Execution conditions for conditional ltm

Abstract

Methods, apparatus, and systems for supporting conditional L1 / L2-triggered mobility, LTM, in a wireless network An example method, carried out by a user equipment, UE, comprises the steps of receiving (1210), from the wireless network, conditional LTM configuration information comprising first and second conditional LTM execution conditions, associated to respective first and second LTM candidate cell configurations, and executing a first LTM cell switch procedure to a first candidate cell, according to the first LTM candidate cell configuration, in response to fulfilment of the first conditional LTM execution condition. The example method further comprises evaluating (1240) the second conditional LTM execution condition, responsive to executing the first LTM cell switch procedure to the first candidate cell, to determine whether to perform a second LTM cell switch procedure to a second candidate cell, corresponding to the second LTM candidate cell configuration.

Description

[0001] EXECUTION CONDITIONS FOR CONDITIONAL LTM

[0002] TECHNICAL FIELD

[0003] The present application relates generally to the field of wireless networks, and more specifically to mobility of user equipment (UEs) across multiple cells in a wireless network, specifically mobility based on layer-1 (LI) and / or layer-2 (L2) procedures, commonly referred to as Layer- l / Layer-2 Triggered Mobility, or LTM.

[0004] BACKGROUND

[0005] Currently the fifth generation (“5G”) of cellular systems, also referred to as New Radio (NR), is being standardized within the Third-Generation Partnership Project (3GPP). NR is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultrareliable low latency communications (URLLC), side-link device-to-device (D2D), and several other use cases.

[0006] Figure 1 illustrates a high-level view of the 5G network architecture, consisting of a Next Generation RAN (NG-RAN) 199 and a 5G Core (5GC) 198. NG-RAN 199 can include one or more gNodeB’s (gNBs) connected to the 5GC via one or more NG interfaces, such as gNBs 100, 150 connected via interfaces 102, 152, respectively. More specifically, gNBs 100, 150 can be connected to one or more Access and Mobility Management Functions (AMFs) in the 5GC 198 via respective NG-C interfaces. Similarly, gNBs 100, 150 can be connected to one or more User Plane Functions (UPFs) in 5GC 198 via respective NG-U interfaces. 5GC 198 can include various other network functions (NFs), such as Session Management Function(s) (SMF).

[0007] Although not shown, in some deployments 5GC 198 can be replaced by an Evolved Packet Core (EPC), which conventionally has been used together with a Long-Term Evolution (LTE) Evolved UMTS RAN (E-UTRAN). In such deployments, gNBs 100, 150 can connect to one or more Mobility Management Entities (MMEs) in EPC 198 via respective Sl-C interfaces. Similarly, gNBs 100, 150 can connect to one or more serving Gateways (SGWs) in EPC via respective NG-U interfaces.

[0008] The gNBs can be connected to each other via one or more Xn interfaces, such as Xn interface 140 between gNBs 100 and 150. The radio technology for the NG-RAN is often referred to as “New Radio” (NR). With respect to the NR interface to UEs, each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. NG-RAN 199 is layered into a Radio Network Layer (RNL) and a Transport Network Layer (TNL). The NG-RAN architecture, / .< ., the NG-RAN logical nodes and interfaces between them, is defined as part of the RNL. For each NG-RAN interface (NG, Xn, Fl) the related TNL protocol and the functionality are specified. The TNL provides services for user plane transport and signaling transport.

[0009] The NG RAN logical nodes shown in Figure 1 include a Central Unit (CU or gNB-CU) and one or more Distributed Units (DU or gNB-DU). For example, gNB 100 includes gNB-CU 110 and gNB-DUs 120 and 130. CUs are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs, which are logical nodes that host lower layer protocols and can include various subsets of the gNB functions. As such, each of the CUs and DUs can include various circuitry needed to perform their respective functions, including processing circuitry, communication interface circuitry (e.g., transceivers), and power supply circuitry.

[0010] A gNB-CU connects to one or more gNB-DUs over respective Fl logical interfaces, such as interfaces 122 and 132 shown in Figure 1. A gNB-DU may be connected to multiple gNB-CUs by appropriate implementation. The gNB-CU and connected gNB-DU(s) are only visible to other gNBs and the 5GC as a gNB. In other words, the Fl interface is not visible beyond gNB- CU.

[0011] Dual connectivity (DC) was introduced in LTE Rel-12. In DC operation, a UE in

[0012] RRC CONNECTED state consumes radio resources provided by at least two different network nodes connected to one another with a non-ideal backhaul. Several DC (or more generally, multi -connectivity) arrangements are also supported in 5G / NR. These include NR-DC that is like LTE DC except that both network nodes use the NR interface to communicate with the UE, as well as various multi-RAT DC (MR-DC) involving both LTE and NR access by the same UE. More generally, one node acts as a master node (MN) providing the UE’s master cell group (MCG) and another node acts as a secondary node (SN) providing the UE’s secondary cell group (SCG), with at least the MN being connected to a core network (e.g., EPC or 5GC).

[0013] Each of the CGs includes one MAC entity, a primary cell (PCell), and optionally one or more secondary cells (SCells). The term “Special Cell” (or “SpCell” for short) refers to the PCell of the MCG or the PCell of the SCG (also referred to as “PSCell”) depending on whether the UE’s MAC entity is associated with the MCG or the SCG, respectively. In non-DC operation (e.g., carrier aggregation, CA), SpCell refers to the PCell. An SpCell is always activated and supports physical UL control channel (PUCCH) transmission and contention-based random access by UEs.

[0014] When the UE moves between the coverage areas of two cells, a serving cell change needs to be performed at some point. Currently, serving cell change is triggered by layer 3 (L3, e.g., RRC) measurements and involves RRC signaling to change PCell and / or PSCell (e.g., when dual connectivity is configured), as well as release / add SCells (e.g., when CA is configured). For example, a handover command is sent by an RRCReconfiguration message that includes a reconfigurationWithSync information element (IE).

[0015] Currently, L3 inter-cell mobility involves complete layer 2 (L2) and layer 1 (LI, i.e., PHY) resets, leading to longer latency, increased signaling overhead, and longer interruptions than for intra-cell beam switching. To address these issues, NR Rel-18 included a Work Item on NR mobility enhancements, which includes a feature referred to as L1 / L2 based inter-cell mobility, L1 / L2 triggered mobility (LTM), or lower layer-triggered mobility. This work item is further described in 3GPP document RP-213565. A goal of Rel-18 L1 / L2 mobility (or LTM) enhancements is to facilitate serving cell change via L1 / L2 signaling to reduce latency, signaling overhead, and interruptions associated with conventional L3 inter-cell mobility.

[0016] A basic principle of LTM is that the UE is pre-configured, by the network, with one RRC configuration per LTM candidate target cell. This pre-configured RRC configuration is sometimes referred to as an LTM candidate cell configuration. Such an LTM candidate cell configuration may be an RRCReconfiguration message or one or more IEs / fields / parameters such as CellGroupConfig.

[0017] After receiving these LTM candidate cell configurations, the UE performs measurements on these LTM candidate cells and transmits corresponding measurement reports to the network. The network then triggers the execution of a LTM cell switch in the UE to one of these LTM candidate cells by transmitting an LTM cell switch command (such as a MAC CE), to the UE, which then connects to the particular LTM candidate cell and switches to an RRC configuration of this LTM candidate cell.

[0018] Thus, LTM is a procedure in which a gNB receives LI measurement report(s) from a UE, and on their basis the gNB changes UE serving cell by a cell switch command signalled via a Medium Access Control (MAC) Control element (CE). The cell switch command indicates an LTM candidate configuration that the gNB previously prepared and provided to the UE through RRC signalling. Then the UE switches to the target configuration according to the cell switch command [1],

[0019] According to the 3 GPP specifications, LTM supports both intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. LTM supports both intra-frequency and inter-frequency mobility, including mobility to inter-frequency cell that is not a current serving cell. Cell switch command is conveyed in a MAC CE, which contains the necessary information to perform the LTM cell switch.

[0020] Figure 2 illustrates an example signaling flow for configuring a UE with LTM, according to Rel- 18 of the 3 GPP standards.

[0021] Since Rel-18, a feature referred to as “Subsequent LTM” is supported, whereby the UE may be triggered to perform multiple LTM cell switch procedures between candidate cells without RRC reconfiguration by the network in between. Subsequent LTM is done by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion.

[0022] As discussed above, LTM was introduced in Rel-18 of the 3GPP specifications and can offer improvements in handover latency and interruption time compared to Layer 3 based mobility. However, LTM as introduced in Rel-18 also has a number of limitations compared to Layer 3 mobility. The Rel-19 work item aims to remove a number of these limitations. Layer 3 mobility has evolved over several releases. Conditional handover (CHO) and other conditional mobility procedures (CP AC, SCPAC) were developed to achieve high robustness by enabling the procedure to be executed without necessitating a signalling exchange with source cell beforehand. LTM as introduced in Rel-18 offers short interruption times but not the same level of robustness as the conditional L3 mobility procedures. In Rel-19, enhancements should be specified so that the system can benefit from both the high robustness and short interruption.

[0023] Regarding conditional LTM, the following objectives have been captured in [2]:

[0024] • Specify support of conditional LTM [RAN2, RAN3, RANI]

[0025] • Specify UE evaluated conditions for triggering LTM

[0026] • Aim to support conditional LTM including subsequent LTM

[0027] Further improvements to Ll / L2-triggered mobility, or LTM, are needed. SUMMARY

[0028] Specific problems arise when considering the specification of procedures for subsequent conditional LTM, i.e., conditional LTM that is triggered after an LTM procedure. For the case of subsequent conditional LTM it is however also not clear how the UE can evaluate the different conditional LTM candidate configurations using execution conditions that are relevant for the current serving cell, i.e. using different execution conditions for the same LTM candidate configuration depending on which cell the UE is currently located in.

[0029] Embodiments described herein address these problems.

[0030] An example method carried out by a UE comprises the step of receiving, from the wireless network, conditional LTM configuration information comprising a first conditional LTM execution condition, associated to a first LTM candidate cell configuration, and a second conditional LTM execution condition, associated to a second LTM candidate cell configuration. The method further comprises executing a first LTM cell switch procedure to a first candidate cell, according to the first LTM candidate cell configuration, in response to fulfilment of the first conditional LTM execution condition. Note that this implies an evaluation of the first conditional LTM execution condition and a determination that it has been fulfilled. The method still further comprises, in response to executing the first LTM cell switch procedure to the first candidate cell, evaluating the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a second candidate cell, corresponding to the second LTM candidate cell configuration.

[0031] Another example method is carried out by a first network node, which controls a cell, such as a DU or gNB. This method comprises the step of receiving, from a second network node, a request to configure a first cell, controlled by the first network node, as a first conditional LTM candidate cell, the request comprising an indication of a second conditional LTM candidate cell. The method further includes sending a message to the second network node, in response to the request, the message including a lower layer configuration for the first conditional LTM candidate cell and further including a conditional LTM execution condition associated to the second conditional LTM candidate cell, for use by a UE after performing a conditional LTM cell switch procedure to the first conditional LTM candidate cell.

[0032] Variations of these methods and corresponding apparatuses and systems are described in detail below. Other objects, features, and advantages of the present disclosure will become apparent upon reading the following detailed description in view of the drawings briefly described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 illustrates a high-level view of an exemplary 5G / NR network architecture.

[0034] Figure 2 is a signaling flow diagram illustrating configuration of a UE with LTM.

[0035] Figure 3 is another high-level view of an exemplary 5G / NR network architecture

[0036] Figure 4 shows an exemplary configuration of NR user plane (UP) and control plane (CP) protocol stacks.

[0037] Figure 5 is a message sequence chart illustrating signaling for LTM in an inter-DU scenario.

[0038] Figure 6 is a signaling flow diagram focused on UE steps for subsequent conditional LTM when the UE is configured with the first and the second LTM candidate cells for conditional LTM and, while connected to a S-DU, the UE executes LTM cell switch to the first cell.

[0039] Figure 7 is a signaling flow focused on the C-DU steps for subsequent conditional LTM when the UE is configured with the first and the second LTM candidate cells for conditional LTM, for configuring conditional LTM execution conditions for when the UE switches to the C-DU, in subsequent LTM.

[0040] Figure 8 illustrates a signaling flow focused on the UE steps when the UE is configured with execution conditions for the first and the second cells, evaluated while the UE is connected to the S-DU, and the UE executes an LTM cell switch to the first cell.

[0041] Figure 9 illustrates an example configuration of a fourth conditional LTM execution condition within a first LTM candidate cell configuration and a third conditional LTM execution condition within the second LTM candidate cell configuration.

[0042] Figure 10 illustrates an example of how a measurement configuration identifier is used to refer to a conditional LTM execution condition for subsequent LTM.

[0043] Figure 11 A and Figure 1 IB illustrate an example signaling flow - inter-gNB-DU (intra-CU) - for the configuration of conditional LTM execution conditions.

[0044] Figure 12 shows an exemplary method (e.g., procedure) for a UE, according to various embodiments of the present disclosure.

[0045] Figure 13 shows an exemplary method (e.g., procedure) for a network node, according to various embodiments of the present disclosure. Figure 14 shows a communication system according to various embodiments of the present disclosure.

[0046] Figure 15 shows a UE according to various embodiments of the present disclosure.

[0047] Figure 16 shows a network node according to various embodiments of the present disclosure.

[0048] Figure 17 is a block diagram of a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized.

[0049] DETAILED DESCRIPTION

[0050] Embodiments briefly summarized above will now be described more fully with reference to the accompanying drawings. These descriptions are provided by way of example to explain the subject matter to those skilled in the art and should not be construed as limiting the scope of the subject matter to only the embodiments described herein. More specifically, examples are provided below that illustrate the operation of various embodiments according to the advantages discussed above.

[0051] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods and / or procedures disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and / or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein can be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments can apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.

[0052] Furthermore, the following terms are used throughout the description given below:

[0053] • Radio Access Node: As used herein, a “radio access node” (or equivalently “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) that operates to wirelessly transmit and / or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., gNB in a 3 GPP 5G / NR network or an enhanced or eNB in a 3GPP LTE network), base station distributed components (e.g., CU and DU), a high-power or macro base station, a low-power base station (e.g., micro, pico, femto, or home base station, or the like), an integrated access backhaul (IAB) node, a transmission point (TP), a transmission reception point (TRP), a remote radio unit (RRU or RRH), and a relay node.

[0054] • Core Network Node: As used herein, a “core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a serving gateway (SGW), a PDN Gateway (P-GW), a Policy and Charging Rules Function (PCRF), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), a Charging Function (CHF), a Policy Control Function (PCF), an Authentication Server Function (AUSF), a location management function (LMF), or the like.

[0055] • Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device that is capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other wireless devices. Communicating wirelessly can involve transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information through air. Unless otherwise noted, the term “wireless device” is used interchangeably herein with the term “user equipment” (or “UE” for short), with both of these terms having a different meaning than the term “network node”.

[0056] • Radio Node: As used herein, a “radio node” can be either a “radio access node” (or equivalent term) or a “wireless device.”

