GB2575691A - Improvements in and relating to beam management in a telecommunication system - Google Patents

Abstract

Disclosed is a method of beam management in a telecommunication system comprising a User Equipment (UE) 110, and a transception point (TRP) 120. The TRP provides the UE with details of candidate beams, arranged in one or more sets of quasi-co-­located (QCL), beams. The UE periodically performs measurements of the candidate beams. The UE senses likely failure of a current beam and triggers a link recovery procedure whereby the UE signals the TRP with details of the best of the candidate beams and the bestof the sets. The TRP messages, via backhaul, a relay TRP (rTRP), associated with the best of the candidate beams or the best of the sets. The UE monitors a control resource set, (CORESET), and then establishes communication with the relay TRP. The method seeks to improve beam failure recovery in a multi-TRP network environment.

Description

Improvements in and relating to beam management in a telecommunication system

This invention relates to a procedure and apparatus for signalling to support beam management in Fifth Generation (5G or new radio, NR) integrated access backhaul (IAB) and multi-transception (transmission/reception) points (TRP). In a network with IAB, NR relay transception points (rTRPs) are used to increase coverage and provide access to users and wireless backhaul between TRPs and rTRPs. These rTRPs and TRPs may not be quasi-colocated (QCL), which means that their beams may have different large-scale parameters, Doppler shifts, etc.

In a multi-TRP network, coordinated TRPs may not provide QCL beams either. In these cases, the prior art beam management framework, which requires the user equipment (UE) to only detect QCL beams when the link failure is about to occur, does not support NR IAB and multiTRP scenarios. Embodiments of this invention include information on sets of QCL beams and cell IDs in the system information block (SIB) such that UEs can acquire this information during the connection establishment phase.

In NR, a UE is configured with one control resource set (CORESET) by higher layer parameter Beam-failure-Recovery-Response-CORESET. When beam failure happens, the UE will monitor Physical Downlink Control Channel (PDCCH) in the Beam-failure-RecoveryResponse-CORESET for details of beam failure recovery.

That beam failure is about to happen implies two things: 1) the default CORESET might not be correctly received because of low link quality; and 2) beam reporting might not be received correctly due to low link quality. Moreover, long latency is expected in beam failure recovery.

In NR, integrated access backhaul (IAB) can be enhanced to handle beam failure recovery. Layer 3 (L3) relay TRP (rTRP) (similar to L3 relay node (RN) in LTE) is expected to be supported in IAB. In L3 rTRP, a radio resource control (RRC) connection needs to be established between the UE and the rTRP. The potential rTRPs are shown in Figure 1. This shows a layer 3 connection between UE and rTRP. It also shows Layer 1 and 2 connections between UE and rTRP and rTRP and TRP, respectively.

In NR, a UE may receive beams from multiple TRPs. This multi-TRP scenario can be enhanced to handle beam failure recovery. These TRPs are operable to coordinate and exchange certain information. In the multi-TRP case, even with one link/beam failure from one

TRP, another reliable link/beam still exists with another TRP and this link can be used to facilitate the beam/link failure for another TRP. This is illustrated in Figure 2, where a single UE 10 is in a position to receive beams from TRP1 20 and TRP2 30. However, in the prior at, neither IAB nor multi-TRP scenario is able to provide efficient beam failure recover because only QCL beams can be used in the current NR specification, which is depicted in Figure 3, which shows UE 10, operable to receive beams from TRP 40.

It is an aim of embodiments of the present invention to address shortcomings in the prior art, whether mentioned herein or not.

According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

In the following, this terminology is used:

Candidate beams: these are numbered 1,2,3,4,...N. Each beam has an id.

QCL Beamsets: These are labelled “QcIBeamSetl{1,2,3,...,8}”. Each QCLBeamSet has an id, and each QCLBeamSet consists of beams that are QCL with respect to each other. In other words, all beams in a particular QCL beam set are QCL with respect to other beams in the same set. Different QCL beamsets are not necessarily QCL with respect to each other.

