Switching transmission configuration indication states

Abstract

Certain examples of the present disclosure relate to an apparatus (110, 10) comprising: means (11) for receiving, from a network node (120), information indicating at least one target Transmission Configuration Indication, TCI, state (202), wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS (203); means (11) for determining whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus (110) is synchronised; and means (11) for performing at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

Description

[0001] DESCRIPTION

[0002] SWITCHING TRANSMISSION CONFIGURATION INDICATION STATES

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to switching Transmission Configuration Indication, TCI, states. Various examples provide an apparatus, a method, a system, and a computer program for use in switching TCI states. Some examples, though without prejudice to the foregoing, relate to determining whether or not to perform a synchronisation process in a TCI switching procedure, such as an TCI activation procedure.

[0005] BACKGROUND

[0006] The conventional TCI switching procedure is not always optimal.

[0007] In some circumstances it can be desirable to improve TCI switching. In some circumstances it can be desirable to reduce delays in performing a TCI switching procedure. In some circumstances it can be desirable to avoid a need to perform a synchronisation process in a TCI switching procedure and thereby reduce a TCI switching delay.

[0008] The listing or discussion of any prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge. One or more aspects / examples of the present disclosure may or may not address one or more of the background issues.

[0009] BRIEF SUMMARY

[0010] According to various, but not necessarily all, examples of the disclosure there are provided examples as claimed in the appended claims. Any examples and features described in this specification that do not fall underthe scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0011] According to at least some examples of the disclosure there is provided an apparatus comprising: means for receiving, from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; means for determining whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and means for performing at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

[0012] According to various, but not necessarily all, examples of the disclosure there is provided a method comprising: receiving, at an apparatus from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; determining, at the apparatus, whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and performing, at the apparatus, at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

[0013] According to various, but not necessarily all, examples of the disclosure there is provided a chipset comprising processing circuitry configured to perform the above-mentioned method.

[0014] According to various, but not necessarily all, examples of the disclosure there is provided a module, circuitry, device and / or system comprising means for performing the above- mentioned method.

[0015] According to various, but not necessarily all, examples of the disclosure there is provided a computer program comprising instructions, which when executed by an apparatus, cause the apparatus to perform: receiving, from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; determining whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and performing at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

[0016] According to various, but not necessarily all, examples of the disclosure there is provided an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; determine whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and perform at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

[0017] According to various, but not necessarily all, examples of the disclosure there is provided a non-transitory computer readable medium encoded with instructions that, when executed by at least one processor, causes at least the following to be performed: receive, at an apparatus from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; determine, at the apparatus, whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and perform, at the apparatus, at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

[0018] The following portion of this 'Brief Summary’ section describes various features that can be features of any of the examples described in the foregoing portion of the 'Brief Summary’ section mutatis mutandis. The description of a function should additionally be considered to also disclose any means suitable for performing that function, or any instructions stored in at least one memory that, when executed by at least one processor, cause an apparatus to perform that function.

[0019] In some but not necessarily all examples, at least one TCI state, which is activated at the apparatus, has at least one QCL relation with the at least one second RS.

[0020] In some but not necessarily all examples, the information indicating the at least one target TCI state comprises at least one of the following: an indication of at least one TCI state that the apparatus is to switch to; or an indication of at least one TCI state that the apparatus is to activate.

[0021] In some but not necessarily all examples, In some but not necessarily all examples, the information indicating at least one target TCI state is received via at least one of the following: a Medium Access Control, MAC, layer signal; a MAC Control Element, CE, command for TCI indication for Physical Downlink Control Channel, PDCCH; or a MAC-CE command for TCI state activation for Physical Downlink Shared Channel, PDSCH.

[0022] In some but not necessarily all examples, the at least one first RS is a QCL source RS of the at least one target TCI state.

[0023] In some but not necessarily all examples, the at least one first and second RSs comprise at least one of the following: at least one synchronization signal; at least one Synchronization Signal Block, SSB; at least one a Channel-State Information Reference Signal, CSI-RS; at least one Tracking Reference Signal, TRS; or at least one Aperiodic Reference Signal.

[0024] In some but not necessarily all examples, determining whether the at least one condition has been met comprises determining whether: the at least one first RS is a member of a group of a plurality of RSs, and the at least one second RS is a member of the same group.

[0025] In some but not necessarily all examples, the group to which the at least one first RS is a member of is identified based at least in part on a time and / or frequency resource through which the at least one first RS is transmitted.

[0026] In some but not necessarily all examples, the apparatus further comprises means for receiving, from the network node, information indicating the group.

[0027] In some but not necessarily all examples, determining whether the at least one condition has been met comprises determining whether there is an association between the at least one first RS and the at least one second RS, and wherein determining whether there is an association comprises determining whether at least one criterion is satisfied.

[0028] In some but not necessarily all examples, the at least one criterion is pre-determined.

[0029] In some but not necessarily all examples, the at least one criterion is that the at least one first RS and the at least second one RS are received within a time interval. In some but not necessarily all examples, the at least one criterion is that the at least one first RS and the at least one second RS are received from the same Transmission Reception Point, TRP, of the network node.

[0030] In some but not necessarily all examples, the apparatus comprises means for receiving information indicative of at least one spatial position associated with the at least one first RS, and at least one spatial position associated with the at least one second RS; and wherein the at least one criterion is that a difference between the at least one spatial position of the at least one first RS and the at least one spatial position of the at least one second RS is within at least one threshold value.

[0031] In some but not necessarily all examples, the at least one synchronisation process is at least one SSB synchronization of a TCI switching procedure.

[0032] In some but not necessarily all examples, in response to determining that the at least one condition is fulfilled, a determination is made not to perform the synchronisation process.

[0033] In some but not necessarily all examples, the apparatus further comprises means for transmitting, to the network node, information indicating that the apparatus is capable of at least one of the following: receiving the information indicating the group; and determining whether the at least one first RS and the at least one second RS are members of the group.

[0034] In some but not necessarily all examples, the apparatus further comprises means for transmitting, to the network node, information indicating that the apparatus is capable of: determining whether there is the association between the at least one first RS and the at least one second RS.

[0035] In some but not necessarily all examples, there is provided a User Equipment, UE, that comprises the apparatus described above.

[0036] According to at least some examples of the disclosure there is provided an apparatus comprising: means for receiving, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and means for transmitting, to the UE, information indicating the group based at least in part on the received capability information.

[0037] According to various, but not necessarily all, examples of the disclosure there is provided a method comprising: receiving, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and transmitting, to the UE, information indicating the group based at least in part on the received capability information.

[0038] According to various, but not necessarily all, examples of the disclosure there is provided a chipset comprising processing circuitry configured to perform the above-mentioned method.

[0039] According to various, but not necessarily all, examples of the disclosure there is provided a module, circuitry, device and / or system comprising means for performing the above- mentioned method.

[0040] According to various, but not necessarily all, examples of the disclosure there is provided a computer program comprising instructions, which when executed by an apparatus, cause the apparatus to perform: receiving, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and transmitting, to the UE, information indicating the group based at least in part on the received capability information.

[0041] According to various, but not necessarily all, examples of the disclosure there is provided an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and transmit, to the UE, information indicating the group based at least in part on the received capability information.

[0042] According to various, but not necessarily all, examples of the disclosure there is provided a non-transitory computer readable medium encoded with instructions that, when executed by at least one processor, causes at least the following to be performed: receiving, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and transmitting, to the UE, information indicating the group based at least in part on the received capability information.

[0043] While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all of the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all of the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Some examples will now be described with reference to the accompanying drawings in which:

[0046] FIG. 1 A schematically illustrates an example of a radio telecommunications network;

[0047] FIG. 1 B schematically illustrates QCL and a TCI chain; FIG. 2 schematically illustrates an example of MAC-CE activation and DCI indication of TCI states for PDSCH;

[0048] FIG. 3 schematically illustrates a further example of MAC-CE activation and DCI indication of TCI states for PDSCH with a TCI state switching delay;

[0049] FIG. 4 schematically illustrates an example of MAC-CE indication of TCI states for PDCCH; FIG. 5 schematically illustrates an example of a method in accordance with the subject matter described herein;

[0050] FIG. 6 schematically illustrates a further example of a method in accordance with the subject matter described herein;

[0051] FIG. 7 schematically illustrates an example of SSB grouping in accordance with the subject matter described herein;

[0052] FIG. 8 schematically illustrates a further example of SSB grouping in accordance with the subject matter described herein;

[0053] FIG. 9 schematically illustrates a yet further example of SSB grouping in accordance with the subject matter described herein;

[0054] FIG. 10 schematically illustrates a yet further example of SSB grouping in accordance with the subject matter described herein;

[0055] FIG. 11 schematically illustrates a yet further example of SSB grouping in accordance with the subject matter described herein;

[0056] FIG. 12 schematically illustrates a yet further example of a method in accordance with the subject matter described herein;

[0057] FIG. 13 schematically illustrates an example of an apparatus in accordance with the subject matter described herein; and

[0058] Fig. 14 schematically illustrates a computer program in accordance with the subject matter described herein.

