.0, February 2019

[0009] Non-patent document 3: IEEE Std 802.11, 2016 Summary of the invention

[0010] However, there is still room for research on the control method of spatial multiplexing processing.

[0011] Non-limiting embodiments of the present invention help provide a base station, a terminal, and a communication method, in which the efficiency of processing related to information feedback of a communication device is improved, and the communication device receives a stream subjected to spatial multiplexing.

[0012] A communication device according to an embodiment of the present invention includes: a control circuit that determines a spatial stream for feeding back second information based on first information related to reception quality of multiple spatial streams; and a transmission circuit that transmits the second information related to the determined spatial stream.

[0013] It should be noted that these general or specific aspects may be implemented by a system, an apparatus, a method, an integrated circuit, a computer program or a recording medium, or may be implemented by any combination of systems, apparatuses, methods, integrated circuits, computer programs and recording media.

[0014] According to an embodiment of the present invention, it is possible to improve the efficiency of information feedback-related processing of a communication device that receives a spatially multiplexed stream.

[0015] More advantages and effects of an embodiment of the present invention will be explained through the description and drawings. These advantages and / or effects are provided by several embodiments, and the features described in the description and drawings, but not necessarily all of them need to be provided in order to obtain one or more of the same features. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a sequence diagram showing an example of beamforming using null data packet (NDP) sounding and explicit feedback.

[0017] Figure 2 It is a diagram showing an example of a High Efficiency (HE) Compressed Beamforming (Compressed Beamforming) / Channel Quality Indicator (CQI) frame action field format.

[0018] Figure 3 This is a sequence diagram showing an example of staggered sounding.

[0019] Figure 4 This is a block diagram showing a configuration example of a part of STA according to the first embodiment.

[0020] Figure 5This is a block diagram showing a structural example of an AP according to the first embodiment.

[0021] Figure 6 This is a block diagram showing a structural example of STA according to implementation mode 1.

[0022] Figure 7 This is a sequence diagram showing an operation example of the wireless communication system according to the first embodiment.

[0023] Figure 8 This is a flowchart showing an example of the operation of determining feedback information according to the first embodiment.

[0024] Fig. 9 This is a diagram showing an example of a system configuration according to the first embodiment.

[0025] Fig.10 This is a diagram showing an example of the HE Compressed Beamforming / CQI frame behavior field format of method 1-1.

[0026] Fig.11 This is a diagram showing an example of the HE behavior field of method 1-2.

[0027] Fig.12 This is a diagram showing an example of a frame format of method 1-2.

[0028] Fig.13 This is a diagram showing an example of the BA (Block Aacknowledgement) frame format and the response signal transmission operation of method 1-3.

[0029] Fig.14 This is a diagram showing an example of the BA frame format and the response signal transmission operation of method 1-3.

[0030] Fig.15 This is a sequence diagram showing an example of the operation of methods 1 to 4.

[0031] Fig.16 This is a sequence diagram showing an example of the operation of method 1-5.

[0032] Fig.17 This is a block diagram showing a structural example of an AP according to the second embodiment.

[0033] Fig.18 This is a block diagram showing a structural example of STA according to implementation mode 2.

[0034] Fig.19 This is a diagram showing an example of a system configuration according to the second embodiment.

[0035] Fig. 20 This is a diagram showing an example of relative amplitude accuracy in the second embodiment.

[0036] Description of Reference Numerals

[0037] 100, 300AP; 101, 201 wireless receiving unit; 102 decoding unit; 103 scheduling unit; 104, 302 steering matrix generating unit; 105 data generating unit; 106 preamble generating unit; 107, 206 wireless transmitting unit; 200, 400STA; 202 preamble demodulating unit; 203 data decoding unit; 204, 401 feedback determination unit; 205 transmitting signal generating unit; 301, 402 reference signal retaining unit. DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0039] 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 can be referred to as a "spatial stream", and a spatially multiplexed modulation symbol stream can be referred to as a "space-time stream (or, also called "Space-time stream (STS)")" to distinguish them. For example, when space-time block coding is not performed, the number of space-time streams is equal to the number of spatial streams.

[0040] In the following description, an example in which space-time block coding is not performed is described. In other words, in the following description, the spatial stream and the space-time stream are not distinguished, and the spatial channel used for spatial multiplexing is described as "spatial stream". However, the spatial stream in the following description can also be understood as the space-time stream in the case of space-time block coding.

[0041] [Beamforming]

[0042] In DL MU-MIMO, beamforming technology is used. The beamforming technology can be used to improve the communication quality in DL.

[0043] In beamforming of DL MU-MIMO, for example, weighting (also referred to as "steering", "spatial mapping" or "transmit precoding") is performed to add orthogonality to the signals sent to each user, and the weighting controls the amplitude and phase. For example, a matrix representing the weighting (hereinafter referred to as a "steering matrix") can be derived based on information on the transmission path (also referred to as a "channel") estimated by beamforming.

[0044] The amount of transmission path information in DL MU-MIMO increases in proportion to the maximum number of spatial streams, for example. Therefore, in 11be where the maximum number of spatial streams can be increased, methods for improving the efficiency of beamforming are studied (for example, refer to non-patent document 1).

[0045] As an example of a beamforming method, 11ax supports a method using NDP sounding (or, also called "NDP feedback sequence") and explicit feedback (for example, refer to non-patent document 2). Figure 1 is a sequence diagram showing an example of beamforming using NDP sounding and explicit feedback.

[0046] exist Figure 1 In the present invention, an access point (AP), or a base station, for example, sends an NDP announcement (NDPA) to each terminal (also called a STA (Station)). By sending the NDPA, the AP notifies the STA of the sending of the NDP.

[0047] Following the sending of the NDPA, the AP sends the NDP to the STA.

[0048] 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.

[0049] In addition, for example, when a steering matrix is ​​attached to a non-legacy LTF, the STA can estimate the channel (for example, also referred to as an "effective channel") including the steering matrix, regardless of whether the received signal is NDP or non-NDP. In the following description, whether it is a channel or an effective channel, it is simply referred to as a "transmission path response (also referred to as "transmission path characteristics", "channel response", "channel estimation matrix" or "channel matrix")". For example, based on the channel estimation value, the STA responds to the NDP and decides the feedback information to send to the AP.

[0050] Figure 2 An example of the structure of feedback information sent by STA to AP. As an example, Figure 2 An example structure showing the compressed beamforming / CQI frame behavior field format.

[0051] exist Figure 2 The “HE MIMO Control” shown in FIG. 1 may include, for example, a feedback control signal. Figure 2The "HE Compressed Beamforming Report" shown in FIG. 1 may include, for example, the reception quality of each spatial stream (e.g., average signal-to-noise ratio (SNR)) or a feedback matrix in which the amount of information is compressed by a predetermined method. Figure 2 The “HE MU Exclusive Beamforming Report” shown may include information such as the difference between the SNR of each subcarrier and the average SNR of the spatial stream to which each subcarrier belongs.

[0052] In the following description, as an example, Figure 2 The feedback control signal, feedback matrix, SNR related to spatial streams and subcarriers and other information contained in the HE compressed beamforming / CQI frame behavior field format shown (for example, equivalent to the second information) is called "feedback information (or, also called feedback signal)".

[0053] For example, in the AP, STS When an NDP of spatial streams is sent to a STA, the STA can estimate the size to be N RX ×N STS In addition, N RX In this case, the size of the feedback matrix (N) included in the feedback information by the STA r ×N c ) can be calculated, for example, according to the following formula (1).

[0054] N r =N STS , N c =min(N STS , N RX ) (1)

[0055] The AP may, for example, schedule the STA based on the feedback information sent from the STA. In scheduling, the AP may, for example, determine resource allocation information or transmission parameters of the destination STA or each STA.

[0056] In addition, for example, in the case of multi-user transmission (e.g., also known as "MU-MIMO transmission"), the AP can derive a steering matrix based on feedback information received from multiple STAs. The AP can, for example, use the steering matrix to send downlink (DL) data (e.g., called a "downlink multi-user physical layer convergence procedure protocol data unit (DL MU physicallayer convergence procedure protocol data unit, DL MU PPDU)") to the STA.

[0057] In addition, as an example of another beamforming method, 802.11n supports “interleaved sounding” (for example, refer to Non-Patent Document 3).

[0058] Figure 3 This is a sequence diagram showing an example of the operation of interleaving detection.

[0059] Staggered sounding is a beamforming method for single-user MIMO (SU-MIMO). The AP, for example, sends a signal (e.g., SU PPDU) containing a data portion (e.g., also referred to as a "data field") to the STA. The STA, for example, determines whether to send feedback information based on the channel state information (CSI) / steering request (Steering Request) contained in the medium access control (MAC) layer of the signal sent from the AP. For example, when the STA is instructed to send feedback information (in the case of sending feedback information: "yes"), it will feed back a channel estimation value obtained based on a signal (e.g., non-legacy LTF) contained in the signal sent from the AP. For example, the STA can add a 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 indicated by the CSI / steering request, and send it to the AP.

[0060] However, for example, if NDP sounding and explicit feedback are used for beamforming for each STA every time the AP calculates (in other words, updates) the steering matrix, the overhead of the feedback information will increase and the transmission efficiency will decrease.

