CONFIGURATION

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 62/969,200 filed February 3, 2020, the entirety of which is incorporated by reference herein.

TECHNICAL FIELD

[0002] Embodiments of the invention relate to wireless communications; more specifically, to the configuration of radio link monitoring reference signals.

BACKGROUND

[0003] The Fifth Generation New Radio (5G NR) is a telecommunication standard for mobile broadband communications. NR is promulgated by the 3rd Generation Partnership Project (3GPP) to significantly improve performance metrics such as latency, reliability, throughput, etc. Furthermore, NR supports beamforming, multiple-input multiple-output (MIMO) antenna technology, and carrier aggregation.

[0004] A base station (e.g., gNB) in a 5G NR network transmits downlink signals to a user equipment (UE) via radio beams. The UE monitors downlink reference signals to detect beam failure. When a beam failure condition is met, the UE performs a beam failure recovery (BFR) procedure to restore the radio link between the UE and the base station. The reference signals monitored by the UE are indicated in a radio link monitoring (RLM) configuration. The base station may configure the UE’s RLM configuration via a radio resource control (RRC) message.

[0005] The existing 5G NR technology can be further improved to benefit operators and users. These improvements may also apply to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

[0006] In one embodiment, a method is performed by a UE in a wireless network for updating a radio link monitoring reference signal (RLM RS) configuration. The UE receives a media access control (MAC) control element (CE) from a base station. The MAC CE includes an indication of a detection resource in the RLM RS configuration. The UE then updates the detection resource in the RLM RS configuration according to the MAC CE, and measures an RLM RS received from the base station. The RLM RS is the detection resource updated in the RLM RS configuration.

[0007] In another embodiment, a UE in a wireless network comprises a memory to store a RLM RS configuration. The UE further includes transceiver circuitry operative to receive a MAC CE from a base station. The MAC CE includes an indication of a detection resource in the RLM RS configuration. The UE further includes processing circuitry coupled to the memory and the transceiver circuitry. The processing circuitry is operative to update the detection resource in the RLM RS configuration according to the MAC CE, and measure an RLM RS received from the base station. The RLM RS is the detection resource updated in the RLM RS configuration.

[0008] Other aspects and features will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that different references to "an" or "one" embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0010] Figure l is a diagram illustrating a network in which a base station and a UE communicate according to one embodiment.

[0011] Figure 2 is a diagram illustrating a process for using a MAC CE to update an RLM configuration of a UE according to one embodiment.

[0012] Figure 3 is a diagram illustrating a process performed by a UE for failure detection and recovery according to one embodiment.

[0013] Figure 4 is a diagram illustrating an RLM configuration and a TCI state list according to one embodiment.

[0014] Figure 5A and 5B illustrate examples of a medium access control (MAC) control element (CE) according to some embodiments. [0015] Figure 6A and 6B illustrate examples of a MAC CE according to some other embodiments.

[0016] Figure 7 is a flow diagram illustrating a method performed by a UE for updating an RLM configuration according to one embodiment.

[0017] Figure 8 is a block diagram illustrating an apparatus that performs wireless communication according to one embodiment.

DETAILED DESCRIPTION

[0018] In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques have not been shown in detail in order not to obscure the understanding of this description. It will be appreciated, however, by one skilled in the art, that the invention may be practiced without such specific details. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation.

[0019] Embodiments of the invention improve the reconfiguration latency of one or more radio link monitoring (RLM) reference signals. In one embodiment, a base station may update a UE’s RLM configuration via layer-2 (L2) signaling; e.g., via a medium access control (MAC) control element (CE). The reconfiguration latency of L2 signaling is significantly lower than that of level-3 (L3) signaling (e.g., the radio resource control (RRC) signaling). An RLM configuration includes a set of RLM reference signals that can be used for the purpose of beam failure detection (BFD), radio link failure (RLF) detection, or both. For each RLM reference signal (RLM RS), the RLM configuration specifies a detection resource such as a channel state information reference signal (CSI-RS) or a synchronization signal block (SSB). Thus, when there is a change in the channel condition between the base station and the UE (e.g., caused by a signal blockage or UE movement), the base station can quickly and efficiently update one or more detection resources to avoid beam failure or radio link failure.

