Methods, computer-readable media and apparatus related to mobility procedures in wireless networks

Abstract

A method performed by a first network node is disclosed The method comprises transmitting (402), to one or more of a user equipment (UE) and a second network node, a message comprising a request for the one or more of the UE and the second network node to release an inter-CU LTM configuration. The inter-CU LTM configuration is for use in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure by the UE to the candidate cell.

Description

METHODS, COMPUTER-READABLE MEDIA AND APPARATUS RELATED TO MOBILITY PROCEDURES IN WIRELESS NETWORKSTECHNICAL FIELD[0] Embodiments of the present disclosure relate to communications networks, and particularly to mobility procedures in wireless networks.BACKGROUNDLayer 1 (Ll) / Layer 2 (L2) based inter-cell mobility in Release 18[1] In the 3rd Generation Partnership Project (3GPP) Release 18 (Rel-18), a work item known as Further New Radio (NR) mobility enhancements is ongoing (RP-231475). This work item includes a technical area entitled L1 / L2 based inter-cell mobility. According to the Work Item Description (WID), when a User Equipment (UE) moves from the coverage area of one cell to another cell, at some point a serving cell change needs to be performed. Currently serving cell change is triggered by Layer 3 (L3) measurements and is done by Radio Resource Control (RRC) signalling triggered Reconfiguration with Synchronisation for change of Primary Cell (PCell) and Primary Secondary Cell (PSCell), as well as release add for Secondary Cells (SCells) when applicable. All cases involve complete L2 (and LI) resets, leading to longer latency, larger overhead and longer interruption time than beam switch mobility. The goal of L1 / L2 based inter-cell mobility is to enable a serving cell change via L1 / L2 signalling, in order to reduce the latency, overhead and interruption time.[2] In this work item, according to the WID, the following is included as one objective of the work:To specify mechanism and procedures of L1 / L2 based inter-cell mobility for mobility latency reduction:Configuration and maintenance for multiple candidate cells to allow fast application of configurations for candidate cells [RAN2, RAN3]Dynamic switch mechanism among candidate serving cells (including Special Cell (SpCell) and SCell) for the potential applicable scenarios based on L1 / L2 signalling [RAN2, RANI]LI enhancements for inter-cell beam management, including LI measurement and reporting, and beam indication [RANI, RAN2]Note 1: Early RAN 2 involvement is necessary, including the possibility of further clarifying the interaction between this bullet with the previous bulletTiming Advance (TA) management [RANI, RAN2]Central Unit (CU) Distributed Unit (DU) (CU-DU) interface signaling to support L1 / L2 mobility, if needed [RAN3]Note 2: Frequency Range 2 (FR2) specific enhancements are not precluded, if any.Note 3: The procedure ofLl / L2 based inter -cell mobility are applicable to the following scenarios:Standalone, Carrier Aggregation (CA) and NR Dual Connectivity (DC) (NR-DC) case with serving cell change within one Cell Group (CG)Intra-DU case and intra-CU inter-DU case (applicable for Standalone and CA: no new Radio Access Network (RAN) interfaces are expected)Both intra-frequency and inter-frequencyBoth Frequency Range 1 (FR1) and FR2Source and target cells may be synchronized or non-synchronized[3] In 3GPP, discussions have started on solutions for L1 / L2 based inter-cell mobility (sometimes also referred to as “LTM”, “L1 / L2 -triggered mobility” or “lower layer-triggered mobility”).[4] A basic principle with Ll / L2-triggered mobility is that the UE is pre-configured, by the network, with an RRC configuration per LTM candidate cell, sometimes also known as an LTM candidate cell configuration. Such an LTM candidate cell configuration may be an RRCReconfiguration message or one or more Information Elements (IEs) / fields / parameters such as CellGroupConfig. The UE performs measurements on these LTM candidate cells and transmits corresponding measurement reports to the network. The network then triggers the execution of an LTM cell switch procedure in the UE to one of these LTM candidate cells by transmitting lower layer signaling in a Medium Access Control (MAC) Control Element (CE), sometimes also referred to as an LTM cell switch command, to the UE, which then connects to the particular LTM candidate cell and switches to the LTM candidate cell configuration.[5] There currently exist certain challenge(s).[6] In 3GPP Rel-18, LTM is limited to intra-CU mobility (for both intra-DU and inter-DU). The so-called stage-2 procedures for inter-node signalling for LTM are being discussed in 3 GPP RAN3 and have been documented for inclusion in a Baseline Change Request (CR) (BLCR) for 3GPP TS 38.401 in R3-238059. The stage-2 signalling procedure for intra- CU / inter-DU LTM between source gNB-DU, gNB-CU, candidate gNB-DU and the UE is described in R3-238059 and also illustrated in Figure 1.[7] Figure 1 illustrates the procedure for inter-DU LTM. The procedure occurs between a UE 102, a source gNB-DU 104, a candidate gNB-DU 106, and a gNB-CU 108. The steps of Figure 1 are as follows:[8] At step 110, user data is exchanged between the UE 102 and the source gNB-DU 104, and at step 112, user data is exchanged between the source gNB-DU 104 and the gNB-CU 108.[9] At step 114, an L3 measurement control and reports procedure is performed.

[0010] At step 116, an LTM configuration decision is made at the gNB-CU 108.

[0011] At step 118, the gNB-CU 108 transmits, to the candidate gNB-DU 106, a UE CONTEXT SETUP REQUEST message.

[0012] At step 120, the candidate gNB-DU 106 transmits, to the gNB-CU 108, a UE CONTEXT SETUP RESPONSE message.

[0013] At step 122, the gNB-CU 108 transmits, to the source gNB-DU 104, a UE CONTEXT MODIFICATION REQUEST message.

[0014] At step 124, the source gNB-DU 104 transmits, to the gNB-CU 108, a UE CONTEXT MODIFICATION RESPONSE message.

[0015] At step 126, the gNB-CU 108 transmits, to the candidate gNB-DU 106, a UE CONTEXT MODIFICATION REQUEST message.

[0016] At step 128, the candidate gNB-DU 106 transmits, to the gNB-CU 108, a UE CONTEXT MODIFICATION RESPONSE message.

[0017] At step 130, the gNB-CU 108 transmits, to the source gNB-DU 104, a Downlink (DL) RRC MESSAGE TRANSFER message (including an RRCReconfiguration message).

[0018] At step 132, the source gNB-DU 104 transmits, to the UE 102, an RRCReconfiguration message.

[0019] At step 134, the UE 102 transmits, to the source gNB-DU 104, an RRCReconfigurationComplete message.

[0020] At step 136, the source gNB-DU 104 transmits, to the gNB-CU 108, an Uplink (UL) RRC MESSAGE TRANSFER message (including an RRCReconfigurationComplete message).

[0021] At step 138, an early TA acquisition procedure is performed between the UE 102 and the candidate gNB-DU 106.

[0022] At step 140, the candidate gNB-DU 106 transfers TA information to the gNB-CU 108.

[0023] At step 142, the gNB-CU 108 transfers TA information to the source gNB-DU 104.

[0024] At step 144, the UE 102 transmits, to the source gNB-DU 104, an LI measurement report.

[0025] At step 146, the source gNB-DU 104 makes an LTM cell switch decision.

[0026] At step 148, the source gNB-DU 104 transmits, to the UE 102, a cell switch command.

[0027] At step 150, the source gNB-DU 104 transmits, to the gNB-CU 108, a DU-CU CELL SWITCH NOTIFICATION message (including a target cell identifier (ID) and a Transmission Configuration Indication (TCI) State ID).

[0028] At step 152, the gNB-CU 108 transmits, to the candidate gNB-DU 106, a CU-DU CELL SWITCH NOTIFICATION message (including a target cell ID and a TCI State ID).

[0029] At step 154, the source gNB-DU 104 transmits, to the gNB-CU 108, a downlink data delivery status.

[0030] At step 156, the candidate gNB-DU 106 detects the UE 102 access.

[0031] At step 158, the candidate gNB-DU 106 transmits, to the gNB-CU 108, an ACCESS SUCCESS message (including a target cell ID).

[0032] At step 160, the UE 102 transmits, to the candidate gNB-DU 106, an RRCReconfigurationComplete message.

[0033] At step 162, the candidate gNB-DU 106 transmits, to the gNB-CU 108, an UL RRC MESSAGE TRANSFER message (including the RRCReconfigurationComplete message).

[0034] At step 164, the gNB-CU 108 transmits, to the source gNB-DU 104, a UE CONTEXT RELEASE COMMAND message (including prepared cells to be released).

[0035] At step 166, the source gNB-DU 104 transmits, to the gNB-CU 108, a UE CONTEXT RELEASE COMPLETE message.

[0036] At step 168, user data is exchanged between the UE 102 and the candidate gNB-DU 106, and at step 170, user data is exchanged between the candidate gNB-DU 106 and gNB-CU 108.SUMMARY

[0037] It has been suggested that LTM should be further enhanced to support inter-CU mobility in 3GPP Release 19 (Rel-19). As part of this, the procedures for configuration of the inter-CU LTM functionality towards the UE and within the network has not yet been discussed. More, specifically, it has not yet been discussed how an LTM configuration is released within the network.

[0038] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges.

[0039] In a first aspect of the disclosure, a method is performed by a first network node. The method comprises transmitting, to one or more of a UE and a second network node, a message comprising a request for the one or more of the UE and the second network node to release an inter-CU LTM configuration for use in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure by the UE to the candidate cell.

[0040] For example, the disclosure presents methods for a first network node, such as a serving gNB, to perform inter-CU LTM configuration release for a UE, comprising, transmitting, to a second network node, a request message indicating release of at least one inter-CU LTM configuration.

[0041] Additionally or alternatively, the first network node may transmit, to the UE, a request message indicating release of at least one inter-CU LTM configuration and receive, from the UE, a response message confirming the release of at least one inter-CU LTM configuration.

[0042] The first network node may receive, from a second network node, a response message confirming the release at least one inter-CU LTM configuration.

[0043] The method may comprise the first network node triggering the request message indicating release to the second network node (e.g. Candidate gNB) in response to one or more of the following:• Reception of an indication (e.g. from a third network node, such as a target gNB) that the UE has successfully performed LTM towards the third network node. An example of the indication is a Handover Success message, indicating a successful LTM execution.• Transmission of an LTM Cell switch command to the UE indicating an LTM candidate cell of a third network node.• Determining that the UE is to enter RRC IDLE or RRC IN ACTIVE;• Transmission to the UE of a message transitioning the UE to RRC IDLE or RRC INACTIVE (e.g. RRC Release message including a suspend configuration, or with the suspend configuration absent);• Reception of an indication from the UE that the UE has entered RRC IDLE or RRC INACTIVE e.g. Radio Link Control (RLC) acknowledgements in response to an RRC Release message;• Reception of an indication that the UE has re-established the connection in another network node that is not the first network node and not the second network node e.g. A Context release (in case the UE performed re-establishment in another node and the target node triggers a UE context release);• Determining that the UE is unreachable e.g. has triggered a Radio Link Failure (RLF) and / or is out of coverage.• Reception of an RRC Measurement Reporting including measurement(s) of one or more cell(s) based on which the first network node determines to re-configure LTM candidate cell(s) for the UE, which may lead to release an existing number of LTM candidate cell(s).• Reception of an RRC Reconfiguration Complete message from the UE in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s) associated to the second network node.• The UE entered RRC CONNECTED

[0044] The first network node may include in the request message indicating release to the second network node (e.g. Candidate gNB) a cause value, associated to one of the triggers which has triggered the request for release e.g. UE entering RRC IDLE or RRC INACTIVE, LTM execution in another candidate node, etc.

[0045] In a second aspect of the disclosure, there is provided a method performed by a second network node. The method comprises receiving, from a first network node, a message comprising a request for the second network node to release an inter-CU LTM configuration for use by a UE in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure. The method further comprises responsive to receiving the message, releasing the inter-CU LTM configuration.

[0046] For example, the disclosure also presents methods for a second network node, such as a candidate gNB, to perform inter-CU LTM configuration release for a UE, comprising,receiving, from a first network node, a request message indicating release of at least one inter- CU LTM configuration.

[0047] The second network node may transmit, to the first network node, a response message confirming the release of at least one inter-CU LTM configuration.

[0048] The method may further comprise, in response to receiving, from the first network node, the request message indicating release of at least one inter-CU LTM configuration, triggering the release of LTM related resources in at least one distributed network node (e.g., a DU), wherein the at least one distributed network node is responsible for the lower layer resource(s) and / or configuration(s).

