# US 10,771,120 B2 · Base station front end preprocessing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,771,120 B2 - Document ID: US10771120B2 - Status: Granted - Kind: B2 - Application number: 15/074,951 - Filed: 2016-03-18 - Published: 2016-10-27 - Granted: 2020-09-08 - Earliest claimed: 2015-04-27 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Guangjie Li; Wenting Chang; Yushu Zhang - Web page: https://patentgrep.com/patent/US10771120B2 ## CPC - H04B 7/0413: MIMO systems - H04B 7/022: Site diversity; Macro-diversity (using two or more spaced independent antennas H04B7/04) - H04B 7/0452: Multi-user MIMO systems - H04L 25/0228: {with direct estimation from sounding signals} - H04L 25/03343: {Arrangements at the transmitter end} - H04L 25/03891: {Spatial equalizers (MIMO diversity systems H04B7/0413)} - H04B: TRANSMISSION - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract Embodiments of the present disclosure describe systems, devices, and methods for preprocessing in a base station of a multiple-input multiple-output (MIMO) wireless system. In embodiments, remote radio unit (RRU) circuitry may control radio communication related to the MIMO wireless system, including applying a user equipment (UE)-specific spatial filter. ## Claims ### Claim 1 A base station, comprising: remote radio unit (RRU) circuitry to control radio communication related to multiple-input multiple-output (MIMO) operation, including application of a user equipment (UE)-specific spatial filter, wherein the RRU circuitry includes a downlink (DL) user equipment (UE)-specific precoder to facilitate DL beamforming by the base station; and baseband unit (BBU) circuitry coupled with the RRU circuitry to control baseband operation related to the MIMO operation. ### Claim 2 (depends on 1) The base station of claim 1, wherein operation of the DL UE-specific precoder includes application of a UE-specific conjugate channel. ### Claim 3 (depends on 1) The base station of claim 1, wherein the BBU circuitry is further to determine a UE-specific conjugate channel related to the UE-specific spatial filter and to transmit the UE-specific conjugate channel to the RRU circuitry. ### Claim 4 (depends on 1) The base station of claim 1, wherein the RRU circuitry is further to apply the UE-specific spatial filter to an uplink (UL) data channel. ### Claim 5 (depends on 4) The base station of claim 4, wherein the UL data channel includes a physical uplink shared channel (PUSCH). ### Claim 6 (depends on 1) The base station of claim 1, wherein the RRU circuitry is further to: receive a UL sounding reference signal (SRS); and estimate the DE-specific spatial filter based on the SRS. ### Claim 7 (depends on 6) The base station of claim 6, wherein the estimate of the UE-specific spatial filter includes a conjugate channel of the UE. ### Claim 8 (depends on 1) The base station of claim 1, wherein the eNB is to implement a MIMO wireless system having at least twenty antennas. ### Claim 9 One or more non-transitory, computer-readable media having instructions stored thereon, wherein the instructions, in response to execution by a device, cause the device to: apply downlink (DL) user equipment (UE)-specific precoding in remote radio unit (RRU) circuitry to control radio communication in DL beamforming related to a multiple input, multiple output (MIMO) system having at least twenty antennas; and apply UE-specific spatial filtering in the RRU circuitry to uplink signals received from a specific UE. ### Claim 10 (depends on 9) The one or more non-transitory, computer-readable media of claim 9 wherein the DL UE-specific precoding includes application of the UE-specific spatial filtering. ### Claim 11 (depends on 10) The one or more non-transitory, computer-readable media of claim 10, further including instructions to: receive a UL sounding reference signal (SRS); and estimate the UE-specific spatial filter based on the SRS. ### Claim 12 (depends on 11) The one or more non-transitory, computer-readable media of claim 11, wherein the estimate of the UE-specific spatial filter includes a conjugate channel of the UE. ### Claim 13 Remote radio unit (RRU) circuitry, comprising: a decompression unit to receive and decompress multiple user streams from a baseband unit; a downlink (DL) user equipment (UE)-specific precoder to compensate for characteristics of a channel between the RRU and a specific UE; and an uplink (UL) UE-specific spatial filter for a physical uplink shared channel (PUSCH). ### Claim 14 (depends on 13) The circuitry of claim 13, wherein the DL UE-specific precoder includes application of the UE-specific spatial filter in connection with DL beamforming. ### Claim 15 (depends on 13) The circuitry of claim 13, further including: a sounding reference signal (SRS) unit to receive a UL SRS and estimate the UE-specific spatial filter based on the SRS. ### Claim 16 (depends on 15) The circuitry of claim 15, wherein the estimate of the UE-specific spatial filter includes a conjugate channel of the UE. ### Claim 17 (depends on 13) The circuitry of claim 13, to control radio communication related to a massive multiple-input multiple-output (MIMO) system with at least twenty antennas. ### Claim 18 (depends on 14) The circuitry of claim 14, wherein the DL UE-specific precoder further is to receive the UE-specific spatial filter from a baseband unit. ### Claim 19 (depends on 13) The circuitry of claim 13, wherein the DL UE-specific precoder receives and is applied to a physical downlink shared channel (PDSCH). ### Claim 20 (depends on 19) The circuitry of claim 19, further including: a sounding reference signal (SRS) unit to receive a UL SRS and estimate the UE-specific spatial filter based on the SRS. ### Claim 21 (depends on 13) The circuitry of claim 13, further including a wideband precoder to apply wideband precoding to a physical downlink control channel (PDCCH) to provide a wideband-precoded PDCCH. ### Claim 22 (depends on 21) The circuitry of claim 21, wherein the DL UE-specific precoder receives and is applied to a physical downlink shared channel (PDSCH) to provide a UE-specific-precoded PDSCH and the circuitry further includes a framing unit to receive the wideband-precoded PDCCH and the UE-specific-precoded PDSCH to join them in a signal subframe structure.