[0059] The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

[0060] ABBREVIATIONS / DEFINITIONS

[0061] Az Azimuth CORESET Control Resource Set CSI-RS Channel-State Information Reference Signal

[0062] DCI Downlink Control Information

[0063] DL Downlink

[0064] DMRS Demodulation Reference Signal

[0065] El Elevation

[0066] FR2 Frequency Range 2

[0067] MAC Medium Access Control MAC-CE Medium Access Control - Control Element

[0068] MIMO Multiple Input Multiple Output

[0069] NW Network

[0070] PCID Primary Cell ID

[0071] PDCCH Physical Downlink Control Channel

[0072] PDSCH Physical Downlink Shared Channel

[0073] PUCCH Physical Uplink Control Channel

[0074] PUSCH Physical Uplink Shared Channel

[0075] QCL Quasi Co-Location

[0076] RRC Radio Resource Control

[0077] RRM Radio Resource Management

[0078] RS Reference Signal

[0079] RX Receive

[0080] SFN Single Frequency Network

[0081] SSB Synchronization Signal Block

[0082] TCI Transmission Configuration Indication

[0083] TRP Transmission-Reception Point

[0084] UE User Equipment

[0085] Wl Work Item

[0086] DETAILED DESCRIPTION

[0087] FIG. 1 schematically illustrates an example of a network 100 suitable for use with examples of the present disclosure. The network (also referred to as NW) comprises a plurality of network nodes including: terminal nodes 110 (also referred to as User Equipment, UE), access nodes 120 (also referred to as Radio Access Network, RAN, node, or Base Station, BS), and one or more core network nodes 130. The terminal nodes 110 and access nodes 120 communicate with each other. The one or more core network nodes 130 may, in some but not necessarily all examples, communicate with each other. The one or more access nodes 120 may, in some but not necessarily all examples, communicate with each other.

[0088] The network 100 is, in this example, a radio telecommunications network, i.e. a RAN, in which at least some of the terminal nodes 1 10 and access nodes 120 communicate with each other using transmission / reception of radio waves.

[0089] The network / RAN 100 may be a cellular network comprising a plurality of cells 122 each served by an access node 120. The access nodes 120 comprise cellular radio transceivers. The terminal nodes 110 comprise cellular radio transceivers.

[0090] In the particular example illustrated and discussed below, the network 100 is a New Radio, NR, network of the Third Generation Partnership Project, 3GPP, and its fifth generation, 5G, technology. In other examples, the network 100 may be a network beyond 5G, for example a next generation (i.e. sixth generation, 6G) Radio Network that is currently under development (i.e. an evolution of the NR network and its 5G technology). The interfaces between the terminal nodes 110 and the access nodes 120 are radio interfaces 124 (e.g., Uu interfaces). The interfaces between the access nodes 120 and one or more core nodes 130 are backhaul interfaces 128 (e.g., S1 and / or Next Generation, NG, interfaces).

[0091] Depending on the exact deployment scenario, the access nodes 120 may be RAN nodes such as NG-RAN nodes. NG-RAN nodes may be gNodeBs, gNBs, that provide NG user plane and control plane protocol terminations towards the UE. The gNBs connected by means of NG interfaces to a 5G Core (5GC), more specifically to an Access and Mobility Management Function, AMF, by means of an NG Control Plane, NG-C, interface and to a User Plane Function, UPF, by means of an NG User Plane, NG-U, interface. The access nodes 120 may be interconnected with each other by means of Xn interfaces 126.

[0092] The cellular network 100 may be configured to operate in licensed frequency bands, or unlicensed frequency bands (not least such as: unlicensed bands that rely upon a transmitting device to sense the radio resources / medium before commencing transmission, such as via a Listen Before Talk, LBT, procedure; and a 60GHz unlicensed band where beamforming may be required in order to achieve required coverage).

[0093] The access nodes 120 may be deployed in an NG standalone operation / scenario. The access nodes 120 may be deployed in a NG non-standalone operation / scenario. The access nodes 120 may be deployed in a Carrier Aggregation, CA, operation / scenario. The access nodes 120 may be deployed in a Dual Connectivity, DC, operation / scenario, i.e., Multi Radio Access Technology - Dual Connectivity, MR-DC, or NR-DC. The access nodes 120 may be deployed in a Multi Connectivity, MC, operation / scenario.

[0094] In such non-standalone / dual connectivity deployments, the access nodes 120 may be interconnected to each other by means of X2 or Xn interfaces, and connected to an Evolved Packet Core, EPC, by means of an S1 interface or to the 5GC by means of a NG interface.

[0095] The access nodes 120 are network elements in the network responsible for radio transmission and reception in one or more cells 122 to or from the terminal nodes 110. The access nodes 120 are the network termination of a radio link. Each access node may host one or more Transmission Reception Points, TRPs.

[0096] An access node 120 may be implemented as a single network equipment, or have a split architecture that is disaggregated / distributed over two or more RAN nodes, such as a Central Unit, CU, a Distributed Unit, DU, a Remote Radio Head-end, RRH, using different functional-split architectures and different interfaces.

[0097] The terminal nodes 110 are network elements in the network that terminate the user side of the radio link. They are devices allowing access to network services. Terminal node 110 functionalities may be performed also by Mobile Termination, MT, part of an Integrated Access and Backhaul, IAB, node. The terminal nodes 110 may be referred to as User Equipment, UE, mobile terminals or mobile stations.

[0098] The term 'User Equipment’ may be used to designate mobile equipment comprising means, such as a smart card, for authentication / encryption etc. such as a Subscriber Identity Module, SIM. A SIM / SIM card can be a memory chip, a module, or a Universal Subscriber Identity Module (USIM). In some examples, the term 'User Equipment’ can be used to designate a location / position tag, a hyper / smart, a hyper / smart sensor, or a mobile equipment comprising circuitry embedded as part of the user equipment for authentication / encryption such as a software SIM.

[0099] In the following description, a terminal node may be referred to simply as UE 110. In the following description, an access node, a Radio Access Network, RAN, node, a gNB or a TRP may be referred to simply as a network node 120; and the network itself may be referred to simply as NW.

[0100] There now follows a brief discussion of single Transmission Configuration Indicator, TCI, and dual TCI.

[0101] A TCI state can be used to establish a Quasi Co-Iocation, QCL, relation (also known as a QCL connection) between a source RS and a target RS. The source and target RSs may be said to be Quasi Co-located, i.e. QCLed. The source RS of a TCI state may be referred to as a QCL source RS. The TCI state may be referred to as having or defining a QCL relation with the source (and target) RS.

[0102] A TCI state will have parameters which define the QCL relation between the reference signals. This relation is defined via RRC signaling. The Information Element, IE, TCI-State associates one of two DL reference signals with a corresponding QCL type.

[0103] There are four different types of QCL defined in NR

[0104] QCL types A: Doppler shift, Doppler spread, average delay, delay spread

[0105] QCL types B: Doppler shift, Doppler spread

[0106] QCL types C: average delay, Doppler shift

[0107] QCL types D: Spatial Rx

[0108] The TCI state indicates the QCL relations between the various Reference signals as configured in the network.

[0109] FIG. 1 B schematically illustrates QCL and a TCI chain. Various of the CSI-RSs shown in FIG. 1 B have a QCL (e.g. type C or C and D) relation with an SSB. A TCI state, sent by the network to a UE, would indicate a QCL relation between the RSs. The UE, on reception of the TCI state, would thereby know, for example, that if a QCL relation between two RSs is a QCL type C, then the UE can assume the same channel properties (e.g. average delay, Doppler shift) for both the RSs. The existing Rel-15 NR Frequency Range 2, FR2, minimum UE requirements are defined with an assumption that UE is only required to receive with a single antenna panel at a time and is capable of performing downlink, DL, reception using a single received, RX, beam / chain. Furthermore, UE performance requirements are limited for DL Multiple Input Multiple Output, MIMO, rank 1 and 2 in FR2. In FR2, 4-layer MIMO reception (e.g. for high-rate MIMO in FR2, as well as for FR2 High Speed Train, HST, scenarios) requires beam reception from at least two directions. Although this is supported by the MIMO features since Rel-15, no UE performance requirements have yet been specified.

[0110] Several enhancements to enable efficient and robust DL multi-TRP / panel operation were introduced in the Rel-16 NR enhanced MIMO, eMIMO, Working Item, Wl. However, no Radio Frequency, RF, Radio Resource Management, RRM, or performance requirements were defined in Rel-16 and Rel-17 for FR2 UEs with simultaneousReceptionDiffTypeD-r16 capability.

