Method and apparatus for determining beam failure detection reference signal

Abstract

A method and apparatus for beam failure detection (BFD) reference signal (RS) determination, the method comprising: receiving at least one media access control (MAC) control element (CE) for transmission configuration indicator (TCI) state activation, each of the at least one MAC CE indicating a control resource set (CORESET) and at least one TCI state, each of the at least one MAC CE indicating a plurality of TCI states and at least one TCI state, and at least some of the TCIs indicated in all the indicated TCIs belong to a first set of TCI states associated with a first transmission / reception point (TRP); and performing a first operation after determining that the total number of TCI states included in the first set of TCI states is greater than a first threshold number, the first operation comprising: selecting at least one first TCI state from the first set of TCI states; and determining at least one first BFD RS for detecting a first beam failure condition of the first TRP based on the at least one first TCI state.

Description

[0001] Cross - Reference to Related Applications

[0002] This disclosure claims the benefit and priority of U.S. Provisional Patent Application Serial No. 62 / 984,740, filed on Mar. 3, 2020, entitled “IMPLICIT BFD REFERENCE SIGNAL DETERMINATION FOR PDCCH WITH MULTIPLE ACTIVATED TCI STATES” (“the ’740 provisional application”). For all purposes, the content of the ’740 provisional application is hereby incorporated by reference in its entirety into this document. Field of the Invention

[0003] This disclosure generally relates to wireless communication, and more particularly, to methods and apparatuses for beam failure detection (BFD) reference signal (RS) determination. Background Art

[0004] With the huge growth in the number of connected devices and the rapid increase in user / network traffic, various efforts have been made to improve different aspects of wireless communication in cellular wireless communication systems, such as fifth - generation (5G) new radio (NR), by increasing data rate, reducing latency, improving reliability, and enhancing mobility.

[0005] The 5G NR system is designed to provide flexibility and configurability to optimize network services and types to accommodate various use cases, such as enhanced Mobile Broadband (eMBB), massive Machine - Type Communication (mMTC), and Ultra - Reliable and Low - Latency Communication (URLLC).

[0006] However, as the demand for radio access continues to increase, further improvements in wireless communication for the next - generation wireless communication systems are needed. Summary of the Invention

[0007] This disclosure relates to methods and apparatuses (e.g., user equipment (UE)) for BFD RS determination.

[0008] According to one aspect of the present disclosure, there is provided a method for BFD RS determination performed by a UE configured with more than one transmission / reception point (TRP) in an active bandwidth part (BWP). The method includes: receiving at least one media access control (MAC) control element (CE) for transmission configuration indicator (TCI) state activation, each of the at least one MAC CE indicating a control resource set (CORESET) and at least one TCI state to be used for monitoring a physical downlink control channel (PDCCH), the physical resources of the PDCCH being determined by the configuration of the CORESET indicated by the same at least one MAC CE, one of the at least one MAC CE indicating multiple TCI states, and at least some of all the TCI states being indicated by the at least one MAC CE belonging to a first set of TCI states associated with a first TRP; and performing a first operation after determining that the total number of TCI states included in the first set of TCI states is greater than a first threshold number. The first operation includes: selecting at least one first TCI state from the first set of TCI states, the total number of the at least one first TCI states being equal to the first threshold number; and determining at least one first BFD RS for detecting a first beam failure condition of the first TRP based on the at least one first TCI state.

[0009] According to another aspect of the present disclosure, there is provided a UE configured with more than one TRP in an active BWP for BFD RS determination. The UE includes: a processor; and a memory coupled to the processor, wherein the memory stores at least one computer-executable program that, when executed by the processor, causes the processor to: receive at least one MAC CE for TCI state activation, each of the at least one MAC CE indicating a CORESET and at least one TCI state to be used for monitoring a PDCCH, the physical resources of the PDCCH being determined by the configuration of the CORESET indicated by the same at least one MAC CE, one of the at least one MAC CE indicating multiple TCI states, and at least some of all the TCI states being indicated by the at least one MAC CE belonging to a first set of TCI states associated with a first TRP; and perform a first operation after determining that the total number of TCI states included in the first set of TCI states is greater than a first threshold number. The first operation includes: selecting at least one first TCI state from the first set of TCI states, the total number of the at least one first TCI states being equal to the first threshold number; and determining at least one first BFD RS for detecting a first beam failure condition of the first TRP based on the at least one first TCI state. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] When read in conjunction with the appended Figure 1 drawings, various aspects of the present disclosure can be best understood from the following detailed disclosure. The various features are not drawn to scale. For purposes of discussion, the dimensions of the various features can be increased or decreased arbitrarily.

[0011] Figure 1 Embodiments in accordance with the present disclosure illustrate the MAC CE format.

[0012] Figure 2 Embodiments in accordance with the present disclosure illustrate the TCI code points associated with two TCI states.

[0013] Figure 3 Embodiments in accordance with the present disclosure illustrate a fixed-size MAC CE format for indicating two TCI states.

[0014] Figure 4 Another embodiment in accordance with the present disclosure illustrates a fixed-size MAC CE format for indicating two TCI states.

[0015] Figure 5 Embodiments in accordance with the present disclosure illustrate a variable-size MAC CE format for indicating at least two TCI states.

[0016] Figure 6 Another embodiment in accordance with the present disclosure illustrates a variable-size MAC CE format for indicating at least two TCI states.

[0017] Figure 7 An embodiment in accordance with the present disclosure illustrates a flowchart of a method for BFD RS determination performed by a UE configured with more than one TRP in an active BWP.

[0018] Figure 8 Embodiments in accordance with the present disclosure illustrate Figure 7 a flowchart of a first operation of

[0019] Figure 9 Embodiments in accordance with the present disclosure illustrate the process of BFD RS determination.

[0020] Figure 10 Embodiments in accordance with the present disclosure illustrate a block diagram of a node for wireless communication. DETAILED DESCRIPTION

[0021] The following includes specific information related to exemplary embodiments in the present disclosure. The accompanying drawings and the detailed disclosure thereof are directed to the exemplary embodiments. However, the present disclosure is not limited to these exemplary embodiments. Other variations and embodiments of the present disclosure will be apparent to those skilled in the art. Unless otherwise specified, similar or corresponding elements in the drawings may be denoted by similar or corresponding reference numerals. In addition, the drawings and illustrations are generally not drawn to scale and are not intended to correspond to actual relative dimensions.

[0022] For consistency and ease of understanding, in the drawings, similar features may be identified by the same numerals (although not shown in some examples). However, the features in different embodiments may be different in other respects and should not be narrowly limited to what is shown in the drawings.

[0023] References to "one embodiment", "an embodiment", "exemplary embodiment", "various embodiments", "some embodiments", "embodiments of the present disclosure", etc. may indicate that the embodiments of the present disclosure may include a particular feature, structure, or characteristic, but not every possible embodiment of the present disclosure necessarily includes the particular feature, structure, or characteristic. In addition, the repeated use of the phrase "in one embodiment", "in an exemplary embodiment", or "an embodiment" does not necessarily refer to the same embodiment, although they may be the same. In addition, any use of phrases such as "embodiments" associated with "the present disclosure" does not mean that all embodiments of the present disclosure must include a particular feature, structure, or characteristic. On the contrary, it should be understood that "at least some embodiments of the present disclosure" include the said particular feature, structure, or characteristic. The term "coupled" is defined as connected directly or indirectly through an intermediate component and is not necessarily limited to a physical connection. The term "comprising", when used, means "comprising but not necessarily limited to"; it specifically indicates an open inclusion or membership in the disclosed combinations, groups, series, and equivalents. The terms "system" and "network" in the present disclosure may be used interchangeably.

[0024] The term "and / or" herein is only used to describe the association relationship of associated objects and indicates that there can be three relationships. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. "A and / or B and / or C" may represent the existence of at least one of A, B, and C. The character " / " used herein generally indicates that the former and the latter associated objects are in an "or" relationship.

[0025] In addition, for purposes of explanation rather than limitation, specific details are set forth for providing an understanding of the disclosed technology, such as functional entities, technologies, protocols, standards, etc. In other examples, detailed disclosures of well-known methods, technologies, systems, and architectures are omitted to avoid obscuring the present disclosure with unnecessary details.

