# US 8,787,484 B2 · Precoding techniques for downlink coordinated multipoint transmission in radio communications system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,787,484 B2 - Document ID: US8787484B2 - Status: Granted - Kind: B2 - Application number: 13/704,802 - Filed: 2010-06-18 - Published: 2013-04-11 - Granted: 2014-07-22 - Earliest claimed: 2010-06-18 - Assignees: NEC Corporation - Applicants: Le Liu - Inventors: Le Liu - Web page: https://patentgrep.com/patent/US8787484B2 ## CPC - H04B 7/024: Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems - H04B 7/026: Co-operative diversity, e.g. using fixed or mobile stations as relays - H04B 7/0417: Feedback systems - H04B 7/0617: {for beam forming} - H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]} - H04B 7/063: {Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection} - H04B 7/0632: {Channel quality parameters, e.g. channel quality indicator [CQI]} - H04B 7/0634: {Antenna weights or vector/matrix coefficients} - H04B 7/0452: Multi-user MIMO systems - H04B: TRANSMISSION ## Abstract A precoding vector of coordinated multipoint transmission (CoMP) for at least one user equipment is decided by receiving the channel state information for CoMP from the user equipment, wherein the channel state information includes inter-cell correlation property between a serving cell serving the user equipment and a cooperating cell for CoMP; and deciding the precoding vector of CoMP based on the channel state information. ## Claims ### Claim 1 A method for deciding a precoding vector of coordinated multi-point transmission (CoMP) for at least one user equipment in a network, comprising: receiving channel state information for CoMP from the user equipment, wherein the channel state information includes inter-cell correlation property between a serving cell serving the user equipment and a cooperating cell for CoMP, wherein the inter-cell correlation property is represented by a cross-correlation channel matrix which is obtained by correlation between a first transmit channel matrix from the serving cell to the ,equipment and a second transmit channel matrix from the cooperating cell to the user equipment, and wherein a precoding matrix index (PMI) for the serving cell and the cooperating cell is selected by the user equipment with a joint channel matrix and a joint correlation matrix, wherein the joint channel matrix is constructed b the first transmit channel a matrix from the serving cell to the user equipment and the second transmit channel matrix from the cooperating cell to the user equipment; and the joint correlation matrix is constructed by the cross-correlation channel matrix, the first auto-correlation channel of the serving cell and the second auto-correlation channel matrix of the cooperating cell; and deciding the precoding vector of CoMP based on the channel state information. ### Claim 2 (depends on 1) The method according to claim 1, wherein the channel state information further includes first auto-correlation channel property between the serving cell and the user equipment. ### Claim 3 (depends on 2) The method according to claim 2, wherein the network estimates second auto-correlation channel property between the cooperating cell and the user equipment by using the first auto-correlation channel property and the inter-cell correlation property. ### Claim 4 (depends on 2) The method according to claim 2, wherein the channel state information further includes second auto-correlation channel property between the cooperating cell and the user equipment. ### Claim 5 (depends on 1) The method according to claim 1, wherein the user equipment feeds back PMI information and channel matrix information whose term is longer than the PMI information, wherein the channel matrix information includes at least the cross-correlation channel matrix and the auto-correlation channel of the serving cell, wherein the PMI information includes the PMI for the serving cell and the PMI for the cooperating cell. ### Claim 6 (depends on 1) The method according to claim 1, wherein the user equipment feeds back PMI information and channel matrix information whose bandwidth is wider than the PMI information, wherein the channel matrix information includes at least the cross-correlation channel matrix and the auto-correlation channel of the serving cell, wherein the PMI information includes the PMI for the serving cell and the PMI for the cooperating cell. ### Claim 7 A system for deciding a precoding vector of coordinated multipoint transmission (CoMP) for at least one user equipment in a network, comprising: a receiver for receiving channel state information for CoMP from the user equipment, wherein the channel state information includes inter-cell correlation property between a serving cell serving the user equipment and a cooperating cell for CoMP, wherein the inter-cell correlation property is represented by a cross-correlation channel matrix which is obtained by correlation between a first transmit channel matrix from the serving cell to the user equipment and a second transmit channel matrix from the cooperating cell to the user equipment, and wherein a precoding matrix index (PMI) for the serving cell and the cooperating cell is selected by the user equipment with a joint channel matrix and a joint correlation matrix, wherein the joint channel matrix is constructed by the first transmit channel matrix from the serving cell to the user equipment and the second transmit channel matrix from the cooperating cell to the user equipment; and the joint correlation matrix is constructed by the cross-correlation channel matrix, the first auto-correlation channel of the serving cell and the second auto-correlation channel matrix of the cooperating cell; and a scheduler for deciding the precoding vector of CoMP based on the channel state information. ### Claim 8 (depends on 6) The system according to claim 6, wherein the channel state information further includes first auto-correlation channel property between the serving cell and the user equipment. ### Claim 9 (depends on 7) The system according to claim 7, wherein the scheduler estimates second auto-correlation channel property between the cooperating cell and the user equipment by using the first auto-correlation channel property and the inter-cell correlation property. ### Claim 10 (depends on 7) The system according to claim 7, wherein the channel state information further includes second auto-correlation channel property between the cooperating