Systems, methods, and apparatus for inactive state beam failure recovery

Abstract

A method for beam failure recovery in a communication network can include detecting, at a user equipment (UE) in an inactive state, a beam failure based on a downlink transmission; and performing, at the UE in the inactive state, a beam failure recovery (BFR) procedure based on detecting the beam failure. The downlink transmission can include a reference signal. The reference signal can include a synchronization signal block. The reference signal can include a channel state information reference signal. Detecting the beam failure can include detecting the beam failure based on a beam failure measurement configuration. The method can further include receiving, at the UE, the beam failure measurement configuration. The UE can receive the beam failure measurement configuration based on a preconfigured uplink resource (PUR) response. The UE can receive the beam failure measurement configuration based on a system information block (SIB) transmission.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 061,779, filed August 5, 2020, entitled “Beam Failure Recovery and Reconfiguration in RRC_Inactive State,” and U.S. Provisional Patent Application No. 63 / 075,812, filed September 8, 2020, entitled “Beam Failure Recovery and Reconfiguration in RRC_Inactive State,” which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates generally to communication systems, and more specifically to systems, methods, and apparatuses for beam failure recovery and / or reconfiguration in an inactive state. BACKGROUND

[0004] Wireless communication networks can use beamforming techniques to improve data transmission between devices, such as base stations and user equipment (UEs). However, beams between devices can experience failure due to various reasons, such as blockage due to a person walking between the devices. Beam failure recovery (BFR) techniques can be used to recover data transmission between devices experiencing beam failure. A base station can detect a downlink beam failure and can then initiate a recovery procedure in which a new beam can be selected for data transmission.

[0005] The above information disclosed in the Background section is only for enhancing the understanding of the background of the application, therefore, it can contain information that does not constitute the prior art. SUMMARY

[0006] A method for beam failure recovery in a communication network can include detecting, at a user equipment (UE) in an inactive state, a beam failure based on a downlink transmission; and performing, at the UE in the inactive state, a beam failure recovery (BFR) procedure based on detecting the beam failure. The downlink transmission can include a reference signal. The reference signal can include a synchronization signal block. The reference signal can include a channel state information reference signal. Detecting the beam failure can include detecting the beam failure based on a beam failure measurement configuration. The method can further include receiving, at the UE, the beam failure measurement configuration. The UE can receive the beam failure measurement configuration based on a preconfigured uplink resource (PUR) response. The UE can receive the beam failure measurement configuration based on a system information block (SIB) transmission. The UE can be preconfigured with at least a portion of the beam failure measurement configuration in a connected state. Detecting the beam failure can include switching one or more beams based on the beam failure measurement configuration and measuring the one or more beams based on the beam failure measurement configuration.

[0007] A first active spatial relation information of two or more spatial relation information for a preconfigured uplink resource (PUR) physical uplink shared channel (PUSCH) can be quasi co-located (QCLed) with a first synchronization signal block (SSB) index of two or more SSB indexes, which can be QCLed with one or more downlink channels for a PUR response message, the two or more SSB indexes are preconfigured with the two or more spatial relation information QCLed with the two or more SSB indexes, and detecting the beam failure can further include determining, by the base station, a second spatial relation of the two or more spatial relations, activating the second spatial relation of the two or more spatial relations by a medium access control (MAC) control element (CE). The UE can perform one or more measurements of a physical downlink control channel (PDCCH) that schedules a physical downlink shared channel (PDSCH) of the PUR response message that carries one or more of the SSBs corresponding to the two or more SSB indexes, and report the one or more measurements to the base station. The base station can determine the second spatial relation of the two or more spatial relations based on the one or more measurements, and activate the second spatial relation of the two or more spatial relations by a MAC CE in the PDSCH, and detecting the beam failure can further include updating the PDCCH and the PDSCH to a transmission control indicator (TCI) state that is QCLed with a SSB index corresponding to the second spatial relation of the two or more spatial relations. A first TCI state for a PDSCH reception of a PUR occasion can be QCLed with a default TCI state of a PDCCH reception for a PUR response for the PUR occasion based on a delay between the PDSCH reception and the PDCCH reception. The UE can monitor one or more control resource sets (CORESETs) in a slot, and the default TCI state of the PDCCH reception can include a first CORESET of the one or more CORESETs corresponding to the SSB index. The default TCI state of the PDCCH reception can include the SSB index that is QCLed with the PUR. The first TCI state for the PDSCH reception of the PUR occasion can be QCLed with the SSB index of a QCL relationship for the PDCCH reception based on a delay between the PDSCH reception and the PDCCH reception for the PUR response for the PUR occasion.

[0008] The UE can perform one or more first measurements of one or more downlink beams in a first set of one or more periodic SSB indexes, the UE can perform one or more second measurements of one or more downlink beams in a second set of one or more candidate beams for recovery, and the method can further include determining a beam failure based on the one or more first measurements and determining a beam for recovery based on the one or more second measurements. Performing the BFR procedure can include transmitting a contention-free beam recovery request and providing a CORESET to the UE by a link to a search space set for monitoring a PDCCH in the CORESET. The search space set can be configured in a connected state. The search space set can be configured in an inactive state by a PUR response message. The search space set can be configured in an inactive state by a SIB message.

[0009] Performing the BFR procedure can include transmitting a contention-free beam recovery request and monitoring, by the UE, a PDCCH on a CORESET linked to an SSB index corresponding to a physical random access channel (PRACH) transmitted by the UE. Performing the BFR procedure can include transmitting a contention-free beam recovery request and providing a configuration for a PRACH transmission to the UE. The configuration can be provided in a connected state. The configuration can be provided in an inactive state by a PUR response message. The configuration can be provided in an inactive state by a SIB message. Performing the BFR procedure can include transmitting a contention-based beam recovery request and the contention-based beam recovery request can be based on a preamble and a random access channel (RACH) occasion quasi co-located with a selected candidate beam direction. The method can further include performing an uplink transmission from the UE in an inactive state and the downlink transmission can include an acknowledgement for the uplink transmission. The uplink transmission can include a preconfigured uplink resource (PUR) transmission. The UE can perform a transition to a connected state and the UE can indicate that the transition can be based on detecting a beam failure.

[0010] An apparatus can include a transceiver configured to access a communication network and an apparatus controller configured to control the transceiver to detect a beam failure based on a downlink transmission in an inactive state and to perform a beam failure recovery procedure based on detecting the beam failure. The downlink transmission can include a reference signal. The apparatus controller can be configured to transmit an uplink transmission in the inactive state and the downlink transmission can include an acknowledgement for the uplink transmission.

[0011] A method for beam failure recovery in a communication network can include detecting, at a first transmit-receive point (TRP), a performance condition in an uplink beam shared by a first user equipment (UE) in an inactive state and a second UE in an inactive state; transmitting, from the first TRP to the first UE, a downlink transmission based on detecting the performance condition; and performing, at the first UE, a transition procedure from the first TRP to a second TRP based on the downlink transmission. The transition procedure can include performing a beam management procedure with the second TRP. The beam management procedure can include selecting a candidate beam with the second TRP. The downlink transmission can include a preconfigured uplink resource (PUR) response message. BRIEF DESCRIPTION OF DRAWINGS

[0012] The drawings are not necessarily to scale and, in some instances, proportions of certain parts have been exaggerated from the drawings for illustrative purposes. Generally, similar reference numbers and / or characters denote like elements throughout the drawings. The drawings are only intended to facilitate an understanding of the various embodiments described herein and are not intended to limit the scope of the disclosure. Not all components, connections, and / or features can be shown in each drawing, and some components, connections, and / or features can be shown in more than one drawing. However, the pattern of components’ configurations shown in the drawings is readily apparent and thus, the pattern is not repeated in the description since it is believed that the pattern is sufficiently understood from the drawings alone. The drawings, together with the description, serve to explain principles of the disclosure.

[0013] Figure 1A Example embodiments of signaling involved in a legacy (e.g., LTE) idle-to-connected transition are shown.

[0014] Figure 1B Example embodiments of signaling involved in an NR inactive-to-connected transition according to the present disclosure are shown.

[0015] Figure 2 Example embodiments of configured grant small data transmission operation in an inactive state according to the present disclosure are shown.

[0016] Figure 3 An overview of example message sequences for a beam refinement procedure for a UE in an RRC_INACTIVE state according to the present disclosure is shown.

[0017] Figure 4 Another example message sequence for a beam refinement procedure for a UE in an RRC_INACTIVE state according to the present disclosure is shown.

[0018] Figure 5 Example embodiments of a beam failure procedure in which no beam failure is detected according to the present disclosure are shown.

[0019] Figure 6 An example embodiment of a beam failure procedure according to the present disclosure in which a beam failure is detected is shown.

[0020] Figure 7 An example embodiment of a beam failure detection and recovery method for a UE in an inactive state according to the present disclosure is shown.

[0021] Figure 8 An example embodiment of a user equipment according to the present disclosure is shown.

[0022] Figure 9 An example embodiment of a base station according to the present disclosure is shown.

[0023] Figure 10 An embodiment of a method for beam failure recovery in a communication network according to the present disclosure is shown.

[0024] Figure 11 Another embodiment of a method for beam failure recovery in a communication network according to the present disclosure is shown. DETAILED DESCRIPTION

[0025] SUMMARY

[0026] The present disclosure encompasses a number of inventive principles related to beam failure detection and / or recovery for a UE in an inactive state. These principles can have independent utility and can be embodied individually, and not every embodiment can utilize each principle. Moreover, these principles can also be embodied in various combinations, some of which can amplify the benefits of the individual principles in a synergistic manner.

[0027] In some embodiments, a UE according to the present disclosure can detect a beam failure in an inactive state based on one or more downlink reference signals, such as a synchronization signal block (SSB), a channel state information reference signal (CSI-RS), and the like. According to the present disclosure, a UE can detect a beam failure by measuring one or more reference signals using a measurement configuration that can be made available to the UE through various mechanisms. For example, a UE can receive a measurement configuration with a response to a preconfigured uplink resource (PUR) message transmitted by the UE. As another example, a UE can receive a measurement configuration with a system information block (SIB) transmission that can be transmitted periodically and / or on-demand by the UE. As yet another example, a UE can be preconfigured with a measurement configuration, e.g., in an RRC connected state.

