Transfer of control plane

Abstract

An apparatus comprising means for: transmitting a request towards a second radio access network – control plane, RAN-CP, to transfer a user equipment, UE, context and logical termination of the UE control plane, CP, from a first RAN-CP to the second RAN-CP; transmitting information towards at least one core node to inform the at least one core node of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP towards the second RAN-CP; and transmitting information towards a source distributed unit, DU, associated with the UE to inform the source DU of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

Description

[0001] TITLE

[0002] TRANSFER OF CONTROL PLANE

[0003] TECHNOLOGICAL FIELD

[0004] Examples of the disclosure relate to transfer of control plane. Some relate to transfer of user equipment control plane in a wireless network.

[0005] BACKGROUND

[0006] A wireless network comprises a plurality of network nodes including terminal nodes and access nodes. Communication between the terminal nodes and access nodes is wireless.

[0007] The control plane of a terminal node can be transferred in the wireless network. For example, during inter gNB Handover in 5G, the control plane of the UE is transferred from the source gNB to the target gNB. In some circumstances it may be desirable to improve or enhance transfer of control plane in a wireless network.

[0008] BRIEF SUMMARY

[0009] According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: transmitting a request towards a second radio access network - control plane, RAN-CP, to transfer a user equipment, UE, context and logical termination of the UE control plane, CP, from a first RAN-CP to the second RAN-CP; transmitting information towards at least one core node to inform the at least one core node of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP towards the second RAN-CP; and transmitting information towards a source distributed unit, DU, associated with the UE to inform the source DU of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP. In some examples, the means are configured to: receive an acknowledgement from the source DU; and transmit transfer complete information towards the second RAN-CP.

[0010] In some examples, the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

[0011] In some examples, the means are configured to: after transmitting the request towards the second RAN-CP and prior to transmitting the transfer complete information towards the second RAN-CP, forward at least one received message towards the second RAN-CP.

[0012] In some examples, the means are configured to: after transmitting the request towards the second RAN-CP, receive at least one message; determine whether a transfer confirmation has been received from the second RAN-CP; and in response to determining that a transfer confirmation has not been received from the second RAN-CP, store the at least one received message.

[0013] In some examples, the means are configured to: receive a transfer confirmation from the second RAN-CP and delete any stored messages based, at least in part, on receiving the transfer confirmation.

[0014] In some examples, the means are configured to: receive a transfer confirmation from the second RAN-CP, wherein at least one of: transmitting information towards at least one core node to inform the at least one core node of the transfer is based, at least in part, on receiving the transfer confirmation; and transmitting information towards a source DU associated with the UE to inform the source DU of the transfer is based, at least in part, on receiving the transfer confirmation. In some examples, at least a portion of the transfer complete information is received with the acknowledgement from the source DU.

[0015] In some examples, the apparatus comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the apparatus.

[0016] According to various, but not necessarily all, embodiments there is provided a method comprising: transmitting a request towards a second RAN-CP to transfer a UE context and logical termination of the UE CP from a first RAN-CP to the second RAN-CP; transmitting information towards at least one core node to inform the at least one core node of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP; and transmitting information towards a source distributed unit, DU, associated with the UE to inform the source DU of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

[0017] In some examples, the method comprises: receiving an acknowledgement from the source DU; and transmitting transfer complete information towards the second RAN-CP.

[0018] In some examples, the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

[0019] In some examples, the method comprises: after transmitting the request towards the second RAN-CP and prior to transmitting the transfer complete information towards the second RAN-CP, forwarding at least one received message towards the second RAN-CP.

[0020] In some examples, the method comprises: after transmitting the request towards the second RAN-CP, receiving at least one message; determining whether a transfer confirmation has been received from the second RAN-CP; and in response to determining that a transfer confirmation has not been received from the second RAN-CP, store the at least one received message.

[0021] In some examples, the method comprises: receiving a transfer confirmation from the second RAN-CP and deleting any stored messages based, at least in part, on receiving the transfer confirmation.

[0022] In some examples, the method comprises: receiving a transfer confirmation from the second RAN-CP, wherein at least one of: transmitting information towards at least one core node to inform the at least one core node of the transfer is based, at least in part, on receiving the transfer confirmation; and transmitting information towards a source DU associated with the UE to inform the source DU of the transfer is based, at least in part, on receiving the transfer confirmation.

[0023] In some examples, at least a portion of the transfer complete information is received with the acknowledgement from the source DU.

[0024] According to various, but not necessarily all, embodiments there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: transmitting a request towards a second RAN-CP to transfer a UE context and logical termination of the UE CP from a first RAN-CP to the second RAN-CP; transmitting information towards at least one core node to inform the at least one core node of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP; and transmitting information towards a source distributed unit, DU, associated with the UE to inform the source DU of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

[0025] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving an acknowledgement from the source DU; and transmitting transfer complete information towards the second RAN-CP.

[0026] In some examples, the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

[0027] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: after transmitting the request towards the second RAN-CP and prior to transmitting the transfer complete information towards the second RAN-CP, forwarding at least one received message towards the second RAN-CP.

[0028] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: after transmitting the request towards the second RAN-CP, receiving at least one message; determining whether a transfer confirmation has been received from the second RAN-CP; and if it is determined that a transfer confirmation has not been received from the second RAN-CP, store the at least one received message.

[0029] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a transfer confirmation from the second RAN-CP and deleting any stored messages based, at least in part, on receiving the transfer confirmation.

[0030] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a transfer confirmation from the second RAN-CP, wherein at least one of: transmitting information towards at least one core node to inform the at least one core node of the transfer is based, at least in part, on receiving the transfer confirmation; and transmitting information towards a source DU associated with the UE to inform the source DU of the transfer is based, at least in part, on receiving the transfer confirmation.

[0031] In some examples, at least a portion of the transfer complete information is received with the acknowledgement from the source DU.

[0032] According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: receiving a request from a first RAN-CP to transfer a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP; determining whether to accept transfer of the UE context and logical termination of the UE CP; and in response to determining to accept transfer of the UE context and logical termination of the UE CP, transmitting a transfer confirmation towards the first RAN- CP.

[0033] In some examples, the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

[0034] In some examples, the means are configured to: receive at least one forwarded message from the first RAN-CP; determine whether transfer complete information has been received; and in response to determining that transfer complete information has not been received, storing the at least one forwarded message.

[0035] In some examples, the means are configured to: transmit relocation information towards the UE to inform the UE of the transfer of the UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP.

[0036] In some examples, the means are configured to: receive a request for the UE context from a third RAN-CP; and transmit the UE context towards the third RAN-CP.

[0037] According to various, but not necessarily all, embodiments there is provided a method comprising: receiving a request from a first RAN-CP to transfer a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP; determining whether to accept transfer of the UE context and logical termination of the UE CP; and in response to determining to accept transfer of the UE context and logical termination of the UE CP, transmitting a transfer confirmation towards the first RAN- CP.

[0038] In some examples, the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

[0039] In some examples, the method comprises: receiving at least one forwarded message from the first RAN-CP; determining whether transfer complete information has been received; and in response to determining that transfer complete information has not been received, storing the at least one forwarded message.

[0040] In some examples, the method comprises: transmitting relocation information towards the UE to inform the UE of the transfer of the UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP.

[0041] In some examples, the method comprises: receiving a request for the UE context from a third RAN-CP; and transmitting the UE context towards the third RAN-CP.

[0042] According to various, but not necessarily all, embodiments there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a request from a first RAN-CP to transfer a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP; determining whether to accept transfer of the UE context and logical termination of the UE CP; and in response to determining to accept transfer of the UE context and logical termination of the UE CP, transmitting a transfer confirmation towards the first RAN- CP.

[0043] In some examples, the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

[0044] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving at least one forwarded message from the first RAN-CP; determining whether transfer complete information has been received; and in response to determining that transfer complete information has not been received, storing the at least one forwarded message.

[0045] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: transmitting relocation information towards the UE to inform the UE of the transfer of the UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP.

[0046] In some examples, the computer program comprises instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a request for the UE context from a third RAN-CP; and transmitting the UE context towards the third RAN-CP. According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: receiving information indicating a transfer of a UE context and logical termination of the UE control plane from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement towards the first RAN-CP; and updating routing information based, at least in part, on the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

[0047] In some examples, the acknowledgement comprises transfer complete information.

[0048] According to various, but not necessarily all, embodiments there is provided a method comprising: receiving information indicating a transfer of a UE context and logical termination of the UE control plane from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement towards the first RAN-CP; and updating routing information based, at least in part, on the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

[0049] In some examples, the acknowledgement comprises transfer complete information.

