Resource configuration for conditional l1 / l2- triggered mobility (LTM) without random access

Abstract

Embodiments includes methods for a user equipment (UE) configured for conditional layer- 1 / layer-2 triggered inter-cell mobility (LTM) in a radio access network (RAN). Such methods include receiving the following information from a first RAN node via a source cell: a 5 configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled. Such methods include, in response to determining that the execution condition is fulfilled, performing an LTM cell switch from the source cell to the LTM candidate cell, including selectively 0 performing a random access (RA) to the LTM candidate cell based on whether the configured resources are activated. Other embodiments include complementary methods for the first and second RAN nodes. 5 Figure 7 is selected for publication.

Description

[0001] RESOURCE CONFIGURATION FOR CONDITIONAL L1 / L2- TRIGGERED MOBILITY (LTM) WITHOUT RANDOM ACCESS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to wireless networks, and more specifically to techniques for improving conditional layer-l / layer2 triggered mobility (LTM) of user equipment (UEs) across multiple cells in a radio access network (RAN), specifically in relation to configuring resources for UEs to avoid random access during execution of conditional LTM cell switch.

[0004] BACKGROUND

[0005] The fifth generation (5G) of cellular systems has been standardized within the Third- Generation Partnership Project (3GPP). 5G was developed for maximum flexibility to support many different use cases including enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device- to-device (D2D), and several other use cases. 5G was initially specified in Release 15 (Rel-15) and continues to evolve through subsequent releases.

[0006] Figure 1 shows an exemplary 5G network architecture, including a Next Generation Radio Access Network (NG-RAN, 199) and a 5G Core (5GC, 198). The NG-RAN 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 respective interfaces (102, 152). More specifically, the gNBs can be connected to one or more Access and Mobility Management Functions (AMFs) in the 5GC via respective NG-C interfaces and to one or more User Plane Functions (UPFs) in 5GC via respective NG-U interfaces. The 5GC can include various other network functions (NFs), such as Session Management Function(s) (SMF).

[0007] In addition, the gNBs can be connected to each other via one or more Xn interfaces, such as Xn interface (140) between gNBs (100, 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. Each of the gNBs can serve a geographic coverage area including one or more cells and, in some cases, can also use various directional beams to provide coverage in the respective cells. In general, a downlink (DL) “beam” is a coverage area of a network-transmitted reference signal (RS) that may be measured or monitored by a UE.

[0008] NG RAN logical nodes (e.g., gNB 100) include a Central Unit (CU or gNB-CU, e.g., 110) and one or more Distributed Units (DU or gNB-DU, e.g., 120, 130). CUs are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. DUs are decentralized logical nodes that host lower layer protocols and can include, depending on the functional split option, various subsets of the gNB functions. Each CU and DU can include various circuitry needed to perform their respective functions, including processing circuitry, communication interface circuitry (e.g., transceivers), and power supply circuitry. A gNB-CU connects to one or more gNB-DUs over respective Fl logical interfaces (e.g., 122 and 132 shown in Figure 1).

[0009] Seamless mobility is a key feature of 3GPP radio access technologies (RATs). In general, a RAN (e.g., NG-RAN) configures a UE to perform and report radio resource management (RRM) measurements to assist network-controlled mobility decisions, such as for handover from a serving cell to a neighbor cell. Seamless handovers ensure that the UE moves around in the coverage area of different cells without excessive interruption to data transmission.

[0010] Even so, handover and other mobility procedures can have various problems related to robustness. For example, a HO command is normally sent when the radio conditions for the UE are already quite bad, such as at or near cell borders. As such, the HO command may need to be segmented (e.g., to allow for redundancy to protect against errors) and / or retransmitted one or more times before it reaches the UE. In such case, the HO command may not reach the UE in time (or at all) before the degraded connection with the source node (e.g., the node hosting the UE’s current serving cell) is dropped. Failure of handover to a target cell may lead to the UE declaring radio link failure (RLF) in the source cell.

[0011] To address various difficulties with handovers and other mobility procedures, 3GPP Rel- 16 includes support for conditional handover (CHO) and SN-initiated intra-SN conditional PSCell change (CPC) procedures while Rel-17 includes support for various other conditional mobility procedures. A main principle of conditional mobility is separation of transmission and execution of a mobility (e.g., handover) command. This allows the mobility command to be sent earlier to UE when the radio conditions are still good, thus increasing the likelihood that it is successfully transferred. The execution of the mobility command is done at later point in time based on an associated execution condition.

[0012] Conditional mobility procedures are based on a conditional reconfiguration framework in which the network provides a UE with one or more reconfigurations, each with associated execution condition(s). Each reconfiguration can be provided in an RRCReconflguration message (in 5G) or an RRCConnectionReconflguration message (in fourth-generation (4G) Long-Term Evolution (LTE)). When the UE later detects the execution condition(s) associated with one of the earlier-received reconfigurations, the UE executes the associated reconfiguration to perform the mobility procedure (e.g., HO, PSCell change, PSCell addition, etc.).