[0057] • Network Node: As used herein, a “network node” is any node that is either part of the radio access network (e.g., a radio access node or equivalent term) or of the core network (e.g., a core network node discussed above) of a cellular communications network. Functionally, a network node is equipment capable, configured, arranged, and / or operable to communicate directly or indirectly with a wireless device and / or with other network nodes or equipment in the cellular communications network, to enable and / or provide wireless access to the wireless device, and / or to perform other functions (e.g., administration) in the cellular communications network.

[0058] • Base station: As used herein, a “base station” may comprise a physical or a logical node transmitting or controlling the transmission of radio signals, e.g., eNB, gNB, ng-eNB, en- gNB, centralized unit (CU) / distributed unit (DU), transmitting radio network node, transmission point (TP), transmission reception point (TRP), remote radio head (RRH), remote radio unit (RRU), Distributed Antenna System (DAS), relay, etc. • Node: As used herein, the term “node” (without prefix) can be any type of node that can in or with a wireless network (including RAN and / or core network), including a radio access node (or equivalent term), core network node, or wireless device. However, the term “node” may be limited to a particular type (e.g., radio access node) based on its specific characteristics in any given context.

[0059] Note that the description given herein focuses on a 3 GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is generally used. However, the concepts disclosed herein are not limited to a 3GPP system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from the concepts, principles, and / or embodiments described herein.

[0060] To provide additional context for the techniques described in detail below, Figure 3 shows a high-level view of an exemplary 5G network architecture, including an NG-RAN 399 and a 5GC 398. As shown in the figure, NG-RAN 399 can include gNBs (e.g., 310a,b) and ng-eNBs (e.g., 320a, b) that are interconnected with each other via respective Xn interfaces. The gNBs and ng-eNBs are also connected via the NG interfaces to the 5GC, more specifically to the access and mobility management functions (AMFs, e.g., 330a, b) via respective NG-C interfaces and to user plane functions (UPFs, e.g., 340a, b) via respective NG-U interfaces. Moreover, the AMFs can communicate with one or more policy control functions (PCFs, e.g., 350a, b) and network exposure functions (NEFs, e.g., 360a,b).

[0061] Each of the gNBs can support the NR radio interface including frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of ng-eNBs can support the LTE radio interface. Unlike conventional LTE eNBs, however, ng-eNBs 320 connect to the 5GC via the NG interface. Each of the gNBs and ng-eNBs can serve a geographic coverage area including one more cells, such as cells 31 la-b and 321a-b shown in Figure 3. Depending on the cell in which it is located, a UE 305 can communicate with the gNB or ng-eNB serving that cell via the NR or LTE radio interface, respectively. Although Figure 3 shows gNBs and ng-eNBs separately, it is also possible that a single NG-RAN node provides both types of functionality.

[0062] Figure 4 shows an exemplary configuration of NR user plane (UP) and control plane (CP) protocol stacks between a UE 410, a gNB 420, and an AMF 430, such as those shown in Figures 1-2. The Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP) layers between the UE and the gNB are common to UP and CP. The PDCP layer provides ciphering / deciphering, integrity protection, sequence numbering, reordering, and duplicate detection for both CP and UP. In addition, PDCP provides header compression and retransmission for UP data.

[0063] On the UP side, Internet protocol (IP) packets arrive to the PDCP layer as service data units (SDUs), and PDCP creates protocol data units (PDUs) to deliver to RLC. The Service Data Adaptation Protocol (SDAP) layer handles quality -of-service (QoS) including mapping between QoS flows and Data Radio Bearers (DRBs) and marking QoS flow identifiers (QFI) in UU and DL packets. The RLC layer transfers PDCP PDUs to the MAC through logical channels (LCH). RLC provides error detection / correction, concatenation, segmentation / reassembly, sequence numbering, reordering of data transferred to / from the upper layers. The MAC layer provides mapping between LCHs and PHY transport channels, LCH prioritization, multiplexing into or demultiplexing from transport blocks (TBs), hybrid ARQ (HARQ) error correction, and dynamic scheduling (on gNB side). The PHY layer provides transport channel services to the MAC layer and handles transfer over the NR radio interface, e.g., via modulation, coding, antenna mapping, and beam forming.

[0064] On the CP side, the non-access stratum (NAS) layer is between UE and AMF and handles UE / gNB authentication, mobility management, and security control. The RRC layer sits below NAS in the UE but terminates in the gNB rather than the AMF. RRC controls communications between UE and gNB at the radio interface as well as the mobility of a UE between cells in the NG-RAN. RRC also broadcasts system information (SI) and performs establishment, configuration, maintenance, and release of DRBs and Signaling Radio Bearers (SRBs) and used by UEs. Additionally, RRC controls addition, modification, and release of carrier aggregation (CA) and dual -connectivity (DC) configurations for UEs. RRC also performs various security functions such as key management.

[0065] After a UE is powered ON it will be in the RRC IDLE state until an RRC connection is established with the network, at which time the UE will transition to RRC CONNECTED state (e.g., where data transfer can occur). The UE returns to RRC IDLE after the connection with the network is released. In RRC IDLE state, the UE’s radio is active on a discontinuous reception (DRX) schedule configured by upper layers. During DRX active periods (also referred to as “DRX On durations”), an RRC IDLE UE receives SI broadcast in the cell where the UE is camping, performs measurements of neighbor cells to support cell reselection, and monitors a paging channel on PDCCH for pages from 5GC via gNB. An NR UE in RRC IDLE state is not known to the gNB serving the cell where the UE is camping. However, NR RRC includes an RRC_INACTIVE state in which a UE is known (e.g., via UE context) by the serving gNB. RRC INACTIVE has some properties similar to a “suspended” condition used in LTE.

[0066] Seamless mobility is a key feature of 3GPP radio access technologies (RATs). In general, a network configures a UE to perform and report RRM measurements to assist network-controlled mobility decisions, such as for handover from a serving cell to a neighbor cell while the UE is in RRC CONNECTED state. Seamless handovers ensure that the UE moves around in the coverage area of different cells without causing too many interruptions in data transmission.

[0067] The network can configure a UE in RRC CONNECTED state to perform and report RRM measurements that assist network-controlled mobility decisions such as UE handover between cells, SN change, etc. The UE may lose coverage in its current serving cell (e.g., PCell in DC) and attempt handover to a target cell. Similarly, a UE in DC may lose coverage in its current PSCell and attempt an SN change. Other events may trigger other mobility-related procedures. A radio link failure (RLF) procedure is typically triggered in the UE when something unexpected happens in any of these mobility-related procedures. The RLF procedure involves interactions between RRC and lower layer protocols such as PHY (or LI), MAC, RLC, etc. including radio link monitoring (RLM) on LI.

[0068] The principle of RLM is similar in LTE and NR. In general, the UE monitors link quality of the UE’s serving cell (i.e., SpCell) and uses that information to decide whether the UE is in-sync (IS) or out-of-sync (OOS) with respect to that serving cell. In LTE, RLM is carried out by the UE measuring downlink reference signals (e.g., CRS) in RRC CONNECTED state. If RLM (i.e., by Ll / PHY) indicates number of consecutive OOS conditions to the UE RRC layer, then RRC starts a radio link failure (RLF) procedure and declares RLF after expiry of a timer (e.g., T310). The LI RLM procedure is carried out by comparing the estimated CRS measurements to some target block error rates (BLERs), called Qout and Qin. In particular, Qout and Qin correspond to BLER of hypothetical PDCCH / PCIFCH transmissions from the serving cell, with exemplary values of 10% and 2%, respectively. In NR, the network can define the RS type (e.g., CSLRS and / or SSB), exact resources to be monitored, and even the BLER target for IS and OOS indications.

[0069] In addition to providing coverage via “cells,” as in LTE, NR networks also provide coverage via “beams.” In general, a DL “beam” is a coverage area of a network-transmitted RS that may be measured or monitored by a UE. Such RS can include any of the following, alone or in combination: SS / PBCH block (SSB), channel state information RS (CSLRS), tertiary reference signals (or any other sync signal), positioning RS (PRS), demodulation RS (DMRS), phase- tracking reference signals (PTRS), etc. In general, SSB is available to all UEs regardless of RRC state, while other RS (e.g., CSI-RS, DMRS, PTRS) are associated with specific UEs that have a network connection, i.e., in RRC CONNECTED state.

[0070] To support beam management, a UE can be configured with a CSI measurement configuration, which instructs the UE to monitor CSI-RS and to send various CSI reports to the RAN (e.g., NG-RAN). For example, the RAN indicates an explicit list of CSI resources to be monitored by the UE for each type of CSI report the UE is configured to send. Similar techniques can be used for beam management based on SSB transmitted by the network.

[0071] During preparation for handover of a UE to a target node, the source node sends the current UE configuration to the target node in the HANDOVER REQUEST message. The target node prepares a target configuration for the UE based on the current configuration and the capabilities of the target node and the UE. The target node sends the target configuration to the source node in a HANDOVER REQUEST ACKNOWLEDGE message, which the source node encapsulates in an RRCReconfiguration message to the UE. As a streamlined option, the target configuration can be signalled as a “delta-configuration” including only the differences from the UE’s current configuration in the source cell.

[0072] To summarize, handover and other serving cell changes are triggered by layer 3 (L3, e.g., RRC) measurements and involves RRC signaling to change PCell and / or PSCell (e.g., when DC is configured), as well as release / add SCells (e.g., when CA is configured). Currently, L3 inter-cell mobility involves complete layer 2 (L2) and layer 1 (LI, i.e., PHY) resets, leading to longer latency, increased signaling overhead, and longer interruptions than for intra-cell beam switching. As discussed in the Background section above, the purpose of the LTM-triggered mobility procedures is to mitigate and / or completely avoid these problems in appropriate circumstances, by providing for a dynamic cell switching mechanism that does not require the execution of a layer 3 (RRC) reconfiguration procedure.

[0073] This text refers to the term “L1 / L2 based inter-cell mobility” as used in the Work Item Description in 3GPP, though it interchangeably also uses the terms L1 / L2 mobility, Ll-mobility, LI based mobility, Ll / L2-centric inter-cell mobility, L1 / L2 inter-cell mobility Ll / L2-Triggered Mobility, Lower-layer triggered Mobility or LTM. The basic principle is that the UE receives a lower layer signaling from the network indicating to the UE 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 / 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., in case the command triggers the UE to change to another cell group configuration of the same type (e.g., another MCG configuration). Before the UE receives the LTM cell switch command, the UE is configured by the network with one or more LTM candidate cell configurations (e.g., reception of an RRC Reconfiguration message, with at least one LTM candidate cell configuration). A LTM candidate cell configuration may include parameters in the information element (IE) CellGroupConfig for an LTM candidate cell and / or an embedded RRC Reconfiguration for an LTM candidate cell. The LTM cell switch command contains an LTM candidate configuration index, which identifies the target LTM candidate cell.

[0074] The term LTM cell switch procedure refers to the process of a UE switching (or changing) its cell from a source cell to a target cell (which may be called here an LTM candidate cell or a neighbor cell), using L1 / L2 -triggered mobility (LTM). In the context of Ll / L2-triggered mobility (LTM), an LTM cell switch procedure may sometimes also be known as L1 / L2 based inter-cell mobility execution, LTM execution, dynamic switch, LTM switch, (LTM) cell switch, (LTM) serving cell change or (LTM) cell change. In the context of the techniques described herein, switching to the LTM candidate cell comprises the UE considering that the LTM candidate cell becomes its new special cell (SpCell) e.g., PCell in case of LTM being configured for a Master Cell Group (MCG) and / or PSCell in case of LTM being configured for a Secondary Cell Group (SCG); or, changing its SpCell from the current PCell to an indicated LTM candidate cell. Note that while the terms “switch” or “change of cells” may be used to describe these procedures, this switch or change of cells may comprise a switch or change of an entire cell group configuration, which may include 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).

[0075] An LTM cell switch procedure may be triggered in the UE by reception of a LTM cell switch command, or alternatively, triggered by some other event, such as a condition, e.g., a triggering condition used for conditional configuration, such as conditional handover, being fulfilled, as a result of recovery from radio link failure or handover failure.

[0076] This text refers to an LTM candidate cell, which is a cell the UE is configured with when configured with L1 / L2 -triggered mobility. That is, an LTM candidate cell is a cell the UE can move to in a LTM cell switch procedure, upon reception of a LTM cell switch command. Such cells may also be called candidate cell(s), candidates, mobility candidates, non-serving cells, additional cells, target candidate cell, target candidate, etc. An LTM candidate cell is a cell the UE may perform measurements on (e.g., CSI measurements) so that the UE reports these measurements and network may take educated decision on which beam (e.g., TCI state) and / or cell the UE is to be switched to. An LTM candidate cell may be a candidate to be a target PCell or PSCell, or an SCell of a cell group (e.g., MCG SCell or a SCG SCell).

[0077] This document also refers to “at least one configured LTM candidate cell” and may indicate that the UE has received at least one LTM candidate cell configuration. This is also sometimes referred to as a configuration of a LTM candidate cell, which may be an RRC configuration, such as encapsulated in an RRC Reconfiguration message, that the UE receives when being configured with Ll / L2-Triggered Mobility. A configuration of a LTM candidate cell comprises the configuration which the UE needs to start to operate accordingly when it performs an LTM cell switch procedure to that LTM candidate cell, e.g., upon reception of the LTM cell switch command directing the UE to perform an LTM cell switch procedure to that LTM candidate cell, which becomes the target cell and the current (new) SpCell, or an SCell in a serving frequency.

[0078] The LTM candidate cell configuration comprises parameters of a serving cell (or multiple serving cells, such as a cell group), comprising one or more of the groups of parameters, such as an RRCReconfiguration message an IE CellGroupConfig or an IE SpCellConfig (or the IE SCellConfig, in the case of a Secondary Cell). An LTM candidate cell configuration may, for example, comprise one or more of: i) the PCell configuration and one or more SCell configuration(s) of a Master Cell Group (MCG); i) the PSCell configuration and one or more SCell configuration(s) of a secondary Cell Group (SCG). The terms (LTM) candidate configuration, LTM configuration, (LTM) candidate target cell configuration, (LTM) target candidate (cell) configuration may be used interchangeably when referring to configuration of a LTM candidate cell.

[0079] An LTM candidate cell configuration is associated with an identifier which can be used in signaling when referring to a certain LTM candidate cell configuration, such as when the UE receives the LTM candidate cell configuration and when the UE receives an LTM cell switch command indicating the UE to perform a LTM cell switch procedure to that LTM candidate cell. This identifier is sometimes known as the LTM candidate cell configuration identity or LTM candidate configuration index (or similar).

[0080] Thus, in L1 / L2 -triggered mobility, the UE receives an LTM cell switch command containing an LTM candidate configuration index, and during the LTM cell switch procedure this index is used by the UE to identify an LTM candidate cell configuration. The UE then performs an RRC procedure, here referred to as an RRC LTM execution procedure, or sometime as LTM execution procedure or LTM execution RRC procedure, to apply and process the content of the LTM candidate cell configuration, which in turn, based on the included information elements (IES) and fields inside the LTM candidate configuration, triggers execution of other RRC procedures related to those IEs and fields including configuration of lower layers (e.g. LI and sometimes also RLC and / or MAC) according to those included IEs and fields.