[0020] The term “RLM configuration,” which may also be referred to as RadioLinkMonitoringConfig, includes the configuration of a set of RLM reference signals (RadioLinkMonitoringRS). Each RLM reference signal is identified by an identifier (radioLinkMonitoringRS-Id) and can be explicitly configured with a detection resource (detectonResource), such as a CSI-RS identified by NZP-CSI-RS-Resourceld or an SSB identified by SSB-Index. The configuration parameters, identifiers (IDs), and their values mentioned herein such as RadioLinkMonitoringConfig, RadioLinkMonitoringRS, radioLinkMonitoringRS-Id, detectonResource, NZP-CSI-RS-Resourceld, and SSB-Index, are defined in 3 GPP Technical Specification; e.g., 3GPP TS 38.331, version 15.7.0, Release 15, October 2019.

[0021] The disclosed method, as well as the apparatus and the computer product implementing the method, can be applied to wireless communication between a base station (e.g., a gNB in a 5G NR network) and UEs. It is noted that while the embodiments may be described herein using terminology commonly associated with 5G or NR wireless technologies, the present disclosure can be applied to other multi-access technologies and the telecommunication standards that employ these technologies, such as Long Term Evolution (LTE) systems, future 3 GPP systems, IEEE protocols, and the like.

[0022] Figure 1 illustrates a wireless network 100 in which a base station (BS) 120 and a UE 150 communicate according to one embodiment. In some network environments such as a 5GNR network, the BS 120 may be known as a gNodeB, a gNB, and/or the like. In an alternative network environment, a base station may be known by other names. The BS 120 transmits beamformed signals to the UE 150. The UE 150 may also be known by other names, such as a mobile station, a subscriber unit, and/or the like. The UE 150 may be stationary or mobile. In practice, the network 100 may include additional devices, different devices, or differently arranged devices than those shown in Figure 1.

[0023] Examples of the UE 150 may include a cellular phone (e.g., a smartphone), a wireless communication device, a handheld device, a laptop computer, a tablet, a gaming device, a wearable device, an entertainment device, a sensor, an infotainment device, Internet-of-Things (IoT) devices, or any device that can communicate via a wireless medium. The UE 150 can be configured to receive and transmit signals over an air interface to one or more cells in a radio access network.

[0024] In one embodiment, the UE 150 provides layer-3 functionalities through a radio resource control (RRC) layer, which is associated with the transfer of system information, connection control, and measurement configurations. The UE 150 further provides layer-2 functionalities through a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The PDCP layer is associated with header compression/decompression, security, and handover support. The RLC layer is associated with the transfer of packet data units (PDUs), error correction through automatic repeat request (ARQ), concatenation, segmentation, and reassembly of RLC service data units (SDUs). The MAC layer is associated with the mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), de-multiplexing of MAC SDUs from TBs, scheduling information reporting, error correction through hybrid ARQ (HARQ), priority handling, and logical channel prioritization. The UEs 150 further provides layer- 1 functionalities through a physical (PHY) layer, which is associated with error detection on the transport channels, forward error correction (FEC) coding/decoding of the transport channels, interleaving, rate matching, mapping onto physical channels, modulation/demodulation of physical channels, and multiple-input and multiple-output (MIMO) antenna processing, etc.

[0025] In a 5G NR network, a base station such as a gNB may configure and activate a bandwidth part (BWP) for communication with UEs in a serving cell, through a radio resource control (RRC) configuration according to an RRC layer protocol. The activated BWP is referred to as the frequency resources, and the time scheduled for the communication is referred to as the time resources. The frequency resources and the time resources are herein collectively referred to as the time-and-frequency resources. In a wireless network, different serving cells may be configured with different time-and-frequency resources. Different time-and-frequency resources may be allocated to different physical uplink channels, physical downlink channels, uplink signals, and downlink signals.

[0026] In one embodiment, both the BS 120 and the UE 150 include MIMO antenna arrays for performing beam steering and tracking in transmit (Tx) and receive (Rx) directions. In the example of Figure 1, the BS 120 forms beams DB#1, DB#2, DB#3, and DB#4 for downlink transmission and uplink reception, and the UE 150 forms beams UB#1 and UB#2 for uplink transmission and downlink reception. The downlink signals include UE-specific data signals and control signals such as reference signals. The UE 150 is configured to use some of the reference signals for beam failure detection and/or radio link failure detection. For example, the UE 150 may initially be configured to use RLM RS#1 as a detection resource. When a failure condition is detected by the UE 150, the UE 150 may switch to RLM RS#2 as an updated detection resource, where RLM RS#2 is communicated to the UE 150 via a different radio path than that of RLM RS#1. In one embodiment, the BS 120 may update the configuration of the UE 150 when a change in channel condition is detected to avoid beam failure or radio link failure. In one embodiment, the BS 120 may update the RLM configuration of the UE 150 via a MAC CE.