[0111] Enhanced NR FR2 UEs with multi-beam simultaneous reception and multiple RX chains can provide a meaningful performance improvement in FR2 improving both demodulation performance (4-layer DL MIMO), RRM performance and improve RF spherical coverage. In Rel-18 a Work Item, Wl, NR_FR2_multiRX_DL is being developed, which aims to introduce the requirements for UEs capable of multi-beam / chain simultaneous DL reception on a single component carrier to achieve improved RF, RRM and UE demodulation performance.

[0112] Different implementation scenarios could be considered at the UE. Single-TCI reception on different beams has been supported by RAN1 specifications since Rel-15 via the Type I codebook, which could be achieved at the UE with either a single panel or multiple panels. Alternatively, dual TCI operation can be combined with the Rel-17 mTRP framework - even if the base station is actually deployed as a single TRP. This Wl therefore provides the requirements for both single and dual TCI assumptions to specify requirements for reception of 4-layer downlink MIMO with simultaneous reception at the UE from two different directions.

[0113] There now follows a brief discussion of Multiple Transmit / Receive Points, M-TRPs.

[0114] A NR cell may comprise of one or multiple TRPs. TRPs of the same cell have a common Synchronization Signal, SS / Physical Broadcast Channel, PBCH, block (i.e. SS / PBCH block referred to as Synchronization Signal Block, SSB) which is cell specific. In multi-TRP operation, a serving cell can schedule a UE from two TRPs, which may provide better coverage, reliability and / or data rates for: Physical Downlink Shared Channel, PDSCH; Physical Downlink Control Channel, PDCCH; Physical Uplink Shared Channel, PUSCH; and Physical Uplink Control Channel, PUCCH.

[0115] There are two different operation modes to schedule multi-TRP PDSCH transmissions: single- Downlink Control Information, DCI and multi-DCI. For both modes, control of uplink and downlink operation can be done by physical layer and Medium Access Control, MAC, layer, within the configuration provided by the Radio Resource Control, RRC, layer. In single- DCI mode, only one TRP is responsible for the transmission of the control channel (PDCCH) to the UE. As a result, the UE is scheduled by one PDCCH containing a DCI for both TRPs. On the other hand, in multi-DCI mode, two TRPs are responsible for the transmission of control channel information to the UE. As a result, the UE is scheduled by independent DCIs from each TRP.

[0116] Additionally, there are two different operation modes for single DCI multi-TRP PDCCH: PDCCH repetition and Single Frequency Network, SFN, based PDCCH transmission. In both modes, the UE can receive two PDCCH transmissions, one from each TRP, carrying the same DCI.

[0117] • In PDCCH repetition mode: the network will transmit, and the UE may receive, the two PDCCH transmissions carrying the same DCI from two linked search spaces each associated with a different Control Resource Set, CORESET.

[0118] • In SFN based PDCCH transmission mode: the network transmits, and the UE may receive, the two PDCCH transmissions carrying the same DCI from a single search space / CORESET using different TCI states.

[0119] There now follows a brief discussion of Beam management.

[0120] 3GPP defined 5G NR FR2 bands which have huge bandwidths and which can cater to 5G NR use cases requiring higher data rates. However, these bands are also subject to challenging propagating conditions, not least such as: high path loss, absorption from the environment and penetration losses. To overcome these, beam management procedures have been defined in 3GPP.

[0121] Beam Management is a set of procedures to assist UE to set its receive, Rx, and transmit, Tx, beams for downlink and uplink transmissions respectively. NR supports a hierarchical beam based approach with the SSB beam being the root beam.

[0122] Level 1 : SSB "beams” may comprise, for example:

[0123] SSB #l,

[0124] SSB #m, and SSB #n.

[0125] Level 2-n: Channel-State Information Reference Signal, CSI-RS, "beams” (each associated with a respective root SSB) may comprise for example:

[0126] CSI-RS #0 (associated with SSB #n),

[0127] CSI-RS #1 (associated with SSB #n),

[0128] CSI-RS #2 (associated with SSB #n), and

[0129] CSI-RS #3 (associated with SSB #n) There now follows a brief discussion of Quasi Co-Iocation, QCL, framework used for beam indication. gNB provided beam indication information is used to configure UE with information regarding which Tx beam is to be used for DL (and the UE can select proper Rx beam) and which Tx beam is to be used for UL - so that UE’s Tx beam is "directed” towards the RX beam used at the gNB.

[0130] The UE can be configured with a list of up to M TCI-State configurations within a higher layer parameter PDSCH Config to decode PDSCH according to a detected PDCCH with DCI intended for the UE and a given serving cell, where M depends on the UE capability maxNumberConfiguredTCIstatesPerCC.

[0131] Each TCI-State may contains parameters for configuring a QCL relationship between one or two DL Reference Signals, RSs, (such RSs which have a QCL relation with a TCI state may be referred to as QCL source RS) and: the Demodulation Reference Signal, DMRS, ports of the PDSCH, the DMRS port of PDCCH or the CSI-RS port(s) of a CSI-RS resource. The QCL relationship is configured by a higher layer parameter qcl-Type1 for a first DL RS, and qcl- Type2 for a second DL RS (if configured). In instances where there are two DL RSs, the QCL types are not to be the same, regardless of whether the references are to the same DL RS or different DL RSs.

[0132] The QCL types corresponding to each DL RS are given by a higher layer parameter qcl-Type in QCL-Info and may take one of the following values: o QCL types A: Doppler shift, Doppler spread, average delay, delay spread o QCL types B: Doppler shift, Doppler spread o QCL types C: average delay, Doppler shift o QCL types D: Spatial Rx

[0133] There now follows a brief discussion of a TCI framework.

[0134] The main tool for beam indication for DL is a TCI framework. A UE can be configured with up to 128 TCI states. A gNB configures the UE, via RRC signaling, with TCI states where each TCI state may have one or two source RSs that provide QCL parameters for the target RS (e.g. a Demodulation Reference Signal, DMRS, of PDCCH or PDSCH). Only one RS may provide QCL type D per TCI state. As mentioned above, such source RSs having a QCL relation to a TCI state may be referred to as a source QCL RS. A DL TCI chain consists of an SSB, and one or more CSI-RS resources, and the TCI state of each RS includes another RS in the same TCI chain, where an SSB can be associated with a serving cell Primary Cell ID, PCID, or associated with a PCID different from serving cell PCID.

[0135] DMRS of PDCCH or PDSCH is QCLed with the RS in its active TCI state and any other RS that is QCLed, based on the criteria for DL TCI chain, with the RS in an active TCI state. There now follows a brief discussion of TCI state switching delay requirements.

[0136] TCI state switching delay requirements have been defined in RAN 4 for a single TRP and the same is expected to be used as a baseline while defining RAN 4 requirements for dual TCI state switching in the multi-TRP context.

[0137] Current TCI state switching delay requirements for MAC-CE based TCI switch for PDCCH, DCI based TCI state switch delay and the active TCI state list update delay are defined, e.g. in 3GPP TS 38.133, V18.3.0 (2023-09), sections 8.10.2 - 8.10.6.

[0138] TCI state switch requirements for FR2 have currently only been defined for Rel-15 Single TRP and enhanced in Rel-16 / 17 to include requirement for unified TCI state framework. So far there are no RAN4 requirements for TCI state switch in case of multi-TRP. In 3GPP Rel- 18, TCI state switch requirements will be defined for Multi-Rx chain UEs in the Multi-TRP scenario.

[0139] In a multi-TRP scenario, the UE can be configured to measure on a set of beams from different TRPs and report Layer 1 Reference Signal Received Power, L1 RSRP, levels back to the network in the form of a Channel State Information, CSI, report. Based on such UE feedback, the network sends a Medium Access Control - Control Element, MAC CE, indicating a TCI state for PDCCH (this is discussed below and shown with respect to FIG. 4).

[0140] In case of PDSCH, a maximum of 8 TCI states can be activated for the UE. These are indicated by the network to the UE via MAC CE signaling (this is discussed below and shown with respect to FIGs 2 and 3) and would be a part of a code point table such as the following example TCI code point table:

[0141] After an update of an active TCI list, the network may then send a DCI indicating which of the TCI states of the updated active TCI list are to be used for reception of PDSCH.

[0142] The requirements for TCI state active list update delay are defined in RAN4 RRM requirements in 3GPP TS 38.133 for a single TRP. In the existing RRM requirements defined for a single TRP, after the UE has received the MAC-CE (either for TCI state indication for PDCCH or activation of TCI states for PDSCH), the UE first needs to synchronize with the SSB after THARQ+3ms. It is only after such synchronization with the SSB is complete that, depending on whether the MAC-CE received is for indicating the TCI state for PDCCH or TCI state activation for PDSCH, the UE is considered to be capable of using the target TCI state.