[0028] To detect beam failure in an inactive state, a UE according to the present disclosure can implement one or more beam switching and / or measurement techniques that can be applicable to operating in an inactive state (e.g., in a PUR framework). Some of these inactive state beam switching and / or measurement techniques according to the present disclosure involve a UE obtaining a set of one or more SSB indexes. For example, a UE can be provided with a set of periodic SSB indexes, a UE can determine a set of periodic SSB indexes based on a reference signal (RS) used during an initial access procedure, and / or a UE can determine a set of SSB indexes based on spatial relation information for a PUR configuration.

[0029] Some inactive state beam switching and / or measurement techniques according to the present disclosure involve activating, by a UE, a spatial relation for a PUR response for a physical uplink shared channel (PUSCH), e.g., when a gNodeB (gNB) determines a new spatial relation for the PUSCH. In some embodiments, a UE can perform a reference signal received power (RSRP) measurement on a physical downlink control channel (PDCCH) that schedules a PDSCH that carries a PUR response, a gNB can determine a new spatial relation based on the RSRP measurement, and a beam failure can be declared if all beam and / or SSB indexes fail.

[0030] Some inactive state beam switching and / or measurement techniques according to the present disclosure involve determining a transmission control indicator (TCI) state of a current PDSCH reception. For example, if a time interval between a current physical downlink shared channel (PDSCH) reception and a PDCCH in a current PUR occasion (which can be used to receive a PUR acknowledgement and / or schedule a PUR response) is less than a threshold, a TCI state of the current PDSCH reception can be quasi co-located (QCLed) with a default TCI state of the PDCCH. Otherwise, the TCI state of the current PDSCH reception can be QCLed with an SSB index of a QCL relation used for the current PDCCH reception.

[0031] Some non-active state beam switching and / or measurement techniques according to the present disclosure involve detecting beam failure and / or identifying a new beam based on measuring current and / or candidate beams. For example, a UE can continuously measure the RSRP and / or reference signal received quality (RSRQ) of one or more downlink beams for a set of periodic SSB indices (one of which can be quasi co-located with the corresponding spatial relation information for PUSCH transmissions). The UE can also measure the RSRP and / or RSRQ of one or more downlink beams for a set of candidate SSB indices. The UE can detect beam failure and / or select a new beam based on the measurements.

[0032] In some embodiments, a UE according to the present disclosure can implement one or more beam failure recovery techniques that can be applicable for operating in a non-active state. For example, for a contention-free beam recovery request, a UE can be provided a configuration for a physical random access channel (PRACH) transmission, where the configuration can be provided in a connected state, alternatively, the configuration can be provided in a non-active state through a PUR response message, and / or provided in a non-active state through a SIB message. In some alternative embodiments, a UE can use a contention-based 4-step random access channel (RACH) procedure for beam recovery. For example, a UE can transmit a recovery request using a preamble and RACH occasion that are quasi co-located with a selected candidate beam direction (e.g., spatial relation information for PUSCH).

[0033] In some embodiments, a UE according to the present disclosure can detect beam failure in a non-active state without using reference signals. For example, if a UE does not receive one or more acknowledgements for one or more PUR messages transmitted by the UE, the UE can detect beam failure. Upon detecting beam failure, the UE can attempt to recover the beam, for example, using one or more candidate transmission configuration indicator (TCI) states. Additionally or alternatively, the UE can transition to an RRC connected state to use a beam failure recovery (BFR) procedure in a connected state, and then return to a non-active state. The UE can indicate to the base station that the purpose of transitioning to the connected state is to perform BFR.

[0034] In some embodiments, for example, in response to detecting an overload and / or multi-user interference in an uplink beam shared by multiple UEs, the network can initiate a beam reconfiguration of one or more UEs in an inactive state. For example, in response to detecting an overload or multi-user interference on a beam, a first transmission reception point (TRP) can offload one of the UEs sharing the beam to a second TRP. The first TRP can transmit a downlink transmission (e.g., a PUR response message, a SIB message, etc.) to the UE, causing the UE to transition from the first TRP to the second TRP. The UE can perform a beam management procedure with the second TRP, for example, by selecting a candidate beam with the second TRP. The candidate beam can be selected, for example, based on SSB configuration and CSI-RS measurement configuration.

[0035] Example Embodiments

[0036] Some example embodiments illustrating systems, apparatuses, devices, procedures, methods, etc. in accordance with some possible implementation details of the present disclosure are described herein. These examples are provided to illustrate the principles of the present disclosure, but the principles are not limited to or defined by these embodiments, implementation details, etc. For example, some embodiments can be described in the context of a 5G and / or New Radio (NR) wireless communication system, but the principles can also be applied to any other type of communication system, including 3G, 4G, and / or future generation wireless networks, and / or any other communication system.

[0037] UE transmissions in inactive state

[0038] In some embodiments of a wireless communication system (e.g., a Long Term Evolution (LTE) system), a user equipment (UE) can only transmit in a radio resource control (RRC) connected state. Transitioning from an idle state to a connected state can involve a large amount of traffic between the UE, a radio access network (RAN), and / or a core network (CN), as well as high latency. Even if the UE has a small amount of data to transmit (e.g., one packet), this traffic and latency can be required.

[0039] To reduce the traffic and / or latency involved in allowing a UE to transmit data, some embodiments of a wireless communication system (e.g., an NR system) can implement an RRC_INACTIVE state, which can reduce the overhead and / or latency by not requiring a re-establishment of an RRC connection setup. Instead, after an initial establishment of an RRC connection, a UE can transition to an RRC_INACTIVE state from which the UE can quickly transition back to an RRC_CONNECTED state to transmit data.

[0040] Figure 1A Example embodiments of signaling involved in a legacy (e.g., LTE) IDLE to CONNECTED transition are shown. For comparison, Figure 1B Example embodiments of signaling involved in an NR INACTIVE to CONNECTED transition according to the present disclosure are shown. In Figure 1A and Figure 1B In Figure 1A and Figure 1B It can be apparent that an INACTIVE to CONNECTED transition Figure 1B can be faster and can involve less overhead signaling than a legacy IDLE to CONNECTED transition Figure 1A .

[0041] To further reduce the overhead, latency, and / or power consumption (e.g., for Internet of Things (IoT) devices), some wireless communication systems can allow a UE to transmit a small amount of data while in an INACTIVE state. For example, an NR system implementing a Third Generation Partnership Project (3GPP) Release 17 (Rel-17) work item on NR small data transmission in INACTIVE state can allow a UE to perform a small data transmission (SDT) while in an RRC_INACTIVE state without transitioning to an RRC_CONNECTED state. The work item can include uplink SDT for RACH-based schemes (e.g., 2-step and / or 4-step RACH), and transmission of UL data on preconfigured PUSCH resources (PUR) (e.g., reuse of configured grant Type 1) when a timing advance (TA) is valid.

[0042] Figure 2 Example embodiments of configured grant small data transmission (CG SDT) operation in an INACTIVE state according to the present disclosure are shown. Figure 2 The embodiments shown can be implemented as, for example, an L2 / L3 solution. In this embodiment, the terms CG SDT and PUR transmission can be used interchangeably.

[0043] The UE can be initially configured with CG SDT configuration, e.g., in an RRC suspend message. When TA is valid, the UE 202 can perform a PUR transmission (PUR Tx) 206 to a base station 204 (e.g., gNB, transmission reception point (TRP), etc.) using the configured PUSCH resources.

[0044] Once the initial CG transmission 206 is performed, the UE 202 can monitor for downlink control information (DCI) 208 (e.g., UE-specific DCI or common DCI) for potential PUR response reception 210 and possible subsequent data transmission and / or retransmission. Downlink transmissions can be based on, e.g., dynamic scheduling addressed to UE-specific radio network temporary identifier (RNTI), and uplink transmissions can be based on, e.g., dynamic grant or configured grant addressed to UE-specific RNTI.

[0045] The UE 202 can receive a PUR response message 210, which can include downlink data and possible beam failure recovery (BFR) configuration information. The PUR response message 210 can also include reconfiguration information related to CG SDT. The UE can transmit an acknowledgement / negative acknowledgement (ACK / NACK) 212, e.g., on a physical uplink control channel (PUCCH). As Figure 2 shown, additional CG SDT operations can be performed in the inactive state.

[0046] Messages for beam refinement

[0047] Some wireless systems can implement one or more beam refinement techniques in accordance with the present disclosure. In some embodiments, beam refinement can improve data transfer over a beam, e.g., by narrowing the beam, selecting a beam with better directivity and / or higher gain, etc.

[0048] Figure 3 An overview of an example message sequence for a beam refinement procedure 300 for a UE in RRC INACTIVE state in accordance with the present disclosure is shown. In Figure 3 the time advances to the right. The procedure 300 allows a UE in RRC INACTIVE state to perform an uplink (UL) signal transmission and / or an enhanced downlink (DL) signal reception mechanism (which can be referred to as enhanced Tx). Specifically, the procedure 300 allows the UE to indicate to the gNB which analog narrow beam is optimal and should be used when receiving the enhanced Tx and / or transmitting to the UE.

[0049] The UE obtains system information (SI) at 301 by receiving a system information block 1 (SIB1) that includes information for receiving subsequent SIB messages (which can be referred to as SIB-x). The information received in the SIB1 can include an indication of resources (e.g., time / frequency) for transmitting SIB-x and an indication of resources for requesting SIB-x (e.g., when SIB-x is transmitted on-demand to allow UEs in RRC_INACTIVE state to request SIB-x). SIB-x can be transmitted periodically, semi-periodically, or on-demand in response to a request for SIB-x. The content of SIB-x can include an indication of resources and configuration for subsequent DL RS transmissions and information related to measurement reporting.

