Apparatuses and methods for LTM with group-based beam reporting

Abstract

Example embodiments provide a handover procedure enhanced with group-based beam reporting for multiple transmission and reception point operation Apparatuses, methods, and computer programs are disclosed.

Description

APPARATUSES AND METHODS FOR LTM WITH GROUP-BASED BEAMREPORTINGTECHNICAL FIELD

[0001] The present application generally relates to information technology. Some example embodiments of the present application relate to providing an enhanced lower layer triggered mobility procedure with group-based beam reporting.BACKGROUND

[0002] Multiple transmission and reception point (multi-TRP or m-TRP) functionality enables a user equipment (UE), to maintain multiple links with multiple transmission and reception points. A user equipment, which is in multiple transmission and reception operation in serving cells, can be transferred to a target cell using a handover procedure, such as a baseline handover, a lower layer (layer 1 / layer 2) triggered mobility and other handover procedures. After the handover, the UE may need to be reconfigured to establish the multiple transmission and reception point operation with the target cell.SUMMARY

[0003] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0004] Example embodiments may enable reducing interruptions in m-TRP operations due to, for example, LTM mobility in a communication network. This may be achieved by the features of the independent claims. Further implementation forms are provided in the dependent claims, the description, and the drawings.

[0005] According to a first aspect, an apparatus of a source network node is provided. The apparatus may comprise at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to transmit, to a target network node of a target cell, a handover request including a group-based beam report, GBBR, received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the targetcell; receive, from the target network node, a handover acknowledgement including information for configuration of multiple transmission reception point operation; and transmit, to the UE, a handover command indicating a handover to the target network node, the handover command including the information for configuration of the multiple transmission reception point operation with the target cell.

[0006] According to an example embodiment of the first aspect, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: transmit, to the target network node prior to the handover request, a configuration request including capability information of the UE, the capability information indicating that the UE supports m-TRP operation; receive, from the target network node, a response to the configuration request, the response including an indication of channel measurement resource sets of the multiple transmission reception points in the target cell; forward the indication of the channel measurement resource sets to the UE to be used for the group-based beam report; and receive, from the UE in response to the forwarded indication of channel measurement resource sets and prior to the handover request, the group-based beam report of measurements corresponding to the indicated channel measurement resource sets of the multiple transmission reception points.

[0007] According to an example embodiment of the first aspect, the handover acknowledgement received from the target network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, configuration information, TCI states assigned for the UE, an indication of time period for validity of the TCI states assigned for the UE, or channel measurement resource sets for m-TRP operation with the target cell.

[0008] According to an example embodiment of the first aspect, at least one of the TCI configuration information or the TCI states included in the handover acknowledgement is based on the group-based beam report received from the UE.

[0009] According to an example embodiment of the first aspect, the apparatus is further configured to determine TCI states of the target network node based on the received information for configuration of the m-TRP operation; and transmit, to the UE, a cell switch command including the determined TCI states.

[0010] According to an example embodiment of the first aspect, the cell switch command is transmitted in a medium access control control element message.

[0011] According to an example embodiment of the first aspect, the handover acknowledgement is received from the target network node in a target to node transparent container.

[0012] According to an example embodiment of the first aspect, transmission of the handover request and reception of the handover acknowledgement are based on a Xn-based handover procedure.

[0013] According to an example embodiment of the first aspect, transmission of the handover command to the UE is based on a Ng-based handover procedure.

[0014] According to a second aspect, an apparatus of a target network node is provided. The apparatus may comprise at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to receive, from a source network node of a source cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell; transmit, to the source network node, a handover acknowledgement including information for configuration of multiple transmission reception point, m-TRP, operation; and establish a connection with the UE based on a handover performed by the UE from the source network node to the target network node such that the UE activates m-TRP operation according to the information for configuration of the m-TRP operation.

[0015] According to an example embodiment of the second aspect, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: receive, from the source network node prior to the handover request, a configuration request including capability information of user equipment, UE, the capability information indicating that the UE supports m-TRP operation; transmit, to the source network node, a response to the configuration request, the response including an indication of the channel measurement resource sets for the multiple transmission reception points in the target cell.

[0016] According to an example embodiment of the second aspect, the handover acknowledgement transmitted to the source network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, configuration information, TCI states assigned for the UE, anindication of a time period for validity of the TCI states assigned for the UE, or channel measurement resources for m-TRP operation with the target cell.

[0017] According to an example embodiment of the second aspect, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: generate at least one of the TCI configuration information or the TCI states based on the group-based beam report received from the source network node in the handover request.

[0018] According to an example embodiment of the second aspect, the handover request is received by the target network node and the handover request acknowledgement is transmitted by the target network node according to Xn-based handover procedure.

[0019] According to a third aspect, an apparatus for user equipment of a communication network is provided. The apparatus may comprise at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to transmit, to a source network node of a source cell, a group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in a target cell; receive, from the source network node, a handover command including information for configuration of multiple transmission reception point, m-TRP, operation in the target cell; and perform, with a target network node in the target cell, a handover to the target network node from the source network node such that the UE activates m-TRP operation with the target cell according to the information for configuration of m-TRP operation.

[0020] According to an example embodiment of the third aspect, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: receive, from the source network node, a request including an indication of the channel measurement resource sets for the multiple transmission reception points in the target cell; and transmit the group-based beam report to the source network node in response to the request.

[0021] According to an example embodiment of the third aspect, the handover command received from the source network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, state configuration information, TCI states assigned for the UE,an indication of a time period for validity of the TCI states assigned for the UE, or channel measurement resource sets for m-TRP operation with the target cell.

[0022] According to an example embodiment of the third aspect, at least one of the TCI configuration information or the TCI states included in the information for configuration of m-TRP operation is based on the group-based beam report transmitted to the source network node.

[0023] According to an example embodiment of the third aspect, the apparatus is further configured to: receive, from the source network node, a cell switch command including TCI states of the target network node assigned by the source network node for the UE based on the information for configuration of m-TRP operation with the target cell; and perform the handover to the target network node from the source network node such that the m-TRP operation is activated by the UE based on the assigned TCI states.

[0024] According to a fourth aspect, a method may comprise transmitting, by a source network node of a source cell to a target network node of a target cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell; receiving, by the source network node from the target network node, a handover acknowledgement including information for configuration of multiple transmission reception point operation; and transmitting, by the source network node to the UE, a handover command indicating a handover to the target network node, the handover command including the information for configuration of the multiple transmission reception point operation with the target cell.

[0025] According to an example embodiment of the fourth aspect, the method comprises transmitting, by the source network node to the target network node prior to the handover request, a configuration request including capability information of the UE, the capability information indicating that the UE supports m-TRP operation; receiving, by the source network node from the target network node, a response to the configuration request, the response including an indication of channel measurement resource sets of the multiple transmission reception points in the target cell; forwarding the indication of the channel measurement resource sets to the UE to be used for the group-based beam report; and receiving, by the source network node from the UE in response to the forwarded indication of channel measurement resource sets and prior to the handover request, the group-based beamreport of measurements corresponding to the indicated channel measurement resource sets of the multiple transmission reception points.

