Method, user equipment and access network node

Abstract

A user equipment (UE) receives, from an access network node, information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE and determines, using the information, a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

Description

METHOD, USER EQUIPMENT AND ACCESS NETWORK NODE

[0001] The present disclosure relates to a communication system. The disclosure has particular but not exclusive relevance to wireless communication systems and devices thereof operating according to the 3rd Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof (including LTE-Advanced, Next Generation or 5G networks, future generations, and beyond), and to beam prediction and beam management.

[0002] Earlier developments of the 3GPP standards were referred to as the Long-Term Evolution (LTE) of Evolved Packet Core (EPC) network and Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), also commonly referred as '4G'. More recently, the terms '5G' and 'new radio' (NR) are used to refer to an evolving communication technology that is expected to support a variety of applications and services. Various details of 5G networks are described in, for example, NPL 1. 3GPP intends to support 5G by way of the so-called 3GPP Next Generation (NextGen) radio access network (RAN) and the 3GPP NextGen core network.

[0003] Under the 3GPP standards, a NodeB (or an eNB in LTE, and gNB in 5G) is the radio access network (RAN) node (or simply 'access node', 'access network node' or 'base station') via which communication devices (user equipments or 'UEs') connect to a core network and communicate with other communication devices or remote servers. For simplicity, the present application will use the term access network node, RAN node or base station to refer to any such access nodes.

[0004] Also for simplicity, the present application will use the term mobile device, user device, or UE to refer to any communication device that is able to connect to the core network via one or more base stations. Although the present application may refer to mobile devices in the description, it will be appreciated that the technology described can be implemented on any communication devices (mobile and / or generally stationary) that can connect to a communications network for sending / receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

[0005] Some of the additional developments in 3GPP relate to the use of artificial intelligence (AI) and machine learning (ML), often abbreviated to AI / ML. Some AI / ML use cases are given below (though it will be appreciated that many use cases may be defined): ●　　Channel state information (CSI) feedback enhancement: e.g., overhead reduction, improved accuracy, prediction; ●　　Beam management: e.g., beam prediction in time, and / or spatial domain for overhead and latency reduction, beam selection accuracy improvement; ●　　Positioning accuracy enhancements for different scenarios including, e.g., those with heavy non-line of sight (NLOS) conditions.

[0006] NPL 1: Next Generation Mobile Networks (NGMN) Alliance, 'NGMN 5G White Paper' V1.0, February 17, 2015 <https: / / www.ngmn.org / 5g-white-paper.html>

[0007] Predictions or inferences generated using an AI / ML model can be used as part of various methods for improving the reliability or efficiency of communications in the network. For example, AI / ML models can be used for beam prediction and beam management (as mentioned above). However, there is a need for improved methods and apparatus for beam prediction. For example, improved methods for determining a receiver (Rx) beam to use for reception of PDSCH or PDCCH are needed for a case where a predicted beam is configured for transmission of the PDSCH or PDCCH. Moreover, there is a need for improved performance evaluation for beam predictions. More generally, there is a need for the development of improved communication devices (such as base stations and / or UEs), and corresponding methods, for beam management and beam prediction.

[0008] The disclosure aims to provide apparatus and methods that at least partially address the above needs and / or issues.

[0009] A method performed by a user equipment (UE) according to a first aspect of the present disclosure, the method comprising: 　　receiving, from an access network node, information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE; and 　　determining, using the information, a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

[0010] A method performed by an access network node according to a second aspect of the present disclosure, the method comprising: 　　transmitting, to a user equipment (UE), information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE, and wherein 　　the information is used by the UE to determine a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

[0011] A user equipment (UE) according to a third aspect of the present disclosure, the UE comprising: 　　means for receiving, from an access network node, information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE; and 　　means for determining, using the information, a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

[0012] An access network node according to a fourth aspect of the present disclosure, the access network node comprising: 　　means for transmitting, to a user equipment (UE), information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE, and wherein 　　the information is used by the UE to determine a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

[0013] Detailed examples of the disclosure will now be described, by way of example, with reference to the accompanying drawings in which:Fig. 1 schematically illustrates a mobile ('cellular' or 'wireless') communication system 1;Fig. 2 illustrates a typical frame structure that may be used in the communication system 1 of Fig. 1;Fig. 3 illustrates a framework in respect of an AI / ML model;Fig. 4 shows an illustration of a method of training an AI / ML model, and of monitoring the performance of the AI / ML model;Fig. 5 illustrates a set of transmitted beams and a set of predicted (non-transmitted) beams;Fig. 6 illustrates a further set of transmitted beams and a set of predicted (non-transmitted) beams;Fig. 7 illustrates TCI state information;Fig. 8 illustrates TCI state information included in a MAC CE;Fig. 9 illustrates a set of CSI-RS transmitted by a base station, and a set of Rx beams for a UE;Fig. 10 illustrates a correspondence between CSI-RS and DL Rx beams;Fig. 11 illustrates a set of transmitted and non-transmitted CSI-RS, and a set of Rx beams for a UE;Fig. 12 illustrates a correspondence between downlink reference signals and actual and predicted DL Rx beams;Fig. 13 illustrates a set of transmitted SSB, a set of non-transmitted CSI-RS, and a set of Rx beams for a UE;Fig. 14 illustrates a correspondence between CSI-RS and the SSBs;Fig. 15 illustrates a correspondence between the SSBs and DL Rx beams;Fig. 16 illustrates transmission of DCI, CSI-RS and PDSCH by a base station;Fig. 17 illustrates TCI state information transmitted by a base station to a UE;Fig. 18 is a schematic block diagram illustrating the main components of a UE 3 for the communication system 1 of Fig. 1;Fig. 19 is a schematic block diagram illustrating the main components of a base station 5 of a distributed type for the communication system 1 of Fig. 1; andFig. 20 is a schematic block diagram illustrating the main components of a core network node or function 7 for the communication system 1 of Fig. 1.

[0014] Overview 　　An exemplary communication system will now be described in general terms, by way of example only, with reference to Figs. 1 to 5.

[0015] Fig. 1 schematically illustrates a mobile ('cellular' or 'wireless') communication system 1 to which examples of the present disclosure are applicable.

[0016] In the communication system 1, user equipment (UEs) 3-1, 3-2, 3-3 (e.g. mobile telephones and / or other mobile devices) can communicate with each other via a (radio) access network ((R)AN) node 5 that operates according to one or more compatible radio access technologies (RATs). In the illustrated example, the RAN node 5 comprises a distributed base station 5 or 'gNB' operating one or more associated cells 9. Communication via the RAN is typically routed through an associated core network 7 (e.g. a 5G / 6G or later generations core network or evolved packet core network (EPC)).

[0017] As those skilled in the art will appreciate, whilst three UEs 3 and one base station 5 are shown in Fig. 1 for illustration purposes, the system, when implemented, will typically include other base stations 5 and UEs 3.

[0018] Each base station 5 controls one or more associated cells 9 either directly, or indirectly via one or more other nodes (such as home base stations, relays, remote radio heads, distributed units, and / or the like). It will be appreciated that the base stations 5 may be configured to support 4G, 5G, 6G, and / or later generations and / or any other 3GPP or non-3GPP communication protocols.

[0019] In this example the illustrated RAN node 5 comprises a distributed base station comprising at least one distributed unit (DU) 5b (e.g., a gNB-DU or the like), and a central unit (CU) 5c (e.g., a gNB-CU or the like). The CU 5c employs a separated control plane and user plane and so is, itself, split between a control plane function (CU-CP) and a user plane function (CU-UP) which respectively communicate, with the DU via appropriate interfaces (e.g. an F1-C interface and an F1-U interface (together forming an F1 interface (or 'reference point'))), and with one another via an appropriate interface (e.g. an E1 logical interface). It will be appreciated that while, in this example, the DU includes the physical and virtual elements required to provide the functionality of the lower parts of the PHY layer and hence communicate with the UEs 3 over the air interface, the RAN may alternatively (or additionally) include one or more separate radio units (RUs) (e.g., providing this functionality of the lower parts of the PHY layer). It will, nevertheless, be appreciated that whilst distributed RAN node 5 is shown and described, the RAN node 5 may be provided in a non-distributed form, for example as an integrated base station (e.g. gNB or eNB).

[0020] The UEs 3 and their serving base station 5 are connected via an appropriate air interface (for example the so-called 'Uu' interface and / or the like). Neighbouring base stations 5 may be connected to each other via an appropriate base station to base station interface (such as the so-called 'X2' interface, 'Xn' interface and / or the like).

[0021] The core network 7 includes a number of logical nodes (or 'functions') for supporting communication in the communication system 1. In this example, the core network 7 comprises control plane functions (CPFs) 10 and one or more network node entities for the communication of user data (e.g. user plane functions (UPFs) 11). The CPFs 10 include one or more network node entities for the communication of control signalling (e.g. Access and Mobility Management Functions (AMFs) 10-1), one or more network node entities for session management (e.g. Session Management Functions (SMFs) 10-2) and a number of other functions 10-n (such as, for example, an Authentication Server Function (AUSF) which facilitates security processes, a Unified Data Management (UDM) entity for managing user specific data (e.g., for access authorization, user registration, and data network profiles), a Policy Control Function (PCF), an Application Function (AF), and / or the like). It will be appreciated that the nodes or functions may have different names in different systems.

[0022] The RAN node 5 is connected to the core network nodes via appropriate interfaces (or 'reference points') such as an N2 reference point between the CU 5c (CU-CP) of the RAN node 5 and the AMF 10-1 for the communication of control signalling, and an N3 reference point between the CU 5c (CU-UP) of the RAN node 5 and each UPF 11 for the communication of user data. The UEs 3 are each connected to the AMF 10-1 via a non-access stratum (NAS) connection over an appropriate reference porint (e.g. an N1 reference point (analogous to the S1 reference point in LTE). It will be appreciated, that N1 communications are routed transparently via the RAN.

[0023] One or more UPFs 11 are connected to an external data network (e.g., an IP network such as the Internet) via an appropriate reference point (e.g. an N6 reference point) for communication of the user data.

[0024] The AMF 10-1 performs mobility management related functions, maintains the NAS connection with each UE 3 and manages UE registration. The AMF 10-1 is also responsible for managing paging. The SMF 10-2 provides session management functionality (that formed part of MME functionality in LTE) and additionally combines some control plane functions (provided by the serving gateway and packet data network gateway in LTE). The SMF 10-2 also allocates IP addresses to each UE 3.

[0025] The base station 5 of the communication system 1 may be configured to operate at least one cell 9 on an associated time-division duplex (TDD) carrier that operates in unpaired spectrum. It will be appreciated that the base station 5 may also operate at least one cell 9 on an associated frequency-division duplex (FDD) carrier that operates in paired spectrum.

[0026] The base station 5 is also configured for transmission of, and the UEs 3 are configured for the reception of, control information and user data via a number of downlink (DL) physical channels and for transmission of a number of physical signals. The DL physical channels correspond to resource elements (REs) carrying information originating from a higher layer, and the DL physical signals are used in the physical layer and correspond to REs which do not carry information originating from a higher layer.

[0027] The physical channels may include, for example, a physical downlink shared channel (PDSCH), a physical broadcast channel (PBCH), and a physical downlink control channel (PDCCH). The PDSCH carries data sharing the PDSCH's capacity on a time and frequency basis. The PDSCH can carry a variety of items of data including, for example, user data, UE-specific higher layer control messages mapped down from higher channels, system information blocks (SIBs), and paging. The PDCCH carries downlink control information (DCI) for supporting a number of functions including, for example, scheduling the downlink transmissions on the PDSCH and also the uplink data transmissions on a physical uplink shared channel (PUSCH). The PBCH provides UEs 3 with the Master Information Block (MIB). It also, in conjunction with the PDCCH, supports the synchronisation of time and frequency, which aids cell acquisition, selection and re-selection. The UE 3 may receive a Synchronization Signal Block (SSB), and the UE 3 may assume that reception occasions of a PBCH, primary synchronization signal (PSS) and secondary synchronization signal (SSS) are in consecutive symbols and form a SS / PBCH block. The base station 5 may transmit a number of synchronization signal (SS) blocks corresponding to different DL beams. The total number of SS blocks may be confined, for example, within a 5 ms duration as an SS burst. The periodicity of the SSB transmissions may be indicated to the UE using any suitable signalling (e.g. per serving cell using ssb-periodicityServingCell). The periodicity value for the SSB may be, for example, greater than or equal to 20 ms. For initial cell selection, the UE 3 may be configured to assume that an SS burst occurs with a periodicity of 2 frames. The UE 3 may also be provided with an indication of which SSBs within a 5 ms duration are transmitted (e.g. using ssb-PositionsInBurst).

[0028] The DL physical signals may include, for example, reference signals (RSs) and synchronization signals (SSs). A reference signal (sometimes known as a pilot signal) is a signal with a predefined special waveform known to both the UE 3 and the base station 5. The reference signals may include, for example, cell specific reference signals, UE-specific reference signal (UE-RS), downlink demodulation signals (DMRS), and channel state information reference signal (CSI-RS).