[0081] The actual LTM candidate cell configuration and its exact content and / or structure of this IE and / or embedded message may be called an RRC model for the candidate configuration, or simply RRC model. An LTM candidate cell configuration comprises the configuration which the UE needs to operate accordingly when it performs (executes) L1 / L2 based inter-cell mobility execution to a LTM candidate cell, upon reception of the lower layer signaling (MAC CE) indicating a L1 / L2 based inter-cell mobility to a LTM candidate cell (which becomes the target cell and the current (new) PCell, or an SCell in a serving frequency), or upon reception of the lower layer signaling (MAC CE) indicating a L1 / L2 based inter-cell mobility to a LTM candidate cell configuration indicated with a candidate configuration index (sometimes also denoted candidate configuration ID). The UE may be configured with multiple LTM candidate cell configurations, e.g., so that a candidate distributed unit (DU) generates and sends to the central unit (CU) multiple configuration(s). The actual LTM candidate cell configuration the UE receives during the LTM configuration may be a delta signaling to be applied on top of a reference configuration, so that the actual configuration the UE is to use in the candidate cell upon LTM cell switch is the combination of the LTM candidate cell configuration and the reference configuration (e.g., separately signaled by the network to the UE).

[0082] The LTM cell switch command may also contain a beam indication. The term “beam” may correspond to a spatial direction in which a signal is transmitted (e.g., by a network node) or received (e.g., by the UE), or a spatial filter applied to a signal which is transmitted or received. Thus, transmitting signals on different beams could correspond to transmitting signals in different spatial directions. When the text refers to a “beam which is selected” it may refer to a beam index and / or a Reference Signal (RS) index or identifier, such as a Synchronization Signal block (SSB) index, or a CSLRS resource identifier. Thus, selecting a beam may correspond to selecting an SSB, associated to an SSB index. Or, selecting a beam may correspond to selecting a CSLRS, associated to a CSLRS resource identifier.

[0083] The descriptions of various techniques herein may refer to an “indication of applied LTM candidate.” This indication of applied LTM candidate may be an indication of the target cell, such as a cell identifier (e.g. PCI, CGI), an indication of an LTM candidate cell configuration, such as an LTM candidate cell configuration index or LTM candidate cell configuration identity, an indication of a beam, such as an SSB index or an CSI-RS resource identifier or an indication of an index that identify a particular RRC message previously sent by the network and received by the UE.

[0084] The techniques described herein involve conditional LTM, which may be seen as a conditional reconfiguration in which execution conditions are associated to the evaluation of conditions associated to lower layer measurements e.g. Layer 1 (LI) RSRP, and / or SS-RSRP, based on SSB(s) and / or CSLRSs of a serving cell and / or of an LTM candidate cell. In this context, a conditional LTM uses an execution condition (or conditional LTM execution condition) or a combination of multiple executing conditions, that is / are evaluated, and when fulfilled, results in that the UE performs an action, such as executing the conditional reconfiguration (sometimes known as executing the condition) or conditional LTM; for example applying a message, parts of a message or at least one information element, or performing a serving cell switch or change. Known existing examples of conditional reconfiguration are conditional handover (CHO), Conditional PSCell Change (CPC) and Conditional PSCell Addition (CPA). According to the methods in the invention upon fulfillment of the execution conditions(s) the UE performs an LTM Cell Switch.

[0085] This document may refer to an LTM candidate cell for conditional LTM, which may be called a conditional LTM candidate cell, or, in the context of the present document, simply a candidate cell; or L1 / L2 inter-cell mobility candidate cell or target candidate cell for L1 / L2 inter-cell mobility to refer to a cell the UE is configured with when configured with conditional L1 / L2 inter-cell mobility; which is a cell the UE moves to or switches to in the execution of a conditional L1 / L2 inter-cell mobility procedure upon fulfillment of the associated execution condition. These cells may also be called candidate cells, candidates, mobility candidates, nonserving cells, additional cells, deactivated cells, etc.

[0086] In various methods described herein the UE receives an LTM candidate cell configuration for conditional LTM, for an LTM candidate cell. The LTM candidate cell configuration may be received in the form of an RRC Reconfiguration message (e.g. RRCReconfiguration) which the UE stores and applies upon fulfillment of the conditional LTM execution condition associated to that LTM candidate cell. The LTM candidate cell configuration contains parameters the UE uses to operate in the associated LTM candidate cell when the UE moves to it in an LTM Cell switch. The LTM candidate cell configuration may be applied on top of the UE’s current configuration and / or on top of a reference configuration (also received by the UE e.g. as part of a conditional LTM configuration).

[0087] In various methods described herein the UE receives a conditional LTM execution condition (e.g. a conditional LTM execution condition for use in a subsequent LTM). That may correspond to the UE receiving an indication of a conditional LTM execution condition and / or one or more parameters for configuring a conditional LTM execution condition e.g. event identifier, offset(s), threshold(s), reference signal type, trigger quantity, time to trigger, etc.

[0088] The text mentions the term “subsequent conditional LTM” to refer to a subsequent LTM procedure in which there are LTM cell switch procedures between candidate cells without RRC reconfiguration by the network in between, wherein these LTM cell switch procedures are triggered by the fulfillment of conditional LTM execution condition(s).

[0089] The lower layer measurement configuration discussed herein corresponds to a measurement configuration provided to the UE by the network instructing the UE to perform measurements on reference signal(s) for which measurements are typically reported on one or more message(s) on a protocol layer lower than the RRC and / or lower than L3 protocol layer in the UE’s protocol stack. These lower layer measurements derived by the UE are according to the lower layer measurement configuration are typically reported as Uplink Control Information (UCI) over a Physical Uplink Control Channel (PUCCH) and / or UCI over Physical Uplink Shared Channel (PUSCH).

[0090] Figure 5 shows an example of a possible signaling flow for the LTM cell switch procedure. This example starts with the execution of LTM cell switch procedure triggered by an LI measurement report from the UE. Prior to this step, the UE has already been configured with LTM candidate cell configuration(s), each of them represented as individual RRCReconfiguration messages stored by the UE. When the UE executes the LTM cell switch procedure it transmits an RRCReconfigurationComplete message in the target cell. This message can be seen as the “response” message that confirms that the UE has applied the RRCReconfiguration message representing the LTM candidate cell configuration for the particular LTM candidate cell.

[0091] This example illustrates the inter-DU case but the signaling is also applicable for intra-DU, with the difference that the source gNB-DU and the candidate gNB-DU is a single gNB-DU. In conditional LTM the UE needs to be configured with conditional LTM execution conditions to be evaluated, so that the UE executes an LTM cell switch upon the fulfillment of these conditions. In conditional handover (CHO), a similar principle is applicable. However, CHO is a higher layer procedure, relying on L3 measurements, so the existing framework for configuring execution conditions is not suitable for conditional LTM. For CHO, the serving Master Node (MN), which is controlling the serving PCell, decides the execution conditions for CHO configurations to other candidate target PCells. In a similar manner, it can be assumed that a serving node of the UE will decide the conditional LTM execution conditions.

[0092] One of the objectives of the Work Item in Rel-19 is the support of subsequent conditional LTM, which requires to the UE to be configured with all information needed for multiple / subsequent conditional LTM cell switches without the need for further RRC Reconfiguration(s) in between. In the specifications and agreements to date, it is not clear how conditional LTM execution conditions are to be configured at the UE since the first LTM configuration.

[0093] For normal (non-conditional) mobility it is the network node that controls the serving cell (i.e. the cell where the UE is currently located) that decides when to trigger mobility (e.g., a cell switch procedure) to another cell. This is typically based on measurement results that are received from the UE. Such decisions may then be different depending on what cell the UE is located in, as well as the characteristics of the target cell of the mobility procedure. For conditional LTM, the execution conditions for different LTM candidate cells should then in a similar way be decided by the network node that is controlling the cell where the UE is currently located (and could be set differently for different cells).

[0094] For the case of subsequent conditional LTM it is, however, also not clear how the UE can evaluate the different conditional LTM candidate configurations using execution conditions that are relevant for the current serving cell, i.e., using different execution conditions for the same LTM candidate configuration depending on which cell the UE is currently located in.

[0095] In some of the embodiments described in detail herein, these problems are addressed in techniques performed by a user equipment (UE) capable of conditional LTM, where the UE receives at least two conditional LTM configurations, with each having one or more conditional LTM execution conditions associated with it. An example of this is shown in Figure 6, is a signaling flow diagram focused on UE steps for subsequent conditional LTM when the UE is configured with the first and the second LTM candidate cells for conditional LTM and, while connected to a S-DU, the UE executes LTM cell switch to the first cell. As seen in Figure 6, after a conditional LTM configuration decision made in the network, the UE receives LTM candidate cell configurations for each of first and second cells, as well as a first conditional LTM execution condition associated with the first LTM candidate cell configuration and another conditional LTM execution condition, this one associated with the second LTM candidate cell configuration. The UE then evaluates fulfillment of at least the first conditional LTM execution condition, associated to the first LTM candidate cell configuration, and, upon fulfillment of the first conditional LTM execution condition, applies the first LTM candidate cell configuration, thus switching to the candidate cell associated with that first LTM candidate cell configuration. Subsequently to and in response to applying the first LTM candidate cell configuration, the UE begins evaluating another conditional LTM execution condition, this one associated to a second LTM candidate cell configuration. Thus, in the event this other conditional LTM execution condition is fulfilled, the UE may apply the second LTM candidate cell configuration, thereby carrying out a “subsequent conditional” LTM configuration, i.e., two LTM executions without any intervening RRC configuration signaling.

[0096] In some embodiments or instances, the first conditional LTM execution condition is associated to the first LTM candidate cell configuration by one or more measurements of the first LTM candidate cell being input to the first conditional LTM execution condition.

[0097] In some embodiments or instances, a configuration(s) for the other conditional LTM execution condition (associated with the second LTM candidate cell configuration is / are at least partially included in the first LTM candidate cell configuration the UE has applied. Thus, in some embodiments or instances, the configuration(s) for the first conditional LTM execution condition (associated with the first LTM candidate cell configuration) and the other conditional LTM execution condition (associated with the second LTM candidate cell configuration) are received within the same message or messages in which the first LTM candidate cell configuration has been received. Alternatively, of course, the configuration(s) of the other conditional LTM execution condition may be received in a different message on which the first conditional LTM execution condition has been received, in other embodiments or instances.

[0098] In some embodiments or instances, the other conditional LTM execution condition, i.e., the one associated with the second LTM candidate cell configuration and that is evaluated for fulfilment after application of the first LTM candidate cell configuration, is associated to at least one measurement configuration identifier of a lower layer measurement configuration of the first cell (e.g., included in the first LTM candidate cell configuration) of a candidate DU (C-DU). In some instances or embodiments, the other conditional LTM execution condition and the first LTM candidate cell configuration are associated to the same measurement configuration identifier of a lower layer measurement configuration of the first cell. In other embodiments or instances, the other conditional LTM execution condition and the first LTM candidate cell configuration are associated to different measurement configuration identifier of a lower layer measurement configuration of the first cell.

[0099] In some embodiments or instances, the UE performs one or more measurements (e.g., RSRP and / or RSRQ measurements for serving cell and / or LTM candidate cell(s)) used as input to the evaluation of the fulfillment of the other conditional LTM execution condition, in response to receiving the lower layer measurement configuration for configuring the other conditional LTM execution condition associated to the measurement configuration identifier.

[0100] In some embodiments or instances, the lower layer measurement configuration of the first candidate cell corresponds to an LTM CSI reporting configuration, where the measurement configuration identifier may correspond to a lower layer reporting configuration identifier.

[0101] In the method described above, the “other” conditional LTM execution condition, which is associated with the second LTM candidate cell configuration, is specifically for use after the UE applies the first LTM candidate cell configuration. The UE may be configured with a different conditional LTM execution condition, also associated with the second LTM candidate cell configuration that is evaluated by the UE along with the first conditional LTM execution condition, before the UE determines that the first conditional LTM execution condition is fulfilled and applies the first LTM candidate cell configuration. In other words, the UE may be evaluating multiple conditional LTM execution conditions at the same time (or during the same period), where each is associated with a particular one of multiple LTM candidate cell configurations.

[0102] Similarly, after a conditional LTM execution condition is fulfilled and the UE applies the corresponding LTM candidate cell configuration (e.g., the first LTM candidate cell configuration, in the scenario shown in Figure 6), the UE may again evaluate multiple conditional LTM execution conditions that were previously provided, each associated with an LTM candidate cell configuration. Significantly, for a given LTM candidate cell configuration, the conditional LTM execution condition that is evaluated at this point may differ from a conditional LTM execution condition, associated with that same LTM candidate cell configuration, that was evaluated prior to the UE applying the first LTM candidate cell configuration. Thus, the conditional LTM execution condition that is evaluated for a given LTM candidate cell configuration can be made to depend on the cell serving the UE at the time the conditional LTM execution condition is under evaluation.

[0103] As an example, referring to Figure 6, while the UE is evaluating the first conditional LTM execution condition, for the first cell, as shown in the figure, the UE may be also evaluating a second conditional LTM execution condition, for the second cell. Upon fulfilment of the first conditional LTM execution condition, the UE applies the first LTM candidate cell configuration as shown in the figure. Subsequently, as shown in the figure, the UE evaluates the “other” conditional LTM execution condition, for the second cell. This may differ from the second conditional LTM execution condition, also associated with the second LTM candidate cell configuration, that the UE was evaluating prior to applying the first LTM candidate cell configuration. In this manner, then, the conditional LTM execution condition evaluated for the second LTM candidate cell configuration changes, depending on whether the UE is served by the initial cell / DU, or whether it is served by the “first cell,” i.e., the cell to which the UE switched upon applying the first LTM candidate cell configuration.

[0104] In a similar manner, the UE may be configured ahead of time with yet another conditional LTM execution configuration, this one associated with the first LTM candidate cell configuration, that is to be evaluated by the UE in the event that it applies the second LTM candidate cell configuration, whether it does so instead of applying the first LTM candidate cell configuration or does so sometime after applying the first LTM candidate cell configuration.

[0105] Thus, in a variation of the method discussed above (and illustrated in Figure 6), the UE may receive a conditional LTM configuration including a first LTM candidate cell configuration and a second LTM candidate cell configuration, as well as a first conditional LTM execution condition associated with the first LTM candidate cell configuration and a second conditional LTM execution condition associated with the second LTM candidate cell configuration. These conditional LTM execution conditions are to be used by the UE while it remains served by the currently serving cell. The UE may further receive a third conditional LTM execution condition, this one also associated with the first LTM candidate cell configuration, and a fourth conditional LTM execution condition, this one being associated with the second LTM candidate cell configuration. In this example, the first and second conditional LTM execution conditions are evaluated, while the UE is served by the currently served cell, to determine whether to apply the first LTM candidate cell configuration or second LTM candidate cell configuration, respectively. The fourth conditional LTM execution condition is for use by the UE for evaluating whether to perform a subsequent LTM execution (to the second cell) in response to fulfilment of the first conditional LTM execution condition and application of the first candidate cell configuration. The third conditional LTM execution condition, on the other hand, is to be used by the UE for evaluating whether to perform a subsequent LTM execution (to the first cell) in response to fulfilment of the second conditional LTM execution and application of the second candidate cell configuration. It will be appreciated that the UE may be still further provided with at least a fifth conditional LTM execution condition, applying to some LTM candidate cell configuration other than the first and second LTM candidate cell configurations, for evaluation by the UE along with the third conditional LTM execution condition, after application of the first LTM candidate cell configuration and / or may be provided with at least a sixth conditional LTM execution condition, again applying to some LTM candidate cell configuration other than the first and second LTM candidate cell configurations, for evaluation by the UE along with the fourth conditional LTM execution condition after application of the second LTM candidate cell configuration.