[0026] According to an example embodiment of the fourth aspect, the handover acknowledgement received from the target network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, configuration information, TCI states assigned for the UE, an indication of time period for validity of the TCI states assigned for the UE, or channel measurement resource sets for m-TRP operation with the target cell.

[0027] According to an example embodiment of the fourth aspect, at least one of the TCI configuration information or the TCI states included in the handover acknowledgement are based on the group-based beam report received from the UE.

[0028] According to an example embodiment of the fourth aspect, the method further comprises determining, by the source network node, TCI states of the target network node based on the received information for configuration of the m-TRP operation; and transmitting, by the source network node to the UE, a cell switch command including the determined TCI states.

[0029] According to an example embodiment of the fourth aspect, the handover acknowledgement is received from the target network node in a target to node transparent container.

[0030] According to an example embodiment of the fourth aspect, transmission of the handover request and reception of the handover acknowledgement are based on a Xn-based handover procedure.

[0031] According to an example embodiment of the fourth aspect, transmission of the handover command to the UE is based on a Ng-based handover procedure.

[0032] According to a fifth aspect, a method may comprise receiving, by a target network node of a target cell from a source network node of a source cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell; transmitting, by the target network node to the source network node, a handover acknowledgement including information for configuration of multiple transmission reception point, m-TRP, operation; and establishing, by the target network node, a connection with the UE based on a handover performed by theUE from the source network node to the target network node such that the UE activates m- TRP operation according to the information for configuration of the m-TRP operation.

[0033] According to an example embodiment of the fifth aspect, the method comprises receiving, by the target network node from the source network node prior to the handover request, a configuration request including capability information of user equipment, UE, the capability information indicating that the UE supports m-TRP operation; transmitting, by the target network node to the source network node, a response to the configuration request, the response including an indication of the channel measurement resource sets for the multiple transmission reception points in the target cell.

[0034] According to an example embodiment of the fifth aspect, the handover acknowledgement transmitted to the source network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, configuration information, TCI states assigned for the UE, an indication of a time period for validity of the TCI states assigned for the UE, or channel measurement resources for m-TRP operation with the target cell.

[0035] According to an example embodiment of the fifth aspect, the method comprises generating, by the target network node, at least one of the TCI configuration information or the TCI states based on the group-based beam report received from the source network node in the handover request.

[0036] According to an example embodiment of the fifth aspect, the handover request acknowledgment is transmitted in a target to source transparent container.

[0037] According to an example embodiment of the fifth aspect, the handover request is received by the target network node and the handover request acknowledgement is transmitted by the target network node according to Xn-based handover procedure.

[0038] According to a sixth aspect, a method may comprise transmitting, by a user equipment, UE, to a source network node of a source cell, a group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in a target cell; receiving, by the UE from the source network node, a handover command including information for configuration of multiple transmission reception point, m-TRP, operation in the target cell; and performing, by the UE with a target network node in the target cell, a handover to the target network node from the source networknode such that the UE activates m-TRP operation with the target cell according to the information for configuration of m-TRP operation.

[0039] According to an example embodiment of the sixth aspect, the method comprises receiving, from the source network node, a request including an indication of the channel measurement resource sets for the multiple transmission reception points in the target cell; and transmitting the group-based beam report to the source network node in response to the request.

[0040] According to an example embodiment of the sixth aspect, the handover command received from the source network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, state configuration information, TCI states assigned for the UE, an indication of a time period for validity of the TCI states assigned for the UE, or channel measurement resource sets for m-TRP operation with the target cell.

[0041] According to an example embodiment of the sixth aspect, at least one of the TCI configuration information or the TCI states included in the information for configuration of m-TRP operation are based on the group-based beam report transmitted to the source network node.

[0042] According to an example embodiment of the third aspect, the apparatus is further configured to: receive, from the source network node, a cell switch command including TCI states of the target network node assigned by the source network node for the UE based on the information for configuration of m-TRP operation with the target cell; and perform the handover to the target network node from the source network node such that the m-TRP operation is activated by the UE based on the assigned TCI states.

[0043] According to a seventh aspect, an apparatus may comprise means for performing the method of the fourth, fifth or sixth aspect. The apparatus may further comprise means for performing any example embodiment of the method of the fourth, fifth or sixth aspect.

[0044] According to an eight aspect, a computer program, a computer program product, or a (non-transitory) computer-readable medium is disclosed. The computer program, computer program product, or (non-transitory) computer-readable medium may comprise instructions for causing an apparatus to perform at least the method according to the fourth, fifth or sixth aspect. The computer program may further comprise instructions forcausing the apparatus to perform any example embodiment(s) thereof, as provided in the description and / or the claims.

[0045] According to an eighth aspect, an apparatus may comprise means for performing the method according to the fourth, fifth or sixth aspect. The apparatus may further comprise means for performing any example embodiment(s) of the method of the fourth, fifth or sixth aspect, as provided in the description and / or the claims.

[0046] Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings.DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and together with the description help to explain the example embodiments. In the drawings:

[0048] FIG. 1 illustrates an example of a communication network comprising network nodes and one or more client nodes according to an example embodiment.

[0049] FIG. 2 illustrates an example of a m-TRP aware LTM procedure according to an example embodiment;

[0050] FIG. 3 illustrates an example of a m-TRP aware L3 based handover procedure according to an example embodiment;

[0051] FIG. 4 illustrates an example of an apparatus configured to practice one or more example embodiments;

[0052] FIG. 5 illustrates an example of a method for a handover in a communication network according to an example embodiment;

[0053] FIG. 6 illustrates a second example of a method for a handover in a communication network according to an example embodiment;

[0054] FIG. 7 illustrates a third example of a method for a handover in a communication network according to an example embodiment;

[0055] FIG. 8 illustrates an example of a message format for GBBR resource configuration request according to an example embodiment;

[0056] FIG. 9 illustrates an example of a message format for GBBR resource configuration response according to an example embodiment;

[0057] FIG. 10 illustrates an example of a message format for GBBR resource configuration failure according to an example embodiment.

[0058] Like references are used to designate like parts in the accompanying drawings.DETAILED DESCRIPTION

[0059] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present examples may be constructed or utilized. The description sets forth the functions of the example and a possible sequence of operations for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0060] FIG. 1 illustrates an example of a communication network 100 comprising network nodes and one or more client nodes. The communication network may comprise one or more base stations, represented by gNBs 104 and 106. The communication network 100 may further comprise one or more client nodes, which may be also referred to as user nodes or UE. For example, the communication network may comprise a mobile device, such as a UE 102. The UE 102 may communicate with one or more of the base stations via wireless radio channel(s). Communications between UE 102, gNB 104, and gNB 106 may be bidirectional. Hence, any of the devices may be configured to operate as a transmitter and / or a receiver. A base station may comprise one or more transmission and reception points, TRPs, for communication with UEs and other network elements. Transmission by a base station to UE 102 may be called downlink (DL) transmission. Transmission by UE 102 to a base station may be called uplink (UL) transmission.