[0013] Even so, conditional (e.g., CHO) and non-conditional (e.g., HO) mobility operations are triggered by layer 3 (L3) measurements and involves radio resource control (RRC) signaling to change primary cells as well as to release / add secondary cells as needed. Moreover, conventional inter-cell mobility involves complete layer 2 (L2) and layer 1 (LI) resets, leading to longer latency, increased signaling overhead, and longer interruptions than for intra-cell beam switching.

[0014] 3GPP Rel-18 includes new mobility procedures that facilitate serving cell changes via L1 / L2 signaling to address these problems and / or difficulties. These new procedures are often referred to as L1 / L2 based inter-cell mobility or L1 / L2 triggered mobility (LTM). In LTM, a UE is pre-configured by its serving RAN node with one RRC configuration per LTM candidate cell, sometimes referred to as an “LTM candidate cell configuration.”

[0015] Each LTM candidate cell configuration may include a configuration for early uplink (UL) synchronization (or “sync’) in the cell. Using the early UL sync configuration for an LTM candidate cell, the UE transmits on a random access channel (RACH) in the cell prior to receiving an LTM cell switch command for the cell, which may include a timing advance (TA) determined based on the UE’s earlier RACH transmission. In this manner, the UE can become UL synchronized with LTM candidate cells that are different from the UE’s current serving cell.

[0016] The UE performs measurements on configured LTM candidate cells and reports these measurements to its serving RAN node, based on which the RAN node triggers execution of an LTM cell switch procedure by the UE to one of the configured LTM candidate cells. The RAN node may trigger LTM cell switch by sending the UE an LTM cell switch command. If the UE has the TA value from its earlier RACH transmission, the UE does not need to perform RA before transmitting data or a scheduling request (SR) in the LTM candidate cell, based on an UL grant or SR configuration also included in the LTM cell switch command.

[0017] There are some notable differences between Rel-18 LTM and conditional L3 mobility. For example, unlike conditional L3 mobility in which the UE initiates execution, LTM is initiated by a UE’s serving RAN node based on measurements reported by the UE. This introduces some amount of delay in an LTM cell switch. To capture advantages of both LTM and conditional L3 mobility, 3GPP Rel-19 will introduce conditional LTM (CLTM). Much like conditional L3 mobility, when a UE detects the execution condition(s) associated with an earlier-received LTM candidate cell configuration, the UE executes an LTM cell switch to the candidate cell.

[0018] SUMMARY

[0019] Unlike Rel-18 LTM, the UE’s serving RAN node does not send the UE an LTM cell switch command for Rel-19 CLTM. This can cause various problems, issues, and / or difficulties. For example, since there is no LTM cell switch command in Rel-19 CLTM, the serving RAN node is unable to provide an UL grant of resources (or SR configuration) that enables the UE to directly transmit UL data (or SR) in the LTM candidate cell without first performing RA (“RACH- less”). One solution is to provide the UL grant (or SR configuration) to the UE in an earlier message during CLTM configuration. However, this would require the RAN node that provides the LTM candidate cell to reserve the cell resources for the UL grant (or SR configuration) for an indeterminate amount of time until execution conditions are fulfilled at the UE. This is undesirable since these cell resources may be scarce relative to the need for them by UEs being served by or entering the cell.

[0020] As another example, since there is no LTM cell switch command in Rel-19 CLTM, the serving RAN node is unable to provide a TA value for an LTM candidate cell at the time of the LTM cell switch. It is unclear how the UE determines a TA value that would enable it to directly transmit UL data (or SR) in the LTM candidate cell without first performing RA.

[0021] An object of embodiments of the present disclosure is to improve RACH-less conditional LTM cell switches for UEs, such as by providing, enabling, and / or facilitating solutions to overcome exemplary problems summarized above and described in more detail below.

[0022] Embodiments include methods (e g., procedures) for a UE configured for CLTM in a radio access network (RAN, e.g., E-UTRAN, NG-RAN).

[0023] These exemplary methods include receiving, from a first RAN node via a source cell, a configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled. These exemplary methods also include, in response to determining that the execution condition is fulfilled, performing an LTM cell switch from the source cell to the LTM candidate cell, including selectively performing a random access (RA) to the LTM candidate cell based on whether the configured resources are activated.

[0024] In some embodiments, selectively performing a RA to the LTM candidate cell includes the following operations:

[0025] • when the configured resources are activated, refraining from performing a RA to the LTM candidate cell and performing the initial transmission in the LTM candidate cell using at least part of the configured resources; and

[0026] • when the configured resources are not activated, performing a RA to the LTM candidate cell without using the configured resources.

[0027] In some embodiments, the configuration of resources include one or more of the following: one or more grants of UL resources, and an SR configuration. In some of these embodiments, the initial transmission using at least part of the configured resources is one of the following: an RRCReconflgurationComplete message using resources from an UL grant, or an SR using resources specified by the SR configuration. In some of these embodiments, these exemplary methods also include receiving, from the first RAN node or the second RAN node before the execution condition is fulfilled, an indication that the configured resources are activated. Selectively performing a RA to the LTM candidate cell is based on the indication.