Cell IDs: Each cell is numbered and has an id.

CellQcISets: Each cell has a number of QCLBeamSets included therein.

According to a first aspect of the present invention, there is provided a method of beam management in a telecommunication system comprising a User Equipment, UE, and a transception point, TRP, comprising the steps of:

the TRP providing the UE with details of candidate beams, arranged in one or more sets of quasi-co-located, QCL, beams;

the UE periodically performing measurements of the candidate beams;

the UE sensing likely failure of a current beam and triggering a link recovery procedure whereby the UE signals the TRP with details of the best of the candidate beams and the best of the sets;

the TRP messaging, via backhaul, a relay TRP, rTRP, associated with the best of the candidate beams or the best of the sets;

the UE monitoring a control resource set, CORESET, and then establishing communication with the relay TRP.

In an embodiment, if the rTRP is a L1/L2 rTRP, the step of establishing communication with it comprises the rTRP sending a control channel.

In an embodiment, the control channel is a PDCCH.

In an embodiment, if the rTRP is a L3 rTRP, the step of establishing communication with it comprises a RACH procedure between the TRP and the UE and a RRC connection procedure between the rTRP and the UE.

In an embodiment, if one or more of the candidate beams are associated with a L3 relay TRP, then the TRP additionally provides the UE with details of the cell ID associated with the L3 rTRP.

In an embodiment, the step of the UE sensing likely failure of a current beam comprises the UE sensing the current beam power falling below a predefined threshold.

In an embodiment, the best of the sets is determined on the basis of average beam qualities in a particular set.

In an embodiment, the step of the TRP providing the UE with details of candidate beams, the TRP determines the candidate beams on the basis of knowledge of a beam used for backhaul and a TRP access beams presently used to contact the UE.

According to a second aspect of the present invention, there is provided a TRP operable to determine candidate beams, arranged in one or more sets of quasi-co-located, QCL, beams, and to forward details of the candidate beams to a UE, the TRP being further operable to receive from the UE, in the event of the UE triggering a link recovery procedure, details of the best of the candidate beams and the best of the sets and being further operable to message, via backhaul, a relay TRP, rTRP, associated with the best of the candidate beams or the best of the sets.

According to a third aspect of the present invention, there is provided a UE operable to: receive from a TRP details of candidate beams, arranged in one or more sets of quasi-colocated, QCL, beams;

periodically perform measurements of the candidate beams;

sense likely failure of a current beam and trigger a link recovery procedure whereby the UE is operable to signal the TRP with details of the best of the candidate beams and the best of the sets;

monitor a control resource set, CORESET, and then establish communication with the relay TRP.

According to a fourth aspect of the present invention, there is provided a communication system operable to perform the method of the first aspect.

According to a fifth aspect of the present invention, there is provided a communication system comprising the TRP of the second and the UE of the third aspect.

Embodiments of the present invention offer several advantages over the prior art.

In particular, embodiments of the invention are enabled by virtue of RRC signalling for beam management including details of one or more QCL beam sets, cell IDs. Note that the QCL sets include sets of beams which are QCL with respect to each other, but different QCL sets are not necessarily QCL to other QCL sets.

As a result, beam management in a distributed-TRP/multi-cell NR IAB network supported, in a way which is not possible in prior art solutions. Furthermore, improved coverage and IAB network operation is supported, in the proposed beam management embodiments. Embodiments of the invention provide a procedure for a UE to discover non-QCL beams in link failure, which is not possible in prior art solutions.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which:

Figure 1 shows potential relay TRPs in NR IAB setup, according to the prior art;

Figure 2 shows a multi-TRP setup in NR, according to the prior art;

Figure 3 shows beam reconfiguration according to the prior art;

Figure 4 shows a NR network with IAB using L1/L2 rTRPs according to an embodiment of the invention;

Figure 5 shows a NR network with IAB using L3 rTRPs according to an embodiment of the invention;

Figure 6 shows a message sequence according to an embodiment of the invention;