[0026] Those skilled in the art will immediately recognize that any disclosed network function or algorithm can be implemented by hardware, software, or a combination of software and hardware. The disclosed functions may correspond to modules that can be software, hardware, firmware, or any combination thereof. Software implementations may include computer-executable instructions stored on a computer-readable medium (such as a memory or other type of storage device). For example, one or more microprocessors or general-purpose computers with communication processing capabilities can be programmed with the corresponding executable instructions and execute the disclosed network function or algorithm. The microprocessor or general-purpose computer can be composed of an application specific integrated circuitry (ASIC), a programmable logic array, and / or use one or more digital signal processors (DSP). Although some of the disclosed embodiments are applicable to software installed on and executed on computer hardware, alternative embodiments as firmware or hardware or a combination of hardware and software are fully within the scope of this disclosure.

[0027] The computer-readable medium may include, but is not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, compact disc read-only memory (CD-ROM), cassette tapes, magnetic tapes, disk storage devices, or any other equivalent medium capable of storing computer-readable instructions.

[0028] A radio communication network architecture (e.g., Long-Term Evolution (LTE) system, LTE-Advanced (LTE-A) system, LTE Advanced Pro system) generally may include at least one base station (BS), at least one UE, and one or more optional network elements providing connection to the network. The UE may communicate with a network (e.g., Core Network (CN), Evolved Packet Core (EPC) network, Evolved Universal Terrestrial RAN (E-UTRAN), Next-Generation Core (NGC), 5G Core (5GC), or the Internet) via a Radio Access Network (RAN) established by the BS.

[0029] The UE disclosed herein may include, but is not limited to, a mobile station, a mobile terminal or device, or a user communication radio terminal. The UE may be a portable radio device, which includes, but is not limited to, a mobile phone, a tablet computer, a wearable device, a sensor, or a Personal Digital Assistant (PDA) having wireless communication capabilities. The UE is configured to receive signals via an air interface and transmit them to one or more cells in the RAN.

[0030] The BS disclosed herein may include, but is not limited to, a Node B (NB) in a Universal Mobile Telecommunication System (UMTS), an evolved Node B (eNB) in LTE-A, a Radio Network Controller (RNC) in UMTS, a Base Station Controller (BSC) in a Global System for Mobile communication (GSM) / GSM EDGE Radio Access Network (GERAN), a next-generation eNB (ng-eNB) in an Evolved Universal Terrestrial Radio Access (E-UTRA) BS connected to 5GC, a next-generation Node B (gNB) in a 5G Access Network (5G-RAN), and any other device capable of controlling radio communication and managing radio resources within a cell. The BS may be connected to a network via a radio interface to serve one or more UEs.

[0031] The BS may be configured to provide communication services according to at least one of Radio Access Technologies (RATs): Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile communications (GSM, commonly referred to as 2G), GERAN, General Packet Radio Service (GPRS), UMTS based on Wideband-Code Division Multiple Access (W-CDMA) (commonly referred to as 3G), High-Speed Packet Access (HSPA), LTE, LTE-A, enhanced LTE (eLTE), NR (commonly referred to as 5G), and / or LTE-A Pro. However, the scope of the present disclosure should not be limited to the above protocols.

[0032] The BS may be operable to provide radio coverage to a specific geographical area using multiple cells that form a RAN. The BS may support the operation of the cells. Each cell may operate to provide service to at least one UE within its radio coverage. Specifically, each cell (commonly referred to as a serving cell) may provide service to one or more UEs within its radio coverage (e.g., each cell schedules DL resources and optionally UL resources to at least one UE within its radio coverage for DL and optionally UL packet transmission). The BS may communicate with one or more UEs in the radio communication system via multiple cells.

[0033] The cell may allocate sidelink (SL) resources to support proximity service (ProSe), LTE SL service, and / or LTE / NR vehicle-to-everything (V2X) service. Each cell may have a coverage area that overlaps with other cells. In the case of multi-RAT dual connectivity (MR-DC), the primary cell of the master cell group (MCG) or the secondary cell group (SCG) may be referred to as a special cell (SpCell). The primary cell (PCell) may refer to the SpCell of the MCG. The primary SCG cell (PSCell) may refer to the SpCell of the SCG. The MCG may refer to a set of serving cells associated with a master node (MN), including the SpCell and optionally one or more secondary cells (SCells). The SCG may refer to a set of serving cells associated with a secondary node (SN), including the SpCell and optionally one or more SCells.

[0034] As previously mentioned, the frame structure of NR supports flexible configuration to accommodate various next-generation (e.g., 5G) communication requirements, such as eMBB, mMTC, and URLLC, while meeting high-reliability, high-data-rate, and low-latency requirements. In the Third Generation Partnership Project (3 rdThe orthogonal frequency-division multiplexing (OFDM) technology stipulated in the 3rd Generation Partnership Project (3GPP) can be used as the baseline for NR waveforms. Scalable OFDM parameter sets can also be used, such as adaptive subcarrier spacing, channel bandwidth, and cyclic prefix (CP). In addition, NR considers two coding schemes: (1) Low-Density Parity-Check (LDPC) codes and (2) polar codes. Coding scheme adaptation can be configured based on channel conditions and / or service applications.

[0035] In addition, it should be considered that the transmission time interval of a single NR frame should at least include DL transmission data, a guard period, and UL transmission data. Each part of the DL transmission data, the guard period, and the UL transmission data should also be configured based on, for example, the network dynamics of NR. In addition, SL resources can also be provided in the NR frame to support ProSe services.

[0036] The 3rd Generation Partnership Project (3GPP) New Radio (NR) Release 15 (Rel-15) supports link recovery (e.g., Beam Failure Recovery (BFR)) for special cells (e.g., Primary Cell (PCell) and / or Primary Secondary Cell (PSCell)). In Release 16 (Rel-16), link recovery for secondary cells is also introduced. From a high-level perspective, the link recovery process can include the following stages: Beam Failure Detection (BFD), New Beam Identification (NBI), Beam Failure Recovery reQuest (BFRQ) transmission, and network response reception.

[0037] In the BFD stage, the UE can detect beam failure events in the BWP of the serving cell based on at least one BFD reference signal (RS) implicitly or explicitly configured by the network (e.g., BS).

[0038] In the NBI stage, the UE can identify an alternative beam for recovering the link where the beam failure event is detected based on a set of configured (NBI) RSs.

[0039] In the BFRQ transmission phase, the UE can transmit the information required to resume the link. The BFRQ transmission can be a Physical Random Access Channel (PRACH)-based transmission for a special cell or a Physical Uplink Shared Channel (PUSCH)-based transmission (carried in the MAC CE) for an SCell.

[0040] In the network response reception phase, the UE can receive a response from the network (e.g., the BS) to complete the link recovery. For a special cell, the UE can monitor PDCCH transmissions on a dedicated-configured search space to determine whether the network has successfully received the BFRQ. For an SCell, the UE can monitor UL DCI (PDCCH) transmissions that indicate the HARQ process ID, which is the same as the HARQ process ID used for the BFRQ (PUSCH) transmission but with a toggled NDI field.

[0041] In Release 17 (Rel-17), the multi-TRP scenario can be extended for DL control channels (e.g., PDCCH). Details on how to implicitly derive BFD RS need to be designed.

[0042] In NR Rel-15 / 16, the Quasi-Colocated (QCL) assumptions for transmission are indicated by Transmission Configuration Indication (TCI) states. For PDCCH reception, the CORESET can be configured with a candidate TCI state group by Radio Resource Control (RRC) signaling and has a numerical limit (e.g., maxNrofTCI-StatesPDCCH). Among the candidate TCI state groups, the TCI state can be activated by a MAC CE for monitoring the CORESET. As used herein, "monitoring the CORESET" can refer to monitoring the PDCCH whose physical resources are determined by the configuration of the CORESET. The MAC CE for activating the TCI state can have a fixed size of 16 bits, as Figure 1 shown.

[0043] Figure 1 FIG. 100 shows the MAC CE format according to an embodiment of the present disclosure. The symbol "Oct" can refer to an octet, which is a digital information unit consisting of eight bits. As Figure 1As shown, the MAC CE format 100 has a fixed size of 16 bits and consists of two octets: Oct 1 and Oct 2. The MAC CE format 100 includes the following fields:

[0044] Serving cell ID: This field indicates the identity (ID) of the serving cell to which the MAC CE is applied.

