Active-Coordination-Set Beam Failure Recovery

This document describes methods, devices, systems, and means for beam failure recovery for wireless communication in an active coordination set (ACS) by a user equipment (UE) in which the UE receives a beam-failure-recovery (BFR) Random Access Channel (RACH) configuration including multiple candidate beam configurations, each candidate beam configuration comprising a candidate BFR sub-beam configuration for each base station in the ACS. The UE detects a beam failure with the ACS and determines a respective link-quality metric for each of the received candidate beam configurations in the BFR RACH configuration. Based on the determined link-quality metrics, the UE selects a candidate beam to use for the wireless communication, and transmits a RACH message that includes an indication of the selected candidate beam, the transmitting being effective to direct the base stations in the ACS to use the selected candidate beam for the wireless communication.

BACKGROUND

An Active Coordination Set (ACS) of base stations provides and optimizes mobility management and other services to a user equipment (UE) in a radio access network (RAN). The ACS may be a component of, or used to implement, a user-centric no-cell (UCNC) network architecture. As a UE moves through the coverage provided by the RAN, the UE continually determines and updates, from its perspective, which base stations are usable for wireless communication.

In high frequency bands, such as millimeter wave (mmWave) or terahertz (THz) frequency bands, user mobility may cause frequent beam failures due to changes in multipath propagation or signal blockage from buildings, foliage, or other obstructions. When employing techniques, such as Coordinated MultiPoint (CoMP), sub-beams from each base station in an ACS together form a beam for beamformed wireless connections with a UE. However, if one or more sub-beams fail due to rapidly changing radio-channel conditions, base stations in the ACS need coordinate to determine a set of sub-beams to form a new beam for satisfactory communication with the user equipment.

SUMMARY

This summary is provided to introduce concepts of active-coordination-set beam failure recovery. The concepts are further described below in the Detailed Description. This summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter.

In aspects, methods, devices, systems, and means for beam failure recovery for wireless communication in an active coordination set (ACS) by a user equipment (UE) describe the user equipment receiving a beam-failure-recovery (BFR) Random Access Channel (RACH) configuration including multiple candidate beam configurations, each candidate beam configuration with a candidate BFR sub-beam configuration for each base station in the ACS. When the user equipment detects a beam failure during communication with the ACS and determines a respective link-quality metric for each of the received candidate beam configurations in the BFR RACH configuration. Based on the determined link-quality metrics, the user equipment selects a candidate beam to use for the wireless communication, and transmits a RACH message that includes an indication of the selected candidate beam, the transmitting being effective to direct the base stations in the ACS to use the selected candidate beam for the wireless communication.

In other aspects, methods, devices, systems, and means for beam failure recovery in an active coordination set describe a base station in the ACS that negotiates, with other base stations in the ACS, parameters for a BFR RACH configuration for a user equipment, the BFR RACH configuration including multiple candidate beam configurations, each candidate beam configuration with a respective candidate BFR sub-beam configuration for each base station in the ACS. The base station jointly-transmits, with the other base stations in the ACS, the BFR RACH configuration to the UE, the joint-transmission directing the UE to initialize parameters for a Beam Failure Detection and Recovery procedure. When the base station receives a RACH message from the UE that includes an indication of a selected candidate beam for the BFR, and based on the received RACH message, the base station coordinates with the other base stations to configure the base stations in the ACS to use the selected candidate beam for joint-communication with the UE. Along with the other base stations in the ACS, the base station jointly-transmits a RACH response message to the UE, with the RACH response message indicating that the ACS is using the selected candidate beam for the wireless communication with the UE. The base station jointly-communicates with the user equipment using the selected candidate beam indicated by the received RACH message, a superposition of the respective sub-beams of the base stations forming the selected candidate beam.

DETAILED DESCRIPTION

The evolution of wireless communication systems to fifth generation (5G) New Radio (5G NR) and Sixth Generation (6G) technologies provides higher data rates to users. By employing techniques, such as Coordinated MultiPoint (CoMP) over beamformed wireless connections, even higher data rates can be provided at the edges of 5G and 6G cells. However, identifying a satisfactory beam for communication between a user equipment (UE) and the base stations in an active coordination set (ACS) becomes increasingly complex at higher radio frequencies that are more susceptible to blockage and for UEs experiencing rapidly changing radio-channel conditions.

Conventional techniques for beam searches employ beam-sweeping during the attachment process of the UE with periodic beam-sweeping updates to identify a suitable beam for communication between a UE and a base station. These techniques are base-station-specific and do not fully account for the changing radio-channel environment of a user equipment communicating with multiple base stations in an ACS where a beam between the ACS and a UE is composed of sub-beams from each of the base stations in the ACS.

In aspects of active-coordination-set beam failure recovery, the base stations in an ACS coordinate with each other on a per-UE basis to determine configurations for beam-failure-recovery candidate beams. Collectively, the ACS determines a multi-base station beam-failure-recovery configuration, and the base stations coordinate to jointly-transmit a beam sweep for the candidate beams. During a beam-failure-recovery, each base station within the ACS transmits a specific sub-beam for each candidate beam, such that the superposition of sub-beams for each candidate beam from multiple base stations in the ACS forms the respective candidate beams within the candidate set of beams for the UE. Alternatively or additionally, the beam-failure-recovery process can be used to determine uplink receive beams for each base station in the ACS.