[0061] In addition, the AP may not be able to properly determine when to update the steering matrix. For example, when the change in the transmission path response (e.g., also known as "channel fading") is small (e.g., when the change in the transmission path response is less than a threshold), the steering matrix may not be updated. As a result, when the change in the transmission path response is less than a threshold, when beamforming is performed using NDP sounding and explicit feedback, feedback information is sent unnecessarily, and transmission efficiency is reduced.

[0062] In one embodiment of the present invention, a method for improving transmission efficiency in spatial multiplexing transmission such as MU-MIMO transmission is described. For example, a method for improving the efficiency of information feedback-related processing in a communication device that receives a spatially multiplexed stream is described.

[0063] (Implementation Method 1)

[0064] [Structure of wireless communication system]

[0065] A wireless communication system according to an embodiment of the present invention includes at least one AP 100 and a plurality of STAs 200 .

[0066] For example, in DL communication (e.g., transmission and reception of DL data), AP100 (or, also referred to as "downlink wireless transmission device") can perform DL MU-MIMO transmission to multiple STA200 (or, also referred to as "downlink wireless reception device"). Each STA200 can, for example, generate feedback information based on the signal transmitted by DL MU-MIMO (e.g., also referred to as "DL MU PPDU") and send the feedback information to AP100 (e.g., perform uplink (UL) SU transmission or UL MU transmission).

[0067] Figure 4 FIG. 1 is a block diagram showing a configuration example of a part of STA 200 according to an embodiment of the present invention. Figure 4 In the STA 200 (e.g., corresponding to a communication device), a feedback determination unit 204 (e.g., corresponding to a control circuit) determines a spatial stream for feeding back second information (e.g., stream information) based on first information related to reception quality of a plurality of spatial streams. A wireless transmission unit 206 (e.g., corresponding to a transmission circuit) transmits the second information related to the determined spatial stream.

[0068] <AP100 structure example>

[0069] Figure 5 It is a block diagram showing a configuration example of AP100. Figure 5The AP 100 shown includes, for example, a wireless receiving unit 101 , a decoding unit 102 , a scheduling unit 103 , a steering matrix generating unit 104 , a data generating unit 105 , a preamble generating unit 106 , and a wireless transmitting unit 107 .

[0070] The wireless receiving unit 101 receives the signal transmitted from the STA 200 via the antenna, and performs wireless receiving processing such as down-conversion and A / D (Analog / Digital) conversion on the received signal. For example, the wireless receiving unit 101 divides the received signal after the wireless receiving processing into, for example, a preamble part (also referred to as a "preamble signal") and a data part (also referred to as a "data signal"), and outputs it to the decoding unit 102.

[0071] The decoding unit 102 performs processing such as Fast Fourier Transform (FFT) on the preamble signal and the data signal input from the wireless receiving unit 101 .

[0072] The decoding unit 102, for example, extracts a control signal (e.g., frequency bandwidth, modulation and channel coding scheme (MCS), or coding method) contained in the preamble signal. In addition, the decoding unit 102, for example, uses a reference signal contained in the preamble signal to perform channel estimation. For example, the decoding unit 102 can generate a channel estimate matrix based on the channel estimation result. The channel estimate matrix can be, for example, a matrix composed of N corresponding to the number of streams. ss and N corresponding to the number of receiving antennas of AP100 RX Indicated by (N RX ×N ss ) is represented by a matrix.

[0073] The decoding unit 102 performs channel equalization, demodulation, decoding, and error determination such as cyclic redundancy check (CRC) on the data signal after FFT, based on the control signal and channel estimation matrix extracted from the preamble signal, for example. If the data signal has no error (in other words, no decoding error), the decoding unit 102 outputs the decoded data signal to the scheduling unit 103 and the steering matrix generation unit 104, for example. If the data signal has an error, the decoding unit 102 does not output the decoded data signal, for example.

[0074] The scheduling unit 103 performs scheduling for STA200 (in other words, in DL) based on the data signal (for example, including a response signal or feedback information) input from the decoding unit 102. For example, the scheduling unit 103 can decide whether to perform MU-MIMO transmission. In the case of MU-MIMO transmission, the scheduling unit 103 can determine the allocation of RU (Resource Unit) to each STA200 (for example, user) based on the data signal input from the decoding unit 102, and can also determine the allocation of spatial streams to each STA200. The scheduling unit 103 outputs the determined scheduling-related information to the steering matrix generation unit 104, the data generation unit 105, and the preamble code generation unit 106.

[0075] The steering matrix generation unit 104 generates a steering matrix based on the information related to scheduling input from the scheduling unit 103. The steering matrix is, for example, a matrix that gives orthogonality to MU-MIMO signals.

[0076] In addition, when a data signal containing feedback information (for example, a channel estimation value or a singular vector) is input from the decoding unit 102, the steering matrix generating unit 104 may newly generate a steering matrix based on the feedback information, or may update a portion of the reserved steering matrix. In addition, when a data signal containing feedback information is not input from the decoding unit 102, the steering matrix generating unit 104 may generate a steering matrix based on the feedback information reserved for the destination STA 200 (in other words, the user). In addition, when the feedback information of the destination STA 200 is not reserved, the steering matrix generating unit 104 may, for example, set a predetermined orthogonal matrix (for example, a unit matrix or a Hadamard matrix) as the steering matrix.

[0077] The steering matrix generator 104 outputs information related to the steering matrix used for MU-MIMO transmission to the data generator 105 and the preamble generator 106. In addition, the steering matrix generator 104 stores information related to the steering matrix (eg, feedback information) in a buffer (not shown).

[0078] The data generation unit 105 generates a data sequence to be sent to STA200 based on the scheduling information input from the scheduling unit 103. In addition, the data generation unit 105 encodes the generated data sequence based on the scheduling information. In addition, the data generation unit 105 can add information related to the steering matrix input from the steering matrix generation unit 104 to the encoded data sequence. The data generation unit 105, for example, allocates the data sequence (for example, a sequence with information related to the steering matrix added) to the scheduled RU, and performs modulation and inverse Fourier transform (Inverse Fast Fourier Transform (IFFT)) processing to generate a data signal. The data generation unit 105 outputs the generated data signal to the wireless transmission unit 107.

[0079] The preamble generator 106 generates a preamble signal based on the scheduling information input from the scheduler 103. For example, the preamble generator 106 may add the steering matrix input from the steering matrix generator 104 to the reference signal included in the preamble signal. The preamble generator 106 modulates and performs IFFT processing on the preamble signal, and outputs the preamble signal to the wireless transmitter 107.

[0080] The wireless transmission unit 107 generates a wireless frame (in other words, 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 (Digital / Analog) conversion and up-conversion to a carrier frequency on the generated wireless frame, and transmits the signal after the wireless transmission processing to the STA 200 via the antenna.

[0081] <Configuration example of STA200>

[0082] Figure 6 It is a block diagram showing a configuration example of the STA 200 . Figure 6 The STA 200 shown 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 .

[0083] The wireless receiving unit 201 performs wireless receiving processing such as down-conversion and A / D conversion on the signal received via the antenna. The wireless receiving unit 201 extracts the preamble signal from the signal after the wireless receiving processing and outputs it to the preamble demodulation unit 202. In addition, the wireless receiving unit 201 extracts the data signal from the signal after the wireless receiving processing and outputs it to the data decoding unit 203.

[0084] The preamble demodulation unit 202 performs demodulation processing such as FFT on the preamble signal input from the wireless receiving unit 201, and extracts a control signal, such as a control signal used for demodulation and decoding of the data signal, from the demodulated preamble signal. In addition, the preamble demodulation unit 202 can perform channel estimation based on the reference signal contained in the preamble signal. The preamble demodulation unit 202 outputs the extracted control signal and channel estimation information (for example, a channel estimation matrix) to the data decoding unit 203. In addition, the preamble demodulation unit 202 outputs the reference signal and channel estimation information contained in the preamble signal to the feedback determination unit 204.

[0085] The data decoding unit 203 performs FFT processing, channel equalization, or demodulation on the data unit input from the wireless receiving unit 201, based on the control signal and channel estimation information input from the preamble demodulation unit 202, and extracts the demodulated data sent to the STA 200. In addition, the data decoding unit 203 decodes the extracted demodulated data and performs error determination such as CRC. The data decoding unit 203 outputs the error result of the data signal to the feedback determination unit 204.

[0086] The feedback determination unit 204 determines whether to feed back information related to the spatial stream (e.g., stream information). In other words, the feedback determination unit 204 determines the spatial stream to which the stream information is fed back, for example, among a plurality of spatial streams in multi-user transmission. In addition, the "determination unit" may be replaced with other terms such as "determination unit" or "control unit".

[0087] For example, the feedback determination unit 204 generates reception quality information based on the error determination result of the data signal input from the data decoding unit 203 and the reference signal included in the preamble input from the preamble demodulation unit 202 .

[0088] The reception quality information may include, for example, the error determination result of the expected (or desired) signal (for example, a signal with STA200 as the destination), the signal to interference plus noise ratio (SINR) of the expected signal, the power value of the inter-user interference signal (for example, a signal with other STAs different from STA200 as the destination), the desired signal to undesired signal ratio (DUR) between the expected signal and the inter-user interference signal, the change in the expected signal power between the last MU-MIMO signal and the current MU-MIMO signal or the change in the inter-user interference signal power, the change in the expected signal power detected by NDP and the expected signal power between the MU-MIMO signal, or the change in the inter-user interference signal power, and the like.