[0029] Similarly, the UEs 3 are configured for transmission of, and the base station 5 is configured for the reception of, control information and user data via a number of uplink (UL) physical channels corresponding to REs carrying information originating from a higher layer, and UL physical signals which are used in the physical layer and correspond to REs which do not carry information originating from a higher layer. The physical channels may include, for example, the PUSCH, a physical uplink control channel (PUCCH), and / or a physical random-access channel (PRACH). The UL physical signals may include, for example, demodulation reference signals (DMRS) for a UL control / data signal, and / or sounding reference signals (SRS) used for UL channel measurement.

[0030] When the UE 3 initially establishes a radio resource control (RRC) connection with a base station 5 via a cell 9 it registers with an appropriate core network node (e.g., AMF, MME). The UE 3 is in the so-called RRC connected state and an associated UE context is maintained by the network. When the UE 3 is in the so-called RRC idle state, or is in the RRC inactive state, it selects an appropriate cell for camping so that the network is aware of the approximate location of the UE 3 (although not necessarily on a cell level).

[0031] As mentioned above, the base station 5 in this example is a 'distributed' base station 5 that is split between one or more distributed units (DUs) 5b and a central unit (CU) 5c, with a CU 5c typically performing higher level functions and communication with the next generation core, and with the DU 5b performing lower level functions and communication over an air interface with UEs 3 in the vicinity (i.e. in a cell operated by the base station 5). A distributed base station 5 may, for example, include the following functional units hosting the following functions: 　　　　Central Unit (CU): a logical node hosting Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) layers of the base station 5 that controls the operation of one or more DUs. The CU terminates an appropriate interface (e.g. the so-called F1 interface) connected with the DU. 　　　　Distributed Unit (DU): a logical node hosting Radio Link Control (RLC), Medium Access Control (MAC) and Physical (PHY) layers of the base station 5, and its operation is partly controlled by the CU. One DU supports one or multiple cells. One cell is supported by only one DU. The DU terminates an appropriate interface (e.g. the F1 interface) connected with the CU. 　　　　CU-Control Plane (CU-CP): a logical node hosting the RRC and the control plane part of the PDCP protocol of the CU for the base station 5. The CU-CP terminates an appropriate interface (e.g. the so-called E1 interface) connected with the CU-UP and an appropriate interface (e.g. the F1-C (F1 control plane) interface) connected with the DU. 　　　　CU-User Plane (CU-UP): a logical node hosting the user plane part of the PDCP protocol and the SDAP protocol of the CU for the base station 5. The CU-UP terminates an appropriate interface (e.g. the E1 interface) connected with the CU-CP and an appropriate interface (e.g. the F1-U (F1 user plane) interface) connected with the DU.

[0032] Frame Structure 　　Referring to Fig. 2, which illustrates a typical frame structure that may be used in the communication system 1, the base station 5 and UEs 3 of the communication system 1 communicate with one another using resources that are organised, in the time domain, into frames of length 10 ms. Each frame comprises ten equally sized subframes of 1 ms length. Each subframe is divided into one or more slots comprising 14 orthogonal frequency-division multiplexing (OFDM) symbols of equal length.

[0033] As seen in Fig. 2, the communication system 1 supports multiple different numerologies (subcarrier spacing (SCS), slot lengths and hence OFDM symbol lengths). Specifically, each numerology is identified by a parameter, μ, where μ=0 represents 15 kHz (corresponding to the LTE SCS). Currently, the SCS for other values of μ can, in effect, be derived from μ = 0 by scaling up in powers of 2 (i.e. SCS = 15 x 2μkHz). The relationship between the parameter, μ, and SCS (Δf) is as shown in Table 1:

[0034] CU-DU Information Exchange 　　In the communication system 1, various messages may be exchanged between the CU 5c and the DU 5b, for instance during a setup procedure for configuring communication between the DU and CU (e.g., an 'F1 setup procedure'). The purpose of the setup procedure is to exchange application level data needed for the DU 5b and the CU 5c to interoperate correctly (e.g., on the F1 interface). This procedure is the initial procedure triggered for control plane communication (e.g., over the F1-C interface) after a transport network layer (TNL) association has become operational. Typically, this procedure will use non-UE associated signalling.

[0035] During such a procedure, the DU 5b may transmit a setup request message (e.g., an F1 Setup Request) to the CU 5c. Where the setup request message is an F1 Setup Request it may, for example, include the following information: -　　DU Served Cells List IE: Information about the cells supported by the DU and associated features (e.g., NR-U); -　　DU System Information IE.

[0036] It will be appreciated that differently named information elements, having a similar purpose, may be used.

[0037] In response, the CU 5c typically transmits an F1 Setup Response message to the DU 5b. The following information may be included in the F1 Setup Response message: -　　Cells to be Activated List IE: a list of cells that the CU 5c requests the DU 5b to activate.

[0038] Further to the above messages, other messages (with associated information elements) may be used to update the configuration between the CU 5c and the DU 5b. For example, Public Land Mobile Network (PLMN) list, served cell information, DU Configuration Update or CU Configuration Update messages may be used to exchange information between the CU 5c and the DU 5b.

[0039] Additional messaging may be used between the CU 5c and the DU 5b, for instance when establishing a UE's context during a UE Context Setup procedure. The purpose of the UE Context Setup procedure is to establish the UE Context including, signalling radio bearer (SRB), and data radio bearer (DRB). This procedure uses UE associated signalling.

[0040] During such a procedure, the CU 5c may transmit a UE Context Setup Request message to the DU 5b (this message may comprise an RRC container used to carry additional information, e.g. in an RRC information IE). The following information may be included in the UE Context Setup Request message: -　　UE-CapabilityRAT-ContainerList: the DU 5b may take this information into account for UE specific configurations; -　　DRX Cycle IE: the DU 5b may use the provided value from the CU 5c; -　　RRC Information IE; in the case where the CU 5c receives a UEAssistanceInformation IE from the UE 3, the UEAssistanceInformation IE may be included in the RRC Information IE. The DU 5b may, if supported, take the UE's assistance information into account when configuring resources for the UE 3. -　　SRB To Be Setup List; -　　DRB To Be Setup List.

[0041] In response, the DU 5b transmits a UE Context Setup Response message to the CU 5c. The following information may be included in the UE Context Setup Response message: -　　A list of DRBs (and SRBs) which are successfully established and DRBs (and SRBs) which failed to establish; -　　When the DU 5b reports the unsuccessful establishment of a DRB or SRB, an associated cause value should be precise enough to enable the CU 5c to know the reason for the unsuccessful establishment. This may include the reason that a given feature is not supported by the DU 5b; -　　CellGroupConfig: As an Octet string which is included by CU 5c transparently within an RRC reconfiguration message sent to UE 3; -　　DRX Config: As an Octet string which is included by CU 5c transparently within the RRC reconfiguration message sent to UE 3.

[0042] Instead of the above messages, alternative messages (with associated information elements) may be used to update the UE's configuration between the CU 5c and the DU 5b.

[0043] For example, to further update the UE 3 configuration between CU 5c and DU 5b (e.g., DRB / SRB), UE Context Modification Request message (from CU 5c to DU 5b) or UE Context Modification Required (from DU 5b to CU 5c) messages may be used for information exchange between the CU 5c and the DU 5b.

[0044] System information and SIB 　　It will be appreciated that transmissions in a cell 9 of a base station 5 may include one or more broadcast transmissions, one or more unicast transmissions for reception by a UE 3, and / or one or more multicast transmissions for reception by a group of UEs 3. System information (SI) transmitted in a cell may include 'minimum SI' (MSI) and 'other SI' (OSI). The OSI may be broadcast on-demand, for example using a downlink shared channel (DL-SCH). The OSI may be broadcast upon request from a UE 3 that is in a radio resource control (RRC) idle or RRC inactive state. The OSI may also be requested by a UE 3 that is in the RRC connected state, for example via one or more dedicated RRC transmissions.

[0045] The SI may include information for enabling (e.g. configuring) the UE 3 to complete a cell selection, may include information for enabling the UE 3 to complete a cell reselection procedure, or for enabling the UE 3 to receive one or more paging messages transmitted in a cell. SI may be broadcast using a Master Information Block (MIB) and one or more System Information Blocks (SIB).

[0046] The MSI comprises the MIB and system information block 1 (SIB1). The MIB includes information for use by the UE 3 to receive SIB1, for example a subcarrier spacing for SIB1. The MIB provides information corresponding to a Control Resource Set (CORESET) and Search Space. SIB1 may be referred to as 'remaining MSI' (RMSI). SIB1 may be transmitted in a dedicated RRC message, and other SIB (e.g. SIB2 to SIB9) may be transmitting using one or more other suitable RRC transmissions (e.g. another dedicated RRC message). The MIB and SIB1 may provide the UE 3 with an indication of scheduling information for receiving and decoding the other SIB, such as SIB2 to SIB9, and may provide information for use by the UE 3 to receive one or more paging messages. The OSI may comprise, for example, SIB2 to SIB9 transmitted using a downlink sharded channel (DL-SCH) in SI messages. A mapping of SIB2 to SIB9 to corresponding SI messages may be provided to the UE 3 by the base station 5. MIB and SIB1 to SIB9 are described in more detail, for example, in 3GPP TS 38.331. SIB2 provides information for intra-frequency, inter-frequency and inter-system cell reselection. SIB3 provides cell-specific information for intra-frequency cell reselection. SIB4 provides information for inter-frequency cell reselection. SIB5 provides information regarding inter-system cell reselection towards 4G (LTE). SIB6 and SIB7 provide information for an earthquake and tsunami warning system (ETWS). SIB8 provides information for a commercial mobile alert service (CMAS) notification, for example to provide warning text messages to the UE 3. SIB9 includes information regarding coordinated universal time (UTC), global positioning system (GPS) time (e.g. for GPS initialisation) and local time.

[0047] SIB may be broadcast periodically (e.g. according to a predetermined periodic pattern), or alternatively may be provided 'on-demand', for example in response to a request from a UE 3. For example, MIB may be transmitted with a periodicity of 80 ms and repetitions made within 80 ms, and SIB1 may be transmitted with a periodicity of 15c ms and a variable transmission repetition periodicity within 15c ms (e.g. 20 ms). SIB1 can be used to indicate to a UE 3 which SIB are transmitted periodically and which SIB are available on-demand in response to a request from the UE 3. A UE 3 may be configured to request on-demand SIB using message 1 (MSG1), which may be referred to as a MSG1-based on-demand SI request, or message 3 (MSG3), which may be referred to as a MSG3-based on-demand SI request.

[0048] A physical broadcast channel (PBCH) can be used to broadcast the MIB. The base station 5 may transmit the PBCH with synchronisation signals (SS) (e.g. primary synchronisation signal (PSS) and secondary synchronisation signal (SSS)) in a SS / PBCH Block. The SS / PBCH block comprises four orthogonal frequency-division multiplexed (OFDM) symbols that are mapped to PSS, SSS and PBCH associated with a demodulation reference signal (DM-RS). In the frequency domain, an SS / PBCH block comprises 240 contiguous subcarriers. When the UE 3 is in an RRC connected state, the base station 5 may provide the UE 3 with an indication of resources used for the SS / PBCH, for example using dedicated signalling. SIB1 may be transmitted using a physical downlink shared channel (PDSCH). The OSI may be similarly transmitted, for example, using a PDSCH. When one or more beamformed transmissions are transmitted in a cell provided by the base station 5, some of the SI (e.g. some of the SIB) may only be transmitted using particular beams, or using a particular transmission / reception point (TRP).

[0049] CORESET and DCI 　　A CORESET is a set of time-frequency resources for use by a UE 3 to search for downlink control information (DCI) transmitted by a base station on a PDCCH. A CORESET is analogous to the control region at the start LTE subframes. Unlike LTE, in which the frequency domain of the control region corresponds to the total system bandwidth, the frequency domain location for CORESET is localised to a specific region in the frequency domain and has a variable width that can be set to any suitable value (in multiples of 6 resource blocks where each resource block comprises 12 subcarriers in the frequency domain).

[0050] Each CORESET may be up to 3 OFDM symbols in length. The CORESET configured for a UE 3 will typically include one or more UE specific CORESETs configured, for example, by RRC signalling, and one or more common CORESETs configured by system information, for example by a master information block (MIB). The base station 5 is configured to use the MIB to configure an initial CORESET (CORESET 0) in which to search for a PDCCH providing scheduling for the physical downlink shared channel (PDSCH) providing system information block type 1 (SIB1). A PDCCH is made up of a number of (typically 1, 2, 4, 8, 16) control channel elements (CCEs) depending on the required aggregation level (L ∈ {1, 2, 4, 8, 16}). Each CCE is made up of a number of (typically 1, 2 or 3) resource element group bundles (REG bundles) each comprising a number of resource element groups (REGs) made up of resource elements (REs). Each RE is effectively the smallest unit of the resource grid and is made up of one subcarrier in the frequency domain and one OFDM symbol in time domain. A REG corresponds to one resource block (i.e. 12 REs / subcarriers) in the frequency domain and one OFDM symbol in time domain.