[0050] If SIB-x is transmitted periodically or semi-periodically, the UE attempts to receive SIB-x at 303 by monitoring for the periodically or semi-periodically transmitted SIB-x. If SIB-x is transmitted on-demand, the UE transmits a request for SIB-x at 302, and in response to the on-demand request for SIB-x transmitted by the UE at 302, the UE attempts to receive SIB-x at 303.

[0051] If the DL-RS message is transmitted periodically or semi-periodically, the UE can receive a set of downlink reference signals (DL RS) in the DL-RS message at 305. If the DL RS message is transmitted on-demand, the UE can transmit a request for the DL RS message at 304, in which case the UE can receive a set of downlink reference signals (DL RS) in the DL RS message at 305 in response to the on-demand request for the DL RS message. If the UE previously acquired SIB-x, the UE can omit transmitting a request for SIB-x and directly request a set of DL RS signals. The downlink reference signals can be used to perform beam measurements. The DL RS message can include an indication of a collection of sets of RS, where each set corresponds to a particular beam that the UE can measure and indicate to the gNB as a suitable beam for reception. For example, the DL RS message can include an indication of resources (time / frequency) and reference signal type of the DL RS signals to be used.

[0052] At 306, the UE performs beam measurements using the DL RS signals indicated in the DL RS message received at 305. The duration between different RS sets can be specified to account for suitable measurement time. At 307, the UE sends a measurement report to the gNB based on the measurements performed at 306. The content of the measurement report and the resources used to send the measurement report can be indicated in the SIB-x received at 303, in a dedicated UL grant, or in a combination of the SIB-x and the dedicated UL grant.

[0053] Enhanced Tx can be performed at 308. A predetermined time delay between the transmission of the measurement report at 307 and the enhanced Tx at 308 can be defined to allow the gNB to adjust the receive beams accordingly based on the measurement report.

[0054] According to the present disclosure, beam refinement for reduced capability (RedCap) UEs in RRC_INACTIVE state can use a new SIB (which can be referred to as SIB-x) for beam refinement measurement and reporting configuration. In addition, a new e Message 2 (E msg2) can be used to allocate measurement report resources. E msg2 is an evolved message with more functionalities than the traditional msg2. Furthermore, DL RS for beam refinement can be requested by the UE, and the UE beam report can be sent from the UE in RRC_INACTIVE state.

[0055] Figure 4 Another example message sequence for a beam refinement procedure 400 for UEs in RRC_INACTIVE state according to the present disclosure is shown. Time progresses in a downward direction. The beam refinement procedure 400 can be a contention-based procedure or a contention-free procedure.

[0056] Operation Phase 1 (OP 1). The UE requests SIB-x information.

[0057] Variant 1.1. Contention-based procedure

[0058] In the contention-based procedure, an inactive UE can request on-demand SIB-x at 401 by selecting a random access preamble and / or a physical random access channel (PRACH) occasion. The selected PRACH occasion can correspond to the SSB index of the earliest broadcasted with the measured strongest wide beam. The UE’s request can occur periodically or can be event-driven, e.g., based on the UL buffer status for UL transmission of the UE, DL paging of the UE for DL reception, or measured RSRP and / or RSRQ of the current DL beam less than a threshold (due to beam blocking or intra- or inter-beam interference). Upon successful reception of the request at the gNB, the gNB sends an e-message 2 / RAR (extRA Response Window) message to the UE at 402 acknowledging the reception of the request at 401. The e-message 2 is different from the SIB1 message (SIB1 message is a broadcast message from the gNB to all UEs) because this e-message 2 is a message sent by the gNB to a group of UEs sharing the same RA RNTI, not a message sent to all UEs. In response to the e-message 2, the UE then sends a request for r-message in e-message 3. The e-message 3 is a PUSCH transmission from the UE to the gNB. In contrast to the e-message 3, the request sent at 401 is a preamble sequence transmission from the UE to the gNB in conjunction with a PRACH occasion. The gNB acknowledges (ACK) the SIB-x request in message 4 (not shown). At 403, the gNB sends the SIB-x message to the UE.

[0059] Variant 1.2. Contention-free procedure

[0060] In the contention-free procedure, an inactive UE that has been pre-configured with PRACH resources to send SIB-x request sends the SIB-x request at 401. The PRACH resources can be in the form of random access preambles, SIB-x specific PRACH occasions, and / or RedCap UE specific PRACH resources. The UE requests a new on-demand SIB-x by sending the pre-configured PRACH resources to the gNB. The gNB acknowledges (ACK) the request in e-message 2 at 402 and knows that the request for SIB-x is from the specific UE that sent the request. The triggering conditions for the UE request at 401 can be the same as the contention-based procedure. The sending of the SIB X request and acknowledgement is not performed in the contention-free procedure. At 403, the gNB sends the SIB-x message to the UE.

[0061] Operation Phase 1.5 (OP 1.5)

[0062] For both contention-based and contention-free procedures, the resources for beam reporting can be optionally allocated in e-message 2. Each RedCap UE that sends a request for SIB-x in PRACH resources different from other RedCap UEs is allocated resources orthogonal to other allocated resources. In one example embodiment, the resource allocation in e-message 2 can be on-demand, e.g., when a UE sends a request for SIB-x for random access at 401. Alternatively, the resource allocation in e-message 2 can be periodically broadcast to UEs independently of e-message 1 (which uses a different PRACH resource pool than normal message 1 (msg1)) and can include resource grants based on the network remembering the measurement reports of each UE’s past sent specific requests for SIB-x. RedCap UEs are likely to be stationary, so the set of Redcap UEs per cell can not change and the network can relatively easily remember the RACH resources used by each UE. In addition to the resource allocation in e-message 2, the resources for beam reporting can also be optionally allocated in normal message 2 for the traditional RACH procedure when a UE changes from inactive state to connected state. That is, e-message 2 differs from normal message 2 in that it is also able to include resource allocation for beam refinement and reporting.

[0063] Operation Phase 2 (OP 2): Broadcast SIB-x.

[0064] The new SIB-x is broadcast at 403 within the coverage area of the wide beam indicated by the requesting UE (i.e., the SSB index corresponding to the strongest wide beam). Since the broadcast SIB is for each contending UE, the gNB does not perform contention resolution for UEs using the same preamble and PRACH occasion. The SIB-x includes beam measurement and reporting configuration. The content of SIB-x is described as follows. The SIB-x is broadcast a predetermined number of times (i.e., aperiodic), or based on the PRACH resource selected by the UE initiating the request is broadcast a predetermined number of times (i.e., aperiodic). Alternatively, the SIB-x can be broadcast periodically and semi-persistently until the UE explicitly requests to end the broadcast, e.g., when the UE has no data to send in the buffer, or when the UE has completed good beam alignment with the gNB in the past (in the sense that the measured DL RSRP is greater than a threshold).

[0065] Operation Phase 3 (OP 3): Broadcast DL RS.

[0066] Downlink reference signals (DL RS) for beam refinement can be broadcast on-demand. Upon gNB receiving SIB-x request from UE, gNB can perform narrow beam sweeping at 404 by broadcasting DL SSB or DL CSI-RS in various narrow beams within the wide beam indicated by the UE that initiated the request. The narrow beam sweeping uses the configuration indicated in SIB-x. The DL RS can be broadcast continuously periodically (for periodic traffic); a predetermined number of times within a time window; a variable number of times within a time window depending on the PRACH resource selected by the UE requesting SIB-x; a variable number of times within a time window depending on the specific SIB-x request in message 3 in operation phase 1; a variable number of times within a time window depending on the number of UE SIB-x requests accumulated within a time window; or broadcast periodically until the UE requests to end the broadcast.

[0067] Operation Phase 4 (OP 4): Measurement Report.

[0068] At 405, the UE performs UL beam measurement and reports the result to the gNB at 406 using the measurement configuration indicated in SIB-x. The resource for reporting can be allocated in operation phase 2 by allocating orthogonal resources, or by allocating different RACH resources for UEs using message 1 in SIB-x (allocating a set of resources in SIB-x and contended by all UEs intending to report beam measurement). The measurement report can include the C-RNTI of the UE. At 407, the gNB obtains the best DL Tx beam and the best UL Rx beam from the report.

[0069] Variant 4.1. On-demand beam measurement report

[0070] For on-demand beam measurement report, the UE can report beam measurement based on some events, for example, when the UE has UL data to transmit in the buffer, when the UE is paged by the network because the UE has DL data to receive, when beam failure is detected a predetermined number of times by having measured RSRP and / or RSRQ less than a threshold, or based on explicit command from the network via DL DCI or RRC message.

[0071] Variant 4.2. Periodic beam measurement report

[0072] When the UE has been periodically configured by the network, the UE can periodically report beam measurement. In one embodiment, the UE periodically reports beam measurement until the UE enters RRC IDLE state.

[0073] Beam failure recovery

[0074] In some embodiments, at higher frequencies (e.g., above 6 GHz), control and / or data transmissions can be more sensitive to the relatively narrow beamwidths of analog beams. Beam failure can be a relatively short-term and / or dynamic event as opposed to out-of-coverage events. Thus, it can be beneficial to maintain one or more channels (e.g., at least one DL control channel) for connectivity in response to a beam failure event. Thus, some embodiments of a wireless communication system (e.g., an NR system) according to the present disclosure can support dynamic beam failure reporting and / or beam failure recovery procedures.

[0075] An overview of a legacy beam failure recovery procedure for a UE in a connected state according to the present disclosure can operate as follows. Beam failure monitoring can be based on one or more reference signals, such as periodic CSI-RS or SSBs that can be configured by, for example, RRC. A detection metric can be implemented as a number (N) of consecutive PDCCH hypothesis block error rates (BLERs) exceeding a threshold to determine that a beam failure has occurred. A beam failure recovery request can be implemented, for example, with a contention-free UE-specific PRACH channel (e.g., resources and / or preambles). In some embodiments, each resource and / or preamble can be mapped to a new beam identification RS.