[0050] According to various, but not necessarily all, embodiments there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving information indicating a transfer of a UE context and logical termination of the UE control plane from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement towards the first RAN-CP; and updating routing information based, at least in part, on the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

[0051] In some examples, the acknowledgement comprises transfer complete information. According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: receiving relocation information indicating a transfer of a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP; determining that radio link failure has occurred at the UE; and transmitting a re-establishment request towards a third RAN-CP, wherein the re-establishment request comprises an identifier of the second RAN-CP.

[0052] According to various, but not necessarily all, embodiments there is provided a method comprising: receiving relocation information indicating a transfer of a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP; determining that radio link failure has occurred at the UE; and transmitting a re-establishment request towards a third RAN-CP, wherein the re-establishment request comprises an identifier of the second RAN-CP.

[0053] According to various, but not necessarily all, embodiments there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving relocation information indicating a transfer of a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP; determining that radio link failure has occurred at the UE; and transmitting a re-establishment request towards a third RAN-CP, wherein the re-establishment request comprises an identifier of the second RAN-CP.

[0054] According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for: receiving a re-establishment request from a UE, wherein the re-establishment request comprises an identifier of a last RAN-CP of the UE; transmitting a request for UE context towards the RAN-CP identified by the identifier; and receiving the UE context from the RAN-CP identified by the identifier.

[0055] According to various, but not necessarily all, embodiments there is provided a method comprising: receiving a re-establishment request from a UE, wherein the re-establishment request comprises an identifier of a last RAN-CP of the UE; transmitting a request for UE context towards the RAN-CP identified by the identifier; and receiving the UE context from the RAN-CP identified by the identifier.

[0056] According to various, but not necessarily all, embodiments there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a re-establishment request from a UE, wherein the re-establishment request comprises an identifier of a last RAN-CP of the UE; transmitting a request for UE context towards the RAN-CP identified by the identifier; and receiving the UE context from the RAN-CP identified by the identifier.

[0057] According to various, but not necessarily all, examples there is provided examples as claimed in the appended claims.

[0058] According to various, but not necessarily all, embodiments there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform at least a part of one or more methods described herein. According to various, but not necessarily all, embodiments there is provided an apparatus comprising means for performing at least part of one or more methods described herein.

[0059] The description of a function and / or action should additionally be considered to also disclose any means suitable for performing that function and / or action.

[0060] Functions and / or actions described herein can be performed in any suitable way using any suitable method.

[0061] While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all of the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all of the features, in any combination, may be implemented by / comprised in / performable by an apparatus, a method, and / or computer program instructions as desired, and as appropriate.

[0062] BRIEF DESCRIPTION

[0063] Some examples will now be described with reference to the accompanying drawings in which:

[0064] FIG. 1 shows an example of a network architecture of a communication system; FIG. 2 shows an example of a network architecture of a communication system;

[0065] FIG. 3 shows an example of signaling between entities;

[0066] FIG. 4 shows an example of a flowchart of a method;

[0067] FIG. 5 shows an example of a flowchart of a method;

[0068] FIG. 6 shows an example of a flowchart of a method;

[0069] FIG. 7 shows an example of a flowchart of a method;

[0070] FIG. 8 shows an example of a flowchart of a method;

[0071] FIG. 9 shows an example of signaling between entities;

[0072] FIG. 10A shows an example of a block diagram of an apparatus; and FIG. 10B shows an example of a memory. The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

[0073] DETAILED DESCRIPTION

[0074] FIG 1 illustrates an example of a network 100 comprising a plurality of network nodes including terminal nodes 110, access nodes 120 and one or more core nodes 129.

[0075] The terminal nodes 110 and access nodes 120 communicate with each other. The one or more core nodes 129 communicate with the access nodes 120.

[0076] The network 100 is in this example a radio telecommunications network, in which at least some of the terminal nodes 110 and access nodes 120 communicate with each other using transmission / reception of radio waves / signals.

[0077] The one or more core nodes 129 may, in some examples, communicate with each other. The one or more access nodes 120 may, in some examples, communicate with each other.

[0078] The network 100 may be a cellular network comprising a plurality of cells 122 each served by an access node 120. In this example, the interface between the terminal nodes 110 and an access node 120 defining a cell 122 is a wireless interface 124.

[0079] The access node 120 is a cellular radio transceiver. The terminal nodes 110 are cellular radio transceivers.

[0080] In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal nodes 110 are user equipment 46 (UE), see, for example, FIG. 3, and the access nodes 120 are base stations. In examples the network 100 is an Evolved Universal Terrestrial Radio Access network (E-UTRAN). The E-UTRAN consists of E-UTRAN NodeBs (eNBs) 120, providing the E-UTRA user plane and control plane (RRC) protocol terminations towards the UE. The eNBs 120 are interconnected with each other by means of an X2 interface 126. The eNBs are also connected by means of the S1 interface 128 to the Mobility Management Entity (MME) 129.

[0081] In other examples the network 100 is a Next Generation (or New Radio, NR) Radio Access network (NG-RAN). The NG-RAN consists of gNodeBs (gNBs) 120, providing the user plane and control plane (RRC) protocol terminations towards the UE 110. The gNBs 120 are interconnected with each other by means of an Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the Access and Mobility management Function (AMF).

[0082] A user equipment 130 (UE) can comprise a mobile equipment. Where reference is made to user equipment that reference includes and encompasses, wherever possible, a reference to mobile equipment.

[0083] In examples, the network 100 can comprise a combination of E-UTRAN and NG-RAN.

[0084] In examples, the network 100 can comprise a 6GRAN network.

[0085] In NR, RAN control plane (CP) functionalities and protocols which include procedures related to the management of the cells and UEs inside these cells reside in gNBs. In examples, these functionalities can be disaggregated into two logical nodes, which in 5G are the central unit (CU) and the distributed unit (DU), wherein most of the CP functionalities reside inside the gNB-CU.

[0086] In examples, the network 100 can comprise CP entities in the form of Radio Access Network Control Planes (RAN-CPs) instances, which can be referred to as RAN-CPs. In 5G RAN-CP can refer to gNB-CU-CP and in 6G RAN-CP can refer to 6NB-CU-CP. In examples, a RAN-CP is a logical node in Radio Access Network (RAN) hosting the Radio Resource Control (RRC) and the control plane part of the Packet Data Convergence Protocol (PDCP) layer of the radio access protocol.

[0087] A reference to a RAN-CP can be considered a reference to an apparatus / device configured to operate / function as a RAN-CP and / or operating / functioning as a RAN- CP.

[0088] In some examples, there is an M:N cardinality between CP entities and Dlls. See, for example, FIG. 2.

[0089] FIG. 2 illustrates an example of an architecture 48, comprising an M:N cardinality between CP entities (denoted as RAN-CPs 12 in the example of FIG. 2) and the Dlls 24, so that a DU 24 can be connected to a plurality of RAN-CPs 12 enabling flexibility with regard to choice of which RAN-CP 12 should be responsible for UE CP handling such as mobility procedures, connection with the network, and UE context.

[0090] In examples, a source RAN-CP of a UE can determine that the UE context and logical termination of the UE CP should be transferred to a different RAN-CP, due to RAN-CP capacity and / or RAN-CP capabilities for example, and can initiate transfer of the UE context and logical termination of the UE CP to a different RAN-CP.

[0091] In examples, transfer of the UE context and logical termination of the UE CP can happen without any mobility / handover and Random Access Channel (RACH) procedures.

[0092] In examples, transfer of the UE context and logical termination of the UE CP can happen while the UE is in Radio Resource Control Connected (RRC Connected) state and while the UE remains in RRC Connected state.

[0093] Examples of the disclosure relate to apparatuses, methods, and / or computer programs for and / or involved in change of RAN-CPs. Examples of the disclosure relate to apparatuses, methods, and / or computer programs for and / or involved in transfer of UE context and logical termination of the UE CP.

[0094] FIG. 3 illustrates an example of signaling between entities. FIG. 3 also illustrates an example of a method 300.

[0095] In examples, FIG. 3 can be considered to illustrate a plurality of methods. For example, FIG. 3 illustrates one or more actions at a plurality of actors / entities and, in examples, FIG. 3 can be considered to illustrate a plurality of methods performed by the individual actors / entities.

[0096] One or more of the features discussed in relation to FIG. 3 can be found in one or more of the other FIGs.

[0097] In the example of FIG. 3, a plurality of apparatuses transmit and / or receive one or more signals and / or messages across and / or via and / or using a network. In examples, any suitable form of communication in any suitable network can be used. For example, at least a portion of the network 100 of FIG. 1 can be used.

[0098] Accordingly, in examples, the plurality of apparatuses in FIG. 2 form at least a portion of network 100 as described in relation to FIG. 1.

[0099] In the illustrated example, a terminal node 110, which in the example of FIG. 3 is a UE 46, a source DU 24, a first RAN-CP 12A, a second RAN-CP 12B, a third RAN-CP 12C, and a core node 129 transmit and / or receive one or more signals and / or one or more messages.