Figure 7 shows another message sequence according to an embodiment of the invention;

Figure 8 shows RRC signalling according to an embodiment of the invention;

Figure 9 shows RRC signalling according to an embodiment of the invention;

Figure 10 shows CORESETs according to an embodiment of the invention;

Figure 11 shows CORESETs according to an embodiment of the invention;

Figure 12 shows CORESETs according to an embodiment of the invention;

Figure 13 shows a flowchart showing a method according to an embodiment of the invention;

Figure 14 shows a backhauling configuration according to an embodiment of the present invention; and

Figure 15 shows a candidate beam estimation process.

In NR IAB, TRPs and rTRPs have multiple beams and they can establish connections to UEs with these beams. However, these beams are not QCL, i.e., they do not share common largescale parameters, Doppler effects, delay spreads etc. Therefore, the prior art NR specification does not provide support on link reconfiguration in IAB. An example is shown in Error! Reference source not found.. The UE 10 can only access QCL beams which are from the TRP 40, i.e., beams 1-8.

In the prior art NR specification, beam management only supports QCL beams. As a result, a UE in an IAB scenario cannot access beams from both TRPs and rTRPs. Embodiments of the present invention enable UEs to access QCL beams in a cell with distributed L1/2 rTRPs/TRPs, as shown in Figure 4. With the invention, the UE 110 can access QCL beams which are from the TRP 120 and rTRP1 130 and rTRP2 140, i.e., beams 1-16.

In addition, embodiments of the present invention enable UEs to access QCL beams in a cell with distributed L3 rTRPs - rTRP1 230 and rTRP2 240, as shown in Figure 5. In embodiments of the invention, the UE 210 can access QCL beams which are from the TRP 220 and rTRPs 230, 240, i.e., beams 1-16.

Furthermore, in embodiments of the invention UEs are able to access QCL beams from distributed TRPs in a multi-TRP scenario. The UE can access QCL beams which are from the TRPs.

According to embodiments ofthe invention, a UE acquires details of sets of QCL beams during connection establishment. The information of a beam list with sets of QCL beams is carried via signalling from the base station (BS). As soon as the UE acquires the information on the sets of QCL beams, the UE can report the index of the best beam inside the beam list. A set of QCL beams are beams from either one TRP or one rTRP. Multiple sets of QCL beams are included in the beam list. Therefore, beam management and/or beam recovery in IAB and multi-TRP can be performed.

Figure 6 illustrates the procedure which is followed. By referring to Figures 4 and 6: For L1/2 rTRPs (as shown in Figure 4), the TRP 120 informs the UE 110, via a message (S100), about the list of candidate beam Reference Signals (RS) list and indicates which beams are QCL. As shown in Figure 4, when the NR IAB network is formed with L1/L2 rTRPs 130, 140, TRP 120 and rTRPs 130, 140 share the same cell ID i.e. Cell 1. In this case, the TRP 120 only needs to inform the UE 110 about which candidate beams in the list are QCL. To achieve this, the TRP 120 sends a message to the UE 110. The UE 110 periodically performs measurement (S110) on the beams in the different QCL beam sets in the list. When the UE 110 senses that it is likely to have beam failure, which can be inferred if its current beam power level is lower than a predefined threshold, then, the link recovery procedure is triggered (S120) and the UE 110 feeds back (S130) the best beam ID and the best QCL set ID to the TRP 120 and the best beam ID in the best QCL set.

The TRP 120 forwards this message (S140) to the L1/L2 rTRP 130, 140 associated with the best beam ID or the best QCL set ID via backhaul. Next, the UE 110 monitors (S150) the preconfigured control resource set (CORESET) for beam recovery, on which the L1/L2 rTRP 130, 140 will send (S160) physical downlink control channel (PDCCH).

In another embodiment using L3 rTRPs, as shown in Figure 5, the procedure is slightly different, as shown in Figure 7.