[0076] A more detailed example embodiment of a legacy NR beam failure detection and recovery procedure for a UE in a connected state according to the present disclosure can operate as follows. Some embodiments can use terminology that can be similar to that used in the following documents, which are incorporated by reference herein: 3GPP TS 38.211 v15.6.0, “NR; Physical channels and modulation”; 3GPP TS 38.212 v15.6.0, “NR; Multiplexing and Channel coding”; 3GPP TS 38.213 v15.6.0, “NR; Physical Layer Procedures for Control”; 3GPP TS 38.214 v15.6.0, “NR; Physical Layer Procedures for Data”; 3GPP TS 38.321 v15.6.0, “NR; Medium Access Control (MAC) protocol specification”; and 3GPP TS 38.331 v15.6.0, “NR; Radio Resource Control (RRC) Protocol Specification”.

[0077] In the beam failure detection procedure, the UE can be provided with a set of periodic CSI-RS resource configuration indices For example, through failureDetectionResources. The UE can evaluate the radio link quality according to the set of resource configurations relative to a threshold Q out,LR . When the radio link quality is worse than the threshold Q out,LR with a specified periodicity, the physical (PHY) layer can inform one or more higher layers.

[0078] For each beam failure indication from the lower PHY layer, the beamFailureDetectionTimer can be started or restarted, and the BFI_COUNTER can be increased by 1 before the beamFailureDetectionTimer expires. If the BFI_COUNTER >= beamFailureInstanceMaxCount (which can be referred to as C MAX ), the UE can initiate a random access procedure on the primary cell of the primary or secondary cell group (PSCell) or initiate a BFR on a secondary cell (SCell).

[0079] Figure 5 An example embodiment of a beam failure procedure according to the present disclosure is shown, in which when the BFD counter expires, BFI_COUNTER < C MAX .

[0080] Figure 6 An example embodiment of a beam failure procedure according to the present disclosure is shown, in which when the BFD counter expires, BFI_COUNTER >= C MAX .

[0081] To search for the next beam, for a PCell or PSCell, the UE can provide to one or more higher layers, upon request from the one or more higher layers, a periodic CSI-RS configuration index and / or a synchronization signal and / or physical broadcast channel (SS / PBCH) index from the set and a corresponding L1-RSRP measurement greater than or equal to Q out,LR threshold.

[0082] A random access procedure related to beam failure recovery can select a beam and associated RA resources for preamble transmission. For random access response (RAR) reception, if a specific DCI is received within a RAR window, the beam recovery can be considered complete. Otherwise, the random access procedure can be considered not complete and a RA resource selection procedure can be performed after a back-off time. If the RACH procedure for beam recovery is not completed after a certain number of attempts, the RACH procedure can end.

[0083] In the above conventional embodiments, a UE can not perform beam failure and / or recovery in an inactive state. Moreover, the BFR framework in RRC CONNECTED state as described above cannot simply be reused in an inactive state because, for example, it can be intended for downlink operation using downlink reference signals in response to downlink beam failure rather than uplink beam failure. Moreover, the BFR framework requires the UE to be in an RRC connected state.

[0084] Beam failure detection and recovery in an inactive state

[0085] Figure 7 Example embodiments of a method for beam failure detection and recovery for a UE in an inactive state according to the present disclosure are shown. In contrast to conventional BFR procedures, in the embodiments shown, a UE in an inactive state can detect a beam failure and initiate a beam failure recovery procedure at the UE. Figure 7 In the embodiments shown, a UE in an inactive state can detect a beam failure and initiate a beam failure recovery procedure at the UE.

[0086] At operation 702, the UE can receive a BFR configuration for performing beam failure detection and recovery at the UE. The UE can receive the BFR configuration, for example, in a response to a PUR message, in a SIB-x message, by being preconfigured while in an RRC CONNECTED state, or in any other manner. At operation 704, the UE can perform a beam failure detection procedure, for example, by determining whether a beam failure has occurred based on switching beams and measurement results beams based on the BFR configuration. If a beam failure is detected at operation 704, the method can proceed to operation 706, at which the UE can perform a beam failure recovery procedure, for example, by selecting a candidate beam based on the BFR configuration.

[0087] Some more detailed example embodiments of the BFR method according to the present disclosure are provided below. These examples include many implementation details for purposes of illustration. However, the principles are not limited to these or any other specific implementation details. In the embodiments described below, some variables used in the BFR procedure in an inactive state can be adapted from other variables by including “PUR” in the variable name.

[0088] Embodiment 0: UE in RRC_INACTIVE state initiates beam failure recovery with SSB measurement.

[0089] Operation 0.1

[0090] In some embodiments, a UE in RRC_INACTIVE state can be provided a UE-specific SSB measurement configuration in a PUR response message for beam failure recovery, which can be scheduled by DCI transmitted over a PUR search space. Alternatively, a SIB-x can broadcast a common SSB measurement configuration for beam failure recovery to all RRC_INACTIVE UEs in a similar manner as described above in the context of beam refinement. As another alternative, a UE can be preconfigured with SSB measurement configuration when the UE is in RRC_Connected state.

[0091] In some embodiments, for each BWP of the camped cell, a UE can be provided a set of periodic SSB indexes by failureDetectionResources_PUR or beamFailureDetectionResourceList_PUR and a set of periodic SSB indexes by candidateBeamRSList_PUR or candidateBeamResourceList_PUR for radio link quality measurement on the BWP of the camped cell. If the UE is not provided then the UE can determine the set to include one or more periodic SSB indexes that have the same value as the RS index used by the UE to decode message 2 in the initial access procedure. Alternatively, the UE can determine the set to include the SSB index as the spatial relation information of the PUR configuration.

[0092] Operation 0.2

[0093] In some embodiments, when At the time, the PUR PUSCH can only have one active spatial relation information, which can be quasi-co-located (e.g., directly) with one of the SSB-indices-j in the SSB-indices, which can also be quasi-co-located with the PDCCH and PDSCH of the PUR response message to the UE. The spatial relation information of the PUSCH that is quasi-co-located with SSB-indices-1, SSB-indices-2,... SSB-indices-K can be RRC pre-configured and activated via a MAC CE in the PDSCH to the UE, e.g., when the gNB determines a new spatial relation information for the PUSCH for the UE.

[0094] The UE can monitor (in some embodiments, it can continuously monitor) the PDCCH (e.g., CORESET#0) scheduling the PDSCH carrying the PUR response message corresponding to all of the SSB-indices-1, SSB-indices-2,... SSB-indices-j... SSB-indices-K. The UE can perform RSRP measurements and report the measurements to the gNB, e.g., in the PUR PUSCH.

[0095] The gNB can then determine a new spatial relation for the PUSCH by selecting the best SSB index (e.g., the SSB-index with the strongest measured RSRP) and activate it via a MAC CE in the PDSCH. The PDCCH and PDSCH of the PUR response message can then also be updated to a new TCI state that is quasi-co-located with the new SSB-index. If all K beams or SSB indices fail, a beam failure can be declared, for example.

[0096] In some embodiments, independent of the beam failure recovery procedure, if the time interval between the current PDSCH reception and the PDCCH in the current PUR occasion (for receiving an acknowledgement (e.g., ACK / NACK) and / or scheduling a PUR response including activating a new TCI state) is less than a threshold, the TCI state of the current PDSCH reception can be quasi-co-located with the default TCI state of the PDCCH (which is not necessarily quasi-co-located with the current PDCCH reception). One example of the default TCI state of the PDCCH can be the TCI state of the CORESET corresponding to the smallest SSB index among the CORESETs that the UE can have monitored in the latest slot. Another example of the default TCI state of the PDCCH can be the SSB index that is quasi-co-located with the PUR. Otherwise, if the time interval is greater than or equal to the threshold, the TCI state of the current PDSCH reception can be quasi-co-located with the SSB index of the QCL relation for the current PDCCH reception.

[0097] Operation 0.3

[0098] In some embodiments, the UE can continuously measure SSBs (e.g., a set of periodic SSB indices). One of these can be the RSRP and / or RSRQ of the current DL beam (quasi-co-addressable) corresponding spatial relationship information transmitted with PUSCH. The physical layer in the UE can configure the set of resources accordingly. Relative to threshold Q out,LR This is used to assess radio link quality. Simultaneously, the UE can begin measuring the set of SSBs in candidate beams configured in a UE-specific SSB measurement configuration. The UE can identify candidate beams for recovery. For example, the UE can use Q... in,LR Thresholds are applied to data from a set The L1-RSRP measurement is obtained from the SSB resources. Alternatively, the UE can use Q... in,LR Thresholds are applied to data from sources not present in the target population. and L1-RSRP measurements were obtained for all SSB resources in the dataset.

[0099] Operation 0.4

[0100] In some embodiments, the UE may declare a beam failure based on the number of consecutive beam failure instances exceeding a configured value, wherein, for example, a beam failure instance may be determined as a measured L1-RSRP and / or RSRQ being lower than a configured threshold Q. out,LR rlmInSyncOutOfSyncThreshold_PUR. For example, in non-discontinuous reception (non-DRX) mode operation, when the UE uses the set of data to evaluate radio link quality. The radio link quality of all corresponding resource configurations is worse than the threshold Q. out,LR In this case, the physical layer in the UE can provide indications to one or more higher layers. For example, when the radio link quality is worse than a threshold Q with a specific period. out,LR At that time, the physical layer can notify one or more higher layers, where the specific period is a set that the UE can use to assess the radio link quality. The maximum value between the shortest period and a fixed time period (e.g., 2 milliseconds) in the periodic SSB on the PCell is used to determine this. In DRX mode operation, when the radio link quality is worse than a threshold Q with a predetermined period (e.g., the period described in TS 38.133), this is used. out,LR At that time, the physical layer can provide instructions to one or more higher layers.

[0101] If the MAC layer receives a beam failure instance indication, the MAC layer can perform the following operations:

[0102] (1) Start or restart beamFailureDetectionTimer;

[0103] (2) Increment BFI_COUNTER by 1;

[0104] (3) If BFI_COUNTER>=beamFailureInstanceMaxCount, then initiate a random access procedure on the Pcell or initiate a BFR on the Scell;

[0105] (4) If beamFailureDetectionTimer expires or the random access procedure is successfully completed, BFI_COUNTER is reset to 0, beamFailureRecoveryTimer is stopped, and the beam failure recovery process is considered to be complete.