[0100] In examples, communications and / or transmissions between entities illustrated in FIG. 3 can proceed via any number of intervening entities, including no intervening entities.

[0101] Although one terminal node 110 is illustrated in the example of FIG. 3, in examples any suitable number of terminal nodes 110, for example UE 46, can be included. Similarly, any suitable number of DUs 24, RAN-CPs 12 and / or core nodes 129 can be included. As used herein, a description of a function and / or action should also be considered to disclose enabling, and / or causing, and / or controlling that function and / or action. For example, description of transmitting information should also be considered to disclose enabling, and / or causing, and / or controlling transmitting / transmission of information.

[0102] For example, a description of an apparatus, such as a UE 46, transmitting information should also be considered to disclose at least one controller of the apparatus enabling, and / or causing, and / or controlling the apparatus to transmit the information.

[0103] The above paragraphs concerning FIG. 3 can apply similarly to FIG. 9.

[0104] In examples, method 300 and / or at least a part of method 300 can be considered a method of changing RAN-CPs.

[0105] In examples, method 300 and / or at least a part of method 300 can be considered a method of transferring UE context and logical termination of the UE CP.

[0106] In examples, method 300 and / or at least a part of method 300 can be considered a method of transferring UE context and logical termination of the UE CP while the UE is in Radio Resource Control Connected (RRC Connected) state and while the UE remains in RRC Connected state.

[0107] In examples, method 300 and / or at least a part of method 300 can be considered a method of transferring UE context and logical termination of the UE CP without any mobility / handover and Random Access Channel (RACH) procedures.

[0108] In the illustrated example, the location of blocks indicates the entity or entities performing the function(s) and / or action(s). For example, block 302 is performed by the first RAN-CP 12A.

[0109] At block 302, method 300 comprises determining that a UE context 14 and logical termination of the UE CP 16 should be transferred from a first RAN-CP 12A to a second RAN-CP 12B. Block 302 can be performed based, at least in part, on any suitable information.

[0110] For example, block 302 can be performed based, at least in part, on any suitable information regarding at least one of the UE 46, the source DU 24, the first RAN-CP 12A, and at least one prospective RAN-CP 12, for example the second and / or third RAN-CP 12B, 12C.

[0111] A prospective RAN-CP can be considered a RAN-CP to which the UE context 14 and logical termination of the UE CP 16 could be transferred, for example the second and third RAN-CPs 12B, 12C in the example of FIG. 3.

[0112] In examples, block 302 can be performed based, at least in part on, at least one of: load information of the first RAN-CP 12A, load information of at least one prospective RAN-CP, the cell or cells the first RAN-CP 12A is currently serving, the cell or cells at least one prospective RAN-CP is currently serving, a network slice of a UE, a class of a UE, a type of a UE, UE network slice or class requirements, types, classes or slices of UE supported by the first RAN-CP 12A, types, classes or slices of UE supported by at least one prospective RAN-CP, location information of the first RAN-CP 12A, location information of at least one prospective RAN-CP, capacity information of the first RAN-CP 12A, capacity information of at least one prospective RAN-CP, location information of a UE, latency information of the first RAN-CP 12A, latency information of at least one prospective RAN-CP, latency information of a UE and so on.

[0113] In examples, the first RAN-CP 12 determines that a different RAN-CP is better for the UE 46, and determines to transfer UE context 14 and the logical termination of the UE CP 16 to a different RAN-CP 12.

[0114] In the illustrated example, at block 302, the first RAN-CP 12A has determined that UE context 14 and logical termination of the UE CP 16 should be transferred to the second RAN-CP 12B. In different circumstances, the first RAN-CP 12A could determine that UE context 14 and logical termination of the UE CP 16 should be transferred to the third RAN-CP 12C, for example. In some examples UE context 14 is UE context information. In some examples, UE context 14 is UE RRC context.

[0115] In some examples, UE context 14 comprises parameters which enable a UE to communicate inside a RAN.

[0116] In some examples, UE context 14 can comprise information as defined in TS 38.423, clause 9.1.1.1.

[0117] In examples, logical termination of the UE CP 16 can be considered a transfer of responsibility for / control of the UE CP. For example, logical termination of the UE CP 16 can comprise transfer of the responsibility for / control of the UE RRC functionality.

[0118] At block 304, method 300 comprises transmitting a request 10 towards the second RAN-CP 12B to transfer the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0119] As FIG. 3 illustrates one or more functions / actions of transmitting, FIG. 3 also illustrates the corresponding receiving and / or causing / enabling transmitting function(s) / action(s). For example, from the point of view of the second RAN-CP 12B, at block 304, method 300 comprises receiving a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0120] The request 10 can have any suitable form and / or can comprise any suitable information. For example, the request 10 can have any suitable form and / or can comprise any suitable information to request a transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0121] In some examples, block 304 comprises transmitting a UE Relocation Request message towards the second RAN-CP 12B.

[0122] In some examples, the request 10 to transfer the UE context 14 and logical termination of the UE CP 16 to the second RAN-CP comprises the UE context 14. At block 306, method 300 comprises determining whether to accept transfer of the UE context 14 and logical termination of the UE CP 16.

[0123] Block 306 can be performed based, at least in part, on any suitable information. For example, block 306 can be performed based, at least in part, capability, and / or capacity, and / or requirement information of the UE and / or second RAN-CP 12B.

[0124] In some examples, block 306 is performed based, at least in part, on UE CP requirements, UE capability and / or capacity of the second RAN-CP 12B. For example, at block 306 the second RAN-CP 12B can check the UE context and determine whether the second RAN-CP 12B can fulfil the UE CP requirements and capability. The second RAN-CP 12B can also check whether it can accommodate the UE 46 according to its own capacity.

[0125] Blocks 308, 310, 312, and 314 will be discussed later.

[0126] At block 316, method 300 comprises in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation 32 towards the first RAN-CP 12A.

[0127] Consequently, FIG. 3 illustrates a method 300 comprising: receiving a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP from the first RAN-CP 12A to a second RAN-CP 12B; determining whether to accept transfer of the UE context 14 and logical termination of the UE CP 16; and in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation 32 towards the first RAN-CP 12A.

[0128] The transfer confirmation 32 can have any suitable form and / or can comprise any suitable information. For example, the transfer confirmation 32 can have any suitable form and / or can comprise any suitable information to confirm to the first RAN-CP 12A that the second RAN-CP 12B will accept the transfer of the UE context 14 and logical termination of the UE CP 16.

[0129] In some examples, block 316 comprises transmitting a Relocation Acknowledgement message (Relocation ACK) towards the first RAN-CP 12A.

[0130] In some, but not necessarily all, examples, block 316 comprises if it is determined to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation towards the first RAN-CP 12A.

[0131] In examples, the second RAN-CP 12B determines at block 306 that it cannot accept the transfer.

[0132] In some such examples, the second RAN-CP 12B transmits at least one message towards the first RAN-CP 12B to inform the first RAN-CP 12A that the requested transfer cannot be accepted by the second RAN-CP 12B. The at least one message informing the first RAN-CP 12A that the requested transfer cannot be accepted by the second RAN-CP 12B can be considered a refusal message.

[0133] In examples, the first RAN-CP 12A, based at least in part on receiving a refusal message, processes messages stored at block 312 (described later).

[0134] At block 320, method 300 comprises transmitting relocation information 36 towards the UE 46 to inform the UE 46 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN-CP 12B.

[0135] The relocation information 36 can have any suitable form and / or can comprise any suitable information. For example, the relocation information 36 can have any suitable form and / or can comprise any suitable information to inform the UE 46 of the transfer.

[0136] In some examples, block 320 comprises transmitting a CP Relocation indication message towards the UE 46. The identifier 44 of the second RAN-CP 12B can have any suitable form and / or comprise any suitable information. For example, the identifier 44 can have any suitable form and / or can comprise any suitable information to identify the second RAN-CP 12B. For example, the identifier 44 can comprise any suitable information to enable the UE 46 and / or another RAN-CP 12, such as the third RAN-CP 12C, to identify the second RAN-CP 12B and therefore identify to where the UE context 14 and logical termination of the UE CP 16 has been transferred.

[0137] From the point of view of the UE 46, at block 320, method 300 comprises receiving relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN- CP 12B.

[0138] At block 322, method 300 comprises transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0139] The information 18 can have any suitable form and / or comprise any suitable information. For example, the information 18 can have any suitable form and / or comprise any suitable information to inform the at least one core node 129 of the transfer.

[0140] In examples, the information 18 comprises the network address of the second RAN- CP 12B so that the at least one core node 129 can send messages, such as Non Access Stratum (NAS) messages, towards the second RAN-CP 12B.