[0089] Next, the feedback determination unit 204 determines whether the reception quality based on the reference signal satisfies a predetermined threshold (in other words, a condition), for example.

[0090] When the reception quality satisfies a predetermined threshold, the feedback determination unit 204, for example, decides to feed back (in other words, transmit) the stream information. On the other hand, when the reception quality does not satisfy a predetermined threshold, the feedback determination unit 204, for example, may decide not to transmit the stream information. The feedback determination unit 204, for example, may decide whether to feed back the stream information for each of a plurality of spatial streams in multi-user transmission.

[0091] The feedback determination unit 204 generates feedback information including stream information related to the determined spatial stream, and outputs it to the transmission signal generation unit 205. The stream information may include, for example, information for identifying the destination STA 200 of the spatial stream whose reception quality satisfies a predetermined threshold (e.g., STA-ID), information for identifying the spatial stream (e.g., index information of the spatial stream), SNR of the spatial stream, feedback matrix, and the like.

[0092] When feedback information is not input from the feedback determination unit 204, the transmission signal generation unit 205 generates, for example, a data sequence including a response signal for the AP 100. On the other hand, when feedback information is input from the feedback determination unit 204, the transmission signal generation unit 205 may generate a data sequence including a response signal for the AP 100 and feedback information. The transmission signal generation unit 205 allocates the generated data sequence to a predetermined frequency resource and performs modulation and IFFT processing to generate a data signal (for example, a transmission signal). In addition, the transmission signal generation unit 205 adds a preamble to the data signal to generate a wireless frame (packet signal), and outputs it to the wireless transmission unit 206.

[0093] The wireless transmission 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 generation unit 205 , and transmits the signal after the wireless transmission processing to the AP 100 via the antenna.

[0094] [AP and STA operation example]

[0095] Next, an operation example of the AP 100 and the STA 200 according to the present embodiment will be described.

[0096] In this embodiment, in multi-user transmission, STA200 feeds back to AP100 the stream information corresponding to a part of the spatial stream in the spatial stream of the data part contained in the non-NDP MU PPDU based on the reception quality information of the reference signal (e.g., LTF) contained in the non-NDP MU PPDU (e.g., the MU PPDU containing the data part described later).

[0097] As an example, the following method is described, that is, in 11ax multi-user transmission (for example, DL MU-MIMO transmission), STA200 generates feedback information based on part of the stream information for the non-NDP MU PPDU sent by AP100, and provides feedback.

[0098] Figure 7 This is a sequence diagram showing an operation example of a wireless communication system related to DL MU-MIMO transmission.

[0099] As an example, Figure 7 An operation example of DL MU-MIMO transmission in the AP 100 and two STAs 200 (for example, STA1 and STA2) is shown. In addition, the number of STAs subjected to spatial multiplexing in DL MU-MIMO transmission is not limited to two, and may be three or more.

[0100] exist Figure 7 In the example, AP100 transmits NDPA to STA1 and STA2 (ST101). By transmitting NDPA, AP100 notifies STA1 and STA2 that NDP will be transmitted after the transmission of NDPA.

[0101] STA1 and STA2, for example, perform reception processing of NDPA (ST102-1 and ST102-2). For example, STA1 and STA2 may obtain the following control signal based on NDPA, which is used to compress and feedback the transmission path information derived based on the NDP sent by AP100. The control signal may include, for example, information related to feedback such as bandwidth, frequency resource (e.g., also referred to as "resource unit (RU)") index, feedback type, number of subcarrier groups, or codebook size.

[0102] AP100 transmits NDP to STA1 and STA2, for example (ST103). For NDP, for example, DL MU transmission may be performed. DL MU transmission may be, for example, DL MU-MIMO transmission or DL ​​Orthogonal Frequency-Division Multiple Access (OFDMA) transmission.

[0103] STA1 and STA2 perform, for example, NDP reception processing (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.

[0104] STA1 and STA2, for example, generate feedback information (ST105-1 and ST105-2). STA1 and STA2, for example, may generate feedback information including information such as a feedback matrix or an average SNR of each spatial stream based on the control signal obtained from the NDPA. The feedback matrix may, for example, include a channel estimation value for each spatial stream, or a singular vector obtained by applying singular value decomposition (SVD) to the channel estimation value.

[0105] For example, AP100 sends a trigger frame to STA1 and STA2 (ST106). For example, AP100 can use the trigger frame of NDP feedback report polling (Feedback Report Poll) to notify STA1 and STA2 of the control signal and transmission timing for UL MU transmission of feedback information. The control signal may include information related to the transmission of feedback information, such as bandwidth, transmission power, allocated RU, MCS, or allocated spatial stream.

[0106] STA1 and STA2 perform, for example, a trigger frame reception process (ST107-1 and ST107-2). STA1 and STA2 receive the trigger frame to obtain, for example, a control signal for UL MU-MIMO transmission for feedback information.

[0107] STA1 and STA2 transmit feedback information to AP100 based on the timing indicated by the trigger frame, for example (ST108-1 and ST108-2). For example, the feedback information may be transmitted by UL MU-MIMO.

[0108] AP 100 receives signals (eg, UL MU-MIMO signals) transmitted from STA 1 and STA 2 and obtains feedback information ( ST109 ).

[0109] AP100, for example, schedules STA1 and STA2 based on the feedback information (ST110). For example, when performing DL MU-MIMO transmission to STA1 and STA2, AP100 can generate a steering matrix based on the feedback information. In addition, AP100 can also perform zero-point control on the steering matrix to reduce interference between each feedback information.

[0110] AP100 transmits a DL MU-MIMO signal (e.g., DL MU PPDU) to STA1 and STA2 (ST111). For example, AP100 may attach a steering matrix to the DL MU MIMO signal (e.g., a reference signal and a data portion included in the preamble portion) and transmit the signal. In addition, AP100, for example, retains the generated steering matrix in a buffer (not shown).

[0111] STA1 and STA2 perform reception processing of DL MU-MIMO signals (ST112-1 and ST112-2). For example, STA1 and STA2 perform channel estimation based on the reference signal contained in the preamble part of the DL MU-MIMO signal, and extract the signal sent to each STA200. In addition, STA1 and STA2 can measure the reception quality of the reference signal sent to themselves (for example, called "expected signal") and the reference signal sent to other STAs that are spatially multiplexed in the RU like themselves (for example, called "inter-user interference signal") based on the reference signal contained in the preamble part of the DL MU-MIMO signal.

[0112] The reception quality may be, for example, an error determination result of an expected signal (in other words, a decoding error determination result), the SINR of an expected signal, a power value of an inter-user interference signal, the DUR between an expected signal and an inter-user interference signal, or a change in the expected signal power (or, the inter-user interference signal power) between a previous MU-MIMO signal and this MU-MIMO signal.

[0113] STA1 and STA2, for example, determine (in other words, perform feedback determination) whether to transmit feedback information related to each stream based on the measured reception quality (ST113-1 and ST113-2).

[0114] Figure 8 FIG. 1 is a flowchart showing an example of feedback determination based on reception quality. Figure 8 As an example, the information related to the reception quality (e.g., equivalent to the first information) includes the error determination result of the expected signal, the SINR of the expected signal, DUR, the inter-user interference signal power Pi, the change amount ΔPd of the expected signal power, and the change amount ΔPi of the inter-user interference signal power. In addition, Figure 8 In the example, the thresholds corresponding to the reception qualities may be different values ​​from each other.

[0115] exist Figure 8 In the embodiment, the input of the feedback determination process in STA200 may include, for example, the expected signal for STA200 (STA1 or STA2) and the inter-user interference signal (ST201).

[0116] For example, STA200 determines whether the expected signal includes a decoding error (ST202). If the expected signal does not include a decoding error (ST202: NO), STA200 determines whether the SINR of the expected signal is less than a threshold value (ST203).

[0117] When the SINR of the expected signal is greater than or equal to the threshold (ST203: No), STA200 does not output feedback information (ST204). In other words, when receiving an expected signal without decoding errors and with an SINR greater than or equal to the threshold, STA200 decides not to send feedback information.

[0118] On the other hand, when the expected signal contains a decoding error (ST202: YES), or when the SINR of the expected signal is less than the threshold (ST203: YES), STA200 determines whether DUR is less than the threshold (ST205). When DUR is less than the threshold (ST205: YES), STA200 outputs feedback information of the inter-user interference signal (ST206). In other words, when DUR is less than the threshold, it is decided to send feedback information of the inter-user interference signal that interferes more with the expected signal.

[0119] When DUR is greater than the threshold (ST205: No), STA200 determines whether the inter-user interference signal power Pi is greater than the threshold (ST207). When the inter-user interference signal power Pi is greater than the threshold (ST207: Yes), STA200 outputs feedback information of the inter-user interference signal (ST208).

[0120] When the inter-user interference signal power Pi is below the threshold (ST207: No), STA200 determines whether the change amount ΔPd of the expected signal power is greater than the threshold (ST209). When the change amount ΔPd of the expected signal power is greater than the threshold (ST209: Yes), STA200 outputs feedback information of the expected signal (ST210).