For L3 rTRPs 230, 240, as shown in Figure 5, the TRP 220 informs the UE 210 via a message (S200) about the list of candidate beam RS list and indicates which beams are QCL and cell IDs associated to these beams. When the NR IAB network is formed with L3 rTRPs 230, 240, TRP 220 and rTRPs 230, 240 share different cell IDs (Celli and Cell2, respectively).

In this case, the TRP 220 needs to inform the UE 210 about which candidate beams in the list are QCL and which QCL beam sets are with the same cell ID. To achieve this, the TRP 220 will send a message (S200) to the UE 210 and the UE acquires cell IDs in order to measure beams in other L3 rTRPs 230, 240. The UE will periodically perform measurement (S210) on beams in the different QCL beam sets in the list.

When the UE senses that it is likely to have beam failure, which can be inferred if its current beam power level is lower than a predefined threshold, then, the link recovery procedure is triggered (S220) and UE will feedback (S230) the best beam ID and the best QCL set ID to the TRP and the best beam ID in the best QCL set.

The TRP will forward this message (S240) to the L3 rTRP associated with the best beam ID via backhaul. Next, the UE will monitor (S250) the preconfigured CORESET for beam recovery, on which the L3 rTRP will send PDCCH. Ifthe best beam/best QCL set belongs to a L3 rTRP, then an initial access procedure (S270) and a RRC connection procedure (S280) are needed between the UE and the L3 rTRP.

The message S110, S200 on candidate beam RS list and QCL indicators and cell IDs is sent from the TRP 120, 220 to the UE 110, 210 via RRC signalling. These beam RS lists, QCL indicators and cell IDs correspond to one Beam-failure-Recovery-Response-CORESET. To represent different IAB network settings, Figure 8 and Figure 9 show the diagrams of contents in the RRC signalling a NR IAB network with L1/L2 rTRPs and L3 rTRPs, respectively. Beam sets may be identified using RRC signaling, or as set out in the following paragraphs. Each beam has an ID; each QCL beam set contains a sequence of beam IDs; and each Cell QCL set contains a sequence of QCL beam sets.

Figure 8 shows there are 16 possible beams available to the UE 110. Beams 1 to 8 are from TRP 120; beams 9 to12 are from rTRP1 130; and beams 13 to16 are from rTRP2 140. These beams constitute QCL beam sets 1, 2 and 3 respectively and are identified as such in the signalling.

Figure 9 shows similar information, but further information is provided regarding the different Cell IDs associated with the various beams.

If N denotes the total number of beams and 1,2,3,...,N denotes the beam IDs, the in the context of NR, a beam ID has a one-to-one mapping to the candidate beam resource in the current NR beam management signalling. If Q is the number of QCL beam sets and M is the number of cells. Then, an example RRC signalling is constructed as below:

δ£δ3ϊδ·1&'5ΐ3.ί2Γ€3χε5ΐ£ ^: = SSOIE&CS ί — Rererence siarusl ^ssci. to idsritiry cajidLS&te bsas.

beas^ailttreCandidateSea^escurce 2, 2,.3,..., K’ — CCL b&s.^ s-et. IDs arid £CL .toears. indications in escb OCL ’c-eat'.. set.

besiTiFall^reQclEeajy.Sets QclEeaTtSeti^l, 2,3,..., S;, Qo2SeasSet2 ί 9_f... CcLBeaitSatG'ilS,...

— Candssate ceil IDs for te-e&sl· raana.g!=fsent beaKFailoreCellllis CellZDl, CelllDl, ...,251112^

-- Cell and CL· beiat set association be ssiFs.il LixeCel IQciSe t a Cel 2..Ξ Di {OclSeai&Set 1 ?, Ce 1IID2 ;' QclBea^Se 12,..., Cc 13-e asiSe tO}

Multiple Beam-failure-Recovery-Response-CORESETs from multiple TRPs (rTRPs) can be configured to a UE. In addition to extending the message for beam management for a Beamfailure-Recovery-Response-CORESET, multiple Beam-failure-Recovery-ResponseCORESETs from multiple TRPs (rTRPs) can be configured to a UE. Each Beam-failureRecovery-Response-CORESET can correspond to a TRP or a rTRP.