[0106] Corresponding methods to those summarized above may be carried out by the network node controlling a serving cell or by a serving distributed unit (S-DU), where this network node or S- DU provides the configurations and condition configurations discussed above. Further methods may be carried out by network nodes controlling candidate cells, or by network nodes operating as a candidate distributed unit (C-DU), to support these subsequent conditional LTM techniques. An example is shown in Figure 7, which is a signaling flow focused on the C-DU steps for subsequent conditional LTM when the UE is configured with the first and the second LTM candidate cells for conditional LTM, for configuring conditional LTM execution conditions for when the UE switches to the C-DU, in subsequent LTM.

[0107] For example, as shown in Figure 7, such a network node may:

[0108] - receive a request message from a Central Unit (CU) for requesting the C-DU to configure a first cell of the C-DU as an LTM candidate cell for conditional LTM (first conditional LTM candidate cell), where the request message also includes a resource configuration comprising at least an indication of a second cell (e.g., not from the C-DU) to be configured as an LTM candidate cell for conditional LTM for subsequent LTM (second conditional LTM candidate cell); and,

[0109] - in response, transmit a response message to the CU including: o lower layers configuration for the first conditional LTM candidate cell, and another conditional LTM execution condition associated to the second conditional LTM candidate cell (for subsequent LTM). In various embodiments or instances, the request message may correspond to a UE CONTEXT SETUP REQUEST message and the response message is the UE CONTEXT SETUP RESPONSE message. In other embodiments or instances, the request message may correspond to a UE CONTEXT MODIFICATION REQUEST message and the response message is the UE CONTEXT MODIFICATION RESPONSE message.

[0110] In some embodiments or instances, in the same message in which the C-DU is requested to configure conditional LTM for one of its cell(s) the C-DU also receives a resource configuration indicating one or more potential LTM candidate cell(s) and / or RS ID(s) of these cells, for subsequent conditional LTM.

[0111] In some embodiment or instances, the configuration of the other conditional LTM execution condition, i.e., the conditional LTM execution condition associated with the second conditional LTM candidate cell and for evaluation by the UE after application of the first LTM candidate cell configuration, may be provided within the lower layer configuration of the first conditional LTM candidate cell, which is to be applied by the UE when the UE executes a conditional LTM cell switch to the first conditional LTM candidate cell.

[0112] The indication of the second conditional LTM candidate cell (e.g., not from the C-DU) for subsequent LTM which the C-DU receives may correspond to an LTM candidate ID and / or another information of the second conditional LTM candidate cell; the indication of the second conditional LTM candidate cell indicates to the C-DU that the second conditional LTM candidate cell is to be considered an LTM candidate cell when the UE switches to the first cell of the C-DU in an LTM Cell Switch. That is why the C-DU, in response to the request message, generates the “another” conditional LTM execution condition discussed above, which is associated to the second conditional LTM candidate cell, so that when the UE switches to the first cell of the C-DU, the UE evaluates this other conditional LTM execution condition, associated to the second conditional LTM candidate cell (which is a candidate when the UE is in the C-DU).

[0113] One of the benefits of this approach is that the same candidate DU that will become responsible for the LTM Cell Switch in case of subsequent LTM towards that candidate DU is also responsible, under the approach described above, for defining the execution conditions for the UE for executing conditional LTM in a subsequent conditional LTM. In other words, the C-DU determining to trigger LTM cell Switch in case of legacy subsequent LTM, when that C-DU becomes a new serving DU, so that it makes sense that it is also the S-DU that determines the LTM execution conditions. It is also the C-DU that determines whether a report for legacy LTM is periodic, aperiodic or semi-persistent for subsequent LTM, for when the C-DU becomes the new serving DU.

[0114] Another benefit is that by defining the conditional LTM execution condition(s) as part of the lower layer measurement configuration, the UE can perform measurements according to its existing configuration(s) and simply associates these measurements as input to the evaluation of the conditional LTM execution condition(s), which simplifies the signaling structure and reduces the number of bits for configuring conditional LTM.

[0115] Further details of various techniques performed by the UE are provided here. These techniques include a method at a User Equipment (UE) capable of conditional LTM, in which the UE receives a conditional LTM configuration including a first LTM candidate cell configuration and a second LTM candidate cell configuration. This may be received in an RRC Reconfiguration message (RRCReconfiguration). In the same message or in a different message the UE further receives:

[0116] - a first conditional LTM execution condition associated to the first LTM candidate cell configuration; and,

[0117] - a second conditional LTM execution condition associated to the second LTM candidate cell configuration (for subsequent LTM).

[0118] In response to receiving the conditional LTM configuration the UE evaluates the fulfillment of the first conditional LTM execution condition associated to the first LTM candidate cell configuration and, upon fulfillment of the first conditional LTM execution condition, the UE applies the first LTM candidate cell configuration, switches to the first cell. Subsequently to and in response to this application of the first LTM candidate cell configuration, the evaluates the second conditional LTM execution condition, which is associated to the second LTM candidate cell configuration. In other words, the UE only evaluates the second conditional LTM execution condition when it switches to the first cell.

[0119] The UE may be configured with first and second candidate cells to be monitored from the start, while the UE is connected to a serving DU (S-DU). In that case, the UE capable of conditional LTM, may receive a conditional LTM configuration including a first LTM candidate cell configuration and a second LTM candidate cell configuration, e.g., in an RRC Reconfiguration message. Then, in the same message or in one or more different messages the UE further receives: - a first conditional LTM execution condition associated to the first LTM candidate cell configuration. This is the same “first” conditional LTM execution condition discussed above.

[0120] - a second conditional LTM execution condition associated to the second LTM candidate cell configuration. As will be seen below, this is a different “second” conditional LTM execution condition from the one discussed above, as this second conditional LTM execution condition is for use by the UE while it is connected to the S-DU.

[0121] - a third conditional LTM execution condition, associated to the first LTM candidate cell configuration.

[0122] - a fourth conditional LTM execution condition, associated to the second LTM candidate cell configuration. As will be seen below, this fourth conditional LTM execution condition corresponds to the “second” conditional LTM execution discussed in the previous example.

[0123] In this variation of the UE-based technique, the UE, in response to receiving the conditional LTM configuration, evaluates the fulfillment of the first conditional LTM execution condition associated to the first LTM candidate cell configuration and also evaluates the fulfillment of the second conditional LTM execution condition, which is associated to the second LTM candidate. Since the first conditional LTM execution condition and the second conditional LTM execution condition are being evaluated while the UE is connected to the S-DU, either of these conditions may be fulfilled, with the condition that is fulfilled dictating whether the UE applies the first LTM candidate cell configuration or the second candidate cell configuration. Neither of the third and fourth conditional LTM execution conditions is used until after a conditional LTM execution is completed.

[0124] In one case, upon fulfillment of the first conditional LTM execution condition, the UE applies the first LTM candidate cell configuration and, in response, evaluates the fourth conditional LTM execution condition, associated to the second LTM candidate cell configuration. This corresponds to the flow shown in Figure 6. In another case, upon fulfillment of the second conditional LTM execution condition, the UE applies the second LTM candidate cell configuration and, in response to it, evaluates the third conditional LTM execution condition associated to the first LTM candidate cell configuration. In this event, the UE does not delete or remove the first and second conditional LTM execution condition(s) but instead will evaluate them again after performing an LTM cell switch (which may also be conditional) to the cell that was previous to the first conditional LTM execution. The first conditional LTM execution condition is described above as being associated to the first LTM candidate cell configuration. The association may be by one or more measurements of the first LTM candidate cell being input to the first conditional LTM execution condition. For example, when the condition is defined as “conditional LTM candidate cell becomes offset better than PCell (e.g. in more general terms SpCell of PSCell, incase of a Secondary Cell Group - SCG conditional LTM)” and a trigger quantity is defined as RSRP, the UE uses one or more RSRP measurements of the first cell to be compared with RSRP measurements of the Primary Cell (PCell).

[0125] The second conditional LTM execution condition is described above as being associated to the second LTM candidate cell configuration. Again, this may be by one or more measurements of the second LTM candidate cell being used as input to the second conditional LTM execution condition. For example, when the condition is defined as “conditional LTM candidate cell becomes offset better than serving cell (e.g. PCell, SpCell, PSCell)” and a trigger quantity is defined as RSRP, the UE uses one or more RSRP measurements of the second cell to be compared with RSRP measurements of the serving cell, e.g., PCell.

[0126] Given this configuration, in a first case, upon fulfillment of the first conditional LTM execution condition while the UE is in the S-DU, the UE applies the first LTM candidate cell configuration and, in response, switches to the first cell and starts evaluating the fulfillment of the fourth conditional LTM execution condition, which is associated to the second LTM candidate cell configuration. The configuration(s) for the fourth conditional LTM execution condition may be at least partially included in the first LTM candidate cell configuration the UE has applied. In other words, when the UE switches to the first cell, the second cell is still a candidate and for that the UE needs to evaluate the conditional LTM execution conditions for it. For example, the configuration(s) for the fourth conditional LTM execution condition may be included at least partially in a lower measurement configuration of the first LTM candidate cell configuration (e.g. in an LTM CSI reporting configuration), so that the UE perform measurements and evaluates the fourth condition only when it switches to the first cell i.e. after an LTM cell switch to that first cell.

[0127] In a second case, upon fulfillment of the second conditional LTM execution condition while the UE is in the S-DU, the UE applies the second LTM candidate cell configuration and, in response, switches to the second cell and starts evaluating the fulfillment of the third conditional LTM execution condition associated to the first LTM candidate cell configuration. The configuration(s) for the third conditional LTM execution condition may be at least partially included in the second LTM candidate cell configuration the UE has applied. In other words, when the UE switches to the second cell, the first cell is still a candidate and for that the UE needs to evaluate the conditional LTM execution conditions for it. For example, the configuration(s) for the third conditional LTM execution condition may be included at least partially in a lower measurement configuration of the second LTM candidate cell configuration (e.g. in an LTM CSI reporting configuration), so that the UE perform measurements and evaluates the third condition only when it switches to the second cell i.e. after an LTM cell switch to that second cell.

[0128] It will be appreciated that this example can be extended to include more than the first and second cells described here, for either or both of the first evaluation of conditional LTM execution conditions, prior to one being fulfilled and an LTM candidate cell configuration being applied, and the second evaluation of conditional LTM execution conditions, i.e., the evaluation of conditions for a subsequent conditional LTM execution, after the application of an LTM candidate cell configuration. At each of these stages (which may continue for additional stages), the conditional LTM execution condition associated with a given LTM candidate cell configuration may change, depending on the then-current serving cell configuration.

[0129] Figure 8 illustrates a signaling flow focused on the UE steps when the UE is configured with execution conditions for the first and the second cells, evaluated while the UE is connected to the S-DU, and the UE executes an LTM cell switch to the first cell. This corresponds to the first of the two cases described immediately above. Figure 9 shows the relationships between the LTM candidate cell configurations and the conditional LTM execution conditions referred to in Figure 8 and in the scenario described immediately above.

[0130] In various embodiments and instances of the techniques described herein, a conditional LTM execution condition for subsequent LTM may be associated to a measurement configuration identifier of the UE’s measurement configuration. For example, the fourth conditional LTM execution condition described above may be associated to at least one measurement configuration identifier of a lower layer measurement configuration of the first cell (e.g., included in the first LTM candidate cell configuration) of a candidate DU (C-DU), which may later become a new S-DU the UE connects to when the UE switches to the first cell. When the candidate DU (C-DU) becomes the new S-DU for the UE, i.e., when the UE switches to a cell of that C-DU (e.g. cell switch to the first cell), the UE applies the first LTM candidate cell configuration and, consequently, the lower layer measurement configuration of the first cell, and starts evaluating the fourth conditional LTM execution condition which has measurement(s) of the second cell as input to it.

[0131] The measurement configuration identifier may be an LTM CSI reporting configuration identifier. In one sub-option, the measurement configuration identifier is part of the conditional LTM configuration, while the actual configuration of the fourth conditional LTM execution condition is inside the first candidate configuration. In that option, in response to applying the configuration of the first LTM candidate cell configuration, the UE evaluates the fulfillment of the fourth conditional LTM execution condition. In other words, the UE determines what condition to evaluate for the second LTM candidate cell, after the LTM cell switch to the first cell, by determining the measurement configuration identifier associated to the second conditional LTM candidate cell and checking the lower layer measurement configuration of the first conditional LTM candidate cell associated to that measurement configuration identifier.

[0132] According to various embodiments or instances, when applying the first conditional LTM candidate cell configuration, and its lower layer measurement configuration for configuring the fourth conditional LTM execution condition associated to a measurement configuration identifier, the UE performs one or more lower layer measurements (e.g., LI RSRP, RSRP and / or RSRQ measurements for serving cell and / or LTM candidate cell(s)) used as input to the evaluation of the fulfillment of the fourth conditional LTM execution condition. The lower layer measurement configuration of the first candidate LTM candidate cell of the C-DU may correspond to an LTM CSI reporting configuration, where the measurement configuration identifier may correspond to a reporting configuration identifier. One example of a LTM CSI reporting configuration is the LTM-CSI-ReportConfig IE (or an instance of the IE) which includes the configuration of the conditional LTM execution condition.

[0133] Figure 10 illustrates an example of the configuration the UE may receive in an RRC Reconfiguration message, and how it works in subsequent LTM. In the conditional LTM configuration, the UE has a first LTM candidate cell configuration associated to a measurement configuration identifier =X which points to a measurement configuration in the UE’s current configuration when the UE is in PCell A of the S-DU, which contains the first conditional LTM execution. The UE monitors the first conditional LTM execution condition and when that is fulfilled, the UE switches to the first conditional LTM candidate cell by applying the configuration of the first LTM candidate cell. Within the configuration of the first LTM candidate is the lower layer measurement configuration the UE needs for operation in the first cell, and that contains a measurement configuration identifier = Y, and the fourth conditional LTM execution condition.

[0134] In another option, the first, second, third, and fourth conditional LTM execution condition may be part of the same lower layer measurement configuration. This means that even if the first and second LTM candidate cell configuration are separate configurations, they both point to the same measurement configuration identifier. This in practice means that all the four conditional LTM execution conditions may be part of the same LTM CSI reporting configuration which refer to a LTM CSI resource configuration which includes both the first and second LTM candidate cell configurations.

[0135] In some embodiments or instances, there is no change between association of measurement configuration identifier and Conditional LTM candidate cell upon LTM cell switch.