[0028] In some variants of these embodiments, the LTM candidate cell configuration and the execution condition are received in a first message, the configuration of resources is received in the first message or in a second message after the first message, and the indication is included in or implicit from the second message.

[0029] Other embodiments include exemplary methods (e.g., procedures) for a first RAN node configured to facilitate CLTM by UEs. In general, these exemplary methods may be complementary to the exemplary methods for a UE summarized above.

[0030] These exemplary methods include sending the following information to a UE via a source cell provided by the first RAN node: a configuration for an LTM candidate cell provided by the first RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled. These exemplary methods also include sending, to the UE before the execution condition is fulfilled, an indication that the configured resources are activated.

[0031] In some embodiments, the configuration of resources include one or more of the following: one or more grants of UL resources, and an SR configuration. In some embodiments, the LTM candidate cell configuration and the execution condition are sent in a first message, the configuration of resources is sent in the first message or in a second message after the first message, and the indication is implicit from or included in the second message.

[0032] In some embodiments, these exemplary methods also include receiving the LTM candidate cell configuration and the configuration of resources from one of the following: the second RAN node, or a third RAN node associated with the first RAN node and with the second RAN node.

[0033] Other embodiments include exemplary methods (e.g., procedures) for a second RAN node configured to facilitate CLTM by UEs. In general, these exemplary methods may be complementary to the exemplary methods for a UE and for a first RAN node, summarized above.

[0034] These exemplary methods include sending the following information to a first RAN node that provides a source cell for a UE or to a third RAN node associated with the first and second RAN nodes: a configuration for an LTM candidate cell provided by the second RAN node, and a configuration of resources for an initial transmission by the UE in the LTM candidate cell after a configured execution condition is fulfilled. These exemplary methods also include selectively activating or deactivating the configured resources for the UE in the LTM candidate cell. These exemplary methods also include subsequently facilitating an LTM cell switch by the UE from the source cell to the LTM candidate cell when the configured execution condition is fulfilled, including selectively receiving an initial transmission by the UE in the LTM candidate cell based on whether the configured resources are activated for the UE.

[0035] In some embodiments, selectively receiving an initial transmission by the UE in the LTM candidate cell includes the following operations:

[0036] • when the configured resources are activated, receiving the initial transmission by the UE in the LTM candidate cell using at least part of the configured resources; and

[0037] • when the configured resources are not activated, receiving a RA preamble from the UE in the LTM candidate cell without using the configured resources.

[0038] In some embodiments, selectively activating or deactivating the configured resources for the UE in the LTM candidate cell comprises activating the configured resources for the UE in response to sending the configuration of resources to the first RAN node.

[0039] In other embodiments, these exemplary methods also include receiving a RA preamble from the UE in the LTM candidate cell before the execution condition is fulfilled and sending to the first or third RAN node a TA value for the UE in the LTM candidate cell, based on the received RA preamble.

[0040] In some of these embodiments, selectively activating or deactivating the configured resources for the UE in the LTM candidate cell comprises activating the configured resources in response to receiving the RA preamble. Also, an indication that the configured resources in the LTM candidate cell are activated for the UE is included with the TA value.

[0041] In other of these embodiments, these exemplary methods also include receiving, from the first or third RAN node, a request or command for the configured resources in the LTM candidate cell to be activated for the UE. In such embodiments, selectively activating or deactivating the configured resources for the UE in the LTM candidate cell comprises activating the configured resources in response to the request or command.

[0042] In various embodiments summarized above, the first RAN node may be a first DU, the second RAN node may be a second DU, and the third RAN node may be a CU associated with the first and second DUs.

[0043] Other embodiments and variants of the exemplary methods summarized above are described herein. Other embodiments include UEs (e.g., wireless devices) and RAN nodes (e.g., base stations, eNBs, gNBs, ng-eNBs, etc.) configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include non-transitory, computer- readable media storing program instructions that, when executed by processing circuitry, configure such UEs and RAN nodes to perform operations corresponding to any of the exemplary methods described herein.

[0044] These and other embodiments described herein may provide various advantages and / or benefits. For example, by providing timely configuration or activation of resources for a UE in an LTM candidate cell, embodiments may facilitate RACH-less conditional LTM cell switch by a UE without the need for a RAN node that provides the LTM candidate cell to keep the configured resources reserved indefinitely until cell switch execution conditions are fulfilled at the UE. As such, embodiments may enable the RAN node to configure a particular cell as an conditional LTM candidate cell for more UEs. By facilitating RACH-less conditional LTM cell switch, embodiments may reduce UE connection interruption, network signaling overhead, and UE energy consumption.

[0045] These and other objects, features, and advantages of embodiments of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 shows an exemplary 5G network architecture.