[0143] FIG. 2 schematically illustrates a further example of MAC-CE activation and DCI indication of TCI states for PDSCH with a TCI state switching delay.

[0144] In the example of FIG. 2, it is assumed that the existing RAN 4 procedures currently defined for a single TRP TCI state switching would be used as a baseline for Multi-TRP scenarios.

[0145] In the example of FIG. 2, a multi-Rx UE receives a MAC-CE with activation command for TCI states for PDSCH at a time tO. The UE would be able to switch the TCI state upon reception of a PDCCH DCI with a TCI indication, and the UE would be able to receive PDSCH at time instance t1.

[0146] FIG. 2, considers the case where the active TCI state list is updated, and wherein one codepoint, containing target TCI states TCI #1 and TCI#2 from 2 TRPs, is activated. In this example, SSB#1 is a first SSB transmission associated with target TCI #1 after the MAC CE command is decoded by the UE. Similarly, SSB#2 is a first SSB transmission associated with target TCI#2 after the MAC CE command is decoded by the UE.

[0147] The two SSBs are the source RSs, or QCL sources, of the two target TCI states. In this regard SSB#1 serves as a source RS source that is in a QCL relation indicated in TCI#1, and SSB#2 serves as a source RS in a QCL relation indicated in TCI#2. In other words, SSB#1 is in a QCL relation / connection with TCI#1 , and can be considered to be a QCL source for TCI #1 . Likewise, SSB#2 is in a QCL relation / connection with TCI#2, and can be considered to be a QCL source for TCI#2.

[0148] The codepoint containing targets TCI states TCI #1 and TCI#2 is only activated after SSB#1 and SSB#2 is received by the UE because the UE needs to detect the DL frame boundary related to TCI #1 and TCI#2 (in this regard, the UE would need to synchronize to the QCL sources SSB#1 and SSB#2).

[0149] One challenge with this approach is that depending on when the MAC CE command is sent to the UE, there could be a further delay of up to one SSB period between THARQ+3 ms and the first SSB transmission. Considering that THARQ is k1 *slot length, where K1 is indicated in PDSCH-to-HARQ-timing-indicator, which can be 0 to 15 slots, a MAC CE activation delay could theoretically take about 4 ms if the first SSB were sent immediately after THARQ+3ms (as illustrated in the scenario of FIG. 2). However, if one were to consider that SSB periodicity can be up to 160 ms, this delay in activation time could be extended to up to 164 ms.

[0150] In current 3GPP specifications, when the UE receives the MAC CE command for activating the TCI states for PDSCH or for indication of TCI state for PDCCH, the UE may need time to synchronize with the first SSB after Tharq + 3ms. Hence, depending on when the indication is received, a SSB burst may just have been transmitted, during for example the Tharq + 3ms interval, in which case the UE will need to wait for the next SSB which will be around 20ms later ( assuming SSB periodicity is 20ms). For higher periodicity like 160 ms, the delay / wait time will be higher.

[0151] FIG. 3 schematically illustrates a further example of MAC-CE activation and DCI indication of TCI states for PDSCH. FIG. 3 illustrates the above-mentioned issues that can lead to a TCI state switching delay.

[0152] Unlike in FIG. 2 wherein the SSBs were received just after THARQ+3 ms, in the scenario illustrated in FIG. 3 the SSBs are received just before THARQ+3 ms. Hence the UE has to wait for the next SSB transmission - which happens only 160 ms after that time.

[0153] The TCI state switching delay could be even worse in scenarios wherein the first SSBs that the UE has to synchronize with in a dual TCI activation scenario are overlapping, and the UE cannot synchronize with both simultaneously. In this case, the UE would need to wait for another SSB / SSB based Measurement Timing Configuration, SMTC, periodicity to be able to synchronize with both SSBs. This could, in a worst case, lead to another additional delay of 160 ms, leading to a total delay of 324 ms.

[0154] FIG. 4 schematically illustrates an example of MAC-CE indication of TCI states for PDCCH. It is to be appreciated that TCI switching delays, similar to those discussed above with respect to FIGs 2 and 3, could equally well arise with regards to TCI switching involving the procedure of FIG. 4 mutatis mutandis.

[0155] Whilst the TCI switching delay issues have been described and discussed above with regards to dual TCI operation, it is to be appreciated that TCI switching delay issues could also arise for single TCI operation.

[0156] Various examples of the present disclosure seek to reduce TCI active list update delay and TCI switching delays by avoiding / reducing the need for a UE to synchronize to an SSB.

[0157] As will be discussed in further detail below, various examples of the present disclosure seek to provide a method for fast TCI state activation, wherein QCL relations with previously activated TCI states are considered for enabling faster activation of target TCI state(s) when a MAC CE indication of a TCI state(s) for PDCCH - as well as a MAC-CE activation of target TCI state(s) for PDSCH - is sent by a gNB. In various examples, it is proposed that the UE may synchronize via alternate means when it already has activated TCI states which are QCL-ed with new target TCI state(s).

[0158] FIG. 5 schematically illustrates a method 200 according to an example of the subject matter described herein. The method may be used in a TCI switching procedure, such as for example a TCI switching procedure involving a MAC-CE command for TCI indication for PDCCH, or a TCI switching procedure involving a MAC-CE command for TCI state activation for PDSCH.

[0159] FIG. 5 can be considered to illustrate a plurality of methods, in the sense that FIG. 5 can be considered to illustrate one or more actions performed by / at a plurality of actors / entities (e.g. apparatuses such as a UE 110 and a network node 120). FIG. 5 can therefore be considered to illustrate a plurality of individual methods performed by each respective individual actor / entity of the plurality of the actors / entities.

[0160] The component blocks of FIG. 5 are functional, and the functions described can be performed by a single physical entity, such as an apparatus as described with reference to FIG. 13, wherein the apparatus may be embodied either as a UE 110 or network node 120. The functions described can also be implemented by a computer program, such as is described with reference to FIG. 14. The blocks illustrated in FIG. 5 can therefore represent actions in a method, functionality performed by an apparatus, and / or sections of instructions / code in a computer program.

[0161] In block 201 , a UE receives, from the NW, information indicating a target Transmission Configuration Indication, TCI, state 202, wherein the target TCI state has Quasi Co-Location, QCL, relation with a first Reference Signal, RS, 203. In this regard, the first RS may serve as a QCL source RS for the target TCI state.

[0162] The information indicating the target TCI state may be: an indication of a TCI state that the UE is to switch to; or an indication of a TCI state that the UE is to activate. The information may be: a MAC layer signal; a MAC-CE command for TCI indication for PDCCH, or a MAC-CE command for TCI state activation for PDSCH.

[0163] In block 204, the UE determines whether a condition has been met, wherein the condition is based at least in part on: the first RS, and a second RS that the UE is currently synchronised with.

[0164] The second RS that the UE is synchronised with may be an RS with which a TCI state, that is currently activated at the UE, has a QCL relation. In this regard, the second RS may be a QCL source for a TCI state that is already currently activated at the UE.

[0165] Each of first and / or second RS may be transmitted by the NW (e.g. a gNB 120) and received by the UE. Each of first and / or second RS may be at least one of the following: a synchronization signal; an SSB; a CSI-RS; a Tracking Reference Signal, TRS; or an Aperiodic Reference Signal (not least such as an Aperiodic Tracking Reference Signal, A-TRS).

[0166] In some examples, the condition is that there is a relation between the first and second RSs. In some examples, the RS relation is defined by statically grouping the SSBs as discussed further below. In some examples, the UE may deduce a relation or association between the first and second RSs based on, for example, UE implementation.

[0167] In some examples, the gNB may indicate a relation or association between the first and second RSs in the signal received in block 201 , e.g. in a MAC CE TCI activation or indication command.

[0168] In some examples, the RS relation is defined by the gNB instructing the UE to assume that the first and second RSs are co-related based on a pre-defined criterion being met, as discussed further below.

[0169] In some examples the condition is that the first and second RSs are each members of the same group.

[0170] In some examples, the UE may receive, from the NW, information for enabling the UE to determine which group the first RS belongs to and which group the second RS belongs to - thereby enabling the UE to determine whether the first and second RSs belong to the same group. For example, the NW may determine / configure groups of RSs, i.e. assign each RS to a group, for instance such that adjacent RSs (e.g. from adjacent beams that would have experienced the same / similar path and channel conditions) are in the same group. The NW may send RS group information (e.g. via RRC signaling) to the UE for indicating which RSs are in which groups. This is discussed in further detail below with respect to FIGs. 7 and 8.

[0171] In some examples, the group to which each RS is a member of may be identified based on a time / frequency resource in which the RS is transmitted. For instance, where the RSs are SSBs that are periodically transmitted by a gNB in an SSB burst, a first group of a plurality of SSBs may be defined as the SSBs which are transmitted within a particular time internal. This is discussed in further detail below with respect to FIG. 10.