[0121] When the change amount ΔPd of the expected signal power is less than the threshold value (ST209: No), STA200 determines whether the change amount ΔPi of the inter-user interference signal power is greater than the threshold value (ST211). When the change amount ΔPi of the inter-user interference signal power is greater than the threshold value (ST211: Yes), STA200 outputs feedback information of the inter-user interference signal (ST212). On the other hand, when the change amount ΔPi of the inter-user interference signal power is less than the threshold value (ST211: No), STA200 does not output anything.

[0122] like Figure 8As shown, for example, when the ratio of the expected signal to the inter-user interference signal (e.g., DUR) is less than a threshold, or when the inter-user interference signal power or the change in the inter-user interference signal power is greater than a threshold, STA200 determines to feedback the stream information related to the inter-user interference signal. In addition, for example, when the change in the expected signal power is greater than a threshold, STA200 determines to feedback the stream information related to the expected signal.

[0123] The above describes an operation example of judging (or determining) information to be fed back based on reception quality.

[0124] In this way, STA200 (for example, STA1 and STA2) determines the feedback of stream information based on information related to the reception quality of the expected signal and the inter-user interference signal. The stream information may include information such as STA-ID or spatial stream index that notifies the destination STA of the spatial stream, or information indicating the estimation result such as feedback matrix and SNR. For example, in the case where the expected signal and the inter-user interference signal include multiple spatial streams, STA200 may perform the above-mentioned feedback determination (in other words, check the conditions for the reception quality) for each spatial stream. Through the feedback determination, STA200 determines the spatial stream to which the stream information is to be fed back among the multiple spatial streams.

[0125] In addition, Figure 7 As an example, assume a case where STA1 has stream information to be fed back (feedback: yes), and STA2 does not have stream information to be fed back (feedback: no).

[0126] exist Figure 7 STA1 and STA2 transmit response signals (eg, block ACK) to the DL MU-MIMO signal (ST114-1 and ST114-2). In addition, STA1 that transmits feedback information, for example, newly acquires carrier sense and transmits the feedback information to AP100 (ST115-1).

[0127] In addition, for example, Figure 8 As shown, the stream information included in the feedback information may be information related to the expected signal or information related to the inter-user interference signal. Alternatively, the stream information may also be information about a combination of the expected signal and the inter-user interference signal. In addition, the stream information included in the feedback information may be, for example, information related to all spatial streams whose reception quality meets a predetermined threshold, or information related to a portion of the spatial streams among the spatial streams whose reception quality meets a predetermined threshold.

[0128] AP100 receives and processes the feedback information sent from STA1 (ST116). For example, AP100 determines, based on the STA-ID or spatial stream index information included in the feedback information, to which STA the fed-back stream information is related to the spatial stream.

[0129] AP100 performs scheduling processing (ST117). For example, AP100 may update the retained steering matrix based on the feedback information newly obtained from STA1 and save it in the buffer. In addition, AP100 may also change (e.g., update) the scheduling (e.g., RU allocation or user allocation) of DL MU-MIMO transmission based on the feedback information.

[0130] For example, the AP 100 transmits a DL MU-MIMO signal (including a DL MU PPDU, for example) to STA1 and STA2 based on the updated steering matrix ( ST118 ).

[0131] An operation example of the wireless communication system related to DL MU-MIMO transmission has been described above.

[0132] For example, imagine the following situation, that is, if Fig. 9 As shown, one AP 100 having four transmitting antennas transmits a MUPPDU to which one spatial stream (SS) is allocated to each of four STAs 200 (eg, STA1 to STA4) having one receiving antenna.

[0133] Each of STA1 to STA4 performs channel estimation based on the reference signal included in the received MU PPDU, and determines whether the reference signal satisfies a condition related to reception quality (for example, reference signal 1). Figure 8 ).

[0134] Here, the reference signal used for channel estimation includes an expected signal sent to each STA200 and three inter-user interference signals sent to other STA200. For example, for a certain STA200, when the conditions related to the reception quality of the reference signals corresponding to an expected signal and an inter-user interference signal are met, STA200 sends the following feedback information to AP100, and the feedback information includes stream information related to the two spatial streams corresponding to the two signals. In other words, STA200 does not feed back the stream information related to the spatial streams corresponding to the other two signals that do not meet the reception quality conditions. In this case, for example, according to formula (1), the size of the feedback information (e.g., feedback matrix) sent by STA200 is 2×1 (e.g., N in formula (1) r =2,N c =1).

[0135] Here, assuming that Fig. 9 In the case where the STA receives the NDP sent in the above-mentioned NDP detection under the same conditions as the MU PPDU, according to formula (1), the size of the feedback information (e.g., feedback matrix) sent by the STA is 4×1. Therefore, in this embodiment, the feedback amount can be reduced.

[0136] Fig. 9 STA1 to STA4 shown can each determine the spatial stream for sending feedback information through the above actions. For example, STA1 to STA4 can each send feedback information for all four spatial streams, or can send feedback information for a portion of the spatial streams. In addition, for example, STA1 to STA4 can each not send feedback information for all spatial streams.

[0137] In other words, STA1 to STA4 may feed back part of the stream information corresponding to each of the plurality of spatial streams in the data portion included in the non-NDP MU PPDU, based on the reception quality of the reference signal included in the non-NDP MU PPDU, for example, during multi-user transmission.

[0138] Through this feedback, STA1 to STA4 can each determine the feedback of the stream information corresponding to the spatial stream that satisfies the condition related to the reception quality, and decide not to send the stream information corresponding to the spatial stream that does not satisfy the condition related to the reception quality. As a result, the overhead of the feedback information sent from each STA 200 can be reduced. In addition, for example, the frequency of beamforming processing using NDP sounding can be reduced.

[0139] In addition, STA1 to STA4 can feed back stream information at a timing that satisfies conditions related to reception quality, in other words, at an appropriate timing when AP 100 updates the steering matrix. In other words, STA1 to STA4 can autonomously determine the timing to feed back stream information based on reception quality.

[0140] In addition, Fig. 9 In the example shown, the example in which STA200 sends a feedback matrix related to a desired signal and an inter-user interference signal is described, but the feedback information is not limited to these signals (in other words, a combination of signals). Fig. 9 In the embodiment, STA 200 may also send feedback matrices related to two inter-user interference signals having large signal levels (eg, received powers) among the three inter-user interference signals without including the expected signal.

[0141] Next, methods 1-1 to 1-5 will be described as examples of methods for feeding back stream information in the STA 200 .

[0142] [Method 1-1]

[0143] In method 1-1, STA 200 includes the stream information in a signal in a compressed beamforming / CQI frame row field format and feeds back the signal to AP 100 .

[0144] Fig.10 An example of the compressed beamforming / CQI frame behavior field format when the stream information is fed back in method 1-1 is shown.

[0145] In method 1-1, if Fig.10 As shown, STA200 includes the front-end index (for example, called "front-end spatial stream index (Start SS index)") in the index of the spatial stream corresponding to the fed-back stream information in the Sounding Dialog Token Number field of the HE MIMO Control field.

[0146] In other words, the AP 100 and the STA 200 replace the HE MIMO control sounding session token number field with the front-end spatial stream index field.

[0147] For example, STA200 can use the front-end spatial stream index to c The AP 100 is notified of the spatial stream index information of the feedback information (eg, feedback matrix) related to the spatial streams. For example, the STA 200 may correspond to the spatial stream index from the front spatial stream index to (front spatial stream index + N c -1) to N c The feedback matrix of each spatial stream is included in the feedback information and transmitted. In addition, the feedback information may include, for example, a feedback matrix for each tone.

[0148] For example, Fig.10 As shown, corresponding to N c The feedback information of each spatial stream may be included in at least one of a HE Compressed Beamforming Report field and a HE MU Exclusive Beamforming Report field.

[0149] For example, in 11ax, STA feedback and spatial stream index are 1 to N in the front end. c N c In contrast, in method 1-1, STA200 feedbacks the spatial stream index as the front-end spatial stream index to (front-end spatial stream index + N c-1) to N c In other words, in method 1-1, STA 200 can decide not to send information related to spatial streams with spatial stream indexes ranging from front-end 1 to (front-end spatial stream index-1).

[0150] Therefore, according to method 1-1, for example, the feedback amount in the HE compressed beamforming report field or the HE MU exclusive beamforming report field can be reduced.

[0151] In addition, Fig.10 The detection dialogue token number field shown in FIG. 1 may contain, for example, the following value, which is a copy of the value of the detection dialogue token contained in the NDPA. In method 1-1, for example, Figure 7 As shown in (e.g., processing of ST111), STA200 makes feedback determination based on the reception quality of the reference signal included in the MU-MIMO signal, and therefore, does not send NDPA. Thus, for example, by replacing the sounding conversation token number field with the front-end spatial stream index field, STA200 can include the stream information in the compressed beamforming / CQI frame behavior field format and provide feedback.

[0152] In addition, the area (e.g., field) to which the front-end spatial stream index is allocated is not limited to the detection session token number field, and may be other areas, part or all of which are not used during feedback determination processing.

[0153] [Method 1-2]

[0154] In method 1-2, STA 200 feeds back information determining the destination STA of the spatial stream to AP 100. In other words, in method 1-2, STA 200 does not feed back feedback information such as feedback matrix or SNR to AP 100.

