# US 8,787,481 B2 · Method and arrangement for adapting a multi-antenna transmission > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,481 B2 - Document ID: US8787481B2 - Status: Granted - Kind: B2 - Application number: 13/632,904 - Filed: 2012-10-01 - Published: 2013-01-31 - Granted: 2014-07-22 - Earliest claimed: 2007-04-30 - Assignees: Telefonaktiebolaget L M Ericsson (publ) - Applicants: George Jöngren - Inventors: George Jöngren - Web page: https://patentgrep.com/patent/US8787481B2 ## CPC - H04W 24/02: Arrangements for optimising operational condition - H04B 1/707: using direct sequence modulation - H04B 7/0413: MIMO systems - H04B 7/0417: Feedback systems - H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting - H04B 7/0465: {taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account} - H04B 7/0469: {taking special antenna structures, e.g. cross polarized antennas into account} - H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection} - H04B 7/0697: {using spatial multiplexing} - H04J 11/00: Orthogonal multiplex systems, {e.g. using WALSH codes}(H04J13/00 takes precedence) - H04L 25/03343: {Arrangements at the transmitter end} - H04W 72/0446: Resources in time domain, e.g. slots or frames - H04B 7/10: Polarisation diversity; Directional diversity - H04L 2025/03426: {transmission using multiple-input and multiple-output channels} - H04W 88/02: Terminal devices - H04W 88/08: Access point devices - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H04B: TRANSMISSION - H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method in a first node for adapting a multi-antenna transmission to a second node over a wireless channel is provided. The wireless channel has at least three inputs and at least one output. The first node and the second node are comprised in a wireless communication system. The method includes obtaining at least one symbol stream, determining a precoding matrix having a product structure created by a block diagonal matrix being multiplied from the left with a block diagonalizing unitary matrix, precoding the at least one symbol stream with the determined precoding matrix, and transmitting the precoded at least one symbol stream over a wireless channel to the second node. ## Claims ### Claim 1 A method in a first node for adapting a multi-antenna transmission to a second node over a wireless channel, the wireless channel having at least three inputs and at least one output, the first node and the second node being included in a wireless communication system, the method comprising the steps of: obtaining at least one symbol stream; determining a precoding matrix having a product structure created by a block diagonal matrix being multiplied from the left with a block diagonalizing unitary matrix; precoding the at least one symbol stream with the determined precoding matrix; and transmitting the precoded at least one symbol stream over a wireless channel to the second node. ### Claim 2 (depends on 1) The method of claim 1, wherein said block diagonalizing unitary matrix is a 45 degree block diagonalizing unitary matrix. ### Claim 3 (depends on 1) The method of claim 1, wherein the step of determining a precoding matrix is performed by selecting the precoding matrix having a product structure from a precoding codebook comprising precoding elements, wherein at least half of the precoding elements in the precoding codebook have said product structure. ### Claim 4 (depends on 1) The method of claim 1, wherein the block diagonalizing unitary matrix is equivalent to [ 1 0 1 0 0 1 0 1 1 0 - 1 0 0 1 0 - 1 ] ⁢ . ### Claim 5 (depends on 1) The method of claim 1, wherein the block diagonalizing unitary matrix is equivalent to ⁢ [ exp ⁡ ( jπ / 4 ) 0 exp ⁡ ( - jπ / 4 ) 0 0 exp ⁡ ( jπ / 4 ) 0 exp ⁡ ( - jπ / 4 ) exp ⁡ ( jπ / 4 ) 0 - exp ⁡ ( - jπ / 4 ) 0 0 exp ⁡ ( jπ / 4 ) 0 - exp ⁡ ( - jπ / 4 ) ] . ### Claim 6 (depends on 1) The method of claim 1, further comprising the step of receiving channel information from the second node, and wherein the step of determining the precoding matrix is performed based on the channel information received from the second node. ### Claim 7 (depends on 6) The method of claim 6, wherein said received channel information comprises a precoding matrix that the second node recommends the first node to use for the step of precoding. ### Claim 8 (depends on 6) The method of claim 6, wherein said received channel information comprises a channel estimate. ### Claim 9 (depends on 1) The method of claim 1, wherein the step of determining the precoding matrix is