[0106] Operation 0.5

[0107] In some embodiments, when a beam failure is declared, the UE may provide a set of information to one or more higher layers upon request from one or more higher layers. The periodic SSB index and greater than or equal to Q in,LR The corresponding L1-RSRP measurement for the threshold.

[0108] Operation 0.6

[0109] In some embodiments, for a contention-free beam recovery request, the CORESET can be provided to the UE via a link to the search space set for monitoring the PDCCH in that CORESET, provided by recoverySearchSpaceId_PUR. recoverySearchSpaceId_PUR can be pre-configured when the UE is in the RRC_Connected state. Alternatively, recoverySearchSpaceId_PUR can be configured via a PUR response message in the RRC_Inactive state. Alternatively, recoverySearchSpaceId_PUR can be configured via SIB-x in the RRC_Inactive state, for example, in a manner similar to that described above in the context of beam improvement. Alternatively, the UE can monitor the PDCCH linked to CORESET0 corresponding to the SSB index of the PRACH sent by the UE.

[0110] Operation 0.7

[0111] In some embodiments, for contention-free beam recovery request, the UE can select a new beam at the MAC layer. For example, the UE can transmit a recovery request to the TRP using a preamble and RACH occasion that is quasi co-located with the selected candidate beam direction. For example, the UE can be provided a configuration for PRACH transmission by PRACH-ResourceDedicatedBFR_PUR, which can be preconfigured via a PUR response message or via a SIB-x message when the UE is in RRC_Connected state or in RRC_INACTIVE state, e.g., in a similar manner as described above in the context of beam refinement. For a PRACH transmission in slot n, and according to the antenna port quasi co-location parameters associated with the periodic SSB with index q new provided by one or more higher layers, the UE can monitor one or more PDCCH in the search space set provided by recoverySearchSpaceId_PUR starting from slot n+4 within a window configured by BeamFailureRecoveryConfig_PUR for detecting DCI format with CRC scrambled by C-RNTI or MCS-C-RNTI. BeamFailureRecoveryConfig_PUR can be preconfigured when the UE is in RRC_Connected state or configured via a PUR response message when the UE is in RRC_INACTIVE state. For PDCCH monitoring in the search space set provided by recoverySearchSpaceId-PUR and for corresponding PDSCH reception, the UE can assume the same antenna port quasi co-location parameters as the antenna port quasi co-location parameters associated with index q new until the UE receives an activation for TCI states from one or more higher layers or any of parameters tci-StatesPDCCH-ToAddList and / or tci-StatesPDCCH-ToReleaseList.

[0112] Operation 0.8

[0113] In some embodiments, for contention-free beam recovery request, the random access procedure can be successfully completed if a DCI is detected in the search space set recoverySearchSpaceId-PUR. The UE can transmit a recovery request to the TRP using a preamble and RACH occasion that is quasi co-located with the selected SSB index q newPUSCH quasi co-located. If the ra-ResponseWindow configured in BeamFailureRecoveryConfig PUR expires and no DCI is received, the UE can perform the following operations:

[0114] (1) Random access response reception can be considered unsuccessful;

[0115] (2) Increase PREAMBLE_TRANSMISSION_COUNTER by 1;

[0116] (3) If PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1 (where preambleTransMax is configured in BeamFailureRecoveryConfig PUR), the UE can:

[0117] (a) Declare a RA error and report the error to one or more higher layers.

[0118] Otherwise, the UE can:

[0119] (b) (1) Consider the random access procedure not completed and start a backoff procedure; and

[0120] (b) (2) After backoff, perform a random access resource selection procedure.

[0121] Operation 0.9

[0122] In some embodiments, for a contention-based 4-step RACH procedure, the UE can select a new beam at the MAC layer. The UE can transmit a recovery request to the TRP using a preamble and RACH occasion quasi co-located with the selected candidate beam direction (e.g., spatial relation information for PUSCH). The UE can then perform a procedure such as shown in Appendix 1.

[0123] Embodiment 1: UE initiates beam failure recovery with CSI-RS measurement in RRC_INACTIVE state.

[0124] Operation 1.1

[0125] In some embodiments, based on the NR PUR framework in the context, a UE in RRC_INACTIVE state can obtain a UE-specific CSI-RS measurement configuration in a PUR response message (e.g., scheduled by DCI transmitted on the PUR search space) for beam refinement and beam failure recovery. Alternatively, a SIB-x can broadcast a common CSI-RS measurement configuration for beam failure recovery to all RRC_INACTIVE UEs in a similar manner as described above in the context of beam refinement. Alternatively, a UE can also be preconfigured with the RS measurement configuration when the UE is in RRC_Connected state.

[0126] In some embodiments, for each BWP of the camped cell, the UE can be provided a set of periodic CSI-RS resource configuration indices by failureDetectionResources_PUR or beamFailureDetectionResourceList_PUR and a set of periodic CSI-RS resource configuration indices by candidateBeamRSList_PUR or candidateBeamResourceList_PUR for radio link quality measurement on the BWP of the camped cell. If the UE is not provided then the UE can determine the set to include periodic CSI-RS resource configuration indices with the same value as the RS indices in the set of RS indicated by the TCI state (TCI-State) of the corresponding CORESET that the UE can use to monitor PDCCH on the PUR search space. The TCI state of the corresponding CORESET that the UE uses to monitor PDCCH on the PUR search space can be preconfigured when the UE is in RRC_Connected state.

[0127] Operation 1.2

[0128] In some embodiments, when At this time, it can be assumed that the PUR PUSCH can only have one active spatial relation information that is quasi co-located (e.g., directly quasi co-located) with one of the CSI-RS indexes (e.g., CSI-RS-Index-j) that can also be quasi co-located with the PDCCH and PDSCH of the PUR response message to the UE. The spatial relation information of the PUSCH that is quasi co-located with CSI-RS-Index-1, CSI-RS-Index-2…CSI-RS-Index-K can be RRC pre-configured and can be activated via a MAC CE in the PDSCH transmission to the UE, e.g., when the gNB determines a new spatial relation information for the PUSCH for the UE.

[0129] For the set The UE can evaluate the radio link quality only from the periodic CSI-RS resource configuration that can be quasi co-located with the DM-RS of the PDCCH reception that the UE monitors to schedule the PDSCH carrying the PUR response message. Therefore, the network can configure additional CORESETs to increase the TCI states that the UE can evaluate in the set. The UE can perform RSRP measurements of the CSI-RS indexes and report the measurements to the gNB in the PUR PUSCH.

[0130] The gNB can determine a new spatial relation for the PUSCH by selecting the best CSI-RS-Index (e.g., the CSI-RS-Index with the strongest measured RSRP) and activate it via a MAC CE in the PDSCH. The PDCCH and PDSCH of the PUR response message can also be updated to a new TCI state that is quasi co-located with the new CSI-RS-Index. For example, if all K beams or CSI-RS-Indexes fail, then a beam failure is declared.

[0131] In some embodiments, independent of the beam failure recovery procedure, the TCI state of the current PDSCH reception can be quasi co-located with a default TCI state of the PDCCH (used to receive ACK / NACK and / or schedule a PUR response including activating a new TCI state) in the current PUR occasion if a time interval between the current PDSCH reception and the PDCCH is less than a threshold. One example of the default TCI state of the PDCCH can be a TCI state of a CORESET that can have a quasi co-location with a smallest CSI-RS index among CORESETs that the UE can have monitored in the latest slot. Alternatively, the default TCI state of the PDCCH can be a TCI state of a CORESET with a smallest index. Another example of the default TCI state of the PDCCH can be a CSI-RS index that is quasi co-located with the PUR. Otherwise, if the time interval is greater than or equal to the threshold, the TCI state of the current PDSCH reception can be quasi co-located with a CSI-RS index of a QCL relationship for the current PDCCH reception.

[0132] Operation 1.3

[0133] In some embodiments, the UE can measure (e.g., can continuously measure) CSI-RS, e.g., a set of periodic CSI-RS resource configuration indices One of the RSRP and / or RSRQ of the current DL beam that can be quasi co-located with a corresponding spatial relation information of the PUSCH transmission. The physical layer in the UE can evaluate the radio link quality according to the set of resource configurations relative to a threshold Q out,LR For the set of resource configurations The UE can evaluate the radio link quality only according to periodic CSI-RS resource configurations on a PCell or a PSCell that can be quasi co-located with the PUSCH transmission of the UE.

[0134] Operation 1.4

[0135] In some embodiments, simultaneously, the UE can start measuring a set of CSI-RS in candidate beams configured in the UE-specific CSI-RS measurement configuration. The UE can identify a candidate beam for recovery. For example, after scaling the corresponding CSI-RS received power by a value provided by powerControlOffsetSS, the UE can apply a Q in,LR threshold to the L1-RSRP measurement obtained for the CSI-RS from the set According to a request from one or more higher layers, the UE can provide to the one or more higher layers a periodic CSI-RS configuration index from the set and can be greater than or equal to Qin,LR corresponding L1-RSRP measurement of the threshold.

[0136] Operation 1.5

[0137] In some embodiments, the UE can declare beam failure based on the number of consecutive beam failure instances exceeding a configured value, where one beam failure instance can be defined as the measured L1-RSRP and / or RSRQ being below a configured threshold Q out,LR rlmInSyncOutOfSyncThreshold_PUR. For example, in non-DRX mode operation, when the radio link quality of all corresponding resource configurations in the set of resources used by the UE to evaluate the radio link quality is worse than the threshold Q out,LR , the physical layer in the UE can provide an indication to one or more higher layers. When the radio link quality is worse than the threshold Q out,LR with a certain periodicity determined by the maximum of the shortest periodicity among the periodic CSI-RS configurations on the PCell or PSCell in the set of resources used by the UE to evaluate the radio link quality and a fixed time (e.g., 2 ms), the physical layer can notify one or more higher layers. In DRX mode operation, when the radio link quality is worse than the threshold Q out,LR with a predetermined periodicity (e.g., a period as specified in TS 38.133), the physical layer can provide an indication to one or more higher layers.