cell and the user equipment. ### Claim 11 (depends on 6) A base station in a cellular network, comprising the system according to claim 6. ### Claim 12 A user equipment in a cellular network, comprising: a channel estimator for generating channel state information for CoMP, wherein the channel state information includes inter-cell correlation property between a serving cell serving the user equipment and a cooperating cell for CoMP, wherein the channel state information further includes second auto-correlation channel property between the cooperating cell and the user equipment, and wherein a precoding matrix index (PMI) for the serving cell and the cooperating cell is selected by using a joint channel and a joint correlation matrix, wherein the joint channel matrix is constructed by the first transmit channel matrix from the serving cell to the user equipment and the second transmit channel matrix from the cooperating cell to the user equipment; and the joint correlation matrix is constructed by the cross-correlation channel matrix, the first auto-correlation channel of the serving cell and the second auto-correlation channel matrix of the cooperating cell; and a transmitter for transmitting the channel state information to the serving cell. ### Claim 13 (depends on 11) The user equipment according to claim 11, wherein the channel state information further includes first auto-correlation channel property between the serving cell and the user equipment. ### Claim 14 (depends on 11) The user equipment according to claim 11, wherein the inter-cell correlation property is represented by a cross-correlation channel matrix which is obtained by correlation between a first transmit channel matrix from the serving cell to the user equipment and a second transmit channel matrix from the cooperating cell to the user equipment. ### Claim 15 (depends on 12) The user equipment according to claim 12, wherein the user equipment feeds back PMI information and channel matrix information whose term is longer than the PMI information, wherein the channel matrix information includes at least the cross-correlation channel matrix and the auto-correlation channel of the serving cell, wherein the PMI information includes the PMI for the serving cell and the PMI for the cooperating cell. ### Claim 16 (depends on 12) The user equipment according to claim 12, wherein the user equipment feeds back PMI information and channel matrix information whose bandwidth is wider than the PMI information, wherein the channel matrix information includes at least the cross-correlation channel matrix and the auto-correlation channel of the serving cell, wherein the PMI information includes the PMI for the serving cell and the PMI for the cooperating cell. ### Claim 17 A feedback method in a user equipment in a cellular network, comprising: generating channel state information for CoMP, wherein the channel state information includes inter-cell correlation property between a serving cell serving the user equipment and a cooperating cell for CoMP, wherein the channel state information further includes second auto-correlation channel property between the cooperating cell and the user equipment, and wherein a precoding matrix index (PMI) for the serving cell and the cooperating cell is selected by using a joint channel matrix and a joint correlation matrix, wherein the joint channel matrix s constructed by the first transmit channel matrix from the serving cell to the user equipment and the second transmit channel matrix from the cooperating cell to the user equipment; and the joint correlation matrix is constructed by the cross-correlation channel matrix, the first auto-correlation chat el of the serving cell and the second auto-correlation channel matrix of the cooperating cell; and transmitting the channel state information to the serving cell. ### Claim 18 A computer-readable program stored in a recording medium, for functioning a program-controlled processor as a system deciding a precoding vector of coordinated multipoint transmission (CoMP) for at least one user equipment in a network, comprising: receiving channel state information for CoMP from the user equipment, wherein the channel state information includes inter-cell correlation property between a serving cell serving the user equipment and a cooperating cell for CoMP, wherein the inter-cell correlation property is represented by a cross-correlation channel matrix which is obtained by correlation between a first transmit channel matrix from the serving cell to the user equipment and a second transmit channel matrix from the cooperating cell to the user equipment, and wherein a precoding matrix index (PMI) for the serving cell and the cooperating cell is selected by the user equipment with a joint channel matrix and a joint correlation matrix, wherein the joint channel matrix is constructed by the first transmit channel matrix from the serving cell to the user equipment and the second transmit channel matrix from the cooperating cell to the user equipment; and the joint correlation matrix is constructed by the cross-correlation channel matrix, the first auto-correlation channel of the serving cell and the second auto-correlation channel matrix of the cooperating cell; and deciding the precoding vector of CoMP based on the channel state information. ### Claim 19 A computer-readable program stored in a recording medium, for functioning a program-controlled processor as a user equipment for transmitting channel state information for CoMP to a network, comprising: generating the channel state information including inter-cell correlation property between a serving cell serving the user equipment and a cooperating cell for CoMP, wherein the channel state information further includes second auto-correlation channel property between the cooperating cell and the user equipment, and wherein a precoding matrix index (PMD) for the serving cell and the cooperating cell is selected by using a joint channel matrix and a joint, correlation matrix, wherein the joint channel matrix is constructed by the first transmit channel matrix from the serving cell to the user equipment and the second transmit channel matrix from the cooperating cell to the user equipment; and the joint correlation a is constructed by the cross-correlation channel matrix, the first auto-correlation channel of the serving cell and the second auto-co elation channel matrix of the cooperating cell; and transmitting the channel state information to the serving cell.