[0048] Figure 2 shows exemplary 5G user plane (UP) and control plane (CP) protocol layers.

[0049] Figure 3 shows a signaling diagram for an exemplary LTM cell switch procedure.

[0050] Figures 4-6 show signaling diagrams of various exemplary conditional LTM cell switch procedures, according to various embodiments of the present disclosure.

[0051] Figure 7 shows a flow diagram of an exemplary method for a UE (e.g., wireless device), according to various embodiments of the present disclosure.

[0052] Figure 8 shows a flow diagram of an exemplary method for a first RAN node (e.g., base station, eNB, gNB, DU, etc.), according to various embodiments of the present disclosure.

[0053] Figure 9 shows a flow diagram of an exemplary method for a second RAN node (e.g., base station, eNB, gNB, DU, etc.), according to various embodiments of the present disclosure.

[0054] Figure 10 shows a communication system according to various embodiments of the present disclosure.

[0055] Figure 11 shows a UE according to various embodiments of the present disclosure.

[0056] Figure 12 shows a network node according to various embodiments of the present disclosure.

[0057] Figure 13 shows a virtualization environment in which some embodiments of the present disclosure may be virtualized. DETAILED DESCRIPTION

[0058] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art.

[0059] In general, all terms used herein are to be interpreted according to their ordinary meaning to a person of ordinary skill in the relevant technical field, unless a different meaning is expressly defined and / or implied from the context of use. 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 or clearly implied from the context of use. The operations of any methods and / or procedures disclosed herein do not have to be performed in the exact order disclosed, unless an operation is explicitly described as following or preceding another operation and / or where it is implicit that an operation must follow or precede another operation. Any feature of any embodiment disclosed herein can apply to any other disclosed embodiment, as appropriate. Likewise, any advantage of any embodiment described herein can apply to any other disclosed embodiment, as appropriate.

[0060] Furthermore, the following terms are used throughout the description given below:

[0061] • 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 3GPP 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 (c.g. micro, pi co, 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.

[0062] • 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), aPDN 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. • 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”.

[0063] • Radio Node: As used herein, a “radio node” can be either a “radio access node” (or equivalent term) or a “wireless device.”

[0064] • 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.

[0065] • 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, IAB node) based on its specific characteristics in any given context.

[0066] The above definitions are not meant to be exclusive. In other words, various ones of the above terms may be explained and / or described elsewhere in the present disclosure using the same or similar terminology. Nevertheless, to the extent that such other explanations and / or descriptions conflict with the above definitions, the above definitions should control.

[0067] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system and can be applied to any communication system that may benefit from them.

[0068] Figure 2 shows exemplary 5G user plane (UP) and control plane (CP) protocol layers between a UE (210), a gNB (220), and an AMF (230). Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP) layers between UE and gNB are common to UP and CP. PDCP provides ciphering / deciphering, integrity protection, sequence numbering, reordering, and duplicate detection for both CP and UP, as well as header compression and retransmission for UP data.

[0069] On the UP side, Internet protocol (IP) packets arrive to PDCP 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 UL and DL packets. RLC transfers PDCP PDUs to MAC through logical channels (LCH). RLC provides error detection / correction, concatenation, segmentation / reassembly, sequence numbering, reordering of data transferred to / from the upper layers. MAC 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 (in gNB). PHY provides transport channel services to MAC and handles transfer over the NR radio interface, e.g., via modulation, coding, antenna mapping, and beam forming.

[0070] On the CP side, the non-access stratum (NAS) layer between UE and AMF handles UE / gNB authentication, mobility management, and security control. RRC 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, and performs various security functions such as key management.

[0071] After a UE is powered ON it will be in the RRCJDLE 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 RRCJDLE 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. A UE in RRCJDLE state is not known to the gNB serving the cell where the UE is camping. However, RRC includes an RRCJNACTIVE state in which a UE is known (e.g., via UE context) by the serving gNB. RRCJNACTIVE has some properties similar to a “suspended” condition used in LTE.

[0072] 3GPP Rel-10 introduced support for channel bandwidths larger than 20 MHz in LTE networks. To remain compatible with UEs from earlier releases (e.g., LTE Rel-8), a wideband LTE Rel-10 carrier appears as multiple component carriers (CCs), each having the same structure as an LTE Rel-8 carrier. A Rel-10 UE can receive the multiple CCs based on Carrier Aggregation (CA). The CCs can also be considered “cells,” such that a UE in CA has one primary cell (PCell) and one or more secondary cells (SCells) that are referred to collectively as a “cell group.”

[0073] LTE Rel-12 introduced dual connectivity (DC) whereby a UE can be connected to two network nodes simultaneously, thereby improving connection robustness and / or capacity. 5G / NR also supports various DC (or more generally, multi-connectivity) configurations for UEs. 3GPP TR 38.804 (v!4.0.0) describes various exemplary DC scenarios or configurations in which the MN and SN can apply NR, LTE, or both. In particular, a UE is configured with a Master Cell Group (MCG) provided by a master node (MN) and a Secondary Cell Group (SCG) provided by a secondary node (SN). Each cell group includes one MAC entity, a set of logical channels with associated RLC entities, a primary cell (i.e., PCell for MCG, PSCell for SCG), and optionally one or more SCells.