[0172] In some examples the condition is that the there is an association between the first RS and second RS. The association could be determined based on whether a criterion is satisfied. The criterion could be pre-determined and / or pre-configured to the UE by the NW.

[0173] The criterion could be that the first and second RSs are: part of the same group; received at the UE within a time interval (discussed in further detail below with respect to FIG. 10); and / or received from the same Transmission Reception Point, TRP, of the network node (discussed in further detail below with respect to FIG. 9).

[0174] Each RS may be associated with its own spatial position, such as a spatial index or an angular index / directionality. An association / group of RSs may be based on the spatial position. For instance, the association could be determined based on whether a criterion is satisfied, wherein the criterion is that a difference between the spatial position of the first RS and the spatial position of the second RS is within threshold value. This is discussed in further detail below with respect to FIG. 11 .

[0175] In block 205, depending on the determination in block 204, the UE performs a synchronisation process with the target TCI statr using the first RS. The synchronisation process may be SSB synchronization of a TCI switching procedure.

[0176] In this regard, the UE performs the synchronisation process (i.e. synchronises with the first RS) if the condition is not met. Whereas, if the condition is m et / f u If i I led, the synchronisation process is not performed, i.e. the UE skips / bypasses the synchronisation process for instance such that no further SSB synchronisation occurs during the TCI switching procedure).

[0177] Advantageously, examples may thereby avoid the need to perform the synchronisation process, and hence save time / reduce a time delay that there would otherwise be if the synchronisation process were performed. Examples may thereby enable faster target TCI state activation.

[0178] FIG. 6 schematically illustrates a method 300 according to an example of the subject matter described herein. The method 300 may be used to enable the method 200 of FIG. 5. In this regard, the steps of FIG. 6 may be precursor steps performed by the UE and NW prior to the UE and NW performing the method 200 of FIG. 5.

[0179] In block 301 , the UE transmits, to the NW, capability information 302. The capability information may be indicative of whether the UE is capable of: receiving RS group information, i.e. for indicating which RSs are in which group, and determining whether the first RS and the second RS are members of the group; and / or determining whether the first RS and the second RS are associated with one another (i.e. if an association criterion is met / fulf illed as discussed above).

[0180] In block 303, responsive to receipt of the capability information, the NW sends (e.g. via RRC signaling):

[0181] RS grouping information 304 (i.e. for indicating which RSs are in which group), and / or association information 305 (i.e. for enabling the UE to determine whether the first and second RS are associated with one another). Such association information may comprise information indicative of an association criterion to be met to determine whether the first and second RS are associated with one another.

[0182] FIG. 7 schematically illustrates an example of RS grouping in accordance with the subject matter described herein. In the following discussed examples, the RSs are SSBs of an SSB burst (the SSB burst comprising 64 SSBs, with SSB indexes: SSB#1 - SSB#64). The groups can be pre-configured by the gNB and signalled / transmitted to the UE by the gNB such that the UE is pre-configured by the gNB with information indicating the groups.

[0183] In this example, the SSBs of the SSB burst are segregated into groups and the UE identifies the groups based on how close they are in time. In this regard, the UE can consider that the SSB indexes which are transmitted close to each other in time (e.g. adjacent one another in time, or within a pre-determined time interval) belong to the same SSB group. As illustrated in the figure, SSB GROUP 1 contains SSB#1 , SSB#2, SSB#3. Similarly, SSB GROUP 2 contains SSB#4, SSB#5, SSB#6.

[0184] This enables the UE, having identified two RSs (e.g. an RS that is a QCL source for a target TCI and another RS that is a QCL source for an already / currently activated TCI) to determine whether the two RSs are members of the same group.

[0185] FIG. 8 schematically illustrates a further example of SSB grouping in accordance with the subject matter described herein. In this alternative example, the UE receives information from the gNB indicating the grouping of the RSs. In this regard, the gNB can send, to a UE via RRC signaling, SSB group information indicating the one or more groups and the constituent members of each group. For instance, SSB group information indicating that group 1 (transmitted from TRP 1 ) contains SSB 1 -3 and group 2 (transmitted from TRP 2) contains SSB 4-6.

[0186] This enables the UE, having identified two RSs (e.g. an RS that is a QCL source for a target TCI and another RS that is a QCL source for an already / currently activated TCI) to use the SSB group information determine whether the two RSs are members of the same group.

[0187] Instead of statically grouping SSBs as described above, the UE can be configured, e.g. via RRC signalling, to consider that a relation exists between certain SSBs based on a certain criteria being fulfilled.

[0188] There now follows a discussion of an example implementation of an embodiment of the present disclosure involving dual TCI operation.

[0189] There now follows a discussion of an example implementation of an embodiment of the present disclosure involving dual TCI operation.

[0190] Upon reception, from a gNB, of a MAC-CE command for TCI indication for PDCCH, or for TCI state activation for PDSCH, a UE can, instead of waiting to synchronize with a first SSB received after THARQ+SITIS, take certain steps autonomously without any additional signaling depending on a certain set of conditions being fulfilled.

[0191] The gNB and UE are aware of / can determine the following conditions while activating a codepoint with two TCI states TCI#A and TCI#B: condition A) If an SSB* of at least one of an already active TCI states and SSB of one of the TCI states TCI#A or TCI#B received in the MAC-CE command are corelated or source associated, i.e., belong to a same group. condition B) If SSBs of already active TCI states and SSBs for both of the TCI states TCI#A and TCI#B received in the MAC-CE command are co-related, i.e. belong to the same group.

[0192] *the references above to "SSB of a TCI state” mean "SSB to which a TCI state has a QCL relation”, for instance the SSB is a source RS for the TCI state. qNB behaviour

[0193] The gNB behaviour could be, for example, as per one of the two below discussed alternatives.

[0194] The gNB could, in one alternative "Alt 1 ”, configure sets of SSB groups, such as SSB group#1 , SSB group#2 etc. Each SSB group would consist of SSBs (such as illustrated in Figure 8)

[0195] FIG. 10 shows an example of spatial domain to time domain mapping / grouping for SSBs. For simplicity, the groups of SSBs are illustrated as occurring in a row. However, it is to be appreciated that there can be many alternate ways of grouping the SSBs such as considering the rows and columns. Also, in some examples, an SSB can be part of multiple SSB groups.

[0196] The gNB could, in another alternative "Alt 2” configure the UE to consider a relation exists between the SSBs

[0197] FIG. 11 illustrates SSB relations based on spatial indexing, wherein each SSB is associated with a spatial position, e.g. elevation, El, and azimuth, Az, angles.

[0198] As shown in the example of FIG. 11 , SSB #12 has El = -5° and Az = -15°. The UE can be configured, via RRC, to assume that a relation exists between SSBs as long as their relative positions do not exceed for example the following:

[0199] El: +15°, -15°;

[0200] Az: +10°, -10°

[0201] Alternately, the gNB could can provide, as part of a configuration of an SSB, an angular index. In the example of Figure 11 , SSB#12 has a position on (3, 2), where 3 is the row and 2 is the column. The UE could be configured to assume a relation exists between the SSBs as long as the vector comparison between the SSBs is < 2.

[0202] For example, SSB#12 has position (3,2). SSB#8 has a position (2,3). Similarly, SSB#17 has position (4,2). Both these SSBs can be assumed to be adjacent to SSB#12 since they fulfil the vector comparison criteria. Hence, the UE can assume that a relation exists between SSB#12 and SSB#17, and also between SSB#12 and SSB#8. However, SSB#19 has a position of (4,4). Comparing positions of SSB#12 and SSB#19, since the vector comparison between the two is > 2, they cannot be considered to be adjacent and hence UE cannot assume that a relation between the two exists.

[0203] UE behaviour

[0204] When the UE receives a MAC-CE command for TCI state activation, or TCI state indication, the UE performs a comparison to see if any SSBs for TCI states in an old active list have a relation to the new active TCI state list.

[0205] In case: one or more SSB of one of the TCI states received in the MAC-CE command for TCI activation, and one or more SSBs of one of the TCI states in the active TCI state list have a relation, then the UE will not need to synchronize with the one or more SSBs of one of the TCI states in the active TCI state list. Hence the UE can skip a synchronization part of a TCI switch delay.

[0206] The UE may (if needed, i.e. where a TCI state whose SSB does not have a relation to any of the active TCI states) synchronize with the first SSB transmission associated with the other TCI state after the MAC CE command is decoded by the UE (condition A). Additionally, if condition B is met, then the UE can reuse the synchronization information for both TCI states, and can conclude the TCI active state list update or TCI indication without monitoring SSB for TCI#A and TCI#B.

[0207] FIG. 12 schematically illustrates an example of a method 400 in accordance with the present disclosure.