[0049] In a third aspect of the disclosure, a method performed by a user equipment, the method comprising receiving, from a network node, a message comprising a request for the user equipment to release an inter-CU LTM configuration for use in connecting to and / or communicating with a candidate cell following a lower-layer cell mobility procedure. The method further comprising, responsive to receiving the message, releasing the inter-CU LTM configuration.

[0050] For example, the disclosure also presents methods for a UE to perform inter-CU LTM configuration release, comprising, receiving, from a first network node, a request message indicating release of at least one inter-CU LTM configuration and releasing at least one inter- CU LTM configuration. The UE may further transmit, to the first network node, a response message confirming the release of at least one inter-CU LTM configuration.

[0051] In a fourth aspect of the disclosure, there is provided a first network node configured to perform a method according to embodiments of the first aspect.

[0052] In a fifth aspect of the disclosure, there is provided a second network node configured to perform a method according to embodiments of the second aspect.

[0053] In a sixth aspect of the disclosure, there is provided a first network node configured to perform a method according to embodiments of the third aspect.

[0054] Certain embodiments may provide one or more of the following technical advantage(s). The proposed solutions enable the network to release an inter-CU LTM configuration. Thanks to embodiments of the disclosure, resources (such as radio resources and allocated identities) used by an inter-CU LTM configuration reserved by a candidate network node, such as a candidate gNB, can be released and used for other users.BRIEF DESCRIPTION OF THE DRAWINGS

[0055] For a better understanding of the embodiments of the present disclosure, and to show how it may be put into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0056] Fig. l is a signalling diagram showing an inter-DU LTM procedure;

[0057] Fig. 2 is a schematic diagram showing a system according to embodiments of the disclosure;

[0058] Fig. 3 is a flow chart illustrating a method in accordance with some embodiments;

[0059] Fig. 4 is a flow chart illustrating a method in accordance with some embodiments;

[0060] Fig. 5 is a flow chart illustrating a method in accordance with some embodiments;

[0061] Fig. 6 is a signalling diagram according to embodiments of the disclosure;

[0062] Fig. 7 is a signalling diagram according to further embodiments of the disclosure;

[0063] Fig. 8 is a flowchart illustrating a method in accordance with some embodiments;

[0064] Fig. 9 is a flowchart illustrating a method in accordance with some embodiments;

[0065] Fig. 10 is a flowchart illustrating a method in accordance with some embodiments;

[0066] Fig. 11 shows transmission of a Handover Cancel message, and forms part of a suggested update to 3GPP TS 38.423 vl7.6.0 in accordance with some embodiments;

[0067] Fig. 12 shows an example of a communication system in accordance with some embodiments;

[0068] Fig. 13 shows a UE in accordance with some embodiments;

[0069] Fig. 14 shows a network node in accordance with some embodiments;

[0070] Fig. 15 is a block diagram of a host;

[0071] Fig. 16 is a block diagram illustrating a virtualization environment in which functions implemented by some embodiments may be virtualized; and

[0072] Fig. 17 shows a communication diagram of a host communicating via a network node with a UE over a partially wireless connection in accordance with some embodiments.DETAILED DESCRIPTION

[0073] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

[0074] The text refers to the term “L1 / L2 based inter-cell mobility” as used in 3GPP RP-231475, though it interchangeably also uses the terms “L1 / L2 mobility”, “LI -mobility”, “LI basedmobility”, “Ll / L2-centric inter-cell mobility”, “L1 / L2 inter-cell mobility”, “Ll / L2-Triggered Mobility”, “Lower-layer triggered Mobility”, “lower-layer cell mobility” or “LTM”. The basic principle is that the UE receives a lower layer signaling (e.g. a MAC CE) from the network indicating to the LE a change (or switch or activation) of its serving cell (e.g. change of PCell, from a source to a target PCell), wherein a lower layer signaling is a message or signaling of a lower layer protocol, which may be referred as a L1 / L2 inter-cell mobility execution command or LTM cell switch command. The change of serving cell (e.g. change of PCell) may also lead to a change in Scell(s) for the same cell group e.g. where the command triggers the LE to change to another cell group configuration of the same type (e.g. another Master Cell Group (MCG) configuration). Before the LE receives the LTM cell switch command, the LE is configured by the network with one or more LTM candidate cells (e.g. reception of an RRC Reconfiguration message, with at least one LTM candidate cell configuration). A candidate cell configuration may include parameters in the IE CellGroupConfig per candidate cell and / or an embedded RRC Reconfiguration per candidate cell.

[0075] The term “LTM cell switch procedure” refers to the process of a LE changing its cell from a source cell to a target cell (which may be called here a candidate cell or a neighbour cell), using LTM. In the context of LTM, an LTM cell switch procedure may sometimes also be known as “dynamic switch”, “LTM switch”, “(LTM) cell switch”, “(LTM) serving cell change” or “(LTM) cell change”. Even if the term “change of cell” is used, that may comprise a change of a whole cell group configuration, which includes a change in the SpCell (e.g. change of PCell, or change of PSCell) and a change in SCells of the cell group (e.g. addition, modification and / or release of one or more SCells). The LTM cell switch procedure may be triggered by the LE receiving an LTM cell switch command from the network. The source and target cells in an LTM cell switch procedure may be controlled by the same gNB, which sometimes is referred to as the intra-gNB case, or when the gNB uses a distributed CU / DU RAN architecture, the intra-CU inter-DU case or the intra-CU intra-DU case (depending on whether the cells are controlled by the same DU or different DUs). When the source and target cells in an LTM cell switch procedure are controlled by different gNBs, this is sometimes referred to as the inter-gNB case, or inter-CU case, or sometimes known as an inter-CU LTM cell switch procedure.

[0076] An “inter-CU LTM cell switch procedure” is an LTM cell switch procedure resulting in a change of serving cell, e.g. change of SpCell, PCell, PSCell, to an LTM candidate cell controlled by a different base station, e.g. gNB, than the source base station, e.g. source gNBor serving gNB, of the UE upon reception of the LTM cell switch command. From the UE point of view, the actions performed during an inter-CU LTM cell switch procedure may be the same type of actions of an LTM cell switch procedure, but may also include additional actions, such as change of security key, sometimes known as security key refresh.

[0077] The text refers to “an LTM configuration”. An LTM configuration is a configuration to be used for L1 / L2 -triggered mobility or a configuration being related to L1 / L2 -triggered mobility. An LTM configuration may include one or multiple of the following type of elements where each element contains a configuration of one aspect of LTM, for example as follows:• LTM candidate cell configuration(s),• lower layer information, such as physical layer configuration, MAC layer configuration or RLC layer configuration, Cell Group configuration, serving cell configuration• higher layer information, such as RRC protocol parameters, such as timer values, Packet Data Convergence Protocol (PDCP) layer configuration, radio bearer configuration or measurement configuration• Configuration of measurements for LTM• Configuration for measurement reports for LTM• Channel State Information (CSI) resource configuration(s) for LTM• CSI report configuration for LTM• Configurations of early synchronization procedures, such as o Configurations for DL pre-sync for LTM, such as configurations for early TCI state activation o Configurations for UL pre-sync for LTM, such as configurations for reception of Physical Downlink Control Channel (PDCCH) ordered triggered preamble transmission and reception of TA• Configurations for the execution of an LTM cell switch procedure for a given LTM candidate cell configuration (e.g., whether to perform random access procedure, whether to perform RLC reestablishment, or MAC reset, or PDCP recovery), a timer value, configured UL grants, dedicated Random Access (RA) preambles.

[0078] The text refers to “an inter-CU LTM configuration”. An inter-CU LTM configuration is a LTM configuration which contains the configuration needed by the UE to start operating accordingly when it performs an inter-CU LTM cell switch procedure to an LTM candidate cell which is controlled by a different base station, e.g. gNB, from the current source base station, e.g. serving gNB of the UE. An inter-CU LTM configuration may contain the sameinformation as an LTM configuration for the intra-DU case and the intra-CU inter-DU case, but it may also include additional information which is not in LTM configuration(s) for the intra-DU case and intra-CU inter-DU case. This additional information may comprise, for example, one or more of:• Information to perform security key refresh, e.g. the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes SecurityConfig with Security AlgorithmConfig. This may be part of higher layer information. The information to perform security key refresh in the inter-CU LTM configuration is information related to inter-CU LTM configuration which is not in LTM configuration(s) for the intra-DU case and intra-CU inter-DU cases.• Indication to perform a full configuration, e.g. the RRC field fullConfig.• Indication to perform L2 re-establishment, such as an indication to perform PDCP reestablishment for one or multiple bearers.

[0079] The term “security key refresh” refers to the UE changing its security key, e.g. during a mobility procedure such as an inter-CU LTM cell switch procedure. A security key refresh may comprise at least one of:• The UE receives a Master Key Update parameter / IE (e.g. masterKeyUpdate) included in the inter-CU LTM configuration (e.g. set by the Target CU).• When a Non-Access Stratum (NAS) indication (e.g. nas-Container) is received (e.g. within the Master Key Update parameter / IE) the UE forwards the NAS indication to the upper layer (e.g. UE NAS layer);• When a key set change indication (e.g. keySetChangelndicator) is received and / or is set to ‘true’ (e.g. within the Master Key Update parameter / IE) the UE derives or updates the KgNB key based on the KAMF key, as specified in TS 33.501 (e.g., V18.3.0);• The UE derives or updates the KSNB key (for the inter-CU LTM configuration indicated in the LTM cell switch command) based on the current KSNB key or the Next Hop (NH), using the Next Hop Chaining Count (e.g. nextHopChainingCount) value indicated in the received Master Key Update parameter / IE (e.g. MasterKeyUpdate), as specified in TS 33.501 (e.g., V18.3.0);• The UE derives the KRRCenc and Kupenc keys associated with a ciphering algorithm (e.g. cipheringAlgorithm indicated in the security AlgorithmConfig), as specified in TS 33.501 (e.g., V18.3.0);• The UE derives the KRRCint and Kupint keys associated with an integrity protection algorithm (e.g. integrityProtAlgorithm indicated in the security AlgorithmConfig), as specified in TS 33.501 (e.g., V18.3.0);• The UE receives a security algorithm configuration included in the inter-CU LTM configuration, based on which the UE derives User plane keys and / or control plane keys (e.g. for encryption and / or integrity protection) e.g. the KRRCenc and KuPenc keys, the KRRCint and Kupim keys.• The UE uses its current security algorithm configuration, based on which the UE derives User plane keys and / or control plane keys (e.g. for encryption and / or integrity protection) e.g. the KRRCenc and KuPenc keys, the KRRCint and Kupint keys.• The UE applies the provided ciphering algorithm and key during an PDCP entity reestablishment procedure;• The UE applies the provided integrity protection algorithm and key during an PDCP entity re-establishment procedure• The UE may derive the security key(s) when it receives the inter-CU LTM configuration, but only used when the UE performs the inter-CU LTM cell switch procedure. In that case, when the UE is configured with an LTM candidate cell (e.g. a candidate to be a PCell) the UE derives one or more security key(s) associated to that LTM candidate cell (e.g. User Plane (UP) integrity protection key, Control Plane (CP) integrity protection key, UP encryption / ciphering key, CP encryption / ciphering key), but only starts to use one of the derived security key(s) when it performs the inter-CU LTM cell switch procedure.System overview

[0080] Error! Reference source not found, illustrates a system structure including entities involved in embodiments of the disclosure. Further detail regarding these entities can be found below in Figure 12, with reference to Figures 13 and 14.

[0081] The UE 202 is a wireless terminal, such as a cellular smartphone, sometimes connected to the first network node 204 over a wireless interface 205 and sometimes connected to a second network node 206, to which the UE 202 is connected over a wireless interface 207.

[0082] The first network node 204 controls a first cell 208 (sometimes called serving cell, SpCell, PCell or PSCell, or, in the context of mobility, referred to as source cell). The second network node 206 controls a second cell 210, which sometimes, e.g. in the context of mobility,is referred to as target cell, neighbour cell, candidate cell, LTM candidate cell or inter-CU LTM candidate cell.

[0083] Sometimes the UE 202 is configured with dual connectivity, such as NR-DC. In this case the UE 202 may be configured with a MCG and a Secondary Cell Group (SCG). The first network node 204 may control either the MCG or SCG. In this case, the second network node 206 may control an MCG or an SCG, sometimes known as the candidate MCG or target MCG, the candidate SCG or target SCG, respectively. In this case, the first network node 204 or the second network node 206 may be referred to as a Master Node (MN) (when controlling an MCG) or a Secondary Node (SN) (when controlling an SCG).