[0074] While in RRC CONNECTED state, the UE maintains a timing advance (TA) value for its UL transmissions to the serving gNB. The TA value indicates how much earlier in time the UE should initiate its UL transmissions to compensate for the propagation delay between the UE and the gNB’s antenna / receiver. The UEs in a cell apply individual TAs to ensure that their respective UL transmissions arrive to the gNB receiver in the appropriate (e.g., scheduled) time window.

[0075] The UE obtains an initial TA value when it performs random access (RA) to a cell. In particular, the UE transmits a RA preamble (also called “msgl”) in the cell, based on which the gNB determines the TA value and provides it to the UE in a RA response (also called “msg2”). While in RRC CONNECTED state in the cell, the UE maintains and updates TA based on continuous monitoring of the alignment of the DL signal from the gNB with the expected arrival window. Also, if the gNB notices the UE’s UL transmissions falling out of synchronization, it can send the UE a PDCCH order that causes the UE to send another RA preamble, based on which the gNB can determine and provide a new TA value.

[0076] In general, the UE has no TA value while in RRC IDLE and RRC_ INACTIVE states since it does not perform UL transmissions in these states. There is one exception for RRC INACTIVE state, specifically when the UE has been assigned a configured grant (CG) for small data transmission (SDT) while moving from RRC CONNECTED state to RRC INACTIVE state. This CG enables the UE to immediately transmit any UL data that arrives at its buffer while in RRC INACTIVE state. This transmission requires TA alignment and since the UE does not continuously adjust TA while in RRC INACTIVE, another technique to obtain TA introduced for CG-SDT in 3GPP Rel-17 and Rel-18.

[0077] Seamless mobility is a key feature of 3GPP radio access technologies (RATs). 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 L3 (e.g., RSRP) measurements and involves RRC signaling to change PCell and PSCell (e.g., when dual connectivity is configured), as well as release / add SCells (e.g., when CA is configured).

[0078] In general, a RAN (e.g., NG-RAN) configures a UE in RRC_CONNECTED state to perform and report radio resource management (RRM) measurements to assist network- controlled mobility decisions, such as for handover from a serving cell to a target cell (e.g., PCell change). Upon the reported measurements meeting a certain condition or threshold, the serving RAN node may send a handover command to the UE, indicating a target cell for the handover. In NR, the handover command is an RRCReconflguration message with a reconflgurationWithSync field. The procedure to perform a handover is sometimes also referred to as “L3 mobility”, as it is controlled by L3 and the RRC messages exchanged are part of L3.

[0079] These reconfigurations are prepared in advance by a target RAN node serving the target cell, upon a request from the UE’s serving RAN node. This request is transmitted over the Xn interface in case the serving and target RAN nodes are part of the NG-RAN. The reconfiguration in the handover command is based on the UE’s existing RRC configuration in its current serving cell (also referred to as “source cell”), which are provided in the inter-node request. In some cases, the reconfiguration can be provided as a “delta” to the UE’s existing configuration in the source cell, which reduces the size of the handover command.

[0080] The reconfiguration provided by the target RAN node contains all information the UE needs to access the target cell, e.g., random access configuration, a new cell radio network temporary identifier (C-RNTI) assigned to the UE in the target cell, and parameters enabling the UE to calculate security keys that it can use when communicating with the target cell (including sending a handover complete message).

[0081] In general, UE nobility in RRC CONNECTED state is network-based since the network has the most information about conditions such as cell loading (UEs and / or traffic), available node resources (e.g., processing), available frequencies, etc. Seamless handovers ensure that the UE moves around in the coverage area of different cells without excessive interruption to data transmission. However, there will be scenarios when the network fails to handover the UE to the “correct” neighbor cell in time, which can cause the UE will declare radio link failure (RLF) or handover failure (HOF).

[0082] To address various difficulties with handovers and other mobility procedures, 3GPP Rel- 16 includes support for conditional handover (CHO) and SN-initiated intra-SN conditional PSCell change (CPC) procedures while Rel-17 includes support for various other conditional mobility procedures. A main principle of conditional mobility is separation of transmission and execution of a mobility (e.g., handover) command. This allows the mobility command to be sent earlier to UE when the radio conditions are still good, thus increasing the likelihood that it is successfully transferred. The execution of the mobility command is done at later point in time based on an associated execution condition.

[0083] Conditional mobility procedures are based on a conditional reconfiguration framework in which the network provides a UE with one or more reconfigurations, each with associated execution condition(s). Each reconfiguration can be provided in an RRCReconflguration message (in NR) or an RRCConnectionReconfiguration message (in LTE). When the UE later detects the execution condition(s) associated with one of the earlier-received reconfigurations, the UE executes the associated reconfiguration to perform the mobility procedure (e.g., HO, PSCell change, PSCell addition, etc.).