[0051] A number of different DCI formats can be used by the base station 5, depending on requirements, for transmission on a PDCCH corresponding to one of the PDCCH candidates in one of the search spaces configured for a given UE 3. For example, the base station 5 may be able to transmit DCI using one or more of the DCI formats set out in Table 2:

[0052] Radio Link Monitoring (RLM) and Radio Link Failure (RLF) 　　The UE 3 may be configured to perform one or more radio link monitoring (RLM) procedures to monitor a radio link for communications. The UE 3 performs measurements for the RLM using the physical layer. The UE 3 performs the measurements to monitor the status of serving cell, and may also perform measurements for candidate cells for lower-layer triggered mobility. The measurement results may be passed to both the MAC and RRC layers at the UE 3. Radio link failure (RLF) can be detected using the measurements and the RRC layer. In other words, the RRC layer evaluates conditions for RLF based on the measurements performed by the UE 3. If it is determined that RLF has occurred, then corresponding RLF procedures are triggered, and RRC Re-establishment may be triggered. Configuration information for beam failure, and beam failure recovery parameters, may also be passed to the MAC layer from the RRC layer. Configuration information for the UE 3 measurements may be passed from the RRC layer to the physical layer, for example a set of radio link monitoring reference signal resources (RLM-RS) may be provided. The RLM-RS may comprise one or more SS / PBCH Blocks (SSB), and / or one or more channel state information reference signals (CSI-RS).

[0053] RLF may occur, for example, due to congestion in a cell of a base station 5, or due to a change in radio conditions (e.g. poor weather, or an obstruction between the UE 3 and the base station 5). In response to detecting RLF, the UE 3 may cease to transmit one or more uplink transmissions to avoid generating uplink interference (e.g. within 40 ms of detecting RLF).

[0054] Artificial Intelligence (AI) / Machine Learning (ML) 　　Fig. 3 illustrates a functional framework for AI / ML models, and how various entities of the framework may interact with one another, that may be implemented in the communication system 1.

[0055] The entities include a data collection function 41, a model training function 43, an inference function 45, an actor 47, a management function 49, and a model storage entity 51.

[0056] The model storage entity 51 may be a reference point for protocol terminations for model transfer and delivery. The AI / ML models could be stored at any suitable node in the network.

[0057] The data collection function 41 provides training data to the model training function 43, inference data to the inference function 45, and monitoring data to the management function 49. The collected data may be, for example, data regarding mobility (e.g. handover of a UE 3, or a location of the UE 3). The data may be obtained, for example, by a UE 3 or a base station 5 (e.g. by receiving a measurement report from a UE 3, or by receiving data from another base station 5 or a core network node / function) and transmitted to another base station 5 or core network node that generates the AI / ML model inference output (or alternatively, the same base station that obtains the data may generate the AI / ML model output).

[0058] The model training function 43 performs the ML model training, validation, and testing, and may generate model performance metrics as part of a model testing procedure. The model training function 43 may output a trained AI / ML model to the model storage entity 51 (though it will be appreciated that the output model may be stored at locations other than model storage entity 51).

[0059] The inference function 45 provides AI / ML model inference output (e.g., predictions or decisions), and the actor 47 is a function or node that receives the output from the inference function 45 and triggers or performs corresponding actions (e.g. a base station 5 that increases / reduces its transmit power, or initiates a handover procedure for a UE 3). The AI / ML model inference output may be, for example, a prediction of mobility (e.g. expected path, route or trajectory, inter-cell or inter-beam mobility, or expected handover) of the UE 3, one or more parameters for use in encoding or decoding transmissions between the base station 5 and the UE 3, or a beam prediction (e.g. receiving (Rx) beam to use to receive a downlink transmission). The inference function 45 may receive an AI / ML model from the model storage entity 51, and inference data from the data collection function 41 for use with the AI / ML model. The inference function 45 may also output monitoring data for use at the management function 49, and receive information indicating an AI / ML to activate or deactivate from the management function 49.

[0060] The management function 49 receives monitoring data from the data collection function 41, and may also receive monitoring data from the inference function 45. The management function 49 may transmit, to the model storage entity 51, an indication of an AI / ML model to be transmitted for use at the inference function 45. The management function 49 may also transmit, to the model training function 43, performance feedback or a retraining request for the AI / ML model.

[0061] The functions illustrated in Fig. 3 may be co-located at a single node of the communications network (e.g. at a base station 5, core network node / function, or UE 3), or may be distributed amongst a plurality of network nodes (e.g. a plurality of (R)AN nodes 5).

[0062] Terms referred to by 3GPP in the context of this framework include: 　　　　AI / ML model training: A process to train an AI / ML Model (by learning the input / output relationship) in a data driven manner and obtain the trained AI / ML Model for inference. Model training can be performed offline or online or combination of both. 　　　　AI / ML model validation: A subprocess of training, to evaluate the quality of an AI / ML model using a dataset different from one used for model training, that helps selecting model parameters that generalize beyond the dataset used for model training. 　　　　AI / ML model testing: A subprocess of training, to evaluate the performance of a final AI / ML model using a dataset different from one used for model training and validation. Differently from AI / ML model validation, testing does not assume subsequent tuning of the model. 　　　　AI / ML model Inference: A process of using a trained AI / ML model to produce a set of outputs based on a set of inputs. 　　　　Data collection: A process of collecting data by the network nodes, management entity, or UE for the purpose of AI / ML model training, data analytics and inference. 　　　　Model monitoring: A procedure that monitors the inference performance of the AI / ML model. 　　　　Model activation: Enable an AI / ML model for a specific function. Model deactivation: Disable an AI / ML model for a specific function. 　　　　Model switching: Deactivating a currently active AI / ML model and activating a different AI / ML model for a specific function. 　　　　Supervised learning: A process of training a model from input and its corresponding labels. 　　　　Unsupervised leaning: A process of training a model without labelled data. 　　　　Semi-supervised learning: A process of training a model with a mix of labelled data and unlabelled data. 　　　　Reinforcement Learning (RL): A process of training an AI / ML model from input (also referred to as 'state') and a feedback signal (also referred to as 'reward') resulting from the model's output (also referred to as 'action') in an environment the model is interacting with.

[0063] The data collection function 41 may be performed at various nodes of the communication network (e.g., at one or more base stations 5 or UEs 3).

[0064] Fig. 4 schematically illustrates of a method of training an AI / ML model, and of monitoring the performance of the AI / ML model. As illustrated in Fig. 4, stored data / features may first be extracted in a data extraction step. In the data validation step, a determination of whether to proceed with training or retaining the AI / ML model is made (e.g., based on the extracted data). In the data preparation stage, the data is prepared for use in training the AI / ML model. For example, the data may be cleaned (e.g., filtered), subject to a transformation, or modified in any other suitable manner. The data may also be divided in training data, validation data and test data sets in the data preparation stage.

[0065] In the model training step, the AI / ML model is trained (or retrained) using training data prepared in the data preparation step. It will be appreciated that any suitable training method can be used to train the AI / ML model (e.g. a method that comprises supervised learning or unsupervised learning). In the model evaluation step, the AI / ML model is evaluated (e.g. a prediction accuracy of the AI / ML model is evaluated) using a test data set (which may be generated in the data preparation step). In the model validation step, a determination of whether the AI / ML model is suitable for deployment in the communication network is made (e.g. based on the results of the model evaluation step).

[0066] In the model serving step, the AI / ML model is deployed for use in the communication system 1. AI / ML model deployment may comprise compiling a trained AI / ML model, packaging the model into an executable format, and delivering the AI / ML model to a target device. For example, the AI / ML model may be transmitted to the base station 5 and / or the UE 3, for use at the base station and / or the UE to generate predictions or determinations using the AI / ML model as part of a prediction service step, as illustrated in the figure. In the performance monitoring step, the performance of the deployed AI / ML model is monitored. The predictive performance of the AI / ML model may be monitored by comparing predictions generated using the model with one or more measurements. For example, when the AI / ML model is used to predict a location of a UE 3, the prediction accuracy of the AI / ML model may be assessed using a measurement of an actual location of the UE 3. Alternatively, if the AI / ML model is used for determining parameters for use in encoding and decoding data transmitted between a base station 5 and a UE 3, the model may be assessed based on the performance of the encoding and / or decoding processes. In the retraining trigger step, retraining of the AI / ML model is triggered (e.g. because the prediction accuracy of the AI / ML model has fallen below an acceptable threshold accuracy, or because a performance of a method that uses inferences from the AI / ML model has fallen below an acceptable threshold performance), and the method returns to the data extraction step.

[0067] As described above with reference to Fig. 3, each step of the method of Fig. 4 may be executed at a single node of the communication system 1, or alternatively steps of the method may be distributed between a plurality of different nodes (or indeed one or more of these steps may be performed online or offline).

[0068] As discussed above with reference to Figs. 3 and 4, information collected by nodes / functions in the communication network (e.g. at a UE 3) can be used as training data for an AI / ML model, and used as inference data for use in generating one or more model inferences using the AI / ML model. The information used as training data, monitoring data, and / or to generate the one or more model inferences may be referred to as 'AI / ML information' or 'AI / ML data'.

[0069] Typically, an AI / ML feature is generally considered as an AI / ML use case, for example spatial beam prediction or temporal beam prediction. Within one AI / ML feature, multiple (different) functionalities may exist, where each functionality may refer to one configuration of an associated AI / ML feature. For example, for spatial beam prediction (an AI / ML feature), different functionalities can be defined in terms of the number of beams predicted by the AI / ML model. Hence, a functionality is defined by configuration of input, output and other applicable conditions (e.g., UE vendor, deployment scenarios) associated with a given AI / ML feature.

[0070] AI / ML model (or models) can provide even finer granularity than AI / ML functionality, but any such AI / ML model may also be defined without any reference to functionality (i.e., each AI / ML feature can have multiple AI / ML models without any functionality definition). An AI / ML model is associated with a configuration related to an AI / ML feature (similar to the above-described definition of AI / ML functionality) and may further include additional detailed aspects such as the version of the model. Hence, if one or more AI / ML functionalities are defined, then each functionality can be associated to multiple AI / ML models.

[0071] Beams and Reference Signals 　　A base station 5 may transmit signals over a plurality of different beam directions. Each beam may have a corresponding index for identifying the beam. For SSB transmissions, the identifying index may be an SSB index. Whilst each beam is transmitted in a generally different direction, it will be appreciated that there may be some spatial overlap between the beams. For SIB1 / SI / paging transmission, there may be one or multiple beam sweeping cycles within a SIB1 / SI / paging transmission window / transmission occasion.

[0072] SSB beams may be transmitted in the time domain as a group of SSB transmissions, which may be referred to as an 'SSB burst set'. Each SSB in the SSB burst set may be referred to as an 'SSB block'. For example, a 5 ms SSB burst set in which SSB beams are transmitted by the base station 5 sequentially within a 5 ms time period may be used, resulting in the 'beam sweeping' effect. However, the burst set need not necessarily be of 5 ms duration. Various other transmission configurations in the time domain may be used depending on the configuration of the base station 5 and the available communication resources.

[0073] The UE 3 and the base station 5 may perform an initial access procedure after the UE 3 has received one of the beamformed signals transmitted by the base station 5, and the UE 3 may be configured to transmit a corresponding measurement report to the base station 5. The UE 3 may perform measurements of, for example, syncronisation signal RSRP (SS-RSRP), reference signal received quality (RSRQ), RSRP and signal to noise interference ratio (RSRP-SINR), or physical broadcast channel demodulation reference signal (PBCH DMRS).

[0074] The UE 3 may be configured to determine an SSB index corresponding to a beam by decoding the PBCH DMRS. The UE 3 may determine a particular beam (and / or corresponding time or frequency resource) to be used for communication with the base station 5 based on corresponding signal measurements performed by the UE 3. Alternatively, the UE 3 may report the measurements to the base station 5, and the base station 5 may determine the beam (and / or corresponding time or frequency resource) to be used for communication with the UE 3.

[0075] The base station 5 is operable to transmit reference signals (RS) in the one or more cells 9 that it operates. These reference signals include channel state information RS (CSI-RS). The CSI-RS may be used by the UE 3 for a number of different purposes including, for example, CSI reporting in which the UE 3 derives channel state information (CSI) including one or more channel quality indicators (CQI), one or more rank indicators (RI), and / or one or more precoding matrix indicators (PMI) from CSI-RS measurements and reports them to the base station 5 in a CSI report. The CQI is an index (typically 4 bits) value representing a signal to interference and noise ratio (SINR). The CQI value also corresponds to a modulation and coding scheme (MCS) to be used for each layer. The RI indicates a number of MIMO transmission layers requested by the UE 3 (albeit the base station 5 might not necessarily use the requested number of MIMO transmission layers). The PMI is used by the UE 3 to report parameters defining a preferred precoding matrix to be applied for downlink transmissions (albeit the base station 5 may not use the requested precoding). A layer indicator (LI) may also be included in the CSI report for identifying the strongest layer from the set of layers indicated by the RI.

[0076] The CSI-RS may also be used by the UE 3 for beam management, including the refinement of initial beam selection based on SSBs. For example, the base station 5 may use a set of relatively broad beams for transmission of the SSBs and a set of narrower (more directional) beams for the CSI-RS. The UE 3 can be configured, by the base station 5, to measure each CSI-RS transmission to identify the best CSI-RS beam and to report this to the base station 5 (e.g., by means of a CSI report including a CSI-RS indicator (CRI) identifying the strongest CSI-RS and hence CSI-RS beam). The UE 3 may also be configured to report the (Layer 1) RSRP which has been measured for the strongest CSI-RS.

