Method of RRC configuration structure for inter-CU ltm

Abstract

An apparatus configured to: receive, from a source central unit (CU), a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one group configuration, wherein the at least one group configuration comprises, at least: a delta reference configuration associated with a central unit (CU), wherein the delta reference configuration is defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration is defined based on the reference configuration associated with the CU; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

Description

METHOD OF RRC CONFIGURATION STRUCTURE FOR INTER-CU LTMTECHNICAL FIELD

[0001] The example and non-limiting embodiments relate generally to L1 / L2 triggered mobility (LTM) and, more particularly, to the configurations of target cells during the LTM procedure.BACKGROUND

[0002] It is known, in radio resource control messaging, to provide the user equipment with a reference configuration that is common for all target cells. In the case of LTM between central units, the use of a common reference configuration for all target cells, regardless of which central unit provides each target cell, may result in additional overhead and / or latency.SUMMARY

[0003] The following summary is merely intended to be illustrative. The summary is not intended to limit the scope of the claims .

[0004] In accordance with one aspect, an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one first group configuration, wherein the at least one first group configuration comprises, at least: a first referenceconfiguration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration is defined based on the first reference configuration; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0005] In accordance with one aspect, a method comprising: receiving, with a user equipment from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one first group configuration, wherein the at least one first group configuration comprises, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration is defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration .

[0006] In accordance with one aspect, an apparatus comprising means for: receiving, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one first group configuration, wherein the at least one first group configuration comprises, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least onefirst delta configuration is defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration .

[0007] In accordance with one aspect, a non-transitory computer- readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, with a user equipment from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one first group configuration, wherein the at least one first group configuration comprises, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration is defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration .

[0008] In accordance with one aspect, an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine to cause switching of a serving cell of a user equipment; transmit, to at least one first target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a first group configuration, wherein the first group configuration comprises, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at leastone first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration is defined based on the first reference configuration; receive, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and transmit, to the user equipment, a configuration comprising, at least, the at least one received first group configuration.

[0009] In accordance with one aspect, a method comprising: determining, with a source central unit (CU) , to cause switching of a serving cell of a user equipment; transmitting, to at least one first target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a first group configuration, wherein the first group configuration comprises, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration is defined based on the first reference configuration; receiving, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and transmitting, to the user equipment, a configuration comprising, at least, the at least one received first group configuration.

[0010] In accordance with one aspect, an apparatus comprising means for: determining to cause switching of a serving cell of a user equipment; transmitting, to at least one first target central unit (CU) , a handover request , wherein the handover request comprises, at least, a request for a first group configuration,wherein the first group configuration comprises, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration is defined based on the first reference configuration; receiving, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and transmitting, to the user equipment, a configuration comprising, at least, the at least one received first group configuration.

[0011] In accordance with one aspect, a non-transitory computer- readable medium comprising program instructions stored thereon for performing at least the following: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one first target central unit (CU) , of a handover request, wherein the handover request comprises, at least, a request for a first group configuration, wherein the first group configuration comprises, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration is defined based on the first reference configuration; causing receiving, from respective ones of the at least one first target CU, of at least one first group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration comprising, at least, the at least one received first group configuration .

[0012] In accordance with one aspect, an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration comprising a reference configuration associated with one or more target cells the apparatus provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration is defined based on the reference configuration; generate the group configuration; and transmit, to the source CU, the group configuration .

[0013] In accordance with one aspect, a method comprising: receiving, with a target central unit (CU) from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration comprising a reference configuration associated with one or more target cells the target CU provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration is defined based on the reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration .

[0014] In accordance with one aspect, an apparatus comprising means for: receiving, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration comprising a reference configuration associated with one or more target cellsthe apparatus provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration is defined based on the reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration.

[0015] In accordance with one aspect, a non-transitory computer- readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request comprises, at least, a request for a group configuration comprising a reference configuration associated with one or more target cells a target central unit (CU) provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration is defined based on the reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration.

[0016] In accordance with one aspect, an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one group configuration, wherein the at least one group configuration comprises, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration is defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least onetarget cell that is associated with the CU, wherein the at least one delta configuration is defined based on the reference configuration associated with the CU; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0017] In accordance with one aspect, a method comprising: receiving, with a user equipment, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one group configuration, wherein the at least one group configuration comprises, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration is defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration is defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0018] In accordance with one aspect, an apparatus comprising means for: receiving, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one group configuration, wherein the at least one group configuration comprises, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration is defined based on a reference configuration associated with the CU and a source reference configuration, andat least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration is defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0019] In accordance with one aspect, a non-transitory computer- readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one group configuration, wherein the at least one group configuration comprises, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration is defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration is defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0020] In accordance with one aspect, an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine to cause switching of a serving cell of a user equipment; transmit, to at least one target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a group configuration,wherein the group configuration comprises, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration comprises at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration is defined based on the full reference configuration; receive, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmit, to the user equipment, a configuration comprising, at least, the at least one group configuration .

[0021] In accordance with one aspect, a method comprising: determining, with a source central unit (CU) , to cause switching of a serving cell of a user equipment; transmitting, to at least one target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration comprises at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration is defined based on the full reference configuration; receiving, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmitting, to the user equipment, aconfiguration comprising, at least the at least one group configuration .

[0022] In accordance with one aspect, an apparatus comprising means for: determining to cause switching of a serving cell of a user equipment; transmitting, to at least one target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration comprises at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration is defined based on the full reference configuration; receiving, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmitting, to the user equipment, a configuration comprising, at least, the at least one group configuration .

[0023] In accordance with one aspect, a non-transitory computer- readable medium comprising program instructions stored thereon for performing at least the following: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one target central unit (CU) , of a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configurationcomprises at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration is defined based on the full reference configuration; causing receiving, from respective ones of the at least one target CU, of at least one group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration comprising, at least, the at least one group configuration.

[0024] In accordance with one aspect, an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with the apparatus, wherein the reference configuration comprises at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the apparatus provides, wherein the at least one delta configuration is defined based on the full reference configuration; generate the group configuration; and transmit, to the source CU, the group configuration.

[0025] In accordance with one aspect, a method comprising: receiving, with a target central unit (CU) from a source central unit (CU) serving a user equipment, a handover request, whereinthe handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with the target CU, wherein the reference configuration comprises at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration is defined based on the full reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration.

[0026] In accordance with one aspect, an apparatus comprising means for: receiving, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with the apparatus, wherein the reference configuration comprises at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the apparatus provides, wherein the at least one delta configuration is defined based on the full reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration.

[0027] In accordance with one aspect, a non-transitory computer-readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, from a source central unit (CU) serving a user equipment, of ahandover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with a target central unit (CU) , wherein the reference configuration comprises at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration is defined based on the full reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration.

[0028] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The foregoing aspects and other features are explained in the following description, taken in connection with the accompanying drawings, wherein:

[0030] FIG. 1 is a block diagram of one possible and nonlimiting example system in which the example embodiments may be practiced;

[0031] FIG. 2 is a diagram illustrating features as described herein;

[0032] FIG. 3 is a diagram illustrating features as described herein;

[0033] FIG. 4 is a diagram illustrating features as described herein;

[0034] FIG. 5 is a diagram illustrating features as described herein;

[0035] FIG. 6 is a diagram illustrating features as described herein;

[0036] FIGs. 7A-7D are diagrams illustrating features as described herein;

[0037] FIG. 8 is a diagram illustrating features as described herein;

[0038] FIG. 9 is a diagram illustrating features as described herein;

[0039] FIG. 10 is a diagram illustrating features as described herein;

[0040] FIG. 11 is a diagram illustrating features as described herein;

[0041] FIGs. 12A-12B are diagrams illustrating features as described herein;

[0042] FIGs. 13A-13B are diagrams illustrating features as described herein;

[0043] FIG. 14 is a diagram illustrating features as described herein;

[0044] FIGs. 15A-15B are diagrams illustrating features as described herein;

[0045] FIG. 16 is a diagram illustrating features as described herein;

[0046] FIGs. 17A-17B are diagrams illustrating features as described herein;

[0047] FIG. 18 is a diagramfeatures as described herein;

[0048] FIGs. 19A-19B areillustrating features as described herein;

[0049] FIG. 20 is a diagramfeatures as described herein;

[0050] FIG. 21 is a flowchart illustrating steps as described herein;

[0051] FIG. 22 is a flowchart illustrating steps as described herein;

[0052] FIG. 23 is a flowchart illustrating steps as described herein;

[0053] FIG. 24 is a flowchart illustrating steps as described herein;

[0054] FIG. 25 is a flowchart illustrating steps as described herein; and

[0055] FIG. 26 is a flowchart illustrating steps as described herein .DETAILED DESCRI PTION OF EMBODIMENTS

[0056] The following abbrevi ations that may be found in the speci fication and / or the drawing figures are de fined as follows :3 GPP third generation partnership project5G fifth generation5GC 5G core networkAM acknowledged modeA MF access and mobility management functionAS access stratumCE control elementCFRA contention free random accessCHO conditional handover cRAN cloud radio access networkCU central unitDC dual connectivityDCCH dedicated control channelDL downlinkDU distributed unit eNB (or eNodeB) evolved Node B (e.g., an LTE base station)EN-DC E-UTRA-NR dual connectivity en-gNB or En-gNB node providing NR user plane and control plane protocol terminations towards the UE, and acting as secondary node in EN- DCE-UTRA evolved universal terrestrial radio access, i.e., the LTE radio access technology gNB (or gNodeB) base station for 5G / NR, i.e., a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GCIAB integrated accessIE information elementI / F interfaceLI layer 1LIE long term evolutionLTM Ll / 2 triggered mobilityMAC medium access controlMCG master cell groupMME mobility management entityMN master node ng or NG new generation ng-eNB or NG-eNB new generation eNBNR new radioN / W or NW networkO-RAN open radio access networkPBCH physical broadcast channelPCell primary cell of master cell groupPCI physical cell identityPDCCH physical downlink control channelPDCP packet data convergence protocolPHY physical layerPSCell primary cell of secondary groupRA random accessRACH random access channelRAN radio access networkRB resource blockRF radio frequencyRLC radio link controlRRC radio resource controlRRH remote radio headRS reference signalRU radio unitRx receiverSAP service access pointSCG secondary cell groupSDAP service data adaptation protocolSGW serving gatewaySMF session management functionSN secondary nodeSRB signaling radio bearerSS synchronization signalSSB synchronization signal blockSUL supplementary uplinkTA timing advanceTCI transmission configuration indicatorTx transmitterUE user equipment (e.g., a wireless, typically mobile device)UE uplinkUPF user plane functionVNR virtualized network function

[0057] Tu rning to FIG. 1, this figure shows a block diagram of one possible and non-limiting example in which the examples may be practiced. A user equipment (UE) 110, radio access network (RAN) node 170, and network element (s) 190 are illustrated. In the example of FIG. 1, the user equipment (UE) 110 is in wireless communication with a wireless network 100. A UE is a wireless device that can access the wireless network 100. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected through one or morebuses 127. Each of the one or more transceivers 130 includes a receiver, Rx, 132 and a transmitter, Tx, 133. The one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, and the like. A "circuit" may include dedicated hardware or hardware in association with software executable thereon. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a module 140, comprising one of or both parts 140-1 and / or 140-2, which may be implemented in a number of ways. The module 140 may be implemented in hardware as module 140-1, such as being implemented as part of the one or more processors 120. The module 140-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 140 may be implemented as module 140-2, which is implemented as computer program code 123 and is executed by the one or more processors 120. For instance, the one or more memories 125 and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more of the operations as described herein. The UE 110 communicates with RAN node 170 via a wireless link 111.

