# US 10,312,978 B2 · Wireless transceiver station with performs multi-path reciprocity calibration with multiple reference antennas > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,312,978 B2 - Document ID: US10312978B2 - Status: Granted - Kind: B2 - Application number: 16/036,372 - Filed: 2018-07-16 - Published: 2019-01-24 - Granted: 2019-06-04 - Earliest claimed: 2017-07-18 - Assignees: National Instruments Corporation - Applicants: National Instruments Corporation - Inventors: Jörg Hofrichter; Michael Löhning; Eckhard Ohlmer - Web page: https://patentgrep.com/patent/US10312978B2 ## CPC - H04B 7/0417: Feedback systems - H01Q 1/241: {used in mobile communications, e.g. GSM (H01Q1/247, H01Q1/248 take precedence)} - H04B 1/40: Circuits - H04B 17/0085: {using test signal generators} - H04B 17/12: of transmit antennas, e.g. of the amplitude or phase - H04B 17/14: of the whole transmission and reception path, e.g. self-test loop-back - H04L 1/0009: {by adapting the channel coding (H04L1/1812 takes precedence)} - H04B 7/0413: MIMO systems - H04B: TRANSMISSION - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract In a wireless transceiver station having M antennas, designate an antenna as a target reference antenna (TRA) and for each antenna m other than the TRA: define N distinct paths from antenna m to TRA through zero or more intermediate reference antennas, N is two or more, each distinct paths has a distinct associated set of one or more antenna pairs; for each antenna pair of the sets, estimate an effective forward and backward channel response by sending calibration pilots forth and back between the antenna pair and calculate a reciprocity coefficient for the antenna pair using the estimated channel responses; for each of the N distinct paths, calculate a reciprocity coefficient estimate using the reciprocity coefficients calculated for the set of antenna pairs associated with the path; and combine the N calculated reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna). ## Claims ### Claim 1 A wireless transceiver station, comprising: M antennas connected to radio transceivers; and a processor, programmed to: designate an antenna of the M antennas as a target reference antenna; and for each antenna m of the M antennas other than the target reference antenna: define N distinct paths from the antenna m to the target reference antenna through zero or more intermediate reference antennas of the M antennas, wherein N for the antenna m is two or more; wherein each of the N distinct paths has a distinct associated set of one or more antenna pairs of the M antennas; for each antenna pair of the sets of antenna pairs: estimate an effective forward and backward channel response by sending calibration pilots forth and back between the antenna pair; and calculate a reciprocity coefficient for the antenna pair using the estimated channel responses; for each path of the N distinct paths: calculate a reciprocity coefficient estimate using the reciprocity coefficients calculated for the set of antenna pairs associated with the path; and combine the N calculated reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna). ### Claim 2 (depends on 1) The wireless transceiver station of claim 1, wherein to combine the N calculated reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna), the processor is further programmed to: for each of the N calculated reciprocity coefficient estimates: calculate a respective weight; and calculate a sum of N products of the N calculated reciprocity coefficient estimates and their respective weights to produce the final reciprocity coefficient estimate. ### Claim 3 (depends on 1) The wireless transceiver station of claim 1, wherein the wireless transceiver station is programmed to transmit and receive on multiple subcarriers; wherein to estimate an effective forward and backward channel response by sending calibration pilots forth and back between the antenna pair, the wireless transceiver station is programmed to: estimate an effective forward and backward channel response for a plurality of the multiple subcarriers by sending calibration pilots forth and back between the antenna pair on each of the plurality of the subcarriers; and wherein to calculate a reciprocity coefficient for the antenna pair using the estimated channel responses, the wireless transceiver station is programmed to: calculate a reciprocity coefficient for the antenna pair for each of the plurality of subcarriers using the effective forward and backward channel responses estimated for each of the plurality of subcarriers. ### Claim 4 (depends on 3) The wireless transceiver station of claim 3, wherein to calculate a reciprocity coefficient for the antenna pair using the estimated channel responses, the wireless transceiver station is further programmed to: average the calculated reciprocity coefficients over the plurality of subcarriers to obtain a mean reciprocity coefficient estimate for the antenna pair, which is the calculated reciprocity coefficient for the antenna pair. ### Claim 5 (depends on 4) The wireless transceiver station of claim 4, wherein to calculate a reciprocity coefficient estimate using the reciprocity coefficients calculated for the set of antenna pairs associated with the path, the wireless transceiver station is programmed to: calculate the reciprocity coefficient estimate using the obtained mean reciprocity coefficient estimates for the set of antenna pairs associated with the path. ### Claim 6 A wireless transceiver station, comprising: M antennas connected to radio transceivers; and a processor, programmed to: designate an antenna of the M antennas as a target reference antenna; designate a subset of R antennas of the M antennas as reference antennas, where the target reference antenna is included in the