[0077] CSI-RS may either be either zero power (ZP-CSI-RS) or non-zero power (NZP-CSI-RS). ZP-CSI-RS are empty resource elements, used primarily for interference measurement. NZP-CSI-RS are used for most of the procedures including channel measurement, beam management, beam measurement, connected mode mobility etc. A non-zero-power CSI-RS may be configured, for example, using a NZP-CSI-RS-Resource information element (IE), or using a CSI-RS-Resource-Mobility field in an CSI-RS-ResourceConfigMobility IE. NZP CSI-RS can be used for interference measurement (IM), for example as part of determining a Signal to Interference plus Noise Ratio (SINR). For cases in which interference is likely to be primarily due to inter-cell interference, CSI IM resources may be used. These resources may be used to measure background interference originating from neighbouring cells. The UE 3 may be provided a configuration for receiving (and measuring) the CSI-RS from the base station 5 (e.g. using a CSI Report Configuration, CSI-ReportConfig, transmitted from the base station 5 to the UE 3). The CSI Report Configuration includes an indication of resources for channel measurement, NZP-CSI-RS resources for interference management, and CSI-IM resources.

[0078] There are also several other ways in which the CSI-RS may be used including, for example, for connected mode mobility, radio link failure detection, beam failure detection / recovery, and fine timing of time and / or frequency synchronisation.

[0079] CSI Reporting 　　The base station 5 can configure how the UE 3 measures CSI-RS and transmits corresponding reports to the base station 5 using appropriate measurement configuration signalling. The base station 5 can, for example, use the measurement configuration signalling (e.g., using a CSI-measconfig IE) to configure the UE 3 to measure and report specific resources used for CSI-RS.

[0080] The base station 5 can also configure the UE 3 to provide CSI reports based on different report timing configurations. For example, the UE 3 may be configured for persistent reporting, semi-persistent reporting on the PUSCH, semi-persistent reporting on the PUCCH, or aperiodic reporting. Aperiodic reporting and semi-persistent reporting on PUSCH may be triggered using a PUSCH DCI. For example, DCI (e.g., using DCI format 0_1) may trigger aperiodic reporting by providing a CSI request that points to a respective index of each of one or more corresponding aperiodic trigger states. Each of these trigger states is associated with one or more corresponding CSI report configurations. Semi-persistent reporting on PUSCH may be triggered in a similar way.

[0081] Each CSI report configuration identifies at least one CSI resource configuration for measurement (e.g., channel measurement). The identified CSI resource configuration is defined by a corresponding IE that includes a list of identifiers corresponding to one or more sets of CSI resources and associated configuration information. The associated configuration information may, for example, identifying an associated bandwidth part and a resource type. The identified resource type may, for example, identify the CSI-RS resource to be a periodic, a semi-persistent, or an aperiodic type. Each resource set comprises one or more specific CSI resource configurations represented by associated identifiers that each point to the specific configuration information for that CSI resource configuration). Accordingly, the base station 5 can configure multiple CSI report configuration instances and CSI resource configuration instances. It will be appreciated that multiple resource sets can be configured per CSI resource config for the case of aperiodic CSI RS resources.

[0082] The CSI-RS transmissions may be beamformed and each CSI-RS resource mapped to a different respective beam (and to an associated set of physical antenna elements). Since the CSI-RS is already beamformed the UE 3 measures the CSI-RS, identifies the one or more directional beams on which it can successfully receive data, and reports the one or more CSI-RS resources associated with the one or more identified beams (or with the best identified beams) to the base station 5. Thus, the base station 5 can schedule resources for the PDSCH (and associated DMRS) using the one or more identified beams and the PDSCH (and associated DMRS) can be precoded / beamformed using the same weights as were used for the CSI-RS beamforming of the identified beams.

[0083] Quasi Co-Location (QCL) and Transmission Configuration Indicator (TCI) 　　It will be appreciated that transmissions that share the same antenna port experience the same propagation channel. However, transmissions using different antenna ports can have radio channels that also share common characteristics, in which case the different antenna ports can be said to be "Quasi Co-Located" (QCL). The characteristics that are common for the radio channels may be, for example, the Doppler shift, Doppler spread, average delay, delay spread, or spatial receiver parameters (properties associated with the downlink received signal angle of arrival at the UE 3), depending on the type of QCL. These characteristics may be referred to as 'large scale' radio channel characteristics. QCL information can be used as part of channel estimation, frequency offset estimation and synchronisation procedures performed by a UE 3. For example, the UE 3 can determine a characteristic for a transmission transmitted using a particular antenna port, and assume that the characteristic is the same for a transmission using a quasi co-located antenna port. It will be appreciated that antenna ports may be geographically separated and yet still have common channel characteristics and be considered to be quasi co-located.

[0084] There are four types of QCL, each type corresponding to a set of channel characteristics that are common between the QCL antenna ports. The four types of QCL and the corresponding common channel characteristics are: ●　　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 ●　　QCL Type D: spatial receiver parameters (for spatial quasi co-location, e.g. the UE 3 can use the same Tx and / or Rx beam for DL reception of PDCCH / PDSCH as used for the quasi co-located transmission)

[0085] The base station 5 may be configured to provide an indication to the UE 3 that the antenna port used for a specific synchronisation signal or reference signal (e.g. CSI-RS) is quasi co-located with an antenna port used for PDSCH or PDCCH. Therefore, by performing a measurement of the synchronisation signal or refence signal, the UE 3 can determine a configuration to be used for transmission or reception of the PDSCH or PDCCH. The base station 5 may provide the indication of which transmissions can be considered to be quasi co-located using RRC signalling, a MAC CE, or DCI (e.g. to provide an indication of which CSI-RS can be considered to be QCL with a PDSCH or PDCCH). A number of "transmission configuration indicator" (TCI) states can be configured for the PDSCH and PDCCH (e.g. up to 128 TCI states for the PDSCH and up to 64 TCI states for the PDCCH). The TCI states are deactivated by default. The TCI includes an indication of the SS / PBCH block or CSI-RS that is QCL with the PDSCH or PDCCH, and an indication of the type of QCL. The UE 3 can receive and decode the PDSCH / PDCCH based on the QCL information indicated by the TCI state. If multiple TCI states are associated with a particular PDSCH or PDDCH, then the base station 5 may provide an indication of which TCI state to use (e.g. using an activation command included in a MAC CE), or the UE 3 may assume, for example, QCL between the PDSCH or PDCCH and an SSB selected during an initial access procedure.

[0086] AI / ML Beam Prediction and Beam Management 　　AI / ML models can be used to predict (generate an inference of) a receiving (Rx) beam for use by the UE 3 for receiving a beamformed signal (e.g. SSB, CSI-RS, PDSCH or PDCCH) transmitted by the base station 5. The Rx beam corresponds to a configuration for use by the UE 3 to receive the beamformed signal (whilst the UE 3 does not form a Rx 'beam' as such, the antenna elements at the UE 3 and the processing of the received signals can be tuned for receiving signals from a particular direction). An AI / ML model can also be used to predicted which of a plurality of beamformed signals (e.g. a set of beamformed SSB, CSI-RS, PDSCH or PDCCH) transmitted in different directions would be received at the UE 3 with the highest signal strength or signal quality. The prediction of which of a plurality of beamformed signals transmitted in different directions would be received at the UE 3 with the highest signal strength or signal quality, and the prediction of which Rx beam to use at the UE 3, may be referred to as spatial-domain DL beam predictions. An AI / ML model can also be used to generate a temporal DL beam prediction (e.g. a time resource to use for transmitting / receiving a downlink transmission).

[0087] The spatial-domain DL beam prediction may be a prediction for a first set of beams based on measurement results from measurements of a second set of beams. For example, Fig. 5 illustrates a first set of beamformed transmissions (70a - 70e), "Set A", and a second set of beamformed transmissions (60a, 60b), "Set B". Set A is the set of beamformed transmissions for which an AI / ML model prediction is generated, and Set B is the set of beamformed transmissions that can be measured by the UE 3 to generate a measurement result for generating the prediction. A spatial-domain DL beam prediction for Set A may be generated based on measurements of one or more of the beamformed signals 60a, 60b of Set B. In this example, Set A and Set B are different, and set B is not a subset of set A. Fig. 6 shows an alternative in which Set B is a subset of set A. In other words, all of the beamformed transmissions 80a-80g illustrated in Fig. 6 belong to Set A, but only a subset of the beamformed transmissions (80a, 80d and 80g) belong to Set B. The network may provide an indication, to the UE 3, of the Set A of beams (for which an AI / ML prediction is to be generated) that is associated with a Set B of beams (for use by the UE 3 to perform a measurement).

[0088] In a further alternative, Set A and Set B could be the same (e.g. for temporal DL beam predictions).

[0089] The AI / ML prediction may comprise a prediction of a DL Tx beam that is to be used. For example, the UE 3 may generate an inference of a DL Tx beam to use for transmission of PDCCH / PDSCH to the UE 3 (a "DL Tx beam prediction"). The UE 3 may also generate, using an AI / ML model, a corresponding prediction of an Rx beam to use to receive the PDCCH / PDSCH. In other words, the AI / ML model can be used to generate a Tx-Rx "beam pair prediction". The UE 3 may transmit, to the base station 5, and indication of the Tx and / or Rx beams inferred using the AI / ML model (or for the case of temporal DL beam predictions, an indication of a time resource, or time instance, generated using the AI / ML model). The UE 3 may also transmit, to the base station 5, an indication of a predicted L1-RSRP for the Tx and / or Rx beams inferred using the AI / ML model. The UE 3 may also transmit, to the base station 5, an indication of confidence of probability associated with the AI / ML model inferences (e.g a confidence associated with a predicted Tx / Rx beam pair).

[0090] The spatial and / or temporal DL beam predictions may be generated using an AI / ML model hosted at the UE 3, but could alternatively be generated using an AI / ML model hosted at the base station 5 (or a model split between the UE 3 and the base station 5). The UE 3 may transmit, to the base station 5, an indication of performance metrics for AI / ML model monitoring. For example, the UE 3 may transmit, to the base station 5, an indication of one or more of: beam prediction accuracy related key performance indicators (KPIs); link quality related KPIs (e.g. throughput, L1-RSRP, L1-SINR, hypothetical block error rate (BLER)); performance metrics based on input / output data distribution; or the L1-RSRP difference evaluated by comparing measured RSRP and predicted RSRP. The UE 3 may also transmit to the base station 5, for AI / ML performance monitoring, one or more of: the one or more best beams obtained by measuring beams of a set indicated by the base station 5; measurements of the one or more predicted best beams corresponding to the AI / ML model output (e.g. a comparison between the actual L1-RSRP and the predicted RSRP); or an indication of the beam corresponding to some or all of the one or more indicated / activated TCI states.

[0091] For PDCCH and PDSCH beam management, the network provides an indication to the UE 3 of a beam used for transmission of PDCCH / PDSCH with respect to a reference signal (e.g. CSI-RS or SSB). As described above, one or more TCI states can be configured for the PDCCH / PDSCH, and the PDCCH / PDSCH transmission is associated with a TCI state. Fig. 7 shows an example of a TCI state, that comprises QCL information. As illustrated in Fig. 7, the TCI state information comprises an indication of a cell, bandwidth part ID (BWP-ID), the type of reference signal associated with the TCI state, and the type of QCL (e.g. type A, type B, type C or type D, as described above) associated with the TCI state. The information is indicated using a QCL-Info information element.

[0092] For example, if a PDCCH transmission is associated with a TCI state that is mapped to "SSB-X", then the UE 3 can assume that the PDCCH transmission will be performed using the same transmission (Tx) beam as SSB-X, and the UE 3 can attempt to the receive the PDCCH using the same Rx beam as used for receiving SSB-X (or predicted to be the best Rx beam for receiving SSB-X).

[0093] For PDCCH reception associated with a particular CORESET, the network may provide an indication, to the UE 3 of the TCI state for reception of the PDCCH. The indication of the TCI state may be provided via an RRC configuration (e.g. tci-StatesPDCCH-ToAddList) for the CORSET. The indication of the TCI state may be provided using a "TCI State Indication for UE-specific PDCCH MAC CE" if the RRC configuration indicates more than one TCI state associated with a CORESET. The TCI State Indication for UE-specific PDCCH MAC CE is illustrated in Fig. 8, and includes an indication of the Serving Cell ID, CORESET ID, and TCI State ID. For beam switching, the base station 5 configures multiple TCI states for a CORESET (which each TCI state is associated with a different SSB index or CSI-RS), and the MAC CE illustrated in Fig. 8 can be used by the base station 5 to indicate the beam switch.