In conventional Coordinated Multipoint and/or Dual Connectivity (DC) communications, beam sweeps and beam failure recovery are independently performed by each base station or distributed unit in the CoMP or DC communication. In active-coordination-set beam failure recovery, the beam failure recovery is coordinated across the multiple base stations in the ACS. This coordination in beam failure recovery provides faster recovery of a usable beam configuration than independent beam recovery on a base station-by-base station basis to maintain higher bandwidth communications for the UE, especially in millimeter wave (mmWave) or terahertz (THz) frequency bands that are subject to frequent signal blocking and associated beam failures.

While features and concepts of the described devices, systems, and methods for active-coordination-set beam failure recovery can be implemented in any number of different environments, systems, devices, and/or various configurations, aspects of active-coordination-set beam failure recovery are described in the context of the following example devices, systems, and configurations.

Example Environment

FIG.1illustrates an example environment100in which various aspects of active-coordination-set beam failure recovery can be implemented. The example environment100includes a user equipment110(UE110) that communicates with one or more base stations120(illustrated as base stations121and122), through one or more wireless communication links130(wireless link130), illustrated as wireless links131and132. In this example, the user equipment110is implemented as a smartphone. Although illustrated as a smartphone, the user equipment110may be implemented as any suitable computing or electronic device, such as a mobile communication device, a modem, cellular phone, gaming device, navigation device, media device, laptop computer, desktop computer, tablet computer, smart appliance, or vehicle-based communication system. The base stations120(e.g., an Evolved Universal Terrestrial Radio Access Network Node B, E-UTRAN Node B, evolved Node B, eNodeB, eNB, Next Generation Node B, gNode B, gNB, ng-eNB, a 6G node B, or the like) may be implemented in a macrocell, microcell, small cell, picocell, distributed base station, and the like, or any combination or future evolution thereof.

The base stations120communicate with the user equipment110via the wireless links131and132, which may be implemented as any suitable type of wireless link. The wireless links131and132can include a downlink of data and control information communicated from the base stations120to the user equipment110, an uplink of other data and control information communicated from the user equipment110to the base stations120, or both. The wireless links130may include one or more wireless links or bearers implemented using any suitable communication protocol or standard, or combination of communication protocols or standards such as 3rd Generation Partnership Project Long-Term Evolution (3GPP LTE), Fifth Generation New Radio (5G NR), 6G, and so forth. Multiple wireless links130may be aggregated in a carrier aggregation to provide a higher data rate for the user equipment110. Multiple wireless links130from multiple base stations120may be configured for Coordinated Multipoint (CoMP) communication with the user equipment110. Additionally, multiple wireless links130may be configured for single-radio access technology (RAT) (single-RAT) dual connectivity (single-RAT-DC) or multi-RAT dual connectivity (MR-DC).

The base stations120are collectively a Radio Access Network140(RAN, Evolved Universal Terrestrial Radio Access Network, E-UTRAN, 5G NR RAN or NR RAN). The base stations121and122in the RAN140are connected to a core network150, such as a Fifth Generation Core (5GC) or 6G core network. The base stations121and122connect, at102and104respectively, to the core network150via an NG2 interface (or a similar 6G interface) for control-plane signaling and via an NG3 interface (or a similar 6G interface) for user-plane data communications. In addition to connections to core networks, base stations120may communicate with each other via an Xn Application Protocol (XnAP), at112, to exchange user-plane and control-plane data. The user equipment110may also connect, via the RAN140and the core network150, to public networks, such as the Internet160to interact with a remote service170.

Example Devices

FIG.2illustrates an example device diagram200of the user equipment110and the base stations120. The user equipment110and the base stations120may include additional functions and interfaces that are omitted fromFIG.2for the sake of clarity. The user equipment110includes antennas202, a radio frequency front end204(RF front end204), an LTE transceiver206, a 5G NR transceiver208, and a 6G transceiver210for communicating with base stations120in the RAN140. The RF front end204of the user equipment110can couple or connect the LTE transceiver206, the 5G NR transceiver208, and the 6G transceiver210to the antennas202to facilitate various types of wireless communication. The antennas202of the user equipment110may include an array of multiple antennas that are configured similarly to or differently from each other. The antennas202and the RF front end204can be tuned to, and/or be tunable to, one or more frequency bands defined by the 3GPP LTE, 5G NR, and 6G communication standards and implemented by the LTE transceiver206, the 5G NR transceiver208, and/or the 6G transceiver210. Additionally, the antennas202, the RF front end204, the LTE transceiver206, the 5G NR transceiver208, and/or the 6G transceiver210may be configured to support beamforming for the transmission and reception of communications with the base stations120. By way of example and not limitation, the antennas202and the RF front end204can be implemented for operation in sub-gigahertz bands, sub-6 GHz bands, and/or above 6 GHz bands that are defined by the 3GPP LTE, 5G NR, and 6G communication standards.