[0061] The communication network 100 may further comprise one or more core network elements (not shown) such as for example access and mobility management function (AMF) and / or user plane function (UPF). The base stations may be configured to communicate with the core network elements over a communication interface, such as for example a control plane interface or a user plane interface NG-C / U. Base stations may be also called radio access network (RAN) nodes and they may be part of a radio access network between the core network and the UEs. Network elements AMF / UPF and gNB may be referred to as network nodes, network elements or network devices, or generally a network. Although depicted as a single device, a network node may not be a stand-alone device, butfor example a distributed computing system coupled to a remote radio head. In one example, one or more base stations of the communication network 100 may have a split architecture, wherein functions of the base station may be divided into one or more distributed units (gNB- DU or DU) and a control unit (gNB-CU or CU).

[0062] The communication network 100 may be configured for example in accordance with the 5th Generation digital cellular communication network, as defined by the 3rd Generation Partnership Project (3 GPP). In one example, the communication network 100 may operate according to 3GPP 5G-NR (5thgeneration new radio). It is however appreciated that example embodiments presented herein are not limited to this example network and may be applied in any present or future wireless or wired communication networks (e.g., 6G or beyond), or combinations thereof, for example other type of cellular networks, short-range wireless networks, broadcast or multicast networks, or the like.

[0063] The gNBs 104, 106 may be configured to communicate with the UE 102 via one or more cells 108, 110. A cell may be configured to serve the UE at a certain geographical area at a certain radio frequency, or, a range of radio frequencies around a centre frequency of the cell. A UE may receive signals from one or more cells, such as from a serving cell and one or more neighboring cells. A serving cell refers to a specific cell or base station with which a mobile device is currently communicating or has an active connection. The serving cell may be responsible for managing the communication, handling data transfer, and coordinating various aspects of the connection with the mobile device. For example, the gNB 104 may serve UE 102 at the serving cell. A serving cell may be also referred to as a source cell. The gNB at the serving cell may be referred to as a source gNB or a serving gNB. The gNB 106 may be at a neighboring cell. A neighboring cell is any other cell in the communication network that is not the serving cell but is within range and can potentially be connected to by the mobile device. A gNB at a neighboring cell can be referred to as a candidate gNB or a target gNB. A mobile device may continuously monitor signals from neighboring cells to be aware of alternative connections. The information about neighboring cells can be used for various purposes, including optimizing handovers, which is the process of switching the mobile device's connection from one cell to another as the mobile device moves within the communication network 100.

[0064] Communication network 100 may be operated based on a protocol stack comprising a plurality of protocol layers. Example components of the protocol stack comprise layer 1, LI, layer 2, L2, and layer 3, L3, that manage communication between the UE 102,and the network in a wireless communication system. LI, also referred to as the Physical Layer, is responsible for the physical transmission and reception of signals over the air interface, covering processes such as modulation, coding, and signal propagation. L2, or the Data Link Layer, ensures reliable data transfer across the physical link established by LI and includes sub-layers like the Medium Access Control (MAC) layer, the Radio Link Control (RLC) layer, and the Packet Data Convergence Protocol (PDCP) layer. These sub-layers collectively manage data framing, error correction, retransmission, and security, thereby providing a stable link between the UE and the network. L3, the Network Layer, handles higher-level functions such as connection management, routing, and mobility, including the Radio Resource Control (RRC) protocol, which manages handovers between cells, such as the transition from a source cell (e.g., gNB 104) to a target cell (e.g., gNB 106), based on LI or L2 measurements as well as higher-layer decisions. LI and L2 of the protocol stack can be also referred to as lower layers. These layers may work together to ensure efficient, reliable, and adaptive communication across the network.

[0065] As mentioned, a cell may comprise one or more TRPs. TRPs of the same cell may have a common synchronization signal block (SS / PBCH block) which is cell specific. In multi-TRP operation, a serving cell can schedule the UE from two TRPs. With multi-TRP operation, 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, can be provided for the UE.

[0066] There can be two different operation modes to schedule multi-TRP PDSCH transmissions: single-DCI and multi-DCI. For both operation modes, control of uplink and downlink operation can be done by the physical layer and the MAC layer, within the configuration provided by the RRC layer. In single-DCI mode, or s-DCI, the UE can be scheduled by the same DCI for both TRPs. In multi-DCI mode, or m-DCI, the UE can be scheduled by independent DCIs from each TRP. Furthermore, s-DCI and m-DCI are independent capabilities. This means, that a UE may either support any one of s-DCI or m- DCI, or both capabilities, depending on implementation of the UE.

[0067] In 3GPP 5G NR, frequency range 2, FR2, bands have relatively huge bandwidths which can serve 5G NR use cases requiring higher data rates. However, these bands are also subject to challenging propagating conditions, such as high path loss, absorption from the environment, penetration losses, and the like. Beam management procedures provide one option to alleviate these drawbacks. Beam management refers to a setof procedures to assist UE to set receive and transmit beams of the UE for downlink and uplink transmissions, respectively. NR supports a hierarchical beam-based approach with the SSB beam being a root beam for other beam types, such as channel state information reference signal, CSI-RS, beams.

[0068] Quasi co-location, QCL, framework can be used for beam indication. Beam indication information can be provided by a gNB to a UE. The beam indication information configures the UE with information which transmit, Tx, beam is to be used for downlink and which Tx beam is to be used for uplink. Thus, the UE can select proper receive, Rx, beam and such that Tx beam of the UE is directed towards Rx beam used at the gNB.

[0069] For example, a UE can be configured with a list of up to M transmission configuration indicator, TCI, state configurations within a higher layer parameter PDSCH configuration to decode PDSCH according to a detected PDCCH with downlink control information, DCI, intended for the UE and the given serving cell. The value of M may depend on the UE capability, such as a maximum number of configured TCI states per component carrier.

[0070] Each TCI-state can contain parameters for configuring a quasi -co-location relationship between one or two downlink reference signals and demodulation reference signal, DMRS, ports of the PDSCH, DMRS port of PDCCH or CSI-RS port(s) of a CSI-RS resource. The quasi -co-location relationship can be configured, for example, by a higher layer parameter qcl-Typel for the first DL RS, and qcl-Type2 for the second DL RS (if configured). For the case of two DL RSs, the QCL types may not be the same, regardless of whether the references are to the same DL RS or different DL RSs.

[0071] The quasi -co-location types corresponding to each DL RS may be given by a higher layer parameter QCL type in QCL information and may take one of the following values:QCL types A: Doppler shift, Doppler spread, average delay, delay spread;QCL types B: Doppler shift, Doppler spread;QCL types C: average delay, Doppler shift;QCL types D: Spatial Rx.