[0084] Each of the first network node 204 and the second network node 206 may be a base station such as when they e.g. are part of NG-RAN, e.g. a gNB. The first network node 204 and the second network node 206 are connected over an interface 212, which may be an Xn or Xn-C type of interface, for example when the first network node and second network node are of type gNB and part of an NG-RAN.

[0085] In the context of mobility, such as inter-CU L1 / L2 -triggered mobility, the first network node 204 may sometimes be referred to as either the source network node, the source gNB, the serving network node or the serving gNB, and the second network node 206 may sometimes be referred to as either the target network node, the target gNB, the candidate network node or the candidate gNB.

[0086] In case of a distributed CU / DU RAN architecture, the first network node 204 and / or the second network node 206 may be divided into a DU, sometimes known as gNB-DU, and a CU, sometimes referred to as gNB-CU, gNB-CU-CP or gNB-CU-UP. Thus, in such a case the first network node 204 may be divided into a first CU 214, sometimes referred to as serving CU or source CU, and a first DU 216, and second network node 206 may be divided into a second CU 218, sometimes referred to as target CU or candidate CU, and a second DU 220. Sometimes the first CU 214 is referred to as the first network node 204 and the second CU 218 is referred to as the second network node 206.

[0087] The first CU 214 and the first DU 216 are connected over an interface 222, which may be an Fl type of interface in case of NG-RAN. Correspondingly, the second CU 218 and the second DU 220 are connected over an interface 224, which may be an Fl type of interface in case of NG-RAN.

[0088] The first network node 204 and the second network node 206 may be connected to a third network node 226 over interfaces 228 and 230, respectively. The third network node 226 maybe a base station such as, when it is e.g. are part of NG-RAN, e.g. a gNB. In the latter case the interfaces 228 and 230 may both be an Xn or Xn-C type of interface. The UE 202 may sometimes be connected to the third network node 226 over a wireless interface (not shown in the figure). In the context of mobility, the third network node 226 may be referred to as either target network node or target gNB. The third network node 226 may control a third cell, which sometimes may be referred to as a target cell (not illustrated in Figure 2).The methods

[0089] The disclosure presents methods, and apparatus for performing those methods, to perform inter-CU LTM configuration release for a UE. In one set of methods, the UE is connected to a first network node in a first cell and is configured with at least one inter-CU LTM configuration. This inter-CU LTM configuration may contain LTM configuration controlled by a second network node (and generated by that second network node), such as one or more of LTM candidate cell configuration(s), configurations for the execution of an LTM cell switch procedure, CSI resource configuration(s) for LTM, configurations of early synchronization procedures and information to perform security key refresh. The information to perform security key refresh in the inter-CU LTM configuration is additional information related to inter-CU LTM configuration which is not in LTM configuration(s) for the intra-DU case and intra-CU inter-DU cases.

[0090] The information to perform security key refresh may, for example be the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes SecurityConfig with Security AlgorithmConfig. This may be part of higher layer information. The information to perform security key refresh in the inter-CU LTM configuration is information related to inter- CU LTM configuration which is not in LTM configuration(s) for the intra-DU case and intra- CU inter-DU cases.

[0091] In one example, the UE is configured with at least one inter-CU LTM configuration by the first network node. For example, in order to setup the at least one inter-CU LTM configuration for the UE, the first network node may transmit a request message, such as a HANDOVER REUQEST message, to the target network node, which then returns the at least one inter-CU LTM configuration for the UE in a response message, such as a HANDOVER REQUEST ACKNOWLEDGE message, to the first network node. An example of a cause for configuring the UE with at least one inter-CU LTM configuration may be reception of a measurement report, from the UE, by the first network node.

[0092] In another example, the UE has been configured with at least one inter-CU LTM configuration by another network node than the first network node and due to a mobility procedure, such as L3 handover or L1 / L2 -triggered mobility, is being handed over and controlled by the first network node.

[0093] The first network node then determines to perform inter-CU LTM configuration release for the UE and triggers a request message indicating release to a second network node in response to one or more of the following:• Reception of a measurement report, from the UE, by the first network node, that indicates that a certain cell is above or below a certain threshold.• Reception of an indication (e.g. from a third network node) that the UE has successfully performed LTM towards the third network node. An example of the indication is a Handover Success message, indicating a successful LTM execution.• Transmission of an LTM Cell switch command to the UE indicating an LTM candidate cell of a third network node.• Determining that the UE is to enter RRC IDLE or RRC IN ACTIVE;• Transmission to the UE of a message transitioning the UE to RRC IDLE or RRC INACTIVE (e.g. RRC Release message including a suspend configuration, or with the suspend configuration absent);• Reception of an indication from the UE that the UE has entered RRC IDLE or RRC INACTIVE e.g. RLC acknowledgements in response to an RRC Release message;• Reception of an indication that the UE has re-established the connection in another network node that is not the first network node and not the second network node e.g. A Context release (in case the UE performed re-establishment in another node and the target node triggers a UE context release);• Determining that the UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage.• Reception of an RRC Measurement Reporting including measurement(s) of one or more cell(s) based on which the first network node determines to re-configure LTM candidate cell(s) for the UE, which may lead to release an existing number of LTM candidate cell(s).• Reception of an RRC Reconfiguration Complete message from the UE in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s) associated to the second network node.• The UE entered RRC CONNECTED.

[0094] The procedure for performing inter-CU LTM configuration release for the UE may include a release of the inter-CU LTM configuration in a second network node that controls at least parts of the inter-CU LTM configuration to be released.

[0095] The first network node transmits, to the second network node, a request message, such as a HANDOVER CANCEL message or a new type of message, that indicates release of at least one inter-CU LTM configuration for the UE. The first network node may include in the request message indicating release to the second network node a cause value, associated to one of the triggers which has triggered the request for release e.g. UE entering RRC IDLE or RRC INACTIVE, LTM execution in another candidate node, etc.

[0096] The second network node releases the indicated inter-CU LTM configuration for the UE. In one example, the second network node uses a distributed CU / DU RAN architecture. In this case the second network node may be divided into a second CU and a second DU. In this example, the second CU receives the HANDOVER CANCEL message from the first network node and may further request a release of a first part of the inter-CU LTM configuration (such as lower layer information) in a second DU. The second CU may release a second part of the inter-CU LTM configuration (such as higher layer information).

[0097] In one example, the request message that indicates release of at least one inter-CU LTM configuration received by the second network node does not require a response message, for example when the request message is a as a HANDOVER CANCEL message. In another example, the request message requires a response to confirm the release of the at least one inter-CU LTM configuration for the UE.

[0098] The first network node also transmits a request message to the UE that indicates release of the at least one inter-CU LTM configuration in the UE. In one example, this request message is an RRCReconfiguration message. The UE then releases the indicated at least one inter-CU LTM configuration and responds to the first network node, such as with a RRCReconfigurationComplete message, to confirm that the inter-CU LTM configuration has been released.

[0099] Further detail regarding these methods is set out below, in Figures 3 and 8 (in respect of the UE), Figures 4 and 9 (in respect of the first network node) and Figures 5 and 10 (in respect of the second network node). Enumerated embodiments, which correspond to the methods for the UE, the first network node and the second network node respectively, are set out as Al to A4, and group A embodiments towards the end of the disclosure; Bl to B5 and group Bembodiments towards the end of the disclosure; and Cl to C5 and group B embodiments towards the end of the disclosure. Example signalling diagrams are shown in Figures 6 and 7.

[0100] Figure 3 depicts a method in accordance with particular embodiments. The method of Figure 3 may be performed by a UE or wireless device (e.g. the UE 1212 or UE 1300 as described later with reference to Figures 12 and 13 respectively). The method of Figure 3 may be complementary to methods described below with respect to a first network node (e.g., a serving base station) and a second network node (e.g., a base station serving a candidate cell) in Figures 4 and / or 5.

[0101] The method begins at step 302, in which the UE receives, from a network node (such as a serving base station), a message comprising a request for the user equipment to release a configuration for use in connecting to and / or communicating with a candidate cell following a lower-layer cell mobility procedure. For example, the request may correspond to an instruction for the UE to release the configuration (e.g., with which the UE is expected to comply) or an optional request (e.g., with which the UE may comply). See step 630 in Figure 6 and / or steps 744 and 746 in Figure 7 for examples of this step.

[0102] The UE may therefore have been previously configured (by the network node or a different network node) with one or more configurations for use in connecting to and / or communicating with candidate cell(s) following a lower-layer cell mobility procedure to the candidate cell(s). The message may comprise a request for the UE to release one or more of these previously configured configurations. The configuration may correspond to an RRC configuration, for example, and may comprise a full configuration or a delta configuration defining one or more differences relative to a reference configuration. The configuration may additionally or alternatively comprise one of: a configuration for a connection to a standalone network node; a configuration for a connection to a master-cell group network node; and a configuration for a connection to a secondary-cell group network node. The message itself may comprise an RRCReconfiguration message.

[0103] The lower-layer cell mobility procedure may comprise an LTM procedure, e.g., a mobility procedure which is triggered upon receipt of, via lower-layer signalling from a source network node, a command to switch to the candidate cell. The lower-layer signalling may comprise one or more of LI and L2 signalling, such as PHY or MAC signalling.

[0104] In embodiments of the disclosure, the candidate cell is served by a different base station and / or a different CU than the source cell. In the latter case, the candidate cell is served by a base station having a distributed architecture. In either case, the lower-layer cell mobilityprocedure may be termed an inter-CU LTM procedure, the configuration may therefore also comprise an inter-CU LTM configuration.

[0105] The configurations for inter-CU lower-layer cell mobility are different to configurations for inter-DU intra-CU and intra-DU lower-layer cell mobility.

[0106] For example, the configuration may comprise information that enables the user equipment to refresh one or more security keys (e.g., a master key for a network node serving the candidate cell) for use in connecting to and / or communicating with the candidate cell. Such information may comprise one or more of an indication of a master key update parameter; an indication of one or more security algorithms to be used by the user equipment to derive one or more user plane keys and / or one or more control plane keys. The configuration may additionally comprise an indication of one or more source cells, with the UE determining whether to refresh the one or more security keys based on whether or not the lower-layer mobility procedure was from one of the one or more source cells. That is, the indication of one or more source cells may indicate to the UE whether or not to perform the security key change when executing an LTM cell switch. The indication of one or more source cells comprises one or more of one or more cell IDs; one or more physical cell identifiers; one or more source cell configuration identifiers; and an identifier of a group of one or more cells.

[0107] The configuration may additionally or alternatively comprise a measurement configuration comprising an instruction for the user equipment to perform measurements on transmissions by the candidate cell. In such a case, the UE may transmit a report message to the network node, comprising an indication of values derived from the measurements on transmissions by the candidate cell. The measurement configuration may comprise an indication of whether the user equipment is instructed to autonomously estimate timing advance for the candidate cell.

[0108] The configuration may additionally or alternatively comprise an indication to perform lower-layer re-establishment for one or more radio bearers upon connection to the candidate cell, e.g., PDCP re-establishment.

[0109] The message may be transmitted by the network node, and received by the UE, responsive to one or more of the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cell are above or below a threshold; the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE re-establishing a connection in a second network node thatdoes not serve the candidate cell; the UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage or has become reachable again; the user equipment transmitting, to a network node, measurement report (e.g., RRC Measurement Report) including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message.[HO] In step 304, responsive to receiving the message, the UE releases the configuration. For example, the UE may delete the configuration from its memory. See step 632 in Figure 6 and / or step 748 in Figure 7 for examples of this step.[Hl] In step 306, the UE transmits, to the network node, a response message confirming release of the configuration. The response message may comprise, for example, an RRCReconfigurationComplete message. See step 634 in Figure 6 and / or step 750 in Figure 7 for examples of this step.