[0141] In examples the information 18 can be considered UE CP Relocation information 18.

[0142] The at least one core node 129 can comprise any suitable core node 129 or core nodes 129. For example, the at least one core node 129 can comprise any core node(s) 129 that need to know the current location of the UE context 14 and logical termination of the UE CP 16. For example, the at least one core node 129 can comprise an Access and Mobility Management Function (AMF).

[0143] At block 324, method 300 comprises transmitting information 20 towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0144] Consequently, FIG. 3 illustrates a method 300 comprising: transmitting a request 10 towards a second RAN-CP 12B to transfer a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to the second RAN- CP 12B; transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B; and transmitting information towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0145] In examples, the source DU 24 can be considered a DU 24 supporting UE communications.

[0146] The information 20 can have any suitable form and / or can comprise any suitable information. For example, the information 20 can have any suitable form and / or comprise any suitable information to inform the source DU 24 of the transfer.

[0147] In examples, the information 20 informs the DU 24 that uplink (UL) RRC messages must be sent to the second RAN-CP 12B.

[0148] In examples the information 20 can be considered Routing update information 18.

[0149] In examples, it can be considered that, at block 324, the first RAN-CP instructs or orders the source DU 24 to update its routing information 40. In some examples, block 322 and / or block 324 can be based at least in part on receipt of the transfer confirmation 32 (block 316).

[0150] Accordingly, in some examples method 300 comprises, from the point of view of the first RAN-CP 12A: receiving a transfer confirmation 32 from the second RAN-CP 12B, wherein at least one of: transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer is based, at least in part, on receiving the transfer confirmation 32; and transmitting information 20 towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer is based, at least in part, on receiving the transfer confirmation 32.

[0151] From the point of view of the DU 24, block 324 comprises receiving information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B.

[0152] At block 326, method 300 comprises transmitting an acknowledgement 26 towards the first RAN-CP 12A.

[0153] The acknowledgement 26 can have any suitable form and / or comprise any suitable information. For example, the acknowledgement 26 can have any suitable form and / or comprise any suitable information to acknowledge receipt of the information 20 at block 324.

[0154] In examples, the acknowledgement 26 informs the first RAN-CP 12A that there will be no further messages from the UE 46 to the first RAN-CP 12A.

[0155] In examples the acknowledgement 26 can be considered a routing update acknowledgement.

[0156] From the point of view of the first RAN-CP 12A, block 326 comprises receiving an acknowledgement 26 from the source DU 24. At block 328, method 300 comprises updating routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0157] Consequently, FIG. 3 illustrates a method 30 comprising: receiving information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement 26 towards the first RAN-CP 12A; and updating routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0158] Routing information 40 can have any suitable form and / or can comprise any suitable information. For example, routing information 40 can have any suitable form and / or can comprise any suitable information to enable the source DU 24 to correctly route messages from the UE 46 towards the second RAN-CP 12B.

[0159] In some examples, the DU 24 updates its routing table to enable the DU 24 to route messages from the UE 46 towards the second RAN-CP 12B.

[0160] At block 329, the DU 24 forwards at least one message from the UE 46 towards the second RAN-CP 12B, in accordance with the updated routing information 40.

[0161] At block 330, method 300 comprises transmitting transfer complete information 28 towards the second RAN-CP 12B.

[0162] Consequently, from the point of view of the first RAN-CP 12A, in examples method 300 comprises receiving an acknowledgement 26 from the source DU 326, and transmitting transfer complete information 28 towards the second RAN-CP 12B.

[0163] Block 330 can be performed based, at least in part, on receiving the acknowledgement 26 from the source DU 24 at block 326. Transfer complete information 28 can have any suitable form and / or can comprise any suitable information. For example, transfer complete information 28 can have any suitable form and / or comprise any suitable information to inform the second RAN-CP 12B that transfer of UE context 14 and logical termination of the UE CP 16 to the second RAN-CP 12B has been completed. For example, transfer complete information 28 can inform the second RAN-CP 12B that the source DU 24 will now route messages from the UE 46 towards the second RAN-CP 12B.

[0164] In some examples, the transfer complete information 28 comprises an end marker.

[0165] In examples, at least a portion of the transfer complete information 28 is received with the acknowledgement 26 from the source DU 24.

[0166] For example, the transfer complete information 28 can comprise an end marker received with the acknowledgement 26 from the source DU 24.

[0167] Accordingly, in examples, the acknowledgement comprises transfer complete information 28.

[0168] At block 308, from the point of view of the first RAN-CP 12A, method 300 comprises receiving at least one message 30. The at least one message 30 can be received from any suitable source or sources and can comprise any suitable message or messages 30.

[0169] In the example of FIG. 3, there are three instances of block 308 shown, 308_1 , 308_2 and 308_3.

[0170] At 308_1 , at least one message 30 is received by the first RAN-CP 12A from the at least one core node 129. In examples the at least one message 30 can comprise at least one NAS message from the at least one core node 129.

[0171] At 308_1 , and 308_2 at least one message 30 is received by the first RAN-CP 12A from the source DU 24. At blocks 308_1 , and 308_2 the at least one message 30 is a message received by the DU 24 from the UE 46 and forwarded by the DU 24 towards the first RAN-CP 12A. In examples, the at least one message 30 can comprise at least one RRC message from the UE 46 and forwarded towards the first RAN-CP 12A by the DU 24.

[0172] In examples, block 308 can occur after the first RAN-CP 12A has transmitted the request 10 (block 304) and prior to the first RAN-CP 12A transmitting transfer complete information 28 towards the second RAN-CP 12B (block 330).

[0173] At block 310, method 300 comprises forwarding at least one received message 30 towards the second RAN-CP 12B.

[0174] Accordingly, from the point of view of the first RAN-CP 12A, in some examples method 300 comprises after transmitting the request 10 towards the second RAN-CP 12B and prior to transmitting the transfer complete information 28 towards the second RAN-CP 12B, forwarding at least one received message 30 towards the second RAN-CP 12B.

[0175] In the illustrated example, two instances of block 310 are shown, 310_1 and 310_2. At block 310_1 the first RAN-CP 12A forwards at lease one message received from the DU 24 and the core node(s) 129 towards the second RAN-CP 12B.

[0176] In examples, block 310 can comprise any suitable number of transmissions towards the second RAN-CP 12B. For example, at block 310_1 , the at least one message 30 from the DU 24 and the at least one message 30 from the core node(s) 129 can be forwarded towards the second RAN-CP 12B in a single transmission or in multiple transmissions.

[0177] At block 310_2 at least one message from the DU 24 is forwarded towards the second RAN-CP 12B.

[0178] At block 312, method 300 comprises storing at least one received message 30 based, at least in part, on whether a transfer confirmation 32 has been received from the second RAN-CP 12B. In examples, if it is determined that a transfer confirmation 32 has not been received from the second RAN-CP 12B, the first RAN-CP stores the at least one received message 30 to, for example, ensure that no messages 30 are lost during the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0179] Accordingly, in examples, from the point of view of the first RAN-CP 12A, method 300 comprises, after transmitting the request 10 towards the second RAN-CP 12B, receiving at least one message 30, determining whether a transfer confirmation 32 has been received from the second RAN-CP 12B, and in response to determining that a transfer confirmation 32 has not been received from the second RAN-CP 12B, storing the at least one message 30.

[0180] Received messages 30 can be stored in any suitable memory. See, for example, FIGs 10A and 10B.

[0181] In examples, if a transfer confirmation 32 has been received from the second RAN-CP 12B, the first RAN-CP 12A does not store received message(s) 30 that are forwarded towards the second RAN-CP 12B. See, for example, block 310_2.

[0182] In some examples, the first RAN-CP 12A deletes any stored messages 30 once a transfer confirmation 32 is received from the second RAN-CP 12B (not illustrated in FIG. 3).

[0183] Accordingly, in some examples, from the point of view of the first RAN-CP 12A, method 300 comprises receiving a transfer confirmation 32 from the second RAN-CP 12B and deleting any stored messages based, at least in part, on receiving the transfer confirmation 32.

[0184] At block 314, method 300 comprises storing at least one received message 30 based, at least in part, on whether a transfer complete information 28 has been received from the first RAN-CP 12A. In examples, if it is determined that transfer complete information 28 has not been received from the first RAN-CP 12A, the second RAN-CP 12B stores the at least one message 30 to, for example, ensure that no messages 30 are lost during the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0185] Accordingly, in examples, from the point of view of the second RAN-CP 12B, method 300 comprises, receiving at least one forwarded message 30 from the first RAN-CP 12A, determining whether transfer complete information 28 has been received, and in response to determining that transfer complete information 28 has not been received, storing the at least one forwarded message 30.

