# US 10,873,379 B1 · Systems and methods for performing implicit sounding in multi-user multiple input multiple output (MU-MIMO) systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,873,379 B1 - Document ID: US10873379B1 - Status: Granted - Kind: B1 - Application number: 16/569,262 - Filed: 2019-09-12 - Granted: 2020-12-22 - Earliest claimed: 2017-06-21 - Assignees: Marvell Asia Pte Ltd - Applicants: Marvell Asia Pte, Ltd. - Inventors: Hongyuan Zhang; Sudhir Srinivasa; Christian R. Berger; Xiayu Zheng - Web page: https://patentgrep.com/patent/US10873379B1 ## CPC - H04B 7/0617: {for beam forming} - H04L 25/0204: {of multiple channels} - H04B 7/0421: {utilizing implicit feedback, e.g. steered pilot signals} - H04B 7/0452: Multi-user MIMO systems - H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting - H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]} - H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection} - H04B 7/0656: {at the transmitter, e.g. error detection at base station} - H04L 1/1685: {the supervisory signal being transmitted in response to a specific request, e.g. to a polling signal} - H04L 25/03898: {codebook-based design (selection of codebook or precoding matrix for MIMO diversity systems H04B7/0456)} - H04L 5/0023: {Time-frequency-space} - H04L 5/0048: {Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091)} - H04L 5/0057: {Physical resource allocation for CQI} - H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract Embodiments described herein provide a method for performing beamforming in a multiple-user-multiple-input-multiple-output (MUMIMO) system. At a MUMIMO access point, MUMIMO data may be received from a station of a plurality of stations. Uplink channel state information may be obtained, from the MUMIMO data, representing an uplink channel between the station and the MUMIMO access point. The uplink channel includes signals transmitted from the station using the second number of antennas. Downlink channel state information may be computed, based on the uplink channel state information, representing a downlink channel between the MUMIMO access point and the station. ## Claims ### Claim 1 A method for performing beamforming in a multiple-user-multiple-input-multiple-output (MUMIMO) system, the method comprising: receiving, at an MUMIMO access point, an MUMIMO packet from a station of a plurality of stations, wherein the MUMIMO access point has a first number of antennas, and wherein the station has a second number of antennas less than the first number of antennas; obtaining, from the MUMIMO packet, uplink channel state information representing an uplink channel between the station and the MUMIMO access point, the uplink channel including signals transmitted from the station using the second number of antennas; computing, based on the uplink channel state information, downlink channel state information representing a downlink channel between the MUMIMO access point and the station, the downlink channel including signals transmitted from the MUMIMO access point using the first number of antennas; and transmitting data from the MUMIMO access point to the plurality of stations using the first number of antennas based on the downlink channel state information. ### Claim 2 (depends on 1) The method of claim 1 further comprising: computing, based on the uplink channel state information, an uplink channel state information matrix having a size corresponding to the first number of antennas; generating a downlink channel state information matrix by transposing the uplink channel state information matrix; and computing, based on the downlink channel state information matrix, a precoding matrix at the MUMIMO access point for transmitting the data to the plurality of stations. ### Claim 3 (depends on 2) The method of claim 2, wherein the station is a first station, the MUMIMO packet is a first MUMIMO packet, and the downlink channel state information matrix is a first downlink channel state information matrix, and the method further comprising: receiving, at the MUMIMO access point, a second MUMIMO packet from a second station of a plurality of stations, wherein the second station has a third number of antennas less than the second number of antennas; computing, based on uplink channel state information of the data received from the second station, a second uplink channel state information matrix having a size corresponding to the first number of antennas; and generating a second downlink channel state information matrix by transposing the second uplink channel state information matrix; wherein computing the precoding matrix at the MUMIMO access point comprises combining the first and second downlink channel state information matrices. ### Claim 4 (depends on 2) The method of claim 2, wherein the size of the uplink channel state information matrix is Nr×Nss, and wherein the size of the downlink channel state information matrix is Nss×Nr, where Nr is equal to the first number of antennas and Nss is equal to the second number of antennas. ### Claim 5 (depends on 2) The method of claim 2 further comprising: retrieving a calibration correction matrix from storage; and applying the calibration correction matrix to the downlink channel state information matrix before computing the precoding matrix. ### Claim 6 (depends on 2) The method of claim 2 further comprising: retrieving a calibration correction matrix from storage; and applying the calibration correction matrix to the precoding matrix. ### Claim 7 (depends on 1) The method of claim 1, wherein obtaining the uplink channel state information comprises processing a predetermined symbol of the data received by each of the antennas of the MUMIMO access point to generate the uplink channel state information corresponding to each of the antennas of the MUMIMO access point. ### Claim 8 (depends on 1) The method of claim 1 further comprising: transmitting from the MUMIMO access point to the plurality of stations at least one of a null data packet, a junk data packet, and a Transmission Control Protocol (TCP) null data packet; and causing the station to transmit at least one of Block Acknowledgement (BA/ACK) frame and a transmission control protocol (TCP) acknowledgements (ACKs) frame in response to the station receiving the at least one of the null data packet, the junk data packet, and the TCP null data packet, wherein the downlink channel state information is computed periodically. ### Claim 9 (depends on 1) The method of claim 1 further comprising: communicating information between the MUMIMO access