[0112] For the avoidance of doubt, the following numbered paragraphs set out embodiments of the disclosure:Al . Method for a UE to perform inter-CU LTM configuration release, comprising, receiving, from a first network node, a request message indicating release of at least one inter-CU LTM configuration, releasing at least one inter-CU LTM configuration and transmitting, to the first network node, a response message confirming the release of at least one inter-CU LTM configuration.A2. The method in Al, wherein the at least one inter-CU LTM configuration includes at least one of:• information to perform security key refresh, such as one of the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes SecurityConfig with Security AlgorithmConfig;• Indication to perform a full configuration, e.g. the RRC field fullConfig;• Indication to perform L2 re-establishment, such as an indication to perform PDCP reestablishment for one or multiple bearers;• An identifier of the inter-CU LTM configuration;• Indication to perform UE based TA measurements, such as an indication on whether the UE is configured to autonomously estimated the TA or not.A3. The method in Al or A2, wherein the reception of the request message was in response to one or more of the following:• Transmission, to a network node, of a measurement report that indicates that a certain cell is above or below a certain threshold;• the UE has successfully performed LTM towards a network node;• Reception, from a network node, of an LTM Cell switch command;• The UE is about to enter RRC IDLE or RRC INACTIVE;• Re-establishment of the connection in another network node that is not the first network node and not the second network node;• The UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage or has become reachable again;• Transmission, to a network node, of an RRC Measurement Reporting including measurement(s) of one or more cell(s);• Transmission, to a network node, of an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s);• The UE entered RRC CONNECTED;• Transmission of an RLF-related RRC message received from the UE, such as an SCG failure information, Failure information, or MCG failure information message.A4. The method in any one of Al to A3, wherein release of an inter-CU LTM configuration means releasing a standalone network node configuration, or, if dual connectivity is configured, an MCG configuration, or an SCG configuration, or both an MCG and SCG configuration.

[0113] Figure 4 depicts a method in accordance with particular embodiments. The method of Figure 4 may be performed by a first network node (e.g. the network node 1210 or network node 1400 as described later with reference to Figures 12 and 14 respectively). The method may comprise interactions with a UE and / or a second network node. The first network node may act as a serving base station for the UE (e.g., as part of MCG, SCG, etc). The second network node may comprise a base station (or a component of a base station, such as a CU or DU) serving a candidate cell for which the UE has previously been configured with a lower- layer cell mobility configuration. Corresponding methods in the UE and the second network node are described with respect to Figures 3 and 5 respectively.

[0114] The method begins at step 402, in which the first network node transmits, to one or more of the UE and the second network node, a message comprising a request for the one or moreof the UE and the second network node to release a configuration for use in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure by the UE to the candidate cell. For example, the request may correspond to an instruction for the UE and / or the second network node to release the configuration (e.g., with which the UE or second network node is expected to comply) or an optional request (e.g., with which the UE or second network node may comply). See step 626 in Figure 6 and / or step 738 in Figure 7 for examples of this step where the message is transmitted to the second network node; see step 630 in Figure 6 and / or steps 744 and 746 in Figure 7 for examples of this step where the message is transmitted to the UE.

[0115] The UE may therefore have been previously configured (by the first network node or a different network node) with one or more configurations for use in connecting to and / or communicating with candidate cell(s) following a lower-layer cell mobility procedure to the candidate cell(s). See steps 608 to 622 in Figure 6 and / or steps 712 to 734 in Figure 7 for examples of this process. The message transmitted to the UE may comprise a request for the UE to release one or more of these previously configured configurations. The configuration may correspond to an RRC configuration, for example, and may comprise a full configuration or a delta configuration defining one or more differences relative to a reference configuration. The configuration may additionally or alternatively comprise one of: a configuration for a connection to a standalone network node; a configuration for a connection to a master-cell group network node; and a configuration for a connection to a secondary-cell group network node. The message itself may comprise an RRCReconfiguration message.

[0116] The second network node may control at least part of the configuration provided to the UE for the candidate cell served by the second network node. That is, the second network node may provide one or more parameters (or all of the parameters) to be used within the configuration for the candidate cell. Initially these may be provided to the network node that is configuring the UE with the lower-layer cell mobility configurations (which may be the first network node or a different node, as noted above). The second network node may additionally reserve resources corresponding to the configuration (e.g., temporary identifiers, UE-specific random access preambles and resources, etc), such that the UE can handover promptly and correctly to the second network node upon executing the cell mobility procedure. The message transmitted to the second network node may comprise a request for the second network node to release this configuration and / or these resources. The message may comprise a HANDOVER CANCEL message.

[0117] Additionally or alternatively, the message may comprise an indication of a cause for release of the configuration. The message may be transmitted by the first network node responsive to one or more of: the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cell are above or below a threshold (e.g., the source cell, or a different candidate cell to the whose configuration is being released); the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE re-establishing a connection in a second network node that does not serve the candidate cell; the UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage or has become reachable again; the user equipment transmitting, to a network node, measurement report (e.g., RRC Measurement Report) including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message.

[0118] The lower-layer cell mobility procedure may comprise an LTM procedure, e.g., a mobility procedure which is triggered upon receipt of, via lower-layer signalling from a source network node, a command to switch to the candidate cell. The lower-layer signalling may comprise one or more of LI and L2 signalling, such as PHY or MAC signalling.

[0119] In embodiments of the disclosure, the candidate cell is served by a different base station and / or a different CU than the source cell. In the latter case, the candidate cell is served by a base station having a distributed architecture. In either case, the lower-layer cell mobility procedure may be termed an inter-CU LTM procedure, the configuration may therefore also comprise an inter-CU LTM configuration.

[0120] The configurations for inter-CU lower-layer cell mobility are different to configurations for inter-DU intra-CU and intra-DU lower-layer cell mobility.

[0121] For example, the configuration may comprise information that enables the user equipment to refresh one or more security keys (e.g., a master key for a network node serving the candidate cell) for use in connecting to and / or communicating with the candidate cell. Such information may comprise one or more of: an indication of a master key update parameter; an indication of one or more security algorithms to be used by the user equipment to derive oneor more user plane keys and / or one or more control plane keys. The configuration may additionally comprise an indication of one or more source cells, with the UE determining whether to refresh the one or more security keys based on whether or not the lower-layer mobility procedure was from one of the one or more source cells. That is, the indication of one or more source cells may indicate to the UE whether or not to perform the security key change when executing an LTM cell switch. The indication of one or more source cells comprises one or more of one or more cell IDs; one or more physical cell identifiers; one or more source cell configuration identifiers; and an identifier of a group of one or more cells.

[0122] The configuration may additionally or alternatively comprise a measurement configuration comprising an instruction for the user equipment to perform measurements on transmissions by the candidate cell. In such a case, the UE may transmit a report message to the network node, comprising an indication of values derived from the measurements on transmissions by the candidate cell. The measurement configuration may comprise an indication of whether the user equipment is instructed to autonomously estimate timing advance for the candidate cell.

[0123] The configuration may additionally or alternatively comprise an indication to perform lower-layer re-establishment for one or more radio bearers upon connection to the candidate cell, e.g., PDCP re-establishment.

[0124] In step 404, optionally, the first network node receives a response message from the one or more of the UE and the second network node confirming release of the configuration (see step 634 in Figure 6, for example). Where the response message is received from the UE, the response message may comprise an RRCReconfigurationComplete message. Where the response message is received from the second network node, the response message may comprise a different message.

[0125] In step 406, as an alternative to step 404, the first network node refrains from monitoring for a response message from the second network node confirming release of the configuration. That is, the second network node may not transmit a response message to confirm release of the configuration and therefore the first network node should not monitor for receipt of such a response message.

[0126] For the avoidance of doubt, the following numbered paragraphs set out embodiments of the disclosure:B 1. Method for a first network node, such as a first gNB or a first CU, to perform inter-CU LTM configuration release for a UE, comprising, transmitting, to a second network node, a request message to perform release of at least one inter-CU LTM configuration.B2. The method in Bl wherein the first network node receives, from a second network node, a response message confirming the release of at least one inter-CU LTM configuration.B3. The method in Bl or B2, wherein the at least one inter-CU LTM configuration includes at least one of:• information to perform security key refresh, such as one of the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes SecurityConfig with Security AlgorithmConfig;• Indication to perform a full configuration, e.g. the RRC field fullConfig;• Indication to perform L2 re-establishment, such as an indication to perform PDCP reestablishment for one or multiple bearers;• An identifier of the inter-CU LTM configuration;• Indication to perform UE based TA measurements, such as an indication on whether the UE is configured to autonomously estimated the TA or not.B4. The method in any one of Bl to B3, wherein the request message is transmitted in response to one or more of the following:• Reception of a measurement report, from the UE, by the first network node, that indicates that a certain cell is above or below a certain threshold;• Reception of an indication (e.g. from a third network node) that the UE has successfully performed LTM towards the third network node. An example of the indication is a Handover Success message, indicating a successful LTM execution;• Transmission of an LTM Cell switch command to the UE indicating an LTM candidate cell of a third network node;• Determining that the UE is to enter RRC IDLE or RRC IN ACTIVE;• Transmission to the UE of a message transitioning the UE to RRC IDLE or RRC INACTIVE (e.g. RRC Release message including a suspend configuration, or with the suspend configuration absent);• Reception of an indication from the UE that the UE has entered RRC IDLE or RRC INACTIVE e.g. RLC acknowledgements in response to an RRC Release message;• Reception of an indication that the UE has re-established the connection in another network node that is not the first network node and not the second network node e.g. A Context release (in case the UE performed re-establishment in another node and the target node triggers a UE context release);• Determining that the UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage;• Reception of an RRC Measurement Reporting including measurement(s) of one or more cell(s) based on which the first network node determines to re-configure LTM candidate cell(s) for the UE, which may lead to release an existing number of LTM candidate cell(s);• Reception of an RRC Reconfiguration Complete message from the UE in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s) associated to the second network node;• Reception of an RLF -related RRC message received from the UE, such as an SCG failure information, Failure information, or MCG failure information message.B5. The method in any one of Bl to B4, wherein the request message includes a cause value, associated to one of the triggers which has triggered the request for release.B6. The method in any one of Bl to B5, wherein the first network node is a standalone network node, or, if dual connectivity is configured, controls an MCG, or an SCG.

[0127] Figure 5 depicts a method in accordance with particular embodiments. The method of Figure 5 may be performed by a network node (e.g. the network node 1210 or network node 1400 as described later with reference to Figures 12 and 14 respectively). The method may comprise interactions with a UE and / or a first network node. The first network node may act as a serving base station for the UE (e.g., as part of MCG, SCG, etc). The second network node may comprise a base station (or a component of a base station, such as a CU or DU) serving a candidate cell for which the UE has previously been configured with a lower-layer cell mobility configuration. Corresponding methods in the UE and the first network node are described with respect to Figures 3 and 4 respectively.

[0128] The method begins at step 502, in which the second network node receives, from the first network node, a message comprising a request for the second network node to release a configuration for use in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure by the UE to the candidate cell. For example, the request may correspond to an instruction for the secondnetwork node to release the configuration (e.g., with which the second network node is expected to comply) or an optional request (e.g., with which the second network node may comply). See step 626 in Figure 6 and / or step 738 in Figure 7 below for examples of this step.

[0129] The UE may therefore have been previously configured (by the first network node or a different network node) with one or more configurations for use in connecting to and / or communicating with candidate cell(s) following a lower-layer cell mobility procedure to the candidate cell(s). The configuration may correspond to an RRC configuration, for example, and may comprise a full configuration or a delta configuration defining one or more differences relative to a reference configuration. The configuration may additionally or alternatively comprise one of a configuration for a connection to a standalone network node; a configuration for a connection to a master-cell group network node; and a configuration for a connection to a secondary-cell group network node.

[0130] The second network node may control at least part of the configuration provided to the UE for the candidate cell served by the second network node. That is, the second network node may provide one or more parameters (or all of the parameters) to be used within the configuration for the candidate cell. Initially these may be provided to the network node that is configuring the UE with the lower-layer cell mobility configurations (which may be the first network node or a different node, as noted above). See step 616 in Figure 6 below, for example. The second network node may additionally reserve resources corresponding to the configuration (e.g., temporary identifiers, UE-specific random access preambles and resources, etc), such that the UE can handover promptly and correctly to the second network node upon executing the cell mobility procedure. The message transmitted to the second network node may comprise a request for the second network node to release this configuration and / or these resources. The message may comprise a HANDOVER CANCEL message.

[0131] Additionally or alternatively, the message may comprise an indication of a cause for release of the configuration. The message may be transmitted by the first network node responsive to one or more of the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cell are above or below a threshold (e.g., the source cell, or a different candidate cell to the whose configuration is being released); the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE re-establishing a connection in a second network node that does not serve the candidate cell; the UE is unreachable e.g. has triggered a Radio LinkFailure and / or is out of coverage or has become reachable again; the user equipment transmitting, to a network node, measurement report (e.g., RRC Measurement Report) including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message.

[0132] The lower-layer cell mobility procedure may comprise a LTM procedure, e.g., a mobility procedure which is triggered upon receipt of, via lower-layer signalling from a source network node, a command to switch to the candidate cell. The lower-layer signalling may comprise one or more of LI and L2 signalling, such as PHY or MAC signalling.