[0208] In block 401 , a gNB receives a CSI report from a UE which indicates a best beam pair (e.g. a Tx beam of the gNB and an Rx beam of the UE).

[0209] The gNB may decide to perform a TCI switch based on the CSI report received from the UE.

[0210] In block 402, the gNB sends a MAC-CE to the UE, wherein the MAC-CE indicates two target TCI states. In this particular example, the target states are: TCI#A and TCI #B. TCI#A has a QCL relation with SSB#A, and TCI#B has a QCL relation with SSB#B. In block 403, the UE decodes the MAC-CE.

[0211] In block 404, following receipt and decoding of the MAC-CE with the target TCI states, the UE compares the SSBs of the TCI states which are already active with the SSBs of the received target TCI states. In this regard, the UE checks whether the SSB(s) that serve as a QCL source RS for already activated TCI states are associated with (e.g. in the same group as) the SSBs that serve as QCL source RSs for the target TCI states indicated in the received MAC-CE, namely SSB#A and SSB#B. If the SSBs belong to the same SSB group, or if there exists a relation between the SSBs, then the UE would not need to further synchronize. In particular, the UE may determine the SSB groups (e.g. via one of the above-discussed ways for determining SSB groups) and determines whether each of condition A and condition B is True or False.

[0212] Condition A ("A”) is defined as an SSB of at least one of the already active TCI state and an SSB of one of the target TCI states in the MAC CE belong to the same SSB group. For instance, SSB#A is in the same group as an SSB of at least one of the already active TCI state, and SSB#B is not in the same group as an SSB of at least one of the already active TCI state.

[0213] Condition B ("B”) is defined as SSBs of already active TCI states and SSBs for both of the target TCI states (i.e. TCI#A and TCI#B) in the MAC CE belong to the same SSM group. For instance, SSB#A and SSB#B are both in the same group as SSBs of already active TCI states.

[0214] If condition A=True and B=False, then in block 405, the UE synchronises only with Tfirst SSB of the other indicated TCI state, i.e. SSB#B. Instead of synchronising with SSB#A, the UE can make use of the UE’s current synchronisation with an SSB of an already active TCI state which is in the same group as SSB#A. In this regard, the UE synchronizes with only one SSB associated with the indicated TCI state (i.e. SSB#B) if the SSB of other TCI state (i.e. SSB#A) and an SSB of an already active TCI state are a part of the same SSB group or have a relation. Advantageously, this avoids the need to perform a synchronisation process on SSB#A as well as SSB#B), and hence saves time / reduces a time delay which may thereby enable faster target TCI state activation when two TCI states are activated simultaneously.

[0215] Following on from block 405, in block 406, the UE activates the target TCI states, i.e. the UE activates both TCI#A and TCI#B.

[0216] If condition B=True (which implies condition A=True), then in block 407, then no further synchronisation with SSBs is required. Instead the UE can make use of the UE’s current synchronisation with SSBs of already active TCI states. In this regard, if both SSBs associated with the indicated target TCI states and the SSBs of TCI states already active are part of the same SSB groups, or have a relation, then no further synchronization is required. Advantageously, by avoiding the need to perform such synchronisation this saves time / reduces a time delay which may thereby enable faster target TCI state activation when two TCI states are activated simultaneously.

[0217] Following on from block 407, in block 408, the UE activates the target TCI states, i.e. the UE activates both TCI#A and TCI#B.

[0218] If condition A=False and condition B=False, then in block 409, the UE synchronises with Tfirst SSB of each of the target TCI states, i.e. both SSB#A and SSB#B.

[0219] Following on from block 409, in block 410, the UE activates the target TCI states, i.e. the UE activates both TCI#A and TCI#B.

[0220] The example method of FIG. 12, uses two TCI state activation. However, the underlying principle may also apply for cases when the network activates any number of TCI states, which may require synchronization with the first SSB with a QCL relation to one or more activated TCI state(s).

[0221] It will be understood that each block and combinations of blocks illustrated in FIGs 5, 6 and 12, as well as the further functionality described above, can be implemented by various means, such as hardware, firmware, and / or software including one or more computer program instructions. For example, one or more of the functions described above can be performed by a duly configured apparatus (such as an apparatus, or UE, comprising means for performing the above described functionality). One or more of the functions / functionality described above can be embodied by a duly configured computer program (such as a computer program comprising computer program instructions which embody the functions / functionality described above and which can be stored by a memory storage device and performed by a processor).

[0222] As will be appreciated, any such computer program instructions can be loaded onto a computer or other programmable apparatus (i.e. hardware) to produce a machine, such that the instructions when performed on the programmable apparatus create means for implementing the functions / functionality specified in the blocks. These computer program instructions can also be stored in a computer-readable medium that can direct a programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the blocks. The computer program instructions can also be loaded onto a programmable apparatus to cause a series of operational actions to be performed on the programmable apparatus to produce a computer-implemented process such that the instructions which are performed on the programmable apparatus provide actions for implementing the functions / functionality specified in the blocks.

[0223] Various, but not necessarily all, examples of the present disclosure can take the form of a method, an apparatus, or a computer program. Accordingly, various, but not necessarily all, examples can be implemented in hardware, software or a combination of hardware and software.

[0224] Various, but not necessarily all, examples of the present disclosure are described using flowchart illustrations and schematic block diagrams. It will be understood that each block (of the flowchart illustrations and block diagrams), and combinations of blocks, can be implemented by computer program instructions of a computer program. These program instructions can be provided to one or more processor(s), processing circuitry or controller(s) such that the instructions which execute on the same create means for causing implementing the functions specified in the block or blocks, i.e. such that the method can be computer implemented. The computer program instructions can be executed by the processor(s) to cause a series of operational block / steps / actions to be performed by the processor(s) to produce a computer implemented process such that the instructions which execute on the processor(s) provide block / steps for implementing the functions specified in the block or blocks.

[0225] Accordingly, the blocks support: combinations of means for performing the specified functions; combinations of actions for performing the specified functions; and computer program instructions / algorithm for performing the specified functions. It will also be understood that each block, and combinations of blocks, can be implemented by special purpose hardware-based systems which perform the specified functions or actions, or combinations of special purpose hardware and computer program instructions.

[0226] Various, but not necessarily all, examples of the present disclosure provide both a method and corresponding apparatus comprising various modules, means or circuitry that provide the functionality for performing / applying the actions of the method. The modules, means or circuitry can be implemented as hardware, or can be implemented as software or firmware to be performed by a computer processor. In the case of firmware or software, examples of the present disclosure can be provided as a computer program product including a computer readable storage structure embodying computer program instructions (i.e. the software or firmware) thereon for performing by the computer processor.

[0227] FIG. 13 schematically illustrates a block diagram of an apparatus 10 for performing the methods, processes, procedures and signalling described in the present disclosure and illustrated in FIGs. 5, 6 and 12, in this regard the apparatus can perform the roles of the UE 110 or a gNB 120, in the methods illustrated and described above. The component blocks of FIG. 13 are functional and the functions described can be performed by a single physical entity.

[0228] The signals sent and received may be electromagnetic signals encoding (in accordance with an encoding process) information. The signal X may be an electromagnetic signal encoding information and configured to [technical effect] .... The apparatus comprises a controller 11 , which could be provided within a device such as a UE 110, a RAN node 120.

[0229] The controller 11 can be embodied by a computing device, not least such as those mentioned above. In some, but not necessarily all examples, the apparatus can be embodied as a chip, chip set, circuitry or module, i.e. for use in any of the foregoing. As used here 'module’ refers to a unit or apparatus that excludes certain parts / components that would be added by an end manufacturer or a user.

[0230] Implementation of the controller 11 can be as controller circuitry. The controller 11 can be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

[0231] The controller 11 can be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 14 in a general- purpose or special-purpose processor 12 that can be stored on a computer readable storage medium 13, for example memory, or disk etc, to be executed by such a processor 12.

[0232] The processor 12 is configured to read from and write to the memory 13. The processor 12 can also comprise an output interface via which data and / or commands are output by the processor 12 and an input interface via which data and / or commands are input to the processor 12. The apparatus can be coupled to or comprise one or more other components 15 (not least for example: a radio transceiver, sensors, input / output user interface elements and / or other modules / devices / components for inputting and outputting data / commands).

[0233] The memory 13 stores instructions such as a computer program 14 comprising such instructions (e.g. computer program instructions / code) that controls the operation of the apparatus 10 when loaded into the processor 12. The instructions of the computer program 14, provide the logic and routines that enables the apparatus to perform the methods, processes and procedures described in the present disclosure and illustrated in FIGs. 5, 6 and 12. The processor 12 by reading the memory 13 is able to load and execute the computer program 14.

[0234] The instructions may be comprised in a computer program, a non-transitory computer readable medium, a computer program product, a machine readable medium. The term "non-transitory,” as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. RAM vs. ROM). In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program.