point and another wireless device; obtaining a raw channel state information estimate of a downlink channel and an uplink channel of at least one of the MUMIMO access point antennas used in communicating the information; computing at least one of a phase and magnitude difference between the downlink and uplink channels; and generating a calibration matrix based on the computed at least one of a phase and magnitude difference. ### Claim 10 (depends on 9) The method of claim 9, wherein the calibration matrix is either constant across all subcarriers of the MUMIMO access point or different for each subcarrier of the MUMIMO access point. ### Claim 11 (depends on 1) The method of claim 1, wherein obtaining, from the MUMIMO packet, uplink channel state information comprises obtaining uplink channel state information from at least one selected from a group of a preamble of the MUMIMO packet and a postamble of the MUMIMO packet. ### Claim 12 A system for performing beamforming in a multiple-user-multiple-input-multiple-output (MUMIMO) system, the system comprising: control circuitry configured to: receive, at an MUMIMO access point, an MUMIMO packet from a station of a plurality of stations, wherein the MUMIMO access point has a first number of antennas, and wherein the station has a second number of antennas less than the first number of antennas; obtain, from the MUMIMO packet, uplink channel state information representing an uplink channel between the station and the MUMIMO access point, the uplink channel including signals transmitted from the station using the second number of antennas; compute, based on the uplink channel state information, downlink channel state information representing a downlink channel between the MUMIMO access point and the station, the downlink channel including signals transmitted from the MUMIMO access point using the first number of antennas; and transmit data from the MUMIMO access point to the plurality of stations using the first number of antennas based on the downlink channel state information. ### Claim 13 (depends on 12) The system of claim 12, wherein the control circuitry is further configured to: compute, based on the uplink channel state information, an uplink channel state information matrix having a size corresponding to the first number of antennas; generate a downlink channel state information matrix by transposing the uplink channel state information matrix; and compute, based on the downlink channel state information matrix, a precoding matrix at the MUMIMO access point for transmitting the data to the plurality of stations. ### Claim 14 (depends on 13) The system of claim 13, wherein the station is a first station, the MUMIMO packet is a first MUMIMO packet, and the downlink channel state information matrix is a first downlink channel state information matrix, and wherein the control circuitry is further configured to: receive, at the MUMIMO access point, a second MUMIMO packet from a second station of a plurality of stations, wherein the second station has a third number of antennas less than the second number of antennas; compute, based on uplink channel state information of the data received from the second station, a second uplink channel state information matrix having a size corresponding to the first number of antennas; and generate a second downlink channel state information matrix by transposing the second uplink channel state information matrix; wherein the control circuitry is further configured to compute the precoding matrix at the MUMIMO access point by combining the first and second downlink channel state information matrices. ### Claim 15 (depends on 13) The system of claim 13, wherein the size of the uplink channel state information matrix is Nr×Nss, and wherein the size of the downlink channel state information matrix is Nss×Nr, where Nr is equal to the first number of antennas and Nss is equal to the second number of antennas. ### Claim 16 (depends on 13) The system of claim 13, wherein the control circuitry is further configured to: retrieve a calibration correction matrix from storage; and apply the calibration correction matrix to the downlink channel state information matrix before computing the precoding matrix. ### Claim 17 (depends on 13) The system of claim 13, wherein the control circuitry is further configured to: retrieve a calibration correction matrix from storage; and apply the calibration correction matrix to the precoding matrix. ### Claim 18 (depends on 12) The system of claim 12, wherein the control circuitry is configured to obtain the uplink channel state information by processing a predetermined symbol of the data received by each of the antennas of the MUMIMO access point to generate the uplink channel state information corresponding to each of the antennas of the MUMIMO access point. ### Claim 19 (depends on 12) The system of claim 12, wherein the control circuitry is further configured to: transmit from the MUMIMO access point to the plurality of stations at least one of a null data packet, a junk data packet, and a TCP null data packet; and cause the station to transmit as the data at least one of block acknowledgement (BA/ACK) frame and a transfer control protocol (TCP) acknowledgement (ACKs) frame in response to the station receiving the at least one of the null data packet, the junk data packet, and the TCP null data packet, wherein the downlink channel state information is computed periodically. ### Claim 20 (depends on 12) The system of claim 12, wherein the control circuitry is further configured to: communicate information between the MUMIMO access point and another wireless device; obtain a raw channel state information estimate of a downlink channel and an uplink channel of at least one of the MUMIMO access point antennas used in communicating the information; compute at least one of a phase and magnitude difference between the downlink and uplink channels; and generate a calibration matrix based on the computed at least one of a phase and magnitude difference. ### Claim 21 (depends on 20) The system of claim 20, wherein the calibration matrix is either constant across all subcarriers of the MUMIMO access point or different for each subcarrier of the MUMIMO access point. ### Claim 22 (depends on 12) The system of claim 12, wherein the control circuitry is configured to obtain, from the MUMIMO packet, uplink channel state information by obtaining uplink channel state information from at least one selected from a group of a preamble of the MUMIMO packet and a postamble of the MUMIMO packet.