[0027] Specifically, the MAC CE updates the detection resource in the configuration of an RLM RS. The detection resource includes a reference signal, such as a CSI-RS or an SSB. Each of these reference signals corresponds to a spatial relation between the BS 120 and the UE 150. To the UE 150, a spatial relation is equivalent to spatial filtering that the UE can apply in the analog and/or digital domain.

[0028] Figure 2 is a diagram illustrating a process 200 for using a MAC CE to update an RLM configuration of a UE (e.g., the UE 150 in Figure 1) according to one embodiment. At step 210, a base station a MAC CE sends to a UE, the MAC CE indicating one or more detection resources in the RLM configuration of the UE. Each detection resource is used for an RLM RS in the RLM configuration. After receiving the MAC CE, the UE at step 220 updates the one or more detection resources in its RLM configuration. In one embodiment, the MAC CE may include an updated detection resource identifier, such as SSB-Index (which identifies an updated SSB) and/or NZP- CSI-RS-Resourceld (which identifies an updated CSI-RS). Alternatively, the MAC CE may include a transmission configuration indication (TCI) state ID, which identifies an updated detection resource, such as an updated SSB or an updated CSI-RS. The UE at step 230 then monitors one or more updated RLM RSs according to the one or more updated detection resources according to the updated RLM configuration. The UE at step 240 measures the one or more updated RLM RSs to detect beam failure or radio link failure.

[0029] Figure 3 is a diagram illustrating a process 300 performed by a UE (e.g., the UE 150 in Figure 1) for failure detection and recovery according to one embodiment. At step 310, the UE detects beam failure or radio link failure based on measurements of one or more RLM reference signals. Radio link failure occurs when a UE in an RRC connected state detects, consecutively for a configured time period, downlink out-of-synchronization (OOS) condition, random access procedure failure, or radio link control (RLC) failure. Beam failure occurs when a UE detects, for all physical downlink control channel (PDCCH) beams, a consecutive number of detected beam failure instances (BFIs). A BFI is detected when the hypothetical PDCCH block error rate (BLER) > RLM default BLER for OOS. The UE maintains a timer for counting the number of valid BFIs. The timer is (re)started upon every new reception of a BFI. The counter is reset when the timer expires.

[0030] Upon detection of the failure, the UE performs a recovery procedure at step 320. For radio link failure recovery, the UE initiates an RRC connection re-establishment procedure. For beam failure recovery, the UE monitors beam identification (NBI) reference signal to find a new candidate beam, and transmits a beam failure recovery request (BFRQ) to the base station on a contention-free random-access channel (RACH). The beam failure recovery (BFR) procedure is completed when the UE receives a beam BFR response from the base station. [0031] Figure 4 is a diagram illustrating an RLM configuration 410 and a TCI state list 420 according to one embodiment. The RLM configuration 410 and a TCI state list 420 are stored in a UE’s memory 480. The RLM configuration 410 includes a configuration of one or more RLM RSs. The term “RLM RS configuration” (e.g., an RLM RS configuration 412 shown in Figure 4) is used herein to refer to the configuration of one RLM RS. Each RLM RS is identified by an identifier (radioLinkMonitorigRS-Id). Each RLM RS is configured with one of the following purposes: BFD, radio link failure (rlf) detection, or both. An RLM RS may be explicitly configured as either a C SI RS or an SSB, as indicated by the “detection source” 415 in the RLM configuration 410. When an RLM RS is configured with no detection source in the RLM configuration 410, the RLM RS is implicitly configured as a quasi-collocation (QCL) RS in an activated TCI state of the PDCCH. In the present disclosure, a MAC CE 450 is used to update an RLM RS that is explicitly configured with a detection resource.

[0032] The TCI state list 420 includes a list of TCI states, each TCI state identified by a unique TCI state ID. Each TCI state is associated with up to two reference signals, which are referred to as the QCL reference signals. A QCL source reference signal (QCL RS) is either a CSI-RS or an SSB. Each QCL RS has a corresponding QCL type. The QCL types may be one of the following: QCL- type A: (Doppler shift, Doppler spread, average delay, delay spread); QCL-type B: (Doppler shift, Doppler spread); QCL-type C: (Doppler shift, average delay); and QCL-type D: (spatial Rx parameter).

[0033] According to embodiments of the present invention, a base station may use the MAC CE 450 to update the detection resource 415 in the RLM configuration 410. In one embodiment, the MAC CE 450 may include a resource ID for use as the detection resource 415 for an RLM RS. In another embodiment, the MAC CE 450 may include a TCI state ID, which identifies a TCI state associated with a QCL RS having QCL-type D. This QCL source RS (having QCL-type D) is used to update the detection resource 415 in the RLM configuration 410. If the TCI state includes only one QCL RS and that QCL RS is not QCL-type D, the detection resource 415 in the RLM configuration 410 is updated to that QCL RS.