[0235] Although the memory 13 is illustrated as a single component / circuitry it can be implemented as one or more separate components / circuitry some or all of which can be integrated / removable and / or can provide permanent / semi-permanent / dynamic / cached storage.

[0236] Although the processor 12 is illustrated as a single component / circuitry it can be implemented as one or more separate components / circuitry some or all of which can be integrated / removable. The processor 12 can be a single core or multi-core processor.

[0237] The apparatus can include one or more components for effecting the methods, processes and procedures described in the present disclosure and illustrated in FIGs. 5, 6 and 12. It is contemplated that the functions of these components can be combined in one or more components or performed by other components of equivalent functionality. The description of a function should additionally be considered to also disclose any means suitable for performing that function.

[0238] Where a structural feature has been described, it can be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

[0239] Although examples of the apparatus have been described above in terms of comprising various components, it should be understood that the components can be embodied as or otherwise controlled by a corresponding controller or circuitry such as one or more processing elements or processors of the apparatus. In this regard, each of the components described above can be one or more of any device, means or circuitry embodied in hardware, software or a combination of hardware and software that is configured to perform the corresponding functions of the respective components as described above.

[0240] The apparatus can, for example, be a client device, a server device, a mobile cellular telephone, a base station in a mobile cellular telecommunication system, a wireless communications device, a hand-portable electronic device, a location / position tag, a hyper tag etc. The apparatus can be embodied by a computing device, not least such as those mentioned above. However, in some examples, the apparatus can be embodied as a chip, chip set, circuitry or module, i.e. for use in any of the foregoing.

[0241] In one example, the apparatus is embodied on a hand held portable electronic device, such as a mobile telephone, mobile communication device, wearable computing device or personal digital assistant, that can additionally provide one or more audio / text / video communication functions (for example tele-communication, video-communication, and / or text transmission (Short Message Service (SMS) / Multimedia Message Service (MMS) / emailing) functions), interactive / non-interactive viewing functions (for example web-browsing, navigation, TV / program viewing functions), music recording / playing functions (for example Moving Picture Experts Group-1 Audio Layer 3 (MP3) or other format and / or (frequency modulation / amplitude modulation) radio broadcast recording / playing), downloading / sending of data functions, image capture function (for example using a (for example in-built) digital camera), and gaming functions, or any combination thereof.

[0242] In examples where the apparatus is provided within a UE 110, the apparatus comprises: at least one processor 12; and at least one memory 13 storing instructions that, when executed by the at least one processor 12, cause the apparatus at least to: receive, from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; determine whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and perform at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

[0243] In examples where the apparatus is provided within a RAN node 120, the apparatus comprises: at least one processor 12; and at least one memory 13 storing instructions that, when executed by the at least one processor 12, cause the apparatus at least to: receive, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and transmit, to the UE, information indicating the group based at least in part on the received capability information.

[0244] According to some examples of the present disclosure, there is provided a system comprising at least one UE 110 and a RAN node 120 as described above.

[0245] The above described examples find application as enabling components of: tracking systems, automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and / or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things (IOT); Vehicle-to-everything (V2X), virtualized networks; and related software and services.

[0246] The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility.

[0247] FIG. 14, illustrates a computer program 14 which may be conveyed via a delivery mechanism 20. The delivery mechanism 20 can be any suitable delivery mechanism, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a solid-state memory, a record medium such as a Compact Disc Read-Only Memory (CD- ROM) or a Digital Versatile Disc (DVD) or an article of manufacture that comprises or tangibly embodies the computer program 14. The delivery mechanism can be a signal configured to reliably transfer the computer program. An apparatus can receive, propagate or transmit the computer program as a computer data signal.

[0248] In certain examples of the present disclosure, there is provided a computer program comprising instructions, which when executed by an apparatus (UE 110), cause the apparatus to perform at least the following or for causing performing at least the following: receiving, from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; determining whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and performing at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination. In certain examples of the present disclosure, there is provided computer program comprising instructions, which when executed by an apparatus (RAN node 120), cause the apparatus to perform at least the following or for causing performing at least the following: receiving, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and transmitting, to the UE, information indicating the group based at least in part on the received capability information.

[0249] References to 'computer program’, 'computer-readable storage medium’, 'computer program product’, 'tangibly embodied computer program’ etc. or a 'controller’, 'computer’, 'processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other devices. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

[0250] As used in this application, the term 'circuitry’ can refer to one or more or all of the following:

[0251] (a) hardware-only circuitry implementations (such as implementations in only analog and / or digital circuitry) and

[0252] (b) combinations of hardware circuits and software, such as (as applicable):

[0253] (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and

[0254] (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and

[0255] (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (for example firmware) for operation, but the software may not be present when it is not needed for operation.

[0256] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0257] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0258] Features described in the preceding description can be used in combinations other than the combinations explicitly described.

[0259] Although functions have been described with reference to certain features, those functions can be performable by other features whether described or not.

[0260] Although features have been described with reference to certain examples, those features can also be present in other examples whether described or not. Accordingly, features described in relation to one example / aspect of the disclosure can include any or all of the features described in relation to another example / aspect of the disclosure, and vice versa, to the extent that they are not mutually inconsistent.

[0261] Although various examples of the present disclosure have been described in the preceding paragraphs, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as set out in the claims. For example, whilst certain examples have been discussed with respect to dual TCI operation, other examples may involve single TCI operation.

[0262] The term 'comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X can comprise only one Y or can comprise more than one Y. If it is intended to use 'comprise’ with an exclusive meaning then it will be made clear in the context by referring to "comprising only one ...” or by using "consisting”.

[0263] In this description, the wording 'connect’, 'couple’ and 'communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e. so as to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components.

[0264] As used herein, the term "determine / determining" (and grammatical variants thereof) can include, not least: evaluating, calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), retrieving / accessing (for example, retrieving / accessing data in a memory), obtaining and the like. Also, " determine / determining" can include resolving, selecting, choosing, establishing, inferring and the like.

[0265] As used herein, a description of an action should also be considered to disclose enabling, and / or causing, and / or controlling that action. For example, a description of transmitting information should also be considered to disclose enabling, and / or causing, and / or controlling transmitting information. Similarly, for example, a description of an apparatus transmitting information should also be considered to disclose at least one means or controller of the apparatus enabling, and / or causing, and / or controlling the apparatus to transmit the information.”

[0266] The term "means” as used in the description and in the claims may refer to one or more individual elements configured to perform the corresponding recited functionality or functionalities, or it may refer to several elements that perform such functionality or functionalities. Furthermore, several functionalities recited in the claims may be performed by the same individual means or the same combination of means. For example performing such functionality or functionalities may be caused in an apparatus by a processor that executes instructions stored in a memory of the apparatus.

[0267] References to a parameter, or value of a parameter, should be understood to refer to "data indicative of”, "data defining” or "data representative of” the relevant parameter / parameter value if not explicitly stated (unless the context demands otherwise). The data may be in any way indicative of the relevant parameter / parameter value, and may be directly or indirectly indicative thereof.

[0268] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ’example’ or 'for example’, 'can’ or 'may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some or all other examples. Thus 'example’, 'for example’, 'can’ or 'may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class.

[0269] In this description, references to "a / an / the” [feature, element, component, means ...] are used with an inclusive not an exclusive meaning and are to be interpreted as "at least one” [feature, element, component, means ...] unless explicitly stated otherwise. That is any reference to X comprising a / the Y indicates that X can comprise only one Y or can comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use 'a’ or 'the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of 'at least one’ or 'one or more’ can be used to emphasise an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning. As used herein, "at least one of the following: ” and "at least one of ” and similar wording, where the list of two or more elements are joined by "and” or "or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0270] The presence of a feature (or combination of features) in a claim is a reference to that feature (or combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

[0271] In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described. In the above description, the apparatus described can alternatively or in addition comprise an apparatus which in some other examples comprises a distributed system of apparatus, for example, a client / server apparatus system. In examples where an apparatus provided forms (or a method is implemented as) a distributed system, each apparatus forming a component and / or part of the system provides (or implements) one or more features which collectively implement an example of the present disclosure. In some examples, an apparatus is re-configured by an entity other than its initial manufacturer to implement an example of the present disclosure by being provided with additional software, for example by a user downloading such software, which when executed causes the apparatus to implement an example of the present disclosure (such implementation being either entirely by the apparatus or as part of a system of apparatus as mentioned hereinabove).

[0272] The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0273] Whilst endeavouring in the foregoing specification to draw attention to those features of examples of the present disclosure believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon. The examples of the present disclosure and the accompanying claims can be suitably combined in any manner apparent to one of ordinary skill in the art. Separate references to an "example”, "in some examples” and / or the like in the description do not necessarily refer to the same example and are also not mutually exclusive unless so stated and / or except as will be readily apparent to those skilled in the art from the description. For instance, a feature, structure, process, block, step, action, or the like described in one example may also be included in other examples, but is not necessarily included.