[0186] Messages 30 can be stored in any suitable memory. See, for example, FIGs 10A and 10B.

[0187] In the example of FIG. 3, there three instances of block 314 are shown, 314_1 , 314_2, and 314_3.

[0188] In the illustrated example, the second RAN-CP 12B determines at block 314_1 ,314_2, and 314_3 that transfer complete information 28 has not been received and therefore stores the forwarded message(s) 30.

[0189] In some examples, the second RAN-CP 12B performs block 314 only in relation to messages received from the DU 24, without forwarding by the first RAN-CP 12A. In such examples, blocks 314_1 and 314_2 would not be present, and block 314_3 would be present.

[0190] In examples, the second RAN-CP 12B processes the stored messages based, at least in part, on receipt of the transfer complete information 28.

[0191] At block 332, method 300 comprises determining that radio link failure has occurred. In examples, it can therefore be considered that the UE 46 experiences a radio link failure at block 332. At block 334, method 300 comprises transmitting a re-establishment request 42 towards a third RAN-CP 12C, wherein the re-establishment request 42 comprises an identifier 44 of the second RAN-CP 12B.

[0192] In examples, the identifier 44 at block 334 can be an identifier as described in relation to block 320. In some examples, the identifier 44 at block 334 can comprise the identifier received at block 320.

[0193] Consequently, FIG. 3 illustrates a method 300 comprising: receiving relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN- CP 12B; determining that radio link failure has occurred at the UE 46; and transmitting a re-establishment request towards a third RAN-CP 12C, wherein the reestablishment request comprises an identifier 44 of the second RAN-CP 12B.

[0194] Accordingly, in examples, the UE 46 informs a RAN-CP to which the UE 46 is attempting to re-establish connection where the UE context 14 and logical termination of the UE CP 16 was last located to enable, for example, the RAN-CP to obtain the UE context 14.

[0195] From the point of view of the third RAN-CP 12C, block 334 comprises receiving a reestablishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46, which in the example of FIG. 3 is the second RAN-CP 12B.

[0196] At block 336, method 300 comprises transmitting a request 38 for UE context 14 towards the RAN-CP identified by the identifier 44, which in the example of FIG. 3 is the second RAN-CP 12B.

[0197] The request 38 for UE context 14 can have any suitable form and / or can comprise any suitable information. For example, the request 38 for UE context 14 can have any suitable form and / or comprise any suitable information to request the last RAN-CP of the UE 46 to provide the UE context 14.

[0198] In some examples, the request 38 for UE context 14 comprises an identifier of the UE 46.

[0199] In examples, block 336 comprises transmitting a UE context request message.

[0200] From the point of view of the second RAN-CP 12B, block 336 comprises receiving a request 38 for the UE context 14 from a third RAN-CP 12C.

[0201] At block 338, method 300 comprises transmitting the UE context 14 towards the third RAN-CP 12C.

[0202] Consequently, in examples, method 300 comprises, from the point of view of the second RAN-CP 12B, receiving a request 38 for the UE context 14 from a third RAN- CP 12C, and transmitting the UE context 14 towards the third RAN-CP 12C.

[0203] As used herein, transmitting and / or receiving UE context 14 should be understood to include transmitting and / or receiving information to enable determining of the UE context 14.

[0204] From the point of view of the third RAN-CP 12C, block 338 comprises receiving the UE context 14 from the RAN-CP identified by the identifier 44.

[0205] Consequently, FIG. 3 illustrates a method 300 comprising: receiving a re-establishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46; transmitting a request 38 for UE context 14 towards the RAN-CP identified by the identifier 44; and receiving the UE context 14 from the RAN-CP identified by the identifier 44.

[0206] The third RAN-CP 12C therefore has the UE context 14 for use in re-establishing connection for the UE 46. In examples, the order of one or more blocks / actions can change and the example of FIG. 3 is not, therefore, intended to indicate a required order of actions. For example, block 316 can occur earlier or later in illustrated method. Similarly, blocks 308, 310, 312, and / or 314 can occur earlier or later in the illustrated method.

[0207] Examples of the disclosure are advantageous and / or provide technical benefits.

[0208] For example, examples of the disclosure provide for UE context and logical termination of the UE CP to be transferred to a most suitable RAN-CP.

[0209] For example, examples of the disclosure provide for UE context and logical termination of the UE CP to be transferred without involving handover and / or RACH procedures.

[0210] For example, examples of the disclosure provide for UE context and logical termination of the UE CP to be transferred while the UE is in RRC Connected state and while the UE remains in RRC Connected state.

[0211] For example, examples of the disclosure provide for UE context to be retrieved upon radio link failure.

[0212] For example, examples of the disclosure provide a way to relocate UE context allowing the Termination of CP to treat the messages in the order of their transmission by the UE.

[0213] FIG. 4 illustrates an example of a method 400.

[0214] Method 400 can be performed by any suitable apparatus comprising any suitable means for performing method 400, for example an apparatus as described in relation to FIG. 10A and / or FIG. 10B.

[0215] In examples, method 400 can be performed by a RAN-CP, or by a control device configured to control the functioning thereof. At block 402, method 400 comprises transmitting a request 10 towards a second RAN- CP 12B to transfer a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to the second RAN-CP 12B.

[0216] At block 404, method 400 comprises transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0217] At block 406, method 400 comprises transmitting information towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0218] Consequently, FIG. 4 illustrates a method 400 comprising: transmitting a request 10 towards a second RAN-CP 12B to transfer a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to the second RAN- CP 12B; transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B; and transmitting information towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0219] FIG. 5 illustrates an example of a method 500.

[0220] Method 500 can be performed by any suitable apparatus comprising any suitable means for performing method 500, for example an apparatus as described in relation to FIG. 10A and / or FIG. 10B.

[0221] In examples, method 500 can be performed by a RAN-CP, or by a control device configured to control the functioning thereof. At block 502, method 500 comprises receiving a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP from the first RAN- CP 12A to a second RAN-CP 12B.

[0222] At block 504, method 500 comprises determining whether to accept transfer of the UE context 14 and logical termination of the UE CP 16.

[0223] At block 506, method 500 comprises in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation 32 towards the first RAN-CP 12A.

[0224] Consequently, FIG. 5 illustrates a method 500 comprising: receiving a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP from the first RAN-CP 12A to a second RAN-CP 12B; determining whether to accept transfer of the UE context 14 and logical termination of the UE CP 16; and in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation 32 towards the first RAN-CP 12A.

[0225] FIG. 6 illustrates an example of a method 600.

[0226] Method 600 can be performed by any suitable apparatus comprising any suitable means for performing method 600, for example an apparatus as described in relation to FIG. 10A and / or FIG. 10B.

[0227] In examples, method 600 can be performed by a DU, or by a control device configured to control the functioning thereof.

[0228] At block 602, method 600 comprises receiving information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP to a second RAN-CP. At block 604, method 600 comprises transmitting an acknowledgement 26 towards the first RAN-CP 12A.

[0229] At block 606, method 600 comprises updating routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0230] Consequently, FIG. 6 illustrates a method 600 comprising: receiving information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement 26 towards the first RAN-CP 12A; and updating routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0231] FIG. 7 illustrates an example of a method 700.

[0232] Method 700 can be performed by any suitable apparatus comprising any suitable means for performing method 700, for example an apparatus as described in relation to FIG. 10A and / or FIG. 10B.

[0233] In examples, method 700 can be performed by a UE, or by a control device configured to control the functioning thereof.

[0234] At block 702, method 700 comprises receiving relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN- CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN-CP 12B.

[0235] At block 704, method 700 comprises determining that radio link failure has occurred at the UE 46. At block 706, method 700 comprises transmitting a re-establishment request towards a third RAN-CP 12C, wherein the re-establishment request comprises an identifier 44 of the second RAN-CP 12B.

[0236] Consequently, FIG. 7 illustrates a method comprising: receiving relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN- CP 12B; determining that radio link failure has occurred at the UE 46; and transmitting a re-establishment request towards a third RAN-CP 12C, wherein the reestablishment request comprises an identifier 44 of the second RAN-CP 12B.

[0237] FIG. 8 illustrates an example of a method 800.

[0238] Method 800 can be performed by any suitable apparatus comprising any suitable means for performing method 800, for example an apparatus as described in relation to FIG. 10A and / or FIG. 10B.

[0239] In examples, method 800 can be performed by a RAN-CP, or by a control device configured to control the functioning thereof.

[0240] At block 802, method 800 comprises receiving a re-establishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46.

[0241] At block 804, method 800 comprises transmitting a request 38 for UE context 14 towards the RAN-CP identified by the identifier 44.

[0242] At block 806, method 800 comprises receiving the UE context 14 from the RAN-CP identified by the identifier 44.