The user equipment110also includes processor(s)212and computer-readable storage media214(CRM214). The processor212may be a single core processor or a multiple core processor composed of a variety of materials, such as silicon, polysilicon, high-K dielectric, copper, and so on. The computer-readable storage media described herein excludes propagating signals. CRM214may include any suitable memory or storage device such as random-access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or Flash memory useable to store device data216of the user equipment110. The device data216includes user data, multimedia data, beamforming codebooks, applications, and/or an operating system of the user equipment110, which are executable by processor(s)212to enable user-plane communication, control-plane signaling, and user interaction with the user equipment110.

In some implementations, the CRM214may also include an active coordination set (ACS) manager218. The ACS manager218can communicate with the antennas202, the RF front end204, the LTE transceiver206, the 5G NR transceiver208, and/or the 6G transceiver210to monitor the quality of the wireless communication links130. Based on this monitoring, the ACS manager218can determine to add or remove base stations120from the ACS and/or determine beams to use for communication with base stations.

The device diagram for the base stations120, shown inFIG.2, includes a single network node (e.g., a gNode B). The functionality of the base stations120may be distributed across multiple network nodes or devices and may be distributed in any fashion suitable to perform the functions described herein. The base stations120include antennas252, a radio frequency front end254(RF front end254), one or more LTE transceivers256, one or more 5G NR transceivers258, and/or one or more 6G transceivers260for communicating with the UE110. The RF front end254of the base stations120can couple or connect the LTE transceivers256, the 5G NR transceivers258, and/or the 6G transceivers260to the antennas252to facilitate various types of wireless communication. The antennas252of the base stations120may include an array of multiple antennas that are configured similarly to or differently from each other. The antennas252and the RF front end254can be tuned to, and/or be tunable to, one or more frequency band defined by the 3GPP LTE, 5G NR, and 6G communication standards, and implemented by the LTE transceivers256, one or more 5G NR transceivers258, and/or one or more 6G transceivers260. Additionally, the antennas252, the RF front end254, the LTE transceivers256, one or more 5G NR transceivers258, and/or one or more 6G transceivers260may be configured to support beamforming, such as Massive-MIMO, for the transmission and reception of communications with the UE110.

The base stations120also include processor(s)262and computer-readable storage media264(CRM264). The processor262may be a single core processor or a multiple core processor composed of a variety of materials, such as silicon, polysilicon, high-K dielectric, copper, and so on. CRM264may include any suitable memory or storage device such as random-access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or Flash memory useable to store device data266of the base stations120. The device data266includes network scheduling data, radio resource management data, beamforming codebooks, applications, and/or an operating system of the base stations120, which are executable by processor(s)262to enable communication with the user equipment110.

CRM264also includes a base station manager268. Alternately or additionally, the base station manager268may be implemented in whole or part as hardware logic or circuitry integrated with or separate from other components of the base stations120. In at least some aspects, the base station manager268configures the LTE transceivers256, the 5G NR transceivers258, and the 6G transceiver(s)260for communication with the user equipment110, as well as communication with a core network, such as the core network150, and routing user-plane and control-plane data for joint communication. Additionally, the base station manager268may allocate air interface resources, schedule communications, configure beam recovery configurations, and preform beam-sweeps for the UE110and base stations120in the ACS when the base station120is acting as a coordinating base station for the base stations120in the ACS.

The base stations120include an inter-base station interface270, such as an Xn and/or X2 interface, which the base station manager268configures to exchange user-plane and control-plane data between other base stations120, to manage the communication of the base stations120with the user equipment110. The base stations120include a core network interface272that the base station manager268configures to exchange user-plane and control-plane data with core network functions and/or entities.

FIG.3illustrates an air interface resource that extends between a user equipment and a base station and with which various aspects of active-coordination-set beam failure recovery can be implemented. The air interface resource302can be divided into resource units304, each of which occupies some intersection of frequency spectrum and elapsed time. A portion of the air interface resource302is illustrated graphically in a grid or matrix having multiple resource blocks310, including example resource blocks311,312,313,314. An example of a resource unit304therefore includes at least one resource block310. As shown, time is depicted along the horizontal dimension as the abscissa axis, and frequency is depicted along the vertical dimension as the ordinate axis. The air interface resource302, as defined by a given communication protocol or standard, may span any suitable specified frequency range, and/or may be divided into intervals of any specified duration. Increments of time can correspond to, for example, milliseconds (mSec). Increments of frequency can correspond to, for example, megahertz (MHz).

In example operations generally, the base stations120allocate portions (e.g., resource units304) of the air interface resource302for uplink and downlink communications. Each resource block310of network access resources may be allocated to support respective wireless communication links130of multiple user equipment110. In the lower left corner of the grid, the resource block311may span, as defined by a given communication protocol, a specified frequency range306and comprise multiple subcarriers or frequency sub-bands. The resource block311may include any suitable number of subcarriers (e.g., 12) that each correspond to a respective portion (e.g., 15 kHz) of the specified frequency range306(e.g., 180 kHz). The resource block311may also span, as defined by the given communication protocol, a specified time interval308or time slot (e.g., lasting approximately one-half millisecond or seven orthogonal frequency-division multiplexing (OFDM) symbols). The time interval308includes subintervals that may each correspond to a symbol, such as an OFDM symbol. As shown inFIG.3, each resource block310may include multiple resource elements320(REs) that correspond to, or are defined by, a subcarrier of the frequency range306and a subinterval (or symbol) of the time interval308. Alternatively, a given resource element320may span more than one frequency subcarrier or symbol. Thus, a resource unit304may include at least one resource block310, at least one resource element320, and so forth.