[0094] For PDSCH reception, the network can provide an explicit indication of the TCI state within the scheduling DCI. In this case, the UE 3 can be configured with a list of up to 'M' TCI-state configurations within a higher layer parameter 'PDSCHConfig' to decode the PDSCH, and the UE 3 receives a MAC CE activation command that maps up to 8 TCI states to the codepoints of a DCI field 'Transmission Configuration Indication'. If an indication of a TCI state is not provided to the UE 3, then the UE 3 may use the same Tx / RX beam as used for scheduling DCI reception, to receive the PDSCH.

[0095] The PDCCH Tx beam can be a relatively wide beam for improved robustness against beam failure, whereas the PDSCH transmission beam can be a relatively narrow beam (improving network capacity) that is dynamically indicated to the UE 3.

[0096] Fig. 9 shows an example in which the base station 5 transmits seven different beamformed CSI-RS: CSI-RS1 to CSI-RS 7. Three different Rx beams, Rx1 to Rx 3, that could be used by the UE 3 for receiving a downlink transmission are also illustrated. The UE 3 can perform measurements of each CSI-RS in order to determine which DL Rx beam is the best DL Rx beam for receiving that CSI-RS. For example, Fig. 10 shows an example of a result determination by the UE 3 of which DL Rx beam is the best Rx beam to use for receiving each DL RS (e.g. the UE 3 determines that Rx1 is the best configuration for receiving CSI-RS1, whereas Rx3 is the best Rx beam configuration for receiving CSI-RS7). Based on the correspondence between each CSI-RS and the respective Rx beam (which is determined by measuring each CSI-RS in this example), the UE 3 can determine a DL Rx beam to use to receive PDCCH / PDSCH based on TCI information provided by the network. For example, if the base station indicates, for QCL Type-D, a TCI for PDCCH / PDSCH that maps to CSI-RS6 in the example of Fig. 10, then the UE 3 determines to use the DL Rx Beam 'Rx2' to receive the PDCCH / PDSCH (since Rx2 is mapped to CSI-RS6 in the table of Fig. 10).

[0097] Beam prediction can be used for signalling overhead reduction, for reference signal transmissions. This is because even if a particular reference signal (beam) is not measured by the UE 3, the UE 3 may generate a prediction that the beam would have a relatively high signal strength or signal quality, and so the network may determine to use the Tx beam for transmission of the PDCCH or PDSCH. In other words, the base station 5 may determine to use a particular Tx beam for PDCCH / PDSCH based on an AI / ML model inference, rather than based on a measurement of the beam performed by the UE 3. For example, for PDSCH, the network can use beam predictions (in the time or spatial domain) to schedule PDSCH transmission without transmitting the associated CSI-RS, and therefore reducing the signalling overhead.

[0098] Determination of Tx Beam and / or Rx Beam 　　The inventors have realized that when the network configures a beam predicted by the UE 3 for PDSCH reception, methods for determining, at the UE 3, an Rx beam to use to receive the PDSCH are needed. This is because the UE 3 may not have performed a measurement for the predicted Tx beam. Particularly advantageous methods of determining an Rx beam to use to receive a PDSCH transmission will now be described.

[0099] Determination to use Predicted Rx Beam 　　For beam prediction performed by the UE 3 ('UE-sided' beam prediction), the UE 3 may be configured to predict a DL Rx beam to be used for a particular DL Tx beam. Therefore, when the network selects a particular DL Tx beam for transmission of the PDSCH (or PDCCH), the UE 3 can determine the best DL Rx beam to use to receive the PDSCH (or PDCCH) via the DL Tx beam. In other words, the UE 3 is configured to generate an inference of a DL Rx beam to use with the Tx beam, to form the Tx Rx beam pair.

[0100] Fig. 11 shows an example in which the base station 5 transmits a set of CSI-RS. In this example, the base station 5 transmits three CSI-RS: CSI-RS1, CSI-RS4 and CSI-RS7. Four additional CSI-RS that are not transmitted are also illustrated: CSI-RS2, CSI-RS3, CSI-RS5 and CSI-RS6. Three Rx beams of the UE 3, Rx1 to Rx3, are also shown in Fig. 11. In this example, the UE 3 is configured to predict a DL beam pair (Tx and Rx beams), or to predict a best Rx beam for a corresponding DL Tx beam. Whilst CSI-RS are used in the example of Fig. 11, it will be appreciated that alternatively SSB could be used.

[0101] Fig. 12 shows the DL Rx Beams determined by the UE 3 for each CSI-RS for the example illustrated in Fig. 11. As shown in Fig. 12, the UE 3 determines Rx beams for the CSI-RS transmitted by the base station 5 based on measurements of those CSI-RS (for example, Rx1 '(actual)' for CSI-RS1 that is transmitted by the base station 5). For the CSI-RS that are not transmitted by the base station 5, the UE 3 determines an Rx beam for each of those CSI-RS using an AI / ML model (e.g. Rx2 (predicted) for CSI-RS6). Advantageously, therefore, the UE 3 is able to determine an Rx beam even for the CSI-RS that are not transmitted by the base station 5 (in other words, even for CSI-RS that the UE 3 has not measured). If the base station 5 provides an indication, to the UE 3, of TCI for a PDSCH that maps to a CSI-RS for which the UE 3 has predicted the DL Rx Beam, then the UE 3 can use the predicted Rx Beam to receive the PDSCH. For example, in the example of Fig. 12, if the base station 5 transmits TCI for a PDSCH indicating type-D QCL with CSI-RS6, then the UE 3 can use the predicted Rx2 beam for receiving the PDSCH.

[0102] The UE 3 may provide an indication, to the network, of capability information that indicates a capability of the UE 3 to predict Rx beams and / or Tx beams to use for transmission of the PDSCH. The capability information could be provided to the network by the UE 3 using an RRC message (e.g using UE Capability Information, or UE Assistance Information). The capability information may comprise an indication that the UE 3 only supports DL Tx beam prediction and that Rx beam prediction is not supported. The capability information may comprise an indication that the UE 3 only supports DL Rx beam prediction and that Tx beam prediction is not supported (the network, e.g. base station 5, may be configured to activate this AI / ML model / functionality when network-based DL beam prediction is operational so that the UE 3 can determine the Rx beam without the need to transmit the DL RS). The capability information may comprise an indication that the UE 3 supports Tx beam and Rx beam prediction (in other words, the UE 3 supports beam pair prediction).

[0103] The capability information may also comprise an indication of which reference signals the UE 3 supports beam prediction (Tx and / or Rx) for. For example, the capability information may comprise an indication that the UE 3 supports beam prediction for both CSI-RS and SSB, that the UE 3 supports beam prediction only for SSB, or that the UE 3 supports beam prediction only for CSI-RS.

[0104] The capability information may also comprise an indication of frequency bands (or frequencies) that are supported for beam prediction. The UE 3 beam prediction capability of the UE 3 may depend on the frequencies used for a particular beam. The beam prediction capability of the UE may be indicated, using the capability information, per-frequency band (or per-frequency).

[0105] If the UE 3 supports Rx beam prediction (DL Rx beam prediction only, or both DL Tx beam and Rx beam prediction) for a particular type of reference signal (e.g. CSI-RS and / or SSB), then the network can provide an indication, to the UE 3, of a TCI state that is type-D quasi co-located with that type reference signal that the UE 3 supports for Rx beam prediction. The UE 3 can then use the DL Rx beam predicted for the reference signal for receiving a downlink transmission that is associated with the indicated TCI state.

[0106] Assistance Information for Determination of Rx Beam 　　If the UE 3 is not configured for (capable of) predicting a DL Rx beam, and when a reference signal (e.g. CSI-RS) beam that is QCL type-D with the PDSCH is not transmitted, then the network may provide an indication to the UE 3 that the UE 3 is to determine the DL Rx beam for receiving the PDSCH based on another reference signal (e.g. SSB) that is transmitted by the base station 5 (e.g an SSB that is transmitted in a generally similar direction to the CSI-RS that is not transmitted).

[0107] The network may provide (e.g. via the base station 5) assistance information to the UE 3 for use by the UE 3 to determine a DL Rx beam for DL reception of PDSCH or PDCCH when a QCL Type-D reference signal in the PDSCH / PDCCH TCI state is not transmitted. An indication of a periodic reference signal (CSI-RS or SSB) for the PDSCH / PDCCH TCI state may be provided to the UE 3, for use by the UE 3 for determining the DL Rx beam to use to receive the PDSCH / PDCCH. The base station 5 may determine that the indicated periodic reference signal it to be transmitted (e.g. always transmitted, or transmitted during a particular period of time), so that the UE 3 can perform measurements of the reference signal in order to determine the DL Rx beam. The indication of the periodic reference signal may be included in an RRC configuration (e.g. TCI configuration), or could be provided to the UE 3 dynamically in a DCI scheduling PDSCH transmission. When the RS information is provided in the RRC configuration, then a new (e.g. dedicated) IE could be used (e.g. qcl-Type3 with a new QCL type) that indicates that the UE 3 is to use the reference signal information for DL Rx beam determination. Alternatively, the RS information for the DL Rx determination can be provided as part of a "qcl-InfoPeriodicCSI-RS" information element of a QCL Type-D reference signal PDSCH TCI state.

[0108] When the network provides, to the UE 3, an indication of a TCI state for DL PDSCH / PDCCH transmission, and if a QCL Type-D reference signal associated with the TCI state is not available (or received) by the UE 3 or is not transmitted by the network, then the UE 3 determines to use the reference signal provided in the assistance information to determine the DL Rx beam for the TCI state. The network may be configured to provide (e.g. via the base station 5) the assistance information to the UE 3 when a QCL Type-D reference signal associated with a PDSCH is not being transmitted or is a predicted beam. Alternatively, PDSCH information provided to the UE 3 by the network may be configured so that it contains at least one of: ●　　An indication of a QCL Type-D reference signal that is transmitted; or ●　　The assistance information for a reference signal (described above) that can be used for Rx beam determination for the PDSCH.

[0109] Fig. 13 shows an example in which the base station transmits three SSB beams (SSB1, SSB2 and SSB3), but does not transmit a set of CSI-RS (CSI-RS1 to CSI-RS 6). As shown in Fig. 14, each CSI-RS is associated with a respective one of the SSB (CSI-RS1 and CSI-RS2 are associated with SSB1, CSI-RS3 and CSI-RS4 are associated with SSB2, and CSI-RS5 and CSI-RS6 are associated with SSB3). The associations between the CSI-RS and the SSB are based on the CSI-RS beams being transmitted in a generally similar direction to the respective SSB beams (e.g. as shown in Fig. 13 CSI-RS 5 and CSI-RS 6 are transmitted in a direction that is similar to the direction that SSB3 is transmitted). For each transmitted SSB the UE 3 can perform a measurement of the SSB and determine the best Rx beam. In this example, as shown in Fig. 15, the UE 3 has determined, based on measurements of the SSB, that Rx1 is the best Rx beam for receiving SSB, Rx2 is the best Rx beam for receiving SSB2, and Rx2 is also the best Rx beam for receiving SSB3. Advantageously, by virtue of the correspondence information between the CSI-RS and the SSB, the UE 3 is able to determine an Rx beam to receive a DL transmission that is quasi co-located with a CSI-RS beam, even when the UE 3 has not measured the CSI-RS beam and cannot predict an Rx beam for the CSI-RS beam. For example, if the base station provides an indication that a PDSCH transmission is quasi co-located with CSI-RS5, the UE 3 is able to determine that SSB3 is associated with CSI-RS5, and therefore determine (using the information illustrated in Fig. 15) that Rx2 is to be used to receive the PDSCH.

[0110] Transmission of QCL RS for Determination of Rx Beam 　　If the UE 3 is not configured for (capable of) predicting a DL Rx beam, then the network may schedule transmission of a QCL Type-D reference signal for use by the UE 3 to determine a downlink Rx beam. In other words, if a reference signal that is QCL Type-D for a PDSCH or PDCCH to be transmitted, but that reference signal is not currently transmitted, then the network (e.g. base station 5) may determine to transmit the QCL Type-D reference signal so that the UE 3 can perform a measurement of the reference signal and determine an Rx beam to use to receive the PDSCH or PDCCH.

[0111] Fig. 16 shows an example in which DCI, corresponding to a PDSCH, is transmitted to the UE 3. A QCL Type-D reference signal indicated in the TCI state (e.g. 'TCI-X') of the DCI is not transmitted by the base station 5. Therefore, the base station determines to transmit another reference signal, for measurement by the UE 3 so that the UE 3 can determine an Rx beam to use to receive the PDSCH. In this example, the base station 5 determines to transmit CSI-RS Y, and transmits CSI-RS Y in the next CSI-RS Y occasion. The UE 3 receives the CSI-RS and is therefore able to determine the DL Rx beam to use to receive the PDSCH (since CSI-RS Y transmitted by the base station 5 is QCL Type-D with the PDSCH). The base station 5 configures a time gap between transmission of the DCI and transmission of the PDSCH, to allow the reference signal to be transmitted and for to allow the UE 3 to determine the Rx beam to use to receive the PDSCH.

[0112] The QCL Type-D reference signal associated with the TCI state may be periodic, but the network may have provided an indication to the UE 3 that the reference signal is not currently transmitted. Alternatively, the reference signal may be semi-persistent or aperiodic and the network may not be performing transmission of the reference signal. The network may then determine to transmit the reference signal so that the UE 3 can determine the Rx beam for the PDSCH / PDCCH.

