# US 11,909,441 B2 · Base station and a method for operating the base station > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,909,441 B2 - Document ID: US11909441B2 - Status: Granted - Kind: B2 - Application number: 17/353,461 - Filed: 2021-06-21 - Published: 2021-10-07 - Granted: 2024-02-20 - Earliest claimed: 2018-12-19 - Assignees: Huawei Technologies Co., Ltd. - Applicants: Huawei Technologies Co., Ltd. - Inventors: Hongqiang Bao; Zhipeng Zhao; Ramin Khayatzadeh; Ganghua Yang - Web page: https://patentgrep.com/patent/US11909441B2 ## CPC - H04B 10/2507: for the reduction or elimination of distortion or dispersion - H04W 88/085: {Access point devices with remote components} - H03F 1/3241: {using predistortion circuits (H03F1/3211, H03F1/3217 take precedence)} - H03F 1/3247: {using feedback acting on predistortion circuits (H03F1/3264 takes precedence)} - H03F 3/189: High-frequency amplifiers, e.g. radio frequency amplifiers - H03F 3/24: of transmitter output stages - H04B 10/25753: {Distribution optical network, e.g. between a base station and a plurality of remote units} - H04W 72/21: in the uplink direction of a wireless link, i.e. towards the network - H04W 88/08: Access point devices - H03F 2200/207: A hybrid coupler being used as power measuring circuit at the output of an amplifier circuit - H03F 2200/451: the amplifier being a radio frequency amplifier - H04B: TRANSMISSION - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) - H03F: AMPLIFIERS ## Abstract This application provides an example base station for an example wireless communication network and an example method. One example base station includes a central unit and a remote radio unit (RRU). The RRU includes one or more antennas. The RRU is coupled to the central unit via one or more optical transmission fibers. Each optical transmission fiber defines a respective downlink transmission channel for transmitting a respective downlink transmission signal from the central unit to the respective antenna of the RRU. The RRU is configured to provide a respective uplink feedback signal based on the respective downlink transmission signal via an uplink feedback channel to the central unit. ## Claims ### Claim 1 A base station, comprising: a central unit; and a remote radio unit (RRU), comprising: a plurality of antennas, wherein the RRU is coupled to the central unit via a plurality of optical transmission fibers, wherein each optical transmission fiber of the plurality of optical transmission fibers defines a respective downlink transmission channel for transmitting a respective downlink transmission signal from the central unit to a respective antenna of the plurality of antennas of the RRU, wherein the RRU is configured to provide a respective uplink feedback signal via an uplink feedback channel to the central unit for reducing non-linear distortions of the respective downlink transmission signal, wherein the respective uplink feedback signal is based on the respective downlink transmission signal, the RRU comprising a coupler configured to couple, selectively, the respective downlink transmission channels with the uplink feedback channel for providing the respective uplink feedback signal via the uplink feedback channel to the central unit. ### Claim 2 (depends on 1) The base station of claim 1, wherein the central unit comprises an adjustable pre-distorter configured to pre-distort the respective downlink transmission signal to be transmitted to the respective antenna of the RRU based on the respective uplink feedback signal. ### Claim 3 (depends on 2) The base station of claim 2, wherein the central unit is configured to: transmit a respective training signal via the respective downlink transmission channel to the respective antenna of the RRU; and adjust the adjustable pre-distorter based on the respective uplink feedback signal, wherein the respective uplink feedback signal is based on the respective training signal. ### Claim 4 (depends on 3) The base station of claim 3, wherein the central unit is further configured to adjust the adjustable pre-distorter using an iterative adjustment scheme. ### Claim 5 (depends on 1) The base station of claim 1, wherein the base station is configured to operate the uplink feedback channel in linear regime. ### Claim 6 (depends on 1) The base station of claim 1, wherein the RRU is further configured to reduce a signal strength of the respective uplink feedback signal. ### Claim 7 (depends on 1) The base station of claim 1, wherein the base station further comprises a frequency converter, wherein the frequency converter is configured to frequency down-convert the respective uplink feedback signal. ### Claim 8 (depends on 1) The base station of claim 1, wherein the central unit further comprises a digital-to-analog converter for converting the respective downlink transmission signal to be transmitted to the respective antenna of the RRU from a digital domain to an analog domain. ### Claim 9 (depends on 1) The base station of claim 1, wherein the RRU further comprises for each antenna of the plurality of antennas a power amplifier configured to amplify the respective downlink transmission signal received from the central unit. ### Claim 10 (depends on 1) The base station of claim 1, wherein the optical transmission fiber defines the respective downlink transmission channel and the uplink feedback channel between the RRU and the central unit. ### Claim 11 (depends on 1) The base station of claim 1, wherein each respective one of the optical transmission fibers further defines an uplink transmission channel between the RRU and the central unit. ### Claim 12 (depends on 1) The base station of claim 1, wherein the base station comprises a further optical transmission fiber defining the uplink feedback channel between the RRU and the central unit. ### Claim 13 A method of operating a base station for a wireless communication network, the base station comprising: a central unit; and a remote radio unit (RRU) comprising a plurality of antennas, wherein the RRU is coupled to the central unit via a plurality of optical transmission fibers, wherein each optical transmission fiber of the plurality of optical transmission fibers defines a respective downlink transmission channel, the RRU comprising a coupler configured to couple, selectively, the respective downlink transmission channels with the uplink feedback channel, wherein the method comprises: transmitting a respective downlink transmission signal from a respective one of the downlink transmission channels to a respective antenna of the plurality of antennas of the RRU; selectively coupling, via the coupler, the respective one of the downlink transmission channels with the uplink feedback channel; and providing a respective uplink feedback signal based on the respective downlink transmission signal via the uplink feedback channel to the central unit for reducing non-linear distortions of the respective downlink transmission signal. ### Claim 14 A system comprising a base station for a wireless communication network, the base station comprising: a central unit; a remote radio unit (RRU), comprising: a plurality of antennas, wherein the RRU is coupled to the central unit via a plurality of optical transmission fibers, wherein each optical transmission fiber of the plurality of optical transmission fibers defines a respective downlink transmission channel, the RRU comprising a coupler configured to couple, selectively, the respective downlink transmission channels with the uplink feedback channel; and one or more tangible, non-transitory, computer-readable media storing instructions that, when executed by a processor of the base station, cause operations to be performed comprising: transmitting a respective downlink transmission signal from a respective one of the downlink transmission channels to a respective antenna of the plurality of antennas of the RRU; selectively coupling, via the coupler, the respective one of the downlink transmission channels with the uplink feedback channel; and providing a respective uplink feedback signal based on the respective downlink transmission signal via the uplink feedback channel to the central unit for reducing non-linear distortions of the respective downlink transmission signal.