[0072] As mentioned, one tool for beam indication for downlink is the TCI framework. A UE can be configured with up to 128 TCI states. The gNB can configure the UE via RRC signalling with TCI states where each TCI state may have one or two source RSs that provide QCL parameters for the target RS. One of the RSs can provide QCL type D per TCI state. ADL TCI chain consists of an SSB, and one or more CSI-RS resources. Further, the TCI state of each reference signal includes another reference signal in the same TCI chain, where the SSB can be associated with serving cell physical cell identifier, PCID, or associated with a PCID different from serving cell PCID.

[0073] DMRS of PDCCH or PDSCH is quasi co-located with the reference signal in its active TCI state. Any other reference signal can be quasi co-located, based on the criteria for DL TCI chain, with the reference signal in the active TCI state.

[0074] Group-based beam reporting, GBBR, may be used as a prerequisite for multi- Rx reception. In group-based beam reporting, the UE reports N groups / pairs (e.g., beams that can be simultaneously received) of X beams (e.g., at least two beams in one group). The pairing can be done by the UE according to its capabilities. In one example, the UE can be configured to select a best beam pair from configured channel measurement resource, CMR, sets based on Ll-RSRP measurements for the group-based beam reporting.

[0075] NR supports different types of handover. The network can control UE mobility based on UE measurement reporting. In one example, a serving cell change can be triggered by L3 measurements and is usually done by RRC signaling. For example, a source gNB can trigger handover by sending handover request to a target gNB and after receiving acknowledgement from the target gNB, the source gNB initiates handover by sending a handover command with target cell configuration to the UE. In response to the handover command, the UE accesses the target cell after applying the received target cell configuration.

[0076] In another example, a handover can be triggered based on an LTM procedure. LTM refers to lower layer (L1 / L2) triggered mobility. More specifically, LTM is a cell switch procedure, where a source cell of a UE is switched by the network by sending an LTM cell switch command. In an LTM procedure, a UE, e.g., the UE 102, may first send a message comprising a measurement report (e.g., LI measurements) to a gNB of the source cell, such as gNB 104. The gNB 104 may then decide, based on the measurement report, to configure LTM and initiates LTM candidate preparation. The gNB 104 can then transmit, to the UE 102, an RRC reconfiguration message including LTM candidate configurations. The UE 102 may store the LTM candidate configurations and transmit a response to the gNB 104, e.g., RRC reconfiguration complete message. The UE 102 may perform DL synchronization with one or more candidate cells, such as gNB 106, based on the LTM candidate configurations before receiving the cell switch command.

[0077] When UE-based timing advance, TA, measurement is configured, the UE 102 can acquire the TA value(s) of the one or more candidate cells by performing the TA measurement. The UE 102 can perform early TA acquisition with the candidate cell(s) as requested by the network before receiving the cell switch command. The early TA acquisition can be done, for example, via contention-free random access, CFRA, triggered by a PDCCH order from the source cell, following which the UE 102 sends a preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the UE 102 may not receive random access response from the network for the purpose of TA value acquisition. The TA value of the candidate cell can be indicated in the cell switch command. Further, the UE 102 may rely on network implementation to guarantee the TA validity. Therefore, the UE 102 may not need to maintain a TA timer for the candidate cell.

[0078] Execution of the LTM cell switch may be initiated after the UE 102 performs measurements, e.g., LI measurements, on the configured one or more candidate cells and transmits LI measurement reports to the gNB 104. The UE 102 may be configured to perform the LI measurements as long as the received RRC reconfiguration is applicable. Based on the measurement reports, the gNB 104 may decide to execute cell switch to a target cell (e.g., one of the candidate cells, such as the gNB 106) and transmits a trigger to the UE 102 for the cell switch. The trigger may comprise, for example, a medium access control control element, MAC CE, including candidate configuration index of the target cell. The UE 102 then switches to the target cell. During the cell switch, the UE 102 may detach from the source gNB 104 and apply the configuration indicated by the candidate configuration index.

[0079] The UE 102 may be configured to perform a random access channel, RACH, procedure towards the target cell, if the UE 102 does not have valid TA of the target cell. The UE 102 may compete the LTM cell switch procedure by sending a RRC reconfiguration complete message to the target cell. If the UE 102 performed the RACH procedure, the UE 102 can consider that the LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE 102 can consider that the LTM cell switch execution is successfully completed when the UE 102 determines that the network has successfully received first UL data from the UE 102.

[0080] The LTM cell switch execution procedure can be performed multiple times for subsequent LTM using the LTM candidate configurations provided by the network during LTM preparation. The LTM procedure is applicable for both intra-gNB-DU LTM and inter-gNB-DU LTM. LTM procedures can be performed, for example, over the air interface or over Fl-C interface.

[0081] After LTM cell switch in the example LTM procedure, UE that was in multi- TRP mode of operation with the source cell may fall back to single TRP, s-TRP, mode of operation. Therefore, the UE would need to perform a sequence of steps to establish multi- TRP operation with the target cell the UE was handed over to.

[0082] For example, the UE may be initially receiving reference signals from TRP1 and TRP2 of the source gNB. Based on the measurement report sent by the UE, the LTM procedure may be initiated, and the LTM procedure may be completed, for example, post RACH procedure. To establish the multi-TRP mode of operation after the UE is handed over to the target TRP via the LTM procedure, overhead signalling exchange may be needed to be performed between the UE and the target cell.

[0083] For example, a target TRP1 of the target cell (now serving / source cell) may first provide CSI measurement configuration to the UE in a RRC reconfiguration message. The UE can then acknowledge acceptance of the CSI measurement configuration using a RRC reconfiguration complete message.

[0084] The UE can perform GBBR measurement on CSLRS provided in the CSI measurement configuration and report the beams the UE can receive simultaneously to the new source gNB via CSI report. The new source gNB can then assign TCI states based on the CSI report sent by the UE and the multi-TRP mode of operation starts in the TRPs that the UE has been handed over to.

[0085] The message exchange and time needed for establishing the multi-TRP mode of operation after the LMT procedure in the above example causes disruption in the multi- TRP mode of operation. This means, that every time a UE which is in multi-TRP mode of operation undergoes an LTM procedure, the following sequency of events can take place: the UE falls back to s-TRP mode of operation, the UE will be reconfigured for multi-TRP once the LTM is complete, the UE will send a CSI report about the multiple TRPs the UE can receive from the cell the UE has moved to, and based on the CSI report, the network can start the multi-TRP operation. Especially in cases where the UE is constantly on the move, the disruptions can make the multi-TRP feature infeasible.

[0086] An objective of this disclosure is to reduce the signaling overhead and have decreased disruption time for multi-TRP operation in mobility scenarios, such as when the UE experiences lower layer triggered mobility.