[0243] Consequently, FIG. 8 illustrates a method 800 comprising: receiving a re-establishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46; transmitting a request 38 for UE context 14 towards the RAN-CP identified by the identifier 44; and receiving the UE context 14 from the RAN-CP identified by the identifier 44.

[0244] In examples of the disclosure, the UE can be in the RRC CONNECTED state before and after the transfer procedure and the relocation is triggered by the source RAN- CP, i.e. , the RAN-CP the UE is currently connected to because this RAN-CP has the UE Context and other UE-specific information (e.g., PHY requirements, latency requirements, slice requirements etc.).

[0245] Examples of the disclosure enable a RAN-CP instance hosting the UE RRC can relocate the UE RRC and context (UE CP) to another RAN-CP instance without any mobility / handover and RACH procedures.

[0246] In examples, suppose a “better” RAN CP is detected for the UE, the UE context is moved to this RAN CP instance without the handover procedure and RACH procedure, thereby reducing the delay that is normally incurred by such procedures.

[0247] Furthermore, the selection of most appropriate RAN CP instance for a given UE may change due to factors not directly related to a given UE. One example is that a given RAN CP instance may be capacity limit and that one or more UEs need to be transferred to another instance. Another example is that a given UE may no longer be one of the most critical UE and so may become candidate for transfer to another RAN CP instance handling less critical UEs,

[0248] In examples, decoupling of inter-cell handovers and CP relocation allows the network to optimize for UE mobility and application requirements (e.g., latency) simultaneously.

[0249] FIG. 9 illustrates an example of signaling between entities. FIG. 9 also illustrates an example of a method 900. In examples, FIG. 9 can be considered to illustrate a plurality of methods. For example, FIG. 9 illustrates one or more actions at a plurality of actors / entities and, in examples, FIG. 9 can be considered to illustrate a plurality of methods performed by the individual actors / entities.

[0250] The example of FIG. 9 is similar to the example of FIG. 3.

[0251] At block 1 , RAN-CP1 decides to relocate the UE RRC termination to RAN-CP2.

[0252] At block 2, RAN-CP1 sends a request for relocation to RAN-CP2.

[0253] At block 3, any RRC message received from the UE by RAN-CP1 can be forwarded to RAN-CP2.

[0254] At block 4, any RRC message received from the UE by RAN-CP1 can be forwarded to RAN-CP2.

[0255] At block 5. the NAS Message can be forwarded to CN.

[0256] At block 6, RAN-CP2 can send RRC messages to the UE (there is no other RRC message that needs to be treated first).

[0257] At block 7, CN may send some NAS message to the UE.

[0258] At block 8, RAN-CP1 may forward the message to RAN-CP2.

[0259] At block 9, RAN-CP1 stores the NAS messages from CN in case the Relocation is rejected.

[0260] At block 10, RAN-CP1 stores the RRC messages in case the relocation request is refused by RAN-CP2.

[0261] At block 11 , RAN-CP2 accepts the relocation. At block 12, CP2 informs UE about the CP relocation. This message includes the ID of CP2. This element would be sent by UE to the NW when its context needs to be retrieved. For example, for a RRC re-establishment procedure, (see block 24 and further)

[0262] Without this message, the UE would not be able to know where its context is located because it could be in RAN-CP2 or RAN-CP3.

[0263] At block 13, the Core Network is informed of the change of UE RRC termination by the RAN. The message includes the network address of RAN-CP2 so that the NAS messages from CORE can be sent to RAN-CP2.

[0264] At block 14, RAN-CP1 deletes the stored RRC messages.

[0265] At block 15, RAN-CP1 deletes the stored NAS messages.

[0266] At block 16, any UE message received by RAN-CP1 is forwarded to RAN-CP2 without being stored.

[0267] At block 17, NAS messages from CN are sent to RAN-CP2 directly.

[0268] At block 18, RAN-CP1 informs the DU that the UL RRC messages must be sent to RAN-CP2.

[0269] At block 19, DU sends to RAN-CP1 a message containing an END marker. This message indicates that there will be no further messages from the UE to RAN-CP1.

[0270] At block 20, the DU updates its routing table. RAN-CP2 or DU request UE to update / synchronise that the UE context has been moved to RAN-CP2 (shown in Fig. 9 block 12).

[0271] At block 21 , the RRC message from UE are sent to RAN-CP2.

[0272] At block 22, RAN-CP2 stores the received UE RRC messages from DU until it receives the END marker from RAN-CP1. At block 23, RAN-CP1 forwards the END marker received from DU to RAN-CP2.

[0273] At block 24, UE experiences a Radio Link Failure.

[0274] At block 25, UE performs a Re-establishment Request. In the message, UE indicates that its context is in RAN-CP2. This allows RAN-CP3 to know to which node it should contact for UE context.

[0275] At block 26, RAN-CP3 request the UE context to RAN-CP2 (indicating the UE ID)

[0276] At block 27, RAN-CP2 sends UE context to RAN-CP2.

[0277] Fig 10A illustrates an example of a block diagram of an apparatus 130. The apparatus 130 may be a controller of an apparatus or device such as a terminal node 110, for example a UE 46, or network node 168 such as a core node 129, or a DU 24. In examples the apparatus may be a controller of a RAN-CP 1. The apparatus 130 may be considered a controller or controller device.

[0278] Implementation of a controller 130 may be as controller circuitry. The controller 130 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware).

[0279] As illustrated in Fig 10A the controller 130 may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program 136 in a general-purpose or special-purpose processor 132 that may be stored on a computer readable storage medium (disk, memory etc.) to be executed by such a processor 132.

[0280] The processor 132 is configured to read from and write to the memory 134. The processor 132 may also comprise an output interface via which data and / or commands are output by the processor 132 and an input interface via which data and / or commands are input to the processor 132. The memory 134 stores a computer program 136 comprising computer program instructions (computer program code) that controls the operation of the apparatus 130 when loaded into the processor 132. The computer program instructions, of the computer program 136, provide the logic and routines that enables the apparatus to perform the methods illustrated in the accompanying Figs. The processor 132 by reading the memory 134 is able to load and execute the computer program 136.

[0281] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code the at least one memory 134 and the computer program code configured to, with the at least one processor 132, cause the apparatus 130 at least to perform: transmitting a request 10 towards a second RAN-CP 12B to transfer a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to the second RAN- CP 12B; transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B; and transmitting information towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0282] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code the at least one memory 134 and the computer program code configured to, with the at least one processor 132, cause the apparatus 130 at least to perform: receiving a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP from the first RAN-CP 12A to a second RAN-CP 12B; determining whether to accept transfer of the UE context 14 and logical termination of the UE CP 16; and in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation 32 towards the first RAN-CP 12A.

[0283] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code the at least one memory 134 and the computer program code configured to, with the at least one processor 132, cause the apparatus 130 at least to perform: receiving information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement 26 towards the first RAN-CP 12A; and updating routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0284] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code the at least one memory 134 and the computer program code configured to, with the at least one processor 132, cause the apparatus 130 at least to perform: receiving relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN- CP 12B; determining that radio link failure has occurred at the UE 46; and transmitting a re-establishment request towards a third RAN-CP 12C, wherein the reestablishment request comprises an identifier 44 of the second RAN-CP 12B.

[0285] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code the at least one memory 134 and the computer program code configured to, with the at least one processor 132, cause the apparatus 130 at least to perform: receiving a re-establishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46; transmitting a request 38 for UE context 14 towards the RAN-CP identified by the identifier 44; and receiving the UE context 14 from the RAN-CP identified by the identifier 44.

[0286] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code, the at least one memory storing instructions that, when executed by the at least one processor 132, cause the apparatus at least to: transmit a request 10 towards a second RAN-CP 12B to transfer a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to the second RAN-CP 12B; transmit information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B; and transmit information towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0287] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code, the at least one memory storing instructions that, when executed by the at least one processor 132, cause the apparatus at least to: receive a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP from the first RAN-CP 12A to a second RAN-CP 12B; determine whether to accept transfer of the UE context 14 and logical termination of the UE CP 16; and in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmit a transfer confirmation 32 towards the first RAN- CP 12A. In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code, the at least one memory storing instructions that, when executed by the at least one processor 132, cause the apparatus at least to: receive information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP to a second RAN-CP; transmit an acknowledgement 26 towards the first RAN-CP 12A; and update routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0288] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code, the at least one memory storing instructions that, when executed by the at least one processor 132, cause the apparatus at least to: receive relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN- CP 12B; determine that radio link failure has occurred at the UE 46; and transmit a re-establishment request towards a third RAN-CP 12C, wherein the reestablishment request comprises an identifier 44 of the second RAN-CP 12B.