In example implementations, multiple user equipment110(one of which is shown) are communicating with the base stations120(one of which is shown) through access provided by portions of the air interface resource302. The base station manager268(shown inFIG.2) may determine a respective data-rate, type of information, or amount of information (e.g., data or control information) to be communicated (e.g., transmitted) by the user equipment110. For example, the base station manager268can determine that each user equipment110is to transmit at a different respective data rate or transmit a different respective amount of information. The base station manager268then allocates one or more resource blocks310to each user equipment110based on the determined data rate or amount of information.

Additionally, or in the alternative to block-level resource grants, the base station manager268may allocate resource units at an element-level. Thus, the base station manager268may allocate one or more resource elements320or individual subcarriers to different user equipment110. By so doing, one resource block310can be allocated to facilitate network access for multiple user equipment110. Accordingly, the base station manager268may allocate, at various granularities, one or up to all subcarriers or resource elements320of a resource block310to one user equipment110or divided across multiple user equipment110, thereby enabling higher network utilization or increased spectrum efficiency.

The base station manager268can therefore allocate air interface resource302by resource unit304, resource block310, frequency carrier, time interval, resource element320, frequency subcarrier, time subinterval, symbol, spreading code, some combination thereof, and so forth. Based on respective allocations of resource units304, the base station manager268can transmit respective messages to the multiple user equipment110indicating the respective allocation of resource units304to each user equipment110. Each message may enable a respective user equipment110to queue the information or configure the LTE transceiver206, the 5G NR transceiver208, and/or the 6G transceiver210to communicate via the allocated resource units304of the air interface resource302.

Active Coordination Set

FIG.4illustrates an example environment400in which a user equipment110is moving through a radio access network (RAN) that includes multiple base stations120, illustrated as base stations121-127. These base stations may utilize different technologies (e.g., LTE, 5G NR, 6G) at a variety of frequencies (e.g., sub-gigahertz, sub-6 GHz, and above 6 GHz bands and sub-bands).

For example, the user equipment110follows a path402through the RAN140. The user equipment110periodically measures the link quality (e.g., of base stations that are currently in the ACS and candidate base stations that the UE110may add to the ACS. For example, at position404, the ACS at406includes the base stations121,122, and123. As the UE110continues to move, at position408, the UE110has deleted base station121and base station122from the ACS and added base stations124,125, and126, as shown at410. Continuing along the path402, the UE110, at position412, has deleted the base stations123and124and added the base station127, as shown in the ACS at414.

FIG.5illustrates an example environment500in which various aspects of active-coordination-set beam failure recovery can be implemented. The user equipment110is engaged in joint transmission and/or joint reception (joint communication) with the three base stations121,122, and123. The base station121is acting as a coordinating base station for the joint transmission and/or joint reception. Which base station is the coordinating base station is transparent to the UE110, and the coordinating base station can change as base stations are added and/or removed from the ACS. The coordinating base station coordinates control-plane and user-plane communications for the joint communication with the UE110via the Xn interfaces112(or a similar 6G interface) to the base stations122and123and maintains the user-plane context between the UE110and the core network150. The coordination may be performed using proprietary or standards-based messaging, procedures, and/or protocols.

The coordinating base station schedules air interface resources for the joint communication for the UE110and the base stations121,122, and123, based on the ACS associated with the UE110. The coordinating base station (base station121) connects, via an N3 interface501(or a 6G equivalent interface), to the User Plane Function510(UPF510) in the core network150for the communication of user plane data to and from the user equipment110. The coordinating base station distributes the user-plane data to all the base stations in the joint communication via the Xn interfaces112. The UPF510is further connected to a data network, such as the Internet160via the N6 interface502.

UE110downlink data can be sent from all the base stations120in the ACS or any subset of the base stations120in the ACS. The coordinating base station121determines which combination of base stations120in the ACS to use to transmit downlink data to the UE110. The selection of base stations120to use to transmit downlink data can be based on one or more factors, such as application quality of service (QoS) requirements, location of the UE110, velocity of the UE110, a Reference Signal Received Power (RSRP), a Received Signal Strength Indicator (RSSI), interference, or the like. UE110uplink data can be received by all the base stations120in the ACS or any subset of the base stations120in the ACS.

Similar to downlink data, the coordinating base station121determines which combination of base stations120in the ACS to use to receive uplink data from the UE110. The selection of base stations120to use to receive uplink data can be based on one or more factors, such as application QoS requirements, location of the UE110, velocity of the UE110, RSRP, RSSI, interference, or the like. Typically, the combination of base stations120for downlink transmission and uplink reception will be identical, although different combinations of base stations120may be used for downlink transmission and uplink reception. The ACS uplink and downlink assignments may also vary depending on the demand for available air interface resources at the individual base stations for other UEs, IAB, and other purposes.