[0087] In one example, the interruptions in multi-TRP mode of operation of a UE can be reduced by introducing a L3 (e.g., Xn application protocol, XnAP) procedure with message exchange between the serving cells and the target cells for example, when an event A2 occurs in the serving cells. A2 event occurs when a measurement of a signal received from the serving cell fall below a threshold. The message exchange can contain transmission of the CMR sets of the target cells, which enables the UE to measure and send GBBR reports of the target cells to the serving cell.

[0088] Further, an enhanced handover request message is provided, wherein the handover request message for target cell comprises the GBBR report of the target cell received by the serving cell from the UE. In one example, an enhanced handover request acknowledgement message is provided, the message comprising multi-TRP information of the target cell. The multi-TRP information may comprise, for example, configuration of TCI states and / or CRM resource set information. In one example, a RRC reconfiguration message may be transmitted by the serving cell to the UE with a handover command containing the multi-TRP information of the target cell such as CMR resource sets.

[0089] The disclosed message exchange with the enhanced messages may reduce the disruption time in multi-TRP operation, thus enabling faster activation of multi-TRP operations in the target cell once the UE, which was already in multi-TRP mode of operation prior to LTM, completes the mobility procedure.

[0090] FIG. 2 illustrates an example of a m-TRP aware LTM procedure according to an example embodiment. The procedure may be implemented by a UE, such as the UE 102, a gNB of a source cell, such as gNB 104, and a gNB of a target cell, such as gNB 106. The source cell is represented by a first source TRP (TRP1) 200 and a second source TRP (TRP2) 202. The target cell is represented by a first target TRP (TRP1) 204 and a second target TRP (TRP2) 206.

[0091] At operation 208, the UE 102 may be in a RCC connected state and m-TRP mode of operation is enabled between the UE 102 and the source cell.

[0092] With the multi-TRP mode of operation being enabled, the UE 102 may simultaneously receive and measure reference signals of the first source TRP 200, at operation 210, and the second source TRP 202, at operation 212.

[0093] At operation 214, the UE 102 may transmit a measurement report to the source cell, such as to the first source TRP 200. The measurement report may comprise an indicationof a deterioration in measurements of the source cell. The measurement report may be, for example, A2 measurement report.

[0094] At operation 216, the first source TRP 200 may send a message to the target cell, e.g., to the first target TRP 204, based on the received measurement report. The message may comprise a request for GBBR resource configuration. The request for GBBR resource configuration may comprise an indication of capabilities of the UE 102 for m-TRP operation. For example, the request can comprise an indication that the UE 102 supports at least one of multi -DCI or single-DCI. The source cell may be configured to check whether the UE 102 has capabilities for the m-TRP operation and / or that the UE 102 is on m-TRP mode of operation before transmitting the request for GBBR resources. Hence, the resources may be allocated when needed.

[0095] An example of a message format 800 of the request for GBBR resource configuration is illustrated in FIG. 8. In FIG. 8, first column shows example information element, IE, and / or group names 802 to be included in the message. The GBBR resource configuration request message may comprise, for example, the following IES:812: Message type, which denotes an identity of the message;814: Source NG-RAN node UE XnAP ID reference, which is a source NG-RAN node UE identifier over the Xn interface;816: Target NG-RAN node UE XnAP ID, which is a target NG-RAN node UE identifier over the Xn interface;818: Cause, indicating a reason the message is sent / received, for example, as listed in section 9.2.3.2 of 3GPP technical specification TS 38.423;820: Target Cell Global ID, which is the target cell global identity;822: ue-Capabilitylnfo, which provides the UE capability information, for example, as defined in section 6.3.3 of 3GPP TS 38.331824: Csi-MeasConfig, which provides a CSI measurement configuration information to be provided to UE.Further, a second column of FIG. 8 shows presence information 804 for the respective IE in the message, wherein “M” denotes mandatory. A third column of the message format 800 defines semantics description 806, which provides description of the lE / group name. For example, the semantics description 806 may indicate that the source NG-RAN node UE XnAP ID 814 is allocated at the source NG-RAN node (e.g., the first source TRP 200), and that the target NG-RAN node UE XnAP ID 816 is allocated at the target NG-RAN node (e.g., the firsttarget TRP 204). A fifth column of the message format 800 defines assigned criticality 810 (e.g., reject or ignore) of the IE, which provides description of the criticality 808 of the IE. For example, if certain IE (e.g., the target NG-RAN node UE XnAP ID) presented in the message format 800 is not present within the respective message, then based on the assigned criticality (e.g., ignore), the message is handled.

[0096] At operation 218, the first target TRP 204 may respond to the first source TRP 200 with the requested GBBR resource configuration. The response may comprise, for example, UE specific CSI based CMR sets. In the CMR sets, each resource may belong to a different TRP of the target cell.

[0097] An example of a message format 900 for the response to the GBBR resource configuration request is illustrated in FIG. 9. As shown on the first column, the lE / group names 802 may comprise the message type 812, the source NG-RAN node UE XnAP ID reference 814, the target NG-RAN node UE XnAP ID 816 and the cause 818, as described in FIG.8. Further, the message format 900 for GBBR resource configuration request may comprise information about the presence 804, semantics description 806, criticality 808 and assigned criticality 810 for each IE, as described in FIG. 8.

[0098] However, if the target cell fails to provide the requested configuration information, the first target TRP 204 can respond to the first source TPR 200 with a GBBR resource configuration failure message. An example of a message format 1000 for the failure message is illustrated in FIG. 10. Here, the lE / group names 802 included in the message may comprise the message type 812, the source NG-RAN node UE XnAP ID reference 814, the cause 818, the UE capability information 822, and further target cell global ID 1002, which defines the global identifier of the target cell. For example, the target cell global ID may include an E-UTRA cell global identity, CGI, or NR GCI. The message format 1000 may further comprise, for each IE, the presence information 804, semantics description 806, criticality 808, and assigned criticality 810, as in FIG. 8 and FIG. 9. However, here the semantics description 806 of the UE capability information 822 may comprise an IE for UE capability RAT container list supported by the UE, for example, as defined in section 6.3.3 of 3GPP TS 38.331.

[0099] The message formats 800, 900 and / or 1000 may further define other information, such as an IE type and reference to an information source (e.g., a technical specification of a protocol), where the detailed description of the IE can be found (e.g., a section in 3GPP TS 38.423). However, the illustrated message structures are only oneexample, and the messages can also include more or less IES, and with different contents of the IEs applicable to the disclosed procedure, than illustrated in FIG.8, FIG.9 and / or FIG. 1000.

[0100] At operation 220, the first source TRP 200 may reconfigure the UE 102 with the CMR set information received from the first target TRP 204. The reconfiguration may be performed, for example, with a transmission of a RRC reconfiguration message with the received UE specific CSI based CMR sets.

[0101] At operation 222, the UE 102 can be configured to respond to the first source TRP 200, for example, with RRC reconfiguration complete message.

[0102] At operation 224, the UE 102 transmits GBBR report of the target cell to the first source TRP 200. The GBBR report may comprise measurements of neighboring cells performed by the UE 102 based on the configured CMR sets.