[0133] In embodiments of the disclosure, the candidate cell is served by a different base station and / or a different CU than the source cell. In the latter case, the candidate cell is served by a base station having a distributed architecture. In either case, the lower-layer cell mobility procedure may be termed an inter-CU LTM procedure, the configuration may therefore also comprise an inter-CU LTM configuration.

[0134] The configurations for inter-CU lower-layer cell mobility are different to configurations for inter-DU intra-CU and intra-DU lower-layer cell mobility.

[0135] For example, the configuration may comprise information that enables the user equipment to refresh one or more security keys (e.g., a master key for a network node serving the candidate cell) for use in connecting to and / or communicating with the candidate cell. Such information may comprise one or more of: an indication of a master key update parameter; an indication of one or more security algorithms to be used by the user equipment to derive one or more user plane keys and / or one or more control plane keys. The configuration may additionally comprise an indication of one or more source cells, with the UE determining whether to refresh the one or more security keys based on whether or not the lower-layer mobility procedure was from one of the one or more source cells. That is, the indication of one or more source cells may indicate to the UE whether or not to perform the security key change when executing an LTM cell switch. The indication of one or more source cells comprises one or more of: one or more cell IDs; one or more physical cell identifiers; one or more source cell configuration identifiers; and an identifier of a group of one or more cells.

[0136] The configuration may additionally or alternatively comprise a measurement configuration comprising an instruction for the user equipment to perform measurements on transmissions by the candidate cell. In such a case, the UE may transmit a report message to the network node, comprising an indication of values derived from the measurements on transmissions by the candidate cell. The measurement configuration may comprise an indication of whether the user equipment is instructed to autonomously estimate timing advance for the candidate cell.

[0137] The configuration may additionally or alternatively comprise an indication to perform lower-layer re-establishment for one or more radio bearers upon connection to the candidate cell, e.g., PDCP re-establishment.

[0138] In step 504, responsive to receiving the message, the second network node releases the configuration. For example, the second network node may delete the configuration and / or the resources associated with the configuration from its memory. See step 628 in Figure 6 for an example of this step.

[0139] In step 506, the second network node optionally transmits, to the first network node, a response message confirming release of the configuration. Alternatively, step 506 may comprise the second network node refraining from transmitting, to the first network node, a response message confirming release of the configuration.

[0140] Where the second network node comprises a CU, the method may further comprise the CU transmitting to the DU an instruction for the DU to release the configuration. See step 740 in Figure 7 below for an example of this process.

[0141] For the avoidance of doubt, the following numbered paragraphs set out embodiments of the disclosure:Cl. Method for a second network node, such as a second gNB or a second CU, to perform inter-CU LTM configuration release for a UE, comprising, receiving, from a first network node, a request message to perform release of at least one inter-CU LTM configuration. The request message may be Handover Cancel, an MN-initiated or SN-initiated S-NG-RAN node Release, the Failure indication, and / or the SCG Failure Information Report. Alternatively, the request message may be a new type of message.C2. The method in Cl wherein the second network node transmits, to the first network node, a response message confirming the release of at least one inter-CU LTM configuration. In one example the response message is a new type of messageC3. The method in Cl or C2, wherein the at least one inter-CU LTM configuration includes at least one of:• information to perform security key refresh, such as one of the RRC IE MasterKeyUpdate or a RRC IE RadioBearerConfig that includes SecurityConfig with Security AlgorithmConfig;• Indication to perform a full configuration, e.g. the RRC field fullConfig;• Indication to perform L2 re-establishment, such as an indication to perform PDCP reestablishment for one or multiple bearers;• An identifier of the inter-CU LTM configuration;• Indication to perform UE based TA measurements, such as an indication on whether the UE is configured to autonomously estimated the TA or not.C4. The method in any one of Cl to C3, wherein the request message includes a cause value, associated to one of the triggers which has triggered the request for release.C5. The method in any one of Cl to C4, wherein the first network node is a standalone network node, or, in case dual connectivity is configured, controls an MCG, or an SCG.

[0142] Figure 6 illustrates a message sequence chart in one example of the disclosure. In this example, the UE 602 is connected to a first network node 604, here referred to as a serving gNB 604, and configured with at least one inter-CU LTM configuration in a second network node 606, here referred to as a candidate gNB 606, and then the serving gNB performs inter- CU LTM configuration release for the UE.

[0143] Referring to Figure 6, the main steps in this example are as follows.

[0144] Step 608: The serving gNB 604 receives, from the UE 202, an L3 measurement report message, such as an MeasurementReport RRC message.

[0145] Step 610: The serving gNB 604 decides to perform setup of an inter-CU LTM configuration for the UE 602.

[0146] Step 612: The serving gNB 604 transmits, to a candidate gNB 606, a request message to perform setup of an inter-CU LTM configuration. In this example, the message is a HANDOVER REQUEST message.

[0147] Step 614: The candidate gNB 606 creates at least inter-CU LTM configuration for the UE 602.

[0148] Step 616: The candidate gNB 606 transmits, to the serving gNB 604, a response message including at least one inter-CU LTM configuration for the UE 602. In this example, the message is a HANDOVER REQUEST ACKNOWLEDGE message.

[0149] Step 618: The serving gNB 604 transmits, to the UE 602, a reconfiguration message, such as an RRCReconfiguration message, including an inter-CU LTM configuration for the UE 602.

[0150] Step 620: The UE 602 stores the received inter-CU LTM configuration.

[0151] Step 622: The UE 602 transmits, to the serving gNB 604, a response message, such as an RRCReconfigurationComplete message to confirm that the inter-CU LTM configuration has been received.

[0152] Step 624: The serving gNB 604 decides to perform release of an inter-CU LTM configuration for the UE 602. The trigger for performing the release may be for example that the serving gNB 604 has received a measurement report from the UE 602, and determines to re-configure LTM candidate cell(s) for the UE 602, which may lead to release an existing number of LTM candidate cell(s), the UE 602 entering RRC IDLE or RRC INACTIVE, receiving indication about the UE 602 has performed an LTM cell switch to a third network node (e.g. a target gNB), the UE 602 has re-established the connection, determining that the UE 602 is unreachable, etc.

[0153] Step 626: The serving gNB 604 transmits, to the candidate gNB 606, a request message to perform release of an inter-CU LTM configuration for the UE 602. In this example, the request message is a HANDOVER CANCEL message. In another example, the request message is a new type of message. In one example, the request message includes a cause value associated to one of the triggers which has triggered the request for release.

[0154] Step 628: The candidate gNB 606 releases an inter-CU LTM configuration for the UE 602 as indicated by the received request message. In this example, the request message (e.g. HANDOVER CANCEL) does not require a response. In another example, such as when the request message is a new type of message, the candidate gNB 606 transmits a response message to the serving gNB 604 as a confirmation of the release.

[0155] Step 630: The serving gNB 604 transmits, to the UE 602, a request message indicating release of at least one inter-CU LTM configuration, such as an RRCReconfiguration message. Note that this step may be alternatively performed before, or in parallel with, steps 626-630. If the UE 602 is not reachable (e.g. it has entered RRC IDLE or RRC INACTIVE) the steps 630-634 may be omitted.

[0156] Step 632: The UE 602 releases at least one inter-CU LTM configuration according to the received request message.

[0157] Step 634: The UE 602 transmits, to the serving gNB 604, a response message confirming the release of at least one inter-CU LTM configuration, such as an RRCReconfigurationComplete message.

[0158] Figure 7 illustrates a message sequence chart in one example of the disclosure. In this example, both the first network node (e.g. serving gNB) and the second network node (e.g. candidate gNB) uses a distributed CU / DU RAN architecture. The UE 702 is connected to the serving gNB (i.e. serving CU 704 and serving DU 706) and configured with at least one inter- CU LTM configuration in the candidate gNB (i.e. candidate CU 708 and candidate DU 710), and then the serving CU 704 triggers inter-CU LTM configuration release for the UE 702.

[0159] Referring to Figure 7, the main steps in this example are as follows.

[0160] Step 712: The serving DU 706 in the serving gNB receives, from the UE 702, an L3 measurement report message, such as an MeasurementReport RRC message.

[0161] Step 714: The serving DU 706 forwards the L3 measurement report to the serving CU 704.

[0162] Step 716: The serving CU 704 decides to perform setup of an inter-CU LTM configuration for the UE 702.

[0163] Step 718: The serving CU 704 transmits to the candidate CU 708 in a candidate gNB, a request message to perform setup of an inter-CU LTM configuration. In this example, the message is a HANDOVER REQUEST message.

[0164] Step 720: The candidate CU 708 sends a request message to the candidate DU 710 to perform setup of an inter-CU LTM configuration. In this example, the message is a UE CONTEXT SETUP REQUEST message.

[0165] Step 722: If the candidate DU 710 accepts the request, it provides at least one, or a part of (such as lower-layer information), inter-CU LTM configuration in, for example, the UE CONTEXT SETUP RESPONSE message.

[0166] Step 724: The candidate CU 708 may add other information (such as higher layer information) to the received inter-CU LTM configuration sends at least one inter-CU LTM configuration to the serving CU 704 using the HANDOVER REQUEST ACKNOWLEDGE message.

[0167] Step 726: The serving CU 704 prepares the RRCReconfiguration message including an at least one inter-CU LTM configuration and sends it to the serving DU 706.

[0168] Step 728: The serving DU 706 sends to the UE 702 the RRCReconfiguration message including an at least one inter-CU LTM configuration.

[0169] Step 730: The UE 702 stores the received at least one inter-CU LTM configuration.

[0170] Step 732-734: The UE 702 completes the reconfiguration procedure by sending the RRCReconfigurationComplete message to the serving DU 706, and the serving DU 706 forwards it to the serving CU 704.

[0171] Step 736: The serving CU 704 decides to perform release of an inter-CU LTM configuration for the UE 702.

[0172] Step 738: The serving CU 704 transmits, to the candidate CU 708 in the candidate gNB, a request message to perform release of an inter-CU LTM configuration for the UE 702. In this example, the request message is a HANDOVER CANCEL message. In another example, the request message is a new type of message. In this example, the request message (e.g. HANDOVER CANCEL) does not require a response. In another example, such as when the request message is a new type of message, the candidate CU 708 transmits a response message to the serving CU 704 as a confirmation of the release.

[0173] Step 740: The candidate CU 708 sends a request message to the candidate DU 710 to perform release of an inter-CU LTM configuration for the UE 702. In this example, the message is a UE CONTEXT RELEASE COMMAND message.

[0174] Step 742: The candidate DU 710 releases the inter-CU LTM configuration for the UE 702, or a part of the inter-CU LTM configuration (such as lower-layer information) and responds with a UE CONTEXT RELEASE COMPLETE message that confirms the release of the inter-CU LTM configuration for the UE 702. The candidate CU 708 may also release inter- CU LTM configuration for the UE 702, or a part of it (such as higher layer information).

[0175] Step 744: The serving CU 704 prepares the RRCReconfiguration message indicating release of at least one inter-CU LTM configuration and sends it to the serving DU 706. Note that the steps 744-746 may be alternatively performed before, or in parallel with, steps 738- 742.

[0176] Step 746: The serving DU 706 sends to the UE 702 the RRCReconfiguration message.

[0177] Step 748: The UE 702 releases at least one inter-CU LTM configuration according to the received RRCReconfiguration message.

[0178] Step 750: The UE 702 transmits, to the serving DU 706, a RRCReconfigurationComplete message confirming the release of at least one inter-CU LTM configuration.

[0179] Step 752: The serving DU 706 forwards the received RRCReconfigurationComplete message to the serving CU 704.

[0180] Figure 8 illustrates a flow chart with the main steps performed by the UE in one example of the disclosure.

[0181] Referring to Figure 8, the main steps performed by the UE in this example are as follows:Step 802: The UE receives, from a first network node, a request message indicating release of at least one inter-CU LTM configuration.Step 804: The UE releases at least one inter-CU LTM configuration according to the received request message.Step 806: The UE transmits, to the first network node, a response message confirming the release of at least one inter-CU LTM configuration.

[0182] Figure 9 illustrates a flow chart with the main steps performed by the first network node in one example of the disclosure.

[0183] Referring to Figure 9, the main steps performed by the first network node in this example are as follows:Step 902: The first network node, transmits, to a second network node, a request message to indicating release of at least one inter-CU LTM configuration. In this example, the first network node may not receive a response from the second network node as a confirmation of the release, and assumes the procedure succeeds. In another example, the first network node receives a response from the second network node as a confirmation of the release.Step 904: The first network node transmits, to the UE, a request message indicating release of at least one inter-CU LTM configuration. Note that this step may be alternatively performed before, or in parallel with, the previous step.Step 906: The first network node receives, from the UE, a response message confirming the release of at least one inter-CU LTM configuration.