[0058] The RAN node 170 in this example is a base station that provides access by wireless devices such as the UE 110 to the wireless network 100. The RAN node 170 may be, for example, a base station for 5G, also called New Radio (NR) . In 5G, the RAN node 170 may be a NG-RAN node, which is defined as either a gNB or a ng-eNB. A gNB is a node providing NR user plane and control plane protocol terminations towards the UE, and connected via theNG interface to a 5GC (such as, for example, the network element (s) 190) . The ng-eNB is a node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC. The NG-RAN node may include multiple gNBs, which may also include a central unit (CU) (gNB-CU) 196 and distributed unit(s) (DUs) (gNB-DUs) , of which DU 195 is shown. Note that the DU may include or be coupled to and control a radio unit (RU) . The gNB-CU is a logical node hosting RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the Fl interface connected with the gNB-DU. The Fl interface is illustrated as reference 198, although reference 198 also illustrates a link between remote elements of the RAN node 170 and centralized elements of the RAN node 170, such as between the gNB-CU 196 and the gNB-DU 195. The gNB-DU is a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU. One gNB-CU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interface 198 connected with the gNB-CU. Note that the DU 195 is considered to include the transceiver 160, e.g. , as part of a RU, but some examples of this may have the transceiver 160 as part of a separate RU, e.g. , under control of and connected to the DU 195. The RAN node 170 may also be an eNB (evolved NodeB) base station, for LTE (long term evolution) , or any other suitable base station, access point, access node, or node .

[0059] The RAN node 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / W I / F(s) ) 161, and one or more transceivers 160 interconnected through one or more buses 157. Each of the one or more transceivers 160includes a receiver, Rx, 162 and a transmitter, Tx, 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. The CU 196 may include the processor (s) 152, memories 155, and network interfaces 161. Note that the DU 195 may also contain its own memory / memories and processor ( s ) , and / or other hardware, but these are not shown.

[0060] The RAN node 170 includes a module 150, comprising one of or both parts 150-1 and / or 150-2, which may be implemented in a number of ways. The module 150 may be implemented in hardware as module 150-1, such as being implemented as part of the one or more processors 152. The module 150-1 may be implemented also as an integrated circuit or through other hardware such as a programmable gate array. In another example, the module 150 may be implemented as module 150-2, which is implemented as computer program code 153 and is executed by the one or more processors 152. For instance, the one or more memories 155 and the computer program code 153 are configured to, with the one or more processors 152, cause the RAN node 170 to perform one or more of the operations as described herein. Note that the functionality of the module 150 may be distributed, such as being distributed between the DU 195 and the CU 196, or be implemented solely in the DU 195.

[0061] The one or more network interfaces 161 communicate over a network such as via the links 176 and 131. Two or more gNBs 170 may communicate using, e.g. , link 176. The link 176 may be wired or wireless or both and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interface for other standards.

[0062] The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optics or other optical communication equipment, wireless channels, and the like. For example, the one or more transceivers 160 may be implemented as a remote radio head (RRH) 195 for LTE or a distributed unit (DU) 195 for gNB implementation for 5G, with the other elements of the RAN node 170 possibly being physically in a different location from the RRH / DU, and the one or more buses 157 could be implemented in part as, for example, fiber optic cable or other suitable network connection to connect the other elements (e.g. , a central unit (CU) , gNB-CU) of the RAN node 170 to the RRH / DU 195. Reference 198 also indicates those suitable network link (s) .

[0063] It is noted that description herein indicates that "cells" perform functions, but it should be clear that equipment which forms the cell will perform the functions. The cell makes up part of a base station. That is, there can be multiple cells per base station. For example, there could be three cells for a single carrier frequency and associated bandwidth, each cell covering one-third of a 360 degree area so that the single base station's coverage area covers an approximate oval or circle. Furthermore, each cell can correspond to a single carrier and a base station may use multiple carriers. So if there are three 120 degree cells per carrier and two carriers, then the base station has a total of 6 cells .

[0064] The wireless network 100 may include a network element or elements 190 that may include core network functionality, and which provides connectivity via a link or links 181 with a furthernetwork, such as a telephone network and / or a data communications network (e.g. , the Internet) . Such core network functionality for 5G may include access and mobility management function (s) (AMF(s) ) and / or user plane functions (UPF(s) ) and / or session management function(s) (SMF(s) ) . Such core network functionality for LTE may include MME (Mobility Management Entity) / SGW (Serving Gateway) functionality. These are merely illustrative functions that may be supported by the network element (s) 190, and note that both 5G and LTE functions might be supported. The RAN node 170 is coupled via a link 131 to a network element 190. The link 131 may be implemented as, e.g. , an NG interface for 5G, or an SI interface for LTE, or other suitable interface for other standards. The network element 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / W I / F(s) ) 180, interconnected through one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the network element 190 to perform one or more operations.

[0065] The wireless network 100 may implement network virtualization, which is the process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Network virtualization involves platform virtualization, often combined with resource virtualization. Network virtualization is categorized as either external, combining many networks, or parts of networks, into a virtual unit, or internal, providing networklike functionality to software containers on a single system. For example, a network may be deployed in a tele cloud, with virtualized network functions (VNF) running on, for example, datacenter servers. For example, network core functions and / or radio access network(s) (e.g. CloudRAN, O-RAN, edge cloud) may be virtualized. Note that the virtualized entities that result from the network virtualization are still implemented, at some level, using hardware such as processors 152 or 175 and memories 155 and 171, and also such virtualized entities create technical effects.

[0066] It may also be noted that operations of example embodiments of the present disclosure may be carried out by a plurality of cooperating devices (e.g. cRAN) .

[0067] The computer readable memories 125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multicore processor architecture, as non-limiting examples. The processors 120, 152, and 175 may be means for performing functions, such as controlling the UE 110, RAN node 170, and other functions as described herein.

[0068] In general, the various example embodiments of the user equipment 110 can include, but are not limited to, cellular telephones such as smart phones, tablets, personal digital assistants (PDAs) having wireless communication capabilities,portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, tablets with wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions.

[0069] Having thus introduced one suitable but non-limiting technical context for the practice of the example embodiments of the present disclosure, example embodiments will now be described with greater specificity.

[0070] Features as described herein may generally relate to the Ll / 2 triggered mobility (LTM) procedure. Layer 1 (LI) may be considered a physical layer, and layer 2 (L2) may be considered a data link layer, of a network. LTM is a cell switch procedure, where the UE's serving cell (PCell or PSCell) is switched by the network by sending an LTM cell switch command. An LTM switch command is currently assumed delivered by MAC signaling using a MAC CE . In response, RRC signaling as a L3 based handover is not used, which is one of the current methods for changing between cells. Layer 3 (L3) may be considered a network layer. The LTM cell switch decision is based on measurements (for example LI measurements) that are performed and reported (for example LI measurement report) by the UE . Measurements and reporting are based on LTM candidate cell configuration provided by the network for one or more LTM candidate cells. An LTM candidate cell may be a neighboring cell or a UE's current serving cells (e.g. SCells) .

[0071] In Release-18, LTM measurements on a neighboring candidate cell are performed using synchronization signal blocks (SSB) , transmitted by the candidate cell, for which the SSB configuration is provided to the UE .

[0072] Before the cell switch, network may optionally activate one or more transmission configuration indicator (TCI) state (s) for one or more candidate cells. Once a candidate cell TCI state is activated, the UE may start tracking the time / f requency synchronization using the reference signals associated with the activated TCI state (s) . The UE may also perform early UL synchronization before the cell switch, for example if this is requested by the network.

[0073] Referring now to FIG. 2, illustrated is an example of the LTM procedure in Rel . 18, as described in TS 38.300 V18.0.0. It may be noted that Rel. 18 only covers intra-CU LTM handovers. The LTM procedure may include an LTM preparation phase, an early synchronization phase, an LTM execution phase, and an LTM completion phase.

[0074] In the example of FIG. 2, the UE may be in an RRC_CONNECTED mode. At 205, the UE may send a MeasurementReport message to the gNB . The gNB may decide to configure LTM, and at 210 may initiate LTM candidate preparation. At 215, the gNB may transmit an RRCReconf iguration message to the UE including the LTM candidate conf iguration ( s ) . At 220, the UE may store the LTM candidate conf iguration ( s ) and transmit an RRCReconf igurationComplete message to the gNB.

[0075] At 225, the UE may perform downlink (DL) synchronization with the candidate cell (s) before receiving the cell switchcommand. At 230, the UE may perform early TA acquisition with the candidate cell (s) , according to a network request, before receiving the cell switch command as specified in clause 9.2.6 [38.300] . This may be done via contention free random access (CERA) triggered by a physical downlink control channel (PDCCH) order from the source cell, following which the UE may send a preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CERA towards the candidate cell (s) , the UE does not receive a random access response from the network for the purpose of timing advance (TA) value acquisition, and the TA value of the candidate cell may be indicated in the cell switch command. The UE does not maintain the TA timer for the candidate cell, and may rely on network implementation to guarantee the TA validity.

[0076] At 235, the UE may perform LI measurements on the configured candidate cell (s) and transmit the LI measurement report (s) to the gNB . LI measurement may be performed as long as the RRC reconfiguration (step 2, 215) is applicable. At 240, the gNB may decide to execute cell switch to a target cell. At 245, the gNB may transmit, to the UE, a MAC CE triggering cell switch by including the candidate configuration index of the target cell. At 250, the UE may switch to the target cell and apply the configuration indicated by the candidate configuration index. At 255, the UE may perform the random access procedure towards the target cell, for example if the UE does not have valid TA of the target cell as specified in clause 6.1.3.75 of TS 38.321.

[0077] At 260, the UE may complete the LTM cell switch procedure by sending a RRCReconf igurationComplete message to the target cell. If the UE has performed a random access (RA) procedure instep 7 (255) the UE may consider that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the UE may consider that LTM cell switch execution is successfully completed when the UE determines that the network has successfully received its first UL data.

[0078] It may be noted that the steps 4-8 (225-260) may be performed multiple times for subsequent LTM using the LTM candidate conf iguration ( s ) provided in step 2 (215) .

[0079] The procedure over the air interface described above, with respect to FIG. 2, may be applicable to both intra-gNB-DU LTM and inter-gNB-DU LTM. The overall LTM procedures over Fl-C interface are captured in TS 38.401.

[0080] The LTM procedure may be performed in the context of central unit (s) (CU) and distributed unit (s) (DU) . A central unit (CU) is a logical node which may include the functions (i.e. , gNB functions) such as transfer of user data, mobility control, radio access network sharing, positioning, session management etc. , except those functions allocated exclusively to the DU. A CU may control the operation of DUs over a front-haul (Fs) interface. A central unit (CU) may also be known as BBU / REC / RCC / C-RAN / V-RAN . A distributed Unit (DU) is a logical node which may include a subset of the functions (i.e. , gNB functions) , depending on the functional split option. The operation of the DU may be controlled by the CU . A distributed unit (DU) may also be known with other names like RRH / RRU / RE / RU.

[0081] Example embodiments of the present disclosure may be applicable in the context of an integrated access and backhaul(IAB) system. An IAB node may logically consist of at least a UE that communicates with upstream nodes, and a RAN component, such as a gNB DU, that may communicate with downstream IAB nodes or a subscriber UE .

[0082] Features as described herein may generally relate to RRC modeling of Rel . 18 LTM. An example of the RRC (Re ) Conf iguration message provided to a UE for LTM is illustrated schematically in FIG. 3. As shown, the UE may contain, or receive, the source cell configuration (including measurement configuration information element (s) (IE) , radio bearers, etc. ) and target cell configuration in an LTM Configuration IE (LTMConfigA, 310) . LTMConfigA may include a reference configuration which is common for all target cells (320) ; a list of delta configurations (one for each target cell) (330) , which may contain the delta (cellspecific) configuration of each target cell (350, 360) ; and a CSI resource config IE which contains the target cells beam configuration (340) . When the UE receives the MAC CE to trigger cell change, the UE may apply the target cell delta configuration on top of the reference configuration, and may create a protocol stack for the LTM candidate cell.