[0084] Even so, conditional (e.g., CHO) and non-conditional (e.g., HO) are triggered by layer 3 (L3) measurements and involves radio resource control (RRC) signaling to change PCell and PSCell (e.g., when DC is configured), as well as release / add SCells as needed. Moreover, conventional 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.

[0085] 3GPP Rel-18 includes new mobility procedures that facilitate serving cell changes via L1 / L2 signaling to address these problems and / or difficulties. These new procedures are often referred to as L1 / L2 based inter-cell mobility or L1 / L2 triggered mobility (LTM). In LTM, a UE is pre-configured by its serving RAN node with one RRC configuration per LTM candidate cell, sometimes referred to as an “LTM candidate cell configuration.” The UE performs measurements on configured LTM candidate cells and transmits corresponding measurement reports to the RAN node, based on which the RAN node triggers execution of a LTM cell switch procedure by the UE to one of the configured LTM candidate cells. The RAN node may trigger the LTM cell switch procedure by sending the UE an LTM cell switch command.

[0086] In LTM, a UE is pre-configured by its serving RAN with one RRC configuration per LTM candidate cell, sometimes referred to as an “LTM candidate cell configuration”. This configuration may be an RRCReconflguration message or a portion thereof, such as one or more lEs / fields / parameters (e.g., CellGroupConflg IE). The UE performs measurements on configured LTM candidate cells and transmits corresponding measurement reports to the RAN, which triggers the execution of a LTM cell switch procedure by the UE to one of the configured LTM candidate cells. This triggering is done by transmitting an LTM cell switch command to the UE in lower layer signaling (e.g., DCI or MAC CE). Based on this command, the UE connects to the associated LTM candidate cell and uses the previously received RRC configuration for this cell. Regarding terminology, a candidate cell configured for a UE mobility procedure (e.g., LTM or L3) becomes a target cell when the UE performs the mobility procedure, either due to a command from the UE’s current serving RAN node or due to execution conditions being met at the UE. As such, in the context of conditions. As such, the terms “candidate,” “target,” and “candidate (target)” may be used interchangeably when referring to that cell or to the RAN node serving that cell. Likewise, the UE’s serving cell becomes when the UE performs the mobility procedure, and so the terms “source,” “serving,” and “serving (source)” may be used interchangeably when referring to that cell or to the RAN node serving that cell.

[0087] Figure 3 shows a signaling diagram for an exemplary LTM cell switch procedure. Although some of the operations in Figure 3 are given numerical labels, this is done to facilitate the following explanation rather than to require or imply any specific operational order, unless expressly stated otherwise.

[0088] In operation 1, the UE (310) sends a MeasurementReport message to the gNB (320). Based on this message, the gNB decides to configure LTM for the UE and initiates preparation of one or more LTM candidate cells. In operation 2, the gNB sends an RRCReconflguration message to the UE including LTM candidate cell configurations of one or more candidate cells. In operation 3, the UE stores the received LTM candidate cell configurations and transmits an RRCReconflgurationComplete message to the gNB.

[0089] Since a goal of LTM is to reduce interruption time for UE data transmissions, the UE needs to be ready to communicate with an LTM candidate cell upon (or shortly after) receiving the L1 / L2 signaling for mobility execution from the source cell. For example, the UE must be able to transmit UL data or a scheduling request (SR) to the LTM candidate cell and / or monitor a DL control channel (e.g., PDCCH) from the LTM candidate cell. In other words, UE needs to know the cell that it is moving to so it can apply the corresponding configuration, including the correct timing alignment and / or TCI state for the cell. Likewise, in the case of inter-DU LTM, when the source DU transmits the L1 / L2 signaling for mobility execution, the target DU needs to be prepared for scheduling UL and DL transmissions for the UE in the target cell, and for receiving SR from the UE.

[0090] The UE performs operations 4a-b before receiving any LTM cell switch command. In operation 4a, the UE performs early DL synchronization with the configured LTM candidate cells. Each LTM candidate cell configuration may include a configuration for early DL synchronization, which may also be referred to as an “LTM candidate TCI state configuration” or more simply as a “TCI state configuration.” For example, the TCI state configuration may include an RRC CandidateTCI-State IE and / or an RRC CandidateTCI-UL-State IE. Once configured in this manner, early TCI state activation may be triggered by a MAC CE from the serving RAN node, such as a Candidate Cell TCI States Activation / Deactivation MAC CE that identifies one or more TCI states configured in CandidateTCI-State and / or CandidateTCI-UL-State IES.

