# US 7,609,613 B2 · Cyclic delay diversity and space coded-hybrid diversity transmitter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,613 B2 - Document ID: US7609613B2 - Status: Granted - Kind: B2 - Application number: 11/363,430 - Filed: 2006-02-27 - Published: 2006-08-31 - Granted: 2009-10-27 - Earliest claimed: 2005-02-28 - Assignees: King's College London of Strand - Inventors: Abdol Hamid Aghvami; Mischa Dohler; Fatin Said; Afzal Mahmood Lodhi; Francesco Saverio Ostuni - Web page: https://patentgrep.com/patent/US7609613B2 ## CPC - H04B 7/0671: {using different delays between antennas} - H04L 27/2626: {Arrangements specific to the transmitter only} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A diversity transmitter for use in an OFDM transmission protocol which diversity transmitter comprises: a diversity generator (2) for receiving and diversifying OFDM transmit symbols, and outputting diversified OFDM symbol matrices (DOSM), DOSM symbols within each DOSM being divided into at least two primary streams each comprising different DOSM symbols, a transmit processor for receiving said at least two primary streams of DOSM symbols, and for transforming said each DOSM symbol from the frequency domain into the time domain, and outputting time domain OFDM symbols (TDOSs), a cyclic delay circuit (41 . . . 4P) for dividing at least one of said primary streams of TDOSs into at least two branches of identical TDOSs, each branch for supplying a respective spatial channel for transmission to a receiver, the arrangement being such that, in use, said cyclic delay circuit (41 . . . 4P) applies a cyclic time shift to a TDOS symbol in at least one of said branches before transmission. ## Claims ### Claim 1 A diversity transmitter for use in an OFDM transmission protocol which diversity transmitter comprises: a diversity generator for receiving and diversifying OFDM transmit symbols, and outputting diversified OFDM symbol matrices (DOSM), DOSM symbols within each DOSM being divided into at least two primary streams each comprising different DOSM symbols, a transmit processor for receiving said at least two primary streams of DOSM symbols, and for transforming said each DOSM symbol from the frequency domain into the time domain, and outputting time domain OFDM symbols (TDOSs), a cyclic delay circuit for dividing at least one of said primary streams of TDOSs into at least two branches of identical TDOSs, each branch for supplying a respective spatial channel for transmission to a receiver, the arrangement being such that, in use, said cyclic delay circuit applies a cyclic time shift to a TDOS in at least one of said branches before transmission which cyclic time shift is performed modulo the length of said TDOS and is a multiple of a guard period of said OFDM transmission protocol. ### Claim 2 (depends on 1) A diversity transmitter as claimed in claim 1, wherein said cyclic delay circuit applies no cyclic time shift in at least one of said branches, whereby said diversity transmitter transmits substantially simultaneously from different spatial channels at least the original TDOS and a cyclically delayed replica thereof. ### Claim 3 (depends on 1) A diversity transmitter as claimed in claim 1, wherein there is a plurality of said branches, said cyclic delay circuit applying a different cyclic time shift in each branch. ### Claim 4 (depends on 3) A diversity transmitter as claimed in claim 3, wherein said cyclic time shift differs between branches by an amount sufficient to inhibit overlap between TDOSs transmitted from difference spatial channels. ### Claim 5 (depends on 3) A diversity transmitter as claimed in claim 3, wherein said cyclic time shift is such that the length of cyclic prefix or guard period is not increased. ### Claim 6 (depends on 1) A diversity transmitter as claimed in claim 1, wherein said length is measured in a number of samples of said TDOS, and said cyclic shift is performed by shifting the order of said samples. ### Claim 7 (depends on 1) A diversity transmitter as claimed in claim 1, wherein said cyclic time shift is determined according to system requirements and the number of primary streams. ### Claim 8 (depends on 1) A diversity transmitter as claimed in claim 1, wherein said cyclic time shift is dependent on the number of taps in the channel. ### Claim 9 (depends on 1) A diversity transmitter as claimed in claim 1, wherein said cyclic delay circuit comprises a cyclic delay matrix (Cdm). ### Claim 10 (depends on 9) A diversity transmitter as claimed in claim 9, wherein said cyclic delay matrix (Cdm) is obtainable from: Cd m = [ 0 I ( m - 1 ) ⁢ ( L + 1 ) I N - ( m - 1 ) ⁢ ( L + 1 ) 0 ] , m ∈ [ 1 , M ] where IA is the identity matrix of order A×A, N is the number of sub-carrier frequencies in the OFDM system, M is the number of branches in that cyclic delay circuit where Cdm is to be applied, and L+1 is