subset, where R is at least two; for each antenna m of the M antennas other than the target reference antenna: define N distinct paths from the antenna m to the target reference antenna through zero or more of P distinct pairs of antennas (rr, rl) of the subset of R reference antennas, where P is at least one, where N for the antenna m is two or more; for at least each antenna pair (m, r) included in the N distinct paths for the M antennas: estimate an effective forward and backward channel response by sending calibration pilots forth and back between the antenna pair (m, r); and calculate a single-hop reciprocity coefficient estimate for the antenna pair (m, r) using the estimated effective forward and backward channel responses for the antenna pair (m, r); for each antenna pair (rr, rl) of the P distinct pairs of antennas (rr, rl) of the subset of R reference antennas: calculate one or more dual-hop reciprocity coefficient estimates for the antenna pair (rr, rl) through respective one or more antennas of the M antennas, where each respective antenna is distinct from rr and rl; and combine the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl) to generate a combined reciprocity calibration coefficient estimate for the antenna pair (rr, rl); and for each antenna m of the M antennas: for each path of the N distinct paths for the antenna m, calculate a respective reciprocity coefficient estimate using: the combined reciprocity calibration coefficient estimates for each of the antenna pairs (rr, rl) included in the path; and the single-hop reciprocity coefficient estimate for the antenna pair (m, r), where antenna r is one of the antennas in antenna pair (rr, rl) included in the path; and combine the N respective reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna). ### Claim 7 (depends on 6) The wireless transceiver station of claim 6, wherein the wireless transceiver station is programmed to transmit and receive on multiple subcarriers; and wherein to calculate a single-hop reciprocity coefficient estimate for the antenna pair (m, r) using the estimated effective forward and backward channel responses for the antenna pair (m, r), the wireless transceiver station is programmed to: estimate an effective forward and backward channel response for a plurality of the multiple subcarriers by sending calibration pilots forth and back between the antenna m and the antenna r on each of the plurality of subcarriers; calculate a reciprocity coefficient for the antenna pair (m, r) for each of the plurality of subcarriers using the effective forward and backward channel responses estimated for each of the plurality of subcarriers; and average the calculated reciprocity coefficients of the antenna pair (m, r) over the plurality of subcarriers to obtain the single-hop reciprocity coefficient estimate for the antenna pair (m, r). ### Claim 8 (depends on 6) The wireless transceiver station of claim 6, wherein to combine the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl) to generate a combined reciprocity calibration coefficient estimate for the antenna pair (rr, rl), the wireless transceiver station is programmed to: for each of the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl): calculate a respective weight; and calculate a sum of products of the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl) and their respective weights to produce the combined reciprocity calibration coefficient estimate for the antenna pair (rr, rl). ### Claim 9 A method, comprising: designating an antenna of M antennas of a wireless transceiver station as a target reference antenna; and for each antenna m of the M antennas other than the target reference antenna: defining N distinct paths from the antenna m to the target reference antenna through zero or more intermediate reference antennas of the M antennas, wherein N for the antenna m is two or more; wherein each of the N distinct paths has a distinct associated set of one or more antenna pairs of the M antennas; for each antenna pair of the sets of antenna pairs: estimating an effective forward and backward channel response by sending calibration pilots forth and back between the antenna pair; and calculating a reciprocity coefficient for the antenna pair using the estimated channel responses; for each path of the N distinct paths: calculating a reciprocity coefficient estimate using the reciprocity coefficients calculated for the set of antenna pairs associated with the path; and combining the N calculated reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna). ### Claim 10 (depends on 9) The method of claim 9, wherein said combining the N calculated reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna) comprises: for each of the N calculated reciprocity coefficient estimates: calculating a respective weight; and calculating a sum of N products of the N calculated reciprocity coefficient estimates and their respective weights to produce the final reciprocity coefficient estimate. ### Claim 11 (depends on 10) The method of claim 10, wherein said calculating a respective weight comprises: using estimated variances of the reciprocity coefficient estimates to calculate the respective weight. ### Claim 12 (depends on 11) The method of claim 11, wherein said using estimated variances of the reciprocity coefficient estimates to calculate the respective weight comprises: calculating a ratio of a reciprocal of the estimated variance of the respective reciprocity coefficient estimate and a sum of reciprocals of the estimated variances of the N calculated reciprocity coefficient estimates. ### Claim 13 (depends on 9) The method of claim 9, wherein said combining the N calculated reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna) comprises: selecting one of the N calculated reciprocity coefficient