# US 8,543,070 B2 · Reduced complexity beam-steered MIMO OFDM system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,543,070 B2 - Document ID: US8543070B2 - Status: Granted - Kind: B2 - Application number: 11/481,705 - Filed: 2006-07-05 - Published: 2007-10-25 - Granted: 2013-09-24 - Earliest claimed: 2006-04-24 - Assignees: QUALCOMM Incorporated - Applicants: Steven J. Howard; John W. Ketchum; Mark S. Wallace; Jay Rodney Walton - Inventors: Steven J. Howard; John W. Ketchum; Mark S. Wallace; Jay Rodney Walton - Web page: https://patentgrep.com/patent/US8543070B2 ## CPC - H04B 7/0421: {utilizing implicit feedback, e.g. steered pilot signals} - H04B 7/0634: {Antenna weights or vector/matrix coefficients} - H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection} - H04B 7/066: {Combined feedback for a number of channels, e.g. over several subcarriers like in orthogonal frequency division multiplexing [OFDM]} - H04L 25/0248: {Eigen-space methods} - H04L 25/03343: {Arrangements at the transmitter end} - 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 2025/03414: {Multicarrier} - H04L 2025/03426: {transmission using multiple-input and multiple-output channels} - H04L 2025/03802: {Signalling on the reverse channel} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Techniques for transmitting data using channel information for a subset of all subcarriers used for data transmission are described. A transmitter station receives channel information for at least one subcarrier that is a subset of multiple subcarriers used for data transmission. The channel information may include at least one transmit steering matrix, at least one set of eigenvectors, at least one channel response matrix, at least one channel covariance matrix, an unsteered pilot, or a steered pilot for the at least one subcarrier. The transmitter station obtains at least one transmit steering matrix for the at least one subcarrier from the channel information and determines a transmit steering matrix for each of the multiple subcarriers. The transmitter station performs transmit steering or beam-steering for each of the multiple subcarriers with the transmit steering matrix for that subcarrier. ## Claims ### Claim 1 An apparatus comprising: at least one processor configured to receive channel information for at least one subcarrier that is a subset of multiple subcarriers used for data transmission, to obtain transmit steering matrices for the multiple subcarriers based on the channel information for the at least one subcarrier by obtaining at least one transmit steering matrix for the at least one subcarrier based on the channel information and determining a transmit steering matrix for each of the other multiple subcarriers based on the at least one transmit steering matrix by setting the transmit steering matrix for each of the other multiple subcarriers equal to a transmit steering matrix obtained for a closest one of the at least one subcarrier, and to process data for the multiple subcarriers with the transmit steering matrices to send the data from multiple transmit antennas to multiple receive antennas; and a memory coupled to the at least one processor. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the at least one processor is configured to perform transmit steering for each of the multiple subcarriers with the transmit steering matrix determined for the subcarrier. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the channel information comprises at least one transmit steering matrix for the at least one subcarrier. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the channel information comprises at least one eigenvector for each of the at least one subcarrier. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the channel information comprises at least one channel response matrix or at least one channel covariance matrix for the at least one subcarrier. ### Claim 6 (depends on 2) The apparatus of claim 2, wherein the channel information comprises a pilot sent on the at least one subcarrier, and wherein the at least one processor is configured to obtain the at least one transmit steering matrix based on the pilot sent on the at least one subcarrier. ### Claim 7 (depends on 2) The apparatus of claim 2, wherein the channel information comprises a pilot sent on the at least one subcarrier, and wherein the at least one processor is configured to obtain at least one channel response matrix for the at least one subcarrier based on the pilot sent on the at least one subcarrier, and to decompose the at least one channel response matrix to obtain the at least one transmit steering matrix. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the at least one subcarrier is distributed across the multiple subcarriers. ### Claim 9 (depends on 1) The apparatus of claim 1, wherein the at least one subcarrier varies across multiple time intervals. ### Claim 10 A method comprising: receiving channel information for at least one subcarrier that is a subset of multiple subcarriers used for data transmission; obtaining transmit steering matrices for the multiple subcarriers based on the channel information for the at least one subcarrier by obtaining at least one transmit steering matrix for the at least one subcarrier from the channel information and determining a transmit steering matrix for each of the other multiple subcarriers based on the at least one transmit steering matrix by setting the transmit steering matrix for each of the other multiple subcarriers equal to a transmit steering matrix obtained for a closest one of the at least one subcarrier; and processing data for the multiple subcarriers with the transmit steering matrices to send the data from multiple transmit antennas to multiple receive antennas. ### Claim 11 (depends on 10) The method of claim 10, wherein the processing data for the multiple subcarriers comprises: performing transmit steering for each of the multiple subcarriers with the transmit steering matrix determined for the subcarrier. ### Claim 12 An apparatus comprising: means for receiving channel information for at least one subcarrier that is a subset of multiple subcarriers used for data transmission; means for obtaining transmit steering matrices for the multiple subcarriers based on the channel information for the at least one subcarrier by obtaining at least one transmit steering matrix for the at least one subcarrier from the channel information and determining a transmit steering matrix for each of the other multiple subcarriers based on the at least one transmit steering matrix by setting the transmit steering matrix for each of the other multiple subcarriers equal to a transmit steering matrix obtained for a closest one of the at least one subcarrier; and means for processing data for the multiple subcarriers with the transmit steering matrices to send the data from multiple transmit antennas to multiple receive antennas. ### Claim 13 (depends on 12) The apparatus of claim 12, wherein the means for processing data for the multiple subcarriers comprises: means for performing transmit steering for each of the multiple subcarriers with the transmit steering matrix determined for the subcarrier. ### Claim 14 A memory apparatus including instructions stored thereon, comprising: a first instruction set for receiving channel information for at least one subcarrier that is a subset of multiple subcarriers used for data transmission; a second instruction set for obtaining transmit steering matrices for the multiple subcarriers based on the channel information for the at least one subcarrier, by obtaining at least one transmit steering matrix for the at least one subcarrier based on the channel information and determining a transmit steering matrix for each of the other multiple subcarriers based on the at least one transmit steering matrix by setting the transmit steering matrix for each of the other multiple subcarriers equal to a transmit steering matrix obtained for a closest one of the at least one subcarrier; and a third instruction set for processing data for the multiple subcarriers with the transmit steering matrices to send the data from multiple transmit antennas to multiple receive antennas.