[0083] Referring now to FIG. 4, illustrated is an example of the LTM-Config information element, including SetupRelease for Ref erenceConf iguration-rl8 (410) , and CandidateToAddModList (420) .

[0084] TABLE 1 describes some LTM-Config field descriptions with respect to the LTM-Config information element.

[0085] TABLE 1

[0086] TABLE 2 describes LTM-MCG with respect to the LTM-Config information element.

[0087] TABLE 2

[0088] Referring now to FIG. 5, illustrated is an example of a Referenceconfiguration information element. The IE Referenceconfiguration is used provide a configuration that is common, within the same cell group, to all configured non-complete candidate configurations.

[0089] Referring now to FIG. 6, illustrated is an example of an LTM-Candidate information element, including CandidateConf ig-r 18 (610) and Conf igComplete-r 18 (620) . The IE LTM-Candidate concerns a LTM candidate configuration to add or modify.

[0090] TABLE 3 describes some LTM-Candidate field descriptions with respect to the LTM-Candidate information element.

[0091] TABLE 3

[0092] TABLE 4 describes some LTM-SSB-Conf ig field descriptions with respect to the LTM-Candidate information element._ _

[0093] TABLE 4

[0094] Referring now to FIGs. 7A-7D, illustrated is an example of a RRCReconf iguration message, including SetupRelease for LTM- Config-rl8 (710) in FIG. 7C. The RRCReconf iguration message is the command to modify an RRC connection. It may convey information for measurement configuration, mobility control, radio resource configuration (including RBs, MAC main configuration and physical channel configuration) and access stratum (AS) security configuration. The signaling radio bearer used for the RRCReconf iguration message may be SRB1 or SRB3. The radio link control service access point (RLC-SAP) used for the RRCReconf iguration message may be acknowledged mode (AM) . The logical channel used for the RRCReconf iguration message may be dedicated control channel (DCCH) . The direction used for the RRCReconf iguration message may be network to UE . Fields description of the RRC Reconfiguration message can be found in TS 38.331.

[0095] Features as described herein may generally relate to Release 19 NR mobility enhancements. LTM was introduced in Rel- 18, and may offer improvements in handover latency and interruption time compared to Layer 3 based mobility. However, LTM as introduced in Rel-18 also has a number of limitations compared to Layer 3 mobility. This Rel-19 work item aims to remove a number of these limitations with the following objectives:"...Specify support for inter-CU Layer 2 Mobility (LTM) [RAN2, RAN3]Prioritize the case when CU is acting as MN when DC is not configuredAs secondary priority, support the case when NR-DC is configured and CU is acting as SN and MCG is unchangedAs secondary priority, support the case when NR-DC is configured, CU is acting as MN and SCG is unchanged or SCG is releasedNote: The case that LTM is configured in both MCG and SCG is excludedSpecify support for subsequent LTM mobility procedures aiming to avoid RRC configuration between cell switches as per Rel-18 LTMCoordination with SA3 needed with respect to security key handlingNote: Rel. 18 intra-CU LTM procedure is considered as baseline for adding inter-CU supportMeasurements related enhancements for purpose of supporting LTM: [RAN2, RANI]Measurement related enhancements are applicable to Intra-CU MCG / SCG LTM and Inter-CU MCG / SCG LTMSpecify necessary components to support event triggered LI measurement reporting [RAN2, RANI]RANI and RAN2 to progress independently on the event triggered measurements objectives of their respective MIMO and Mobility enhancement WIs. Review progress at RAN#105 to see if any modification of objectives is required to avoid / manage any overlap in the workSpecify support for CSI-RS measurements for LTM procedures and enable CSI-RS based beam management, and / or other necessary physical layer operations on candidate cells before LTM [RANI]Specify support of conditional LTM [RAN2, RAN3, RANI]Specify UE evaluated conditions for triggering LTMAim to support conditional LTM including subsequent LTMPrioritise intra-CU LTMCheckpoint to review objective at RAN#105. RAN WG work to not start before this checkpoint..."

[0096] A simple extension of Rel. 18 RRC structure would be for a common reference configuration to be generated across all the candidate cells, irrespective of the CUs / DUs they belong to. In other words, there may be only one reference configuration, and if the UE supports it, all the candidate cells may be described as delta over the reference configuration. For a UE to derive a complete configuration, the UE may combine the reference configuration with the delta configuration.

[0097] However, there are some drawbacks to this extension. For example, it requires signaling exchange between the CUs to generate a common reference configuration. The signaling procedure may be dependent on the assumption of which CU (source or target) generates the reference configuration. Such signaling exchange may be an extra overhead, and may cause latency (longer preparation phase) . Furthermore, it is not clear if the single reference configuration across cells belonging to multiple CUs isbeneficial. This is because the main advantage of reference configurations comes from the fact that it avoids duplicated / redundant information, and all such information is signaled once as part of the reference configuration. However, it is not clear if cells belonging to multiple CUs will have multiple redundant IES .

[0098] In an example embodiment, the RRC model / structure in case of inter-CU LTM may have a modular design and reuse the Rel. 18 LTM-Config, which may be configured for each CU / gNB. In an example embodiment, separate reference configurations may be configured for each CU / gNB, and only the cells belonging to the same CU / gNB may be delta over the respective reference configuration.

[0099] Referring now to FIG. 8, illustrated is an example of an RRC model / structure, for inter-CU LTM, according to an example embodiment ( s ) of the present disclosure. The LTM-Config (now called LTMConf igGroup) in CU1 / CU2 / CU3 (820, 830, 840) may be according to Rel. 18 structure, and a new Rel. 19 IE (LTM-Config) (810) may comprise a combination of all the LTM ConfigGroups (820, 830, 840) . In other words, LTM Config = [LTM Conf igGroupl , LTM Conf igGroup2 , LTM Conf igGroup3 , ..., LTM Conf igGroupN] ; where N may be a maximum number of CUs or cells supported as LTM candidates.

[0100] In the example of FIG. 8, DU1.1 (850) and DU1.2 (860) are associated with CUI, which defines LTM ConfigGroup 1 (820) . The LTM-Ref erenceConf iguration (870) is associated with CUI. The LTM- Candidate-Li s t (880) includes, at least, information associated with DU1.1 (850) and DU1.2 (860) . LTM ConfigGroup 1 (820) may also include LTM-CSI-Resource-Conf ig-List (890) .

[0101] A technical effect of example embodiments of the present disclosure may be to allow more flexibility and extendibili ty as a result of the modular design. A technical effect of example embodiments of the present disclosure may be to enable reuse of parts of the Rel. 18 design. A technical effect of example embodiments of the present disclosure may be to allow lower signaling overhead to prepare a reference configuration. A technical effect of example embodiments of the present disclosure may be to allow faster preparation due to less signaling exchange.

[0102] Ref erring now to FIG. 9, illustrated is an example of a RRCReconf iguration message according to an example embodiment of the present disclosure. In contrast to FIG. 7, the RRCReconf iguration message illustrated includes a SetupRelease for LTM-Conf ig-r 19 (910) .

[0103] Referring now to FIG. 10, illustrated is an example of an LTM-Config information element according to an example embodiment of the present disclosure. In contrast to the LTM-Config information element illustrated in FIG. 4, the LTM-Config information element of FIG. 10 may be used to provide LTM candidate configurations groups. The LTM-Config information element of FIG. 10 includes Conf igGroupToAddModList-rl 9 (1010) and Conf igGroupToBeReLeaseList-rl 9 (1020) .

[0104] Ref erring now to FIG. 11, illustrated is an example of an LTM-Conf igGroup information element, including a SetupRelease for Ref erenceConf iguration-rl8 (1110) . In an example embodiment, the IE LTM-Conf igGroup may be used to provide LTM candidate configurations and reference configurations.

[0105] Referring now to FIGs. 12A-12B, illustrated is an example of an LTM-Candidate information element according to an example embodiment of the present disclosure. Additional Rel . 19 IES may be added to the example structure of FIGs. 12A-12B; the exact IEs are given just as one example.

[0106] In an example embodiment, target gNBs / CUs may generate reference plus delta configurations. Referring now to FIGs. 13A- 13B, illustrated is an example signaling flow for target gNBs generating reference configurations. The source gNB may ask for the LTM configurations of the target cells be in the form of reference plus delta. Each target gNB may generate a separate reference configuration, and base the delta configurations of the different target cells on the respective reference configuration of the associated target gNB.

[0107] In the example of FIGs. 13A-13B, the source gNB may be a base station and / or CU serving the UE . The source gNB may provide the cell serving the UE, as well as at least one target cell. In the example of FIGs. 13A-13B, each target gNB and / or CU may provide at least one target cell.

[0108] At 1301, user data may be shared between a UE, a source gNB serving the UE, and a user plane function (UPF) . At 1302, mobility control information may be provided by the AMF. At 1303, the UE may transmit, to the source gNB, L3 measurement reports. Although not pictured in FIGS. 13A-13B, the source gNB may obtain information about the capabilities of the UE, for example information indicative of whether the UE supports the use of reference configurations, whether the UE supports the use ofmultiple reference configurations, and / or a number of reference configurations the UE is configured to support.

[0109] At 1305, the source gNB may determine, for example based on an L3 measurement received from the UE, to trigger an LTM-based handover for the UE . At 1310, the source gNB may transmit, to a target gNB, a handover request, which may include a flag indicating a request for a reference configuration associated with the target gNB, as well as delta conf iguration ( s ) for target cell (s) belonging to the target gNB. In other words, the flag may request that the target gNBs generate the target cells' configurations to be in the format of reference + delta configurations. In an example embodiment, the flag may comprise 1 bit. At 1315, the source gNB may transmit, to other potential target gNB(s) , a handover request, which may include a flag indicating a request for a reference configuration associated with the other potential target gNB(s) , as well as delta conf iguration ( s ) for target cell (s) belonging to the other potential target gNB(s) .

[0110] In an example embodiment, the source gNB may determine to transmit the flag indicating the request for reference plus delta configurations based, at least partially, on a capability of the UE . For example, the flag may be transmitted dependent on a UE capability to support reference conf iguration ( s ) , or a number of reference configurations supported by the UE . For example, if the UE has the capability to support X reference configurations, and the number X has not been reached, the source gNB may optionally conf igure / set the flag in the handover request to request that the target cells' configurations to be in the format of reference + delta configurations.

[0111] It may be noted that, although in the example of FIGS. 13A-13B the source gNB transmits a handover request to a target gNB and other potential target gNB ( s ) , the source gNB may transmit a handover request to any number of target gNB.

[0112] At 1320 and 1325, the target gNBs may perform admission control. In an example embodiment, the target gNBs may generate the configurations according to the handover requests received from the source gNB. In an example embodiment, each gNB (CU) may generate a single full reference configuration with corresponding delta configurations for each cell in that gNB.

[0113] In the present disclosure, "full reference configuration" or "complete reference configuration" means a reference configuration that is not a delta configuration over some other configuration. In other words, a full reference configuration is not defined relative to another configuration.

[0114] It may be noted that the handover requests received by the target gNBs may be different. For example, the flag in one handover request may request that the target cells' configurations to be in the format of reference + delta configurations, whereas the flag in another handover request may request that full configurations be provided.

[0115] At 1330, the target gNB may transmit, to the source gNB, a handover request acknowledgement, which may comprise an LTM- ConfigGroup with reference IE ( Itm-Ref erenceConf iguration-rl 9 ) and corresponding delta conf iguration ( s ) , which may include, for example, ltm-CandidateToReleaseList-rl9 and Itm- ConadidateToAddModList-rl9.

