# US 12,119,899 B2 · Downlink symbol-level precoding as part of multiuser MISO communication > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,119,899 B2 - Document ID: US12119899B2 - Status: Granted - Kind: B2 - Application number: 18/022,790 - Filed: 2020-09-16 - Published: 2023-11-09 - Granted: 2024-10-15 - Earliest claimed: 2020-09-16 - Assignees: Telefonaktiebolaget LM Ericsson (publ) - Applicants: Telefonaktiebolaget LM Ericsson (publ) - Inventors: Maha Alodeh - Web page: https://patentgrep.com/patent/US12119899B2 ## CPC - H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting - H04B 7/0452: Multi-user MIMO systems - H04L 27/36: Modulator circuits; Transmitter circuits - Y02D 30/70: in wireless communication networks - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE ## Abstract There is provided mechanisms for downlink symbol-level precoding as part of multiuser MISO communication. A method is performed by a network node. The method comprises obtaining a data vector of a current time instant to be precoded. The data vector comprises data symbols for 1 users. The current time instant corresponds to a single symbol. The method comprises precoding the obtained data vector by determining an output vector for the data vector of the current time instant. Determining the output vector for the current time instant comprises searching for a data vector of a previous time instant that is co-linear with the data vector of the current time instant according to a co-linearity factor. When such a data vector of the previous time instant is found, the output vector is equal to an output vector of the previous time instant multiplied with the co-linearity factor. ## Claims ### Claim 1 A method for downlink symbol-level precoding as part of multiuser multiple-input single-output, MISO, communication, the method being performed by a network node, the method comprising: obtaining a data vector, d[n], of a current time instant, n, to be precoded, wherein the data vector comprises data symbols, d1[n], . . . , dK [n], for K>1 users, and wherein the current time instant corresponds to a single symbol; and precoding the obtained data vector by determining an output vector, x[n], for the data vector of the current time instant n, wherein, determining the output vector for the current time instant comprises searching for a data vector d[m] of a previous time instant, m, that is co-linear with the data vector of the current time instant according to a co-linearity factor, and when such a data vector of the previous time instant is found, the output vector is equal to an output vector x[m] of the previous time instant multiplied with the co-linearity factor. ### Claim 2 (depends on 1) The method according to claim 1, further comprising: transmitting the output vector of the current time instant in the downlink. ### Claim 3 (depends on 1) The method according to claim 1, wherein the data vector of the previous time instant is co-linear with the data vector of the current time instant when the data vector of the current time instant is equal to the co-linearity factor, z, multiplied with the data vector of the previous time instant. ### Claim 4 (depends on 1) The method according to claim 1, wherein the co-linearity factor takes a value in a set Z={1, −1, i, −i}. ### Claim 5 (depends on 1) The method according to claim 1, wherein the data vector of the previous time instant is searched for among data vectors in a look-up table. ### Claim 6 (depends on 5) The method according to claim 5, wherein the output vectors are, together with their respective data vectors, added to the look-up table upon having been determined through an optimization procedure. ### Claim 7 (depends on 6) The method according to claim 6, wherein the optimization procedure takes as input: the data vector of the current time instant, a set of candidate output vectors, channel state information per user for the current time instant, a signal to noise ratio target per user for the current time instant, and a modulation allocation per user for the current time instant. ### Claim 8 (depends on 6) The method according to claim 6, wherein the optimization procedure is constrained by in which constellation region the output vector is to be received. ### Claim 9 (depends on 6) The method according to claim 6, wherein the optimization procedure involves determining constellation rotation, δ, per user for the current time instant. ### Claim 10 (depends on 6) The method according to claim 6, wherein the optimization procedure is performed only for a reduced subset of all possible data vectors, yielding output vectors only for the reduced subset of all possible data vectors. ### Claim 11 (depends on 10) The method according to claim 10, wherein the output vectors for all possible data vectors are found by being co-linear with the output vectors for the reduced subset of all possible data vectors. ### Claim 12 (depends on 6) The method according to claim 6, wherein the optimization procedure is performed as the data vectors are precoded when any data vector of a previous time instant that is co-linear with the data vector of the current time instant cannot be found when the data vector of the current time instant is to be precoded. ### Claim 13 (depends on 12) The method according to claim 12, wherein the output vector of the current time instant is determined through the optimization procedure. ### Claim 14 (depends on 6) The method according to claim 6, wherein the optimization procedure is performed before any data vectors are precoded, and wherein when a data vector of a previous time instant that is co-linear with the data vector of the current time instant always can be found when the data vector of the current time instant is to be precoded. ### Claim 15 A network node for downlink symbol-level precoding as part of multiuser MISO communication, the network node comprising processing circuitry, the processing circuitry being configured to cause the network node to: obtain a data vector, d[n], of a current time instant, n, to be precoded, wherein the data vector comprises data symbols, d1[n], . . . , dK[n], for K>1 users, and wherein the current time instant corresponds to a single symbol; and precode the obtained data vector by determining an output vector, x[n], for the data vector of the current time instant n, wherein, determining the output vector for the current time instant comprises searching for a data vector d[m] of a previous time instant, m, that is co-linear with the data vector of the current time instant according to a co-linearity factor, and when such a data vector of the previous time instant is found, the output vector is equal to an output vector x[m] of the previous time instant multiplied with the co-linearity factor. ### Claim 16 (depends on 15) The network node according to claim 15, further being configured to: transmit the output vector of the current time instant in the downlink, wherein the data vector of the previous time instant is co-linear with the data vector of the current time instant when the data vector of the current time instant is equal to the co-linearity factor, ξ, multiplied with the data vector of the previous time instant. ### Claim 17 A computer program product for downlink symbol-level precoding as part of multiuser MISO communication, the computer program product comprising a non-transitory computer readable storage medium storing computer code which, when run on processing circuitry of a network node, causes the network node to: obtain a data vector, d[n], of a current time instant, n, to be precoded, wherein the data vector comprises data symbols, d1[n], . . . , dK[n], for K>1 users, and wherein the current time instant corresponds to a single symbol; and precode the obtained data vector by determining an output vector, x[n], for the data vector of the current time instant n, wherein, determining the output vector for the current time instant comprises searching for a data vector d[m] of a previous time instant, m, that is co-linear with the data vector of the current time instant according to a co-linearity factor, and when such a data vector of the previous time instant is found, the output vector is equal to an output vector x[m] of the previous time instant multiplied with the co-linearity factor.