[0136] Let us assume an example in which the UE, while connected to the S-DU, receives an RRC Reconfiguration message (e.g., RRCReconfiguration) including a conditional LTM configuration with, e.g., two LTM candidate cells, as follows:

[0137] RRC Reconfiguration

[0138] Conditional LTM configuration o LTM Candidate configuration

[0139] ■ LTM Candidate ID=1

[0140] ■ First LTM candidate cell configuration

[0141] ■ Measurement configuration identifier=X o LTM Candidate configuration

[0142] ■ LTM Candidate ID=2

[0143] ■ Second LTM candidate cell configuration

[0144] ■ Measurement configuration identifier=Y

[0145] In one option, the association between a measurement configuration identifier and an LTM candidate cell configuration does not change when the UE switches from the PCell to a conditional LTM candidate cell e.g. upon fulfillment of a conditional LTM execution condition. In the example above, the UE may change to the second cell (LTM Candidate ID=2), and the association between the first LTM candidate cell configuration and the Measurement configuration identifier=X remains. In another alternative, the measurement configuration identifier for both the LTM candidate cell with LTM candidate ID=1 and the LTM candidate cell with LTM candidate ID=2 is the same (e.g., either “X” or “Y”). It is possible to have such configuration because even if the configuration is the same, the measurements done by the UE are performed on different SSBs for the LTM candidate cell with LTM candidate ID=1 and the LTM candidate cell with LTM candidate ID=2.

[0146] However, the measurement configuration which the measurement identifier points to is modified, and the measurement configuration identifier points to the measurement configuration with the same identifier in the UE’s new configuration after the LTM Cell switch i.e. when the UE executes an LTM cell switch upon fulfilment of the conditional LTM execution condition. For example, when the UE is connected to the serving cell (e.g., PCell A) in the S-DU, the measurement configuration identifier=X points to the lower layer measurement configuration of the PCell A, in which the first conditional LTM execution condition has been configured. After the UE switches e.g. to the second LTM candidate cell (and applies the second LTM candidate cell configuration) the UE keeps the LTM configuration i.e. the measurement configuration identifier=X remains associated to the first LTM candidate cell configuration; However, the UE measurement configuration identifier =X now points to a lower layer measurement configuration of the second LTM candidate cell configuration, in which the third conditional LTM execution condition is configured. In other words, the same measurement configuration identifier=X associated to the first cell now points to the third conditional LTM execution condition which is in the lower layer measurement configuration of the second cell the UE is not connected to.

[0147] As part of that option, a candidate DU (C-DU) which generates a conditional LTM execution condition for an LTM candidate cell for subsequent LTM (e.g. cell B, possibly of another C- DU*), as part of a lower layer measurement configuration, needs to use the same measurement configuration identifier which is to be used by other DU(s) also considering cell B as a conditional LTM candidate cell, so that the LTM configuration is consistent in associating the LTM candidate cell configuration of cell B with a measurement configuration identifier, and, regardless where the UE is connected to in subsequent LTM, the measurement configuration identifier points to the conditional LTM execution condition (i.e. the lower layer measurement configuration) meant to be used for that LTM candidate cell. Thus, when a Candidate DU receives a request for configuring conditional LTM with an indication of one of its LTM candidate cell being requested, and at least an indication of another LTM candidate cell (e.g. candidate cell B) to be a candidate for subsequent LTM, the candidate CU also receives an association between the candidate cell for subsequent LTM (e.g. cell B) and a measurement configuration identifier assigned by the CU. Together with the measurement configuration identifier, the candidate CU may also receive the measurement configuration to which the measurement configuration identifier refer to. In fact, even if the measurement configuration identifier stays the same across multiple DU, if the measurement configuration to which the measurement configuration identifier points to is different, this will be considered as a reconfiguration at the new and therefore the subsequent LTM cannot be supported.

[0148] For example, suppose that the CU determines to configure conditional LTM with candidate cell A from C-DU, candidate cell B from the C-DU* and candidate cell C from the C-DU**:

[0149] - When the CU request conditional LTM to the C-DU (e.g. by sending an UE CONTEXT SETUP REQUEST) requesting cell A, and indicating the candidates cell B and Cell C for subsequent LTM (e.g. in a resource configuration), the CU indicates to the C-DU that cell B is associated to measurement identifier=X, and cell C is associated to measurement identifier=Y and together with these identifier it may also send the related measurement configuration to which the identifier refers to. In response, the C-DU determines the conditional LTM execution condition for cell B, configures it in cell A’s lower layer measurement configuration and associates it to the measurement identifier=X. Also, the C-DU determines the conditional LTM execution condition for cell C, configures it in cell A’s lower layer measurement configuration and associates it to the measurement identifier=Y.

[0150] - And, when the CU request conditional LTM to the C-DU* (e.g. by sending an UE CONTEXT SETUP REQUEST) requesting cell B, and indicating the candidates cell A and Cell C for subsequent LTM (e.g. in a resource configuration), the CU indicates to the C-DU* that cell C is associated to measurement identifier=Y (as also indicated to the C- DU), and cell A is associated to measurement identifier=Z. In response, the C-DU* determines the conditional LTM execution condition for cell C, configures it in cell B’s lower layer measurement configuration and associates it to the measurement identifier=Y. Also, the C-DU* determines the conditional LTM execution condition for cell A, configures it in cell B’s lower layer measurement configuration and associates it to the measurement identifier=Z.

[0151] - And, when the CU request conditional LTM to the C-DU** (e.g. by sending an UE CONTEXT SETUP REQUEST) requesting cell C, and indicating the candidates cell B and Cell C for subsequent LTM (e.g. in a resource configuration), the CU indicates to the C-DU** that cell B is associated to measurement identifier=X (as also indicated to the C-DU), and cell A is associated to measurement identifier=Z. In response, the C-DU* determines the conditional LTM execution condition for cell B, configures it in cell C’s lower layer measurement configuration and associates it to the measurement identifier=X. Also, the C-DU** determines the conditional LTM execution condition for cell A, configures it in cell C’s lower layer measurement configuration and associates it to the measurement identifier=Z.

[0152] In summary, a C-DU receives a UE CONTEXT SETUP REQUEST requesting a conditional LTM candidate cell, and including a resource configuration indicating as conditional LTM candidate cell for subsequent LTM; and, for the conditional LTM candidate cell including an associated measurement configuration identifier (e.g. LTM CSI reporting configuration identifier). In response, the C-DU transmits a UE CONTEXT SETUP RESPONSE including the lower layer configuration of its accepted conditional LTM candidate cell, including a lower layer measurement configuration including the indicated measurement configuration identifier pointing to the configuration of the conditional LTM execution condition for the indicated conditional LTM candidate cell for subsequent LTM.

[0153] In another option, the C-DU receives a UE CONTEXT MODIFICATION REQUEST requesting the modification of a conditional LTM, and including a resource configuration indicating as conditional LTM candidate cell for subsequent LTM; and, for the conditional LTM candidate cell including an associated measurement configuration identifier (e.g. LTM CSI reporting configuration identifier). In response, the C-DU transmits a UE CONTEXT MODIFICATION RESPONSE including the lower layer configuration of its accepted conditional LTM candidate cell, including a lower layer measurement configuration including the indicated measurement configuration identifier pointing to the configuration of the conditional LTM execution condition for the indicated conditional LTM candidate cell for subsequent LTM.

[0154] In some other embodiments or instances, there is a change in the association of measurement configuration identifier and Conditional LTM candidate cell upon LTM cell switch.

[0155] In one option, the association between a measurement configuration identifier and an LTM candidate cell configuration is modified when the UE switches between cells with a conditional LTM cell switch (i.e. upon fulfillment of a conditional LTM execution condition). When the UE applies the candidate configuration a new mapping between candidate and measurement configuration identifier is also provided; as a result the LTM candidate configuration may change.

[0156] Still further details applicable to some embodiments or instances of the techniques described above are provided here. In one option, the fourth conditional LTM execution condition discussed above may correspond to the following “LTM candidate cell becomes amount of offset better than serving cell (e.g. PCell / PSCell). ” The UE considers the conditional LTM condition as fulfilled when the condition(s) applicable for this event is fulfilled for the applicable cell (i.e. LTM candidate cell associated to the condition) for all measurements taken during the corresponding time to trigger defined for this event (in case a time to trigger is defined). The so- called entry condition(s) for such an event, associated to the conditional LTM execution condition may be defined so that the UE shall consider the condition for this event to be satisfied when the condition below, as specified below, is fulfilled:

[0157] Mn - Hys > Mp + Off.

[0158] The variables in this formula are defined as follows:

[0159] Mn is the lower layer measurement result (e.g. LI RSRP) of the LTM candidate cell, not taking into account any offsets.

[0160] Mp is the lower layer measurement result (e.g. LI RSRP) of the serving cell (SpCell=), not taking into account any offsets.

[0161] Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigNR for this event).

[0162] Off is the offset parameter for this event (i.e. Offset as defined within LTM-CSI- ReportConfigNR for this event).

[0163] Mn, Mp are expressed in dBm in case of RSRP, or in dB.

[0164] Hys, Off are expressed in dB.

[0165] In one option, the fourth conditional LTM execution condition may correspond to the following “best SSB of the LTM candidate cell becomes amount of offset better than the serving SSB

[0166] - The best SSB of the LTM candidate cell may corresponds to the SSB with highest trigger quantity e.g. when the trigger quantity is set to RSRP, the best SSB of the LTM candidate cell is the SSB with highest LI RSRP or RSRP.

[0167] - The serving SSB may corresponds to the SSB of the serving cell (e.g. PCell, SpCell) with highest trigger quantity e.g. when the trigger quantity is set to RSRP, the best SSB of the PCell is the SSB with highest LI RSRP or RSRP of the PCell. Alternatively, the serving SSB may correspond to the SSB whose SSB index is configured as Quasi-Co- Location (QCL) source of the activated Transmission Configuration Indication (TCI) state of the serving cell (e.g. of the PCell).

[0168] The UE considers the conditional LTM condition as fulfilled when the condition(s) applicable for this event is fulfilled for the applicable cell (i.e. LTM candidate cell associated to the condition) for all measurements taken during the corresponding time to trigger defined for this event (in case a time to trigger is defined). The so-called entry condition(s) for such an event, associated to the fourth conditional LTM execution condition may be defined so that the UE shall consider the condition for this event to be satisfied when the condition below, as specified below, is fulfilled:

[0169] Mn - Hys > Mp + Off .

[0170] The variables in the formula are defined as follows:

[0171] Mn is the lower layer measurement result (e.g. LI RSRP) of the best SSB of the LTM candidate cell, not taking into account any offsets.

[0172] Mp is the lower layer measurement result (e.g. LI RSRP) of the best SSB of the serving cell (SpCell=), not taking into account any offsets.

[0173] Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigNR for this event).

[0174] Off is the offset parameter for this event (i.e. Offset as defined within LTM-CSI- ReportConfigNR for this event).

[0175] Mn, Mp are expressed in dBm in case of RSRP, or in dB.

[0176] Hys, Off are expressed in dB.

[0177] In one option, the fourth conditional LTM execution condition may correspond to the following “best beam of the LTM candidate cell becomes amount of offset better than the current beam

[0178] - The best beam of the LTM candidate cell may corresponds to the beam (spatial direction) with highest trigger quantity e.g. when the trigger quantity is set to RSRP, the best beam of the LTM candidate cell is the beam with highest LI RSRP or RSRP.

[0179] - The serving beam , or current beam, may corresponds to the beam of the serving cell (e.g. beam of the PCell, beam of the SpCell) with highest trigger quantity e.g. when the trigger quantity is set to RSRP, the best beam of the PCell is the beam with highest LI RSRP or RSRP of the PCell. Alternatively, the serving beam may correspond to the beam whose beam index is configured as Quasi-Co-Location (QCL) source of the activated Transmission Configuration Indication (TCI) state of the serving cell (e.g. of the PCell).

[0180] The lower layer measurement configuration associated to the conditional LTM execution condition may include one or more of the following parameters, in various embodiments or instances:

[0181] - Conditional event identifier: the identifier identifies the exact event he UE is supposed to monitor / evaluate; - Offset: indicates to the UE the offset value in dB to be used for comparing the LTM candidate cell with the serving cell. That is associated to a trigger quantity, such as LI RSRP, LI RSRQ, LI SINR, which is also part of the configuration.

[0182] - Trigger quantity: indicates to the UE the trigger quantity the UE needs to measure for the serving cell (e.g. PCell / PSCell) and the LTM candidate cell (for evaluating the trigger condition);

[0183] - Time to Trigger: indication of amount of time for how long lower layer measurements needs to fulfill the conditional LTM execution condition for the UE to consider the condition as fulfilled.

[0184] - Hysteresis: indication of an amount of hysteresis to be consider in the condition;

[0185] - Reference Signal type: indication of the RS type for which measurements are to be performed such as Synchronization Signal Block (SSB) or Channel State Information - Reference Signal (CSLRS). In one option, the configuration of the RS type may indicate to the UE to consider only the resources in the resource configuration for that Rs type;

[0186] In one option, the lower layer measurement configuration associated to the conditional LTM execution condition is associated to a resource configuration. For example, the lower layer measurement configuration may correspond to a reporting configuration which includes a pointer to a resource configuration.

[0187] In one example, the resource configuration which is indicated in the measurement configuration (e.g. a resource configuration ID within an LTM CSI ReportConfig) of the configuration of the conditional LTM candidate cell to be applied upon fulfillment of the fist condition, may be associated to one or more LTM candidate cell(s) and / or one or more Reference Signal (RS) identifier(s) e.g. a list of LTM candidate ID(s) and a list of SSB indexes. For example, let us assume an instance of the IE LTM-CSI-ResourceConfig-rl8 (having an associated identifier e.g. ltm-CSI-ResourceConfigId-rl8) and being grouped in as a resource set (e.g. in the IE LTM-CSL SSB-ResourceSet-rl8), wherein the resource set may be structure as a first and a second list, wherein the first list comprises one or more SSB indexes and the second list comprises one or more LTM candidate cell identifiers (IDs), wherein the position in the list is associated to an LTM CSI resource in that LTM CSI resource configuration e.g. the instance of the IE LTM-CSL ResourceConfig includes the following lists ltm-CSI-SSB-ResourceList-rl8 and Itm- Candi dateldLi st-r 18 : ltm-CSI-SSB-ResourceList-rl8 ltm-CandidateIdList-rl8

[0188] • [SSB1] [LTM Candidate cell ID 1] • [SSB2] [LTM Candidate cell ID 1]

[0189] • [SSB3] [LTM Candidate cell ID 1]

[0190] • [SSB4] [LTM Candidate cell ID 1]

[0191] • [SSB5] [LTM Candidate cell ID 1]

[0192] • [SSB1] [LTM Candidate cell ID 2]

[0193] • [SSB2] [LTM Candidate cell ID 2]

[0194] • [SSB3] [LTM Candidate cell ID 2]

[0195] • [SSB4] [LTM Candidate cell ID 2]

[0196] • [SSB5] [LTM Candidate cell ID 2]

[0197] • [SSB1] [LTM Candidate cell ID 3]

[0198] • [SSB2] [LTM Candidate cell ID 3]

[0199] • [SSB3] [LTM Candidate cell ID 3]

[0200] • [SSB4] [LTM Candidate cell ID 3]

[0201] • [SSB5] [LTM Candidate cell ID 3]

[0202] • [SSB1] [LTM Candidate cell ID 4]

[0203] • [SSB2] [LTM Candidate cell ID 4]

[0204] • [SSB3] [LTM Candidate cell ID 4]

[0205] • [SSB4] [LTM Candidate cell ID 4]

[0206] • [SSB5] [LTM Candidate cell ID 4]

[0207] • [SSB1] [LTM Candidate cell ID 5]

[0208] • [SSB2] [LTM Candidate cell ID 5]

[0209] • [SSB3] [LTM Candidate cell ID 5]

[0210] • [SSB4] [LTM Candidate cell ID 5]

[0211] • [SSB5] [LTM Candidate cell ID 5]

[0212] In another option, the resource configuration may simply be a list of LTM candidate cell identifiers or information identifying the LTM candidate cells for which the S-DU should generate and provide a conditional LTM execution condition.