This is shown in Figures 10a and 10b. Figure 10a shows Beam-failure-Recovery-ResponseCORESET from TRP1I Figure 10b shows Beam-failure-Recovery-Response-CORESET from TRP2.

The information in Beam-failure-Recovery-Response-CORESET for TRP 1 contains candidate beams for TRP 2 and vice versa. Hence, if a UE cannot read Beam-failure-RecoveryResponse-CORESET for TRP 1, it can still get candidate beam information from Beam-failureRecovery-Response-CORESET for TRP 2, where a reliable link still exists.

Multiple Beam-failure-Recovery-Response-CORESETs from a single TRP can be configured to a UE. In addition to extending the message for beam management for a Beam-failureRecovery-Response-CORESET, multiple Beam-failure-Recovery-Response-CORESETs can be configured from a single TRP to a UE. Each Beam-failure-Recovery-Response-CORESET can correspond to a TRP or an rTRP. This is shown in Figure 11. When the link between the UE and TRP 2 is about to fail, the UE can access the Beam-failure-Recovery-ResponseCORESETs from TRP1 to acquire candidate beams for TRP 2 link recovery.

In other words, the UE is connected to TRP1 and TRP2 and if one of these links fails, then the UE is still able to determine its recovery options.

In another embodiment, regular CORESETs are configured in addition to Beam-failureRecovery-Response-CORESETs from a single TRP to a UE to restore links from other TRPs. Each Beam-failure-Recovery-Response-CORESET can correspond to a TRP or a rTRP. This is shown in Figure 12. When the link between the UE and TRP 2 is about to fail, the UE can access the regular CORESET from TRP1 to acquire candidate beams for TRP 2 link recovery.

Additionally, these CORESET configurations for link recovery can be used when a UE is using different configurations of physical downlink control channel (PDCCH), physical downlink shared channel (PDSCH), physical uplink control channel (PUCCH), and physical uplink shared channel (PUSCH), as follows:

Configuration 1: Single PDCCH/PDSCH, single PUSCH/PUCCH

In this case, there is only one PDCCH scheduling one PDSCH from multiple TRPs. In such a case, the default CORESET needs to be extended to include multiple candidate beam groups and the beams within each group is QCLed. For UE beam reporting, there is only one PUCCH/PUSCH but a UE can switch to a different TRP with existing high quality links for reporting.

Configuration 2: Multiple PDCCH/PDSCH. single PUSCH/PUCCH

In this case, there are multiple PDCCH, each scheduling one PDSCH from multiple TRPs.

Once beam/link failure is detected, the information of candidate beams for TRP 2 can be found in the Beam-failure-Recovery-Response-CORESET from TRP 1 which is expanded so that a UE can read such information. This is illustrated in Figure 10a.

Alternatively, each TRP can define a separate Beam-failure-Recovery-Response-CORESET for candidate beams for another TRPs, which is illustrated in Figure 11.

In another alternative, once beam/link failure is detected, the information of candidate beams for TRP 2 can be transmitted in CORESET for TRP 1, which is not necessarily the Beamfailure-Recovery-Response-CORESET, so that a UE can read such information dynamically. This is illustrated with Figure 12, which makes use of a regular CORESET.

In all alternatives, the Beam-failure-Recovery-Response-CORESET or the regular CORESET may potentially contain multiple candidate beam groups and the beams within each group are QCLed. For UE beam reporting, there is only one PUCCH/PUSCH, but a UE can switch to a different TRP with existing high quality links for reporting.

Configuration 3: Multiple PDCCH/PDSCH, multiple PUSCH/PUCCH

In this case, there are multiple PDCCHs, each scheduling one PDSCH from multiple TRPs.