[0103] At operation 226, the source cell may initiate m-TRP aware LTM preparation phase with the target cell. At operation 228, the first source TRP 200 may send a handover request comprising the GBBR report of the target cell, for example, to the first target TRP 204 of the target cell. The GBBR report may be used by the first target TRP 204 to determine dedicated TCI states for multi-TRP operation with the UE 102. At operation 230, the first target TRP 204 and / or second target TRP 206 may generate LTM configuration along with the dedicated TCI states for multi-TRP operation, and perform LTM candidate preparation.

[0104] At operation 232, the first target TRP 204 may send a message with handover request acknowledgement to the first source TRP 200. The message is configured to comprise additional information for configuration of the multi-TRP operation after cell switch. The message may comprise, for example, at least one of the CMR resource sets or the TCI configuration of the target cell to be used by the UE 102 for the multi-TRP operation with the target cell. The TCI configuration may comprise the dedicated TCI states for multi-TRP operation determined by the target cell at operation 230.

[0105] At 234, the first source TRP 200 may send a message indicative of the candidate configurations to the UE 102. The message may be, for example, a RRC connection reconfiguration message. The message may comprise at least some of the information received by the first source TRP 200 from the first target TRP 204 at operation 232, such at the CMR resource sets and / or TCI configuration. The message may comprise a handover command for the UE 102, where the UE 102 can be configured to wait for an explicit cell switch command for the handover to be performed. In one example, the message maycomprise an indication for how long the TCI states assigned for the UE are valid. The UE 102 may be configured with a timer for validity of the received TCI states. In case the timer expires before the UE starts the m-TRP operation in the target cell, the UE 102 can be configured to fall back to single-TRP mode of operation and initiate message exchange with the target cell to enable the m-TRP operation after cell switch. The timer may ensure that RAN4 requirements with respect to TCI state switch for m-TRP are complied with. The RAN4 requirements for TCI state switch command require that the TCI state switch is received within 1280 ms upon the last transmission of a RS resource for beam reporting or measurement for a TCI switch to be considered as known. In one example, the message received at 234 may comprise an indication of time period for validity of the TCI states assigned for the UE, e.g., a trigger for the timer.

[0106] At operation 236, the UE 102 may respond to the message received at operation 234. The UE 102 may respond to the first source TRP 200, for example, with a RRC connection reconfiguration complete message.

[0107] At operation 238, the UE 102 may perform early synchronization with the candidate cell(s) before receiving the cell switch command. For example, at operation 240, the UE 102 may be configured to perform UL / DL synchronization with the candidate cell(s) before the cell switch command and / or early TA acquisition. The early synchronization may be initiated by the network or autonomously by the UE.

[0108] At operation 242, LTM execution procedure may be initiated. At operation 244, the UE 102 may transmit a measurement report to the first source TRP 200. The measurement report may be based on LI measurements performed by the UE 102 on the candidate cell(s). At operation 246, the first source TRP 200 may make an LTM decision based on the received measurement report, that is, decides to execute the cell switch.

[0109] At operation 248, the first source TRP 200 sends the cell switch command to the UE 102. The cell switch command can be enhanced with information configured to enable the m-TRP operation after the cell switch. For example, the cell switch command may be a MAC CE command comprising TCI states of the target cell that the UE 102 will use after the LTM procedure, e.g., TCI states of the first target TRP 204 and the second target TRP 206. The TCI states that the source cell assigns to the UE 102 may be based on the TCI configuration received at 232 from the target cell, e.g., the first target TRP 204. The TCI configuration may comprise multiple TCI states with one-to-one mapping per TRP. The TCI states are then used by the UE 102 to enable the m-TRP operation in the target cell.[001 10] At operation 250, LTM completion phase may be started where the UE switches from the source cell to the target cell. At operation 252, the UE 102 can start m-TRP operation with the TCI states that the UE 102 was assigned by the target cell at operation 232 and provided for the UE 102 at operation 248. During the m-TRP operation at 254, the UE 102 can transmit signals to the first target TRP 204 and / or to the second target TRP 206, as well as receive signals from the first target TRP 204 and / or from the second target TRP 206.[001 1 1 ] The procedure of FIG. 2 illustrates an LTM RACH-less mobility and simultaneous reception in m-TRP mode of operation. However, it is noted that similar procedure can be used for LTM RACH based mobility as well as for non-simultaneous multi- TRP mode of operation.[001 12] FIG. 3 illustrates an example of a m-TRP aware L3 based handover procedure according to an example embodiment. The procedure may be implemented by a UE, such as the UE 102, a gNB of a source cell, such as the gNB 104, and a gNB of a target cell, such as the gNB 106. The source cell is represented by the first source TRP 200 and the second source TRP 202. The target cell is represented by the first target TRP 204 and the second target TRP 206.[001 1 3] Operations 208 to 212 of FIG. 2 and FIG. 3 correspond to each other and are not therefore repeated herein.[001 14] At operation 214, the UE 102 may transmit a measurement report to the source cell, such as to the first source TRP 200. The measurement report may be based, for example, L3 measurements performed by the UE 102. The measurement report may comprise an indication of a deterioration in measurements of the source cell. In response to the measurement report, the source cell may request GBBR resource configuration from the target cell for the UE 102, and receive a GBBR report from the UE based on the GBBR resource configuration, as already described in operations 216 to 224 in FIG. 2, and not therefore repeated herein.[001 1 5] Based on the GBBR report received by the source cell, such as the first source TRP 200, from the UE 102, the m-TRP aware LTM preparation phase is initiated at operation 226. During the LTM preparation phase, the first source TRP 200 may transmit the handover request together with the received GBBR report to the first target TRP 204, at operation 228. In response to the handover request, at operation 230, the first target TRP 204 may perform candidate preparation for handover, and determine CMR sets and / or TCI configurationinformation for m-TRP operation with the UE 102. For example, the first target TRP 204 may be configured to seek and determine dedicated TCI states for the UE 102.[001 16] At operation 232, the first target TRP 204 may respond to the first source TRP 200 with an acknowledgement. The response may comprise at least one of candidate configurations based on the handover request, the CMR sets and / or the TCI configuration information determined at the operation 230. In one example, the response may be transmitted in an information element used to transparently pass radio related information from the handover target to the handover source, e.g., IE TargetToSourceTransparentContainer.[001 1 7] At operation 300, the UE 102 may receive, from the first source TRP 200, a handover command message comprising at least one of the CMR resource sets or the TCI configuration information received from the target cell at operation 232. Here, the handover command may be received with an indication of the handover to be triggered immediately. For example, the handover command may be received in a RRC reconfiguration message including reconfiguration with synchronization.[001 1 8] In one example, the messages for the handover request and the handover request acknowledgement may be transferred in Xn interface based handover resembles. In addition, the source cell (e.g., first source TRP 200) can be configured to transmit a message for handover to the UE 102 (e.g., handover required message or the handover command) in Ng based handover. If the handover is Ng based handover, the source TRP 200 of the serving cell may be communicating with target cell via AMF.[001 1 9] Based on the received handover command message, the UE 102 may decide to detach from the source cell at operation 302, and apply configurations received in the handover command message.[001 20] At operation 304, the UE 102 may perform RACH procedure towards the target cell. At operation 306, the UE 102 may establish m-TRP operation with the target cell based on the TCI configuration information received at operation 300. For example, the UE 102 may be configured to start the m-TRP operation with TCI states assigned by the first target TRP 204 for the UE 102 at operation 232. During the m-TRP operation at 254, the UE 102 can transmit signals to the first target TRP 204 and / or to the second target TRP 206, as well as receive signals from the first target TRP 204 and / or from the second target TRP 206.[001 21 ] FIG. 4 illustrates an example of an apparatus 400 configured to practice one or more example embodiments. The apparatus 400 may comprise a UE such as UE 102, or a base station such as gNB 104 or gNB 106, an access point, a radio network node, a TRP, suchas the first source TRP 200 or the first target TRP1 204, a network device, or in general any apparatus configured to implement functionality described herein.