[0184] Error! Reference source not found.10 illustrates a flow chart with the main steps performed by the second network node in one example of the disclosure.

[0185] Referring to Figure 10, the main steps performed by the second network node in this example are as follows.Step 1002: The second network node receives, from a first network node, a request message indicating release of at least one inter-CU LTM configuration.Step 1004: The second network node releases at least one inter-CU LTM configuration according to the received request message. In this example, the second network node does not transmit a response to the first network node as a confirmation of the release. In another example, the second network node transmits a response to the first network node as a confirmation of the release.

[0186] Below an implementation in the 3GPP XnAP Technical Specification (TS), TS 38.423 V17.6.0, is illustrated for one example of the disclosure (new text is underlined). The implementation involves the procedures shown in Figure 11, which illustrates signaling between a source NG-RAN node 1102 and a target NG-RAN node 1104 (particularly signalling for a “Handover Cancel, successful operation” scenario). In Figure 11, the source NG-RAN node 1102 transmits (at step 1106), to the target NG-RAN node 1104, a handover cancel message.8.2 Basic mobility procedures8.2.3 Handover Cancel8.2.3.1 GeneralThe Handover Cancel procedure is used to enable a source NG-RAN node to cancel an ongoing handover preparation or an already prepared handover.The procedure uses UE-associated signalling.8.2.3.2 Successful Operation[Text and figure omitted]If the LTM Candidate Cells To Be Cancelled List IE is contained in the HANDOVER CANCEL message, the target NG-RAN node shall consider that the source NG-RAN node is cancelling only the handover associated to the LTM candidate cells identified by the included NG-RAN CGI and associated to the same UE-associated signaling connection identified by the Source NG-RAN node UE XnAP ID IE, [Text omitted]8.2.3.3 Unsuccessful Operation[Not applicable.]8.2.3.4 Abnormal Conditions[Text omitted]If the LTM Candidate Cells To Be Cancelled List IE is included in the HANDOVER CANCEL message and the handover is not associated to LTM, the target NG-RAN node shall ignore the LTM Candidate Cells To Be Cancelled List IE,If one or more candidate cells in the LTM Candidate Cells To Be Cancelled List IE included in the HANDOVER CANCEL message were not prepared using the same UE- associated signaling connection, the target NG-RAN node shall ignore those nonassociated candidate cells.[Text omitted]9.1.1 Messages for Basic Mobility Procedures9.1.1.6 HANDOVER CANCELThis message is sent by the source NG-RAN node to the target NG-RAN node to cancel an ongoing handover.Direction: source NG-RAN nodetarget NG-RAN node.

[0187] Figure 12 shows an example of a communication system 1200 in accordance with some embodiments.

[0188] In the example, the communication system 1200 includes a telecommunication network 1202 that includes an access network 1204, such as a radio access network (RAN), and a core network 1206, which includes one or more core network nodes 1208. The access network 1204 includes one or more access network nodes, such as network nodes 1210a and 1210b (one or more of which may be generally referred to as network nodes 1210), or any other similar 3rdGeneration Partnership Project (3 GPP) access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, thetelecommunication network 1202 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network 1202 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network 1202, including one or more network nodes 1210 and / or core network nodes 1208.

[0189] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O- CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. The network nodes 1210 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 1212a, 1212b, 1212c, and 1212d (one or more of which may be generally referred to as UEs 1212) to the core network 1206 over one or more wireless connections.

[0190] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 1200 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. The communication system 1200 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0191] The UEs 1212 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with the network nodes 1210 and other communication devices. Similarly, the network nodes 1210 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 1212 and / or with other network nodes or equipment in the telecommunication network 1202 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunication network 1202.

[0192] In the depicted example, the core network 1206 connects the network nodes 1210 to one or more hosts, such as host 1216. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 1206 includes one more core network nodes (e.g., core network node 1208) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 1208. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0193] The host 1216 may be under the ownership or control of a service provider other than an operator or provider of the access network 1204 and / or the telecommunication network 1202, and may be operated by the service provider or on behalf of the service provider. The host 1216 may host a variety of applications to provide one or more services. Examples of such applications include the provision of live and / or pre-recorded audio / video content, data collection services, for example, retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0194] As a whole, the communication system 1200 of Figure 12 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include,but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0195] In some examples, the telecommunication network 1202 is a cellular network that implements 3 GPP standardized features. Accordingly, the telecommunications network 1202 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1202. For example, the telecommunications network 1202 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs.

[0196] In some examples, the UEs 1212 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 1204 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1204. Additionally, a UE may be configured for operating in single- or multi -RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0197] In the example illustrated in Figure 12, the hub 1214 communicates with the access network 1204 to facilitate indirect communication between one or more UEs (e.g., UE 1212c and / or 1212d) and network nodes (e.g., network node 1210b). In some examples, the hub 1214 may be a controller, router, a content source and analytics node, or any of the other communication devices described herein regarding UEs. For example, the hub 1214 may be a broadband router enabling access to the core network 1206 for the UEs. As another example, the hub 1214 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1210, or by executable code, script, process, or other instructions in the hub 1214. As another example, the hub 1214 may be a data collector that acts as temporary storage for UE data and, in someembodiments, may perform analysis or other processing of the data. As another example, the hub 1214 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 1214 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1214 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 1214 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0198] The hub 1214 may have a constant / persistent or intermittent connection to the network node 1210b. The hub 1214 may also allow for a different communication scheme and / or schedule between the hub 1214 and UEs (e.g., UE 1212c and / or 1212d), and between the hub 1214 and the core network 1206. In other examples, the hub 1214 is connected to the core network 1206 and / or one or more UEs via a wired connection. Moreover, the hub 1214 may be configured to connect to an M2M service provider over the access network 1204 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 1210 while still connected via the hub 1214 via a wired or wireless connection. In some embodiments, the hub 1214 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to the network node 1210b. In other embodiments, the hub 1214 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1210b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0199] Figure 13 shows a UE 1300 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless camera, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0200] A UE may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), orvehicle- to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0201] The UE 1300 includes processing circuitry 1302 that is operatively coupled via a bus 1304 to an input / output interface 1306, a power source 1308, a memory 1310, a communication interface 1312, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 13. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0202] The processing circuitry 1302 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 1310. The processing circuitry 1302 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 1302 may include multiple central processing units (CPUs). The processing circuitry 1302 may be operable to provide, either alone or in conjunction with other UE 1300 components, such as the memory 1310, UE 1300 functionality. For example, the processing circuitry 1302 may be configured to cause the UE 1302 to perform the methods as described with reference to one or more of Figures 3 and 8, the signalling of the UE in Figure 6, and / or the signalling of the UE in Figure 7.

[0203] In the example, the input / output interface 1306 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices.Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 1300. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0204] In some embodiments, the power source 1308 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 1308 may further include power circuitry for delivering power from the power source 1308 itself, and / or an external power source, to the various parts of the UE 1300 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1308. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1308 to make the power suitable for the respective components of the UE 1300 to which power is supplied.

[0205] The memory 1310 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 1310 includes one or more application programs 1314, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1316. The memory 1310 may store, for use by the UE 1300, any of a variety of various operating systems or combinations of operating systems.

[0206] The memory 1310 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital datastorage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘ SIM card.’ The memory 1310 may allow the UE 1300 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 1310, which may be or comprise a device-readable storage medium.

[0207] The processing circuitry 1302 may be configured to communicate with an access network or other network using the communication interface 1312. The communication interface 1312 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1322. The communication interface 1312 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 1318 and / or a receiver 1320 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 1318 and receiver 1320 may be coupled to one or more antennas (e.g., antenna 1322) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0208] In some embodiments, communication functions of the communication interface 1312 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / intemet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0209] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1312, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0210] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or controls a robotic arm performing a medical procedure according to the received input.

[0211] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are devices which are or which are embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and / or software in dependence on the intended application of the loT device in addition to other components as described in relation to the UE 1300 shown in Figure 13.

[0212] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of suchmonitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3 GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0213] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[0214] Figure 14 shows a network node 1400 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR. NodeBs (gNBs)), 0-RAN nodes or components of an 0-RAN node (e.g, 0-RU, 0-DU, O-CU).

[0215] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g, in an 0-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0216] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllerssuch as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0217] The network node 1400 includes processing circuitry 1402, a memory 1404, a communication interface 1406, and a power source 1408, and / or any other component, or any combination thereof. The network node 1400 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 1400 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 1400 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1404 for different RATs) and some components may be reused (e.g., a same antenna 1410 may be shared by different RATs). The network node 1400 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1400, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z- wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1400.

[0218] The processing circuitry 1402 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node 1400 components, such as the memory 1404, network node 1400 functionality. For example, the processing circuitry 1402 may be configured to cause the network node to perform the methods as described with reference to one or more of Figures 4, 5, 9 and 10, the signalling of the Serving gNB or the Candidate gNB in Figure 6, and / or the signalling of the Serving DU 706, the Serving CU 704, the Candidate DU 710 or the Candidate CU 708 in Figure 7.

[0219] In some embodiments, the processing circuitry 1402 includes a system on a chip (SOC). In some embodiments, the processing circuitry 1402 includes one or more of radio frequency (RF) transceiver circuitry 1412 and baseband processing circuitry 1414. In some embodiments, the radio frequency (RF) transceiver circuitry 1412 and the baseband processing circuitry 1414 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1412 and baseband processing circuitry 1414 may be on the same chip or set of chips, boards, or units.

[0220] The memory 1404 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 1402. The memory 1404 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry 1402 and utilized by the network node 1400. The memory 1404 may be used to store any calculations made by the processing circuitry 1402 and / or any data received via the communication interface 1406. In some embodiments, the processing circuitry 1402 and memory 1404 is integrated.

[0221] The communication interface 1406 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, the communication interface 1406 comprises port(s) / terminal(s) 1416 to send and receive data, for example to and from a network over a wired connection. The communication interface 1406 also includes radio front-end circuitry 1418 that may be coupled to, or in certain embodiments a part of, the antenna 1410. Radio front-end circuitry 1418 comprises filters 1420 and amplifiers 1422. The radio front-end circuitry 1418 may be connected to an antenna 1410 and processing circuitry 1402. The radio front-end circuitry may be configured to condition signals communicated between antenna 1410 and processing circuitry 1402. The radio front-end circuitry 1418 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 1418 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination offilters 1420 and / or amplifiers 1422. The radio signal may then be transmitted via the antenna 1410. Similarly, when receiving data, the antenna 1410 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1418. The digital data may be passed to the processing circuitry 1402. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0222] In certain alternative embodiments, the network node 1400 does not include separate radio front-end circuitry 1418, instead, the processing circuitry 1402 includes radio front-end circuitry and is connected to the antenna 1410. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1412 is part of the communication interface 1406. In still other embodiments, the communication interface 1406 includes one or more ports or terminals 1416, the radio front-end circuitry 1418, and the RF transceiver circuitry 1412, as part of a radio unit (not shown), and the communication interface 1406 communicates with the baseband processing circuitry 1414, which is part of a digital unit (not shown).

[0223] The antenna 1410 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 1410 may be coupled to the radio front-end circuitry 1418 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 1410 is separate from the network node 1400 and connectable to the network node 1400 through an interface or port.

[0224] The antenna 1410, communication interface 1406, and / or the processing circuitry 1402 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, the antenna 1410, the communication interface 1406, and / or the processing circuitry 1402 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0225] The power source 1408 provides power to the various components of network node 1400 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 1408 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1400 with power for performing the functionality described herein. For example, the network node 1400 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source suppliespower to power circuitry of the power source 1408. As a further example, the power source 1408 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0226] Embodiments of the network node 1400 may include additional components beyond those shown in Figure 14 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node 1400 may include user interface equipment to allow input of information into the network node 1400 and to allow output of information from the network node 1400. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1400.

[0227] Figure 15 is a block diagram of a host 1500, which may be an embodiment of the host 1216 of Figure 12, in accordance with various aspects described herein. As used herein, the host 1500 may be or comprise various combinations hardware and / or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host 1500 may provide one or more services to one or more UEs.

[0228] The host 1500 includes processing circuitry 1502 that is operatively coupled via a bus 1504 to an input / output interface 1506, a network interface 1508, a power source 1510, and a memory 1512. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures 13 and 14, such that the descriptions thereof are generally applicable to the corresponding components of host 1500.