[0155] The "information for determining the destination STA of the spatial stream" may include, for example, the "STA-ID" corresponding to the STA 200 assigned to the spatial stream for which the feedback stream information has been determined, or the "spatial stream index (SS index)" corresponding to the spatial stream for which the feedback stream information has been determined.

[0156] In addition, when STA200 feeds back information that determines the destination STA of the spatial stream, for example, Fig.11 As shown, a frame format corresponding to the value of the "HE action field" can be applied.

[0157] For example, when the value of the HE behavior field is 0, STA 200 may apply Figure 2HE Compressed Beamforming / CQI frame behavior field format shown. In addition, for example, when the value of the HE behavior field is any one of 3 to 6, STA 200 may apply the following frame format, which is a frame format for feeding back information on the destination STA that determines the spatial stream.

[0158] Fig.12 (a)~ Fig.12 (d) shows examples of frame formats applied in each case where the value of the HE behavior field is 3 to 6.

[0159] Fig.12 (a) shows an example of the frame format "STA-ID feedback frame format (feedback frame format)" when the information identifying the destination STA of the spatial stream includes the STA-ID (for example, when the value of the HE behavior field is 3).

[0160] exist Fig.12 In the frame format shown in (a) of FIG. 1 , for example, the STA-ID of the STA assigned to the spatial stream for which the stream information feedback is determined by STA 200 is included. For example, in the case of feeding back the stream information related to one or more spatial streams assigned to a single STA, STA 200 may include the STA-ID of the corresponding STA in Fig.12 The STA-ID field shown in (a) is fed back (in other words, notified) to AP100.

[0161] Fig.12 (b) shows an example of a frame format "Continuous SS index feedback frame format" when the information for determining the destination STA of the spatial stream includes a spatial stream index (SSindex) (for example, when the value of the HE behavior field is 4).

[0162] exist Fig.12 In the frame format shown in (b), for example, a "Start SS index" indicating a front spatial stream index and an "End SS index" indicating an end spatial stream index in the spatial stream for which the stream information is fed back by STA200 are determined. For example, when the stream information related to multiple spatial streams allocated to multiple STAs is fed back, STA200 may include the front and end indexes of the corresponding spatial stream index (SS index) in the respective Fig.12 The front spatial stream index field and the end spatial stream index field shown in (b) are fed back to AP100.

[0163] In addition, the continuous stream information notified by the continuous spatial stream index feedback frame format may specify a plurality of spatial streams for a plurality of STAs 200 , or may specify a plurality of spatial streams allocated to one STA 200 .

[0164] In addition, Fig.12 In (b), for example, a field indicating the number of spatial streams (for example, N described later) may be set. ss field) instead of the “End SS index field” indicating the end spatial stream index.

[0165] Fig.12 (c) indicates that the information for determining the destination STA of the spatial stream includes N ss An example of the frame format "Individual SS index feedback frame format" when there are 5 spatial stream indices (SSindex) (for example, when the value of the HE behavior field is 5).

[0166] exist Fig.12 In the frame format shown in (c), for example, "N" indicating the number of spatial streams for which the STA 200 determines the feedback of the stream information is included. ss ", and N ss The spatial stream indexes "spatial stream index 1" to "spatial stream index N" ss ”.

[0167] N is notified by the independent spatial stream index feedback frame format ss The stream information may specify multiple spatial streams for multiple STAs 200 or multiple spatial streams allocated to one STA 200. ss The spatial stream index (SS index) of the stream information may include continuous values ​​and discontinuous values.

[0168] Fig.12 (d) indicates that the information for determining the destination STA of the spatial stream includes N sta This is an example of a frame format “SS index feedback for each STA frame format” in the case of a spatial stream index (SS index) for each STA (for example, when the value of the HE behavior field is 6).

[0169] exist Fig.12 The frame format shown in (d) includes, for example, staThe STA information field contains information related to the spatial stream index of each STA. Each STA information field may include, for example, a "Start SS index field" indicating the front spatial stream index and an "N" indicating the number of spatial streams. ss field.

[0170] For example, STA200 may include the corresponding spatial stream front index and stream number in the STA that feedbacks the stream information. Fig.12 The front-end space stream index field and N shown in (d) SS In other words, STA200, for example, will be fed back to AP100 by the front-end spatial stream index~(front-end spatial stream index+N SS -1) to notify the AP 100 of the stream information (eg, spatial stream index) of each STA.

[0171] In addition, Fig.12 In (d), for example, it is also possible to Fig.12 Similarly, the "End SS index field" indicating the end spatial stream index is set instead of N ss field.

[0172] in addition, Fig.12 (a)~ Fig.12 The category field (Category field) included in (d) can indicate the type of behavior frame, for example.

[0173] For example, after receiving the information of the destination STA for determining the spatial stream, the AP 100 may schedule DL MU-MIMO transmission or update the steering matrix.

[0174] For example, Figure 8 As shown, the spatial stream for which the stream information is fed back may be a spatial stream (or STA) corresponding to a signal (eg, an inter-user interference signal) that may interfere with a desired signal.

[0175] Therefore, for example, AP100 can perform scheduling so that the STA that is the transmission source of the feedback information and the STA determined based on the stream information (for example, STA_ID or spatial stream index) contained in the feedback information will not be multiplexed in the same RU.

[0176] In addition, for example, the AP 100 may change the allocated spatial stream index of the DL MU-MIMO so as not to use the spatial stream index (or the spatial stream corresponding to the STA_ID) included in the feedback information.

[0177] In method 1-2, the information related to the spatial stream of the feedback object (in other words, the information that determines the destination STA of the spatial stream) in the feedback information includes information that determines the index information (for example, STA_ID or spatial stream index). In other words, the feedback information does not include information such as the feedback matrix or SNR. Therefore, according to method 1-2, for example, compared with the case where information such as the feedback matrix or SNR is fed back (for example, the feedback format of 11ax, i.e., the compressed beamforming / CQI frame behavior field format), the feedback amount can be reduced.

[0178] [Method 1-3]

[0179] In method 1-3, the STA 200 includes the feedback information in a response signal (eg, ACK or Block ACK) or a negative response signal (Negative-ACK (NACK)) for received data (eg, MU PPDU) and transmits the feedback information.

[0180] Fig.13 (a) shows an example of a frame format "BA frame format" used to send ACK (or block ACK) and NACK in method 1-3.

[0181] exist Fig.13 In the BA frame format shown in (a) of FIG. 1 , for example, feedback information of a fixed length is included in a “Feedback information field”.

[0182] For example, Fig.13 As shown in (b), STA200 transmits (e.g., performs UL MU transmission) a response signal (e.g., BA) according to the MU PPDU transmitted from AP100. At this time, for example, in the case where there is feedback information transmitted (e.g., STA1), STA200 may transmit BA and feedback information in the BA frame format. In addition, STA200 (e.g., STA2) may not include the feedback information in the feedback information field of the BA frame format.

[0183] Fig.14 (a) shows an example of the frame format "ACK frame format" used to send ACK (or block ACK) and NACK in method 1-3.

[0184] exist Fig.14 In the ACK frame format shown in (a) of FIG. 1 , for example, a "Feedback field" indicating feedback information of a variable length is included. Fig.14The ACK frame format shown in (a) of FIG. 1 includes, for example, a "Feedback present field" indicating whether or not feedback information is present. The Feedback present field has, for example, a fixed length.

[0185] For example, when the feedback occurrence field indicates that there is feedback information in the ACK frame format, the feedback field includes a "feedback length field" and a "feedback information field". The feedback length field is, for example, a fixed-length field and indicates the length (for example, the number of bits) of the variable-length feedback information field. In addition, for example, when the feedback occurrence field does not indicate that there is feedback information in the ACK frame format, the length of the feedback field is 0 bits.

[0186] For example, Fig.14 As shown in (b) of FIG. 1 , STA 200 transmits a signal including an ACK frame format based on the BA request (BAR) that has been transmitted from AP 100 to each STA 200 (for example, STA 1 and STA 2). Fig.14 In (b), STA1 includes ACK and feedback information in the ACK frame format and sends it to AP100. In addition, for example, Fig.14 In (b), no feedback information is included, and STA2 includes ACK in the ACK frame format and sends it to AP100.

[0187] According to method 1-3, STA 200 sends a response signal (or a negative response signal) including feedback information (eg, streaming information). Thus, according to method 1-3, STA 200 can send the response signal and feedback information to AP 100 together, thereby reducing the overhead of the preamble part.

[0188] [Method 1-4]

[0189] In method 1-4, STA200 sends a signal to AP100 requesting the transmission of a trigger frame (hereinafter referred to as a "trigger frame request"), and the trigger frame prompts STA200 to transmit feedback information. In other words, STA200 requests AP100, which is the transmission source of multiple spatial streams in multi-user transmission, to transmit the following signal, which triggers the transmission of feedback information including stream information.

[0190] Fig.15 This is a sequence diagram showing an example of a case where the STA 200 transmits a trigger frame request to the AP 100 .

[0191] For example, in a case where feedback information is generated based on the MU PPDU received from the AP 100 , the STA 200 (eg, STA 1 ) transmits a trigger frame request to the AP 100 .

[0192] In addition, the trigger frame request may be sent at a timing after sending a response signal (eg, ACK) to the AP 100 . In addition, the STA 200 may newly acquire carrier sense and send a trigger frame request to the AP 100 , for example.