[0113] When the network (e.g. base station 5) provides an indication to the UE 3 of the TCI state for which QCL Type-D reference signal measurements are not available at UE (or cannot be performed since the reference signal is not currently transmitted), then network indicates to the UE 3 that transmission of the QCL Type-D reference signal shall be performed before the PDSCH / PDCCH transmission, for use by the UE 3 to determine the DL Rx beam for the PDSCH / PDCCH.

[0114] In one option, the indication of the reference signal activation (or 'trigger') can be provided to the UE 3 by the network using different DCI to the DCI that indicated the TCI state. In this case, the DCI includes an indication that transmission of the reference signal (e.g. CSI-RS, SSB, DM-RS) has started (or will start), and may include an indication of a time resource used to transmit the reference signal.

[0115] In another option, the indication of the reference signal activation (or 'trigger') can be included as an explicit indication in the DCI that indicates the TCI for the downlink transmission. The indication may be provided using a coded bit that indicates whether the reference signal is transmitted or not. As illustrated in Fig. 17, the DCI indicating the TCI for the DL transmission may include a field in the TCI state that indicates whether the reference signal is transmitted or not. In the example of Fig. 17, the TCI state information includes a 'qcl-Method-r19 CHOICE{Predicted, Not-Predicted}' information element, where 'predicted' indicates that the reference signal is not transmitted, and 'not predicted' indicates that the reference signal is transmitted.

[0116] In a further option, the indication of the reference signal activation (or 'trigger') is implicitly indicated using the DCI that indicates the TCI for the downlink transmission. The UE 3, after receiving the DCI indicating the TCI state, assumes that the associated QCL Type-D reference signal will be transmitted by the network, based on an RRC configuration provided to the UE 3 for the reference signal. The RRC configuration could alternatively control whether the UE 3 is to assume (after receiving the DCI for the TCI state) that the QCL Type-D reference signal transmission is active or not.

[0117] The reference signal transmitted so that the UE 3 can determine the Rx beam to use to receive the PDSCH / PDCCH need not necessarily be the same reference signal as the reference signal indicating within the TCI state configuration. Alternatively, the transmitted reference signal could be a standalone DM-RS that is QCL Type-D with the PDSCH transmission / TCI state, that is transmitted so that the UE 3 can determine the DL Rx beam. Alternatively, a different reference signal could be used (e.g. CSI-RS), other than the reference signal indicated in the TCI state for QCL Type-D, and the transmission of the different reference signal could be configured by the network to have the same QCL Type-D as the TCI state. For example, the network may provide a different CSI-RS / DM-RS configuration that only covers a relatively small part of the cell bandwidth to allow the UE 3 to determine the DL Rx beam. When DL Rx beam determination is required, then the network indicates transmission of this reference signal to the UE 3. The standalone DM-RS, or the different reference signal, may be configured within a TCI state or using the QCL information. For example, as shown in Fig. 17, the TCI state information includes an indication of a DM-RS (DMRS-Index) that is transmitted (or will be transmitted) for use by the UE 3 to determine the Rx beam.

[0118] As illustrated in Fig. 16, the base station 5 may transmit multiple repetitions of the reference signal in between the transmission of the DCI and transmission of the PDSCH, in order to allow Rx beam sweeping to be performed by the UE 3 to determine the Rx beam to use for reception of the PDSCH. The repetitions of the reference signal could be indicated in the reference signal configuration (e.g. CSI-RS configuration), or could be indicated within the DCI that triggers the reference signal transmission.

[0119] After receiving the DCI comprising the TCI state, the UE 3 performs measurement of the QCL Type-D reference signal and determines the DL Rx beam. The UE 3 may be configured to expect that the first symbol of the QCL Type-D reference signal transmission occurs after at least a predetermined threshold time duration following the last symbol of the DCI that indicates activation (transmission) of the reference signal. The UE 3 may also be configured to expect that the first symbol of the downlink transmission (PDSCH) will occur after at least a predetermined threshold time duration following the last symbol of the QCL Type-D reference signal.

[0120] The UE 3 may provide capability information to the base station that indicates whether the UE 3 is capable of receiving a PDSCH transmission for which the QCL Type-D reference signal is not transmitted periodically. The UE 3 may provide capability information to the base station that indicates whether the UE 3 is capable of determining an Rx beam using a DM-RS or CSI-RS that is transmitted over a small number of resource blocks. The UE 3 may provide capability information to the base station that indicates whether the UE 3 is capable of determining the Rx beam using a QCL Type-D reference signal (e.g. CSI-RS, SSB, or DM-RS) after receiving DCI scheduling PDSCH, but before reception of the PDSCH (the capability information may include an indication of how much time is needed by the UE 3, following the last symbol of the QCL Type-D reference signal, to determine the Rx beam).

[0121] If more than one method is available to the UE 3 for determining the DL Rx beam, then the UE 3 may determine the DL Rx beam using the following priority order (where 1 is the highest priority and 3 is the lowest priority): 1)　　The UE 3 shall use actual measurements of a QCL Type-D reference signal for DL Rx beam determination. 2)　　The UE 3 shall use the UE's predicted DL Rx beam for determining the DL Rx beam (e.g. using any of the methods for DL Rx beam prediction described above). 3)　　The UE 3 shall use network assistance information (e.g. any of the assistance information described above) for DL Rx determination.

[0122] Alternatively, the UE 3 may determine the DL Rx beam using the following priority order (where 1 is the highest priority and 3 is the lowest priority): 1)　　The UE 3 shall use actual measurements of a QCL Type-D reference signal for DL Rx beam determination. 2)　　The UE 3 shall use network assistance information (e.g. any of the assistance information described above) for DL Rx determination. 3)　　The UE 3 shall use the UE's predicted DL Rx beam for determining the DL Rx beam (e.g. using any of the methods for DL Rx beam prediction described above).

[0123] Determination of Performance Metrics for PDSCH Beam Prediction 　　The inventors have realised that there is a need for performance metrics to use for evaluating PDSCH based beam prediction (the number of beam failures cannot be used, since this is only applicable for PDCCH based beam prediction, and beam prediction may be applicable only for PDSCH transmissions which cannot lead to beam failure / recovery). Information that can be used to evaluation the performance of beam prediction will now be described.

[0124] Whether a DL Tx beam for PDSCH is correctly predicted or not can affect the performance of the PDSCH transmission / reception. The beam prediction may fail because the DL Tx is not correctly (or acceptably) predicted for the PDSCH transmission, or may fail because the UE 3 is not able to determine the correct (or acceptable) DL Rx beam for PDSCH reception. For both cases, incorrect (or inadequate) beam prediction results in PDSCH decoding failure. The inventors have realized, therefore, that one or more of the following events can be used to evaluate the performance of the beam prediction: ●　　Event 1: PDSCH decoding failure occurrence. ●　　Event 2: HARQ NACK reported by the UE 3 to the network for a PDSCH transmission. ●　　Event 3: The UE 3 receiving retransmission grants for the same PDSCH transport block (TB).

[0125] When performance evaluation for the beam prediction is performed by the base station, HARQ ACK / NACK report information may already be available at the base station 5 for determining whether the beam prediction is operating correctly. However, for the case of UE based performance evaluation, or when the UE 3 transmits a monitoring report to the network for performance evaluation, events 1 to 3 described above can be used to evaluate the AI / ML beam prediction performance. For example, the UE 3 may accumulate or average Event 1, Event 2 or Event 3 over a time window to determine whether 'predicted PDSCH failure' has occurred. For example, the UE 3 may accumulate a number of event occurrences, or perform averaging of the number of event occurrences during a time window. The time window may be a sliding time window, or a time window that is triggered by the occurrence of one of the events that is used for performance monitoring. The time window could be specified in terms of seconds of ms (or any other suitable unit of time), or could alternatively be defined with respect to a number of PDSCH receptions. The number of the events (or average number of the events) can be used to trigger transmission of a performance monitoring report from the UE 3 to the network, or for performance evaluation to be performed at the UE 3. The criteria for transmission of the performance monitoring report or initiation of the performance evaluation may be that the 'predicted PDSCH failure' metric exceeds a predetermined threshold. The threshold may be configured by the network (e.g. via the base station 5), or could be pre-configured at the UE 3. Alternatively, the 'predicted PDSCH failure' metric may be compared against a 'Non-predicted PDSCH failure" metric. The 'Non-predicted PDSCH failure' metric may be computed in a similar manner as for the 'predicted PDSCH failure' metric, but only those events are counted for which PDSCH transmission performed using a non-predicted beam. If the predicted PDSCH failure' metric is greater than the "Non-Predicted PDSCH Failure" by a threshold value then performance monitoring report or performance evaluation is triggered. In other words, the performance of PDSCH reception based on the predicted Rx beam can be compared to PDSCH reception based on a non-predicted Rx beam to determine whether to transmit the performance monitoring report, or to initiate performance evaluation at the UE 3. The threshold value may be configured by the network, or may be pre-configured at the UE 3.

[0126] If the UE 3 has determined to transmit a performance monitoring report for the DL Rx beam prediction to the network, the UE 3 includes the performance metric in the report transmitted to the network. If the UE 3 determines to perform performance evaluation for the for the DL Rx beam prediction at the UE 3, then the UE 3 uses the performance metric for evaluation of the DL Rx beam prediction.

[0127] In order for the UE 3 to determine whether a TCI state associated with PDSCH transmission corresponds to a predicted beam or not, the network may provide an indication of which beams corresponds to transmitted beams and which beams correspond to predicted (non-transmitted) beams.

[0128] The network may provide a list of reference signals (e.g. CSI-RS / SSB) that are predicted beams and a list of reference signals that are transmitted beams. The UE 3 may be configured to determine whether an indicated TCI state corresponds to a predicted beam if the associated reference signal does not belong to the indicated list of transmitted beams (or any other QCL Type-D reference signal corresponding to the list of transmitted beams). Alternatively, the UE 3 may determine the set of transmitted beams as the set of reference signals for which the network has indicated are for use as an AI / ML model input. All other reference signals may be assumed by the UE 3 to belong to the set of predicted beams. The UE 3 determines whether an indicated TCI state corresponds to a predicted beam if the associated reference signal does not belong to the indicated list of transmitted beams (or any other QCL Type-D reference signal corresponding to the list of transmitted beams).

[0129] In a further alternative, the UE 3 is configured to determine that an indicated TCI state corresponds to a predicted beam if the UE 3 has not performed measurement using the associated reference signal for at least a threshold time duration.

[0130] In a further alternative, the UE 3 is configured to determine that an indicated TCI state corresponds to a predicted beam if the network is not performing periodic transmission of the associated reference signal.

[0131] User Equipment 　　Fig. 18 is a schematic block diagram illustrating the main components of a UE 3 as shown in Fig. 1.

[0132] As shown, the UE 3 has a transceiver circuit 310 that is operable to transmit signals to and to receive signals from a base station 5 via one or more antenna 330 (e.g., comprising one or more antenna elements). The UE 3 has a controller 370 to control the operation of the UE 3. The controller 370 is associated with a memory 390 and is coupled to the transceiver circuit 310. Although not necessarily required for its operation, the UE 3 might, of course, have all the usual functionality of a conventional UE 3 (e.g. a user interface 35b, such as a touch screen / keypad / microphone / speaker and / or the like for, allowing direct control by and interaction with a user) and this may be provided by any one or any combination of hardware, software, and firmware, as appropriate. Software may be pre-installed in the memory 390 and / or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example.

[0133] The controller 370 is configured to control overall operation of the UE 3 by, in this example, program instructions or software instructions stored within memory 390. As shown, these software instructions include, among other things, an operating system 410, a communications control module 430, and a beam prediction module 450.

[0134] The communications control module 430 is operable to control the communication between the UE 3 and its one or more serving base stations 5 (and other communication devices connected to the base station 5, such as further UEs and / or core network nodes). The communications control module 430 is configured for the overall handling uplink communications via associated uplink channels (e.g. via a physical uplink control channel (PUCCH), random access channel (RACH), and / or a physical uplink shared channel (PUSCH)) including both dynamic and semi-static signalling (e.g., SRS). The communications control module 430 is also configured for the overall handling of receipt of downlink communications via associated downlink channels (e.g. via a physical downlink control channel (PDCCH) and / or a physical downlink shared channel (PDSCH)) including both dynamic and semi-static signalling (e.g., CSI-RS). The communications control module 430 is responsible, for example: for determining where to monitor for downlink control information (e.g., the location of CSSs / USSs, CORESETs, and associated PDCCH candidates to monitor); for determining the resources to be used by the UE 3 for transmission / reception of UL / DL communications (including interleaved resources and resources subject to frequency hopping); for managing frequency hopping at the UE side; for determining how slots / symbols are configured (e.g., for UL, DL or SBFD communication, or the like); for determining which one or more bandwidth parts are configured for the UE 3; for determining how uplink transmissions should be encoded; for applying any SBFD specific communication configurations appropriately; and the like. The communications control module 430 may be configured to control communications in accordance with any of the methods described above (for example, to transmit a measurement report according to any of the methods described above).