[0138] If the MAC layer receives a beam failure instance indication, the MAC layer can perform the following operations:

[0139] (1) start or restart the beamFailureDetectionTimer;

[0140] (2) increase the BFI_COUNTER by 1;

[0141] (3) if the BFI_COUNTER >= beamFailureInstanceMaxCount, initiate a random access procedure on the Pcell or a BFR procedure on the Scell;

[0142] (4) if the beamFailureDetectionTimer expires or the random access procedure is successfully completed, reset the BFI_COUNTER to 0, stop the beamFailureRecoveryTimer, and consider the beam failure recovery procedure completed.

[0143] Operation 1.6

[0144] In some embodiments, the UE can be provided with the CORESET through a link to a search space set provided by recoverySearchSpaceId PUR for monitoring PDCCH in the CORESET. The recoverySearchSpaceId PUR can be pre-configured when the UE is in RRC_Connected state. Or the recoverySearchSpaceId PUR can be configured through a PUR response message in RRC_Inactive state. Or the recoverySearchSpaceId PUR can be configured through a SIB-x message in RRC_Inactive state in a similar way as described above in the context of beam refinement.

[0145] Operation 1.7

[0146] In some embodiments, the UE can select a new beam at the MAC layer. The UE can make a beam failure recovery request using option 1 contention-free 2-step contention-free random access. For example, the UE can transmit a recovery request to a transmission reception point (TRP) using a preamble and a RACH occasion that are quasi co-located with the selected candidate beam direction. For example, the UE can be provided with a configuration for PRACH transmission through PRACH-ResourceDedicatedBFR PUR, which can be pre-configured when the UE is in RRC_Connected state or in RRC_INACTIVE state via a PUR response message or via a SIB-x message in a similar way as described above in the context of beam refinement. For a PRACH transmission in slot n, and according to an antenna port quasi co-location parameter associated with a periodic CSI-RS resource configuration with an index q new , the UE can monitor PDCCH in a search space set provided by recoverySearchSpaceId PUR within a window configured by BeamFailureRecoveryConfig PUR starting from slot n+4 for detecting DCI format with CRC scrambled by C-RNTI or MCS-C-RNTI. The BeamFailureRecoveryConfig PUR can be pre-configured when the UE is in RRC_Connected state or configured via a PUR response message when the UE is in RRC_INACTIVE state. For PDCCH monitoring in the search space set provided by recoverySearchSpaceId PUR and for corresponding PDSCH reception, the UE can assume the same spatial domain transmission filter as used for reception of the PDCCH with CRC scrambled by C-RNTI or MCS-C-RNTI. newThe associated antenna port quasi co-location parameters are the same as the antenna port quasi co-location parameters until the UE receives one or more higher layers for TCI states or any of the parameters tci-StatesPDCCH-ToAddList and / or tci-StatesPDCCH-ToReleaseList.

[0147] Operation 1.8

[0148] In some embodiments, if DCI is detected in the search space set recoverySearchSpaceId-PUR, the random access procedure can be considered to be successfully completed. The UE can transmit a CSI-RS-index q new PUSCH quasi co-located. If the ra-ResponseWindow configured in BeamFailureRecoveryConfig PUR expires and no DCI is received, the UE can perform the following operations:

[0149] (1) Random access response reception can be considered unsuccessful;

[0150] (2) PREAMBLE_TRANSMISSION_COUNTER is increased by 1;

[0151] (3) If PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1 (where preambleTransMax is configured in BeamFailureRecoveryConfig PUR), the UE can:

[0152] (a) declare a RA error and report the error to one or more higher layers.

[0153] Otherwise, the UE can:

[0154] (b) (1) consider that the random access procedure is not completed and start the backoff procedure; and

[0155] (b) (2) after backoff, perform the random access resource selection procedure.

[0156] Operation 1.9

[0157] In some embodiments, the UE can select a new beam at the MAC layer. The UE can use option 2, contention-based 4-step RACH procedure to make a beam failure recovery request. For example, the UE can use a preamble and RACH occasion (e.g., spatial relation information for PUSCH) quasi co-located with the selected candidate beam direction to transmit a recovery request to the TRP. Then, the UE can perform a procedure such as shown in Appendix 2.

[0158] Embodiment 2: UE initiated beam failure recovery without beam RS measurement in RRC_INACTIVE state, method 1.

[0159] Operation 2.1

[0160] In some embodiments, as part of the initial configuration of NR PUR transmission, the UE can be preconfigured with one TCI state for PUSCH transmission and / or PDCCH reception in NR PUR search space when the UE is in RRC_Connected state, and a set of candidate TCI states for beam failure recovery (e.g., fast beam failure recovery) in RRC_INACTIVE state. The candidate TCI states can be obtained based on the legacy NR beam management procedure, where a set of candidate SSB wide beams with the strongest measured RSRP or RSRQ can be selected and stored.

[0161] Operation 2.2

[0162] In some embodiments, the UE can perform PUR transmission to gNB periodically in RRC_INACTIVE state. If the UE does not receive ACK / NACK in PDCCH over PUR search space (e.g., over M consecutive PUR search occasions), the UE can declare beam failure at MAC layer. For example, when the UE does not receive ACK / NACK from gNB within a specified time window in PUR occasions, the physical layer in the UE can provide an indication to one or more higher layers. At MAC layer, if the MAC layer receives the beam failure instance indication, the MAC layer can perform the following operations:

[0163] (1) start or restart beamFailureDetectionTimer;

[0164] (2) increase BFI_COUNTER by 1;

[0165] (3) if BFI_COUNTER >= beamFailureInstanceMaxCount, initiate random access procedure on Pcell or BFR on Scell:

[0166] (4) if beamFailureDetectionTimer expires or random access procedure is successfully completed, reset BFI_COUNTER to 0, stop beamFailureRecoveryTimer, and consider the beam failure recovery procedure completed.

[0167] Operation 2.3

[0168] In some embodiments, the CORESET can be provided to the UE through a link to a search space set provided by recoverySearchSpaceId PUR for monitoring PDCCH in the CORESET. The recoverySearchSpaceId PUR can be preconfigured when the UE is in RRC_Connected state. Or the recoverySearchSpaceId PUR can be configured by a PUR response message in RRC_Inactive state. Or the recoverySearchSpaceId PUR can be configured by a SIB-x message in RRC_Inactive state in a similar way as described above in the context of beam refinement.

[0169] Operation 2.4

[0170] In some embodiments, the UE can select a candidate TCI state from a preconfigured list of candidate TCI states stored in the UE at the MAC layer. The UE can make a beam failure recovery request using contention-free 2-step contention-free random access. For example, the UE can transmit a recovery request to the TRP using a preamble and a RACH occasion that are quasi co-located with the selected candidate beam spatial filter information. For example, the UE can be provided a configuration for PRACH transmission by PRACH-ResourceDedicatedBFR_PUR, which can be preconfigured while the UE is in RRC_Connected state, or in RRC_INACTIVE state via a PUR response message. For a PRACH transmission in slot n, and according to the antenna port quasi co-location parameters associated with the new selected TCI state provided by one or more higher layers, the UE can monitor PDCCH in the search space set provided by recoverySearchSpaceId_PUR starting from slot n+4 within a window configured by BeamFailureRecoveryConfig_PUR for detecting DCI format(s) with CRC scrambled by C-RNTI or MCS-C-RNTI. BeamFailureRecoveryConfig_PUR can be preconfigured while the UE is in RRC_Connected state, or configured via a PUR response message while the UE is in RRC_INACTIVE state. For PDCCH monitoring in the search space set provided by recoverySearchSpaceId-PUR and for corresponding PDSCH reception, the UE can assume the same antenna port quasi co-location parameters as the new selected TCI state until the UE receives an activation for the TCI state by one or more higher layers.

[0171] Operation 2.5

[0172] In some embodiments, if a DCI is detected in the search space set recoverySearchSpaceId-PUR, the random access procedure can be considered to be successfully completed. The UE can transmit PUSCH that is quasi co-located with the previous PDCCH reception of the DCI. If the ra-ResponseWindow configured in BeamFailureRecoveryConfig_PUR expires and no DCI is received, the UE can perform the following operations:

[0173] (1) consider the random access response reception unsuccessful;

[0174] (2) increase PREAMBLE_TRANSMISSION_COUNTER by 1;

[0175] (3) If PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1 (preambleTransMax is configured in BeamFailureRecoveryConfig PUR), the UE can perform the following operations:

[0176] (a) If (there are still pre-configured new TCI states remaining stored in the UE):

[0177] (i) The UE can return to operation 2.4 to select the next candidate beam with a new TCI state and continue the 2-step contention-free RACH procedure;

[0178] Otherwise:

[0179] (ii) Or the UE declares RA failure and reports to higher layers; or

[0180] (iii) The UE falls back to RACH and moves to RRC_Connected state to perform a legacy beam recovery procedure; or

[0181] (iv) The UE falls back to the beam recovery procedure of embodiment 1;

[0182] Otherwise:

[0183] (b1) The random access procedure is considered not completed, and the UE starts a back-off procedure; and

[0184] (b2) The UE performs a random access resource selection procedure after back-off.

[0185] Embodiment 3: Beam failure recovery initiated by the UE in RRC_INACTIVE state without beam RS measurement, method 2.

[0186] Operation 3.1

[0187] In some embodiments, the UE can periodically perform PUR transmission to the gNB in RRC_INACTIVE state. If the UE does not receive ACK / NACK in PDCCH on PUR search space in M consecutive PUR search occasions, the UE can declare beam failure at MAC layer. For example, when the UE does not receive ACK / NACK from the gNB within a time window in PUR occasions, the physical layer in the UE can provide an indication to one or more higher layers. At the MAC layer, if the MAC layer receives the beam failure instance indication, the MAC layer can perform the following operations:

[0188] (1) start or restart the beamFailureDetectionTimer;

[0189] (2) increment BFI_COUNTER by 1;

[0190] (3) if BFI_COUNTER >= beamFailureInstanceMaxCount, initiate a random access procedure on the Pcell or initiate BFR on the Scell:

[0191] (4) if the beamFailureDetectionTimer expires or the random access procedure is successfully completed, reset BFI_COUNTER to 0, stop the beamFailureRecoveryTimer, and consider the beam failure recovery procedure completed.