[0045] The length of this field can be 5 bits;

[0046] CORESET ID: This field indicates the CORESET identified by the parameter ControlResourceSetId, as specified in 3GPP Technical Specification (TS) 38.331 V15.8.0, whose TCI state is indicated in MAC CE format 100. If the value of this field is 0, it can indicate the CORESET configured by the parameter controlResourceSetZero, as specified in 3GPP TS 38.331 V15.8.0. The length of the CORESET ID field can be 4 bits; and

[0047] TCI state ID: This field indicates the TCI state, identified by the parameter TCI-StateId as specified in 3GPP TS 38.331 V15.8.0, applicable to the CORESET identified by the CORESET ID field. If the CORESET ID field is set to 0, the TCI state ID field can refer to the TCI-StateId that indicates the TCI state from the first 64 TCI states in the TCI state pool configured for the PDSCH channel in the active BWP. The TCI state pool can be maintained by adding / modifying or releasing TCI states in the PDSCH configuration (e.g., PDSCH-Config) in the active BWP, such as tci-States-ToAddModList and / or tci-States-ToReleaseList. If the CORESET ID field is set to other non-zero values, the TCI state ID field can refer to the TCI-StateId from another TCI state pool configured for the PDCCH channel in the active BWP. The TCI state pool for the PDCCH channel can be maintained by adding / modifying or releasing TCI states in the parameter controlResourceSet identified by the CORESET ID indicated in MAC CE format 100, such as tci-StatesPDCCH-ToAddList and / or tci-StatesPDCCH-ToReleaseList. The length of the TCI state ID field can be 7 bits.

[0048] In Rel-15 / 16, the BFD RS for detecting beam failure events / conditions can be configured explicitly or implicitly. The explicit configuration of the BFD RS can be provided by explicit signaling from the network (e.g., RRC signaling).

[0049] When the BFD RS is not configured explicitly, the implicit configuration of the BFD RS occurs. Therefore, in the sense of implicit configuration, the term "implicit" is used herein. For implicit configuration, the UE can determine the BFD RS by including the RS in the RS group indicated by the TCI state of each CORESET used by the UE to monitor the PDCCH. If two RS indices are configured for the TCI state, the RS with the QCL type configuration corresponding to the TCI state is included. For example, up to 2 BFD RSs can be configured explicitly for a BWP. In Release 15, up to 3 CORESETs can be configured for each BWP. In Release 16, up to 5 CORESETs can be configured for each BWP for multi-TRP transmission based on multi-PDCCH. For the selection of implicitly configured BFD RS, when the number of PDCCH TCI states (each TCI state corresponding to a CORESET within the relevant BWP) (e.g., 3) is greater than the number of BFD RSs to be selected (e.g., 2), there is no specified rule for selecting the BFD RS.

[0050] The above description related to the implicit configuration of the BFD RS can be applied to beam failure recovery for special cells or SCell.

[0051] When the Radio Link Monitoring (RLM) RS is not configured explicitly, the RLM RS can be determined implicitly. For the implicit configuration of the RLM RS, the UE can select the RLM RS on its own based on the PDCCH reception TCI state. When the number of PDCCH TCI states is greater than the number of RLM RSs to be selected, the following rules (1) and (2) for selecting the RLM RS can be applied:

[0052] (1) The UE selects the required number of RSs provided for the TCI state (or "active TCI state") that is activated for PDCCH reception in the CORESET associated with the search space set, and the search space set order is sorted starting from the shortest monitoring period. As used herein, the (activated / active) TCI state for PDCCH reception can refer to the (activated / active) TCI state applied by the UE to monitor the PDCCH.

[0053] (2) If multiple CORESETs are associated with a search space set having the same monitoring period, the UE determines the order of the CORESETs according to the highest CORESET index as described in, for example, 3GPP TS 38.213 V16.0.0.

[0054] If the active TCI state for PDCCH reception is associated with two RSs, the UE may expect one RS to have QCL type D, and the UE may use this RS (with QCL type D) for radio link monitoring.

[0055] In Release 16, the multi-TRP technology is applied to PDSCH to improve reliability and robustness to meet the URLLC requirements. As one of the multi-TRP features, the code points in the "Transmission Configuration Indication (TCI)" field of the Downlink (DL) Downlink Control Information (DCI) format can indicate up to 2 TCI states for PDSCH scheduling, as Figure 2 shown.

[0056] Figure 2 FIG. shows a TCI code point 202 associated with two TCI states (TCI state #1 204 and TCI state #2 206) according to an embodiment of the present disclosure. As used herein, the TCI code point may be a bit stream carried in the DCI field "TCI". The bit stream carried in the DCI field "TCI" may correspond to different values and thus different code points. Based on the signaling from the BS, each TCI code point may be associated with one or more TCI states. As Figure 2 shown, the TCI code point 202 is associated with TCI state #1 204 and TCI state #2 206.

[0057] When a TCI code point is associated with two TCI states, from the perspective of the UE, the QCL assumptions indicated by the two TCI states can be applied to PDSCH reception. The association between the TCI code point and the TCI state can be signaled via MAC CE signaling.

[0058] For the reliability and robustness of PDCCH, PDCCH transmission may adopt a similar Spatial Division Multiplexing (SDM) method. That is, the UE may receive DCI by applying multiple QCL assumptions. In view of this, the details of the following process need to be provided:

[0059] - A process of indicating multiple TCI states of a CORESET for PDCCH monitoring to a UE; and

[0060] - A process of selecting a BFR. Specifically, for implicit configuration of BFD RS, QCL assumptions from the active TCI states can be used for PDCCH monitoring. Since there are now more QCL type D RSs from the active TCI states for PDCCH, explicit rules are needed to select BFD RS.

[0061] Indication of multiple TCI states of a CORESET

[0062] To indicate multiple active TCI states of a CORESET to a UE, MAC CE signaling or RRC signaling can be used. As used herein, the term "active / activated TCI state for a CORESET" may refer to a TCI state activated by the network and to be applied by the UE to monitor the CORESET. The indication of multiple TCI states of a CORESET can be implemented through a fixed-size MAC CE, a variable-size MAC CE, or RRC configuration.

[0063] Fixed-size MAC CE

[0064] A new MAC CE format can be introduced, which can be identified by a unique Logical Channel Identifier (LCID) and contains a fixed number (e.g., 2) of TCI state IDs for indicating multiple active TCI states of a CORESET. The indicated active TCI states can be restricted within the TCI states configured by RRC for PDCCH monitoring. In another example, the indicated active TCI states can be restricted within a subgroup of the TCI states configured by RRC for PDSCH monitoring.

[0065] The indicated active TCI states can be related to different TRPs. For example, each of the indicated active TCI states can be associated with a TCI state group ID. When two TCI states are activated for a UE to monitor a CORESET, the two activated TCI states may not be associated with the same group ID, as Figure 3 shown.

[0066] Figure 3 FIG. 300 shows a fixed-size MAC CE format according to an embodiment of the present disclosure for indicating two TCI states. The MAC CE format 300 includes the following fields:

[0067] Serving cell ID: This field indicates the ID of the serving cell to which the MAC CE is applied. The length of the field can be 5 bits;

[0068] CORESET ID: This field indicates the CORESET identified by ControlResourceSetId, and as specified in 3GPP TS 38.331 V15.8.0, its TCI state is in MAC CE format 300. If the value of this field is 0, it indicates the CORESET configured by the parameter controlResourceSetZero, as described in 3GPP TS 38.331 V15.8.0. The length of the CORESET ID field can be 4 bits;

[0069] TCI state ID #1: This field indicates the first TCI state, identified by the parameter TCI-StateId as specified in 3GPP TS 38.331 V15.8.0, applicable to the CORESET identified by the CORESET ID field. If the CORESET ID field is set to 0, the field of TCI state ID #1 can refer to the TCI-StateId that indicates the TCI state from the first 64 TCI states in the TCI state pool configured for the PDSCH channel in the active BWP. The TCI state pool can be maintained by adding / modifying or releasing TCI states in the PDSCH configuration (e.g., PDSCH-Config) in the active BWP, such as tci-States-ToAddModList and / or tci-States-ToReleaseList. If the field of CORESET ID is set to other non-zero values, the field of TCI state ID #1 can refer to the TCI-StateId in another TCI state pool configured for the PDCCH channel in the active BWP. The TCI state pool of the PDCCH channel can be maintained by adding / modifying or releasing TCI states in the parameter controlResourceSet identified by the CORESET ID indicated in MAC CE format 300, such as tci-StatesPDCCH-ToAddList and / or tci-StatesPDCCH-ToReleaseList. The length of the TCI state ID #1 field can be 7 bits;