The same approaches as shown in Figures 10a and 10b can be applied. However, for UE beam reporting, there is no switching since multiple PUCCH/PUSCH can be used and there are two alternatives for the UE to report measurement results:

• Alternative 1: via the most reliable PUCCH/PUSCH;

• Alternative 2: via the PUCCH/PUSCH of the master cell if possible, otherwise, via the most reliable PUCCH/PUSCH.

A UE determines a QCL beam set quality by averaging the QCL beams inside the set. A UE performs measurements on beams in the list. The reported QCL beam set quality is computed by averaging the beam qualities inside the QCL beam set. The overall UE procedure illustrated in Figure 13.

At S300, the UE commences measurements of beams for the purposes of link recovery.

At S310, it measures beam qualities using cell IDs, if the configuration is as shown in Figure 5

i.e. if there are multiple cell IDs.

At S320. The UE identifies the best beam ID, based on beam quality.

At S330, the UE determines QCL beam set quality on the basis of average beam qualities in that QCL set. In Figure 5, one QCL sets are composed of beams 1 to 8, 9 to 12 and 13 to 16 respectively.

At S340. The UE reports the best beam ID and best QCL beam set to the TRP.

At S350, a check is performed to determine if a RACH configuration for another cell has been received. If so, at S370, an access procedure is performed for the other cell. If not, at S370, the UE monitors a beam recovery CORESET.

When a UE is configured with multiple Beam-failure-Recovery-Response-CORESETs or regular CORESETs for link recovery, and a link failure is about to happen (the link quality of a beam falls below a certain threshold), the UE first optionally checks the Beam-failureRecovery-Response-CORESET configured by the TRP with the failing link. The UE checks Beam-failure-Recovery-Response-CORESETs or regular CORESETs configured by the TRPs with the reliable links to restore the failing link.

From a general recovery procedure perspective, a UE has multiple choices. One is to follow the original procedure and check the Beam-failure-Recovery-Response-CORESET for candidate beams of TRP 1 if its links/beams with TRP 1 fails. When it is not possible, the UE then checks the Beam-failure-Recovery-Response-CORESET or regular CORESETs of another TRP, e.g., TRP 2, with reliable connection so that the link/beam failure recovery and beam reporting are still possible in such a case.

Another choice is not to check the Beam-failure-Recovery-Response-CORESET for candidate beams of TRP 1 if its links/beams with TRP 1 fails but instead check the Beam-failureRecovery-Response-CORESET or regular CORESETs of TRP 2 with reliable connection directly to further reduce beam/link recovery latency.

Figure 14 illustrates how the TRP 320 is able to calculate possible candidate beams for the UE 310. It does this based on the TRP beam for the UE and the rTRP beam for backhaul. In an IAB network, the TRP has knowledge of its best beams for the UE access link. Also, the TRP has knowledge of the best backhaul links from the rTRP, which are optimal backhauling beams associated to the best beams for the UE access link. The, the TRP can use these backhauling beams as candidate beams for the UE.

For instance,, the TRP 320 uses beam 1 and beam 2 for an access link to the UE 310. Also, the TRP 320 has information regarding the backhauling beams of both rTRP1 330 and rTRP2 340. For the backhauling between rTRP1 330 and the TRP 320, rTRPTs backhauling beams are beam 10 and beam 11 and the TRP’s backhauling beams are beam 3, beam 4 and beam 5.

For the backhauling between rTRP2 340 and the TRP 320, rTRP2’s backhauling beams are beam 13, beam 15 an beam 16, and the TRP’s backhauling beams are beam 1, beam 2 and beam 8.

Based on this information, the TRP 320 is able to infer that rTRP2’s backhauling beams (beam 13, beam 15 and beam 16) have the highest probability to provide reliable access links to the UE 310. Therefore, the TRP 320 will list beam13, beam15 and beam 16 as candidate rTRP beams for the UE.

Figure 15 illustrates the estimation process. Details of rTRP backhauling beams are input to the process, along with details of TRP access beams for the UE. The estimation process considers these inputs and, as asset out above, determines which beams are suitable candidates as access beams for the UE.