[0193] In addition, STA200 may, for example, include parameters related to the feedback information (eg, the length of the feedback information) in the trigger frame request.

[0194] In addition, the STA 200 may include the trigger frame request in a response signal or a negative response signal and transmit the response signal.

[0195] When receiving the trigger frame request, the AP 100 sends a message to the STA 200 ( Fig.15 STA1) in the AP100 sends a trigger frame, which requests to send feedback information. The trigger frame may also be a beamforming report poll, for example. In addition, AP100 may send a trigger frame only when it receives a trigger frame request from more than a predetermined number of STA200.

[0196] When receiving the trigger frame sent from AP100, STA200 sends feedback information to AP100 based on the control signal included in the trigger frame. The control signal included in the trigger frame may include information related to the sending of feedback information, such as bandwidth, transmission power, allocated RU, MCS, or allocated spatial stream.

[0197] In addition, AP100 may also include a newly added control signal when STA200 sends feedback information in, for example, a trigger frame (for example, a common information field (Trigger Dependent Common Info field) dependent on the trigger frame). The newly added control signal may include, for example, information such as feedback category, number of subcarrier groups, or codebook size.

[0198] According to method 1-4, when the 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.

[0199] [Method 1-5]

[0200] In method 1-5, STA 200 transmits a signal notifying transmission of feedback information (hereinafter referred to as "Feedback present") to AP 100. In other words, STA 200 notifies transmission of feedback information including stream information to AP 100, which is the transmission source of multiple spatial streams in multi-user transmission.

[0201] Fig.16 This is a sequence diagram showing an example of a case where the STA 200 transmits “Feedback Present”.

[0202] For example, in Fig.16 In the case where the signal sent to STA2 causes great interference to the signal sent to STA1 regarding the MU PPDU sent by AP100, STA1 will fail to decode the signal, but STA2 will succeed in decoding the signal.

[0203] At this time, STA1 may generate the following feedback information, which includes stream information related to the spatial stream corresponding to the signal sent to STA2. In method 1-5, STA1 sends "Feedback Present" to AP100 before sending the feedback information. For example, STA1 may send "Feedback Present" to AP100 after a short inter-frame space (SIFS) has passed since STA2 sent a response signal (e.g., ACK) to AP100.

[0204] When receiving "Feedback Present", AP100 stops the transmission of MU-MIMO signals including STA1 for a certain period of time, for example, until the steering matrix is ​​updated based on the feedback information from STA1. In other words, AP100 determines that even if the MU-MIMO signal to STA1 is transmitted based on the steering matrix reserved for STA1, the possibility of STA1 decoding failure is still high, and stops the signal transmission to STA1 until the steering matrix is ​​updated.

[0205] After sending "Feedback Present", STA1 sends feedback information. For example, STA1 may newly acquire carrier sense and send feedback information. In addition, STA1 may include "Feedback Present" in a response signal or a negative response signal.

[0206] According to method 1-5, STA200 notifies in advance that feedback information is sent, so AP100 can suppress MU-MIMO transmission based on a non-optimal steering matrix (e.g., a steering matrix before updating). Therefore, AP100 can suppress retransmission caused by decoding errors in STA200, so the system throughput can be improved.

[0207] An example of a method of feeding back stream information in the STA 200 has been described above.

[0208] As described above, in this embodiment, the STA 200 determines a spatial stream for feedback stream information among a plurality of spatial streams in multi-user transmission, and transmits stream information corresponding to the determined spatial stream.

[0209] By sending the stream information (in other words, feedback), STA200 can, for example, send feedback information corresponding to a spatial stream whose actual reception quality (for example, the quality measured by STA200) is different from the reception quality considered by AP100 to AP100. In other words, STA200 can, for example, decide not to send feedback information corresponding to a spatial stream whose actual reception quality is the same or can be considered to be the same as the reception quality considered by AP100. Thus, according to this embodiment, the feedback information sent by STA200 can be reduced, and thus the transmission efficiency can be improved.

[0210] In addition, STA200 can, for example, send feedback information to AP100 when the actual reception quality of each spatial stream is different from the reception quality considered by AP100. Therefore, according to this embodiment, for example, when the actual reception quality is the same as or can be considered to be the same as the reception quality considered by AP100, the feedback information can be sent less, thereby improving the transmission efficiency.

[0211] Based on the above, according to the present embodiment, it is possible to improve transmission efficiency in spatial multiplexing transmission such as MU-MIMO transmission.

[0212] (Implementation Method 2)

[0213] [Structure of wireless communication system]

[0214] A wireless communication system according to an embodiment of the present invention includes at least one AP 300 and a plurality of STAs 400 .

[0215] For example, in DL communication (e.g., transmission and reception of DL data), AP300 (or, also referred to as "downlink wireless transmission device") can perform DL MU-MIMO transmission to multiple STA400 (or, also referred to as "downlink wireless reception device"). Each STA400 can, for example, generate feedback information based on the signal (e.g., DL MU PPDU) transmitted by DL MU-MIMO, and send (e.g., perform UL SU transmission or UL MU transmission) the feedback information to AP300.

[0216] In this embodiment, STA400 feeds back channel coefficients related to one or a portion of the spatial streams of the inter-user interference signal to AP300 based on the reception quality of the reference signal (e.g., LTF) included in the non-NDP MU PPDU. The channel coefficients are, for example, N RX ×N ss A component of the channel estimation matrix represented by . In addition, the channel coefficient is, for example, s In addition, N s Indicates the number of subcarriers allocated to STA400.

[0217] <AP300 Configuration Example>

[0218] Fig.17 is a block diagram showing an example of the structure of AP300. Fig.17 In the embodiment 1 ( Figure 5 ) are given the same reference numerals and their descriptions are omitted. Figure 5 ), AP300 includes a reference signal retaining unit 301, and the operation of the steering matrix generating unit 302 (for example, the operation related to the channel coefficient (or the reference signal)) is the same as that of AP100 ( Figure 5 )different.

[0219] When the data signal input from the decoding unit 102 includes a reference signal, the reference signal storage unit 301 stores the reference signal in a buffer. When the steering matrix generation unit 302 updates the steering matrix, the reference signal storage unit 301 outputs the reference signal stored in the buffer to the steering matrix generation unit 302.

[0220] Here, the "reference signal" may also be, for example, one of the channel coefficients contained in the estimated channel estimation matrix. For example, the reference signal may also use a channel coefficient associated with an expected signal stream whose power is above a threshold (for example, maximum power). In addition, the reference signal may also use, for example, a channel estimation value associated with a specified signal sent before a reference signal used for channel estimation. The specified signal may include, for example, a legacy short training field (Legacy-short training field, L-STF) or L-LTF, and a non-legacy STF. In addition, the specified signal may also be, for example, a signal sequence newly added to the preamble portion.

[0221] The steering matrix generation unit 302 generates a steering matrix based on the information related to the scheduling input from the scheduling unit 103 .

[0222] In addition, when a data signal including feedback information (e.g., a standardized channel coefficient) 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 may update a portion of the reserved steering matrix. In addition, when an existing steering matrix is ​​updated based on the feedback information, the steering matrix generation unit 302 may, for example, standardize the existing steering matrix based on a reference signal input from the reference signal retention unit 301, and adjust the amplitude and phase with respect to the feedback information.

[0223] <Configuration example of STA400>

[0224] Fig.18 is a block diagram showing a structural example of STA400. Fig.18 In the embodiment 1 ( Figure 6 ) are given the same reference numerals and their descriptions are omitted. Figure 6 ) compared to STA400, STA400 includes a reference signal storage unit 402, and the operation of the feedback determination unit 401 is the same as that of STA200 ( Figure 6 )different.

[0225] The feedback determination unit 401 determines whether to feed back information related to a spatial stream (eg, stream information). In other words, the feedback determination unit 401 determines a spatial stream to which stream information is fed back, for example, among a plurality of spatial streams in multi-user transmission.

[0226] For example, the feedback determination section 401 generates reception quality information based on the error determination result of the data signal input from the data decoding section 203 and the reference signal included in the preamble input from the preamble demodulation section 202 .

[0227] In addition, the feedback determination unit 401 determines whether each component (eg, corresponding to a channel coefficient) of reception quality (eg, channel estimation matrix) generated based on the reference signal satisfies a predetermined threshold (in other words, a condition), for example.

[0228] When the channel coefficient satisfies a predetermined threshold, the feedback determination unit 401, for example, decides to feed back (in other words, transmit) the stream information. On the other hand, when the channel coefficient does not satisfy the predetermined threshold, the feedback determination unit 401, for example, decides not to transmit the stream information. The feedback determination unit 401, for example, may decide whether to feed back the stream information for the channel coefficients related to a plurality of spatial streams in multi-user transmission.

[0229] The feedback determination unit 401 generates feedback information including, for example, stream information corresponding to a channel coefficient associated with the determined spatial stream, and outputs the feedback information to the transmission signal generation unit 205 .

[0230] The feedback information may include, for example, an estimated channel coefficient, a spatial stream index for determining the channel coefficient, a receiving antenna index, a subcarrier index, or an RU index. In addition, for example, the channel coefficient included in the feedback information may also be a relative value relative to a reference signal. For example, the channel coefficient fed back may also be a value obtained by standardization using a reference signal.