[0070] TCI State ID #2: This field indicates the second TCI state. As identified by the TCI-StateId as specified in TS 38.331 V15.8.0, it applies to the CORESET identified by the CORESET ID field. If the CORESET ID field is set to 0, the field of TCI State ID #2 can refer to the TCI-StateId that indicates the TCI state from the first 64 TCI states of the TCI state pool configured for the PDSCH channel in the active BWP. The TCI state pool can be maintained by adding / modifying or releasing TCI states via tci-States-ToAddModList and / or tci-States-ToReleaseList in the PDSCH configuration (e.g., PDSCH-Config) in the active BWP. If the field of CORESET ID is set to another value other than 0, the field of TCI State ID #2 can refer to the TCI state ID in another TCI state pool configured for the PDCCH channel in the active BWP. The TCI state pool for the PDCCH channel can be maintained by adding / modifying or releasing TCI states in the parameter controlResourceSet identified by the CORESET ID indicated in MAC CE format 300, such as tci-StatesPDCCH-ToAddList and / or tci-StatesPDCCH-ToReleaseList. The field length of TCI State ID #2 can be 7 bits; and

[0071] R: Reserved bit.

[0072] Figure 4 Figure 400 shows a fixed-size MAC CE format for indicating two TCI states according to another embodiment of the present disclosure. Compared with it, R: Reserved bit.

[0073] The "CORESET ID" field has a length of 1 bit to account for the larger number of CORESETs supported in the multi-TRP scenario (i.e., the CORESET ID in MAC CE format 400 is a 5-bit field). It is worth noting that in the multi-TRP scenario, according to the NR version 16 specification, the maximum number of CORESETs in a PDCCH configuration can reach 5. Since each serving cell has up to 4 DLBWPs at most, a 4-bit field as the CORESET ID is not enough.

[0074] Variable-size MAC CE

[0075] A new MAC CE format for indicating the active TCI state of a CORESET can be introduced, which can be identified by a unique LCID and contains a variable number of TCI state IDs. The MAC CE supports the indication of at least two TCI states. The indicated TCI states can be restricted within the TCI states configured by RRC for PDCCH monitoring. In another example, the indicated TCI states can be restricted within a subgroup of the TCI states configured by RRC for PDSCH monitoring. The indicated TCI states can be restricted to be associated with different TRPs. For example, each TCI state can be associated with a TCI state group ID. When two TCI states are indicated for a CORESET, the two TCI states may not be associated with the same TCI state group ID.

[0076] Figure 5 FIG. 500 shows a MAC CE format with variable size for indicating at least two TCI states according to an embodiment of the present disclosure. The MAC CE format 500 may include the following fields:

[0077] Serving cell ID: This field indicates the ID of the serving cell to which the MAC CE is applied. The length of the field can be 5 bits;

[0078] CORESET ID: This field indicates the CORESET identified by ControlResourceSetId, as specified in 3GPP TS 38.331 V15.8.0, whose TCI state is in the MAC CE format 300. If the value of this field is 0, it indicates the CORESET configured by the parameter controlResourceSetZero as described in 3GPP TS 38.331 V15.8.0. The length of the CORESET ID field can be 4 bits;

[0079] TCI State ID: This field indicates the TCI state, as identified by the parameter TCI-StateId as specified in 3GPP TS 38.331 V15.8.0, applicable to the CORESET identified by the CORESET ID field. If the field of CORESET ID is set to 0, the field of TCI state ID may refer to the TCI state ID that indicates the TCI state from the first 64 TCI states of the TCI state pool for the PDSCH channel configuration in the active BWP. The TCI state pool can be maintained by adding / modifying or releasing TCI states, such as in tci-States-ToAddModList and / or tci-States-ToReleaseList in the PDSCH configuration (e.g., PDSCH-Config) in the active BWP. If the CORESET ID field is set to another value other than 0, the TCI state ID field may refer to the TCI-StateId from another TCI state pool for the PDCCH channel configuration in the active BWP. The TCI state pool for the PDCCH channel can be maintained by adding / modifying or releasing TCI states, such as in tci-StatesPDCCH-ToAddList and / or tci-StatesPDCCH-ToReleaseList in the controlResourceSet identified by the CORESET ID indicated in MAC CE format 500. The field length of the TCI state ID may be 7 bits;

[0080] TCI State ID #i (i ≥ 2): This field indicates the i-th TCI state identified by the parameter TCI-StateId, as specified in TS38.331 V15.8.0, applicable to the CORESET identified by the CORESET ID field. If the field of CORESET ID is set to 0, the field #i of TCI State ID indicates the TCI-StateId of the TCI state from the first 64 TCI states in the TCI state pool configured for the PDSCH channel in the active BWP. The TCI state pool can be maintained by adding / modifying or releasing TCI states, for example, in tci-States-ToAddModList and / or tci-States-ToReleaseList in the PDSCH configuration (e.g., PDSCH-Config) in the active BWP. If the field of CORESET ID is set to another non-zero value, the field #i of TCI State ID can refer to the TCI-StateId from another TCI state pool configured for the PDCCH channel in the active BWP. The TCI state pool for the PDCCH channel can be maintained by adding / modifying or releasing TCI states via tci-StatesPDCCH-ToAddList and / or tci-StatesPDCCH-ToReleaseList in the parameter controlResourceSet identified by the CORESET ID indicated in MAC CE format 500. The field length of TCI State ID #i can be 7 bits;

[0081] C i+1 (i ≥ 2): This field indicates the presence of the next octet (or "byte") that provides an indication to TCI State ID #(i + 1). For example, the value of Ci+1 can be set to "1" to indicate the presence of the next octet in MAC CE format 500, and can be set to "0" to indicate the absence. As Figure 5 shown, the C3 field in Oct 3 of MAC CE format 500 is used to indicate whether the next octet (i.e., Oct 4) is included in MAC CE format 500 up to Oct 3; the C4 field in Oct 4 of MAC CE format 500 is used to indicate whether the next octet (i.e., Oct 5, Figure 5 (not shown) is included in MAC CE format 500 up to Oct 4. Therefore, the actual size of MAC CE format 500 is determined by the value of the C i+1 field, and in the sense of "MAC CE format with variable size", the term "variable" is used herein.

[0082] The field of CORESET ID can be extended to 5 bits. And Figure 5In contrast, to accommodate an additional bit in the CORESET ID field, an additional octet can be introduced and redundant bits can be reserved as Figure 6 shown.

[0083] Figure 6 Fig. Figure 6 shows a MAC CE format 600 with variable size for indicating at least two TCI states according to another embodiment of the present disclosure. Note that the positions of the 7 reserved bits (i.e., the R field) are for illustration only. They can also be arranged in other positions. Figure 6 The 1-bit R field “R1” in Figure 6 can be interpreted as a “C2” field in another embodiment to indicate the presence of the TCI state ID#2 field. For example, when R1 = C2 = 0, this means that the octets after Oct 3 (e.g., Oct 4 and Oct 5) do not exist in the MAC CE format 600.

[0084] RRC-based method

[0085] If the MAC CE for indicating the TCI state remains unchanged as specified in the legacy version 15 / 16, additional TCI state groups can be added to the CORESET configuration, resulting in multiple groups of TCI states in the CORESET (RRC) configuration. As used herein, the MAC CE specified in the legacy version 15 / 16 can refer to the MAC CE that indicates only one TCI state to monitor the indicated CORESET. The MAC CE can have a fixed size of 16 bits.