[0192] Operation 3.2

[0193] In some embodiments, once the UE declares beam failure, it can perform a RACH procedure and transition to RRC_Connected state to perform a beam improvement procedure as described above. In the RACH procedure, the UE can select a specific preamble resource to indicate to the network the purpose of “beam recovery in RRC_Connected state”. This is because the UE was not able to successfully perform the beam failure recovery procedure in the inactive state. Alternatively, the UE can also indicate the purpose of “beam recovery in RRC_Connected state” to the network in the message 3 of the RACH procedure.

[0194] Operation 3.3

[0195] In some embodiments, once the UE is in RRC_Connected state, the UE can be RRC configured with RS measurement configuration for selecting candidate beams for beam improvement. The UE can select a candidate beam and complete a traditional beam improvement procedure with the network. Once the beam improvement is completed, the UE can transition back to RRC_INACTIVE state and perform NRPUR transmission using the new beam.

[0196] Embodiment 4: Network (NW) initiated beam reconfiguration for load balancing and / or interference management, method 1.

[0197] Operation 4.1

[0198] In some embodiments, the TRP can detect overload or multi-user interference in the current UL beam shared by multiple PUR UEs. The TRP can offload one or more of the UEs to another TRP, e.g., for load balancing and / or interference mitigation.

[0199] Operation 4.2

[0200] In some embodiments, by using SSB configuration and new or old UE-specific or common CSI-RS measurement configuration, a TRP can configure a selected one of the UEs in a PUR response message or SIB-x message to perform beam management steps with another TRP. The UE can identify candidate beams (e.g., narrow beams) to another TRP for offloading and / or interference management. For example, the UE can perform P1, P2, and P3 operations of NR Rel-15 beam management steps to select a new beam (e.g., for a new TRP). For example, the UE can first perform SSB measurement and select the best SSB index with the strongest RSRP value. Then, it can inform the network of the newly selected SSB index and spatial relation information of PUSCH associated with the SSB index, e.g., via contention-free 2-step RACH or contention-based 4-step RACH. Then, the UE can perform beam refinement based on configured CSI-RS indices and select the best CSI-RS index that gives the strongest measured RSRP value.

[0201] Operation 4.3

[0202] In some embodiments, a CORESET can be provided to the UE through a link to a search space set for monitoring PDCCH in that CORESET provided by ReconfigSearchSpaceId PUR. ReconfigSearchSpaceId PUR can be pre-configured when the UE is in RRC_Connected state. Or ReconfigSearchSpaceId PUR can be configured by a PUR response message in RRC_Inactive state. Or ReconfigSearchSpaceId PUR can be configured by a SIB-x message in RRC_Inactive state in a similar way as described above in the context of beam refinement.

[0203] Operation 4.4

[0204] In some embodiments, the UE can make a beam reconfiguration request using contention-free 2-step contention-free random access. For example, the UE can send a reconfiguration request to another TRP using a preamble and RACH occasion that are quasi co-located with the selected candidate beam direction or selected CSI-RS index.

[0205] Operation 4.5

[0206] In some embodiments, another TRP can respond to the UE by sending a response message via PDCCH in a PUR search space that is quasi co-located with the RS associated with the selected candidate beam included in the request.

[0207] Embodiment 5: Network initiated beam reconfiguration for load balancing and / or interference management, method 2.

[0208] Operation 5.1

[0209] In some embodiments, a TRP can detect overload or multi-user interference in a current UL beam shared by multiple PUR UEs. The TRP can offload one or more of the UEs to another TRP, e.g., for load balancing and / or interference mitigation.

[0210] Operation 5.2

[0211] In some embodiments, a TRP can trigger a selected one of the UEs in RRC-INACTIVE state in a DCI in a PUR framework to reconfigure another candidate beam for PUR. The UE can then perform a beam management procedure using a preconfigured SSB configuration and UE-specific CSI-RS measurement configuration. The UE can identify a candidate beam (e.g., a narrow beam) to another TRP for offloading and / or interference management. For example, the UE can first perform SSB measurement and select the best SSB index with the strongest RSRP value. The UE can then inform the network of the newly selected SSB index and spatial relation information of PUSCH associated with the SSB index via contention-free 2-step RACH or contention-based 4-step RACH. The UE can then perform a beam refinement procedure based on configured CSI-RS indices and select the best CSI-RS index that gives the strongest measured RSRP value.

[0212] Operation 5.3

[0213] In some embodiments, the UE can make a beam reconfiguration request using contention-free 2-step contention-free random access. For example, the UE can send a reconfiguration request to another TRP using a preamble and RACH occasion that are quasi co-located with the selected candidate beam direction or selected CSI-RS index.

[0214] Operation 5.4

[0215] In some embodiments, the other TRP can respond to the UE by sending a response message via PDCCH in a PUR search space that is quasi co-located with the RS associated with the selected candidate beam included in the request.

[0216] Embodiment 6: Network initiated beam reconfiguration for load balancing and / or interference management, method 3.

[0217] Operation 6.1

[0218] In some embodiments, the TRP can detect overload or multi-user interference in the current UL beam shared by multiple PUR UEs. The TRP can offload one or more of the UEs to another TRP, e.g., for load balancing and / or interference mitigation.

[0219] Operation 6.2

[0220] In some embodiments, the TRP can reconfigure the selected one of the UEs in RRC_INACTIVE state with another candidate beam selected by the network or a new TCI state selected by the network for PUR in a DCI or a PUR response message in the PUR framework for offloading and / or interference management.

[0221] Operation 6.3

[0222] In some embodiments, the UE can send an acknowledgement to the TRP via a MAC CE or an RRC message.

[0223] Additional fallback procedures

[0224] In some embodiments, as an alternative to fallback due to beam failure, the UE can measure downlink CRS RS on the PDSCH of the PUR response message. If the RSRP value is below a threshold for a consecutive number of PUR response messages, the UE can detect beam failure. The UE can request beam recovery through another preconfigured candidate beam from the gNB via a two-step contention-free request. If beam failure still occurs (e.g., via UE downlink measurements), the UE can transition to RACH mode.

[0225] In some embodiments, as another alternative to fallback due to beam failure, if there is no PDSCH transmission (e.g., PDCCH only), and if the UE does not receive an ACK / NACK from the gNB within a specified time window, the UE can assume beam failure and reconfigure an alternative UL beam for UL beam recovery and request to the gNB via a two-step contention-free procedure. If the gNB detects UL beam failure, the gNB can respond by acknowledging the alternative beam in a DCI on the alternative beam. Otherwise, the gNB can reject the recovery request from the UE and reconfigure one or more other parameters (e.g., Tx power) in a DCI on the alternative beam. The UE can then continue to use the original beam with the new configured parameters. If beam failure still occurs, the UE can autonomously fallback to RACH mode.

[0226] User equipment

[0227] Figure 8 An example embodiment of a user equipment (UE) according to the present disclosure is shown. Figure 8The illustrated embodiment 800 can include a radio transceiver 802 and a controller 804, which can control operation of the transceiver 802 and / or any other components in the UE 800. The UE 800 can be used, e.g., to implement any of the functionality described in this disclosure. The transceiver 802 can transmit / receive one or more signals to / from a base station and can include interface units for such transmission / reception. The controller 804 can include, e.g., one or more processors 806 and a memory 808, which can store instructions for the one or more processors 806 to execute to implement any of the functionality described in this disclosure. For example, the UE 800 and / or the controller 804 can be used to implement functionality related to a UE performing a beam failure detection and / or recovery procedure in an inactive state.

[0228] Base station

[0229] Figure 9 An example embodiment of a base station according to the present disclosure is shown. Figure 9 The illustrated embodiment 900 can include a radio transceiver 902 and a controller 904, which can control operation of the transceiver 902 and / or any other components in the base station 900. The base station 900 can be used, e.g., to implement any of the functionality described in this disclosure. The transceiver 902 can transmit / receive one or more signals to / from a user equipment and can include interface units for such transmission / reception. The controller 904 can include, e.g., one or more processors 906 and a memory 908, which can store instructions for the one or more processors 906 to execute to implement any of the base station functionality described in this disclosure. For example, the base station 900 and / or the controller 904 can be used to implement functionality related to network initiated beam reconfiguration for load balancing and / or interference management, etc.

[0230] In Figure 8 And Figure 9In the illustrated embodiment, transceivers 802 and 902 can be implemented with various components such as amplifiers, filters, modulators and / or demodulators, A / D and / or D / A converters, antennas, switches, phase shifters, detectors, couplers, conductors, transmission lines, etc. to receive and / or transmit RF signals. Controllers 804 and 904 can be implemented with hardware, software, and / or any combination thereof. For example, all or part of the hardware implementation can include combinational logic, sequential logic, timers, counters, registers, gate arrays, amplifiers, synthesizers, multiplexers, modulators, demodulators, filters, vector processors, complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), systems on a chip (SOCs), state machines, data converters such as ADCs and DACs, etc. All or part of the software implementation can include one or more processor cores, memory, program and / or data storage, etc., which can be local and / or remote, and which can be programmed to execute instructions to perform one or more functions of the controller. Some embodiments can include one or more CPUs executing instructions stored in any type of memory, such as complex instruction set computer (CISC) processors such as the x86 processor from Intel® Corporation and / or reduced instruction set computer (RISC) processors such as the ARM processor, etc.

[0231] Additional Embodiments

[0232] Figure 10 An embodiment of a method for beam failure recovery in a communication network according to the present disclosure is shown. The method can begin at operation 1002. At operation 1004, the method can detect, at a user equipment (UE) in an inactive state, a beam failure based on a downlink transmission. At operation 1006, the method can perform, at the UE in the inactive state, a beam failure recovery (BFR) procedure based on detecting the beam failure. The method can end at operation 1008.

