# US 8,570,933 B2 · Self-interference suppression in full-duplex MIMO relays > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,933 B2 - Document ID: US8570933B2 - Status: Granted - Kind: B2 - Application number: 13/288,475 - Filed: 2011-11-03 - Published: 2012-05-03 - Granted: 2013-10-29 - Earliest claimed: 2010-11-03 - Assignees: Telefonaktiebolaget L M Ericsson (publ) - Applicants: Panagiota Lioliou; Mats Viberg; Mikael Coldrey - Inventors: Panagiota Lioliou; Mats Viberg; Mikael Coldrey - Web page: https://patentgrep.com/patent/US8570933B2 ## CPC - H04B 7/15564: {Relay station antennae loop interference reduction} - H04B 7/15528: {Control of operation parameters of a relay station to exploit the physical medium} - H04B: TRANSMISSION ## Abstract A method, and an apparatus, for self-interference suppression in a relay for wireless communication, wherein the relay is arranged for receiving a signal r(n) transmitted from a transmitter, and for transmitting a self-interference suppressed transmit signal xr(n) to a receiver. The self-interference suppressed transmit signal xr(n) is achieved by determining a receive suppression filter matrix Wr, determining a relay amplification matrix G, and determining a transmit suppression filter matrix Wt, and then applying the suppression filters and the amplification matrix to the received signal r(n). ## Claims ### Claim 1 A method for self-interference suppression in a relay for wireless communication, wherein said relay is a part of a communication channel between a transmitter and a receiver in a wireless communication system, said relay being arranged for receiving a signal r(n) transmitted from said transmitter, and transmitting a self-interference suppressed transmit signal xr(n) to said receiver, said communication channel having a transmit channel, defined by a transmit channel matrix (H1) between said transmitter and said relay, a receive channel, defined by a receive channel matrix (H2) between said relay and said receiver, and a self-interference channel between an relay output and a relay input of said relay, the self-interference channel being defined by a self-interference channel matrix (H0), the method comprising: receiving at the relay input of said relay a receive signal r(n) transmitted from said transmitter over said transmit channel; determining a receive suppression filter matrix Wr, in said relay, based on said transmit channel matrix (H1) and said self-interference channel matrix (H0); determining a transmit suppression filter matrix Wt, in said relay, based on said receive suppression filter matrix Wr, said receive channel matrix (H2), and said self-interference channel matrix (H0); determining a self-interference suppressed transmit signal xr(n) by applying said receive suppression filter matrix Wr, a relay amplification matrix G and said transmit suppression filter matrix Wt, to said received signal r(n); and transmitting said self-interference suppressed transmit signal xr(n) from said relay over said receive channel to said receiver. ### Claim 2 (depends on 1) The method according to claim 1, wherein said receive signal r(n) is given by r(n)=H1xs(n)+H0xr(n)+nR(n) wherein xr(n) is the transmitted relay signal, and nR(n) is the noise contribution at the relay. ### Claim 3 (depends on 1) The method according to claim 1, wherein said receive suppression filter matrix Wr is determined by the optimal receive suppression matrix which is given by Wr,opt=UH(H0H0H)−1/2 wherein the columns of U are the corresponding generalized eigenvectors of the matrix (H0H0H)−1/2H1H1H(H0H0H)−1/2. ### Claim 4 (depends on 1) The method according to claim 1, wherein said transmit suppression filter matrix Wt is determined by the optimal transmit suppression matrix which is given by Wt,opt=({tilde over (H)}0H{tilde over (H)}0)−1/2Ū wherein {tilde over (H)}0=Wr,optH0 and matrix Ū is obtained by applying a generalized eigenvalue decomposition of the matrix ({tilde over (H)}0H{tilde over (H)}0)−1/2H2HH2({tilde over (H)}0H{tilde over (H)}0)−1/2, wherein the columns of matrix Ū are the corresponding eigenvectors. ### Claim 5 (depends on 1) The method according to claim 1, wherein said determining of said self-interference suppressed transmit signal xr(n) is done according to xr=WtGWrr(n). ### Claim 6 A relay adapted for self-interference suppression in a wireless communication system, wherein said relay is configured to be a part of a communication channel between a transmitter and a receiver in a wireless communication system, said communication channel having a transmit channel, defined by a transmit channel matrix (H1), between said transmitter and said relay, a receive channel, defined by a receive channel matrix (H2), between said relay and said receiver, and a self-interference channel between a relay output and a relay input of said relay, the self-interference channel being defined by a self-interference channel matrix (H0), said relay comprising: a receiver unit adapted to receive a receive signal r(n) transmitted from said transmitter over said transmit channel; a first processing unit adapted to determine a receive suppression filter matrix Wr, based on said transmit channel matrix (H1) and said self-interference channel matrix (H0); a second processing unit adapted to determine a transmit suppression filter matrix Wt, based on said receive suppression filter matrix Wr, said receive channel matrix (H2), and said self-interference channel matrix (H0); a third processing unit adapted to determine a relay amplification matrix G; and a fourth processing unit adapted to produce a self-interference suppressed transmit signal xr(n) by applying said receive suppression filter matrix Wr from said first processing unit, said transmit suppression filter matrix Wt from said second processing unit, and said relay amplification matrix G from said third processing unit to said receive signal r(n), wherein said fourth processing unit is further adapted to supply said self-interference suppressed transmit signal xr(n) to a transmitter unit; wherein said transmitter unit is adapted to receive said self-interference suppressed transmit signal xr(n) from said fourth processing unit, and adapted to transmit said self-interference suppressed transmit signal xr(n) to said receiver over said transmit channel. ### Claim 7 (depends on 6) The relay according to claim 6, wherein said receive signal r(n) received by said receiver is given by r(n)=H1xs(n)+H0xr(n)+nR(n) wherein xr(n) is the transmitted relay signal, and nR(n) is the noise contribution at the relay. ### Claim 8 (depends on 6) The relay according to claim 6, wherein said first processing unit is further adapted to determine said receive suppression filter matrix Wr by determining the optimal receive suppression matrix according to Wr,opt=UH(H0H0H)−1/2 wherein the columns of U are the corresponding generalized eigenvectors of the matrix (H0H0H)−1/2H1H1H(H0H0H)−1/2. ### Claim 9 (depends on 6) The relay according to claim 6, wherein said second processing unit is further adapted to determine said transmit suppression filter matrix Wt by calculating the optimal transmit suppression matrix according to Wt,opt=({tilde over (H)}0H{tilde over (H)}0)−1/2Ū wherein {tilde over (H)}0=Wr,optH0 and the matrix Ū is obtained by the generalized eigenvalue decomposition of the matrix ({tilde over (H)}0H{tilde over (H)}0)−1/2H2HH2({tilde over (H)}0H{tilde over (H)}0)−1/2, and its columns are the corresponding eigenvectors. ### Claim 10 (depends on 6) The relay according to claim 6, wherein said producing, in said fourth processing unit, of said self-interference suppressed transmit signal xr(n) is done according to xr=WtGWrr(n).