estimates having minimum variance from among the N calculated reciprocity coefficient estimates. ### Claim 14 (depends on 9) The method of claim 9, wherein said combining the N calculated reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna) comprises: averaging the N calculated reciprocity coefficient estimates. ### Claim 15 (depends on 9) The method of claim 9, wherein the wireless transceiver station is programmed to transmit and receive on multiple subcarriers; wherein said estimating an effective forward and backward channel response by sending calibration pilots forth and back between the antenna pair comprises: estimating an effective forward and backward channel response for a plurality of the multiple subcarriers by sending calibration pilots forth and back between the antenna pair on each of the plurality of the subcarriers; and wherein said calculating a reciprocity coefficient for the antenna pair using the estimated channel responses comprises: calculating a reciprocity coefficient for the antenna pair for each of the plurality of subcarriers using the effective forward and backward channel responses estimated for each of the plurality of subcarriers. ### Claim 16 (depends on 15) The method of claim 15, wherein said calculating a reciprocity coefficient for the antenna pair using the estimated channel responses further comprises: averaging the calculated reciprocity coefficients over the plurality of subcarriers to obtain a mean reciprocity coefficient estimate for the antenna pair, which is the calculated reciprocity coefficient for the antenna pair. ### Claim 17 (depends on 16) The method of claim 16, wherein said calculating a reciprocity coefficient estimate using the reciprocity coefficients calculated for the set of antenna pairs associated with the path comprises: calculating the reciprocity coefficient estimate using the obtained mean reciprocity coefficient estimates for the set of antenna pairs associated with the path. ### Claim 18 A method, comprising: designating one antenna of the M antennas as a target reference antenna; designating a subset of R antennas of the M antennas as reference antennas, where the target reference antenna is included in the subset, where R is at least two; for each antenna m of the M antennas other than the target reference antenna: defining N distinct paths from the antenna m to the target reference antenna through zero or more of P distinct pairs of antennas (rr, rl) of the subset of R reference antennas, where P is at least one, where N for the antenna m is two or more; for at least each antenna pair (m, r) included in the N distinct paths for the M antennas: estimating an effective forward and backward channel response by sending calibration pilots forth and back between the antenna pair (m, r); and calculating a single-hop reciprocity coefficient estimate for the antenna pair (m, r) using the estimated effective forward and backward channel responses for the antenna pair (m, r); for each antenna pair (rr, rl) of the P distinct pairs of antennas (rr, rl) of the subset of R reference antennas: calculating one or more dual-hop reciprocity coefficient estimates for the antenna pair (rr, rl) through respective one or more antennas of the M antennas, where each respective antenna is distinct from rr and rl; and combining the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl) to generate a combined reciprocity calibration coefficient estimate for the antenna pair (rr, rl); and for each antenna m of the M antennas: for each path of the N distinct paths for the antenna m, calculating a respective reciprocity coefficient estimate using: the combined reciprocity calibration coefficient estimates for each of the antenna pairs (rr, rl) included in the path; and the single-hop reciprocity coefficient estimate for the antenna pair (m, r), where antenna r is one of the antennas in antenna pair (rr, rl) included in the path; and combining the N respective reciprocity coefficient estimates to produce a final reciprocity coefficient estimate for antenna pair (m, target reference antenna). ### Claim 19 (depends on 18) The method of claim 18, wherein the wireless transceiver station is programmed to transmit and receive on multiple subcarriers; and wherein said calculating a single-hop reciprocity coefficient estimate for the antenna pair (m, r) using the estimated effective forward and backward channel responses for the antenna pair (m, r) comprises: estimating an effective forward and backward channel response for a plurality of the multiple subcarriers by sending calibration pilots forth and back between the antenna m and the antenna r on each of the plurality of subcarriers; calculating a reciprocity coefficient for the antenna pair (m, r) for each of the plurality of subcarriers using the effective forward and backward channel responses estimated for each of the plurality of subcarriers; and averaging the calculated reciprocity coefficients of the antenna pair (m, r) over the plurality of subcarriers to obtain the single-hop reciprocity coefficient estimate for the antenna pair (m, r). ### Claim 20 (depends on 18) The method of claim 18, wherein said combining the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl) to generate a combined reciprocity calibration coefficient estimate for the antenna pair (rr, rl) comprises: for each of the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl): calculating a respective weight; and calculating a sum of products of the single-hop reciprocity calibration coefficient estimate for the antenna pair (rr, rl) and the one or more dual-hop reciprocity calibration coefficient estimates for the antenna pair (rr, rl) and their respective weights to produce the combined reciprocity calibration coefficient estimate for the antenna pair (rr, rl).