[0231] For example, when a reference signal is newly determined, the feedback determination unit 401 adds the reference signal to the feedback information. Also, for example, when there is no component of a reference signal that satisfies a threshold value related to predetermined reception quality information (in other words, when there is no feedback information), the feedback determination unit 401 does not output the signal to the transmission signal generation unit 205. Also, when a reference signal is newly determined, the feedback determination unit 401 outputs the reference signal to the reference signal storage unit 402.

[0232] The reference signal storage unit 402 stores the reference signal input from the feedback determination unit 401 in a buffer. When the feedback determination unit 401 feeds back the channel coefficients included in the feedback information, the reference signal storage unit 402 outputs the reference signal stored in the buffer to the feedback determination unit 401 .

[0233] [AP and STA operation example]

[0234] Next, an operation example of the AP 300 and the STA 400 according to the present embodiment will be described.

[0235] For example, imagine the following situation, that is, if Fig.19 As shown, an AP 300 having three transmitting antennas transmits a MUPPDU to each of three STAs 400 (eg, STA1, STA2, and STA3) having one receiving antenna.

[0236] At this time, the reception signals of STA1 to STA3 are expressed as, for example, the following equation (2).

[0237]

[0238] Here, x represents the transmitted signal component, y represents the received signal component, w represents the steering matrix component, and h represents the channel estimation matrix component. For example, the received signal component y in STA1 is 1 This is represented by the following formula (3).

[0239] y 1 =(h 11 w 11 +h 12 w 21 +h13 w 31 )x 1 +(h 11 w 12 +h 12 w 22 +h 13 w 32 )x 2 +(h 11 w 13 +h 12 w 23 +h 13 w 33 )x 3 (3)

[0240] Each transmitted signal component x in formula (3) 1 、x 2 and x 3 The coefficients of are the effective channel coefficients. For example, the effective channel coefficients are defined as the following equations (4), (5) and (6).

[0241]

[0242] In addition, according to equations (4), (5) and (6), for example, the channel coefficient h 13 This is expressed as the following formula (7).

[0243]

[0244] According to equation (7), for example, given the known steering matrix and effective channel coefficients (e.g., h eff11 、h eff12 and h eff13 ) derive the channel coefficient h 13 In addition, other channel coefficients h can also be derived in the same way as in equation (7): 11 and the channel coefficient h 12 .

[0245] For example, by measuring Fig.19 As shown, for the reference signal of the MU-PPDU received by STA1, it is assumed that the power of the reference signal corresponding to the inter-user interference signal sent to STA2 is large (for example, above the threshold), and the power of the reference signal corresponding to the inter-user interference signal sent to STA3 is small (for example, less than the threshold). In this case, for example, STA1 determines the feedback of the stream information related to the inter-user interference signal sent to STA2.

[0246] For example, STA1 calculates the effective channel coefficient h associated with the inter-user interference signal of STA2 among the effective channel coefficients obtained by channel estimation based on the reference signal. eff12Then, STA1 can include the standardized effective channel coefficient h' eff12 The feedback information of the reference signal is sent to AP300.

[0247] AP300 obtains the normalized effective channel coefficient h' based on the feedback information received from STA1 eff12 AP300 is based on the effective channel coefficient h′ obtained by normalization. eff12 , separate the steering matrix, and derive the channel estimate (e.g., the channel coefficient h 13 ).

[0248] At this time, AP300 determines that, for example, eff12 Compared with the effective channel coefficient h related to the expected signal that is not included in the feedback information eff11 Therefore, the AP 300 may use the channel coefficients (e.g., h) obtained by the previous NDP detection. 11 、h 12 and h 13 ) and a known steering matrix (e.g., containing w 11 、w 21 and 31 ), derive the effective channel coefficient h of the expected signal eff11 (For example, refer to formula (4)).

[0249] In addition, for example, according to the effective channel coefficient h eff13 , the interference of the inter-user interference signal of STA3 not included in the feedback information has been fully suppressed, so AP300 can be regarded as |h eff13 |≒0.

[0250] Thus, for example, regarding the channel coefficient h shown in equation (7) 13 Based on the derivation of the effective channel coefficient h of an inter-user interference signal fed back, AP300 can eff12 (For example, the effective channel coefficient h' obtained by normalization eff12 ), and the known channel coefficients and the known steering matrix, derive the channel coefficients h 13 The AP300 can derive other channel coefficients in the same manner as the derivation of the channel coefficient h13.

[0251] The AP 300 may, for example, newly calculate steering matrix components based on the derived channel coefficients. For example, the newly calculated steering matrix components may also be components for suppressing interference caused by a signal sent to STA2 to a signal sent to STA1.

[0252] Next, AP300 updates the steering matrix based on the calculated steering matrix components. At this time, AP300 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.

[0253] In this embodiment, STA400 generates feedback information based on, for example, a channel coefficient (e.g., an effective channel coefficient) related to a portion of a signal (e.g., an inter-user interference signal) in a channel estimation value (e.g., a channel estimation matrix) related to a spatial stream in multi-user transmission. In other words, STA400, for example, sends a portion of the channel estimation value containing the spatial stream (the effective channel coefficient h' in the above example) to AP300. eff12 ) feedback information.

[0254] By generating the feedback information, for example, compared with the case of feeding back the channel estimation value of the spatial stream unit, the feedback information overhead can be reduced. For example, when the amount of feedback information is minimal, the STA 400 only needs to generate feedback information including one effective channel coefficient per tone or group tone, thereby reducing the feedback information overhead.

[0255] Furthermore, the STA 400 can directly obtain the effective channel coefficient based on the reference signal included in the non-NDP MU PPDU transmitted from the AP 300 , for example, and thus can easily generate feedback information.

[0256] In addition, STA400 feeds back the value obtained by normalizing the effective channel coefficient using a specified value (e.g., a reference signal) and the reference signal to AP300. By feeding back the normalized value, for example, when updating the steering matrix, AP300 can adjust the amplitude and phase between the feedback information and the retained information (e.g., steering matrix components).

[0257] Next, method 2-1 will be described as an example of a method for feeding back stream information in the STA 400 .

[0258] [Method 2-1]

[0259] In method 2-1, the STA 400 quantizes the channel coefficient (eg, channel estimation component) normalized by the reference signal within an amplitude range narrower than the amplitude of the reference signal.

[0260] For example, the channel coefficient normalized by the reference signal represents the relative amplitude with respect to the reference signal (in other words, the difference with respect to the reference signal).

[0261] Fig. 20An example of the range of relative amplitudes corresponding to the channel coefficients is shown. Fig. 20 In the example, the relative amplitude relative to the reference signal is set to a range of 0 to 1 / 4. For example, the relative amplitude is expressed by any value from 0 to 3 to represent the amplitude accuracy (in other words, granularity) of four modes, 1 / 16, 2 / 16, 3 / 16, or 4 / 16.

[0262] In this way, STA400 can, for example, variably set the relative amplitude accuracy (in other words, the performance range) according to the value of the channel coefficient (e.g., relative amplitude) obtained by standardization, and quantize the channel coefficient obtained by standardization based on the set relative amplitude accuracy.

[0263] For example, when the relative amplitude value is smaller (in other words, when the difference between the normalized channel coefficient and the reference signal is smaller), STA400 can set the relative amplitude accuracy value to be smaller. With this setting, for example, when the number of bits allocated to the normalized channel coefficient is fixed, for example, the smaller the relative amplitude value is, the STA400 can quantize the normalized channel coefficient with a finer granularity. In other words, for example, the larger the relative amplitude value is, the STA400 can quantize the normalized channel coefficient with a coarser granularity over a larger range.

[0264] STA400 can, for example, convert the relative amplitude accuracy (e.g., Fig. 20 A value between 0 and 3 as shown) is included in feedback information together with the channel coefficient and fed back to AP 300.

[0265] In addition, for example, when the components of the inter-user interference signal are fed back multiple times with respect to the same channel coefficient, the STA 400 may set the relative amplitude accuracy to be smaller in sequence for each feedback. By setting the relative amplitude accuracy, for example, the suppression effect of the steering matrix on the inter-user interference signal may also be gradually corrected.

[0266] According to method 2-1, the amplitude of the channel coefficient as a relative value can be expressed with high accuracy using a smaller number of bits, and thus the AP300 can improve the correction accuracy of the steering matrix.

[0267] In the above, each embodiment of the present invention has been described.

[0268] (Other embodiments)

[0269] (1) Two or more methods among the methods 1-1 to 1-5 and the method 2-1 may be combined.

[0270] For example, in the case of combining method 1-1 and method 1-2, the transmission signal fed back by the STA may include both the compressed beamforming / CQI frame behavior field format and the independent spatial stream index feedback frame format in the data part. In this case, the STA 200 may not replace the sounding session token number field with the front-end spatial stream index field as in method 1-1, but may use the independent spatial stream index feedback frame format to notify the AP 100 of the index information of the fed-back spatial stream. Through this notification method, for example, the spatial stream index can be discretely (in other words, discontinuously) specified, and thus the feedback amount can be reduced.

[0271] In addition, as an example, the independent spatial stream index feedback frame format of method 1-1 and method 1-2 is combined here, but other frame formats for notifying spatial stream indexes may also be used.