[0116] At 1335, the other potential target gNB ( s ) may transmit, to the source gNB, a handover request acknowledgement, which may comprise an LTM-Conf igGroup with reference IE (Itm- Ref erenceConf iguration-rl9) and corresponding delta conf iguration ( s ) , which may include, for example, Itm- CandidateToReleaseList-rl9 and ltm-ConadidateToAddModList-rl9.

[0117] It may be noted that each of the target gNB (s) may provide delta conf iguration ( s ) for any number of target cells. For example, each target gNB may provide a delta configuration for at least one target cell.

[0118] The source gNB may consolidate or combine the received reference + delta format configurations into an LTM-Config IE. At 1340, the source gNB may transmit, to the source gNB, an RRC Reconfiguration message containing the target cells' configurations in separate IES ( LTM-Conf igGroup ) inside the LTM- Config. The LTM-Config IE may contain LTM-Conf igGroups from each CU.

[0119] At 1345, the UE may transmit, to the source gNB, a RRCReconf igurationComplete message .

[0120] At 1350, the UE may transmit, to the source gNB, LI measurement report (s) . At 1351, the source gNB may determine to trigger LTM. At 1352, the source gNB may transmit, to the UE, a LTM cell switch command. At 1353, the source gNB may transmit, to the target gNB, a SN status transfer. At 1354, user data may be transmitted from the UPF to the target gNB via the source gNB. At 1355, LTM handover completion may be performed. At 1356, the UE may transmit, to the target gNB, a RRCReconf iguration complete message. At 1357, the target gNB may transmit, to the source gNB,a handover success message. At 1358, the source gNB may transmit, to the other potential target gNB(s) , a handover cancel message. At 1359, user data may be shared between the UE, the target gNB and the UPF. At 1360, the target gNB may transmit, to the AMF, a path switch request. At 1361, the AMF may perform path switch in UPF. At 1362, the UPF may transmit an end marker to the target gNB via the source gNB. At 1363, user data may be shared between the target gNB and the UPF. At 1364, the AMF may transmit, to the target gNB, a path switch request acknowledgement. At 1365, the target gNB may transmit, to the source gNB, a UE context release message .

[0121] Ref erring now to FIG. 14, illustrated is an example RRC structure, where each target gNB may generate LTM-Conf igGroup information with a reference configuration and dependent delta conf iguration ( s ) for the LTM case. The source gNB may generate, and the UE may receive, an RRCReconf iguration message (1410) , which may comprise an LTM-Config information element (1420) . The LTM- Config information element (1420) may include one or more LTM- ConfigGroup information elements, (1430, 1450) that are each generated by a different target gNB. Each LTM-Conf igGroup information element may include a full configuration (1440, 1470) that serves as a reference configuration for the target cells belonging to the target gNB, as well as one or more delta LTM- Candidate information elements (1450, 1480) comprising delta RRC configurations for the target cells.

[0122] By applying a delta configuration of a target cell to the reference configuration of the target gNB to which the target cell belongs, the UE may determine the full configuration for the target cell .

[0123] Referring now to FIGS. 15A-15B, illustrated is an example signaling flow for target gNBs generating reference configurations or generating full / complete configurations. In an example embodiment, full and delta configurations may coexist.

[0124] Portions of FIGS. 15A-15B with the same labels as FIGS. 13A-13B are not described again so as to avoid duplication of description .

[0125] At 1505, the source gNB may determine, for example based on an L3 measurement received from the UE, to trigger an LTM-based handover for the UE . At 1510, the source gNB may transmit, to a target gNB, a handover request, which may include a flag requesting that the target gNBs generate the target cells' configurations to be in the format of reference + delta configurations. At 1515, the source gNB may transmit, to other potential target gNB ( s ) , a handover request, either without the flag, or with the flag configured to indicate that the other potential target gNB(s) are to generate full configurations. At 1520 and 1525, the target gNBs may perform admission control. In an example embodiment, the target gNBs may generate the configurations according to the handover requests received from the source gNB. In this example, the target gNB may generate a single full reference configuration with corresponding delta configurations for each cell in that gNB, whereas the other potential target gNBs may generate a full configuration for each target cell.

[0126] At 1530, the target gNB may provide the configurations in the form of reference + delta configurations. For example, the target gNB may transmit, to the source gNB, a handover request acknowledgement comprising an LTM-Conf igGroup, which may comprisereference IE ( Itm-Ref erenceConf iguration-rl 9 ) and corresponding delta configurations ( Itm-CandidateToReleaseList-rl 9 and Itm-CandidateToAddModList-rl9 ) .

[0127] At 1535, the other potential target gNB ( s ) may provide the configurations in the form of complete configurations. For example, the target gNB may transmit, to the source gNB, a handover request acknowledgement comprising LTM-Conf igGroup without any reference configuration; the configurations may be full configurations ( Itm-CandidateToReleaseList-rl 9 and Itm- CandidateToAddModList-rl 9 ) .

[0128] The source gNB may consolidate or combine the received configurations into an LTM-Config IE. At 1540, the source gNB may transmit, to the source gNB, an RRC Reconfiguration message containing the target cells' configurations in separate IES (LTM- Conf igGroup) inside the LTM-Config. The LTM-Config IE may contain LTM-Conf igGroups from each CU, which may be reference + delta configurations or full configurations.

[0129] At 1545, the UE may transmit, to the source gNB, a RRCReconf igurationComplete message .

[0130] Referring now to FIG. 16, illustrated is an example RRC structure, where one gNB may generate LTM-Conf igGroup information with reference configuration and the dependent delta conf iguration ( s ) , and the other gNB may create / generate the conf iguration ( s ) as full / complete conf iguration ( s ) . The source gNB may generate, and the UE may receive, an RRCReconf iguration message (1610) , which may comprise an LTM-Config information element (1620) . The LTM-Config information element (1620) may include one or more LTM-Conf igGroup information elements, (1630,1650) that are each generated by a different target gNB. In the example of FIG. 16, one LTM-Conf igGroup information element, 1630, may include a full configuration (1640) that serves as a reference configuration for the target cells belonging to the target gNB, as well as one or more delta LTM-Candidate information elements (1650) comprising delta RRC configurations for the target cells. In contrast, another LTM-Conf igGroup information element, 1660, does not include a reference configuration (1670) , but only complete configurations (1680) for each target cell belonging to the target gNB.

[0131] The UE may be able to determine which LTM-Conf igGroup information elements include a reference configuration + delta configuration structure, and which include no reference configuration, but rather complete configurations only.

[0132] Referring now to FIGS. 17A-17B, illustrated is an example signaling flow for target gNBs generating reference configurations based on the reference configuration and the initial full (serving gNB) reference configuration. The initial full reference configuration may be indicated via a flag.

[0133] In an example embodiment, the UE may indicate, to the source gNB, that it has a capability for determining a reference configuration from a delta reference configuration. In other words, the UE may be capable of performing the delta operation twice to determine a configuration for a target cell.

[0134] In the present disclosure, the terms "initial reference configuration", "initial full reference configuration", "source gNB reference configuration", "initial serving gNB referenceconfiguration", and "source reference configuration" may be used interchangeably .

[0135] Portions of FIGS. 17A-17B with the same labels as FIGS. 13A-13B are not described again so as to avoid duplication of description .

[0136] At 1705, the source gNB may determine, for example based on an L3 measurement received from the UE, to trigger an LTM-based handover for the UE . At 1710, the source gNB may transmit, to a target gNB, a handover request, which may include a flag requesting that the target gNBs generate the target cells' configurations to be in the format of reference + delta configurations, based on a source reference configuration. The source gNB may send its own reference configuration to the target gNBs. The target gNBs may use this reference for creating their own reference configuration in delta format .

[0137] Alternatively, the source reference configuration may be provided to the target gNB ( s ) in a new message (i.e. not in the handover request) .

[0138] In an example embodiment, the source reference configuration may be a configuration specific to a target cell belonging to the source gNB, a configuration generated by the source gNB, a configuration selected by the source gNB, etc.

[0139] At 1715, the source gNB may transmit, to other potential target gNB(s) , a handover request, which may include a flag requesting that the other potential target gNB ( s ) generate the target cells' configurations to be in the format of reference + delta configurations, based on a source reference configuration.

[0140] Alternatively, the source reference configuration may be provided to the other potential target gNB(s) in a new message (i.e. not in the handover request) .

[0141] At 1720 and 1725, the target gNBs may perform admission control. In an example embodiment, the target gNBs may generate the configurations according to the handover requests received from the source gNB. In an example embodiment, each gNB (CU) may generate a single full reference configuration that is delta over the source reference configuration, with corresponding delta configurations for each cell in that gNB.

[0142] In an example embodiment, the target gNBs (CUs) may each generate a single full reference configuration with corresponding delta configurations for each cell in that gNB . The reference configuration may be in the format of a delta configuration. Accordingly, the complete configuration for a given target cell may be obtained by applying first the delta over the source reference configuration to obtain the target CU reference configuration, then applying the second delta configuration on top of that. At 1730 and 1735, the target gNBs may transmit, to the source gNB, handover request acknowledgement messages comprising such delta reference configurations (over the source reference configuration) and delta configurations. In an example embodiment, the LTM-Conf igGroup may be provided with reference IE (Itm-Ref erenceConf iguration-rl9) as a delta itself, and corresponding delta configurations ( 1 tm-CandidateToReleaseList- rl9 and Itm-CandidateToAddModList-rl 9 ) .

[0143] At 1740, the source gNB may transmit, to the UE, anRRCReconf iguration message. The RRCReconf iguration message maycontain the target cells' configurations in separate IES (LTM- Conf igGroup) inside the LTM-Config. The reference configurations of the target gNBs may be delta over the initial gNBs reference configuration. A flag inside the LTM-Conf igGroup may indicate whether the reference configuration is full or delta. The UE may be able to use the flag to determine how to interpret the LTM- Conf igGroups .

[0144] In an example embodiment, the LTM-Config IE may comprise the LTM-Conf igGroups from each UE, and the Itm- Ref erenceConf iguration-rl9 may be in delta format for the target gNB configurations and they may be in full format for the initial gNB configuration. In an example embodiment, the source reference configuration may be provided to the UE . Alternatively, the source reference configuration may be provided to the UE in a new message (i.e. not in the RRCReconf iguration message) .

[0145] In an example embodiment, the LTM-Config IE may comprise a plurality of LTM-Conf igGroups , which may all comprise full reference configurations, may all comprise delta reference configurations, or may partially comprise full reference configurations and partially comprise delta reference configurations .

[0146] At 1745, the UE may transmit, to the source gNB, an RRCReconf gurationComplete message .

[0147] Ref erring now to FIG. 18, illustrated is an example RRC structure, where the reference configuration of the target gNBs may be in delta form / format with reference to the initial gNB full reference configuration. An additional flag, indicating a full reference configuration, may be used.

[0148] The source gNB may generate, and the UE may receive, an RRCReconf iguration message (1810) , which may comprise an LTM- Config information element (1820) . The LTM-Config information element (1820) may include one or more LTM-Conf igGroup information elements, (1830, 1870) that are each generated by a different target gNB. In the example of FIG. 18, one LTM-Conf igGroup information element, 1830, may include a reference configuration over an initial gNB full reference configuration (1840) that may serve as a reference configuration for the target cells belonging to the target gNB, as well as a flag indicating that the full reference configuration is used (1850) , and one or more delta LTM- Candidate information elements (1860) comprising delta RRC configurations for the target cells over the delta reference configuration over the initial full reference configuration. In contrast, another LTM-Conf igGroup information element, 1870, may include target gNB generated delta reference conf iguration ( s ) (1880) , and one or more delta LTM-Candidate information elements (1890) comprising delta RRC configurations for the target cells.