[0086] When receiving a MAC-CE, the activation / deactivation indication provided by the MAC-CE can be applied to all TCI state groups of the indicated CORESET. In one example, the TCI state ID can be directly indicated by the MAC-CE. In one example, the TCI state indication field in the MAC-CE may not directly correspond to the TCI state ID configured in the CORESET (RRC) configuration. Instead, for a CORESET with multiple groups of TCI states, the TCI state indication field can indicate the sequential position of each TCI state group. For example, for each TCI state configured by the CORESET configuration, there is a one-bit field for indicating whether the corresponding TCI state is activated or deactivated. When the i-th field is set to 1, the TCI state with the sequential position i in each group can be activated and mapped to the same code point of the DCI TCI field. In another example, the number of entries in a single group in the CORESET can be the same. The i-th field in the MAC-CE (as described in TS 38.321 V15.8.0) can correspond to the entry index of each TCI state group. When the i-th field is set to 1, the TCI state with the entry index i in each group is activated and mapped to the same code point of the DCI transmission configuration indication (TCI) field. In one example, not all entries are provided with corresponding TCI states. Therefore, the number of activated TCI states associated with the code points of the DCI TCI field can be less than the number of TCI state groups.

[0087] The tci-StatesPDCCH-ToAddList in the ControlResourceSet has two lists. The RRC configuration of the ControlResourceSet can be described as structured information by the Abstract Syntax Notation One (ASN.1) in Table 1.

[0088] As shown in Table 1, the ControlResourceSet can include tci-StatesPDCCH-ToAddList0 (or "List 0") and tci-StatesPDCCH-ToAddList1 (or "List 1"), and the TCI states in List 0 and List 1 are different.

[0089] Table 1

[0090]

[0091]

[0092] The TCI state ID in the MAC CE can correspond to the sequential position of the TCI state ID in the list. Thus, when the MAC CE indicates an active TCI state, the associated TCI states in both lists can be activated simultaneously (e.g., tci-StatesPDCCH-ToAddList0 and tci-StatesPDCCH-ToAddList1 shown in Table 1). For example, assuming that the TCI state IDs in each list are sorted in descending / ascending order according to their values, the i-th TCI state ID in each list (e.g., tci-StatesPDCCH-ToAddList0 and tci-StatesPDCCH-ToAddList1) can be activated for the CORESET by the MAC CE simultaneously. Different lists can correspond to different TRPs.

[0093] Implicitly configured BFD RS selection

[0094] As described above, for multi-TRP based PDDCH reliability enhancement, multiple QCL assumptions can be used to monitor the PDCCH, where each QCL assumption can be indicated by a corresponding TCI state. For beam failure detection purposes, there is an upper limit on the number of BFD RSs, e.g., 2 BFD RSs per BWP, and the number of BFD RSs is less than the total number of TCI states monitored for PDCCH on all relevant CORESETs. The relevant CORESET can be the CORESET configured for the relevant active BWP. When the BFD RS is to be determined implicitly from the TCI state received from the PDCCH, a down-selection of the TCI state is required. For such down-selection, the following can be assumed: When the active TCI state used for PDCCH reception includes two RSs, if the active TCI state is selected for beam failure detection purposes, the UE can assume that one RS has the QCL type, and the UE can use the QCL-type DRS as the BFD RS.

[0095] To select a subgroup of RSs from the TCI state received from the PDCCH for beam failure detection, one or a subgroup combination of the following rules (1) to (11) can be applied:

[0096] (1) The active TCI state in the CORESET associated with the search space set with a shorter monitoring period can be selected first.

[0097] (2) The active TCI state in the CORESET associated with a higher-priority CORESET can be selected first. The higher-priority CORESET can be based on the CORESET index. In one example, the CORESET with a lower (or higher) index can have a higher priority. In another example, the CORESET priority is indicated by base station signaling.

[0098] (3) The active TCI state in the CORESET with a higher or lower CORESET group ID (such as CORESETPoolIndex) can be selected first. In one example, the primary CORESET group can be identified by, for example, the CORESET group ID, and the active TCI state associated with the primary CORESET group can be selected first.

[0099] (4) If there are multiple active TCI states in the CORESET, the default TCI state can be selected from the multiple active TCI states. The default value can be pre-configured, RRC-configured, predefined, or specified in the specification.

[0100] For example, the default value can be

[0101] ● the first (or last) of the multiple active TCI states;

[0102] ● the one with the lowest (or highest) TCI state ID among the multiple active TCI states; or

[0103] ● The TCI state can be associated with a TCI state group index. The default value can be the TCI state associated with the lowest (or highest) TCI state group index. In one example, each of the multiple active TCI states in the CORESET can be associated with a different TCI state group index.

[0104] (5) The TCI state can be associated with a TCI state group index. The PDCCH reception TCI state associated with a lower (or higher) TCI state group index can be selected first. In one implementation, each of the multiple active TCI states in the CORESET can be associated with a different TCI state group index.

[0105] (6) The active TCI state whose QCL RS corresponds to a low-index (or high-index) serving cell can be selected first.

[0106] (7) The active TCI state whose QCL RS corresponds to an in-band serving cell of the associated serving cell can be selected first.

[0107] ■ The relevant serving cell can be the target serving cell for beam failure detection based on the selected BFD RS.

[0108] (8) An active TCI state with a lower (or higher) TCI state ID (e.g., TCI-StateId) can be selected first.

[0109] (9) An active TCI state with a shorter QCL-RS period can be selected first.

[0110] (10) The active TCI state in the CORESET with multiple TCI states can be selected first (or last). For example, the priority (e.g., the first or the last) can be configured by BS signaling. For cases beneficial to multi-TRP, the priority can be "primary". For single-TRP operation, the priority can be "last".

[0111] (11) UE implementation.

[0112] Note that when applying a subgroup combination of the above rules, the order of applying the rule subgroups can be further obeyed. Several such examples are provided below.

[0113] Further note that although the discussion here assumes implicit BFD RS selection, the same principle applies to enhanced implicit RLM RS selection.

[0114] Case #1: Two-stage BFD RS selection

[0115] In this case, for a CORESET with multiple active TCI states, one active TCI state is selected from the multiple active TCI states in stage 1. In the second stage, the required number of TCI states (equal to the number of BFD RSs to be derived) is selected from the remaining active TCI states (a single remaining active TCI state corresponds to a single CORESET). Example details of the two-stage case are described below:

[0116] Stage 1: For a CORESET with multiple active TCI states, the UE can select one active TCI state for BFD RS. The default TCI state can be selected from the multiple active TCI states. The default TCI state can be determined based on the rules described in the "Selection of Implicitly Configured BFD RS" section, that is, the default state can be pre-configured, RRC-configured, predefined, or specified in 3GPP technical specifications. The default TCI state can be

[0117] ● The first (or last) TCI state among the multiple active TCI states;

[0118] ● The TCI state with the lowest (or highest) TCI-StateId among multiple active TCI states;

[0119] ● The TCI state associated with the CORESET pool index of the CORESET (e.g., CORESETPoolIndex), where the CORESETPoolIndex can be used to identify the primary CORESET, which can further correspond to the primary TRP; or

[0120] ● The TCI state associated with the TCI state group index. The default TCI state can be the TCI state associated with the lowest (or highest) TCI state group index. Each of the multiple active TCI states in the CORESET can be associated with a different TCI state group index.

[0121] In one example, an operation of selecting one active TCI state from multiple active TCI states can be performed for each CORESET configured with multiple active TCI states.

[0122] In another example, the operation of selecting one active TCI state from multiple active TCI states may not be performed on each CORESET configured with multiple active TCI states. Instead, if the total number of active TCI states is greater than the required number of BFD RSs, the selection can be performed on the CORESET one by one. When the remaining number of TCI states (including the states from multiple TCI state CORESETs and the states from single TCI state CORESETs) is equal to or less than the required number of BFD RSs, the selection may not be performed on the remaining multiple TCI state CORESETs. Selecting multiple TCI state CORESETs for downward selection of the corresponding multiple TCI states can follow at least one of rules (1) to (11) described in the "Implicitly Configured BFD RS Selection" section, for example, based on the CORESET index. The multi-TCI state CORESET with the highest CORESET index can be selected first for downward selection. As used herein, a "multi-TCI state CORESET" may refer to a CORESET that indicates the activation of multiple TCI states for monitoring the PDCCH. A "single TCI state CORESET" may refer to a CORESET that only indicates the activation of one TCI state for monitoring the PDCCH.

[0123] Phase 2: If the total number of active TCI states in the relevant CORESET is still greater than the number of required BFD RSs (e.g., the number can be 2), the UE can select the remaining TCI states downward to meet the number of required BFD RSs. That is, the UE can determine a subgroup of the remaining TCI states by performing downward selection, where the total number of TCI states in the subgroup meets the number of required BFD RSs (e.g., 2).