[0091] The early DL synchronization of operation 4a may include detecting and / or measuring at least one synchronization signal of the LTM candidate cell, such as SSB that is associated with an SSB index and is transmitted in a spatial direction corresponding to a beam. For example, measuring the synchronization may produce one or more measurement results such as Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and / or Signal to Noise and Interference Ratio (SINR). The early DL synchronization of operation 4a may also include acquiring timing information for the LTM candidate cell (e.g., boundaries of time slots, OFDM symbols, subframes, radio frames, etc.) and synchronizing the UE’s internal timing source (e.g., clock) with the acquired timing information (e.g., boundaries). Later UE transmissions (e.g., operations 4b, 7-8) to the LTM candidate cell are based on the UE’s synchronized internal timing source.

[0092] In operation 4b, when UE-based TA measurement is configured, UE acquires the TA value(s) of the candidate cell(s) by measurement. Otherwise, in operation 4b, the UE performs early TA acquisition with the candidate cell(s) as requested by the network. This is done via contention-free random access (CFRA) triggered by a physical DL control channel (PDCCH) order from the source cell, which causes the UE to transmit a RA preamble towards the indicated LTM candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the LTM candidate cell(s), the UE doesn’t receive RA response (with TA) from the LTM candidate cell; instead, a TA value for the LTM candidate cell is indicated in a subsequent LTM cell switch command (e.g., operation 6 below). Typically, the UE doesn’t maintain a TA timer for the LTM candidate cell but relies on the RAN to guarantee the TA validity.

[0093] In operation 5, the UE performs LI measurements on the configured LTM candidate cells and transmits LI measurement reports to the gNB. The UE performs such LI measurement as long as the LTM candidate cell configurations received in operation 2 remain applicable.

[0094] In operation 6, the gNB decides to trigger an LTM cell switch for the UE to one of the configured LTM candidate cells ( “target cell”) and transmits an LTM cell switch command, which is a MAC CE that includes an identifier (e.g., index) of the corresponding LTM candidate cell configurations provided to the UE in operation 2. The MAC CE may also include an identifier of a beam (e.g., a TCI State ID) by which the UE should access the target cell, as well as a TA value for the UE to use when transmitting to the target cell. The gNB selects the identified beam based on the LI measurements reported by the UE.

[0095] In some cases, the LTM cell switch command may include an UL grant of resources for the UE to use for transmission (e.g., in operation 8 below) in the LTM candidate cell. Alternately or in addition, the LTM cell switch command may include an SR configuration (e.g., of SR resources) for the UE to use for transmitting a SR in the LTM candidate cell, e.g., to obtain an UL grant of resources for subsequent transmission.

[0096] Upon receiving the LTM cell switch command, the UE monitors PDCCH on the indicated beam of the target cell. In other words, the UE considers the TCI state for the indicated beam / TCI state ID to be “activated” when performing the LTM cell switch. The UE also applies the configuration identified in the MAC CE.

[0097] In operation 7, if UE did not receive a TA value for the target cell, the UE performs a RA procedure towards the target cell. The UE performs CFRA if the LTM cell switch command contains the necessary information, as specified in clause 6.1.3.xy of 3GPP TS 38.321 (vl7.7.0). In operation 8, the UE completes the LTM cell switch procedure by transmitting an RRCReconfigurationComplete message to the gNB via the target cell, using the TA value obtained in operation 6 or 7. If the UE received an UL grant of resources in the LTM cell switch command, the UE uses these resources for transmission of the RRCReconfigurationComplete message. If the UE received an SR configuration instead of an UL grant, the UE first transmits a SR based on the SR configuration, obtains an UL grant from the gNB, and then transmits the RRCReconfigurationComplete message using the obtained UL grant.

[0098] If the UE performed a RA procedure in operation 7, the UE considers LTM cell switch execution successfully completed when the RA procedure is successfully completed. For RACH- less LTM, the UE considers LTM cell switch execution successfully completed when the UE determines that the gNB has successfully received its first UL data. The UE determines successful reception of its first UL data by receiving a PDCCH addressing the UE’s C-RNTI in the target cell, which schedules a new transmission following the first UL data. The PDCCH carries either a DL assignment or an UL grant addressing the same HARQ process as the first UL data.

[0099] The split CU / DU architecture shown in Figure 1 also supports LTM, including for intra- DU and inter-DU / intra-CU cell changes. In the inter-DU / intra-CU scenario, the candidate cell for LTM is a cell served by a neighbor DU to the source DU that currently provides the UE’s PCell (or PSCell, for SCG change in DC). In the intra-DU scenario, the candidate cell for LTM is a cell served by the same DU that currently provides the UE’s PCell (or PSCell, for SCG change in DC). Since the procedure shown in Figure 3 involves a single gNB, it can also be considered an intra-CU LTM cell switch and possibly also an intra-DU LTM cell switch.

[0100] In contrast, an inter-CU (or inter-gNB) LTM procedure involves a cell switch from a source cell served by a first CU / gNB to a candidate (target) cell served by a second CU / gNB. In addition to the operations described above in relation to Figure 3, UE actions performed during an inter-CU LTM cell switch procedure may also include other actions such as refresh of security keys. As such, an inter-CU LTM configuration may include the same information as an intra-CU (or intra-gNB) LTM configuration as well as one or more of the following:

[0101] • Information needed to perform security key refresh, e.g., MasterKeyUpdate IE or a RadioBearerConflg IE that includes SecurityConflg with SecurityAlgorithmConfig',

[0102] • Indication to perform L2 / PDCP re-establishment; and

[0103] • Indication to perform a full configuration, e.g., RRC field fullConfig.