The activation and deactivation of beam sets can be performed via one or more of RRC signalling, MAC CE, and DCI. When candidate beam sets are configured, TRPs can dynamically activate and deactivate certain beam sets in Beam-failure-Recovery-ResponseCORESETs according to network load and channel conditions. This can be achieved via RRC signalling and/or medium access control layer (MAC) control element (CE) and/or downlink control information (DCI). The choice of the method(s) used depends on overhead and practical considerations. The following alternatives can be considered in a particular case:

Alternative 1: RRC configures multiple beam groups for a UE; MAC CE indicates a subset of beam groups for a UE; and DCI activates some beam groups from the subset dynamically.

Alternative 2: RRC configures multiple beam groups for a UE; and DCI activates some beam groups dynamically.

Alternative 3: DCI activates some beam groups dynamically.

Each alternative has its own advantages and disadvantages. For example, Alternative 1 has the minimum DCI signalling overhead but is not as dynamic and Alternative 3, which has the maximum DCI signalling overhead.

At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as ‘component’, ‘module’ or ‘unit’ used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term “comprising” or “comprises” means including the component(s) specified but not to the exclusion of the presence of others.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All ofthe features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, ofthe steps of any method or process so disclosed.

Claims (12)

1. A method of beam management in a telecommunication system comprising a User Equipment, UE, and a transception point, TRP, comprising the steps of:

the TRP providing the UE with details of candidate beams, arranged in one or more sets of quasi-co-located, QCL, beams;

the UE periodically performing measurements of the candidate beams;

the UE sensing likely failure of a current beam and triggering a link recovery procedure whereby the UE signals the TRP with details of the best of the candidate beams and the best of the sets;

the TRP messaging, via backhaul, a relay TRP, rTRP, associated with the best of the candidate beams or the best of the sets;

the UE monitoring a control resource set, CORESET, and then establishing communication with the relay TRP.

2. The method as claimed in claim 1 wherein if the rTRP is a L1/L2 rTRP, the step of establishing communication with it comprises the rTRP sending a control channel.

3. The method of claim 2 wherein the control channel is a PDCCH.

4. The method of claim 1 wherein if the rTRP is a L3 rTRP, the step of establishing communication with it comprises a RACH procedure between the TRP and the UE and a RRC connection procedure between the rTRP and the UE.

5. The method of any preceding claim wherein if one or more of the candidate beams are associated with a L3 relay TRP, then the TRP additionally provides the UE with details of the cell ID associated with the L3 rTRP.

6. The method of any preceding claim wherein the step of the UE sensing likely failure of a current beam comprises the UE sensing the current beam power falling below a predefined threshold.

7. The method of any preceding claim wherein the best of the sets is determined on the basis of average beam qualities in a particular set.

8. The method of any preceding claim wherein the step of the TRP providing the UE with details of candidate beams, the TRP determines the candidate beams on the basis of knowledge of a beam used for backhaul and a TRP access beams presently used to contact the UE.

9. A TRP operable to determine candidate beams, arranged in one or more sets of quasico-located, QCL, beams, and to forward details of the candidate beams to a UE, the TRP being further operable to receive from the UE, in the event of the UE triggering a link recovery procedure, details of the best of the candidate beams and the best of the sets and being further operable to message, via backhaul, a relay TRP, rTRP, associated with the best of the candidate beams or the best of the sets.

10. A UE operable to:

receive from a TRP details of candidate beams, arranged in one or more sets of quasi-colocated, QCL, beams;

periodically perform measurements of the candidate beams;

sense likely failure of a current beam and trigger a link recovery procedure whereby the UE is operable to signal the TRP with details of the best of the candidate beams and the best of the sets;

monitor a control resource set, CORESET, and then establish communication with the relay TRP.

11. A communication system operable to perform the method of any one of claims 1 to 8.

12. A communication system comprising the TRP of claim 9 and the UE of claim 10.