number of non-zero taps assumed in the channel transfer function. ### Claim 11 (depends on 1) A diversity transmitter as claimed in claim 1, further comprising a cyclic delay circuit per primary stream of TDOSs. ### Claim 12 (depends on 1) A diversity transmitter as claimed in claim 1, wherein at least one of said primary streams bypasses said cyclic delay circuit for supplying a spatial channel substantially directly, while the or each remaining primary stream delivers TDOSs to one or more cyclic delay circuit. ### Claim 13 (depends on 1) A diversity transmitter as claimed in claim 1, wherein said diversified OFDM symbol matrices are generated from a channel coded sequence. ### Claim 14 A method of transmitting data in an OFDM system, which method comprises the steps of: (1) using a diversity generator to receive and diversify OFDM transmit symbols, and output diversified OFDM symbol matrices (DOSM); (2) dividing DOSM symbols within each DOSM into at least two primary streams each comprising different DOSM symbols; (3) transforming each DOSM symbol from the frequency domain into the time domain, and outputting time domain OFDM symbols (TDOSs); (4) dividing at least one of said primary streams of TDOSs into at least two branches of identical TDOSs, each branch for supplying a respective spatial channel for transmission to a receiver; and (5) applying a cyclic time shift to a TDOS in at least one of said branches before transmission which cyclic time shift is performed modulo the length of said TDOS and is a multiple of a guard period of said OFDM transmission protocol. ### Claim 15 (depends on 14) A method according to claim 14, further comprising the step of applying no cyclic time shift in at least one of said branches, and transmitting substantially simultaneously from different spatial channels at least the original TDOS and a cyclically delayed replica thereof. ### Claim 16 (depends on 14) A method according to claim 14, wherein there is a plurality of said branches, the method further comprising the step of applying a different cyclic time shift in each branch. ### Claim 17 (depends on 16) A method according to claim 16, wherein said cyclic time shift differs between branches by an amount sufficient to inhibit overlap between TDOSs transmitted from difference spatial channels. ### Claim 18 (depends on 14) A method according to claim 14, wherein said cyclic time shift is such that the length of cyclic prefix or guard period is not increased. ### Claim 19 (depends on 14) A method according to claim 14, wherein said length is measured in a number of samples of said TDOS, and said cyclic shift is performed by shifting the order of said samples. ### Claim 20 (depends on 14) A method according to claim 14, wherein said cyclic time shift is dependent on the number of channel taps. ### Claim 21 (depends on 14) A method according to claim 14, wherein step (5) comprises the step of applying a cyclic delay matrix (Cdm) to shift said TDOS in time. ### Claim 22 (depends on 21) A method according to claim 21, wherein said cyclic delay matrix (Cdm) is obtainable from: Cd m = [ 0 I ( m - 1 ) ⁢ ( L + 1 ) I N - ( m - 1 ) ⁢ ( L + 1 ) 0 ] , m ∈ [ 1 , M ] where IA is the identity matrix of order A×A, N is the number of sub-carrier frequencies in the OFDM system, M is the number of branches in that cyclic delay circuit where Cdm is to be applied, and L+1 is number of non-zero taps assumed in the channel transfer function. ### Claim 23 (depends on 14) A method according to claim 14, further comprising the step of applying at least one cyclic delay per primary stream of TDOSs. ### Claim 24 (depends on 14) A method according to claim 14, further comprising the step of bypassing symbols in at least one of said primary streams around said cyclic delay circuit to supplying a spatial channel substantially directly, while the or each remaining primary stream delivers TDOSs to one or more cyclic delay circuit. ### Claim 25 A computer readable medium comprising computer executable instructions for causing a diversity transmitter to perform the method steps of: (1) using a diversity generator to receive and diversify OFDM transmit symbols, and output diversified OFDM symbol matrices (DOSM); (2) dividing DOSM symbols within each DOSM into at least two primary streams each comprising different DOSM symbols; (3) transforming each DOSM symbol from the frequency domain into the time domain, and outputting time domain OFDM symbols (TDOSs); (4) dividing at least one of said primary streams of TDOSs into at least two branches of identical TDOSs, each branch for supplying a respective spatial channel for transmission to a receiver; and (5) applying a cyclic time shift to a TDOS in at least one of said branches before transmission, which cyclic time shift is performed modulo the length of said TDOS and is a multiple of a guard period of said OFDM transmission protocol.