When the user equipment110creates or modifies an ACS, the user equipment110communicates the ACS or the ACS modification to an ACS Server520that stores the ACS for each user equipment110operating in the RAN140. Although shown in the core network150, alternatively the ACS Server520may be an application server located outside the core network150. The user equipment110communicates the ACS or ACS modification via the coordinating base station (base station121) which is connected to the ACS Server520via an N-ACS interface503. Optionally or alternatively, the user equipment110communicates the ACS or ACS modification to the ACS Server520via the Access and Mobility Function530(AMF530) which is connected to the coordinating base station (base station121) via an N2 interface504. The AMF530relays ACS-related communications to and from the ACS Server520via an ACS-AMF interface505. ACS data between the user equipment110and the ACS Server520can be communicated via Radio Resource Control (RRC) communications, Non-Access Stratum (NAS) communications, or application-layer communications.

Active-Coordination-Set Beam Failure Recovery

FIG.6illustrates an example environment600in which a user equipment110is moving through a radio access network (RAN) that includes multiple base stations120, illustrated as base stations121-124. These base stations may support different technologies (e.g., LTE, 5G NR, 6G) at a variety of frequencies (e.g., sub-gigahertz, sub-6 GHz, above 6 GHz bands and sub-bands, mmWave bands, and THz bands).

For example, the user equipment110follows a path602through the RAN140while communicating using an ACS including base stations121,122,123, and124. Each of the base stations121,122,123, and124provides a sub-beam for a beamformed joint communication between the UE110and the ACS. As the UE110passes through the region604of the path602, a sub-beam (e.g., a sub-beam in the mmWave or THz bands) provided by the base station122is blocked by foliage reducing the link quality of the beam collectively provided by the ACS. Based on the sub-beam blockage causing a beam failure, the UE initiates a Beam Failure Detection and Recovery procedure (as described below) to determine a new beam configuration for joint-communication with the ACS.

As the UE110continues along the path602, the UE110experiences a second beam failure in the region606due to blockage of the sub-beam from the base station123by a building. As before, based on this second beam failure, the UE initiates another Beam Failure Detection and Recovery procedure to determine another new beam configuration for joint-communication with the ACS.

Base stations in an ACS coordinate with each other on a per-UE basis to determine configurations for beam-failure-recovery candidate beams. Collectively, the ACS determines a multi-base station beam-failure-recovery configuration. For each candidate beam, each base station within ACS transmits a specific sub-beam, such that the superposition of sub-beams from multiple base stations in the ACS forms one of the candidate beams within the candidate set of beams for the UE.

Each base station within an ACS can determine an individual sub-beam for a candidate beam in a beam-failure-recovery configuration based on UE-specific information. For example, the base station may determine candidate sub-beams based on the location of the UE, the velocity of the UE, the heading of the UE, a projected course of the UE (e.g., along an established walkway or roadway), UE-reported Reference Signal Receive Powers (RSRPs), or the like. The ACS beam-failure-recovery configuration includes a UE-specific ACS-Radio Network Temporary Identifier (ACS-RNTI), the candidate beam-failure-recovery (BFR) sub-beam configuration for each base station in the ACS, time/frequency air interface resources for the candidate beams, a BFR sequence (BFR RACH preamble sequence) common to all candidate beams, and the like for each BFR beam.

The ACS sends a beam-failure-recovery (BFR) Random Access Channel (RACH) configuration to each UE communicating using that ACS. For each UE, the coordinating base station for the ACS negotiates with the other base stations in the ACS to determine the BFR RACH configuration for the Beam Failure Detection and Recovery procedure. The ACS beam-failure-recovery RACH configuration includes the RACH time/frequency air interface resources as well as RACH sequences to use for the BFR.

Each base station within an ACS uses its own beam correspondence to determine the receive beam for an uplink (UL) RACH associated with the UE beam failure recovery. Base stations within the ACS coordinate to determine a power ramping step (e.g., powerRampingStep in 3GPP TS 38.321 V16.1.0) for the beam-failure-recovery RACH. The ACS includes the power ramping step as the powerRampingStep parameter in the RACH configuration for the beam failure recovery. In one example, the ACS determines the power ramping step based on a joint-processing signal-to-interference-plus-noise ratio (SINR) of UE uplink signals as observed by the ACS.

Base stations within the ACS negotiate the timing of the beam-failure response with respect to the received beam-failure request. The timing depends on the timing of the joint-reception and joint-processing of the received RACH message for the beam-failure request by the ACS. For example, the timing of the joint-reception and joint-processing depends on Xn interface latency between the base stations in the ACS.

The ACS can define an ACS Channel State Information (CSI) process such that a single ACS CSI feedback represents the superposition of sub-beams from each base station in the ACS. The ACS defines the ACS CSI process for each UE by including the ACS CSI time/frequency air interface resource configurations for each sub-beam used by each base station in the ACS. Each base station uses feedback from the UE for each ACS CSI process to determine the sub-beam(s) used in a beam-failure-recovery candidate beam.

FIG.7illustrates example data and control transactions between an ACS and a UE in accordance with aspects of active-coordination-set beam failure recovery. An ACS702, including the coordinating base station121and one or more additional base stations120, is jointly-communicating (joint transmission and/or joint reception) with the UE110.