[0289] In examples, the apparatus 130 comprises: at least one processor 132; and at least one memory 134 including computer program code, the at least one memory storing instructions that, when executed by the at least one processor 132, cause the apparatus at least to: receive a re-establishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46; transmit a request 38 for UE context 14 towards the RAN-CP identified by the identifier receive the UE context 14 from the RAN-CP identified by the identifier 44.

[0290] As illustrated in Fig 10A, the computer program 136 may arrive at the apparatus 130 via any suitable delivery mechanism 162. The delivery mechanism 162 may be, for example, a machine readable medium, a computer-readable medium, a non- transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD- ROM) or a Digital Versatile Disc (DVD) or a solid-state memory, an article of manufacture that comprises or tangibly embodies the computer program 136. The delivery mechanism may be a signal configured to reliably transfer the computer program 136. The apparatus 130 may propagate or transmit the computer program 136 as a computer data signal.

[0291] Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: transmitting a request 10 towards a second RAN-CP 12B to transfer a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to the second RAN- CP 12B; transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B; and transmitting information towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0292] Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: receiving a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP from the first RAN-CP 12A to a second RAN-CP 12B; determining whether to accept transfer of the UE context 14 and logical termination of the UE CP 16; and in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation 32 towards the first RAN-CP 12A. Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: receiving information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement 26 towards the first RAN-CP 12A; and updating routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0293] Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: receiving relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN- CP 12B; determining that radio link failure has occurred at the UE 46; and transmitting a re-establishment request towards a third RAN-CP 12C, wherein the reestablishment request comprises an identifier 44 of the second RAN-CP 12B.

[0294] Computer program instructions for causing an apparatus to perform at least the following or for performing at least the following: receiving a re-establishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46; transmitting a request 38 for UE context 14 towards the RAN-CP identified by the identifier 44; and receiving the UE context 14 from the RAN-CP identified by the identifier 44.

[0295] The computer program instructions may be comprised in a computer program, a non- transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program. Although the memory 134 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable and / or may provide permanent / semi-permanent / dynamic / cached storage.

[0296] In examples the memory 134 comprises a random-access memory 158 and a read only memory 160. In examples the computer program 136 can be stored in the read only memory 158. See, for example, Fig. 10B.

[0297] Although the processor 132 is illustrated as a single component / circuitry it may be implemented as one or more separate components / circuitry some or all of which may be integrated / removable. The processor 132 may be a single core or multi-core processor.

[0298] References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single / multi- processor architectures and sequential (Von Neumann) / parallel architectures but also specialized circuits such as field- programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

[0299] As used in this application, the term ‘circuitry’ may refer to one or more or all of the following:

[0300] (a) hardware-only circuitry implementations (such as implementations in only analog and / or digital circuitry) and

[0301] (b) combinations of hardware circuits and software, such as (as applicable):

[0302] (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory or memories 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 (for example, firmware) for operation, but the software may not be present when it is not needed for operation.

[0303] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

[0304] The blocks illustrated in the accompanying Figs may represent steps in a method and / or sections of code in the computer program 136. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

[0305] Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

[0306] The apparatus 130 can, in examples, comprise means for: transmitting a request 10 towards a second RAN-CP 12B to transfer a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to the second RAN- CP 12B; transmitting information 18 towards at least one core node 129 to inform the at least one core node 129 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B; and transmitting information towards a source DU 24 associated with the UE 46 to inform the source DU 24 of the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B. The apparatus 130 can, in examples, comprise means for: receiving a request 10 from a first RAN-CP 12A to transfer a UE context 14 and logical termination of the UE CP from the first RAN-CP 12A to a second RAN-CP 12B; determining whether to accept transfer of the UE context 14 and logical termination of the UE CP 16; and in response to determining to accept transfer of the UE context 14 and logical termination of the UE CP 16, transmitting a transfer confirmation 32 towards the first RAN-CP 12A.

[0307] The apparatus 130 can, in examples, comprise means for: receiving information 20 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement 26 towards the first RAN-CP 12A; and updating routing information 40 based, at least in part, on the transfer of the UE context 14 and logical termination of the UE CP 16 from the first RAN-CP 12A to the second RAN-CP 12B.

[0308] The apparatus 130 can, in examples, comprise means for: receiving relocation information 36 indicating a transfer of a UE context 14 and logical termination of the UE CP 16 from a first RAN-CP 12A to a second RAN-CP 12B, wherein the relocation information 36 comprises an identifier 44 of the second RAN- CP 12B; determining that radio link failure has occurred at the UE 46; and transmitting a re-establishment request towards a third RAN-CP 12C, wherein the reestablishment request comprises an identifier 44 of the second RAN-CP 12B.

[0309] The apparatus 130 can, in examples, comprise means for: receiving a re-establishment request 42 from a UE 46, wherein the re-establishment request 42 comprises an identifier 44 of a last RAN-CP of the UE 46; transmitting a request 38 for UE context 14 towards the RAN-CP identified by the identifier 44; and receiving the UE context 14 from the RAN-CP identified by the identifier 44. In examples, an apparatus 130 can comprise means for performing one or more methods, or at least part of one or more methods, as disclosed herein.

[0310] In examples, an apparatus 130 can be configured to perform one or more methods, or at least a part of one or more methods, as disclosed herein.

[0311] The above-described examples find application as enabling components of: automotive systems; telecommunication systems; electronic systems including consumer electronic products; distributed computing systems; media systems for generating or rendering media content including audio, visual and audio visual content and mixed, mediated, virtual and / or augmented reality; personal systems including personal health systems or personal fitness systems; navigation systems; user interfaces also known as human machine interfaces; networks including cellular, non-cellular, and optical networks; ad-hoc networks; the internet; the internet of things; virtualized networks; and related software and services.

[0312] The apparatus can be provided in an electronic device, for example, a mobile terminal, according to an example of the present disclosure. It should be understood, however, that a mobile terminal is merely illustrative of an electronic device that would benefit from examples of implementations of the present disclosure and, therefore, should not be taken to limit the scope of the present disclosure to the same. While in certain implementation examples, the apparatus can be provided in a mobile terminal, other types of electronic devices, such as, but not limited to: mobile communication devices, hand portable electronic devices, wearable computing devices, portable digital assistants (PDAs), pagers, mobile computers, desktop computers, televisions, gaming devices, laptop computers, cameras, video recorders, GPS devices and other types of electronic systems, can readily employ examples of the present disclosure. Furthermore, devices can readily employ examples of the present disclosure regardless of their intent to provide mobility.

[0313] The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to “comprising only one...” or by using “consisting”.

[0314] In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected / coupled / in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e. , so as to provide direct or indirect connection / coupling / communication. Any such intervening components can include hardware and / or software components.

[0315] As used herein, the term "determine / determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, " determine / determining" can include resolving, selecting, choosing, establishing, and the like.

[0316] In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’ or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example. Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

[0317] Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

[0318] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0319] Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

[0320] The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a / an / the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

[0321] The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

[0322] In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described. The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

[0323] Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance it should be understood that the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not emphasis has been placed thereon. l / we claim:

Claims

CLAIMS1. An apparatus comprising means for: transmitting a request towards a second radio access network - control plane, RAN-CP, to transfer a user equipment, UE, context and logical termination of the UE control plane, CP, from a first RAN-CP to the second RAN-CP; transmitting information towards at least one core node to inform the at least one core node of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP towards the second RAN-CP; and transmitting information towards a source distributed unit, DU, associated with the UE to inform the source DU of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

2. The apparatus as claimed in claim 1, wherein the means are configured to: receive an acknowledgement from the source DU; and transmit transfer complete information towards the second RAN-CP.

3. The apparatus as claimed in claim 1 or 2, wherein the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

4. The apparatus as claimed in claim 2 or 3, wherein the means are configured to: after transmitting the request towards the second RAN-CP and prior to transmitting the transfer complete information towards the second RAN-CP, forward at least one received message towards the second RAN-CP.

5. The apparatus as claimed in any preceding claim, wherein the means are configured to: after transmitting the request towards the second RAN-CP, receive at least one message; determine whether a transfer confirmation has been received from the second RAN-CP; andin response to determining that a transfer confirmation has not been received from the second RAN-CP, store the at least one received message.

6. The apparatus as claimed in claim 5, wherein the means are configured to: receive a transfer confirmation from the second RAN-CP and delete any stored messages based, at least in part, on receiving the transfer confirmation.

7. The apparatus as claimed in any preceding claim, wherein the means are configured to: receive a transfer confirmation from the second RAN-CP, wherein at least one of: transmitting information towards at least one core node to inform the at least one core node of the transfer is based, at least in part, on receiving the transfer confirmation; and transmitting information towards a source DU associated with the UE to inform the source DU of the transfer is based, at least in part, on receiving the transfer confirmation.

8. The apparatus as claimed in any of claims 2 to 7, wherein at least a portion of the transfer complete information is received with the acknowledgement from the source DU.