[0149] Referring now to FIGS. 19A-19B, illustrated is an example signaling flow for the source gNB generating delta reference configurations based on the reference configuration and the initial serving / source gNB reference configuration.

[0150] Portions of FIGS. 19A-19B with the same labels as FIGS. 13A-13B are not described again so as to avoid duplication of description .

[0151] At 1905, the source gNB may determine, for example based on an L3 measurement received from the UE, to trigger an LTM-basedhandover for the UE . At 1910 and 1915, the source gNB may transmit, to target gNBs, a handover request, which may include a flag requesting that the target gNBs generate the target cells' configurations to be in the format of reference + delta configurations. At 1920 and 1925, the target gNBs may perform admission control. In an example embodiment, the target gNBs may generate the configurations according to the handover requests received from the source gNB. In this example, the target gNBs may generate a single full reference configuration with corresponding delta configurations for each cell in that gNB.

[0152] At 1930 and 1935, the target gNBs may transmit, to the source gNB, handover request acknowledgement messages, which may include LTM-Conf igGroup with reference IE (Itm- Ref erenceConf iguration-rl9) and corresponding delta configurations ( Itm-CandidateToRelesaseList-rl 9 and Itm- CandidateToAddModList-rl9) .

[0153] At 1940, the source gNB may generate the delta over the current source reference configuration. For example, for each reference configuration associated with a target gNB / CU, the source gNB may determine the delta of the reference configuration over a source / initial reference configuration, which may be selected / determined by the source gNB. The source gNB may provide the UE with the delta of each reference configuration over the source / initial reference configuration, rather than the reference configurations provided by the target gNBs. The source gNB may also provide the source / initial reference configuration to the UE .

[0154] At 1945, the source gNB may transmit, to the UE, a RRCReconf iguration message, which may contain the target cells'configurations in separate IES ( LTM-Conf igGroup ) inside the LTM- Config. The LTM-Config IE may comprise the LTM-Conf igGroups from each CU . The 1 tm-Re f erenceConf iguration-r 19 may be in delta format for the target gNBs configurations, and they may be in full format for the initial gNB configuration.

[0155] The UE may be able to determine the configuration for each target cell by applying the delta reference configuration for the target gNB over the source reference configuration, and then applying the delta configuration for the target cell.

[0156] At 1950, the UE may transmit, to the source gNB, an RRCReconf igurationComplete message .

[0157] Ref erring now to FIG. 20, illustrated is an example RRC structure, where the reference configurations may themselves be delta over the initial gNB's reference configuration. The main difference between this example embodiment and the example embodiment illustrated in FIG. 18 is that the generated reference delta configurations of the target gNBs may be generated by the initiating gNB (i.e. the source gNB) .

[0158] The source gNB may generate, and the UE may receive, an RRCReconf iguration message (2010) , which may comprise an LTM- Config information element (2020) . The LTM-Config information element (2020) may include one or more LTM-Conf igGroup information elements, (2030, 2070) that may each be generated by a different target gNB, except for the reference configuration. In the example of FIG. 20, one LTM-Conf igGroup information element, 2030, may include a reference configuration over an initial gNB full reference configuration (2040) that may serve as a reference configuration for the target cells belonging to the target gNB, aswell as a flag indicating that the full reference configuration is used (2050) , and one or more delta LTM-Candidate information elements (2060) comprising delta RRC configurations for the target cells over the delta reference configuration over the initial full reference configuration. The included reference configuration may be generated by the source gNB.

[0159] In contrast, another LTM-Conf igGroup information element, 2070, may include target gNB generated delta reference conf iguration ( s ) (2080) , and one or more delta LTM-Candidate information elements (2090) comprising delta RRC configurations for the target cells.

[0160] In an example embodiment, a new RRC model / structure may be used for signaling of LTM configurations between source DU of a source CU and a target DU of a target CU.

[0161] Example embodiments of the present disclosure may relate to multiple LTM configurations belonging to different CUs .

[0162] Example embodiments of the present disclosure may relate to Xn signaling.

[0163] Example embodiments of the present disclosure may relate to the case of non-split gNB architecture, where CU may refer to gNB.

[0164] A technical effect of example embodiments of the present disclosure may be to enable an efficient RRC model / structure, which may have the technical effect of allowing for reduced signaling overhead and maximization of the advantages of configuring a reference configuration.

[0165] FIG. 21 illustrates the potential steps of an example method 2100. The example method 2100 may include: receiving, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one first group configuration, wherein the at least one first group configuration comprises, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration is defined based on the first reference configuration, 2110; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration, 2120. The example method 2100 may be performed, for example, with a UE .

[0166] FIG. 22 illustrates the potential steps of an example method 2200. The example method 2200 may include: determining to cause switching of a serving cell of a user equipment, 2210; transmitting, to at least one first target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a first group configuration, wherein the first group configuration comprises, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration is defined based on the first reference configuration, 2220; receiving, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request, 2230; and transmitting, to the user equipment, a configurationcomprising, at least, the at least one received first group configuration, 2240. The example method 2200 may be performed, for example, with a source gNB, a base station, a network node, a network entity, a network, a CU, etc.

[0167] FIG. 23 illustrates the potential steps of an example method 2300. The example method 2300 may include: receiving, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration comprising a reference configuration associated with one or more target cells the apparatus provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration is defined based on the reference configuration, 2310; generating the group configuration, 2320; and transmitting, to the source CU, the group configuration, 2330. The example method 2300 may be performed, for example, with a target gNB, a base station, a network node, a network entity, a network, a CU, etc.

[0168] FIG. 24 illustrates the potential steps of an example method 2400. The example method 2400 may include: receiving, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one group configuration, wherein the at least one group configuration comprises, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration is defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated withthe CU, wherein the at least one delta configuration is defined based on the reference configuration associated with the CU, 2410; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration, 2420. The example method 2400 may be performed, for example, with a UE.

[0169] FIG. 25 illustrates the potential steps of an example method 2500. The example method 2500 may include: determining to cause switching of a serving cell of a user equipment, 2510; transmitting, to at least one target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration comprises at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration is defined based on the full reference configuration, 2520; receiving, from respective ones of the at least one target CU, at least one group configuration according to the handover request, 2530; and transmitting, to the user equipment, a configuration comprising, at least, the at least one group configuration, 2540. The example method 2500 may be performed, for example, with a source gNB, a base station, a network node, a network entity, a network, a CU, etc.

[0170] FIG. 26 illustrates the potential steps of an example method 2600. The example method 2600 may include: receiving, froma source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with the apparatus, wherein the reference configuration comprises at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the apparatus provides, wherein the at least one delta configuration is defined based on the full reference configuration, 2610; generating the group configuration, 2620; and transmitting, to the source CU, the group configuration, 2630. The example method 2600 may be performed, for example, with a target gNB, a base station, a network node, a network entity, a network, a CU, etc.

[0171] In accordance with one example embodiment, an apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0172] The configuration may further comprise at least one second group configuration, wherein the second group configuration may comprise, at least: a second reference configuration associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU, and at least one second delta configuration associated with at least one second target cell that is associated with the second CU, wherein the at least one second delta configuration may be defined based on the second reference configuration.

[0173] The first reference configuration may be at least partially different from the second reference configuration.

[0174] The configuration may further comprise at least one second group configuration, wherein the second group configuration may comprise, at least: at least one full configuration for at least one second target cell that is associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU.

[0175] The example apparatus may be further configured to: provide at least one capability of the apparatus, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, and / or a maximum number of reference configurations the apparatus can use.

[0176] The at least one first group configuration may comprise a flag configured to indicate that a format of the at least one first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0177] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0178] The example apparatus may be further configured to: determine a configuration for a target cell, of the at least one first target cell, based, at least partially, on the first reference configuration and a delta configuration, of the at least one first delta configuration, associated with the target cell.

[0179] In accordance with one aspect, an example method may be provided comprising: receiving, with a user equipment from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0180] The configuration may further comprise at least one second group configuration, wherein the second group configuration may comprise, at least: a second reference configuration associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU, and at least one second delta configuration associated with at least one second target cell that is associated with the second CU, wherein the at least one second delta configuration may be defined based on the second reference configuration.

[0181] The f irst reference configuration may be at least partially different from the second reference configuration.

[0182] The configuration may further comprise at least one second group configuration, wherein the second group configuration may comprise, at least: at least one full configuration for at least one second target cell that is associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU.

[0183] The example method may further comprise: providing at least one capability of the user equipment, wherein the at least one capability comprises at least one of : a capability for using multiple reference configurations, and / or a maximum number of reference configurations the user equipment can use.

[0184] The at least one first group configuration may comprise a flag configured to indicate that a format of the at least one first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0185] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0186] The example method may further comprise: determining a configuration for a target cell, of the at least one first target cell, based, at least partially, on the first reference configuration and a delta configuration, of the at least one first delta configuration, associated with the target cell.

[0187] In accordance with one example embodiment, an apparatus may comprise: circuitry configured to perform: receiving, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and circuitry configured to perform: performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0188] In accordance with one example embodiment, an apparatus may comprise: processing circuitry; memory circuitry including computer program code, the memory circuitry and the computer program code configured to, with the processing circuitry, enable the apparatus to: receive, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0189] As used in this application, the term "circuitry" or "means" 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 sof tware / f irmware 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." Thisdefinition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (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.

[0190] In accordance with one example embodiment, an apparatus may comprise means for: receiving, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0191] The configuration may further comprise at least one second group configuration, wherein the second group configuration may comprise, at least: a second reference configuration associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU, and at least onesecond delta configuration associated with at least one second target cell that is associated with the second CU, wherein the at least one second delta configuration may be defined based on the second reference configuration.

[0192] The first reference configuration may be at least partially different from the second reference configuration.

[0193] The configuration may further comprise at least one second group configuration, wherein the second group configuration may comprise, at least: at least one full configuration for at least one second target cell that is associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU.

[0194] The means may be further configured for: providing at least one capability of the apparatus, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, and / or a maximum number of reference configurations the apparatus can use.

[0195] The at least one first group configuration may comprise a flag configured to indicate that a format of the at least one first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0196] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations,wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0197] The means may be further configured for: determining a configuration for a target cell, of the at least one first target cell, based, at least partially, on the first reference configuration and a delta configuration, of the at least one first delta configuration, associated with the target cell.

[0198] A processor, memory, and / or example algorithms (which may be encoded as instructions, program, or code) may be provided as example means for providing or causing performance of operation.

[0199] In accordance with one example embodiment, a non- transitory computer-readable medium comprising instructions stored thereon which, when executed with at least one processor, cause the at least one processor to: cause receiving, with a user equipment from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration .

[0200] In accordance with one example embodiment, a non- transitory computer-readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, with a user equipment from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0201] The configuration may further comprise at least one second group configuration, wherein the second group configuration may comprise, at least: a second reference configuration associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU, and at least one second delta configuration associated with at least one second target cell that is associated with the second CU, wherein the at least one second delta configuration may be defined based on the second reference configuration.

[0202] The first reference configuration may be at least partially different from the second reference configuration.

[0203] The configuration may further comprise at least one second group configuration, wherein the second group configuration maycomprise, at least: at least one full configuration for at least one second target cell that is associated with a second central unit (CU) , wherein the first CU may be at least partially different from the second CU.

[0204] The example non- transitory computer-readable medium may further comprise program instructions stored thereon for performing: providing at least one capability of the apparatus, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, and / or a maximum number of reference configurations the user equipment can use.

[0205] The at least one first group configuration may comprise a flag configured to indicate that a format of the at least one first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0206] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0207] The example non-transitory computer-readable medium may further comprise program instructions stored thereon for performing: determining a configuration for a target cell, of the at least one first target cell, based, at least partially, on thefirst reference configuration and a delta configuration, of the at least one first delta configuration, associated with the target cell .