[0135] The beam prediction module 450 is responsible for performing control as part of beam prediction or beam prediction performance evaluation methods. For example, the beam prediction module 450 may be configured to generate one or more DL Rx beam predictions for reception of PDSCH or PDCCH. The beam prediction module 450 may be configured to perform control as part of any of the beam prediction methods described above.

[0136] RAN (Distributed Type) 　　Fig. 19 is a simplified block schematic illustrating the main components of a distributed RAN node 5 comprising a distributed type of base station 5 for implementation in the system of Fig. 1.

[0137] As shown, the RAN node 5 includes a central unit 5c and a distributed unit 5b (although it may include other DUs as described above). Each unit 5c, 5b includes respective transceiver circuitry 51c, 51b.

[0138] The distributed unit 5b transceiver circuitry 51b is operable to transmit signals to and to receive signals from UEs 3 via an air interface 53b and one or more antennas and is also operable to transmit signals to and to receive signals from the central unit 5c via an interface, for example the distributed unit side of an F1 interface (which may be provided over a satellite radio interface).

[0139] The central unit 5c transceiver circuitry 51c is operable to transmit signals to and to receive signals from functions of the core network 7 and / or other RANs via a network interface 55c. The network interface typically includes an N2 and / or N3 interfaces for communicating with the core network 7 and a base station to base station (e.g. Xn) interface for communicating with other RANs. The central unit 5c transceiver circuitry 51c is also operable to transmit signals to and to receive signals from one or more distributed units 5b, for example the central unit side of the F1 interface provided.

[0140] Each unit 5c, 5b includes a respective controller 57c, 57b which controls the operation of the corresponding transceiver circuitry 51c, 51b in accordance with software stored in the respective memories 59c and 59b of the distributed unit 5b and the central unit 5c. The software of each unit may be pre-installed in the memory 59c, 59b and / or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example. The software of each unit includes, among other things, a respective operating system 61c, 61b, a respective communications control module 63c, 63b and an L1 / L2 mobility module 65c, 65b.

[0141] Each communications control module 63c, 63b is operable to control the communication of its corresponding unit 5c, 5b including the communication from one unit to the other. The communications control module 63b of the distributed unit 5b controls communication between the distributed unit 5b and the UEs 3, and the communications control module 63c of the central unit 5c controls communication between the central unit 5c and other network entities that are connected to the distributed RAN.

[0142] The communications control modules 63c, 63b also respectively control the part played by the distributed unit 5b and central unit 5c in the flow of uplink and downlink user traffic and control data to be transmitted to the communications devices served by the RAN including, for example, control data for managing operation of the UEs 3. Each communication control module 63c, 63b is responsible, for example, for controlling the respective part played by the distributed unit 5b and central unit 5c in the reception and decoding of uplink communications, via associated uplink channels (e.g. via a physical uplink control channel (PUCCH), a random-access channel (RACH), and / or a physical uplink shared channel (PUSCH)) including both dynamic and semi-static signalling (e.g., SRS). Each communication control module 63c, 63b is responsible for controlling the respective part played by the distributed unit 5b and central unit 5c in the transmission of downlink communications via associated downlink channels (e.g. via a physical downlink control channel (PDCCH) and / or a physical downlink shared channel (PDSCH)) including both dynamic and semi-static signalling (e.g., CSI-RS, SSBs etc.).

[0143] It will be appreciated that the communications control modules 63c, 63b may also include a number of sub-modules (or 'layers') to support specific functionalities for the corresponding unit 5c, 5b. The modules included will depend on how the corresponding unit 5c, 5b is configured (e.g., the precise CU-DU split). For example, the communications control modules 63c of the distributed unit 5b may include a PHY sub-module, a MAC sub-module, and an RLC sub-module, whereas the communications control modules 63c of the central unit 5c may include a PDCP sub-module, an SDAP sub-module, an IP sub-module, an RRC sub-module, etc.

[0144] The beam prediction module 65b, 65c is responsible for performing control as part of beam prediction or beam prediction performance evaluation methods. For example, the beam prediction module 65b, 65c may be configured to evaluate a beam prediction performed by a UE 3 based on a report received from the UE 3. The beam prediction module 65b, 65c may be configured to perform control as part of any of the beam prediction methods described above.

[0145] Core Network Node / Function 　　Fig. 20 is a block diagram illustrating the main components of a core network node or function, such as the AMF, CPF, the UPF, the SMF or OAM. As shown, the core network function includes a transceiver circuit 710 which is operable to transmit signals to and to receive signals from other nodes (including the UE 3, the base station 5, and other core network nodes) via a network interface 720. A controller 730 controls the operation of the core network function in accordance with software stored in a memory 740. The software may be pre-installed in the memory 740 and / or may be downloaded via the communication system 1 or from a removable data storage device (RMD), for example. The software includes, among other things, an operating system 750, and a communications control module 760.

[0146] The communications control module 760 is responsible for handling (generating / sending / receiving) signalling between the core network function and other nodes, such as the UE 3, the base station 5, and other core network nodes.

[0147] The core network node / function also includes a beam prediction module 770. It will be appreciated that the beam prediction module 770 may be configured to perform control as part of any of the beam prediction module methods described above.

[0148] Modifications and Alternatives 　　As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above examples whilst still benefiting from the inventions therein.

[0149] Whilst some of the examples of AI / ML beam prediction and beam management have been described with reference to beams for transmission of PDSCH, it will be appreciated that these methods can also be used for beam prediction and beam management for beams for transmission of PDCCH.

[0150] Whilst the above examples have been described with reference to an AI / ML model, it will be appreciated that the above described methods are advantageous even when the model is not an AI / ML model. Any other suitable type of model or function may be used to generate inferences (e.g. determinations or predictions), for example for DL Rx beam prediction.

[0151] It will be appreciated, for example, that whilst cellular communication generation (2G, 3G, 4G, 5G, 6G etc.) specific terminology may be used, in the interests of clarity, to refer to specific communication entities, the technical features described for a given entity are not limited to devices of that specific communication generation. The technical features may be implemented in any functionally equivalent communication entity regardless of any differences in the terminology used to refer to them.

[0152] In the above description, the UEs and the base station are described for ease of understanding as having a number of discrete functional components or modules. Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the disclosure, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities.

[0153] In the above detailed examples, a number of software modules were described. As those skilled in the art will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied as a signal over a computer network, or on a recording medium. Further, the functionality performed by part, or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of the base station or the UE in order to update their functionalities.

[0154] Each controller may comprise any suitable form of processing circuitry including (but not limited to), for example: one or more hardware implemented computer processors; microprocessors; central processing units (CPUs); arithmetic logic units (ALUs); input / output (IO) circuits; internal memories / caches (program and / or data); processing registers; communication buses (e.g. control, data and / or address buses); direct memory access (DMA) functions; hardware or software implemented counters, pointers and / or timers; and / or the like. Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0155] The User Equipment (or "UE", "mobile station", "mobile device" or "wireless device") in the present disclosure is an entity connected to a network via a wireless interface.

[0156] It should be noted that the present disclosure is not limited to a dedicated communication device and can be applied to any device having a communication function as explained in the following paragraphs.

[0157] The terms "User Equipment" or "UE" (as the term is used by 3GPP), "mobile station", "mobile device", and "wireless device" are generally intended to be synonymous with one another, and include standalone mobile stations, such as terminals, cell phones, smart phones, tablets, cellular IoT devices, IoT devices, and machinery. It will be appreciated that the terms "mobile station" and "mobile device" also encompass devices that remain stationary for a long period of time.

[0158] A UE may, for example, be an item of equipment for production or manufacture and / or an item of energy related machinery (for example equipment or machinery such as: boilers; engines; turbines; solar panels; wind turbines; hydroelectric generators; thermal power generators; nuclear electricity generators; batteries; nuclear systems and / or associated equipment; heavy electrical machinery; pumps including vacuum pumps; compressors; fans; blowers; oil hydraulic equipment; pneumatic equipment; metal working machinery; manipulators; robots and / or their application systems; tools; molds or dies; rolls; conveying equipment; elevating equipment; materials handling equipment; textile machinery; sewing machines; printing and / or related machinery; paper converting machinery; chemical machinery; mining and / or construction machinery and / or related equipment; machinery and / or implements for agriculture, forestry and / or fisheries; safety and / or environment preservation equipment; tractors; precision bearings; chains; gears; power transmission equipment; lubricating equipment; valves; pipe fittings; and / or application systems for any of the previously mentioned equipment or machinery etc.).

[0159] A UE may, for example, be an item of transport equipment (for example transport equipment such as: rolling stocks; motor vehicles; motorcycles; bicycles; trains; buses; carts; rickshaws; ships and other watercraft; aircraft; rockets; satellites; drones; balloons etc.). A UE may, for example, be an item of information and communication equipment (for example information and communication equipment such as: electronic computer and related equipment; communication and related equipment; electronic components etc.).

[0160] A UE may, for example, be a refrigerating machine, a refrigerating machine applied product, an item of trade and / or service industry equipment, a vending machine, an automatic service machine, an office machine or equipment, a consumer electronic and electronic appliance (for example a consumer electronic appliance such as: audio equipment; video equipment; a loud speaker; a radio; a television; a microwave oven; a rice cooker; a coffee machine; a dishwasher; a washing machine; a dryer; an electronic fan or related appliance; a cleaner etc.).

[0161] A UE may, for example, be an electrical application system or equipment (for example an electrical application system or equipment such as: an x-ray system; a particle accelerator; radio isotope equipment; sonic equipment; electromagnetic application equipment; electronic power application equipment etc.).

[0162] A UE may, for example, be an electronic lamp, a luminaire, a measuring instrument, an analyser, a tester, or a surveying or sensing instrument (for example a surveying or sensing instrument such as: a smoke alarm; a human alarm sensor; a motion sensor; a wireless tag etc.), a watch or clock, a laboratory instrument, optical apparatus, medical equipment and / or system, a weapon, an item of cutlery, a hand tool, or the like.

[0163] A UE may, for example, be a wireless-equipped personal digital assistant or related equipment (such as a wireless card or module designed for attachment to or for insertion into another electronic device (for example a personal computer, electrical measuring machine)).

[0164] A UE may be a device or a part of a system that provides applications, services, and solutions described below, as to "internet of things (IoT)", using a variety of wired and / or wireless communication technologies.

[0165] Internet of Things devices (or "things") may be equipped with appropriate electronics, software, sensors, network connectivity, and / or the like, which enable these devices to collect and exchange data with each other and with other communication devices. IoT devices may comprise automated equipment that follow software instructions stored in an internal memory. IoT devices may operate without requiring human supervision or interaction. IoT devices might also remain stationary and / or inactive for a long period of time. IoT devices may be implemented as a part of a (generally) stationary apparatus. IoT devices may also be embedded in non-stationary apparatus (e.g. vehicles) or attached to animals or persons to be monitored / tracked.

[0166] It will be appreciated that IoT technology can be implemented on any communication devices that can connect to a communications network for sending / receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

[0167] It will be appreciated that IoT devices are sometimes also referred to as Machine-Type Communication (MTC) devices or Machine-to-Machine (M2M) communication devices. It will be appreciated that a UE may support one or more IoT or MTC applications. Some examples of MTC applications are listed in the following table. This list is not exhaustive and is intended to be indicative of some examples of machine type communication applications.

[0168] Applications, services, and solutions may be an MVNO (Mobile Virtual Network Operator) service, an emergency radio communication system, a PBX (Private Branch eXchange) system, a PHS / Digital Cordless Telecommunications system, a POS (Point of sale) system, an advertise calling system, an MBMS (Multimedia Broadcast and Multicast Service), a V2X (Vehicle to Everything) system, a train radio system, a location related service, a Disaster / Emergency Wireless Communication Service, a community service, a video streaming service, a femto cell application service, a VoLTE (Voice over LTE) service, a charging service, a radio on demand service, a roaming service, an activity monitoring service, a telecom carrier / communication NW selection service, a functional restriction service, a PoC (Proof of Concept) service, a personal information management service, an ad-hoc network / DTN (Delay Tolerant Networking) service, etc.

[0169] Further, the above-described UE categories are merely examples of applications of the technical ideas described in the present document. Needless to say, these technical ideas are not limited to the above-described UE and various modifications can be made thereto.

[0170] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0171] While the present disclosure has been particularly shown and described with reference to example embodiments thereof, the present disclosure is not limited to these example embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the claims. And each example embodiment can be appropriately combined with at least one of example embodiments.

[0172] Each of the drawings or figures is merely an example to illustrate one or more example embodiments. Each figure may not be associated with only one particular example embodiment, but may be associated with one or more other example embodiments. As those of ordinary skill in the art will understand, various features or steps described with reference to any one of the figures can be combined with features or steps illustrated in one or more other figures, for example, to produce example embodiments that are not explicitly illustrated or described. Not all of the features or steps illustrated in any one of the figures to describe an example embodiment are necessarily essential, and some features or steps may be omitted. The order of the steps described in any of the figures may be changed as appropriate.