performed by at least one of: basing the determination on measurements on a reverse link; and basing the determination on exploiting channel reciprocity properties. ### Claim 10 (depends on 1) The method of claim 1, wherein the transmission of the precoded at least one symbol stream in the first node is conducted using a multi-antenna system with a cross-polarized antenna set-up. ### Claim 11 A method in a second node for receiving a multi-antenna transmission from a first node over a wireless channel, the wireless channel having at least three inputs and at least one output, the first node and the second node being included in a wireless communication system, the method comprising the step of: receiving a transmission corresponding to at least one symbol stream over a wireless channel conveyed from the first node, which at least one symbol stream is precoded with a precoding matrix having a product structure created by a block diagonal matrix being multiplied from the left with a block diagonalizing unitary matrix. ### Claim 12 (depends on 11) The method of claim 11, wherein said block diagonalizing unitary matrix is a 45 degree block diagonalizing unitary matrix. ### Claim 13 (depends on 11) The method of claim 11, wherein said precoding matrix is included in a precoding codebook of finite size wherein at least half of the precoding elements in the precoding codebook have said product structure. ### Claim 14 (depends on 11) The method of claim 11, wherein the block diagonalizing unitary matrix is equivalent to [ 1 0 1 0 0 1 0 1 1 0 - 1 0 0 1 0 - 1 ] ⁢ . ### Claim 15 (depends on 11) The method of claim 11, wherein the block diagonalizing unitary matrix is equivalent to ⁢ [ exp ⁡ ( jπ / 4 ) 0 exp ⁡ ( - jπ / 4 ) 0 0 exp ⁡ ( jπ / 4 ) 0 exp ⁡ ( - jπ / 4 ) exp ⁡ ( jπ / 4 ) 0 - exp ⁡ ( - jπ / 4 ) 0 0 exp ⁡ ( jπ / 4 ) 0 - exp ⁡ ( - jπ / 4 ) ] . ### Claim 16 (depends on 11) The method of claim 11, further comprising the step of conveying channel information to the first node, which channel information is used by the first node as base for determining the precoding matrix with which the received at least one symbol stream is precoded. ### Claim 17 (depends on 16) The method of claim 16, further comprising the step of selecting the precoding matrix to be recommended to be used by the first node for precoding said transmission, wherein said conveyed channel information in the step of conveying the channel information to the first node, is represented by the recommended precoding matrix. ### Claim 18 (depends on 17) The method of claim 17, wherein the precoding codebook is included in the second node, and wherein the recommended precoding matrix is selected from said precoding codebook. ### Claim 19 (depends on 16) The method of claim 16, wherein said conveyed channel information comprises a channel estimate. ### Claim 20 (depends on 11) The method of claim 11, wherein the reception of said transmission of the precoded at least one symbol stream is performed by using a multi-antenna system with a cross-polarized antenna setup. ### Claim 21 An arrangement in a first node, for adapting a multi-antenna transmission to a second node over a wireless channel, the wireless channel having at least three inputs and at least one output, the first node and the second node being included in a wireless communication system, the first node arrangement comprising: an obtaining unit configured to obtain at least one symbol stream; a determining unit configured to determine a precoding matrix having a product structure created by a block diagonal matrix being multiplied from the left with a block diagonalizing unitary matrix; a precoding unit configured to precode the at least one symbol stream with the determined precoding matrix; and a transmitting unit configured to transmit the precoded at least one symbol stream over a wireless channel to the second node. ### Claim 22 An arrangement in a second node, for receiving a multi-antenna transmission from a first node over a wireless channel, the wireless channel having at least three inputs and at least one output, the first node and the second node being comprised in a wireless communication system, the second node arrangement comprising a receiving unit configured to receive a transmission corresponding to at least one symbol stream over a wireless channel conveyed from the first node, which at least one symbol stream is precoded with a precoding matrix having a product structure created by a block diagonal matrix being multiplied from the left with a block diagonalizing unitary matrix.