[0229] The memory 1512 may include one or more computer programs including one or more host application programs 1514 and data 1516, which may include user data, e.g., data generated by a UE for the host 1500 or data generated by the host 1500 for a UE. Embodiments of the host 1500 may utilize only a subset or all of the components shown. The host application programs 1514 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). The host application programs 1514 may also provide foruser authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host 1500 may select and / or indicate a different host for over-the-top services for a UE. The host application programs 1514 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc.

[0230] Figure 16 is a block diagram illustrating a virtualization environment 1600 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1600 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 1600 includes components defined by the 0-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface.

[0231] Applications 1602 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment Q400 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0232] Hardware 1604 includes processing circuitry, memory that stores software and / or instructions executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1606 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1608a and 1608b (one or more of which may be generally referred to as VMs 1608), and / or perform any of the functions, features and / or benefits described in relation with someembodiments described herein. The virtualization layer 1606 may present a virtual operating platform that appears like networking hardware to the VMs 1608.

[0233] The VMs 1608 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1606. Different embodiments of the instance of a virtual appliance 1602 may be implemented on one or more of VMs 1608, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0234] In the context of NFV, a VM 1608 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 1608, and that part of hardware 1604 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1608 on top of the hardware 1604 and corresponds to the application 1602.

[0235] Hardware 1604 may be implemented in a standalone network node with generic or specific components. Hardware 1604 may implement some functions via virtualization. Alternatively, hardware 1604 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 1610, which, among others, oversees lifecycle management of applications 1602. In some embodiments, hardware 1604 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1612 which may alternatively be used for communication between hardware nodes and radio units.

[0236] Figure 17 shows a communication diagram of a host 1702 communicating via a network node 1704 with a UE 1706 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as aUE 1212a of Figure 12 and / or UE 1300 of Figure 13), network node (such as networknode 1210a of Figure 12 and / or network node 1400 of Figure 14), and host (such as host 1216 of Figure 12 and / or host 1500 of Figure 15) discussed in the preceding paragraphs will now be described with reference to Figure 17.

[0237] Like host 1500, embodiments of host 1702 include hardware, such as a communication interface, processing circuitry, and memory. The host 1702 also includes software, which is stored in or accessible by the host 1702 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE 1706 connecting via an over-the-top (OTT) connection 1750 extending between the UE 1706 and host 1702. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection 1750.

[0238] The network node 1704 includes hardware enabling it to communicate with the host 1702 and UE 1706. The connection 1760 may be direct or pass through a core network (like core network 1206 of Figure 12) and / or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

[0239] The UE 1706 includes hardware and software, which is stored in or accessible by UE 1706 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non-human user via UE 1706 with the support of the host 1702. In the host 1702, an executing host application may communicate with the executing client application via the OTT connection 1750 terminating at the UE 1706 and host 1702. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection 1750 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection 1750.

[0240] The OTT connection 1750 may extend via a connection 1760 between the host 1702 and the network node 1704 and via a wireless connection 1770 between the network node 1704 and the UE 1706 to provide the connection between the host 1702 and the UE 1706. The connection 1760 and wireless connection 1770, over which the OTT connection 1750 may be provided, have been drawn abstractly to illustrate the communication between the host 1702 and the UE 1706 via the network node 1704, without explicit reference to any intermediary devices and the precise routing of messages via these devices.

[0241] As an example of transmitting data via the OTT connection 1750, in step 1708, the host 1702 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE 1706. In other embodiments, the user data is associated with a UE 1706 that shares data with the host 1702 without explicit human interaction. In step 1710, the host 1702 initiates a transmission carrying the user data towards the UE 1706. The host 1702 may initiate the transmission responsive to a request transmitted by the UE 1706. The request may be caused by human interaction with the UE 1706 or by operation of the client application executing on the UE 1706. The transmission may pass via the network node 1704, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step 1712, the network node 1704 transmits to the UE 1706 the user data that was carried in the transmission that the host 1702 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1714, the UE 1706 receives the user data carried in the transmission, which may be performed by a client application executed on the UE 1706 associated with the host application executed by the host 1702.

[0242] In some examples, the UE 1706 executes a client application which provides user data to the host 1702. The user data may be provided in reaction or response to the data received from the host 1702. Accordingly, in step 1716, the UE 1706 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input / output interface of the UE 1706. Regardless of the specific manner in which the user data was provided, the UE 1706 initiates, in step 1718, transmission of the user data towards the host 1702 via the network node 1704. In step 1720, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 1704 receives user data from the UE 1706 and initiates transmission of the received user data towards the host 1702. In step 1722, the host 1702 receives the user data carried in the transmission initiated by the UE 1706.

[0243] One or more of the various embodiments improve the performance of OTT services provided to the UE 1706 using the OTT connection 1750, in which the wireless connection 1770 forms the last segment. More precisely, the teachings of these embodiments may improve the availability of resources in the network through releasing resources and configurations that are unused or are unlikely to be used, and thereby provide benefits such as better responsiveness, improved content resolution and reduced user waiting time.

[0244] In an example scenario, factory status information may be collected and analyzed by the host 1702. As another example, the host 1702 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host 1702 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host 1702 may store surveillance video uploaded by a UE. As another example, the host 1702 may store or control access to media content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host 1702 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing and / or transmitting data.

[0245] In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1750 between the host 1702 and UE 1706, in response to variations in the measurement results. The measurement procedure and / or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host 1702 and / or UE 1706. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection 1750 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1750 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node 1704. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host 1702. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 1750 while monitoring propagation times, errors, etc.

[0246] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or softwareneeded to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[0247] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

[0248] The following groups of numbered statements set out embodiments of the disclosure.EMBODIMENTSGroup A Embodiments1. A method performed by a user equipment, the method comprising: receiving, from a network node, a message comprising a request for the user equipment to release a configuration for use in connecting to and / or communicatingwith a candidate cell following a lower-layer cell mobility procedure; and responsive to receiving the message, releasing the configuration. The method of embodiment 1, further comprising transmitting, to the network node, a response message confirming release of the configuration. The method of any one of the preceding embodiments, wherein the message comprises an instruction for the user equipment to release the configuration. The method of any one of the preceding embodiments, wherein the configuration comprises information that enables the user equipment to refresh one or more security keys for use in connecting to and / or communicating with the candidate cell. The method of embodiment 4, wherein the information that enables the user equipment to refresh one or more security keys comprises one or more of: an indication of a master key update parameter; an indication of one or more security algorithms to be used by the user equipment to derive one or more user plane keys and / or one or more control plane keys. The method of embodiment 4 or 5, wherein the configuration comprises an indication of one or more source cells, and wherein the user equipment determines whether to refresh the one or more security keys based on whether or not the lower-layer mobility procedure was from one of the one or more source cells. The method of embodiment 6, wherein the indication of one or more source cells comprises one or more of: one or more cell IDs; one or more physical cell identifiers; one or more source cell configuration identifiers; and an identifier of a group of one or more cells. The method of any one of embodiments 4 to 7, wherein the one or more security keys comprise a master key for a network node serving the candidate cell. The method of any one of the preceding embodiments, wherein the configuration further comprises a measurement configuration comprising an instruction for the userequipment to perform measurements on transmissions by the candidate cell. The method of embodiment 9, further comprising transmitting a report message to the network node, comprising an indication of values derived from the measurements on transmissions by the candidate cell. The method of embodiment 9 or 10, wherein the measurement configuration comprises an indication of whether the user equipment is instructed to autonomously estimate timing advance for the candidate cell. The method of any one of the preceding embodiments, wherein the configuration comprises an indication to perform lower-layer re-establishment for one or more radio bearers upon connection to the candidate cell, e.g., PDCP re-establishment. The method of any one of the preceding embodiments, wherein the configuration comprises one of: a full configuration; and a delta configuration defining one or more differences relative to a reference configuration. The method of any one of the preceding embodiments, wherein the configuration comprises one of: a configuration for a connection to a standalone network node; a configuration for a connection to a master-cell group network node; and a configuration for a connection to a secondary-cell group network node. The method of any one of the preceding embodiments, wherein the network node comprises a first centralized unit, CU, or a first base station, and wherein the candidate cell is served by a second CU or a second base station. The method of any one of the preceding embodiments, wherein the network node is a serving network node for the user equipment. The method of any one of the preceding embodiments, wherein the message comprises an RRCReconfiguration message. The method of any one of the preceding embodiments, wherein the lower-layer cell mobility procedure is triggered upon receipt of, via lower-layer signalling from asource network node, a command to switch to the candidate cell. The method of embodiment 18, wherein the command comprises an indication that the candidate cell is served by a different CU or a different base station than the source network node. The method of any one of embodiments 18 to 19, wherein the lower-layer signalling comprises one or more of: LI and L2 signalling. The method of any one of embodiments 18 to 20, wherein the lower-layer signalling comprises one or more of: Medium Access Control, MAC, signalling and Physical, PHY, layer signalling. The method according to any one of the preceding embodiments, wherein the lower- layer cell mobility procedure comprises an L1 / L2 triggered mobility, LTM, procedure. The method according to any one of the preceding embodiments, wherein the message comprises a request to release more than one configuration. The method according to any one of the preceding embodiments, wherein the configuration comprises an inter-CU LTM configuration. The method according to any one of the preceding embodiments, wherein the message is received responsive to one or more of: the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cell are above or below a threshold; the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE re-establishing a connection in a second network node that does not serve the candidate cell; the UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage or has become reachable again; the user equipment transmitting, to a network node, measurement report (e.g., RRC Measurement Report) including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRCReconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message.26. The method of any of the previous embodiments, further comprising: providing user data; and forwarding the user data to a host via the transmission to the network node.Group B Embodiments27. A method performed by a first network node, the method comprising: transmitting, to one or more of a user equipment, UE, and a second network node, a message comprising a request for the one or more of the UE and the second network node to release a configuration for use in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure by the UE to the candidate cell.28. The method of embodiment 27, wherein the message comprises an instruction for the one of the user equipment and the second network node to release the configuration.29. The method of embodiment 27 or 28, wherein the message is transmitted to the UE.30. The method of embodiment 29, further comprising receiving, from the UE, a response message confirming release of the configuration.31. The method of embodiment 29 or 30, wherein the message comprises an RRCReconfiguration message.32. The method of embodiment 27 or 28, wherein the message is transmitted to the second network node.33. The method of embodiment 32, further comprising refraining to monitor for a response message from the second network node confirming release of theconfiguration. The method of embodiment 32, further comprising receiving, from the second network node, a response message confirming release of the configuration. The method of any one of embodiments 32 to 34, wherein the message comprises a HANDOVER CANCEL message. The method of any one of embodiments 27 to 35, wherein the message comprises an indication of a cause for release of the configuration. The method according to any one of embodiments 27 to 36, wherein the message is transmitted responsive to one or more of: the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cell are above or below a threshold; the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE reestablishing a connection in a second network node that does not serve the candidate cell; the UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage or has become reachable again; the user equipment transmitting, to a network node, measurement report (e.g., RRC Measurement Report) including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message. A method performed by a second network node, the method comprising: receiving, from a first network node, a message comprising a request for the second network node to release a configuration for use by a user equipment, UE, in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure; and responsive to receiving the message, releasing the configuration.The method of embodiment 38, further comprising transmitting, to the first network node, a response message confirming release of the configuration. The method of embodiment 38, further comprising refraining from transmitting, to the first network node, a response message confirming release of the configuration. The method of any one of embodiments 38 to 40, wherein the message comprises a HANDOVER CANCEL message. The method according to any one of embodiments 38 to 41, wherein the message is received responsive to one or more of: the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cell are above or below a threshold; the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE re-establishing a connection in a second network node that does not serve the candidate cell; the UE is unreachable e.g. has triggered a Radio Link Failure and / or is out of coverage or has become reachable again; the user equipment transmitting, to a network node, measurement report (e.g., RRC Measurement Report) including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message. The method of any one of embodiments 27 to 42, wherein the configuration comprises information that enables the user equipment to refresh one or more security keys for use in connecting to and / or communicating with the candidate cell. The method of embodiment 43, wherein the information that enables the user equipment to refresh one or more security keys comprises one or more of: an indication of a master key update parameter; an indication of one or more securityalgorithms to be used by the user equipment to derive one or more user plane keys and / or one or more control plane keys. The method of embodiment 42 or 43, wherein the configuration comprises an indication of one or more source cells, and wherein the user equipment determines whether to refresh the one or more security keys based on whether or not the lower- layer mobility procedure was from one of the one or more source cells. The method of embodiment 45, wherein the indication of one or more source cells comprises one or more of: one or more cell IDs; one or more physical cell identifiers; one or more source cell configuration identifiers; and an identifier of a group of one or more cells. The method of any one of embodiments 43 to 46, wherein the one or more security keys comprise a master key for a network node serving the candidate cell. The method of any one of embodiments 27 to 47, wherein the configuration further comprises a measurement configuration comprising an instruction for the user equipment to perform measurements on transmissions by the candidate cell. The method of embodiment 48, wherein the measurement configuration comprises an indication of whether the user equipment is instructed to autonomously estimate timing advance for the candidate cell. The method of any one of embodiments 27 to 49, wherein the configuration comprises an indication to perform lower-layer re-establishment for one or more radio bearers upon connection to the candidate cell, e.g., PDCP re-establishment. The method of any one of embodiments 27 to 50, wherein the configuration comprises one of: a full configuration; and a delta configuration defining one or more differences relative to a reference configuration. The method of any one of embodiments 27 to 51, wherein the configuration comprises one of: a configuration for a connection to a standalone network node; a configuration for a connection to a master-cell group network node; and aconfiguration for a connection to a secondary-cell group network node. The method of any one of embodiments 27 to 52, wherein the first network node comprises a first centralized unit, CU, or a first base station, and wherein the second network node comprises a second CU or a second base station. The method of any one of embodiments 27 to 53, wherein the first network node is a serving network node for the user equipment. The method of any one of embodiments 27 to 54, wherein the lower-layer cell mobility procedure is triggered upon receipt of, via lower-layer signalling from a source network node, a command to switch to the candidate cell. The method of embodiment 55, wherein the command comprises an indication that the candidate cell is served by a different CU or a different base station than the source network node. The method of embodiment 55 or 56, wherein the lower-layer signalling comprises one or more of: LI and L2 signalling. The method of any one of embodiments 55 to 57, wherein the lower-layer signalling comprises one or more of: Medium Access Control, MAC, signalling and Physical, PHY, layer signalling. The method according to any one of embodiments 27 to 58, wherein the lower-layer cell mobility procedure comprises an L1 / L2 triggered mobility, LTM, procedure. The method according to any one of embodiments 27 to 59, wherein the message comprises a request to release more than one configuration. The method according to any one of embodiments 27 to 60, wherein the configuration comprises an inter-CU LTM configuration. The method of any of the previous embodiments, further comprising:obtaining user data; and forwarding the user data to a host or a user equipment.Group C Embodiments63. A user equipment, comprising: processing circuitry configured to cause the user equipment to perform any of the steps of any of the Group A embodiments; and power supply circuitry configured to supply power to the processing circuitry.64. A network node, the network node comprising: processing circuitry configured to cause the network node to perform any of the steps of any of the Group B embodiments; power supply circuitry configured to supply power to the processing circuitry.65. A user equipment (UE), the UE comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of the Group A embodiments; an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processed by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE.66. A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; anda network interface configured to initiate transmission of the user data to a network node in a cellular network for transmission to a user equipment (UE), the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE.67. The host of the previous embodiment, wherein: the processing circuitry of the host is configured to execute a host application that provides the user data; and the UE comprises processing circuitry configured to execute a client application associated with the host application to receive the transmission of user data from the host.68. A method implemented in a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular network comprising the network node, wherein the network node performs any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE.69. The method of the previous embodiment, further comprising, at the network node, transmitting the user data provided by the host for the UE.70. The method of any of the previous 2 embodiments, wherein the user data is provided at the host by executing a host application that interacts with a client application executing on the UE, the client application being associated with the host application.71. A communication system configured to provide an over-the-top (OTT) service, the communication system comprising: a host comprising: processing circuitry configured to provide user data for a user equipment (UE), the userdata being associated with the over-the-top service; and a network interface configured to initiate transmission of the user data toward a cellular network node for transmission to the UE, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE.72. The communication system of the previous embodiment, further comprising: the network node; and / or the UE.73. A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to initiate receipt of user data; and a network interface configured to receive the user data from a network node in a cellular network, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to receive the user data from a user equipment (UE) for the host.74. The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application that receives the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.75. The host of the any of the previous 2 embodiments, wherein the initiating receipt of the user data comprises requesting the user data.76. A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising:at the host, initiating receipt of user data from the UE, the user data originating from a transmission which the network node has received from the UE, wherein the network node performs any of the steps of any of the Group B embodiments to receive the user data from the UE for the host.77. The method of the previous embodiment, further comprising at the network node, transmitting the received user data to the host.78. A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the operations of any of the Group A embodiments to receive the user data from the host.79. The host of the previous embodiment, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data to the UE from the host.80. The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.81. A method implemented by a host operating in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular networkcomprising the network node, wherein the UE performs any of the operations of any of the Group A embodiments to receive the user data from the host.82. The method of the previous embodiment, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the host application.83. The method of the previous embodiment, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application.84. A host configured to operate in a communication system to provide an over-the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the steps of any of the Group A embodiments to transmit the user data to the host.85. The host of the previous embodiment, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data from the UE to the host.86. The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.87. A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: at the host, receiving user data transmitted to the host via the network node by the UE, wherein the UE performs any of the steps of any of the Group A embodiments to transmit the user data to the host.88. The method of the previous embodiment, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the UE.89. The method of the previous 2 embodiments, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application.