[0213] In another option, the resource configuration is not indicated in the lower layer measurement configuration configuring the conditional LTM execution condition, or the UE ignores it. That is possible since the UE knows the LTM candidate cell to be evaluated since the measurement configuration identifier is associated to the LTM candidate cell, and that is the applicable cell for that event i.e. the cell to be evaluated. Further details of various embodiments or instances from the C-DU perspective are provided here. The techniques described above include a method at a network node operating as a candidate DU (C-DU) for subsequent conditional LTM, in which the C-DU receives a request message from a Central Unit (CU) for requesting the C-DU to configure a first cell of the C-DU as an LTM candidate cell for conditional LTM (first conditional LTM candidate cell). The request message also includes a resource configuration including at least an indication of a second cell (e.g., not from the C-DU) to be configured as an LTM candidate cell for conditional LTM for subsequent LTM (second conditional LTM candidate cell).

[0214] In response, the C-DU transmits a response message to the CU including lower layers configuration for the first conditional LTM candidate cell, and a conditional LTM execution condition associated to the second conditional LTM candidate cell, for use by the UE in evaluating subsequent conditional LTM.

[0215] The indication of the second conditional LTM candidate cell (e.g., not from the C-DU) for subsequent LTM which the C-DU receives may correspond to an LTM candidate ID and / or another information of the second conditional LTM candidate cell; the indication of the second conditional LTM candidate cell indicates to the C-DU that the second conditional LTM candidate cell is to be considered an LTM candidate cell when the UE switches to the first cell of the C-DU in an LTM Cell Switch. That is why the C-DU, in response to the request message, generates the conditional LTM execution condition associated to the second conditional LTM candidate cell, so that when the UE switches to the first cell of the C-DU, the UE evaluates the fourth conditional LTM execution condition associated to the second conditional LTM candidate cell (which is a candidate when the UE is in the C-DU).

[0216] In one option, the request message may correspond to a UE CONTEXT SETUP REQUEST message (as shown in Figure 3) and the response message is the UE CONTEXT SETUP RESPONSE message. Thus, in the same message in which the C-DU is requested to configure conditional LTM for one of its cell(s) (e.g. first conditional LTM candidate cell), the C-DU also receives a resource configuration indicating one or more potential LTM candidate cell(s) and / or RS ID(s) of these cells, for subsequent conditional LTM, so that in response the C-DU may include the configuration of the conditional LTM execution condition associated to the potential LTM candidate cell, so that in case the UE performs an LTM cell switch execution to the requested LTM candidate cell of the C-DU (first conditional LTM candidate cell), the UE evaluates the conditional LTM execution condition associated to the potential LTM candidate cell without the need to an additional RRC Reconfiguration after the LTM cell switch to the first cell i.e. enabling subsequent conditional LTM cell switch.

[0217] In one option, the request message may correspond to a UE CONTEXT MODIFICATION REQUEST message and the response message is the UE CONTEXT MODIFICATION RESPONSE message. Thus, after the C-DU has provided the lower layer configuration(s) for one of its cell(s) (e.g. first conditional LTM candidate cell), the C-DU receives another message, this time including a resource configuration indicating one or more potential LTM candidate cell(s) and / or RS ID(s) of these cells, for subsequent conditional LTM, so that in response the C- DU may include the configuration of the conditional LTM execution condition associated to the potential LTM candidate cells, so that in case the UE performs an LTM cell switch execution to the previously requested LTM candidate cell of the C-DU (first conditional LTM candidate cell), the UE evaluates the conditional LTM execution condition associated to the potential LTM candidate cell without the need to an additional RRC Reconfiguration after the LTM cell switch to the first cell i.e. enabling subsequent conditional LTM cell switch. In Figure 7, this may correspond to steps 7 and 8.

[0218] In one option, the configuration of the fourth conditional LTM execution condition may be provided within the lower layer configuration of the first conditional LTM candidate cell, which is to be applied by the UE when the UE executes a conditional LTM cell switch to the first conditional LTM candidate cell.

[0219] - Thus, when the C-DU receives the request for configuring the first cell (e.g. the UE CONTEXT SETUP REQUEST, as indicated above) the C-DU generates the conditional LTM execution condition associated with the second conditional LTM candidate cell and includes it within the lower layer configuration of the first conditional LTM candidate cell which is provided to the CU, and is to be provided to the UE.

[0220] - And, when the C-DU receives the UE CONTEXT MODIFICATION REQUEST, as indicated above, the C-DU generates the conditional LTM execution condition associated with the second conditional LTM candidate cell and includes it within an updated version of the lower layer configuration of the first conditional LTM candidate cell (which was previously provided in the UE CONTEXT SETUP RESPONSE), so that the updated version of the lower layer configuration of the first conditional LTM candidate cell is now included in a UE CONTEXT MODIFICATION RESPONSE to the CU, to be provided to the UE. Figure 11 A and Figure 1 IB illustrates an example signaling flow - inter-gNB-DU (intra-CU) - for the configuration of conditional LTM execution conditions described immediately above. In the figure, the bold text represents new steps according to the method in the signaling flow between UE, source gNB-DU, and Candidate gNB-DU and gNB-CU.

[0221] In view of the various examples and details presented above, it will be appreciated that Figure 12 is a process flow diagram illustrating steps of an example method, according to the techniques described herein, as implemented by the UE. Note that the illustrated method, as described in detail below, is intended to be a generalization of and to encompass the various UE- based techniques described above. Thus, where the terminology used in Figure 12 and below differs somewhat from that used above, the former should be understood to be synonymous with or to encompass the latter, unless the context for either clearly indicates otherwise.

[0222] As shown at block 1210, this example method comprises the step of receiving, from the wireless network, conditional LTM configuration information comprising a first conditional LTM execution condition, associated to a first LTM candidate cell configuration, and a second conditional LTM execution condition, associated to a second LTM candidate cell configuration. Here, the term “conditional LTM configuration information” is used to refer to the included elements more generally - as discussed elsewhere herein, these elements may form part of one or more “configurations,” e.g., conditional LTM candidate cell configurations, or may be provided separately, using one or several messages. In some embodiments or instances, the conditional LTM configuration information may be included in one or more RRCReconfiguration messages. In some embodiments or instances, the second conditional LTM execution condition is part of the first LTM candidate cell configuration.

[0223] As shown at block 1230, the method further comprises executing a first LTM cell switch procedure to a first candidate cell, according to the first LTM candidate cell configuration, in response to fulfilment of the first conditional LTM execution condition. Note that this implies an evaluation of the first conditional LTM execution condition and a determination that it has been fulfilled. This is shown at block 1220. As shown at block 1240, the method still further comprises, in response to executing the first LTM cell switch procedure to the first candidate cell, evaluating the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a second candidate cell, corresponding to the second LTM candidate cell configuration.

[0224] In some embodiments or instances, the method further comprises prior to the executing step shown at block 1230, also evaluating a third conditional LTM execution condition, associated to the second LTM candidate cell configuration or to another LTM candidate cell configuration, to determine whether to instead perform the first LTM cell switch procedure to the second candidate cell or another candidate cell. This is shown at block 1225.

[0225] In some embodiments or instances, the method further comprises, responsive to executing the first LTM cell switch procedure to the first candidate cell, evaluating a fourth conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a third candidate cell, corresponding to a third LTM candidate cell configuration, along with said evaluating the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to the second candidate cell. This is shown at block 1245.

[0226] In some embodiments or instances, the first conditional LTM execution condition is associated to the first LTM candidate cell configuration by a measurement configuration identifier for the first LTM candidate cell and the second conditional LTM execution condition is associated to the second LTM candidate cell configuration by a measurement configuration identifier for the second LTM candidate cell.

[0227] Other variations of the method shown in Figure 12 follow directly from any of the several UE- based examples described earlier in this document.

[0228] Figure 13 is a process flow diagram illustrating steps of an example method, according to the techniques described herein, as implemented by a network node. While much of the explanation of the various network-side techniques discussed above refers to steps carried out by a DU or to messages exchanged between DUs, the techniques described herein are more generally applicable to network nodes of any sort that are controlling one or more cells. Thus, the term “network node” is used below and in Figure 13 to describe a network node, such as a DU or gNB, that controls at least one respective cell.

[0229] As was the case with Figure 12, the method shown in Figure 13, as described in detail below, is intended to be a generalization of and to encompass the various network-based techniques described above. Thus, where the terminology used in Figure 13 and below differs somewhat from that used above, the former should be understood to be synonymous with or to encompass the latter, unless the context for either clearly indicates otherwise.

[0230] As shown at block 1310, the illustrated method, which is carried out by a first network node, includes the step of receiving, from a second network node, a request to configure a first cell, controlled by the first network node, as a first conditional LTM candidate cell, the request comprising an indication of a second conditional LTM candidate cell. As shown at block 1320, the method further includes sending a message to the second network node, in response to the request, the message including a lower layer configuration for the first conditional LTM candidate cell and further including a conditional LTM execution condition associated to the second conditional LTM candidate cell, for use by a UE after performing a conditional LTM cell switch procedure to the first conditional LTM candidate cell.

[0231] In some embodiments or instances, the request to configure the first cell is a CONTEXT SETUP REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT SETUP RESPONSE. In other embodiments or instances, the request to configure the first cell is a UE CONTEXT MODIFICATION REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT MODIFICATION RESPONSE.

[0232] In some embodiments or instances, the conditional LTM execution condition is associated to the second conditional LTM candidate cell by a measurement configuration identifier for the second conditional LTM candidate cell.

[0233] Other variations of the method shown in Figure 13 follow directly from any of the several network-node-based examples described earlier in this document.

[0234] Although various embodiments are described above in terms of methods, techniques, and / or procedures, the person of ordinary skill will readily comprehend that such methods, techniques, and / or procedures can be embodied by various combinations of hardware and software in various systems, communication devices, computing devices, control devices, apparatuses, non-transitory computer-readable media, computer program products, etc.

[0235] Figure 14 shows an example of a communication system 1400 in accordance with some embodiments. In this example, the communication system 1400 includes a telecommunication network 1402 that includes an access network 1404 (e.g., RAN) and a core network 1406, which includes one or more core network nodes 1408. The access network 1404 includes one or more access network nodes, such as network nodes 1410a-b (one or more of which may be generally referred to as network nodes 1410), or any other similar 3 GPP access node or non- 3 GPP access point. The network nodes 1410 facilitate direct or indirect connection of UEs, such as by connecting UEs 1412a-d (one or more of which may be generally referred to as UEs 1412) to the core network 1406 over one or more wireless connections. 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 1400 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 1400 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0236] UEs 1412 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 1410 and other communication devices. Similarly, the network nodes 1410 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs 1412 and / or with other network nodes or equipment in the telecommunication network 1402 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 1402.

[0237] In the depicted example, the core network 1406 connects the network nodes 1410 to one or more hosts, such as host 1416. 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 1406 includes one more core network nodes (e.g., core network node 1408) 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 1408. 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).

[0238] The host 1416 may be under the ownership or control of a service provider other than an operator or provider of the access network 1404 and / or the telecommunication network 1402, and may be operated by the service provider or on behalf of the service provider. The host 1416 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as 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.

[0239] As a whole, the communication system 1400 of Figure 14 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.

[0240] In some examples, the telecommunication network 1402 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 1402 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1402. For example, the telecommunications network 1402 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.

[0241] In some examples, the UEs 1412 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 1404 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1404. 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).

[0242] In the example, the hub 1414 communicates with the access network 1404 to facilitate indirect communication between one or more UEs (e.g., UE 1412c and / or 1412d) and network nodes (e.g., network node 1410b). In some examples, the hub 1414 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 1414 may be a broadband router enabling access to the core network 1406 for the UEs. As another example, the hub 1414 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 1410, or by executable code, script, process, or other instructions in the hub 1414. As another example, the hub 1414 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 1414 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 1414 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1414 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 1414 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy loT devices.

[0243] The hub 1414 may have a constant / persistent or intermittent connection to the network node 1410b. The hub 1414 may also allow for a different communication scheme and / or schedule between the hub 1414 and UEs (e.g., UE 1412c and / or 1412d), and between the hub 1414 and the core network 1406. In other examples, the hub 1414 is connected to the core network 1406 and / or one or more UEs via a wired connection. Moreover, the hub 1414 may be configured to connect to an M2M service provider over the access network 1404 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 1410 while still connected via the hub 1414 via a wired or wireless connection. In some embodiments, the hub 1414 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 1410b. In other embodiments, the hub 1414 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1410b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0244] Figure 15 shows a UE 1500 in accordance with some embodiments. 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 cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptopmounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle- mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by 3 GPP, including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0245] A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-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).

[0246] UE 1500 includes processing circuitry 1502 that is operatively coupled via a bus 1504 to an input / output interface 1506, a power source 1508, a memory 1510, a communication interface 1512, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 15. 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.

[0247] The processing circuitry 1502 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 1510. The processing circuitry 1502 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 1502 may include multiple central processing units (CPUs).

[0248] In the example, the input / output interface 1506 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 1500. 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.

[0249] In some embodiments, the power source 1508 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 1508 may further include power circuitry for delivering power from the power source 1508 itself, and / or an external power source, to the various parts of the UE 1500 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1508. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1508 to make the power suitable for the respective components of the UE 1500 to which power is supplied.

[0250] The memory 1510 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 1510 includes one or more application programs 1514, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1516. The memory 1510 may store, for use by the UE 1500, any of a variety of various operating systems or combinations of operating systems.

[0251] The memory 1510 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 data storage (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 1510 may allow the UE 1500 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 1510, which may be or comprise a device-readable storage medium.

[0252] The processing circuitry 1502 may be configured to communicate with an access network or other network using the communication interface 1512. The communication interface 1512 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1522. The communication interface 1512 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 1518 and / or a receiver 1520 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 1518 and receiver 1520 may be coupled to one or more antennas (e.g., antenna 1522) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0253] In the illustrated embodiment, communication functions of the communication interface 1512 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 / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0254] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1512, 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., an alert is sent when moisture is detected), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0255] 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 to a robotic arm performing a medical procedure according to the received input.

[0256] 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 a device which is or which is 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 of the intended application of the loT device in addition to other components as described in relation to the UE 1500 shown in Figure 15.

[0257] 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 such monitoring 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.

[0258] 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.

[0259] Figure 16 shows a network node 1600 in accordance with some embodiments. Examples of network nodes include, but are not limited to, access points (e.g., radio access points) and base stations (e.g., radio base stations, Node Bs, eNBs, and gNBs).

[0260] 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 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).

[0261] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such 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).