9. The apparatus as claimed in any preceding claim, wherein the apparatus comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the apparatus.

10. A method comprising: transmitting a request towards a second RAN-CP to transfer a UE context and logical termination of the UE CP from a first RAN-CP to the second RAN-CP; transmitting information towards at least one core node to inform the at least one core node of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP; andtransmitting information towards a source distributed unit, DU, associated with the UE to inform the source DU of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

11. The method as claimed in claim 10, comprising: receiving an acknowledgement from the source DU; and transmitting transfer complete information towards the second RAN-CP.

12. The method as claimed in claim 10 or 11 , wherein the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

13. The method as claimed in any of claims 10 to 12, comprising: after transmitting the request towards the second RAN-CP and prior to transmitting the transfer complete information towards the second RAN-CP, forwarding at least one received message towards the second RAN-CP.

14. The method as claimed in any of claims 10 to 13, comprising: after transmitting the request towards the second RAN-CP, receiving at least one message; determining whether a transfer confirmation has been received from the second RAN-CP; and in response to determining that a transfer confirmation has not been received from the second RAN-CP, store the at least one received message.

15. The method as claimed in claim 14, comprising: receiving a transfer confirmation from the second RAN-CP and deleting any stored messages based, at least in part, on receiving the transfer confirmation.

16. The method as claimed in any of claims 10 to 15, comprising: receiving a transfer confirmation from the second RAN-CP, wherein at least one of:transmitting information towards at least one core node to inform the at least one core node of the transfer is based, at least in part, on receiving the transfer confirmation; and transmitting information towards a source DU associated with the UE to inform the source DU of the transfer is based, at least in part, on receiving the transfer confirmation.

17. The method as claimed in any of claims 11 to 16, wherein at least a portion of the transfer complete information is received with the acknowledgement from the source DU.

18. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: transmitting a request towards a second RAN-CP to transfer a UE context and logical termination of the UE CP from a first RAN-CP to the second RAN-CP; transmitting information towards at least one core node to inform the at least one core node of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP; and transmitting information towards a source distributed unit, DU, associated with the UE to inform the source DU of the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

19. The computer program as claimed in claim 18, comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving an acknowledgement from the source DU; and transmitting transfer complete information towards the second RAN-CP.

20. The computer program as claimed in claim 18 or 19, wherein the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

21. The computer program as claimed in any of claims 18 to 20, comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform:after transmitting the request towards the second RAN-CP and prior to transmitting the transfer complete information towards the second RAN-CP, forwarding at least one received message towards the second RAN-CP.

22. The computer program as claimed in any of claims 18 to 21 , comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: after transmitting the request towards the second RAN-CP, receiving at least one message; determining whether a transfer confirmation has been received from the second RAN-CP; and if it is determined that a transfer confirmation has not been received from the second RAN-CP, store the at least one received message.

23. The computer program as claimed in claim 22, comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a transfer confirmation from the second RAN-CP and deleting any stored messages based, at least in part, on receiving the transfer confirmation.

24. The computer program as claimed in any of claims 18 to 23, comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a transfer confirmation from the second RAN-CP, wherein at least one of: transmitting information towards at least one core node to inform the at least one core node of the transfer is based, at least in part, on receiving the transfer confirmation; and transmitting information towards a source DU associated with the UE to inform the source DU of the transfer is based, at least in part, on receiving the transfer confirmation.

25. The computer program as claimed in any of claims 19 to 24, wherein at least a portion of the transfer complete information is received with the acknowledgement from the source DU.

26. An apparatus comprising means for: receiving a request from a first RAN-CP to transfer a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP; determining whether to accept transfer of the UE context and logical termination of the UE CP; and in response to determining to accept transfer of the UE context and logical termination of the UE CP, transmitting a transfer confirmation towards the first RAN- CP.

27. The apparatus as claimed in claim 26, wherein the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

28. The apparatus as claimed in claim 26 or 27, wherein the means are configured to: receive at least one forwarded message from the first RAN-CP; determine whether transfer complete information has been received; and in response to determining that transfer complete information has not been received, storing the at least one forwarded message.

29. The apparatus as claimed in any of claims 26 to 28, wherein the means are configured to: transmit relocation information towards the UE to inform the UE of the transfer of the UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP.

30. The apparatus as claimed in any of claims 26 to 29, wherein the means are configured to: receive a request for the UE context from a third RAN-CP; and transmit the UE context towards the third RAN-CP.

31. A method comprising:receiving a request from a first RAN-CP to transfer a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP; determining whether to accept transfer of the UE context and logical termination of the UE CP; and in response to determining to accept transfer of the UE context and logical termination of the UE CP, transmitting a transfer confirmation towards the first RAN- CP.

32. The method as claimed in claim 31, wherein the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

33. The method as claimed in claim 31 or 32, comprising: receiving at least one forwarded message from the first RAN-CP; determining whether transfer complete information has been received; and in response to determining that transfer complete information has not been received, storing the at least one forwarded message.

34. The method as claimed in any of claims 31 to 33, comprising: transmitting relocation information towards the UE to inform the UE of the transfer of the UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP.

35. The method as claimed in any of claims 31 to 34, comprising: receiving a request for the UE context from a third RAN-CP; and transmitting the UE context towards the third RAN-CP.

36. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a request from a first RAN-CP to transfer a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP; determining whether to accept transfer of the UE context and logical termination of the UE CP; andin response to determining to accept transfer of the UE context and logical termination of the UE CP, transmitting a transfer confirmation towards the first RAN- CP.

37. The computer program as claimed in claim 31 , wherein the request to transfer the UE context and logical termination of the UE CP to the second RAN-CP comprises the UE context.

38. The computer program as claimed in claim 36 or 37, comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving at least one forwarded message from the first RAN-CP; determining whether transfer complete information has been received; and in response to determining that transfer complete information has not been received, storing the at least one forwarded message.

39. The computer program as claimed in any of claims 36 to 38, comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: transmitting relocation information towards the UE to inform the UE of the transfer of the UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP.

40. The computer program as claimed in any of claims 36 to 39, comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a request for the UE context from a third RAN-CP; and transmitting the UE context towards the third RAN-CP.

41. An apparatus comprising means for: receiving information indicating a transfer of a UE context and logical termination of the UE control plane from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement towards the first RAN-CP; andupdating routing information based, at least in part, on the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

42. The apparatus as claimed in claim 41, wherein the acknowledgement comprises transfer complete information.

43. A method comprising: receiving information indicating a transfer of a UE context and logical termination of the UE control plane from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement towards the first RAN-CP; and updating routing information based, at least in part, on the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

44. The method as claimed in claim 43, wherein the acknowledgement comprises transfer complete information.

45. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving information indicating a transfer of a UE context and logical termination of the UE control plane from a first RAN-CP to a second RAN-CP; transmitting an acknowledgement towards the first RAN-CP; and updating routing information based, at least in part, on the transfer of the UE context and logical termination of the UE control plane from the first RAN-CP to the second RAN-CP.

46. The computer program as claimed in claim 45, wherein the acknowledgement comprises transfer complete information.

47. An apparatus comprising means for: receiving relocation information indicating a transfer of a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP;determining that radio link failure has occurred at the UE; and transmitting a re-establishment request towards a third RAN-CP, wherein the re-establishment request comprises an identifier of the second RAN-CP.

48. A method comprising: receiving relocation information indicating a transfer of a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP; determining that radio link failure has occurred at the UE; and transmitting a re-establishment request towards a third RAN-CP, wherein the re-establishment request comprises an identifier of the second RAN-CP.

49. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving relocation information indicating a transfer of a UE context and logical termination of the UE CP from the first RAN-CP to a second RAN-CP, wherein the relocation information comprises an identifier of the second RAN-CP; determining that radio link failure has occurred at the UE; and transmitting a re-establishment request towards a third RAN-CP, wherein the re-establishment request comprises an identifier of the second RAN-CP.

50. An apparatus comprising means for: receiving a re-establishment request from a UE, wherein the re-establishment request comprises an identifier of a last RAN-CP of the UE; transmitting a request for UE context towards the RAN-CP identified by the identifier; and receiving the UE context from the RAN-CP identified by the identifier.

51. A method comprising: receiving a re-establishment request from a UE, wherein the re-establishment request comprises an identifier of a last RAN-CP of the UE; transmitting a request for UE context towards the RAN-CP identified by the identifier; and receiving the UE context from the RAN-CP identified by the identifier.

52. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus at least to perform: receiving a re-establishment request from a UE, wherein the re-establishment request comprises an identifier of a last RAN-CP of the UE; transmitting a request for UE context towards the RAN-CP identified by the identifier; and receiving the UE context from the RAN-CP identified by the identifier.

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