[0208] In accordance with another example embodiment, a non- transitory program storage device readable by a machine may be provided, tangibly embodying instructions executable by the machine for performing operations, the operations comprising: causing receiving, with a user equipment from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0209] In accordance with another example embodiment, a non- transitory computer-readable medium comprising instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: causing receiving, with a user equipment from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configurationassociated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration .

[0210] A computer implemented system comprising: at least one processor and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: causing receiving, with a user equipment from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) , and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration .

[0211] A computer implemented system comprising: means for causing receiving, with a user equipment from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one first group configuration, wherein the at least one first group configuration may comprise, at least: a first reference configuration associated with a first central unit (CU) ,and at least one first delta configuration associated with at least one first target cell that is associated with the first CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; and means for performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0212] In accordance with one example embodiment, an apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine to cause switching of a serving cell of a user equipment; transmit, to at least one first target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; receive, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and transmit, to the user equipment, a configuration that may comprise, at least, the at least one received first group configuration.

[0213] The example apparatus may be further configured to: obtain at least one capability of the user equipment, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, and / or a maximum number of reference configurations the user equipment can use; anddetermining whether to request, from the at least one first target CU, the first group configuration based, at least partially, on the at least one capability of the user equipment.

[0214] The example apparatus may be further configured to: transmit, to at least one second target central unit (CU) , a second handover request, wherein the at least one first target CU may be at least partially different from the at least one second target CU, wherein the second handover request may comprise, at least, a request for a second group configuration that may comprise at least one full configuration for at least one second target cell that is associated with at least one second central unit (CU) ; and receive, from respective ones of the at least one second target CU, at least one second group configuration according to the second handover request, wherein the configuration transmitted to the user equipment may further comprise, at least, the at least one second group configuration.

[0215] The request for the group configuration may comprise a flag configured to indicate that a format of the first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0216] A radio resource control (RRC) reconfiguration message may comprise the configuration that may comprise, at least, the at least one received first group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0217] In accordance with one aspect, an example method may be provided comprising: determining, with a source central unit (CU) , to cause switching of a serving cell of a user equipment; transmitting, to at least one first target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; receiving, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and transmitting, to the user equipment, a configuration that may comprise, at least, the at least one received first group configuration .

[0218] The example method may further comprise: obtaining at least one capability of the user equipment, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, and / or a maximum number of reference configurations the user equipment can use; and determining whether to request, from the at least one first target CU, the first group configuration based, at least partially, on the at least one capability of the user equipment.

[0219] The example method may further comprise: transmitting, to at least one second target central unit (CU) , a second handover request, wherein the at least one first target CU may be at least partially different from the at least one second target CU, whereinthe second handover request may comprise, at least, a request for a second group configuration that may comprise at least one full configuration for at least one second target cell that may be associated with at least one second central unit (CU) ; and receiving, from respective ones of the at least one second target CU, at least one second group configuration according to the second handover request, wherein the configuration transmitted to the user equipment may further comprise, at least, the at least one second group configuration.

[0220] The request for the group configuration may comprise a flag configured to indicate that a format of the first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0221] A radio resource control (RRC) reconfiguration message may comprise the configuration that may comprise, at least, the at least one received first group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0222] In accordance with one example embodiment, an apparatus may comprise: circuitry configured to perform: determining, with a source central unit (CU) , to cause switching of a serving cell of a user equipment; circuitry configured to perform: transmitting, to at least one first target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the firstgroup configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; circuitry configured to perform: receiving, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and circuitry configured to perform: transmitting, to the user equipment, a configuration that may comprise, at least, the at least one received first group configuration .

[0223] In accordance with one example embodiment, an apparatus may comprise: processing circuitry; memory circuitry including computer program code, the memory circuitry and the computer program code configured to, with the processing circuitry, enable the apparatus to: determine to cause switching of a serving cell of a user equipment; transmit, to at least one first target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; receive, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and transmit, to the user equipment, a1configuration that may comprise, at least, the at least one received first group configuration.

[0224] In accordance with one example embodiment, an apparatus may comprise means for: determining to cause switching of a serving cell of a user equipment; transmitting, to at least one first target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; receiving, from respective ones of the at least one first target CU, at least one first group configuration according to the handover request; and transmitting, to the user equipment, a configuration that may comprise, at least, the at least one received first group configuration.

[0225] The means may be further configured for: obtaining at least one capability of the user equipment, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, and / or a maximum number of reference configurations the user equipment can use; and determining whether to request, from the at least one first target CU, the first group configuration based, at least partially, on the at least one capability of the user equipment.

[0226] The means may be further configured for: transmitting, to at least one second target central unit (CU) , a second handoverrequest, wherein the at least one first target CU may be at least partially different from the at least one second target CU, wherein the second handover request may comprise, at least, a request for a second group configuration that may comprise at least one full configuration for at least one second target cell that may be associated with at least one second central unit (CU) ; and receiving, from respective ones of the at least one second target CU, at least one second group configuration according to the second handover request, wherein the configuration transmitted to the user equipment may further comprise, at least, the at least one second group configuration.

[0227] The request for the group configuration may comprise a flag configured to indicate that a format of the first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0228] A radio resource control (RRC) reconfiguration message may comprise the configuration that may comprise, at least, the at least one received first group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0229] In accordance with one example embodiment, a non- transitory computer-readable medium comprising instructions stored thereon which, when executed with at least one processor, cause the at least one processor to: determine to cause switching of a serving cell of a user equipment; cause transmitting, to at leastone first target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; cause receiving, from respective ones of the at least one first target CU, of at least one first group configuration according to the handover request; and cause transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one received first group configuration .

[0230] In accordance with one example embodiment, a non- transitory computer-readable medium comprising program instructions stored thereon for performing at least the following: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one first target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; causing receiving, from respective ones of the at least one first target CU, of at least one first group configuration according to the handover request; and causingtransmitting, to the user equipment, of a configuration that may comprise, at least, the at least one received first group configuration .

[0231] The example non-transitory computer-readable medium may further comprise program instructions stored thereon for performing: causing obtaining of at least one capability of the user equipment, wherein the at least one capability may comprise at least one of: a capability for using multiple reference configurations, and / or a maximum number of reference configurations the user equipment can use; and determining whether to request, from the at least one first target CU, the first group configuration based, at least partially, on the at least one capability of the user equipment.

[0232] The example non-transitory computer-readable medium may further comprise program instructions stored thereon for performing: causing transmitting, to at least one second target central unit (CU) , of a second handover request, wherein the at least one first target CU may be at least partially different from the at least one second target CU, wherein the second handover request may comprise, at least, a request for a second group configuration that may comprise at least one full configuration for at least one second target cell that may be associated with at least one second central unit (CU) ; and receiving, from respective ones of the at least one second target CU, at least one second group configuration according to the second handover request, wherein the configuration transmitted to the user equipment may further comprise, at least, the at least one second group configuration .

[0233] The request for the group configuration may comprise a flag configured to indicate that a format of the first group configuration may comprise the first reference configuration and the at least one first delta configuration.

[0234] A radio resource control (RRC) reconfiguration message may comprise the configuration that may comprise, at least, the at least one received first group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0235] In accordance with another example embodiment, a non- transitory program storage device readable by a machine may be provided, tangibly embodying instructions executable by the machine for performing operations, the operations comprising: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one first target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; causing receiving, from respective ones of the at least one first target CU, of at least one first group configuration according to the handover request; and causingtransmitting, to the user equipment, of a configuration that may comprise, at least, the at least one received first group configuration .

[0236] In accordance with another example embodiment, a non- transitory computer-readable medium comprising instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one first target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; causing receiving, from respective ones of the at least one first target CU, of at least one first group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one received first group configuration .

[0237] A computer implemented system comprising: at least one processor and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one first target central unit (CU) , of a handover request, wherein the handover request may comprise, atleast, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; causing receiving, from respective ones of the at least one first target CU, of at least one first group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one received first group configuration.

[0238] A computer implemented system comprising: means for determining to cause switching of a serving cell of a user equipment; means for causing transmitting, to at least one first target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a first group configuration, wherein the first group configuration may comprise, at least, a first reference configuration associated with a respective one of the at least one first target CU, and at least one first delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one first delta configuration may be defined based on the first reference configuration; means for causing receiving, from respective ones of the at least one first target CU, of at least one first group configuration according to the handover request; and means for causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one received first group configuration.

[0239] In accordance with one example embodiment, an apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells the apparatus provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generate the group configuration; and transmit, to the source CU, the group configuration.

[0240] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration may comprise the reference configuration and the at least one delta configuration.

[0241] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) comprising one or more Ll / 2 triggered mobility candidate information elements (IES) .

[0242] In accordance with one aspect, an example method may be provided comprising: receiving, with a target central unit (CU) from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells the target CU provides, and at least one delta configurationassociated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration .

[0243] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration may comprise the reference configuration and the at least one delta configuration.

[0244] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) comprising one or more Ll / 2 triggered mobility candidate information elements (IES) .

[0245] In accordance with one example embodiment, an apparatus may comprise: circuitry configured to perform: receiving, with a target central unit (CU) from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells the target CU provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; circuitry configured to perform: generating the group configuration; and circuitry configured to perform: transmitting, to the source CU, the group configuration .

[0246] In accordance with one example embodiment, an apparatus may comprise: processing circuitry; memory circuitry includingcomputer program code, the memory circuitry and the computer program code configured to, with the processing circuitry, enable the apparatus to: receive, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells the apparatus provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generate the group configuration; and transmit, to the source CU, the group configuration .

[0247] In accordance with one example embodiment, an apparatus may comprise means for: receiving, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration comprising a reference configuration associated with one or more target cells the apparatus provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration .

[0248] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration may comprise the reference configuration and the at least one delta configuration.

[0249] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) comprising one or more Ll / 2 triggered mobility candidate information elements (IES) .

[0250] In accordance with one example embodiment, a non- transitory computer-readable medium comprising instructions stored thereon which, when executed with at least one processor, cause the at least one processor to: cause receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells a target central unit (CU) provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generate the group configuration; and cause transmitting, to the source CU, of the group configuration.

[0251] In accordance with one example embodiment, a non- transitory computer-readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells a target central unit (CU) provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generating thegroup configuration; and causing transmitting, to the source CU, of the group configuration.

[0252] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration may comprise the reference configuration and the at least one delta configuration.

[0253] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) comprising one or more Ll / 2 triggered mobility candidate information elements (IES) .

[0254] In accordance with another example embodiment, a non- transitory program storage device readable by a machine may be provided, tangibly embodying instructions executable by the machine for performing operations, the operations comprising: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells a target central unit (CU) provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration.

[0255] In accordance with another example embodiment, a non- transitory computer-readable medium comprising instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: causing receiving, from a source central unit(CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells a target central unit (CU) provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration.

[0256] A computer implemented system comprising: at least one processor and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells a target central unit (CU) provides, and at least one delta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration.

[0257] A computer implemented system comprising: means for causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration that may comprise a reference configuration associated with one or more target cells a target central unit (CU) provides, and at least onedelta configuration associated with respective ones of the one or more target cell, wherein the at least one delta configuration may be defined based on the reference configuration; means for generating the group configuration; and means for causing transmitting, to the source CU, of the group configuration.

[0258] In accordance with one example embodiment, an apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0259] The example apparatus may be further configured to: obtain the source reference configuration; determine a reference configuration associated with the CU based, at least partially, on the delta reference configuration and the source reference configuration; and determine a configuration for a target cell, of the at least one target cell, based, at least partially, on the determined reference configuration and a delta configuration, ofthe at least one delta configuration, associated with the target cell .

[0260] The at least one group configuration may further comprise a flag configured to indicate that the delta reference configuration may be defined based on the source reference configuration .