[0124] In one example, the remaining TCI states can initially correspond to multiple TCI state CORESETs or to a single TCI state CORESET.

[0125] In one example, the downward selection can be based on the implementation of the UE.

[0126] In one example, the remaining TCI states that initially correspond to multiple TCI state CORESETs can be selected downward first. In another example, the remaining TCI states that initially correspond to a single TCI state CORESET can be selected downward first.

[0127] In one example, when deriving BFD RS from the TCI state for PDCCH reception, the UE can reuse the Release 15 RLM RS selection rule to select the BFD RS.

[0128] In one example, the Release 15 RLM RS selection rule and additional rules for prioritizing certain CORESET group indices or TCI state group indices can be used for BFD RS derivation. For example, the UE can select the required number of RSs for PDCCH reception provided for the active TCI states in the CORESET associated with the search space group in the order of the shortest monitoring period. If more than one CORESET is associated with a search space group with the same monitoring period, the UE can determine the order of the CORESET (or TCI state) from, for example, the highest CORESET group index (or TCI state group index). In one example, the primary CORESET group can be identified by, for example, the CORESET group ID, and the active TCI states associated with the primary CORESET group can be selected first. If more than one CORESET (or TCI state) is associated with the same CORESET group index (or TCI state group index), the UE can determine the order of the CORESET (or TCI state) from, for example, the highest CORESET index (or TCI state index).

[0129] Case 2: RLM-based rules

[0130] In this case, when the UE derives the BSD RS from the TCI state for PDCCH reception, the Release 15 RLM RS selection rule can be used as a baseline. Based on the RLM RS selection, other rules provided in the "Implicitly Configured BFD RS Selection" section (e.g., rules (1) to (11)) can be applied to take into account the fact that a CORESET can be activated by multiple TCI states.

[0131] In one example, if the number of remaining TCI states exceeds the requirement after applying the Release 15 RLM rule, the TCI state with a lower (or higher) TCI state index is selected.

[0132] In one example, if there are still more TCI states than required after applying the Release 15 RLM rule, the TCI state corresponding to the in-band serving cell of the relevant serving cell can be selected first. The relevant serving cell can be the target serving cell for beam failure detection based on the selected BFD RS. If there are still too many, the TCI state with a lower (or higher) TCI state index can be selected.

[0133] Case #3: Prioritize CORESETs with multiple TCI states

[0134] In this case, the TCI state associated with the CORESET with multiple TCI states is preferentially selected. If the number of resulting TCI states is greater than the required number, the rules (1) to (11) listed in the "Implicitly Configured BFD RS Selection" section can be applied for further down-selection. Or, if the number of resulting TCI states is less than the required number, the TCI states related to the 1-TCI state CORESET can also be gradually selected according to the rules (1) to (11) listed in the "Implicitly Configured BFD RS Selection" section, e.g., applying the relevant Release 15 RLM rules.

[0135] In Case #3, the UE can select the TCI state associated with the CORESET with multiple TCI states. If the number of resulting TCI states is greater than the required number, a subgroup of the above resulting TCI states is excluded so that the remaining number of TCI states meets the requirement. The exclusion principle can be based on the UE implementation or the rules (1) to (11) described in the "Implicitly Configured BFD RS Selection" section.

[0136] If the number of resulting TCI states is less than the required number, additional TCI states related to the single-TCI state CORESET can be selected until the total number of selected TCI states meets the requirement.

[0137] In one example, the selection can be the UE implementation.

[0138] In one example, the selection may be based on Release 15 RLM selection rules.

[0139] Case 4: Give priority to CORESETs with 1 TCI state

[0140] In this case, preferentially select the TCI state associated with the CORESET with 1 TCI state. If the number of results of the TCI state is greater than the required number, the rules (1) to (11) listed in the "Implicitly Configured BFD RS Selection" section can be applied for further downward selection. Or, if the number of results of the TCI state is less than the required number, the TCI states associated with multiple TCI state CORESETs can be gradually selected according to the rules (1) to (11) listed in the "Implicitly Configured BFD RS Selection" section until the total number of TCI states meets the required number.

[0141] In Case #4, the UE can select the TCI state associated with the CORESET with 1 TCI state. If the number of results of the TCI state is greater than the required number, exclude a subgroup of the above result TCI states so that the remaining number of TCI states meets the required number. The exclusion principle can be based on the UE implementation or Release 15 RLM selection rules.

[0142] If the number of results of the TCI state is less than the required number, select additional TCI states associated with the CORESET with multiple TCI states until the total number of selected TCI states meets the requirement. The selection can be the UE implementation or based on the RLM-based rules described in Case 2.

[0143] Example methods for BFD RS determination / selection

[0144] Figure 7 A flowchart of a method for BFD RS determination performed by a UE configured with more than one TRP in an active BWP according to an embodiment of the present disclosure is shown. Although operations 702 and 704 are Figure 7 illustrated as separate operations represented as independent blocks in Figure 7 these separately illustrated operations should not necessarily be construed as dependent on order. The order of performing operations in

[0145] In operation 702, the UE may receive at least one MAC CE for TCI state activation. Each MAC CE in the at least one MAC CE may indicate a CORESET and at least one TCI state to be activated to monitor the PDCCH whose physical resources are determined by the configuration of the CORESET indicated by the same MAC CE. One of the at least one MAC CE may indicate more than one TCI state. At least a portion of all TCI states indicated by the at least one MAC CE may belong to a first set of TCI states associated with a first TRP.

[0146] In operation 704, the UE may perform a first operation after determining that the total number of TCI states included in the first set of TCI states is greater than a first threshold number.

[0147] Figure 8 illustrates a Figure 7 flowchart of a first operation according to an embodiment of the present disclosure. As Figure 8 shown, the first operation includes operations 802 and 804.

[0148] In operation 802, the UE may select at least one first TCI state from the first set of TCI states, where the total number of the at least one first TCI states is equal to the first threshold number. In operation 804, the UE may determine at least one first BFD RS for detecting a first beam failure condition of the first TRP based on the at least one first TCI state.

[0149] In one example, among the first set of TCI states, the TCI state associated with the CORESET having the lowest monitoring period among all CORESETs associated with the first set of TCI states may be preferentially selected as one of the at least one first TCI states.

[0150] In one example, among the first set of TCI states, the TCI state associated with the CORESET indicated by one of the at least one MAC CE (i.e., the MAC CE indicating more than one TCI state) may be preferentially selected as one of the at least one first TCI states. If one of the at least one MAC CE includes multiple TCI state IDs, one of the multiple TCI state IDs may indicate a TCI state preferentially selected as one of the at least one first TCI states, where the most significant bit (MSB) of the TCI state ID may be the MSB closest to the MSB of the bit string represented by one of the at least one MAC CE among all MSBs of the multiple TCI state IDs included in one of the at least one MAC CE. Figure 3For example, the MAC CE (or MAC CE format 300) includes TCI state ID #1 and TCI state ID #2. Compared with the MSB of TCI state ID #2, the MSB of TCI state ID #1 is closer to the MSB of the bit string represented by the MAC CE (i.e., the MSB in Oct 1 of MAC CE format 300). Therefore, the TCI state indicated by TCI state ID #1 can be preferentially selected as one of the first TCI states. That is, compared with the TCI state indicated by TCI state ID #2, the UE can first select the TCI state indicated by TCI state ID #1 as the first TCI state for determining the first BFD RS.

[0151] Figure 7 and Figure 8 The method shown above can be performed based on each TRP. For example, if at least another part of the TCI state indicated by at least one MAC CE belongs to a second set of TCI states associated with a second TRP, the UE can also perform a second operation after determining that the total number of TCI states included in the second set of TCI states is greater than a second threshold number. The second operation can include selecting at least one second TCI state from the second set of TCI states (the total number of at least one second TCI state is equal to the second threshold), and determining at least one second BFD RS for detecting the second beam failure condition of the second TRP based on at least one second TCI state.

[0152] In one embodiment, one MAC CE in at least one MAC CE (i.e., the MAC CE that indicates more than one TCI state as described in Figure 7 action 702) can include two TCI states associated with different TRPs. For example, the MAC CE can include a serving cell ID, a CORESET ID, a first TCI state ID, and a second TCI state ID, where the first TCI state ID indicates a TCI state belonging to a first set of TCI states, and the second TCI state ID indicates a TCI state belonging to a second set of TCI states.