[0034] It is noted that in the aforementioned embodiments, the detection resource 415 in the RLM configuration 410 is updated by the MAC CE 450. The update does not change the TCI state list 420. The update also does not change the PDCCH TCI states in the control resource set (CORESET) configuration. [0035] As mentioned before, a base station may update the detection resource in an RLM configuration using a MAC CE. A MAC CE is a bit string that is byte aligned (e.g., multiple of 8 bits) in length. A MAC CE is part of a MAC subPDU; a MAC PDU consists of one or more MAC subPDUs.

[0036] Figure 5 A is a diagram illustrating a MAC CE 510 according to one embodiment. The MAC CE 510 includes three 8-bit segments (i.e., 3 bytes), with each byte shown as a row. The MAC CE 510 can be used to update the detection resource of one RLM RS in an RLM configuration (e.g., the RLM configuration 410 in Figure 4).

[0037] The MAC CE 510 includes a serving cell ID, a BWP ID, and an RLM RS ID 511. The MAC CE 510 further includes a TCI state ID 512. The “R” field is a reserved field. Referring also to Figure 4, when a UE receives the MAC CE 510 with RLM RS ID = RLM RS ID #1 and TCI state ID = TCI state #1, the UE refers to the TCI state list 420 to identify SSB #2 as the new detection resource of RLM RS ID #1 (where SSB #2 is the QCL RS associated with the TCI state ID). The UE then updates the detection resource of RLM RS ID #1 in the RLM configuration to SSB #2.

[0038] Figure 5B is a diagram illustrating a MAC CE 520 according to another embodiment. The MAC CE 520 can be used to update the respective detection resources of N RLM RSs in an RLM configuration (e.g., the RLM configuration 410 in Figure 4).

[0039] The MAC CE 520 includes (2N + 1) bytes, where N is a positive integer. The first byte of the MAC CE 520 includes a serving cell ID and a BWP ID. Each pair of bytes that follows includes an RLM RS ID 521 -i, and a TCI state ID 522-i, where i is a running index from 1 to N. The “R” field is a reserved field. The Έ” field is an extension field which has a binary value indicating existence of an additional detection resource to be updated. Specifically, the extension field indicates the existence of a next pair of (RLM RS ID, TCI state ID). For example, the E field is set to 0 to indicate the nonexistence of an extension. It is set to 1 to indicate the existence of an extension. Alternatively, the “1” and “0” values of the E field may be reversed. Similar to the example in Figure 5A, for each pair of (RLM RS ID, TCI state ID), the UE refers to a TCI state list to identify a QCL RS associated with the TCI state ID as the new detection resource of the RLM RS ID, and updates the detection resource of the RLM RS ID in the RLM configuration accordingly. [0040] Figure 6A is a diagram illustrating a MAC CE 610 according to one embodiment. The MAC CE 610 includes three 8-bit segments (i.e., 3 bytes), with each byte shown as a row. The MAC CE 610 includes a serving cell ID, a BWP ID, and an RLM RS ID 611. The MAC CE 610 further includes a detection resource ID 612. The “R” field is a reserved field. The MAC CE 610 can be used to update the detection resource of one RLM RS. The “F” field is a 1-bit value indicating whether the detection resource is CSI-RS or SSB. For example, if F is set to 0, the detection resource ID field 612 contains SSB-Index identifying an SSB; if F is set to 1, the detection resource ID field 612 contains CSI-Resourceld identifying a CSI-RS. Alternatively, the “1” and “0” values of the F field may be reversed.

[0041] Figure 6B is a diagram illustrating a MAC CE 620 according to another embodiment. The MAC CE 620 includes (2N + 1) bytes, where N is a positive integer. The MAC CE 620 can be used to update N RLM RSs in an RLM configuration. The first byte of the MAC CE 620 includes a serving cell ID and a BWP ID. Each pair of bytes that follows includes an RLM RS ID 621-i, a detection resource ID 622-i, and the “Fi” field, where i is a running index from 1 to N. The “Fi” field contains a 1-bit value indicating whether the detection resource is CSI-RS or SSB as mentioned in Figure 6A. The “R” field is a reserved field. The Έ” field indicates extension; it indicates the existence of a next pair of (RLM RS ID, detection resource ID). For example, the E field is set to 0 to indicate the nonexistence of an extension. It is set to 1 to indicate the existence of an extension. Alternatively, the “1” and “0” values of the E field may be reversed.