[0261] The example apparatus may be further configured to: provide at least one capability of the apparatus, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the apparatus can use.

[0262] The at least one group configuration may comprise a flag configured to indicate that a format of the at least one group configuration may comprise the delta reference configuration and the at least one delta configuration.

[0263] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0264] In accordance with one aspect, an example method may be provided comprising: receiving, with a user equipment, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0265] The example method may further comprise: obtaining the source reference configuration; determining a reference configuration associated with the CU based, at least partially, on the delta reference configuration and the source reference configuration; and determining a configuration for a target cell, of the at least one target cell, based, at least partially, on the determined reference configuration and a delta configuration, of the at least one delta configuration, associated with the target cell .

[0266] The at least one group configuration may further comprise a flag configured to indicate that the delta reference configuration may be defined based on the source reference configuration .

[0267] The example method may further comprise: providing at least one capability of the apparatus, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the user equipment can use.

[0268] The at least one group configuration may comprise a flag configured to indicate that a format of the at least one group configuration may comprise the delta reference configuration and the at least one delta configuration.

[0269] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0270] In accordance with one example embodiment, an apparatus may comprise: circuitry configured to perform: receiving, with a user equipment, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configurationmay be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and circuitry configured to perform: performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0271] In accordance with one example embodiment, an apparatus may comprise: processing circuitry; memory circuitry including computer program code, the memory circuitry and the computer program code configured to, with the processing circuitry, enable the apparatus to: receive, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0272] In accordance with one example embodiment, an apparatus may comprise means for: receiving, from a source central unit (CU) , a configuration for switching from a serving cell the source CUprovides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that may be associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0273] The means may be further configured for: obtaining the source reference configuration; determining a reference configuration associated with the CU based, at least partially, on the delta reference configuration and the source reference configuration; and determining a configuration for a target cell, of the at least one target cell, based, at least partially, on the determined reference configuration and a delta configuration, of the at least one delta configuration, associated with the target cell .

[0274] The at least one group configuration may further comprise a flag configured to indicate that the delta reference configuration may be defined based on the source reference configuration .

[0275] The means may be further configured for: provide at least one capability of the apparatus, wherein the at least one capability may comprise at least one of : a capability for usingmultiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the apparatus can use.

[0276] The at least one group configuration may comprise a flag configured to indicate that a format of the at least one group configuration may comprise the delta reference configuration and the at least one delta configuration.

[0277] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units(CUs) .

[0278] In accordance with one example embodiment, a non- transitory computer-readable medium comprising instructions stored thereon which, when executed with at least one processor, cause the at least one processor to: cause receiving, from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a sourcereference configuration, and at least one delta configuration associated with at least one target cell that may be associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and perform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0279] In accordance with one example embodiment, a non- transitory computer-readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that may be associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0280] The example non- transitory computer-readable medium may further comprise program instructions stored thereon for performing: causing obtaining of the source reference configuration; determining a reference configuration associated with the CU based, at least partially, on the delta reference configuration and the source reference configuration; anddetermining a configuration for a target cell, of the at least one target cell, based, at least partially, on the determined reference configuration and a delta configuration, of the at least one delta configuration, associated with the target cell.

[0281] The at least one group configuration may further comprise a flag configured to indicate that the delta reference configuration may be defined based on the source reference configuration .

[0282] The example non- transitory computer-readable medium may further comprise program instructions stored thereon for performing: providing at least one capability of the user equipment, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the user equipment can use .

[0283] The at least one group configuration may comprise a flag configured to indicate that a format of the at least one group configuration may comprise the delta reference configuration and the at least one delta configuration.

[0284] A radio resource control (RRC) reconfiguration message may comprise the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurationsmay be respectively associated with different target central units(CUs) .

[0285] In accordance with another example embodiment, a non- transitory program storage device readable by a machine may be provided, tangibly embodying instructions executable by the machine for performing operations, the operations comprising: causing receiving, from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that may be associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0286] In accordance with another example embodiment, a non- transitory computer-readable medium comprising instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: causing receiving, from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein thedelta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that may be associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0287] A computer implemented system comprising: at least one processor and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: causing receiving, from a source central unit (CU) , of a configuration for switching from a serving cell the source CU provides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that may be associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration .

[0288] A computer implemented system comprising: means for causing receiving, from a source central unit (CU) , of a configuration for switching from a serving cell the source CUprovides, wherein the configuration may comprise, at least, at least one group configuration, wherein the at least one group configuration may comprise, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration may be defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that may be associated with the CU, wherein the at least one delta configuration may be defined based on the reference configuration associated with the CU; and means for performing switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

[0289] In accordance with one example embodiment, an apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine to cause switching of a serving cell of a user equipment; transmit, to at least one target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; receive, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmit, to the user equipment, aconfiguration comprising, at least, the at least one group configuration .

[0290] The example apparatus may be further configured to: obtain at least one capability of the user equipment, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the user equipment can use; and determine whether to request, from the at least one target CU, the group configuration based, at least partially, on the at least one capability of the user equipment.

[0291] The request for the group configuration may comprise a request for the reference configuration that may comprise the full reference configuration, wherein transmitting the configuration may comprise the example apparatus being further configured to: determine the delta reference configuration; and transmit, to the user equipment, the configuration that may comprise, at least, the at least one group configuration with, at least, the determined delta reference configuration.

[0292] The request for the group configuration may comprise a request for the reference configuration that may comprise the delta reference configuration defined based on the source reference configuration, wherein transmitting the configuration may comprise the example apparatus being further configured to: transmit, to the user equipment, the configuration that may comprise, at least, the at least one group configuration with, at least, the delta reference configuration.

[0293] The transmitted configuration may further comprise a flag configured to indicate that the at least one group configuration may comprise the delta reference configuration defined based on the source reference configuration.

[0294] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration that may comprise the reference configuration and the at least one delta configuration.

[0295] A radio resource control (RRC) reconfiguration message may comprise the configuration that may comprise, at least, the at least one group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0296] The source reference configuration may be at least one of: a reference configuration associated with the apparatus, or a reference configuration the apparatus selects.

[0297] In accordance with one aspect, an example method may be provided comprising: determining, with a source central unit (CU) , to cause switching of a serving cell of a user equipment; transmitting, to at least one target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of: a fullreference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; receiving, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmitting, to the user equipment, a configuration that may comprise, at least, the at least one group configuration .

[0298] The example method may further comprise: obtaining at least one capability of the user equipment, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the user equipment can use; and determining whether to request, from the at least one target CU, the group configuration based, at least partially, on the at least one capability of the user equipment.

[0299] The request for the group configuration may comprise a request for the reference configuration that may comprise the full reference configuration, wherein the transmitting of the configuration may comprise: determining the delta reference configuration; and transmitting, to the user equipment, the configuration that may comprise, at least, the at least one group configuration with, at least, the determined delta reference configuration .

[0300] The request for the group configuration may comprise a request for the reference configuration that may comprise the delta reference configuration defined based on the source reference configuration, wherein the transmitting of the configuration may comprise: transmitting, to the user equipment, the configuration comprising, at least, the at least one group configuration with, at least, the delta reference configuration.

[0301] The transmitted configuration may further comprise a flag configured to indicate that the at least one group configuration that may comprise the delta reference configuration defined based on the source reference configuration.

[0302] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration that may comprise the reference configuration and the at least one delta configuration.

[0303] A radio resource control (RRC) reconfiguration message may comprise the configuration comprising, at least, the at least one group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0304] The source reference configuration may be at least one of: a reference configuration associated with the source CU, or a reference configuration the source CU selects.

[0305] In accordance with one example embodiment, an apparatus may comprise: circuitry configured to perform: determining, with a source central unit (CU) , to cause switching of a serving cell of a user equipment; circuitry configured to perform: transmitting, to at least one target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; circuitry configured to perform: receiving, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and circuitry configured to perform: transmitting, to the user equipment, a configuration that may comprise, at least, the at least one group configuration .

[0306] In accordance with one example embodiment, an apparatus may comprise: processing circuitry; memory circuitry including computer program code, the memory circuitry and the computer program code configured to, with the processing circuitry, enable the apparatus to: determine to cause switching of a serving cell of a user equipment; transmit, to at least one target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise at least: a referenceconfiguration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; receive, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmit, to the user equipment, a configuration comprising, at least, the at least one group configuration .

[0307] In accordance with one example embodiment, an apparatus may comprise means for: determining to cause switching of a serving cell of a user equipment; transmitting, to at least one target central unit (CU) , a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; receiving, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmitting, to the user equipment, a configuration that may comprise, at least, the at least one group configuration .

[0308] The means may be further configured for: obtaining at least one capability of the user equipment, wherein the at least one capability may comprise at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the user equipment can use; and determining whether to request, from the at least one target CU, the group configuration based, at least partially, on the at least one capability of the user equipment.

[0309] The request for the group configuration may comprise a request for the reference configuration that may comprise the full reference configuration, wherein the means configured for transmitting the configuration may comprise means configured for: determining the delta reference configuration; and transmitting, to the user equipment, the configuration that may comprise, at least, the at least one group configuration with, at least, the determined delta reference configuration.

[0310] The request for the group configuration may comprise a request for the reference configuration that may comprise the delta reference configuration defined based on the source reference configuration, wherein the means configured for transmitting the configuration may comprise means configured for: transmitting, to the user equipment, the configuration that may comprise, at least, the at least one group configuration with, at least, the delta reference configuration.

[0311] The transmitted configuration may further comprise a flag configured to indicate that the at least one group configurationmay comprise the delta reference configuration defined based on the source reference configuration.

[0312] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration may comprise the reference configuration and the at least one delta configuration.

[0313] A radio resource control (RRC) reconfiguration message may comprise the configuration comprising, at least, the at least one group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0314] The source reference configuration may be at least one of: a reference configuration associated with the apparatus, or a reference configuration the apparatus selects.

[0315] In accordance with one example embodiment, a non- transitory computer-readable medium comprising instructions stored thereon which, when executed with at least one processor, cause the at least one processor to: determine to cause switching of a serving cell of a user equipment; cause transmitting, to at least one target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of: a full reference configuration, ora delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; cause receiving, from respective ones of the at least one target CU, of at least one group configuration according to the handover request; and cause transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one group configuration.

[0316] In accordance with one example embodiment, a non- transitory computer-readable medium comprising program instructions stored thereon for performing at least the following: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; causing receiving, from respective ones of the at least one target CU, of at least one group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one group configuration.

[0317] The example non-transitory computer-readable medium may further comprise program instructions stored thereon for performing: causing obtaining of at least one capability of the user equipment, wherein the at least one capability may comprise at least one of: a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the user equipment can use; and determining whether to request, from the at least one target CU, the group configuration based, at least partially, on the at least one capability of the user equipment.

[0318] The request for the group configuration may comprise a request for the reference configuration that may comprise the full reference configuration, wherein causing transmitting of the configuration may comprise the example non-transitory computer- readable medium further comprising program instructions stored thereon for performing: determining the delta reference configuration; and causing transmitting, to the user equipment, of the configuration that may comprise, at least, the at least one group configuration with, at least, the determined delta reference configuration .

[0319] The request for the group configuration may comprise a request for the reference configuration that may comprise the delta reference configuration defined based on the source reference configuration, wherein causing transmitting of the configuration may comprise the example non-transitory computer-readable medium further comprising program instructions stored thereon for performing: causing transmitting, to the user equipment, of theconfiguration that may comprise, at least, the at least one group configuration with, at least, the delta reference configuration.

[0320] The transmitted configuration may further comprise a flag configured to indicate that the at least one group configuration may comprise the delta reference configuration defined based on the source reference configuration.

[0321] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration may comprise the reference configuration and the at least one delta configuration.