[0122] The apparatus 400 may comprise at least one processor 402. The at least one processor 402 may comprise, for example, one or more of various processing devices, such as for example a co-processor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.

[0123] The apparatus 400 may further comprise at least one memory 404. The memory 404 may be configured to store, for example, computer program code 406 or the like, for example operating system software and application software. The memory 404 may comprise one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination thereof. For example, the memory 404 may be embodied as magnetic storage devices (such as hard disk drives, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0124] The apparatus 400 may further comprise one or more communication interfaces 408 configured to enable apparatus 400 to transmit and / or receive information, to / from other apparatuses. The communication interface may be configured to provide at least one wireless radio connection, such as for example a 3 GPP mobile broadband connection (e.g. 3G, 4G, 5G, or beyond). However, the communication interface 408 may be configured to provide one or more other type of connections, for example a wireless local area network (WLAN) connection such as for example standardized by IEEE 802.11 series or Wi-Fi alliance; a short range wireless network connection such as for example a Bluetooth, NFC (near-field communication), or RFID connection; a wired connection such as for example a local area network (LAN) connection, a universal serial bus (USB) connection or an optical network connection, or the like; or a wired Internet connection. The communication interface 408 may comprise, or be configured to be coupled to, at least one antenna to transmit and / or receive radio frequency signals. One or more of the various types of connections may be also implemented as separate communication interfaces, which may be coupled or configured to be coupled to a plurality of antennas.

[0125] The apparatus 400 may further comprise a user interface 410 comprising an input device and / or an output device. The input device may take various forms such a keyboard, a touch screen, or one or more embedded control buttons. The output device may for example comprise a display, a speaker, a vibration motor, or the like.

[0126] When the apparatus 400 is configured to implement some functionality, some component and / or components of the apparatus 400, such as for example the at least one processor 402 and / or the memory 404, may be configured to implement this functionality. Furthermore, when the at least one processor 402 is configured to implement some functionality, this functionality may be implemented using program code 406 comprised, for example, in the memory 404.

[0127] The functionality described herein may be performed, at least in part, by one or more computer program product components such as software components. According to an embodiment, the apparatus 400 comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code when executed to execute the embodiments of the operations and functionality described. Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), applicationspecific Integrated Circuits (ASICs), application-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs).

[0128] The apparatus 400 comprises means for performing at least one method described herein. In one example, the means comprises the at least one processor 402, the at least one memory 404 including program code 406 configured to, when executed by the at least one processor 402, cause the apparatus 400 to perform the method.

[0129] The apparatus 400 may comprise for example a computing device such as for example a base station, a network node, a server device, a client node, a mobile phone, a tablet computer, a laptop, or the like. In one example, the apparatus 400 may comprise a vehicle such as for example a car. Although the apparatus 400 is illustrated as a single device it is appreciated that, wherever applicable, functions of apparatus 400 may be distributed to a plurality of devices.[001 30] FIG. 5 illustrates an example of a method for a handover in a communication network according to an example embodiment. The method 500 may be performed by anetwork node of a source cell, or by an apparatus configured to control the functioning thereof, when installed therein.[001 31 ] At operation 502, the method may comprise transmitting, to a target network node of a target cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell.[001 32] At operation 504, the method may comprise receiving, from the target network node, a handover acknowledgement including information for configuration of multiple transmission reception point operation.[001 33] At operation 506, the method may comprise transmitting, to the UE, a handover command indicating a handover to the target network node, the handover command including the information for configuration of the multiple transmission reception point operation with the target cell.[001 34] FIG. 6 illustrates a second example of a method for a handover in a communication network according to an example embodiment. The method 600 may be performed by a network node of a target cell, or by an apparatus configured to control the functioning thereof, when installed therein.[001 35] At operation 602, the method may comprise receiving, from a source network node of a source cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell.[001 36] At operation 604, the method may comprise transmitting, to the source network node, a handover acknowledgement including information for configuration of multiple transmission reception point, m-TRP, operation.[001 37] At operation 606, the method may comprise establishing a connection with the UE based on a handover performed by the UE from the source network node to the target network node such that the UE activates m-TRP operation according to the information for configuration of the m-TRP operation.[001 38] FIG. 7 illustrates a third example of a method for a handover in a communication network according to an example embodiment. The method 700 may beperformed by a user equipment, such as UE 102, or an apparatus configured to control the functioning thereof, when installed therein.[001 39] At operation 702, the method may comprise transmitting, to a source network node of a source cell, a group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in a target cell.

[0140] At operation 704, the method may comprise receiving, from the source network node, a handover command including information for configuration of multiple transmission reception point, m-TRP, operation in the target cell.

[0141] At operation 706, the method may comprise performing, with a target network node in the target cell, a handover to the target network node from the source network node such that the UE activates m-TRP operation with the target cell according to the information for configuration of m-TRP operation.

[0142] Further features of the methods directly result from the functionalities and parameters of the apparatuses, as described in the appended claims and throughout the specification and are therefore not repeated here. It is noted that one or more operations of the method may be performed in different order.

[0143] An apparatus, for example a network node, a base station, a TRP, a user node or a client node, may be configured to perform or cause performance of any aspect of the method(s) described herein. Further, a computer program may comprise instructions for causing, when executed, an apparatus to perform any aspect of the method(s) described herein. Further, an apparatus may comprise means for performing any aspect of the method(s) described herein. According to an example embodiment, the means comprises at least one processor, and memory including program code, the at one memory and the program code configured to, when executed by the at least one processor, cause performance of any aspect of the method(s).