[0173] The whole or part of the example embodiments disclosed above can be described as, but not limited to, the following supplementary notes. 　　(Supplementary Note 1) 　　A method performed by a user equipment (UE), the method comprising: 　　receiving, from an access network node, information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE; and 　　determining, using the information, a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel. 　　(Supplementary Note 2) 　　The method according to supplementary note 1, wherein 　　the determining is performed by predicting a best second downlink beam for receiving, by the UE, the downlink channel, corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel, using the information. 　　(Supplementary Note 3) 　　The method according to supplementary note 2, wherein 　　the predicting is performed by using information indicating mapping between a respective second downlink beam for receiving, by the UE, the downlink channel, and a respective first downlink beam for transmitting, by the access network node, the downlink channel. 　　(Supplementary Note 4) 　　The method according to supplementary note 2 or 3, further comprising: 　　transmitting, to the access network node, capability information indicating a capability of predicting the best second downlink beam for receiving, by the UE, the downlink channel, and wherein 　　the receiving the information indicating the TCI state is performed by the capability information. 　　(Supplementary Note 5) 　　The method according to supplementary note 4, wherein 　　the capability information includes information indicating at least one of: 　　　　a second downlink beam for receiving, by the UE, the downlink channel, 　　　　a first downlink beam for transmitting, by the access network node, the downlink channel, 　　　　both of the second downlink beam for receiving, by the UE, the downlink channel and the first downlink beam for transmitting, by the access network node, the downlink channel, 　　　　a respective supported type of reference signals for predicting, or 　　　　frequencies or frequency bands which are supported by the UE for predicting. 　　(Supplementary Note 6) 　　The method according to supplementary note 1, further comprising: 　　receiving, from the access network node, assistance information for the UE to determine the second downlink beam for receiving, by the UE, the downlink channel corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel, and wherein 　　the determining is performed by using the assistance information. 　　(Supplementary Note 7) 　　The method according to supplementary note 6, wherein 　　the assistance information includes information indicating at least one of: 　　　　another downlink beam whose type is different from the first downlink beam, 　　　　scheduling of transmission of the first downlink beam. 　　(Supplementary Note 8) 　　The method according to supplementary note 7, wherein 　　the another downlink beam includes a standalone demodulation reference signal (DM-RS). 　　(Supplementary Note 9) 　　The method according to any one of supplementary notes 6 to 8, wherein 　　the assistance information is included in at least one of: 　　　　downlink control information which includes the information indicating the TCI state, 　　　　downlink control information which does not include the information indicating TCI state, or 　　　　a Radio Resource Control (RRC) message. 　　(Supplementary Note 10) 　　The method according to any one of supplementary notes 1 to 8, wherein 　　the determining is performed in a case where the UE does not have information for measurement results for the first downlink beam. 　　(Supplementary Note 11) 　　The method according to any one of supplementary notes 1 to 9, wherein 　　each of the first downlink beam and the second downlink beam includes at least one of: 　　　　a channel state information (CSI) reference signal (RS), or 　　　　a synchronization signal / physical broadcast channel block (SSB). 　　(Supplementary Note 12) 　　The method according to any one of supplementary notes 1 to 10, wherein 　　at least one of the first downlink beam or the second downlink beam is for quasi co location type D (QCL-TypeD). 　　(Supplementary Note 13) 　　The method according to any one of supplementary notes 1 to 11, wherein 　　the information indicating the TCI state for the downlink channel includes information indicating whether the first downlink beam is predicted or not. 　　(Supplementary Note 14) 　　The method according to any one of supplementary notes 1 to 11, further comprising: 　　receiving, from the access network node, information indicating whether each of respective first downlink beams for transmitting, by the access network node, the downlink channel is predicted or not. 　　(Supplementary Note 15) 　　The method according to any one of supplementary notes 1 to 11, further comprising: 　　receiving, from the access network node, information indicating at least one first downlink beam for transmitting, by the access network node, the downlink channel is predicted or not as input of training for artificial intelligence / machine learning; and 　　considering other first downlink beam than the at least one first beam as predicted beams. 　　(Supplementary Note 16) 　　The method according to any one of supplementary notes 1 to 11, further comprising: 　　considering the first downlink beam as a predicted beam in a case where: 　　　　the UE has not performed measurements on the first downlink beam, or 　　　　the UE has not received, from the access network node, periodic transmission of the first downlink beam. 　　(Supplementary Note 17) 　　The method according to any one of supplementary notes 1 to 15, wherein 　　the downlink channel includes at least one of: 　　　　a physical downlink control channel (PDCCH), or 　　　　a physical downlink shared channel (PDSCH). 　　(Supplementary Note 18) 　　The method according to any one of supplementary notes 1 to 16, wherein 　　transmitting, to the access network node, information indicating the number of occurrence of at least one of: 　　　　decoding failure of the downlink channel, 　　　　hybrid automatic repeat request (HARQ) negative acknowledgment (NACK) for transmission of the downlink channel, or 　　　　reception of retransmission grants for same transport block of the downlink channel. 　　(Supplementary Note 19) 　　The method according to supplementary note 17, wherein 　　the transmitting the information indicating the number of occurrences is performed in a case where a condition is met. 　　(Supplementary Note 20) 　　The method according to supplementary note 18, wherein 　　the condition includes at least one of: 　　　　occurences for predicted beams are more often than occurences for non-predicted beams, or 　　　　the number of occurences are greater than a threshold. 　　(Supplementary Note 21) 　　The method according to supplementary note 19 or 20, wherein 　　the information indicating the number of occurences includes information indicating the condition which is met. 　　(Supplementary Note 22) 　　A method performed by an access network node, the method comprising: 　　transmitting, to a user equipment (UE), information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE, and wherein 　　the information is used by the UE to determine a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel. 　　(Supplementary Note 23) 　　A user equipment (UE) comprising: 　　means for receiving, from an access network node, information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE; and 　　means for determining, using the information, a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel. 　　(Supplementary Note 24) 　　An access network node comprising: 　　means for transmitting, to a user equipment (UE), information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE, and wherein 　　　　　　the information is used by the UE to determine a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

[0174] This application is based upon and claims the benefit of priority from Great Britain Patent Application No. 2312285.6, filed on August 10, 2023, the disclosure of which is incorporated herein in its entirety by reference.

[0175] 1 COMMUNICATION SYSTEM 3 USER EQUIPMENT 310 TRANSCEIVER CIRCUIT 330 ANTENNA 350 USER INTERFACE 370 CONTROLLER 390 MEMORY 410 OPERATING SYSTEM 430 COMMUNICATIONS CONTROL MODULE 5 (RADIO) ACCESS NETWORK ((R)AN) NODE 5b DISTRIBUTED UNIT 51b TRANSCEIVER CIRCUITRY 53b AIR INTERFACE 57b CONTROLLER 59b MEMORY 61b OPERATING SYSTEM 63b COMMUNICATIONS CONTROL MODULE 65b BEAM PREDICTION MODULE 5c CENTRAL UNIT 51c TRANSCEIVER CIRCUITRY 55c NETWORK INTERFACE 57c CONTROLLER 59c MEMORY 61b OPERATING SYSTEM 63c COMMUNICATIONS CONTROL MODULE 65c BEAM PREDICTION MODULE 7 CORE NETWORK 710 TRANSCEIVER CIRCUIT 720 NETWORK INTERFACE 730 CONTROLLER 740 MEMORY 750 OPERATING SYSTEM 760 COMMUNICATIONS CONTROL MODULE 770 BEAM PREDICTION MODULE 9 CELL 10 CONTROL PLANE FUNCTION (CPF) 10-1 ACCESS AND MOBILITY MANAGEMENT FUNCTION (AMF) 10-2 SESSION MANAGEMENT FUNCTION (SMF) 10-3 UNIFIED DATA MANAGEMENT (UDM) FUNCTION 10-n OTHER FUNCTIONS 11 USER PLANE FUNCTION (UPF) 20 EXTERNAL DATA NETWORK 41 DATA COLLECTION FUNCTION 43 MODEL TRAINING FUNCTION 45 INFERENCE FUNCTION 47 ACTOR 49 MANAGEMENT FUNCTION 51 MODEL STORAGE ENTITY

Claims

1. A method performed by a user equipment (UE), the method comprising: 　　receiving, from an access network node, information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE; and 　　determining, using the information, a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

2. The method according to claim 1, wherein 　　the determining is performed by predicting a best second downlink beam for receiving, by the UE, the downlink channel, corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel, using the information.

3. The method according to claim 2, wherein 　　the predicting is performed by using information indicating mapping between a respective second downlink beam for receiving, by the UE, the downlink channel, and a respective first downlink beam for transmitting, by the access network node, the downlink channel.

4. The method according to claim 2 or 3, further comprising: 　　transmitting, to the access network node, capability information indicating a capability of predicting the best second downlink beam for receiving, by the UE, the downlink channel, and wherein 　　the receiving the information indicating the TCI state is performed by the capability information.

5. The method according to claim 4, wherein 　　the capability information includes information indicating at least one of: 　　　　a second downlink beam for receiving, by the UE, the downlink channel, 　　　　a first downlink beam for transmitting, by the access network node, the downlink channel, 　　　　both of the second downlink beam for receiving, by the UE, the downlink channel and the first downlink beam for transmitting, by the access network node, the downlink channel, 　　　　a respective supported type of reference signals for predicting, or 　　　　frequencies or frequency bands which are supported by the UE for predicting.

6. The method according to claim 1, further comprising: 　　receiving, from the access network node, assistance information for the UE to determine the second downlink beam for receiving, by the UE, the downlink channel corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel, and wherein 　　the determining is performed by using the assistance information.

7. The method according to claim 6, wherein 　　the assistance information includes information indicating at least one of: 　　　　another downlink beam whose type is different from the first downlink beam, 　　　　scheduling of transmission of the first downlink beam.

8. The method according to claim 7, wherein 　　the another downlink beam includes a standalone demodulation reference signal (DM-RS).

9. The method according to any one of claims 6 to 8, wherein 　　the assistance information is included in at least one of: 　　　　downlink control information which includes the information indicating the TCI state, 　　　　downlink control information which does not include the information indicating TCI state, or 　　　　a Radio Resource Control (RRC) message.

10. The method according to any one of claims 1 to 9, wherein 　　the determining is performed in a case where the UE does not have information for measurement results for the first downlink beam.

11. The method according to any one of claims 1 to 10, wherein 　　each of the first downlink beam and the second downlink beam includes at least one of: 　　　　a channel state information (CSI) reference signal (RS), or 　　　　a synchronization signal / physical broadcast channel block (SSB).

12. The method according to any one of claims 1 to 11, wherein 　　at least one of the first downlink beam or the second downlink beam is for quasi co location type D (QCL-TypeD).

13. The method according to any one of claims 1 to 12, wherein 　　the information indicating the TCI state for the downlink channel includes information indicating whether the first downlink beam is predicted or not.

14. The method according to any one of claims 1 to 12, further comprising: 　　receiving, from the access network node, information indicating whether each of respective first downlink beams for transmitting, by the access network node, the downlink channel is predicted or not.

15. The method according to any one of claims 1 to 12, further comprising: 　　receiving, from the access network node, information indicating at least one first downlink beam for transmitting, by the access network node, the downlink channel is predicted or not as input of training for artificial intelligence / machine learning; and 　　considering other first downlink beam than the at least one first beam as predicted beams.

16. The method according to any one of claims 1 to 12, further comprising: 　　considering the first downlink beam as a predicted beam in a case where: 　　　　the UE has not performed measurements on the first downlink beam, or 　　　　the UE has not received, from the access network node, periodic transmission of the first downlink beam.

17. The method according to any one of claims 1 to 16, wherein 　　the downlink channel includes at least one of: 　　　　a physical downlink control channel (PDCCH), or 　　　　a physical downlink shared channel (PDSCH).

18. The method according to any one of claims 1 to 17, wherein 　　transmitting, to the access network node, information indicating the number of occurrence of at least one of: 　　　　decoding failure of the downlink channel, 　　　　hybrid automatic repeat request (HARQ) negative acknowledgment (NACK) for transmission of the downlink channel, or 　　　　reception of retransmission grants for same transport block of the downlink channel.

19. The method according to claim 18, wherein 　　the transmitting the information indicating the number of occurrences is performed in a case where a condition is met.

20. The method according to claim 19, wherein 　　the condition includes at least one of: 　　　　occurences for predicted beams are more often than occurences for non-predicted beams, or 　　　　the number of occurences are greater than a threshold.

21. The method according to claim 19 or 20, wherein 　　the information indicating the number of occurences includes information indicating the condition which is met.

22. A method performed by an access network node, the method comprising: 　　transmitting, to a user equipment (UE), information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE, and wherein 　　the information is used by the UE to determine a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

23. A user equipment (UE) comprising: 　　means for receiving, from an access network node, information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE; and 　　means for determining, using the information, a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

24. An access network node comprising: 　　means for transmitting, to a user equipment (UE), information indicating a transmission configuration indication (TCI) state for a downlink channel, corresponding to a first downlink beam for transmitting, by the access network node, the downlink channel, the first downlink beam being not transmitted to the UE, and wherein 　　the information is used by the UE to determine a second downlink beam for receiving, by the UE, the downlink channel, the second downlink beam corresponding to the first downlink beam for transmitting, by the access network node, the downlink channel.

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