[0322] A radio resource control (RRC) reconfiguration message may comprise the configuration that may comprise, at least, the at least one group configuration, wherein the configuration may comprise a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration may comprise a plurality of group configurations, wherein respective ones of the plurality of group configurations may be respectively associated with different target central units (CUs) .

[0323] The source reference configuration may be at least one of : a reference configuration associated with a source central unit (CU) , or a reference configuration the source CU selects.

[0324] In accordance with another example embodiment, a non- transitory program storage device readable by a machine may be provided, tangibly embodying instructions executable by the machine for performing operations, the operations comprising: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one target centralunit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; causing receiving, from respective ones of the at least one target CU, of at least one group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one group configuration.

[0325] In accordance with another example embodiment, a non- transitory computer-readable medium comprising instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on thefull reference configuration; causing receiving, from respective ones of the at least one target CU, of at least one group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one group configuration.

[0326] A computer implemented system comprising: at least one processor and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: determining to cause switching of a serving cell of a user equipment; causing transmitting, to at least one target central unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; causing receiving, from respective ones of the at least one target CU, of at least one group configuration according to the handover request; and causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one group configuration.

[0327] A computer implemented system comprising: means for determining to cause switching of a serving cell of a user equipment; means for causing transmitting, to at least one targetIllcentral unit (CU) , of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration may comprise at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration may be defined based on the full reference configuration; means for causing receiving, from respective ones of the at least one target CU, of at least one group configuration according to the handover request; and means for causing transmitting, to the user equipment, of a configuration that may comprise, at least, the at least one group configuration.

[0328] In accordance with one example embodiment, an apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with the apparatus, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the apparatus provides, wherein the at least one delta configuration may be defined based on thefull reference configuration; generate the group configuration; and transmit, to the source CU, the group configuration.

[0329] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration that may comprise the reference configuration and the at least one delta configuration.

[0330] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) that may comprise one or more Ll / 2 triggered mobility candidate information elements ( IES ) .

[0331] The request for the group configuration may comprise a request for the reference configuration that may comprise delta reference configuration, wherein generating the group configuration may comprise the example apparatus being further configured to: determine the full reference configuration; determine the delta reference configuration based, at least partially, on the full reference configuration and the source reference configuration; and include the delta reference configuration and the at least one delta reference configuration in the group configuration.

[0332] The handover request may further comprise the source reference configuration.

[0333] In accordance with one aspect, an example method may be provided comprising: receiving, with a target central unit (CU) from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the groupconfiguration may comprise, at least: a reference configuration associated with the target CU, wherein the reference configuration may comprise at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration .

[0334] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration that may comprise the reference configuration and the at least one delta configuration.

[0335] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) that may comprise one or more Ll / 2 triggered mobility candidate information elements ( IES ) .

[0336] The request for the group configuration may comprise a request for the reference configuration that may comprise the delta reference configuration, wherein the generating of the group configuration may comprise: determining the full reference configuration; determining the delta reference configuration based, at least partially, on the full reference configuration and the source reference configuration; and including the delta reference configuration and the at least one delta reference configuration in the group configuration.

[0337] The handover request may further comprise the source reference configuration.

[0338] In accordance with one example embodiment, an apparatus may comprise: circuitry configured to perform: receiving, with a target central unit (CU) from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with the target CU, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; circuitry configured to perform: generating the group configuration; and circuitry configured to perform: transmitting, to the source CU, the group configuration.

[0339] In accordance with one example embodiment, an apparatus may comprise: processing circuitry; memory circuitry including computer program code, the memory circuitry and the computer program code configured to, with the processing circuitry, enable the apparatus to: receive, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with the apparatus, wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based ona source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the apparatus provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generate the group configuration; and transmit, to the source CU, the group configuration.

[0340] In accordance with one example embodiment, an apparatus may comprise means for: receiving, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with the apparatus, wherein the reference configuration may comprise at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the apparatus provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generating the group configuration; and transmitting, to the source CU, the group configuration.

[0341] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration that may comprise the reference configuration and the at least one delta configuration.

[0342] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) that may comprise one or more Ll / 2 triggered mobility candidate information elements ( IES ) .

[0343] The request for the group configuration may comprise a request for the reference configuration that may comprise the delta reference configuration, wherein the means configured for generating the group configuration may comprise means configured for: determining the full reference configuration; determining the delta reference configuration based, at least partially, on the full reference configuration and the source reference configuration; and including the delta reference configuration and the at least one delta reference configuration in the group configuration .

[0344] The handover request may further comprise the source reference configuration.

[0345] In accordance with one example embodiment, a non- transitory computer-readable medium comprising instructions stored thereon which, when executed with at least one processor, cause the at least one processor to: cause receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a target central unit (CU) , wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generate the group configuration; and cause transmitting, to the source CU, of the group configuration.10346] In accordance with one example embodiment, a non- transitory computer-readable medium comprising program instructions stored thereon for performing at least the following: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a target central unit (CU) , wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration.

[0347] The request for the group configuration may comprise a flag configured to indicate that a format of the group configuration that may comprise the reference configuration and the at least one delta configuration.

[0348] The group configuration may comprise an Ll / 2 triggered mobility configuration group information element (IE) that may comprise one or more Ll / 2 triggered mobility candidate information elements ( IES ) .

[0349] The request for the group configuration may comprise a request for the reference configuration that may comprise the delta reference configuration, wherein generating the group configuration may comprise the example non-transitory computer-readable medium further comprising program instructions stored thereon for performing: determining the full reference configuration; determining the delta reference configuration based, at least partially, on the full reference configuration and the source reference configuration; and including the delta reference configuration and the at least one delta reference configuration in the group configuration.

[0350] The handover request may further comprise the source reference configuration.

[0351] In accordance with another example embodiment, a non- transitory program storage device readable by a machine may be provided, tangibly embodying instructions executable by the machine for performing operations, the operations comprising: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a target central unit (CU) , wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration.

[0352] In accordance with another example embodiment, a non- transitory computer-readable medium comprising instructions that,when executed by an apparatus, cause the apparatus to perform at least the following: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a target central unit (CU) , wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generating the group configuration; and causing transmitting, to the source CU, of the group configuration .

[0353] A computer implemented system comprising: at least one processor and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a target central unit (CU) , wherein the reference configuration may comprise at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; generating thegroup configuration; and causing transmitting, to the source CU of the group configuration.

[0354] A computer implemented system comprising: means for causing receiving, from a source central unit (CU) serving a user equipment, of a handover request, wherein the handover request may comprise, at least, a request for a group configuration, wherein the group configuration may comprise, at least: a reference configuration associated with a target central unit (CU) , wherein the reference configuration may comprise at least one of : a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the target CU provides, wherein the at least one delta configuration may be defined based on the full reference configuration; means for generating the group configuration; and means for causing transmitting, to the source CU, of the group configuration .

[0355] The term "non-transi tory, " as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. , RAM vs. ROM) .

[0356] It should be understood that the foregoing description is only illustrative. Various alternatives and modifications can be devised by those skilled in the art. For example, features recited in the various dependent claims could be combined with each other in any suitable combination ( s ) . In addition, features from different embodiments described above could be selectively combined into a new embodiment. Accordingly, the description isintended to embrace all such alternatives, modification and variances which fall within the scope of the appended claims.

Claims

CLAIMSWhat is claimed is:

1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) , a configuration for switching from a serving cell the source CU provides, wherein the configuration comprises, at least, at least one group configuration, wherein the at least one group configuration comprises, at least: a delta reference configuration associated with a central unit (CU) , wherein the delta reference configuration is defined based on a reference configuration associated with the CU and a source reference configuration, and at least one delta configuration associated with at least one target cell that is associated with the CU, wherein the at least one delta configuration is defined based on the reference configuration associated with the CU; andperform switching from the serving cell to a target cell based, at least partially, on at least part of the configuration.

2. The apparatus of claim 1, wherein the at least one group configuration further comprises a flag configured to indicate that the delta reference configuration is defined based on the source reference configuration.

3. The apparatus of claim 1 or 2, wherein the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to: provide at least one capability of the apparatus, wherein the at least one capability comprises at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the apparatus can use.

4. The apparatus of any of claims 1 through 3, wherein a radio resource control (RRC) reconfiguration message comprises the configuration for switching from the serving cell, wherein the configuration for switching from the serving cell comprises a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration for switching from the serving cell comprises a plurality of group configurations, wherein respective ones of the plurality of group configurations are respectively associated with different target central units (CUs) .. An apparatus comprising: at least one processor; and at least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine to cause switching of a serving cell of a user equipment; transmit, to at least one target central unit (CU) , a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with a respective one of the at least one target CU, wherein the reference configuration comprises at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration ; and at least one delta configuration for at least one target cell associated with the at least one target CU, wherein the at least one delta configuration is defined based on the full reference configuration;receive, from respective ones of the at least one target CU, at least one group configuration according to the handover request; and transmit, to the user equipment, a configuration comprising, at least, the at least one group configuration .

6. The apparatus of claim 5, wherein the at least one memory stores instructions that, when executed by the at least one processor, cause the apparatus to: obtain at least one capability of the user equipment, wherein the at least one capability comprises at least one of : a capability for using multiple reference configurations, a capability for determining a reference configuration from a delta reference configuration, and / or a maximum number of reference configurations the user equipment can use; and determine whether to request, from the at least one target CU, the group configuration based, at least partially, on the at least one capability of the user equipment .

7. The apparatus of claim 5 or 6, wherein the request for the group configuration comprises a request for the reference configuration comprising the full reference configuration, wherein transmitting the configuration comprises the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to: determine the delta reference configuration; andtransmit, to the user equipment, the configuration comprising, at least, the at least one group configuration with, at least, the determined delta reference configuration.

8. The apparatus of claim 7, wherein the transmitted configuration further comprises a flag configured to indicate that the at least one group configuration comprises the delta reference configuration defined based on the source reference configuration .

9. The apparatus of any of claims 5 through 8, wherein a radio resource control (RRC) reconfiguration message comprises the configuration comprising, at least, the at least one group configuration, wherein the configuration comprises a Ll / 2 triggered mobility configuration information element (IE) , wherein the configuration comprises a plurality of group configurations, wherein respective ones of the plurality of group configurations are respectively associated with different target central units (CUs) .

10. The apparatus of any of claims 5 through 9, wherein the source reference configuration is at least one of: a reference configuration associated with the apparatus, or a reference configuration the apparatus selects.

11. An apparatus comprising: at least one processor; andat least one non-transitory memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, from a source central unit (CU) serving a user equipment, a handover request, wherein the handover request comprises, at least, a request for a group configuration, wherein the group configuration comprises, at least: a reference configuration associated with the apparatus, wherein the reference configuration comprises at least one of: a full reference configuration, or a delta reference configuration defined based on a source reference configuration; and at least one delta configuration associated with respective ones of one or more target cells the apparatus provides, wherein the at least one delta configuration is defined based on the full reference configuration ; generate the group configuration; and transmit, to the source CU, the group configuration .

12. The apparatus of claim 11, wherein the request for the group configuration comprises a flag configured to indicate that a format of the group configuration comprises the reference configuration and the at least one delta configuration .

13. The apparatus of claim 11 or 12, wherein the group configuration comprises an Ll / 2 triggered mobility configuration group information element (IE) comprising one or more Ll / 2 triggered mobility candidate information elements ( IES ) .

14. The apparatus of any of claims 11 through 13, wherein the request for the group configuration comprises a request for the reference configuration comprising the delta reference configuration, wherein generating the group configuration comprises the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to: determine the full reference configuration; determine the delta reference configuration based, at least partially, on the full reference configuration and the source reference configuration; and include the delta reference configuration and the at least one delta reference configuration in the group configuration .

15. The apparatus of claim 14, wherein the handover request further comprises the source reference configuration.

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