[0262] The network node 1600 includes a processing circuitry 1602, a memory 1604, a communication interface 1606, and a power source 1608. The network node 1600 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 1600 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 1600 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1604 for different RATs) and some components may be reused (e.g., a same antenna 1610 may be shared by different RATs). The network node 1600 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1600, 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 1600.

[0263] The processing circuitry 1602 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 1600 components, such as the memory 1604, to provide network node 1600 functionality.

[0264] In some embodiments, the processing circuitry 1602 includes a system on a chip (SOC). In some embodiments, the processing circuitry 1602 includes one or more of radio frequency (RF) transceiver circuitry 1612 and baseband processing circuitry 1614. In some embodiments, the radio frequency (RF) transceiver circuitry 1612 and the baseband processing circuitry 1614 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 1612 and baseband processing circuitry 1614 may be on the same chip or set of chips, boards, or units.

[0265] The memory 1604 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 1602. The memory 1604 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 (collectively denoted computer program product 1604a) capable of being executed by the processing circuitry 1602 and utilized by the network node 1600. The memory 1604 may be used to store any calculations made by the processing circuitry 1602 and / or any data received via the communication interface 1606. In some embodiments, the processing circuitry 1602 and memory 1604 is integrated.

[0266] The communication interface 1606 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 1606 comprises port(s) / terminal(s) 1616 to send and receive data, for example to and from a network over a wired connection. The communication interface 1606 also includes radio front-end circuitry 1618 that may be coupled to, or in certain embodiments a part of, the antenna 1610. Radio front-end circuitry 1618 comprises filters 1620 and amplifiers 1622. The radio front-end circuitry 1618 may be connected to an antenna 1610 and processing circuitry 1602. The radio front-end circuitry may be configured to condition signals communicated between antenna 1610 and processing circuitry 1602. The radio front-end circuitry 1618 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 1618 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1620 and / or amplifiers 1622. The radio signal may then be transmitted via the antenna 1610. Similarly, when receiving data, the antenna 1610 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1618. The digital data may be passed to the processing circuitry 1602. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0267] In certain alternative embodiments, the network node 1600 does not include separate radio frontend circuitry 1618, instead, the processing circuitry 1602 includes radio front-end circuitry and is connected to the antenna 1610. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1612 is part of the communication interface 1606. In still other embodiments, the communication interface 1606 includes one or more ports or terminals 1616, the radio front-end circuitry 1618, and the RF transceiver circuitry 1612, as part of a radio unit (not shown), and the communication interface 1606 communicates with the baseband processing circuitry 1614, which is part of a digital unit (not shown). The antenna 1610 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 1610 may be coupled to the radio front-end circuitry 1618 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 1610 is separate from the network node 1600 and connectable to the network node 1600 through an interface or port.

[0268] The antenna 1610, communication interface 1606, and / or the processing circuitry 1602 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 1610, the communication interface 1606, and / or the processing circuitry 1602 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.

[0269] The power source 1608 provides power to the various components of network node 1600 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 1608 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1600 with power for performing the functionality described herein. For example, the network node 1600 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 supplies power to power circuitry of the power source 1608. As a further example, the power source 1608 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.

[0270] Embodiments of the network node 1600 may include additional components beyond those shown in Figure 16 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 1600 may include user interface equipment to allow input of information into the network node 1600 and to allow output of information from the network node 1600. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1600.

[0271] Figure 17 is a block diagram illustrating a virtualization environment 1700 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 1700 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.

[0272] Applications 1702 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1700 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0273] Hardware 1704 includes processing circuitry, memory that stores software and / or instructions (collectively denoted computer program product 1704a) 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 1706 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1708a-b (one or more of which may be generally referred to as VMs 1708), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. The virtualization layer 1706 may present a virtual operating platform that appears like networking hardware to VMs 1708.

[0274] VMs 1708 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1706. Different embodiments of the instance of a virtual appliance 1702 may be implemented on one or more of VMs 1708, 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.

[0275] In the context of NFV, a VM 1708 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each VM 1708, and that part of hardware 1704 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 1708 on top of the hardware 1704 and corresponds to the application 1702.

[0276] Hardware 1704 may be implemented in a standalone network node with generic or specific components. Hardware 1704 may implement some functions via virtualization. Alternatively, hardware 1704 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 1710, which, among others, oversees lifecycle management of applications 1702. In some embodiments, hardware 1704 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 1712 which may alternatively be used for communication between hardware nodes and radio units.

[0277] The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

[0278] The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and / or electronic devices and can include, for example, electrical and / or electronic circuitry, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and / or displaying functions, and so on, as such as those that are described herein.

[0279] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

[0280] As described herein, device and / or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and / or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person.

[0281] Furthermore, functions described herein as being performed by a wireless device or a network node may be distributed over a plurality of wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network node and wireless device described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.

[0282] In addition, certain terms used in the present disclosure, including the specification, drawings and embodiments thereof, can be used synonymously in certain instances, including, but not limited to, e.g., data and information. It should be understood that, while these words and / or other words that can be synonymous to one another, can be used synonymously herein, that there can be instances when such words can be intended to not be used synonymously. Further, to the extent that the prior art knowledge has not been explicitly incorporated by reference herein above, it is explicitly incorporated herein in its entirety. All publications referenced are incorporated herein by reference in their entireties.

[0283] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0284] In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., “data” and “information”). It should be understood, that although these terms (and / or other terms that can be synonymous to one another) can be used synonymously herein, there can be instances when such words can be intended to not be used synonymously.

[0285] The techniques and apparatus described herein include, but are not limited to, the following enumerated examples. Note that the terms “first,” “second,” “third,” etc., as used in the following are used merely to distinguish one item from another similar item. These terms should be interpreted within the context of these example embodiments, as they are not necessarily consistent with uses of “first,” “second,” “third,” etc., elsewhere in this document.

[0286] Al . A method, for a user equipment, UE, for conditional Ll / L2-triggered mobility, LTM, in a wireless network, the method comprising: receiving, from the wireless network, conditional LTM configuration information comprising a first conditional LTM execution condition, associated to a first LTM candidate cell configuration, and a second conditional LTM execution condition, associated to a second LTM candidate cell configuration; executing a first LTM cell switch procedure to a first candidate cell, according to the first LTM candidate cell configuration, in response to fulfilment of the first conditional LTM execution condition; and, responsive to executing the first LTM cell switch procedure to the first candidate cell, evaluating the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a second candidate cell, corresponding to the second LTM candidate cell configuration. A2. The method of embodiment Al, wherein the conditional LTM configuration information is included in an RRCReconfiguration message.

[0287] A3. The method of embodiment Al or A2, wherein the method comprises, prior to said executing, evaluating the first conditional LTM execution condition to determine whether to perform the first LTM cell switch procedure to the first candidate cell and evaluating a third conditional LTM execution condition to determine whether to instead perform the first LTM cell switch procedure to the second candidate cell or another candidate cell.

[0288] A4. The method of any one of embodiments Al -A3, wherein the method further comprises, responsive to executing the first LTM cell switch procedure to the first candidate cell, evaluating a fourth conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a third candidate cell, corresponding to a third LTM candidate cell configuration, along with said evaluating the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a second candidate cell.

[0289] A5. The method of any of embodiments A1-A4, wherein the second conditional LTM execution condition is part of the first LTM candidate cell configuration.

[0290] A6. The method of any one of embodiments A1-A5, wherein the first conditional LTM execution condition is associated to the first LTM candidate cell configuration by a measurement configuration identifier for the first LTM candidate cell and the second conditional LTM execution condition is associated to the second LTM candidate cell configuration by a measurement configuration identifier for the second LTM candidate cell.

[0291] BL A method, for a first network node in a wireless network, for supporting Ll / L2-triggered mobility, LTM, of user equipment, UEs, in the wireless network, the method comprising: receiving, from a second network node, a request to configure a first cell, controlled by the first network node, as a first conditional LTM candidate cell, the request comprising an indication of a second conditional LTM candidate cell; and, in response to the request, sending a message including a lower layer configuration for the first conditional LTM candidate cell and further including a conditional LTM execution condition associated to the second conditional LTM candidate cell, for use by a UE after performing a conditional LTM cell switch procedure to the first conditional LTM candidate cell.

[0292] B2. The method of embodiment Bl, wherein the request to configure the first cell is a CONTEXT SETUP REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT SETUP RESPONSE.

[0293] B3. The method of embodiment Bl, wherein the request to configure the first cell is a UE CONTEXT MODIFICATION REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT MODIFICATION RESPONSE.

[0294] B4. The method of any one of embodiments B1-B3, wherein the conditional LTM execution condition is associated to the second conditional LTM candidate cell by a measurement configuration identifier for the second conditional LTM candidate cell.

[0295] CL A user equipment (UE) adapted to support conditional Ll / L2-triggered mobility (LTM) in a wireless network, the UE comprising: communication interface circuitry configured to communicate with the wireless network via at least one serving cell; and processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and communication interface circuitry are configured to perform operations corresponding to any of the methods of embodiments A1-A6.

[0296] C2. A user equipment (UE) adapted to support conditional Ll / L2-triggered mobility (LTM) in a wireless network, he UE being further adapted to perform operations corresponding to any of the methods of embodiments A1-A6.

[0297] C3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a user equipment (UE), configure the UE to perform operations corresponding to any of the methods of embodiments A1-A6.

[0298] C4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a user equipment (UE), configure the UE to perform operations corresponding to any of the methods of embodiments A1-A6. DI. A network node adapted to support conditional Ll / L2-triggered mobility (LTM) of user equipment (UE) in a wireless network, the network node comprising: communication interface circuitry configured to communicate with UEs via at least one serving cell; and processing circuitry operably coupled to the communication interface circuitry, wherein the processing circuitry and communication interface circuitry are configured to perform operations corresponding to any of the methods of embodiments B1-B4.

[0299] D2. A network node adapted to support conditional Ll / L2-triggered mobility (LTM) of user equipment (UE) in a wireless network, the network node being further configured to perform operations corresponding to any of the methods of embodiments B1-B4.

[0300] D3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a network node, configure the RAN node to perform operations corresponding to any of the methods of embodiments B1-B4.

[0301] D4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a network node, configure the RAN node to perform operations corresponding to any of the methods of embodiments B1-B4.

[0302] Below, an example of how the techniques described above might be implemented in 3GPP specification documents is provided. The material shown in bold is material that may be added to currently existing specifications. Note that the below shows mainly the communication with the C-DU, and not with the C-DU*, except when that is mentioned in some steps. The main nodes for subsequent conditional LTM actions are the UE and the Candidate DU (e.g. C-DU or C-DU*), which perform actions to be prepared when becomes a new S-DU. - begin example -

[0303] 1. The UE sends a MeasurementReport message (L3 measurement result) to the source gNB-DU (or simply S-DU) containing measurements of neighbouring cells. The source gNB-DU (S-DU) sends an UL RRC MESSAGE TRANSFER message conveying the received MeasurementReport message to the gNB-CU.

[0304] 2. The gNB-CU (or simply CU, as in the figure above) determines to initiate conditional LTM configuration.

[0305] 3. The gNB-CU sends a UE CONTEXT SETUP REQUEST message including an indication of conditional LTM to the candidate gNB-DU(s) (C-DU) for a first cell containing information about the first cell e.g. one target candidate cell ID for the cell being requested as a candidate, the LTM configuration ID of the candidate cell, etc.

[0306] In one option, for subsequent conditional LTM, the gNB-CU (e.g. CU) may include in the UE CONTEXT SETUP REQUEST an indication of at least a second cell (indication of second conditional LTM candidate cell) which the CU also wants to configure as a conditional LTM candidate cell (e.g. from a C-DU*) for the UE (for example, the indication of the second conditional LTM candidate cell may be included in a CSI resource configuration). The purpose is to indicate that in case the UE accesses the first cell in an execution of a conditional LTM, the second cell becomes a candidate cell for conditional LTM, so that while the UE is in the C-DU, the UE needs conditional LTM execution conditions to evaluate for the second cell.

[0307] In another option, the CU does not need to send information for subsequent conditional LTM to the C-DU or the C-DU* in step 3. Instead, the CU may request conditional LTM candidates in steps 3 and 4 for different candidate DU(s), and, once the CU knows which conditional LTM candidates were accepted, the CU may trigger in step 7 the UE CONTEXT MODIFICATION REQUEST, including information about the accepted cells (e.g. indication of second conditional LTM candidate cell), so that a C-DU may provide the conditional LTM execution condition(s) for subsequent conditional LTM.

[0308] In another option, the DU sends information for subsequent LTM to the C-DU or the C-DU* in step 3. However, after step 4, once the CU knows which conditional LTM candidates were accepted, the CU may trigger in step 7 the UE CONTEXT MODIFICATION REQUEST, including information about the accepted cells, so that a C-DU may provide an update of the conditional LTM execution condition(s) for subsequent conditional LTM e.g. by removing conditional LTM execution condition(s) for cells which were not accepted.

[0309] In one option, when the indication of second conditional LTM candidate cell) is received the C-DU also receives an associated measurement configuration identifier (e.g. LTM CSI reporting configuration identifier) which is used to configure the fourth conditional LTM execution condition in the configuration of the first LTM candidate cell. If the candidate gNB-DU accepts the request of LTM configuration, it responds with a UE CONTEXT SETUP RESPONSE message including the generated lower layer RRC configurations for the accepted target candidate cell i.e. for the first cell.

[0310] For subsequent conditional LTM, e.g. when the gNB-CU may include in the UE CONTEXT SETUP REQUEST an indication of at least a second cell, the C-DU determines a conditional LTM execution condition associated to the second cell (e.g. fourth conditional LTM execution condition) and includes in the UE CONTEXT SETUP RESPONSE, with an association with the second LTM candidate cell. In one option, the fourth conditional LTM execution condition associated to the second cell is included in the generated lower layer RRC configurations for the accepted target candidate cell i.e. for the first conditional LTM candidate cell. The reason is that when the UE applies the generated lower layer RRC configurations for the first cell the UE evaluates the conditional LTM execution condition associated to the second cell.

[0311] Steps 3 and 4, when applied for subsequent LTM are opportunistic steps since the CU indicates to the C-DU a second cell of another C-DU* which the CU wants to configured as a conditional LTM candidate cell, before the C-DU* has actually accepted the request from the CU. Similarly, the CU indicates to the C-DU* a first cell of another C-DU which the CU wants to configured as a conditional LTM candidate cell, before the C-DU has actually accepted the request from the CU. Thus, the CU assumes that both C-DU and C-DU* are likely to accept the requests, so the CU obtains the conditional LTM execution condition associated to the second cell and the conditional LTM execution condition associated to the first cell as soon as possible, for subsequent LTM.

[0312] The UE does not evaluate the conditional LTM execution condition associated to the second cell and the conditional LTM execution condition associated to the first cell while the UE is connected to the S-DU; these are to be used only in subsequent LTM i.e. after the UE leaves the S-DU and switches to the C-DU or the C-DU*.

[0313] NOTE 1: The CU-initiated UE Context Modification procedure may be initiated for preparing candidate cells in the source gNB-DU as specified in step 3 and 4 in 8.2.1.4 Intra-gNB-DU LTM.

[0314] 5. The gNB-CU sends a UE CONTEXT MODIFICATION REQUEST message to the source gNB-DU including the information related to early sync and the LTM configuration IDs for the accepted target candidate cell(s) in other gNB-DU(s).