[0274] Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present disclosure. Further, while the claims herein are provided as comprising specific dependencies, it is contemplated that any claims can depend from any other claims and that to the extent that any alternative embodiments can result from combining, integrating, and / or omitting features of the various claims and / or changing dependencies of claims, any such alternative embodiments and their equivalents are also within the scope of the disclosure.

Claims

We claim:1 . An apparatus comprising: means for receiving, from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; means for determining whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and means for performing at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

2. The apparatus of claim 1 , wherein at least one TCI state, which is activated at the apparatus, has at least one QCL relation with the at least one second RS.

3. The apparatus of any previous claim, wherein the information indicating the at least one target TCI state comprises at least one of the following: an indication of at least one TCI state that the apparatus is to switch to; or an indication of at least one TCI state that the apparatus is to activate.

4. The apparatus of any previous claim, wherein: the information indicating at least one target TCI state is received via at least one of the following: a Medium Access Control, MAC, layer signal; a MAC Control Element, CE, command for TCI indication for Physical Downlink Control Channel, PDCCH; or a MAC-CE command for TCI state activation for Physical Downlink Shared Channel, PDSCH.

5. The apparatus of any previous claim, wherein the at least one first RS is a QCL source RS of the at least one target TCI state.

6. The apparatus of any previous claim, wherein the at least one first and second RSs comprise at least one of the following: at least one synchronization signal; at least one Synchronization Signal Block, SSB; at least one a Channel-State Information Reference Signal, CSI-RS; at least one Tracking Reference Signal, TRS; or at least one Aperiodic Reference Signal.

7. The apparatus of any previous claim, wherein determining whether the at least one condition has been met comprises determining whether:the at least one first RS is a member of a group of a plurality of RSs, and the at least one second RS is a member of the same group.

8. The apparatus of claim 7, wherein the group to which the at least one first RS is a member of is identified based at least in part on a time / frequency resource through which the at least one first RS is transmitted.

9. The apparatus of claim 7 or 8, wherein the apparatus further comprises means for receiving, from the network node, information indicating the group.

10. The apparatus of any previous claim, wherein determining whether the at least one condition has been met comprises determining whether there is an association between the at least one first RS and the at least one second RS, and wherein determining whether there is an association comprises determining whether at least one criterion is satisfied.11 . The apparatus of claim 10, wherein the at least one criterion is pre-determined.

12. The apparatus of claim 10 or 11 , wherein the at least one criterion is that the at least one first RS and the at least second one RS are received within a time interval.

13. The apparatus of claim 10, 11 or 12, wherein the at least one criterion is that the at least one first RS and the at least one second RS are received from the same Transmission Reception Point, TRP, of the network node.

14. The apparatus of any previous claim, wherein the apparatus comprises means for receiving information indicative of at least one spatial position associated with the at least one first RS, and at least one spatial position associated with the at least one second RS; and wherein the at least one criterion is that a difference between the at least one spatial position of the at least one first RS and the at least one spatial position of the at least one second RS is within at least one threshold value.

15. The apparatus of any previous claim, wherein the at least one synchronisation process is at least one SSB synchronization of a TCI switching procedure.

16. The apparatus of any previous claim, wherein, in response to determining that the at least one condition is fulfilled, the synchronisation process is not performed.

17. The apparatus of any previous claim when dependent upon claim 7, wherein the apparatus further comprises means for transmitting, to the network node, information indicating that the apparatus is capable of at least one of the following: receiving the information indicating the group; anddetermining whether the at least one first RS and the at least one second RS are members of the group.

18. The apparatus of any previous claim when dependent upon claim 10, wherein the apparatus further comprises means for transmitting, to the network node, information indicating that the apparatus is capable of: determining whether there is the association between the at least one first RS and the at least one second RS.

19. A User Equipment, UE, comprising the apparatus of any previous claim.

20. An apparatus comprising: means for receiving, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and means for transmitting, to the UE, information indicating the group based at least in part on the received capability information.21 . The apparatus of claim 20, further comprising: means for transmitting, to the UE, information indicating the at least one target TCI state.

22. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a network node, information indicating at least one target Transmission Configuration Indication, TCI, state, wherein the at least one target TCI state has at least one Quasi Co-Location, QCL, relation with at least one first Reference Signal, RS; determine whether at least one condition has been met, wherein the at least one condition is based at least in part on: the at least one first RS, and at least one second RS with which the apparatus is synchronised; and perform at least one synchronisation process with the at least one target TCI state using the at least one first RS, wherein performing the at least one synchronisation process is based at least in part on the determination.

23. The apparatus of claim 22, wherein at least one TCI state, which is activated at the apparatus, has at least one QCL relation with the at least one second RS.

24. The apparatus of any of previous claims 22 to 23, wherein the information indicating the at least one target TCI state comprises at least one of the following: an indication of at least one TCI state that the apparatus is to switch to; or an indication of at least one TCI state that the apparatus is to activate.

25. The apparatus of any of previous claims 22 to 24, wherein: the information indicating at least one target TCI state is received via at least one of the following: a Medium Access Control, MAC, layer signal; a MAC Control Element, CE, command for TCI indication for Physical Downlink Control Channel, PDCCH; or a MAC-CE command for TCI state activation for Physical Downlink Shared Channel, PDSCH.

26. The apparatus of any of previous claims 22 to 25, wherein the at least one first RS is a QCL source RS of the at least one target TCI state.

27. The apparatus of any of previous claims 22 to 26, wherein the at least one first and second RSs comprise at least one of the following: at least one synchronization signal; at least one Synchronization Signal Block, SSB; at least one a Channel-State Information Reference Signal, CSI-RS; at least one Tracking Reference Signal, TRS; or at least one Aperiodic Reference Signal.

28. The apparatus of any of previous claims 22 to 27, wherein determining whether the at least one condition has been met comprises determining whether: the at least one first RS is a member of a group of a plurality of RSs, and the at least one second RS is a member of the same group.

29. The apparatus of claim 28, wherein the group to which the at least one first RS is a member of is identified based at least in part on a time / frequency resource through which the at least one first RS is transmitted.

30. The apparatus of claim 28 or 29, wherein the apparatus further comprises means for receiving, from the network node, information indicating the group.31 . The apparatus of any of previous claims 22 to 30, wherein determining whether the at least one condition has been met comprises determining whether there is an association between the at least one first RS and the at least one second RS, and wherein determining whether there is an association comprises determining whether at least one criterion is satisfied.

32. The apparatus of claim 31 , wherein the at least one criterion is pre-determined.

33. The apparatus of claim 31 or 32, wherein the at least one criterion is that the at least one first RS and the at least second one RS are received within a time interval.

34. The apparatus of claim 31 , 32 or 33, wherein the at least one criterion is that the at least one first RS and the at least one second RS are received from the same Transmission Reception Point, TRP, of the network node.

35. The apparatus of any of previous claims 22 to 34, wherein the apparatus comprises means for receiving information indicative of at least one spatial position associated with the at least one first RS, and at least one spatial position associated with the at least one second RS; and wherein the at least one criterion is that a difference between the at least one spatial position of the at least one first RS and the at least one spatial position of the at least one second RS is within at least one threshold value.

36. The apparatus of any of previous claims 22 to 35, wherein the at least one synchronisation process is at least one SSB synchronization of a TCI switching procedure.

37. The apparatus of any of previous claims 22 to 36, wherein, in response to determining that the at least one condition is fulfilled, the synchronisation process is not performed.

38. The apparatus of any of previous claims 22 to 37 when dependent upon claim 28, wherein the apparatus further comprises means for transmitting, to the network node, information indicating that the apparatus is capable of at least one of the following: receiving the information indicating the group; and determining whether the at least one first RS and the at least one second RS are members of the group.

39. The apparatus of any of previous claims 22 to 38 when dependent upon claim 31 , wherein the apparatus further comprises means for transmitting, to the network node, information indicating that the apparatus is capable of: determining whether there is the association between the at least one first RS and the at least one second RS.

40. A User Equipment, UE, comprising the apparatus of any of previous claims 22 to 39.41 . An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:receive, from a User Equipment, UE, capability information wherein the capability information indicates whether the UE is capable of: receiving an indication of a group of a plurality of Reference Signals, RSs, determining whether to perform at least one synchronisation process using at least one first RS, wherein the determination is based at least in part on whether the at least one first RS and at least one second RS are members of the indicated group; wherein the at least one first RS is at least one RS with which at least one target TCI state has a QCL relation, and wherein the at least one second RS is at least one RS with which the UE is synchronised; and transmit, to the UE, information indicating the group based at least in part on the received capability information.

42. The apparatus of claim 20, wherein the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to: transmit, to the UE, information indicating the at least one target TCI state.

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