[0042] Figure 7 is a flow diagram illustrating a method 700 performed by a UE (e.g., the UE 150 in Figure 1 and/or the apparatus 900 in Figure 9) in a wireless network according to one embodiment. The method 700 begins at step 710 when the UE receives a MAC CE from a base station. The MAC CE includes an indication of a detection resource in an RLM RS configuration. The UE at step 720 updates the detection resource in the RLM RS configuration according to the MAC CE. The UE at step 730 measures an RLM RS from the base station, the RLM RS being the detection resource in the RLM RS configuration.

[0043] In one embodiment, the MAC CE includes a detection resource identifier that identifies an SSB as the detection resource. In one embodiment, the MAC CE includes a detection resource identifier that identifies a CSI-RS as the detection resource. In one embodiment, the MAC CE includes a TCI state identifier associated with an SSB having QCL-type D, and the SSB is used as an updated detection resource. In one embodiment, the MAC CE includes a TCI state identifier associated with a CSI-RS having QCL-type D, and the CSI-RS is used as an updated detection resource.

[0044] Figure 8 is a block diagram illustrating elements of an apparatus 800 performing wireless communication with a base station 850 according to one embodiment. In one embodiment, the apparatus 800 may be a UE and the base station 850 may be a gNb or the like, both of which may operate in a wireless network, such as the wireless network 100 in Figure 1. In one embodiment, the base station 850 may be the base station 120 and the apparatus 800 may be the UE 150 in Figure 1. In one embodiment, the base station 850 includes an antenna array 855 to form beams for transmitting and receiving signals.

[0045] In one embodiment, the apparatus 800 includes an antenna assembly 810; e.g., MIMO antenna arrays, to form beams for transmitting and receiving signals. The apparatus 800 also includes a transceiver circuit (also referred to as a transceiver 820) further including a transmitter and a receiver configured to provide radio communications with another station in a radio access network. The transmitter and the receiver may include filters in the digital front end for each cluster, and each filter can be enabled to pass signals and disabled to block signals. The apparatus 800 may also include processing circuitry 830 which may include one or more control processors, signal processors, central processing units, cores, and/or processor cores. The apparatus 800 may also include a memory circuit (also referred to as memory 840) coupled to the processing circuitry 830 to store configurations 845; e.g., the RLM configuration 410 and the TCI state list 420 in Figure 4. The apparatus 800 may also include an interface (such as a user interface). The apparatus 800 may be incorporated into a wireless system, a station, a terminal, a device, an appliance, a machine, and IoT operable to perform wireless communication in a multi-access network, such as a 5G NR network. It is understood the embodiment of Figure 8 is simplified for illustration purposes. Additional hardware components may be included.

[0046] In one embodiment, the apparatus 800 may store and transmit (internally and/or with other electronic devices over a network) code (composed of software instructions) and data using computer-readable media, such as non-transitory tangible computer-readable media (e.g., computer- readable storage media such as magnetic disks; optical disks; read-only memory; flash memory devices) and transitory computer-readable transmission media (e.g., electrical, optical, acoustical or other forms of propagated signals). For example, the memory 840 may include a non-transitory computer-readable storage medium that stores computer-readable program code. The code, when executed by the processors, causes the processors to perform operations according to embodiments disclosed herein, such as the method disclosed in Figure 7.

[0047] Although the apparatus 800 is used in this disclosure as an example, it is understood that the methodology described herein is applicable to any computing and/or communication device capable of performing wireless communications. [0048] The operations of the flow diagram of Figure 7 have been described with reference to the exemplary embodiments of Figures 1 and 8. However, it should be understood that the operations of the flow diagram of Figure 7 can be performed by embodiments of the invention other than the embodiments of Figures 1 and 8, and the embodiments of Figures 1 and 8 can perform operations different than those discussed with reference to the flow diagram. While the flow diagram of Figure 7 shows a particular order of operations performed by certain embodiments of the invention, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

[0049] Various functional components or blocks have been described herein. As will be appreciated by persons skilled in the art, the functional blocks will preferably be implemented through circuits (either dedicated circuits, or general-purpose circuits, which operate under the control of one or more processors and coded instructions), which will typically comprise transistors that are configured in such a way as to control the operation of the circuity in accordance with the functions and operations described herein.

[0050] While the invention has been described in terms of several embodiments, those skilled in the art will recognize that the invention is not limited to the embodiments described, and can be practiced with modification and alteration within the spirit and scope of the appended claims. The description is thus to be regarded as illustrative instead of limiting.