[0315] At this step, the CU informs the S-DU of the accepted LTM candidate cell(s) for conditional LTM e.g. indication of the first cell and indication of the second cell. In one option, these are informed in the form of a CSI resource configuration for LTM e.g. as a list of cell(s) and / or LTM candidate ID(s). That enables the S-DU to determine conditional LTM execution conditions to be used by the UE while the UE is in the S-DU, for the conditional LTM candidate cells being configured to the UE.

[0316] 6. The source gNB-DU responds with a UE CONTEXT MODIFICATION RESPONSE message which includes an updated lower layer configuration, e.g., containing the updated CSI report configuration of the source cell.

[0317] The S-DU determines the conditional LTM execution conditions to be used by the UE while the UE is in the S-DU, for the conditional LTM candidate cells being configured to the UE, as follows: o i) a conditional LTM execution condition for the first cell, to be evaluated while the UE is in the S-DU; o ii) a conditional LTM execution condition for the second cell, to be evaluated while the UE is in the S-DU;

[0318] These are the conditional LTM execution condition(s) the UE evaluates while connected to the S-DU, for evaluating the first and the second cells e.g. for evaluating whether any of these cells become an offset better than the LTM candidate cell.

[0319] In one option, each conditional LTM execution condition is configured as part of the updated lower layer configuration. For example, the conditional LTM execution condition may be configured as part of the CSI measurement configuration for LTM e.g. in the CSI LTM reporting configuration. In that case the conditional LTM execution condition has an associated identifier (e.g. reporting configuration identifier). The S-DU also provides in the UE CONTEXT MODIFICATION RESPONSE a mapping between the associated identifier and the conditional LTM candidate cell for which the conditional LTM execution condition is applicable.

[0320] 7. The gNB-CU may send a UE CONTEXT MODIFICATION REQUEST message to the candidate gNB-DU(s) containing the information for subsequent LTM or for updating the configurations of candidate cells. The gNB-CU may also provide the lower layer part of the reference configuration to the candidate gNB-DU(s).

[0321] In one option, the DU does not need to send information for subsequent conditional LTM to the C-DU or the C-DU* in step 3. Instead, the CU may request conditional LTM candidates, and, once the CU knows which conditional LTM candidates were accepted, the CU may trigger in step 7 the UE CONTEXT MODIFICATION REQUEST, including information about the accepted cells, so that a C-DU may provide the conditional LTM execution condition(s) for subsequent conditional LTM.

[0322] In another option, the DU sends information for subsequent LTM to the C-DU or the C- DU* in step 3. However, after step 3, once the CU knows which conditional LTM candidates were accepted, the CU may trigger in step 7 the UE CONTEXT MODIFICATION REQUEST, including information about the accepted cells, so that a C-DU may provide an update of the conditional LTM execution condition(s) for subsequent conditional LTM e.g. by removing conditional LTM execution condition(s) for cells which were not accepted.

[0323] In one option, when the indication of second conditional LTM candidate cell) is received the C-DU also receives an associated measurement configuration identifier (e.g. LTM CSI reporting configuration identifier) which is used to configure the fourth conditional LTM execution condition in the configuration of the first LTM candidate cell.

[0324] 8. The candidate gNB-DU responds with a UE CONTEXT MODIFICATION RESPONSE message including the updated lower layer configuration^. g., the updated CSI report configuration).

[0325] NOTE 2: Step 7 may also be triggered after step 19, or after step 22 by implementation for subsequent LTM.

[0326] 9. The gNB-CU sends a DL RRC MESSAGE TRANSFER message to the source gNB-DU, which includes the generated RRCReconfiguration message with the LTM configuration.

[0327] 10. The source gNB-DU forwards the received RRCReconfiguration message to the UE.

[0328] The RRC Reconfiguration which the UE receives contains the configuration(s) needed for conditional LTM while the UE is connected to the S-DU i.e. conditional LTM execution condition for the first cell and the RRC configuration of the first cell; and the conditional LTM execution condition for the second cell and the RRC configuration of the second cell, wherein the conditional LTM execution condition for the first and second cells were determined by the S-DU. These are the execution conditions to be evaluated by the UE when the UE receives the message.

[0329] The RRC Reconfiguration also includes executions conditions for the first and for the second cells to be evaluated later e.g. when the UE connects to the first cell and / or second cell and / or C-DU and / or C-DU*. In one option, the conditional LTM execution condition for the first cell is include in the RRC configuration for the second cell and is evaluated when the UE applies the RRC configuration for the second cell i.e. when the UE executes LTM cell switch to that second cell.

[0330] In one option, the conditional LTM execution condition for the second cell is include in the RRC configuration for the first cell and is evaluated when the UE applies the RRC configuration for the first cell i.e. when the UE executes LTM cell switch to that first cell.

[0331] 11. The UE responds to the source gNB-DU with an RRCReconfigurationComplete message.

[0332] 12. The source gNB-DU forwards the RRCReconfigurationComplete message to the gNB- CU via an UL RRC MESSAGE TRANSFER message. end example Some Abbreviations:

[0333] CHO Conditional Handover

[0334] CPAC Conditional PSCell Addition or Change

[0335] CPA Conditional PSCell Addition

[0336] CPC Conditional PSCell Change

[0337] CSI Channel State Information

[0338] CSI-RS Channel State Information - Reference Signal

[0339] C-DU Candidate DU

[0340] CU Central Unit

[0341] DL Downlink

[0342] DU Distributed Unit gNB Base station supporting the NR air interface gNB-CU gNB Central Unit gNB-DU gNB Distributed Unit

[0343] IE Information Element

[0344] LI Layer 1

[0345] L2 Layer 2

[0346] L3 Layer 3

[0347] LTM L1 / L2 Triggered Mobility

[0348] MAC Medium Access Control

[0349] MAC CE MAC Control element

[0350] MN Master Node

[0351] PCell Primary Cell

[0352] PSCell Primary SCG Cell

[0353] PUCCH Physical Uplink Control Channel

[0354] PUSCH Physical Uplink Control Channel

[0355] QCL Quasi -Co-Locati on

[0356] RACH Random Access CHannel

[0357] RRC Radio Resource Control

[0358] RS Reference Signal

[0359] RSRP Reference Signal Received Power

[0360] RSRQ Reference Signal Received Quality

[0361] S-CU Serving CU

[0362] S-DU Serving DU

[0363] SCPAC Subsequent Conditional PSCell Addition or Change SCG Secondary Cell Group

[0364] SINR Signal -to-Interference-plus-N oi se Ratio

[0365] SpCell Special Cell (PCell of the MCG or the PSCell of the SCG) SSB Synchronization Signal Block SS-RSRP Synchronization Signal RSRP

[0366] SS-RSRQ Synchronization Signal RSRQ SS-SINR Synchronization Signal SINR TCI Transmission Configuration Indication UCI Uplink Control Information UE User Equipment

[0367] UL Uplink

Claims

CLAIMS1. A method, for a user equipment, UE, for conditional Ll / L2-triggered mobility, LTM, in a wireless network, the method comprising: receiving (1210), from the wireless network, conditional LTM configuration information comprising a first conditional LTM execution condition, associated to a first LTM candidate cell configuration, and a second conditional LTM execution condition, associated to a second LTM candidate cell configuration; executing (1230) a first LTM cell switch procedure to a first candidate cell, according to the first LTM candidate cell configuration, in response to fulfilment of the first conditional LTM execution condition; and, responsive to executing the first LTM cell switch procedure to the first candidate cell, evaluating (1240) the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a second candidate cell, corresponding to the second LTM candidate cell configuration.

2. The method of claim 1, wherein the conditional LTM configuration information is included in an RRCReconfiguration message.

3. The method of claim 1 or 2, wherein the method comprises, prior to said executing (1230), evaluating (1220) the first conditional LTM execution condition to determine whether to perform the first LTM cell switch procedure to the first candidate cell and evaluating (1225) a third conditional LTM execution condition to determine whether to instead perform the first LTM cell switch procedure to the second candidate cell or another candidate cell.

4. The method of any one of claims 1-3, wherein the method further comprises, responsive to executing (1230) the first LTM cell switch procedure to the first candidate cell, evaluating (1245) a fourth conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a third candidate cell, corresponding to a third LTM candidate cell configuration, along with said evaluating (1240) the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to the second candidate cell.

5. The method of any of claims 1-4, wherein the second conditional LTM execution condition is part of the first LTM candidate cell configuration.

6. The method of any one of claims 1-5, wherein the first conditional LTM execution condition is associated to the first LTM candidate cell configuration by a measurement configuration identifier for the first LTM candidate cell and the second conditional LTM execution condition is associated to the second LTM candidate cell configuration by a measurement configuration identifier for the second LTM candidate cell.

7. A method, for a first network node in a wireless network, for supporting Ll / L2-triggered mobility, LTM, of user equipment, UEs, in the wireless network, the method comprising: receiving (1310), from a second network node, a request to configure a first cell, controlled by the first network node, as a first conditional LTM candidate cell, the request comprising an indication of a second conditional LTM candidate cell; and, in response to the request, sending (1320), to the second network node, a message including a lower layer configuration for the first conditional LTM candidate cell and further including a conditional LTM execution condition associated to the second conditional LTM candidate cell, for use by a UE after performing a conditional LTM cell switch procedure to the first conditional LTM candidate cell.

8. The method of claim 7, wherein the request to configure the first cell is a CONTEXT SETUP REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT SETUP RESPONSE.

9. The method of claim 7, wherein the request to configure the first cell is a UE CONTEXT MODIFICATION REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT MODIFICATION RESPONSE.

10. The method of any one of claims 7-9, wherein the conditional LTM execution condition is associated to the second conditional LTM candidate cell by a measurement configuration identifier for the second conditional LTM candidate cell.I L A user equipment, UE (1500), for supporting conditional Ll / L2-triggered mobility, LTM, in a wireless network, the UE (1500) being adapted to: receive, from the wireless network, conditional LTM configuration information comprising a first conditional LTM execution condition, associated to a firstLTM candidate cell configuration, and a second conditional LTM execution condition, associated to a second LTM candidate cell configuration; execute a first LTM cell switch procedure to a first candidate cell, according to the first LTM candidate cell configuration, in response to fulfilment of the first conditional LTM execution condition; and, responsive to executing the first LTM cell switch procedure to the first candidate cell, evaluate the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a second candidate cell, corresponding to the second LTM candidate cell configuration.

12. The UE (1500) of claim 11, being further adapted to carry out a method according to any one of claims 2-6.

13. A user equipment, UE (1500), configured to support conditional Ll / L2-triggered mobility, LTM, in a wireless network, the UE (1500) comprising: communication interface circuitry (1512) configured to communicate with the wireless network via at least one serving cell; and processing circuitry (1502) operably coupled to the communication interface circuitry (1512), wherein the processing circuitry (1502) and communication interface circuitry (1512) are configured to: receive, from the wireless network, conditional LTM configuration information comprising a first conditional LTM execution condition, associated to a first LTM candidate cell configuration, and a second conditional LTM execution condition, associated to a second LTM candidate cell configuration; execute a first LTM cell switch procedure to a first candidate cell, according to the first LTM candidate cell configuration, in response to fulfilment of the first conditional LTM execution condition; and, responsive to executing the first LTM cell switch procedure to the first candidate cell, evaluate the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a second candidate cell, corresponding to the second LTM candidate cell configuration.

14. The UE (1500) of claim 13, wherein the conditional LTM configuration information is included in an RRCReconfiguration message.

15. The UE (1500) of claim 13 or 14, wherein the processing circuitry (1502) is configured to, prior to executing the first LTM cell switch behavior, evaluate the first conditional LTM execution condition to determine whether to perform the first LTM cell switch procedure to the first candidate cell and evaluate a third conditional LTM execution condition to determine whether to instead perform the first LTM cell switch procedure to the second candidate cell or another candidate cell.

16. The UE (1500) of any one of claims 13-15, wherein the processing circuitry (1502) is further configured to, responsive to executing the first LTM cell switch procedure to the first candidate cell, evaluate a fourth conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to a third candidate cell, corresponding to a third LTM candidate cell configuration, along with evaluating the second conditional LTM execution condition to determine whether to perform a second LTM cell switch procedure to the second candidate cell.

17. The UE (1500) of any of claims 13-16, wherein the second conditional LTM execution condition is part of the first LTM candidate cell configuration.

18. The UE (1500) of any one of claims 13-17, wherein the first conditional LTM execution condition is associated to the first LTM candidate cell configuration by a measurement configuration identifier for the first LTM candidate cell and the second conditional LTM execution condition is associated to the second LTM candidate cell configuration by a measurement configuration identifier for the second LTM candidate cell.

19. A first network node (1600) for supporting conditional Ll / L2-triggered mobility, LTM, of user equipment, UE, in a wireless network, the first network node (1600) being adapted to: receive, from a second network node, a request to configure a first cell, controlled by the first network node, as a first conditional LTM candidate cell, the request comprising an indication of a second conditional LTM candidate cell; and, in response to the request, send, to the second network node, a message including a lower layer configuration for the first conditional LTM candidate cell and further including a conditional LTM execution condition associated to thesecond conditional LTM candidate cell, for use by a UE after performing a conditional LTM cell switch procedure to the first conditional LTM candidate cell.

20. The first network node (1600) of claim 19, being further adapted to carry out a method according to any one of claims 8-10.

21. A first network node (1600) configured to support conditional Ll / L2-triggered mobility, LTM, of user equipment, UE, in a wireless network, the first network node (1600) comprising: communication interface circuitry (1606) configured to communicate with a second network node; and processing circuitry (1602) operably coupled to the communication interface circuitry (1606), wherein the processing circuitry (1602) and communication interface circuitry (1606) are configured to receive, from the second network node, a request to configure a first cell, controlled by the first network node, as a first conditional LTM candidate cell, the request comprising an indication of a second conditional LTM candidate cell, and, in response to the request, send, to the second network node, a message including a lower layer configuration for the first conditional LTM candidate cell and further including a conditional LTM execution condition associated to the second conditional LTM candidate cell, for use by a UE after performing a conditional LTM cell switch procedure to the first conditional LTM candidate cell.

22. The first network node (1600) of claim 21, wherein the request to configure the first cell is a CONTEXT SETUP REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT SETUP RESPONSE.

23. The first network node (1600) of claim 21, wherein the request to configure the first cell is a UE CONTEXT MODIFICATION REQUEST and the message including the lower layer configuration for the first conditional LTM candidate cell is a UE CONTEXT MODIFICATION RESPONSE.

24. The first network node (1600) of any one of claims 21-23, wherein the conditional LTMexecution condition is associated to the second conditional LTM candidate cell by a measurement configuration identifier for the second conditional LTM candidate cell.

25. A computer program product comprising program instructions configured to, when executed by processing circuitry (1502) of a user equipment, UE (1500), cause the UE (1500) to carry out a method according to any one of claims 1-6.

26. A computer-readable medium comprising, stored thereupon, the computer program product of claim 25.

27. A computer program product comprising program instructions configured to, when executed by processing circuitry (1602) of a first network node (1600), cause the first network node (1600) to carry out a method according to any one of claims 7-10.

28. A computer-readable medium comprising, stored thereupon, the computer program product of claim 27.

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