[0153] In one embodiment, one MAC CE in at least one MAC CE (i.e., the MAC CE that indicates more than one TCI state as described in Figure 7 action 702) can have a fixed-size format for indicating two TCI states for PDCCH monitoring. As shown in Figure 3 or Figure 4 shown, only two TCI states can be indicated by a MAC CE with a fixed-size format.

[0154] In one embodiment, one MAC CE in at least one MAC CE (i.e., asFigure 7 As described in operation 702, a MAC CE indicating more than one TCI state may have a variable - size format for indicating at least two TCI states for PDCCH monitoring. As Figure 5 shown in or 6, a MAC CE with a variable - size format may indicate two or more TCI states. For example, the variable - size format may be implemented by including an indicator (e.g., Figure 5 the field C shown in or 6) in the MAC CE, where the indicator may be used to indicate the presence of an octet including a third TCI state ID. i )

[0155] Figure 9 FIG. shows a process for BFD RS determination according to an embodiment of the present disclosure. In the shown process, the UE receives four MAC CEs for TCI state activation: MAC CE #1, MAC CE #2, MAC CE #3, and MAC CE #4. MAC CE #1 indicates to activate CORESET #1 and two TCI states (i.e., TCI state #1 and TCI state #2) for monitoring the PDCCH whose physical resources are determined by the configuration of CORESET #1. MAC CE #2 indicates to activate CORESET #2 and two TCI states (i.e., TCI state #3 and TCI state #4) for monitoring the PDCCH whose physical resources are determined by the configuration of CORESET #2. MAC CE #3 indicates to activate CORESET #3 and two TCI states (i.e., TCI state #5 and TCI state #6) for monitoring the PDCCH whose physical resources are determined by the configuration of CORESET #3. MAC CE #4 indicates to activate CORESET #4 and one TCI state (i.e., TCI state #7) for monitoring the PDCCH whose physical resources are determined by the configuration of CORESET #4. Each received MAC CE may have a fixed - size format (e.g., as Figure 1 , 3 or 4 shown) or a variable - size format (e.g., as Figure 5 or 6 shown).

[0156] Among the TCI states (i.e., TCI states #1 to #7) indicated by the received MAC CEs, TCI states #1, #4, #5, and #7 belong to the first group G1 of TCI states, while TCI states #2, #3, and #6 belong to the second group G2 of TCI states. The first group G1 may be associated with the first TRP. The second group G2 may be associated with the second TRP.

[0157] Since the total number of TCI states included in the first group G1 is "four", which is greater than the first threshold number (e.g., two), the UE can perform a down-selection to select two TCI states from the first group G1 as the first TCI state to meet the first threshold number. For example, TCI state #1 and #7 can be selected as the first TCI state based on at least one of rules (1) to (11) described in the "Implicitly Configured BFD RS Selection" section. The UE can determine a first BFD RS for detecting a first beam failure condition of the first TRP based on the first TCI state (e.g., whether the signal quality of the first TRP is lower than a predetermined threshold).

[0158] For the second TRP, since the total number of TCI states included in the second group G2 is "three", which is greater than the second threshold number (e.g., two), based on at least one of rules (1) to (11) described in the "Implicitly Configured BFD RS Selection" section, the UE can perform a down-selection to select two TCI states from the second group G2 as the second TCI state to meet the second threshold number. The UE can then determine a second BFD RS for detecting a second beam failure condition of the second TRP based on the second TCI state (e.g., whether the signal quality to the second TRP is lower than a predetermined threshold).

[0159] The present disclosure provides a method for BFD RS determination. Compared with, for example, the Release 15 / Release 16 NR scenarios, the method is more flexible and applicable to advanced scenarios. At least a part of the method disclosed herein at least supports beam failure recovery in the following scenarios: a large number of TCI states are associated with the CORESET configured for the active BWP, but without increasing UE complexity.

[0160] The following can be used to further disclose terms, examples, embodiments, actions, and / or behaviors:

[0161] Beam failure recovery: Movement in the environment or other events can cause the currently established beam pair to be quickly blocked, without enough time for a regular beam adjustment to adapt to a beam reporting mechanism based on a beam reporting mechanism similar to the CSI (Channel State Information) reporting mechanism that occurs in the PHY channel. The beam failure recovery process handles such events within a short reaction time.

[0162] Beam: The term "beam" here can be replaced by a spatial filter. For example, when the UE reports a preferred gNB TX beam, the UE is essentially selecting the spatial filter used by the gNB. The term "beam information" is used to provide information about which beam / spatial filter is being used / selected. In one embodiment, a single reference signal is transmitted by applying a single beam (spatial filter). Therefore, the term beam or beam information can be represented by a reference signal resource index.

[0163] HARQ: The function ensures delivery between peer entities at layer 1 (i.e., the physical layer). When the physical layer is not configured for downlink / uplink spatial multiplexing, a single HARQ process supports one transport block (TB), and when the physical layer is configured for downlink / uplink spatial multiplexing, a single HARQ process supports one or more TBs. Each serving cell has one HARQ entity. Each HARQ entity supports parallel (number) of DL and UL HARQ processes.

[0164] Timer: The MAC entity can set one or more timers for a single purpose, e.g., to trigger some uplink signaling retransmissions or to limit some uplink signaling retransmission periods. The timer runs after being started until it is stopped or expires; otherwise, it does not run. The timer can be started when not running or restarted when running. The timer always starts or restarts from its initial value. Among them, the initial value can be but is not limited to being configured by the gNB via downlink RRC signaling.

[0165] BWP: A subgroup of the total cell bandwidth of a cell is called a bandwidth part (BWP). Beam width part adaptation is achieved by configuring the UE using the BWP and telling the UE which configured BWP is currently active. To enable bandwidth adaptation (BA) on the PCell, the gNB configures the UE using UL and DL BWP. To enable BA on the SCell in the case of CA, the gNB configures the UE with at least the DL BWP (i.e., there may be none in the UL). For the PCell, the initial BWP is the BWP used for initial access. For the SCell, the initial BWP is the BWP configured for the UE's first operation when the SCell is activated. The UE can be configured with the first active uplink BWP by the firstActiveUplinkBWP IE. If the first active uplink BWP is configured for the SpCell, the firstActiveUplinkBWP IE field contains the ID of the UL BWP to be activated when performing the RRC (re)configuration. If there is no field, the RRC (re)configuration does not impose a BWP switch. If the first active uplink BWP is configured for the SCell, the firstActiveUplinkBWP IE field contains the ID of the uplink bandwidth part to be used when the SCell's MAC is activated.

[0166] The following can be used to further disclose terms, examples, embodiments, actions, and / or behaviors:

[0167] QCL (Quasi-Co-Location): Two antenna ports are said to be quasi-co-located if the properties of the channel for transmitting symbols on one antenna port can be inferred from the channel for transmitting symbols on another antenna port. The above "channel characteristics" may include Doppler shift, Doppler spread, average delay, delay spread, and spatial RX parameters. In the NR specification, these characteristics are divided into different QCL types. For example, QCL type D refers to spatial RX parameters. QCL type D is also referred to as "beam" in this document.

[0168] TCI state: The TCI state contains parameters for configuring the QCL relationship between one or two DL reference signals and a target reference signal group. For example, the target reference signal group can be the DM-RS port of PDSCH or PDCCH.

[0169] Normal SR: Normal SR can be used to request UL-SCH resources (e.g., PUSCH resources) for new transmissions. The UE can be configured with zero, one, or more normal SR configurations. A normal SR configuration can include PUCCH resource groups for SR across different BWPs and cells. For a logical channel, at most one PUCCH resource for SR is configured per BWP. Each normal SR configuration can correspond to one or more logical channels. Each logical channel can be mapped to zero or one normal SR configuration. The normal SR configuration of the logical channel that triggers the BSR (if such a configuration exists) is considered the corresponding normal SR configuration that triggers the SR. When a normal SR is triggered, it should be considered pending until it is cancelled.