[0272] (2) Methods 1-1 to 1-5 and method 2-1 may also be applied to the following situation, which refers to the situation where a STA sends feedback information to multiple APs in multi-AP coordination.

[0273] (3) Not limited to the transmission of feedback information for non-NDP PPDU, methods 1-1 to 1-5 and method 2-1 can also be applied to NDP.

[0274] (4) When the AP controls multiple DL MU-MIMO transmissions, the AP may include an identifier for determining the MU-MIMO allocation mode (e.g., called "MU-MIMO ID") in a DL MU-MIMO signal (e.g., a user field of a preamble) and transmit the signal.

[0275] At this time, for example, the STA can obtain the MU-MIMO ID from the received DL MU-MIMO signal and include the MU-MIMO ID in the feedback information and send it. Thus, the AP can identify which DL MU-MIMO signal the feedback information is for based on the MU-MIMO ID contained in the feedback information.

[0276] (5) The STA can send the feedback information to the AP at one time, or divide it into multiple frames and send them to the AP.

[0277] (6) STAs may also give priority to feeding back at least one of an expected signal and an inter-user interference signal for which feedback information has not been sent for a certain period of time.

[0278] (7) In Embodiments 1 and 2, in addition to the reception quality of the reference signal included in the non-NDP PPDU, the STA may determine the stream information to be fed back based on conditions other than the reception quality.

[0279] For example, the STA determines, for each spatial stream, a predetermined condition related to the reception quality of the reference signal and a condition other than the reception quality, and feeds back information related to the spatial stream that satisfies all the conditions.

[0280] Conditions other than reception quality may also be, for example, a feedback interval. The feedback interval may also be the number of packets of non-NDP MU PPDU received since the STA last sent feedback. In addition, the feedback interval may also be the elapsed time since the STA last sent feedback. When the prescribed feedback interval has passed, the STA sends feedback. In addition, when the prescribed feedback interval has not passed, the STA decides not to send feedback.

[0281] Conditions other than reception quality may also be, for example, the MCS of the data portion of the non-NDP PPDU. When the MCS level of the data portion obtained from the preamble portion of the non-NDP PPDU is greater than the predetermined MCS level, the STA may increase the feedback frequency. In addition, when the MCS level of the data portion obtained from the preamble portion of the non-NDP PPDU is less than the predetermined MCS level, the STA may reduce the feedback frequency.

[0282] Conditions other than reception quality may also be, for example, the number of spatial streams allocated to the STA. When the number of allocated spatial streams is greater than the predetermined number of allocated spatial streams, the STA may also reduce the feedback frequency. In addition, when the number of allocated spatial streams is less than the predetermined number of allocated spatial streams, the STA may also increase the feedback frequency.

[0283] Conditions other than reception quality may also be, for example, the upper limit number of spatial streams sent in one feedback. When there are M spatial streams that satisfy the predetermined conditions related to 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).

[0284] Conditions other than reception quality may also be, for example, the minimum number of spatial streams required for feedback. The STA provides feedback only when there are N or more spatial streams that satisfy the predetermined conditions related to the reception quality of the reference signal. In addition, when the number of spatial streams that satisfy the predetermined conditions related to the reception quality of the reference signal is less than N, the STA decides not to send feedback.

[0285] Conditions other than reception quality may be determined based on, for example, STA capabilities. In addition, the AP may include conditions other than reception quality in NDPA, beacon, or management frame, and notify the STA.

[0286] In addition, the STA may also control the threshold of the reception quality information based on conditions other than the reception quality. In addition, the STA may also control the conditions other than the reception quality based on the reception quality information.

[0287] (8) In the above embodiment, a configuration example based on the 11ax frame format is described as an example. However, the format to which an embodiment of the present invention is applied is not limited to the 11ax format.

[0288] (9) In the above embodiments, the operation in DL communication is described, but an embodiment of the present invention is not limited to DL communication, and can be applied to UL communication or sidelink, for example.

[0289] (10) The present invention can be implemented by software, hardware, or software in cooperation with hardware. The functional blocks used in the description of the above embodiments are partially or entirely implemented as LSI (Large Scale Integration) as an integrated circuit, and the processes described in the above embodiments may also be partially or entirely controlled by one LSI or a combination of LSIs. LSI may be composed of individual chips, or may be composed of one chip in a manner that includes part or all of the functional blocks. LSI may also include data input and output. LSI may also be referred to as "IC (Integrated Circuit)", "System LSI", "Super LSI", or "Ultra LSI" depending on the degree of integration. The method of integrated circuitization is not limited to LSI, and may also be implemented by a dedicated circuit, a general-purpose processor, or a dedicated processor. In addition, an FPGA (Field Programmable Gate Array) that can be programmed after LSI manufacturing, or a reconfigurable processor that can reconfigure the connection or setting of the circuit blocks inside the LSI may also be used. The present invention can also be implemented as digital processing or analog processing. Furthermore, if integrated circuit technology that replaces LSI emerges with the advancement of semiconductor technology or the derivation of other technologies, it is of course possible to use this technology to achieve the integration of functional blocks. There is also the possibility of applying biotechnology, etc.

[0290] The present invention can be implemented in all kinds of devices, equipment, and systems (collectively referred to as "communication devices") with communication functions. The communication device may also include a wireless transceiver and a processing / control circuit. The wireless transceiver may also include a receiving unit and a transmitting unit, or perform the functions of these parts. The wireless transceiver (transmitting unit, receiving unit) may also include an RF (Radio Frequency) module and one or more antennas. The RF module may also include an amplifier, an RF modulator / demodulator, or a device similar to these. Non-limiting examples of communication devices include: phones (mobile phones, smart phones, etc.), tablet computers, personal computers (PCs) (laptops, desktops, notebook computers, etc.), cameras (digital cameras, digital video cameras, etc.), digital players (digital audio / video players, etc.), wearable devices (wearable cameras, smart watches, tracking devices, etc.), game consoles, e-book readers, telehealth / telemedicine (telehealth / medical prescription) equipment, vehicles with communication functions or transportation vehicles (cars, airplanes, ships, etc.), and combinations of the above-mentioned various devices.

[0291] Communication devices are not limited to portable or mobile devices, but also include all kinds of devices, equipment, and systems that cannot be carried or fixed. For example, they include: smart home devices (home appliances, lighting equipment, smart meters or meters, control panels, etc.), vending machines, and all other "things" that can exist on the IoT (Internet of Things) network.

[0292] The communication includes data communication performed by a cellular system, a wireless LAN (Local Area Network) system, a communication satellite system, etc., and also includes data communication performed by a combination of these systems.

[0293] In addition, the communication device also includes devices such as controllers or sensors connected or linked to the communication device that performs the communication function described in the present invention. For example, it includes a controller or sensor that generates a control signal or data signal used by the communication device that performs the communication function of the communication device.

[0294] In addition, the communication device includes infrastructure equipment that communicates with the above-mentioned non-limiting various devices or controls the above-mentioned various devices, such as base stations, access points, and all other devices, equipment, and systems.

[0295] A communication device according to an embodiment of the present invention includes: a control circuit that determines a spatial stream for feeding back second information based on first information related to reception quality of multiple spatial streams; and a transmission circuit that transmits the second information related to the determined spatial stream.

[0296] In one embodiment of the present invention, the second information includes information related to a portion of the plurality of spatial streams.

[0297] In one embodiment of the present invention, the second information is included in a compressed beamforming / CQI frame behavior field format signal.

[0298] In one embodiment of the present invention, the second information includes information for identifying a terminal assigned to the determined spatial stream.

[0299] In one embodiment of the present invention, the second information includes information for identifying the determined spatial stream.

[0300] In one embodiment of the present invention, the second information is included in a response signal to received data.

[0301] In one embodiment of the present invention, the transmitting circuit requests the transmission sources of the multiple spatial streams to transmit the following signal, where the signal triggers the transmission of the second information.

[0302] In one embodiment of the present invention, the transmitting circuit transmits a signal to notify transmission sources of the plurality of spatial streams of transmission of the second information.

[0303] In one embodiment of the present invention, the second information includes the following value, where the value is a value obtained by normalizing a portion of components of the channel estimation values ​​of each of the plurality of spatial streams using a reference signal.

[0304] In one embodiment of the present invention, the control circuit quantizes the channel estimation component obtained by the normalization within an amplitude range narrower than an amplitude of the reference signal.

[0305] In a communication method of an embodiment of the present invention, a communication device performs the following steps: based on first information related to reception quality of multiple spatial streams, determining a spatial stream for feeding back second information; and transmitting the second information related to the determined spatial stream.

[0306] The disclosure contents 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.

[0307] Industrial Applicability

[0308] One embodiment of the present invention is useful for a wireless communication system.

Claims

1. A communication device, It is characterized in that have: A sending circuit sends a reference signal; A receiving circuit for receiving feedback information; and The control circuit uses the feedback information for processing.

2. A communication device, It is characterized in that have: A receiving circuit, receiving a reference signal; A control circuit uses the reference signal to perform channel estimation processing; and Sending circuit, sending feedback information.

3. A communication method, It is characterized in that The communication device performs the following processing: sending a reference signal; receiving feedback; and The feedback information is used for processing.

4. A communication method, It is characterized in that The communication device performs the following processing: receiving a reference signal; Using the reference signal to perform channel estimation processing; and Send feedback.

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