[0233] Figure 11 An embodiment of a method for beam failure recovery in a communication network according to the present disclosure is shown. The method can begin at operation 1102. At operation 1104, the method can detect, at a first transmission-reception point (TRP), a performance condition in an uplink beam shared by a first user equipment (UE) in an inactive state and a second UE in an inactive state. At operation 1106, the method can transmit, from the first TRP to the first UE, a downlink transmission based on detecting the performance condition. At operation 1108, the method can perform, at the first UE, a transition procedure from the first TRP to a second TRP based on the downlink transmission. The method can end at operation 1110.

[0234] InFigures 10-11 The illustrated components and / or operations in the embodiments illustrated and herein described are merely exemplary. Some embodiments can involve additional components and / or operations not depicted, and some embodiments can omit certain components and / or operations. Further, the illustrated arrangements of components and / or the order in which operations are implemented can vary in some embodiments. Although some components can be illustrated as separate components, in some embodiments, some components can be integrated into a single component, and / or some components can be implemented using multiple components.

[0235] Embodiments disclosed herein can be described in the context of various implementation details, but the principles of the present disclosure are not limited to these or any other specific details. Some functions have been described as being implemented by particular components, but in other embodiments, the functions can be distributed among different systems and components in different locations. References to components or elements can refer only to a portion of that component or element. The use of terms such as “first” and “second” to modify a reference to a thing can only be to distinguish that thing from another thing, and can not indicate any temporal or chronological order, unless otherwise evident from the context. A reference to a first thing can not imply the existence of a second thing. In addition, various details and embodiments described above can be combined to produce additional embodiments in accordance with the principles of the present patent disclosure. Various organizational aids can be provided for convenience, such as chapter headings and the like, but the subject matter arranged according to these aids and the principles of the present disclosure are not limited by these organizational aids.

[0236] Since the inventive principles of the present patent disclosure can be modified in arrangement and detail without departing from the inventive concepts, such alterations and modifications are considered to fall within the scope of the appended claims.

[0237] Appendix 1

[0238] 1> if the random access procedure is initiated for beam failure recovery; and

[0239] 1> if the beamFailureRecoveryTimer is running or not configured; and

[0240] 1> if at least one of the SSB indexes among the SSB indexes in the candidateBeamRSList with SS-RSRP above rsrp-ThresholdSSB is available:

[0241] 2> select the SSB-RS among the SSB-RS in the candidateBeamRSList with the SSB index with SS-RSRP above rsrp-ThresholdSSB-RS

[0242] 3> set PREAMBLE_INDEX to the ra-PreambleIndex corresponding to the selected SSB from the set of random access preambles used for beam failure recovery request.

[0243] 1> perform the random access preamble transmission procedure.

[0244] 1> RAR reception: legacy message 2 reception

[0245] 1> the UE sends a message 3 to the gNB, where the message includes an indication of beam failure recovery in RRC_INACTIVE state.

[0246] Contention resolution

[0247] 1> if a notification of reception of a PDCCH transmission on SpCell is received from lower layers:

[0248] 1> if C-RNTI MAC CE is included in Msg3:

[0249] 3> if the random access procedure was initiated for beam failure recovery and the PDCCH transmission addressed to C-RNTI;

[0250] 4> consider this contention resolution successful;

[0251] 4> stop ra-ContentionResolutionTimer;

[0252] 4> discard TEMPORARY_C-RNTI;

[0253] 4> consider the random access procedure successfully completed.

[0254] 4> if msg 4 includes an indication that "UE remains in RRC_INACTIVE state"

[0255] From NW

[0256] UE stays in RRC_INACTIVE state;

[0257] Else, the UE enters RRC_Connected state and starts RRC connection establishment.

[0258] 1> if ra-ContentionResolutionTimer expires:

[0259] 2> discard TEMPORARY_C-RNTI;

[0260] 2> consider the contention resolution unsuccessful.

[0261] 1> if contention resolution is considered not to be successful:

[0262] 2> flush the HARQ buffer used to transmit the MAC PDU in Msg3 buffer;

[0263] 2> increase PREAMBLE_TRANSMISSION_COUNTER by 1;

[0264] 2> if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1:

[0265] 3> indicate random access problem to upper layers.

[0266] 2> if the random access procedure is not completed:

[0267] 3> select a random back-off time according to uniform distribution between 0 and PREAMBLE_BACKOFF;

[0268] 4> perform the random access resource selection procedure after the back-off time.

[0269] Annex 2

[0270] 1> if the random access procedure is initiated for beam failure recovery; and

[0271] 1> if beamFailureRecoveryTimer is running or not configured; and

[0272] 1> if at least one of the CSI-RS indices in the candidateBeamRSList among which the SS-RSRP is above rsrp-ThresholdCSI-RS is available:

[0273] 2> select the CSI-RS in the candidateBeamRSList among which the SS-RSRP is above rsrp-ThresholdCSI-RS

[0274] 3> set PREAMBLE_INDEX to the ra-PreambleIndex corresponding to the selected SSB from the set of random access preambles used for beam failure recovery request.

[0275] 1> perform the random access preamble transmission procedure.

[0276] 1> RAR reception: legacy Msg2 reception

[0277] 1> the UE sends message 3 to the gNB, where the message includes an indication of beam failure recovery in RRC_INACTIVE state.

[0278] Contention resolution

[0279] 1> if a notification of reception of a PDCCH transmission by lower layers is received:

[0280] 2> if the C-RNTI MAC CE is included in Msg3:

[0281] 3> if the random access procedure was initiated for beam failure recovery and the PDCCH transmission is addressed to C-RNTI;

[0282] 4> consider this contention resolution successful;

[0283] 4> stop the ra-ContentionResolutionTimer;

[0284] 4> discard the TEMPORARY_C-RNTI;

[0285] 4> consider the random access procedure successfully completed.

[0286] 4> if msg 4 includes an indication that "UE remains in RRC_INACTIVE state"

[0287] From NW

[0288] UE stays in RRC_INACTIVE state;

[0289] Else, the UE enters RRC_Connected state and starts RRC connection establishment.

[0290] 1> if the ra-ContentionResolutionTimer expires:

[0291] 2> discard the TEMPORARY_C-RNTI;

[0292] 2> consider the contention resolution unsuccessful.

[0293] 1> if contention resolution is considered unsuccessful:

[0294] 2> flush the HARQ buffer used for transmission of the MAC PDU in Msg3 buffer;

[0295] 2> increase PREAMBLE_TRANSMISSION_COUNTER by 1;

[0296] 2> if PREAMBLE_TRANSMISSION_COUNTER = preambleTransMax + 1:

[0297] 3> indicate random access problem to upper layers.

[0298] 2> if the random access procedure is not completed:

[0299] 3> select a random back-off time according to a uniform distribution between 0 and PREAMBLE_BACKOFF;

[0300] 4> perform the random access resource selection procedure after the back-off time.

Claims

1. A method for beam failure recovery in a communication network, the method comprising: detecting, at a user equipment, UE in an inactive state, a beam failure based on a downlink transmission; and performing, at the UE in the inactive state, a beam failure recovery, BFR, procedure based on detecting the beam failure, wherein a first transmission control indicator, TCI, state for physical downlink shared channel, PDSCH, reception of a preconfigured uplink resource, PUR, occasion is quasi co-located with a synchronization signal block, SSB, index quasi co-location for physical downlink control channel, PDCCH, reception.

2. The method of claim 1, wherein: the downlink transmission comprises a reference signal; and detecting the beam failure comprises measuring the reference signal.

3. The method of claim 2, wherein, the reference signal comprises a synchronization signal block.

4. The method of claim 2, wherein, the reference signal comprises a channel state information reference signal.

5. The method of claim 1, wherein, detecting the beam failure comprises detecting the beam failure based on a beam failure measurement configuration.

6. The method of claim 5, further comprising receiving, at the UE, the beam failure measurement configuration.

7. The method of claim 5, wherein, the UE receives the beam failure measurement configuration based on a preconfigured uplink resource, PUR, response.

8. The method of claim 5, wherein, the UE receives the beam failure measurement configuration based on a system information block, SIB, transmission.

9. The method of claim 5, wherein, the UE is preconfigured with at least a portion of the beam failure measurement configuration in a connected state.

10. The method of claim 5, wherein, detecting the beam failure comprises: switching one or more beams based on the beam failure measurement configuration; and measuring the one or more beams based on the beam failure measurement configuration.

11. The method of claim 1, wherein: the method further comprises performing, from the UE in the inactive state, an uplink transmission; the downlink transmission comprises an acknowledgement transmission for the uplink transmission; and detecting the beam failure comprises measuring the acknowledgement transmission.

12. The method of claim 11, wherein, the uplink transmission comprises a preconfigured uplink resource, PUR, transmission.

13. The method of claim 11, wherein: the UE performs a transition to a connected state; and the UE indicates the transition is based on detecting the beam failure.

14. The method of claim 1, wherein, performing the BFR procedure comprises: receiving a configuration for a physical random access channel, PRACH, transmission; and transmitting a contention-free beam recovery request based on the configuration.

15. The method of claim 1, wherein, the first TCI state is quasi co-located with the SSB index based on a delay between the PDSCH reception and a physical downlink control channel, PDCCH, reception for a PUR response of the PUR occasion.

16. A method for beam management in a communication network, the method comprising: detecting, at a user equipment, UE in an inactive state, a beam failure based on a downlink transmission; wherein a first transmission control indicator, TCI, state for physical downlink shared channel, PDSCH, reception of a preconfigured uplink resource, PUR, occasion is quasi co-located with a default TCI state of a physical downlink control channel, PDCCH, reception based on a delay between the PDSCH reception and the PDCCH reception for a PUR response of the PUR occasion.

17. The method of claim 16, wherein: The UE monitors one or more control resource sets, CORESETs, in a slot; and The default TCI state for the PDCCH reception comprises a first CORESET of the one or more CORESETs corresponding to a SSB index.

18. The method of claim 16, wherein, The default TCI state for the PDCCH reception comprises a synchronization signal block, SSB, index that is quasi co-located with the PUR.

19. A communication device, comprising: a transceiver; and a controller configured to control the transceiver to perform the method of any one of claims 1-18.

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