[0144] In legacy handover, a target cell would be prepared based on a L3 based (single TRP) measurement report and UE is transferred to the target cell with single TRP operation. Later, m-TRP operation can be configured and resumed in the legacy handover which causes overhead of addition higher layer signalling and degradation of user data throughput, therefore resulting degradation in user experience. Advantages of the methods include reducing disruption time in resuming m-TRP operation once a UE, which was already in m-TRP mode of operation prior to a handover (e.g., LTM), completes the mobility procedure and is now in the target cell. Further, because candidate preparation is done with a GBBR report that isgenerated considering m-TRP operations and the TCI configurations are provided based on the GBBR report, effectiveness of the procedure is increased because the signaling to resume m-TRP operation is included in the handover signaling (e.g., LTM signaling). The approach provides an efficient way to enable continuity of m-TRP operations during handover from a source cell to a target cell. In the procedure disclosed herein, there is no interaction to target cell / DU between source DU and target DU during LTM switch decision and MAC CE HO command - this may ensure the strict time period of validity of a known TCI state (e.g., 1280 ms). As noted above, a TCI state is considered known as per RAN4 RRM requirements if the UE receives the switch command within 1280 ms of the transmission of the RS resource which was used for sending the LI measurement report.

[0145] Any range or device value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed.

[0146] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0147] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[0148] The operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the effect sought.

[0149] The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.[001 50] As used in this application, the term ‘circuitry’ may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable) :(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (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 (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims.[001 51 ] As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of 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 or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.[001 52] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.

Claims

CLAIMS1. An apparatus of a source network node, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus at least to: transmit, to a target network node of a target cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell; receive, from the target network node, a handover acknowledgement including information for configuration of multiple transmission reception point, m-TRP, operation; and transmit, to the UE, a handover command indicating a handover to the target network node, the handover command including the information for configuration of the multiple transmission reception point operation with the target cell.

2. The apparatus of claim 1, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: transmit, to the target network node prior to the handover request, a configuration request including capability information of the UE, the capability information indicating that the UE supports m-TRP operation; receive, from the target network node, a response to the configuration request, the response including an indication of channel measurement resource sets of the multiple transmission reception points in the target cell; forward the indication of the channel measurement resource sets to the UE to be used for the group-based beam report; and receive, from the UE in response to the forwarded indication of channel measurement resource sets and prior to the handover request, the group-based beam report of measurements corresponding to the indicated channel measurement resource sets of the multiple transmission reception points.

3. The apparatus of any preceding claim, wherein the handover acknowledgementreceived from the target network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, configuration information, TCI states assigned for the UE, an indication of time period for validity of the TCI states assigned for the UE, or channel measurement resource sets for m-TRP operation with the target cell.

4. The apparatus of claim 3, wherein at least one of the TCI configuration information or the TCI states included in the handover acknowledgement are based on the group-based beam report received from the UE.

5. The apparatus of any preceding claim, wherein the apparatus is further configured to: determine TCI states of the target cell for the UE based on the received information for configuration of the m-TRP operation; and transmit, to the UE, a cell switch command including the determined TCI states.

6. An apparatus of a target network node in a target cell, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus at least to: receive, from a source network node of a source cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell; transmit, to the source network node, a handover acknowledgement including information for configuration of multiple transmission reception point, m-TRP, operation; and establish a connection with the UE based on a handover performed by the UE from the source network node to the target network node such that the UE activates m-TRP operation according to the information for configuration of the m-TRP operation.

7. The apparatus of claim 6, wherein the at least one memory and the computerprogram code are configured to, with the at least one processor, cause the apparatus to: receive, from the source network node prior to the handover request, a configuration request including capability information of the UE, the capability information indicating that the UE supports m-TRP operation; transmit, to the source network node, a response to the configuration request, the response including an indication of the channel measurement resource sets for the multiple transmission reception points in the target cell.

8. The apparatus of claim 6 or 7, wherein the handover acknowledgement transmitted to the source network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, configuration information, TCI states assigned for the UE, an indication of a time period for validity of the TCI states assigned for the UE, or channel measurement resources for m-TRP operation with the target cell.

9. The apparatus of claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: generate at least one of the TCI configuration information or the TCI states based on the group-based beam report received from the source network node in the handover request.

10. An apparatus of a user equipment, UE, in a communication network, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus at least to: transmit, to a source network node of a source cell, a group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in a target cell; receive, from the source network node, a handover command including information for configuration of multiple transmission reception point, m-TRP, operation in the target cell; andperform, with a target network node in the target cell, a handover to the target network node from the source network node such that the UE activates m-TRP operation with the target cell according to the information for configuration of m-TRP operation.

11. The apparatus of claim 10, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to: receive, from the source network node, a request including an indication of the channel measurement resource sets for the multiple transmission reception points in the target cell; and transmit the group-based beam report to the source network node in response to the request.

12. The apparatus of claim 10 or 11, wherein the handover command received from the source network node includes layer 3 based handover configuration information or lower layer triggered mobility configuration information, and the information for configuration of m-TRP operation including at least one of transmission configuration indication, TCI, state configuration information, TCI states assigned for the UE, an indication of a time period for validity of the TCI states assigned for the UE, or channel measurement resource sets for m-TRP operation with the target cell.

13. The apparatus of claim 12, wherein at least one of the TCI configuration information or the TCI states included in the information for configuration of m-TRP operation are based on the group-based beam report transmitted to the source network node.

14. The apparatus of any of claims 10 to 13, wherein the apparatus is further configured to: receive, from the source network node, a cell switch command including TCI states of the target cell assigned by the source network node for the UE based on the information for configuration of m-TRP operation with the target cell; and perform the handover to the target network node from the source network node such that the m-TRP operation is activated by the UE based on the assigned TCI states.

15. A method, comprising: transmitting, by a source network node of a source cell to a target network node of atarget cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell; receiving, by the source network node from the target network node, a handover acknowledgement including information for configuration of multiple transmission reception point operation; and transmitting, by the source network node to the UE, a handover command indicating a handover to the target network node, the handover command including the information for configuration of the multiple transmission reception point operation with the target cell.

16. A method, comprising: receiving, by a target network node of a target cell from a source network node of a source cell, a handover request including a group-based beam report received from user equipment, UE, the group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in the target cell; transmitting, by the target network node to the source network node, a handover acknowledgement including information for configuration of multiple transmission reception point, m-TRP, operation; and establishing, by the target network node, a connection with the UE based on a handover performed by the UE from the source network node the target network node such that the UE activates m-TRP operation with the target cell according to the information for configuration of the m-TRP operation.

17. A method, comprising: transmitting, by a user equipment, UE, of a communication network to a source network node of a source cell, a group-based beam report comprising measurements corresponding to channel measurement resource sets of multiple transmission reception points in a target cell; receiving, by the user equipment from the source network node, a handover command including information for configuration of multiple transmission reception point, m-TRP, operation in the target cell; andperforming, by the user equipment with a target network node in the target cell, a handover to the target network node from the source network node such that the UE activates m-TRP operation with the target cell according to the information for configuration of m-TRP operation.

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