Claims

CLAIMS1. A method performed by a first network node (1400), the method comprising: transmitting (402), to one or more of a user equipment, UE, (1300) and a second network node (1400), a message comprising a request for the one or more of the UE and the second network node to release an inter-central-unit, CU, L1 / L2 triggered mobility procedure, LTM, configuration for use in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure by the UE to the candidate cell.

2. The method of claim 1, wherein the message comprises an instruction for the one of the user equipment and the second network node to release the inter-CU LTM configuration.

3. The method of claim 1 or 2, wherein the message is transmitted to the UE.

4. The method of claim 3, further comprising receiving, from the UE, a response message confirming release of the inter-CU LTM configuration.

5. The method of claim 1 or 2, wherein the message is transmitted to the second network node.

6. The method of claim 5, further comprising refraining to monitor for a response message from the second network node confirming release of the inter-CU LTM configuration or receiving, from the second network node, a response message confirming release of the inter-CU LTM configuration.

7. The method of any one of claims 1 to 6, wherein the message comprises an indication of a cause for release of the inter-CU LTM configuration.

8. The method according to any one of claims 1 to 7, wherein the message is transmitted responsive to one or more of: the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cellare above or below a threshold; the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE re-establishing a connection in a second network node that does not serve the candidate cell; the UE is unreachable or has become reachable again; the user equipment transmitting, to a network node, a measurement report including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message.

9. A method performed by a second network node (1400), the method comprising: receiving (502), from a first network node (1400), a message comprising a request for the second network node to release an inter-CU LTM configuration for use by a user equipment, UE, (1300) in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure; and responsive to receiving the message, releasing (504) the inter-CU LTM configuration.

10. The method of claim 9, further comprising transmitting, to the first network node, a response message confirming release of the inter-CU LTM configuration or refraining from transmitting, to the first network node, a response message confirming release of the inter-CU LTM configuration.

11. The method according to any one of claims 9 to 10, wherein the message is received responsive to one or more of: the user equipment transmitting, to a network node, a measurement report indicating that radio measurements associated with a certain cell are above or below a threshold; the UE successfully performing LTM towards a network node; the UE receiving, from a network node, an LTM Cell switch command; the UE being about to enter an idle or inactive state; the UE re-establishinga connection in a second network node that does not serve the candidate cell; the UE is unreachable or has become reachable again; the user equipment transmitting, to a network node, measurement report including one or more measurements of one or more cells; the user equipment transmitting, to a network node, an RRC Reconfiguration Complete message in response to an RRC Reconfiguration message which indicated the release of one or more LTM candidate cell(s); the UE entering a connected state; and the UE transmitting an RLF -related RRC message, such as an SCG failure information message, a failure information message, or a MCG failure information message.

12. The method of any one of the preceding claims, wherein the inter-CU LTM configuration comprises information that enables the user equipment to refresh one or more security keys for use in connecting to and / or communicating with the candidate cell.

13. The method of claim 12, wherein the inter-CU LTM configuration comprises an indication of one or more source cells, and wherein the user equipment determines whether to refresh the one or more security keys based on whether or not the lower- layer mobility procedure was from one of the one or more source cells.

14. The method of any one of the preceding claims, wherein the inter-CU LTM configuration further comprises a measurement configuration comprising an instruction for the user equipment to perform measurements on transmissions by the candidate cell.

15. The method of any one of the preceding claims, wherein the inter-CU LTM configuration comprises an indication to perform lower-layer re-establishment for one or more radio bearers upon connection to the candidate cell.

16. The method of any one of the preceding claims, wherein the first network node comprises a first central unit, CU, or a first base station, and wherein the second network node comprises a second CU or a second base station.

17. The method of any one of claims 9 to 16, wherein the lower-layer cell mobility procedure is triggered upon receipt of, via lower-layer signalling from a source network node, a command to switch to the candidate cell.

18. A method performed by a user equipment (1300), the method comprising: receiving (302), from a network node (1400), a message comprising a request for the user equipment to release an inter-CU LTM configuration for use in connecting to and / or communicating with a candidate cell following a lower-layer cell mobility procedure; and responsive to receiving the message, releasing (304) the inter-CU LTM configuration.

19. The method of claim 18, further comprising transmitting, to the network node, a response message confirming release of the inter-CU LTM configuration.

20. The method of any of claims 18 or 19, wherein the message comprises an instruction for the user equipment to release the inter-CU LTM configuration.

21. The method of any of claims 18 to 20, wherein the inter-CU LTM configuration comprises information that enables the user equipment to refresh one or more security keys for use in connecting to and / or communicating with the candidate cell.

22. The method of claim 21, wherein the inter-CU LTM configuration comprises an indication of one or more source cells, and wherein the user equipment determines whether to refresh the one or more security keys based on whether or not the lower- layer mobility procedure was from one of the one or more source cells.

23. The method of any of claims 18 to 22, wherein the inter-CU LTM configuration further comprises a measurement configuration comprising an instruction for the user equipment to perform measurements on transmissions by the candidate cell.

24. The method of claim 23, further comprising transmitting a report message to the network node, comprising an indication of values derived from the measurements on transmissions by the candidate cell.

25. The method of claim 23 or 24, wherein the measurement configuration comprises an indication of whether the user equipment is instructed to autonomously estimate timing advance for the candidate cell.

26. The method of any of claims 18 to 25, wherein the inter-CU LTM configuration comprises an indication to perform lower-layer re-establishment for one or more radio bearers upon connection to the candidate cell.

27. The method of any of claims 18 to 26, wherein the network node comprises a first central unit, CU, or a first base station, and wherein the candidate cell is served by a second CU or a second base station.

28. The method of any of claims 18 to 27, wherein the lower-layer cell mobility procedure is triggered upon receipt of, via lower-layer signalling from a source network node, a command to switch to the candidate cell.

29. The method of claim 28, wherein the command comprises an indication that the candidate cell is served by a different CU or a different base station than the source network node.

30. A first network node (1400) comprising processing circuitry (1402) configured to cause the first network node to: transmit (402), to one or more of a user equipment, UE, (1300) and a second network node (1400), a message comprising a request for the one or more of the UE and the second network node to release an inter-CU LTM configuration for use in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure by the UE to the candidate cell.

31. The first network node of claim 30, the processing circuitry further configured to cause the first network node to perform the method of any of claims 2-8.

32. A first network node (1400) configured to perform the method of any of claims 1-8.

33. A second network node (1400) comprising processing circuitry (1402) configured to cause the second network node to: receive (502), from a first network node (1400), a message comprising a request for the second network node to release an inter-CU LTM configuration for use by a user equipment, UE, (1300) in connecting to and / or communicating with a candidate cell served by the second network node following a lower-layer cell mobility procedure; and responsive to receiving the message, release (504) the inter-CU LTM configuration.

34. The second network node of claim 33, the processing circuitry further configured to cause the second network node to perform the method of any of claims 10-17.

35. A second network node (1400) configured to perform the method of any of claims 9- 17.

36. A user equipment (1300) comprising processing circuitry (1302) configured to cause the user equipment to: receive (302), from a network node, a message comprising a request for the user equipment to release an inter-CU LTM configuration for use in connecting to and / or communicating with a candidate cell following a lower-layer cell mobility procedure; and responsive to receiving the message, release (304) the inter-CU LTM configuration37. The user equipment of claim 36, the processing circuitry further configured to cause the user equipment to perform the method of any of claims 19-29.

38. A user equipment (1300) configured to perform the method of any of claims 18-29.

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