[0170] Figure 10 FIG. shows a block diagram of a node 1000 for wireless communication according to an embodiment of the present disclosure. As Figure 10 shown, the node 1000 may include a transceiver 1006, a processor 1008, a memory 1002, one or more presentation components 1004, and at least one antenna 1010. The node 1000 may also include a radio frequency band module, a BS communication module, a network communication module, and a system communication management module, input / output (I / O) ports, I / O components, and a power supply ( Figure 10 not explicitly shown in the figure).

[0171] Each of these components can communicate with each other directly or indirectly through one or more buses 1024. The node 1000 can be a UE or a BS that performs various functions described herein. For example, refer to Figures 1 to 9 .

[0172] A transceiver 1006 having a transmitter 1016 (e.g., a transmitting / transmission circuit) and a receiver 1018 (e.g., a receiving / reception circuit) may be configured to transmit and / or receive time and / or frequency resource partitioning information. The transceiver 1006 may be configured to transmit in different types of subframes and time slots, including but not limited to available, unavailable, and flexibly available subframe and time slot formats. The transceiver 1006 may be configured to receive data and control channels.

[0173] Node 1000 may include various computer-readable media. Computer-readable media can be any available media that node 1000 can access, and include volatile (and non-volatile) media and removable (and non-removable) media. By way of example and not limitation, computer-readable media may include computer storage media and communication media. Computer storage media may include volatile (and / or non-volatile) and removable (and / or non-removable) media implemented according to any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or data).

[0174] Computer storage media may include RAM, ROM, EPROM, EEPROM, flash memory (or other storage technologies), CD-ROM, digital versatile disk (DVD) (or other optical disk storage), magnetic cassettes, magnetic tape, magnetic disk storage (or other magnetic storage devices), etc. Computer storage media does not include propagated data signals.

[0175] Communication media typically embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal (e.g., a carrier wave or other transmission mechanism) and include any information transmission medium. The term "modulated data signal" may refer to a signal that sets or changes one or more of its characteristics in a manner that encodes information in the signal. By way of example, and not limitation, communication media may include wired media such as a wired network or a direct wired connection, and wireless media such as acoustic, radio frequency, infrared, and other wireless media. Any combination of the previously disclosed communication media should also be included within the scope of computer-readable media.

[0176] Memory 1002 may include computer storage media in the form of volatile and / or non-volatile memory. Memory 1002 may be removable, non-removable, or a combination thereof. For example, memory 1002 may include solid-state memory, hard disk drives, optical disk drives, etc. As Figure 10 shown, memory 1002 may store computer-readable and / or computer-executable instructions 1014 (e.g., software code or computer-executable programs) that are configured to cause the processor 1008 to perform the various functions described herein when executed, e.g., with reference to Figures 1 to 9Alternatively, instruction 1014 may not be directly executed by processor 1008, but may be configured to cause node 1000 (e.g., at compile time and execution time) to perform the various functions described herein.

[0177] Processor 1008 (e.g., having processing circuitry) may include intelligent hardware devices, central processing unit (CPU), microcontrollers, ASICs, etc. Processor 1008 may include memory. Processor 1008 may process data 1012 and instructions 1014 received from memory 1002, as well as information via transceiver 1006, baseband communication module, and / or network communication module. Processor 1008 may also process information to be sent to transceiver 1006 for transmission via antenna 1010, and information to be sent to the network communication module for transmission to the CN.

[0178] One or more presentation components 1004 may present data indications to a person or other device. Examples of presentation components 1004 may include display devices, speakers, printing components, vibrating components, etc.

[0179] As can be seen from this disclosure, various techniques may be used to implement the concepts described in this application without departing from the scope of these concepts. Additionally, although the concepts have been disclosed with specific reference to certain embodiments, those of ordinary skill in the art will recognize that changes may be made in form and detail without departing from the scope of these concepts. Therefore, the disclosed embodiments are to be considered illustrative in all respects and not restrictive. It should also be understood that this disclosure is not limited to the specific embodiments disclosed. However, many rearrangements, modifications, and substitutions are possible without departing from the scope of this disclosure.

Claims

1. A method for beam failure detection (BFD) reference signal (RS) determination performed by a user equipment (UE) configured with more than one transmission / reception point (TRP) in an active bandwidth part (BWP), the method comprising: Receiving at least one media access control (MAC) control element (CE) for activation of a transmission configuration indicator (TCI) state, each of the at least one MAC CE indicating a control resource set (CORESET) and at least one TCI state to be activated for monitoring a physical downlink control channel (PDCCH), the physical resources of the PDCCH being determined by the configuration of the CORESET indicated by the same MAC CE, one of the at least one MAC CE indicating a plurality of TCI states, at least a part of the TCI states indicated by the at least one MAC CE belonging to a first group of TCI states associated with a first TRP; And Performing a first operation after determining that the total number of TCI states included in the first group of TCI states is greater than a first threshold number, the first operation comprising: Selecting at least one first TCI state from the first group of TCI states, the total number of the at least one first TCI state being equal to the first threshold number; and Determining at least one first BFD RS for detecting a first beam failure condition of the first TRP based on the at least one first TCI state; Wherein, among the first group of TCI states, the TCI state associated with the CORESET indicated by the one of the at least one MAC CE is preferentially selected as one of the at least one first TCI states.

2. The method according to claim 1, wherein At least another part of the TCI states indicated by the at least one MAC CE belongs to a second group of TCI states associated with a second TRP, and the method further comprises: Performing a second operation after determining that the total number of TCI states included in the second group of TCI states is greater than a second threshold number, the second operation comprising: Selecting at least one second TCI state from the second group of TCI states, the total number of the at least one second TCI state being equal to the second threshold number; and Determining at least one second BFD RS for detecting a second beam failure condition of the second TRP based on the at least one second TCI state.

3. The method according to claim 2, wherein One of the at least one MAC CE includes a serving cell identifier (ID), a CORESET ID, a first TCI state ID, and a second TCI state ID, The first TCI state ID indicates a TCI state belonging to the first group of TCI states, and the second TCI state ID indicates a TCI state belonging to the second group of TCI states.

4. The method according to claim 3, wherein One of the at least one MAC CE has a fixed - size format for indicating two TCI states for PDCCH monitoring.

5. The method according to claim 3, wherein, One of the at least one MAC CE has a variable - size format for indicating at least two TCI states for PDCCH monitoring.

6. The method according to claim 5, wherein, One of the at least one MAC CE further includes an indicator for indicating the existence of an octet including a third TCI state ID.

7. The method according to claim 1, wherein, In the first set of TCI states, among all CORESETs associated with the first set of TCI states, the TCI state associated with the CORESET having the lowest monitoring period is preferentially selected as one of the at least one first TCI states.

8. The method according to claim 1, wherein, One of the at least one MAC CE includes a plurality of TCI state IDs. One of the plurality of TCI state IDs indicates the TCI state that is preferentially selected as one of the at least one first TCI states. Among all the most - significant bits (MSBs) of the plurality of TCI state IDs included in one of the at least one MAC CE, the MSB of the TCI state ID is closest to the MSB of the bit string represented by one of the at least one MAC CE.

9. A user equipment (UE) in which an active bandwidth part (BWP) is configured with more than one transmission / reception point (TRP) for beam failure detection (BFD) reference signal (RS) determination, the UE comprising: A processor; And A memory coupled to the processor, wherein the memory stores at least one computer - executable program that, when executed by the processor, causes the processor to: Receive at least one media access control (MAC) control element (CE) for transmission configuration indicator (TCI) state activation. Each of the at least one MAC CE indicates a control resource set (CORESET) and at least one TCI state to be activated for monitoring a physical downlink control channel (PDCCH). The physical resources of the PDCCH are determined by the configuration of the CORESET indicated by the same MAC CE. One of the at least one MAC CE indicates a plurality of TCI states, and at least a part of the TCI states indicated by the at least one MAC CE belong to a first set of TCI states associated with a first TRP; And Perform a first operation after determining that the total number of TCI states included in the first set of TCI states is greater than a first threshold number. The first operation includes: Select at least one first TCI state from the first set of TCI states, the total number of the at least one first TCI state being equal to the first threshold number; and Determine at least one first BFD RS for detecting a first beam failure condition of the first TRP based on the at least one first TCI state; Wherein, among the first set of TCI states, the TCI state associated with the CORESET indicated by the one MAC CE among the at least one MAC CE is preferentially selected as one of the at least one first TCI states.

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