At705, the ACS702determines a beam-failure-recovery (BFR) RACH configuration for initialization of a Beam Failure Detection and Recovery procedure (e.g., a Random Access procedure) by the UE110. The ACS can include the beam-failure-recovery RACH configuration in a configuration for initialization of a Random Access procedure (e.g., as described in 3GPP TS 38.321 V16.1.0, section 5.1.1). The beam-failure-recovery RACH configuration includes a UE-specific ACS-Radio Network Temporary Identifier (ACS-RNTI), the candidate beam-failure-recovery (BFR) sub-beam configuration for each base station in the ACS, time/frequency air interface resources for the candidate beams, a BFR sequence (BFR RACH preamble sequence), and the like for each BFR beam. This BFR RACH configuration determination can be triggered periodically or based on past history of ACS beam failures (e.g., by the same UE or by other UEs, with the same ACS or coordinating base station). For example, trigger conditions include a UE-reported RSRP, a UE-reported Reference Signal Received Quality (RSRQ), a UE-reported downlink SINR, a base station observed uplink SINR, a base station received signal level on a UE Sounding Reference Signal (SRS), or the like.

At710, the base stations in the ACS702jointly-transmit the beam-failure-recovery RACH configuration to the UE110. The ACS702can transmit the BFR RACH configuration in a layer-3 message, for example a Radio Resource Control (RRC) message.

At some point in time after receiving the beam-failure-recovery RACH configuration, the UE110detects a beam failure at715. At720, the detection of the beam failure causes the UE110to trigger the Beam Failure Detection and Recovery procedure to search for a beam configuration for communication with the ACS702. For example, the UE110determines a link-quality metric, for example an ACS CSI feedback value, for each of the candidate beams in the BFR RACH configuration and selects the candidate beam with the best link-quality metric (ACS CSI feedback value). Optionally or additionally, the UE110can select the first candidate beam that exceeds a threshold value for the link-quality metric, thus reducing the time to select a candidate beam configuration as compared to evaluating all the candidate beams before selecting a candidate beam.

At725, based on selecting the candidate beam configuration for communication with the ACS702, the UE110transmits a RACH message that includes an indication of the selected candidate beam to the ACS702. In one option, the UE110transmits the RACH message in a sub-6 GHz frequency band to improve the likelihood of reception by the ACS. At730, the ACS702transmits a RACH response message to the UE110indicating the ACS is using the selected candidate beam for communication with the UE110. Additionally, at725, the UE110initializes a timer for the reception of the RACH response message. At735, if the timer expires before the UE receives the RACH response message, the UE retransmits the RACH message. To account for communication latencies over the Xn interface between the base station in the ACS, the timer value may be longer than a timer value used for beam-failure-recovery with a single base station. Optionally, if the ACS702configures a power ramping step to direct increases of the transmit power for retransmissions of the RACH message, the UE at740increases the transmit power for the RACH message by the specified power ramping step and retransmits the RACH message.

At745, the base stations in the ACS702begin joint-communication with the UE110using the selected candidate beam configuration. Each base station120communicates using its respective sub-beam to form the selected beam.

Example Methods

Example methods800and900are described with reference toFIGS.8and9in accordance with one or more aspects of active-coordination-set beam failure recovery.FIG.8illustrates example method(s)800of active-coordination-set beam failure recovery as generally related to the user equipment110selecting a candidate beam to recover from a beam failure.

At block802, a user equipment receives a beam-failure-recovery (BFR) Random Access Channel (RACH) configuration including multiple candidate beam configurations, each candidate beam configuration comprising a candidate BFR sub-beam configuration for each base station in the ACS. For example, a UE (e.g., the UE110) receives a BFR RACH configuration including multiple candidate beam configurations, each candidate beam configuration comprising a candidate BFR sub-beam configuration for each base station (e.g., the base stations120) in the ACS (e.g., the ACS702).

At block804, the user equipment detects a beam failure during communication with the ACS. For example, the user equipment110detects a beam failure during communication with the ACS702that causes the UE110to trigger the Beam Failure Detection and Recovery procedure to search for a new beam configuration for communication with the ACS702.

At block806, the user equipment determines a respective link-quality metric for each of the received candidate beam configurations in the BFR RACH configuration. For example, the user equipment110determines a respective link-quality metric, for example a Reference Signal Receive Power (RSRP), for each of the received candidate beam configurations in the BFR RACH configuration.

At block808, based on the determined link-quality metrics, the user equipment selects a candidate beam to use for the wireless communication. For example, based on the determined link-quality metrics, the user equipment110selects a candidate beam (e.g., the candidate beam with highest RSRP) to use for the wireless communication.

At block810, the user equipment transmits a RACH message that includes an indication of the selected candidate beam, the transmitting being effective to direct the base stations in the ACS to use the selected candidate beam for the wireless communication. For example, the user equipment110transmits a RACH message, including an indication of the selected candidate beam, that directs each base station120and121in the ACS to use a respective sub-beam configuration for the selected candidate beam for the wireless communication.

FIG.9illustrates example method(s)900of active-coordination-set beam failure recovery as generally related to a base station configuring a beam failure recovery (BFR) for a user equipment. At block902, a base station negotiates, with other base stations in the ACS, parameters for a BFR Random Access Channel (RACH) configuration for a user equipment, the BFR RACH configuration including multiple candidate beam configurations, each candidate beam configuration comprising a respective candidate BFR sub-beam configuration for each base station in the ACS. For example, a base station (e.g., a coordinating base station121) negotiates, with other base stations (e.g., the base stations120) in the ACS (e.g., the ACS702), parameters for a BFR RACH configuration for a user equipment (e.g., the UE110). The BFR RACH configuration includes multiple candidate beam configurations, each candidate beam configuration comprising a respective candidate BFR sub-beam configuration for each base station120and121in the ACS702. For example, base stations may conduct the negotiation using an inter-base station interface (e.g., the Xn interface112) for communication between the base stations in the ACS702.

At block904, the base station jointly-transmits, with the other base stations in the ACS, the BFR RACH configuration to the UE, the joint-transmission directing the UE to initialize parameters for a Beam Failure Detection and Recovery procedure. For example, the coordinating base station121jointly-transmits, with the other base stations120in the ACS702, the BFR RACH configuration to the UE110, the jointly-transmitting directing the UE110to initialize parameters for a Beam Failure Detection and Recovery procedure that can be triggered by the UE110upon the detection of a beam failure. The BFR RACH configuration includes a power ramping step parameter, an indication of air interface resources for the candidate beams, a BFR sequence, or the like.

At block906, the base station receives a RACH message from the UE that includes an indication of a selected candidate beam for the BFR. For example, the coordinating base station121receives a RACH message from the UE110that includes an indication of a candidate beam selected by the UE110for the BFR.

At block908, based on the received RACH message, the base station coordinates with the other base stations to configure the base stations in the ACS to use the selected candidate beam for joint-communication with the UE. For example, based on the received RACH message, the coordinating base station121coordinates with the other base stations120to configure the base stations in the ACS702to provide sub-beams for the selected candidate beam for joint-communication with the UE110.

At block910, the base station jointly-transmits a RACH response message, with the other base stations in the ACS, to the UE, the RACH response message indicating that the ACS is using the selected candidate beam for the wireless communication with the UE. For example, the coordinating base station121jointly-transmits a RACH response message, with the other base stations120in the ACS702, to the UE110, the RACH response message indicating that the ACS702is using the selected candidate beam for the wireless communication with the UE110. The base stations coordinate the timing of the joint transmission using the Xn interface.

At block912, the base station jointly-communicates with the user equipment using the selected candidate beam indicated by the received RACH message, a superposition of the respective sub-beams of the base stations forming the selected candidate beam. For example, the coordinating base station121and the other base stations120in the ACS702jointly-communicate with the user equipment110using the selected candidate beam indicated by the received RACH message, a superposition of the respective sub-beams of the base stations forming the selected candidate beam.

The order in which the method blocks are described are not intended to be construed as a limitation, and any number of the described method blocks can be skipped or combined in any order to implement a method or an alternate method. Generally, any of the components, modules, methods, and operations described herein can be implemented using software, firmware, hardware (e.g., fixed logic circuitry), manual processing, or any combination thereof. Some operations of the example methods may be described in the general context of executable instructions stored on computer-readable storage memory that is local and/or remote to a computer processing system, and implementations can include software applications, programs, functions, and the like. Alternatively or in addition, any of the functionality described herein can be performed, at least in part, by one or more hardware logic components, such as, and without limitation, Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), System-on-a-chip systems (SoCs), Complex Programmable Logic Devices (CPLDs), and the like.

In the following text some examples are described:Example 1: A method of beam failure recovery for wireless communication in an active coordination set, ACS, comprising multiple base stations, by a user equipment, UE, the method comprising the user equipment:receiving a beam-failure-recovery, BFR, Random Access Channel, RACH, configuration including multiple candidate beam configurations, each candidate beam configuration comprising a candidate BFR sub-beam configuration for each of the multiple base stations in the ACS;detecting a beam failure during communication with the ACS;determining a respective link-quality metric for each of the received candidate beam configurations in the BFR RACH configuration;based on the determined link-quality metrics, selecting a candidate beam to use for the wireless communication based on the multiple candidate beam configurations; andtransmitting a RACH message that includes an indication of the selected candidate beam, the transmitting being effective to direct the base stations in the ACS to use the selected candidate beam for the wireless communication.Example 2: The method of example 1, further comprising the user equipment:receiving a RACH response message from the ACS that indicates that the ACS is using the selected candidate beam for the wireless communication.Example 3: The method of example 2, further comprising the user equipment:initializing a timer concurrently with the transmitting the RACH message; andif the timer expires before the receiving the RACH response message, retransmitting the RACH message.Example 4: The method of example 3, wherein the BFR RACH configuration includes a power ramping step parameter, the method further comprising the user equipment:increasing a transmit power for the retransmitting the RACH message by an amount of power indicated by the power ramping step parameter.Example 5: The method of any one of the preceding examples, wherein the selected candidate beam for the wireless communication is a superposition of multiple candidate sub-beams, each candidate sub-beam transmitted or received by a respective base station of the multiple base stations in the ACS.Example 6: The method of any one of the preceding examples, wherein the receiving the BFR RACH configuration comprises:receiving the BFR RACH configuration in a layer-3 message.Example 7: The method of example 6, wherein the layer-3 message is a Radio Resource Control, RRC, message.Example 8: The method of any one of the preceding examples, wherein a configuration for initialization of a Random Access procedure includes the BFR RACH configuration.Example 9: The method of any one of the preceding examples, wherein the BFR RACH configuration includes an indication of air interface resources for the candidate beams and a BFR sequence.Example 10: The method of any one of the preceding examples, wherein the determining the respective link-quality metric for each of the received candidate beam configurations in the BFR RACH configuration comprises:receiving an ACS Channel State Information, CSI, time/frequency resource configuration for each candidate beam; anddetermining ACS CSI feedback for each of the received candidate beams.Example 11: The method of any one of the preceding examples, wherein the selecting the candidate beam to use for the wireless communication based on the multiple candidate beam configurations comprises:selecting a first candidate beam with a link-quality metric that exceeds a threshold value.Example 12: The method of any one of the preceding examples, wherein transmitting the RACH message that includes the indication of the selected candidate beam comprises:transmitting the RACH message using a sub-6 GHz frequency band.Example 13: The method of any one of the preceding examples, further comprising the user equipment:jointly-communicating with the ACS using the selected candidate beam indicated by the transmitted RACH message, the selected candidate beam being formed by superposition of a respective sub-beam of each of the multiple base stations in the ACS.Example 14: A user equipment comprising:a wireless transceiver;a processor; andinstructions for an active coordination set manager that are executable by the processor to configure the user equipment to perform any one of methods 1 to 13.Example 15: A method of beam failure recovery, BFR, in an active coordination set, ACS, the method comprising a base station in the ACS:negotiating, with other base stations included in the ACS, parameters for a BFR Random Access Channel, RACH, configuration for a user equipment, UE, the BFR RACH configuration including multiple candidate beam configurations, each candidate beam configuration comprising a respective candidate BFR sub-beam configuration for each base station in the ACS;jointly-transmitting, with the other base stations included in the ACS, the BFR RACH configuration to the UE;receiving a RACH message from the UE that includes an indication of a selected candidate beam for the BFR based on the multiple candidate beam configurations; andbased on the received RACH message, coordinating with the other base stations to configure the base stations in the ACS to use the selected candidate beam for joint-communication with the UE.Example 16: The method of example 15, wherein the parameters for the BFR RACH configuration include one or more of:a power ramping step parameter;an indication of air interface resources for the candidate beams; ora BFR sequence.Example 17: The method of example 15 or example 16, wherein the jointly-transmitting the BFR RACH configuration to the UE comprises:jointly-transmitting the BFR RACH configuration in a layer-3 message.Example 18: The method of example 17, wherein the layer-3 message is a Radio Resource Control, RRC, message.Example 19: The method of any one of examples 11 to 18, further comprising the base station:including the BFR RACH configuration in a configuration for initialization of a Random Access procedure.Example 20: The method of any one of examples 15 to 19, wherein the negotiating the parameters for the BFR RACH configuration comprises:determining candidate sub-beams based on one or more of:a location of the UE;a velocity of the UE;a heading of the UE;a projected course of the UE; orone or more UE-reported Reference Signal Receive Powers, RSRPs.Example 21: The method of any one of examples 15 to 20, wherein the negotiating the parameters for the BFR RACH configuration comprises:determining a power ramping step for a Beam Failure Detection and Recovery procedure; andincluding the determined power ramping step in the BFR RACH configuration.Example 22: The method of example 21, wherein the determining a power ramping step for the BFR comprises:determining the power ramping step based on a joint-processing signal-to-interference-plus-noise ratio (SINR) of the UE as observed by the ACS.Example 23: The method of any one of examples 15 to 22, wherein the negotiating the parameters for the BFR RACH configuration comprises:negotiating with the other base stations using an Xn interface for communication with the other base stations in the active coordination set.Example 24: The method of any one of examples 15 to 23, further comprising the base station:jointly-communicating with the user equipment using the selected candidate beam indicated by the received RACH message, the selected candidate beam being formed by superposition of a respective sub-beam of each of the base stations in the ACS.Example 25: The method of any one of examples 15 to 23, the method further comprising the base station:jointly-transmitting a RACH response message, with the other base stations in the ACS, to the UE, the RACH response message indicating that the ACS is using the selected candidate beam for wireless communication with the UE.Example 26: A base station comprising:a wireless transceiver;a processor; andinstructions for a base station manager that are executable by the processor to configure the base station to perform any one of methods 15 to 25.Example 27: A computer-readable medium comprising instructions that, when executed by a processor, cause an apparatus comprising the processor to perform any of the methods of examples 1 to 13 or 15 to 25.

Although aspects of active-coordination-set beam failure recovery have been described in language specific to features and/or methods, the subject of the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example implementations of active-coordination-set beam failure recovery, and other equivalent features and methods are intended to be within the scope of the appended claims. Further, various different aspects are described, and it is to be appreciated that each described aspect can be implemented independently or in connection with one or more other described aspects.