[0104] As discussed above, in Rel-18 non-conditional LTM, the UE’s serving RAN node sends the UE a command for LTM cell switch to one of the UE’s configured LTM candidate cells, and the command may include a TA value determined based on the UE’s earlier RA transmission towards the LTM candidate cell. In some cases, the command may also include an UL grant of resources and / or an SR configuration for the UE in the LTM candidate cell. All of this information facilitates RACH-less LTM cell switch by the UE. In case of intra-DU / intra-gNB LTM, the RAN node serving the LTM candidate cell may determine the TA value, the UL grant, and / or the SR configuration for the UE and provide it to the UE’s current serving RAN node.

[0105] Since there is no LTM cell switch command in Rel-19 CLTM, however, the serving RAN node is unable to provide this information for the LTM candidate cell to the UE just before the LTM cell switch. Without this information, the UE must perform a conventional RA to the LTM candidate cell to obtain a TA value and an UL grant of resources for further transmissions (e.g., RRCReconfigurationComplete message and data) to the LTM candidate (or target) cell. These operations increase latency, signaling overhead, and interruptions for CLTM cell switch, which is directly contrary to the goals of LTM.

[0106] One solution is to provide the TA value, the UL grant, and / or the SR configuration to the UE in an earlier message during CLTM configuration. However, this would require the RAN node that provides the LTM candidate cell to reserve cell resources for the UL grant (or SR configuration) for an indeterminate amount of time until execution conditions are fulfilled at the UE. This is undesirable since these cell resources may be scarce relative to the demand for them by UEs being served by or entering the cell. Moreover, it is unclear how a UE would know whether a previously received TA value is still valid when LTM cell switch conditions are fulfilled.

[0107] Accordingly, embodiments of the present disclosure address these and related problems and / or issues by various techniques for a serving RAN node to provide a UE with a configuration for an LTM candidate cell, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and resources for the LTM candidate cell that enable the UE to perform the LTM cell switch in a RACH-less manner when the execution conditions are fulfilled. For example, the configured resources may include a TA value, an UL grant, and / or an SR configuration (i.e., of SR resources). In some embodiments, some of the resources may be configured together with (i.e., in the same message as) the LTM candidate cell configuration and execution condition but activated by a subsequent message for use by the UE. In other embodiments, some or all of the resources may be configured in the subsequent message, i.e., after the message that configures the LTM candidate cell configuration and execution condition. For example, the subsequent message may be a MAC CE related to early UL or DL synchronization, while the LTM candidate cell configuration and execution condition may be provided in an earlier RRCReconflguration message.

[0108] Embodiments of the present disclosure may provide various advantages and / or benefits. For example, by providing timely configuration or activation of resources for a UE in an LTM candidate cell, embodiments may facilitate RACH-less conditional LTM cell switch by a UE without the need for a RAN node that provides the LTM candidate cell to keep the configured resources reserved indefinitely until cell switch execution conditions are fulfilled at the UE. As such, embodiments may enable the RAN node to configure a particular cell as an conditional LTM candidate cell for more UEs. By facilitating RACH-less conditional LTM cell switch, embodiments may reduce UE connection interruption, network signaling overhead, and UE energy consumption.

[0109] In the present disclosure, the following terms may be used interchangeably: “L1 / L2 based inter-cell mobility”, “L1 / L2 mobility,” “LI -mobility,” “LI based mobility,” “Ll / L2-centric inter-cell mobility,” “L1 / L2 inter-cell mobility,” “inter-cell beam management,” “inter-DU L1 / L2 based inter-cell mobility”, and “L1 / L2 triggered mobility” (or LTM). These terms refer to a scenario in which a UE receives lower layer (i.e., below RRC, such as MAC or PHY) signaling from a network indicating for the UE to change of its serving cell (e.g., PCell) from a source cell to a target cell.

[0110] The content of the lower layer signaling may be referred to as “LTM cell switch command”. Exemplary lower layer signaling includes LI DL control information (DCI) and L2 MAC control element (CE). Compared to conventional RRC signaling, lower layer signaling reduces processing time and interruption time during mobility and may also increase mobility robustness since the network can respond more quickly to changes in the UE’s channel conditions.

[0111] The term “LTM candidate cell” refers to a cell for which the UE is configured for LTM, specifically a cell the UE can move to in a LTM cell switch procedure in response to receiving an LTM cell switch command. An LTM candidate cell may also be referred to herein as “candidate cell”, “(LTM) candidate, “mobility candidate”, “non-serving cell”, “additional cell”, “(LTM) target candidate cell”, “(LTM) target candidate”, and comparable terms. A UE may perform and report measurements (e.g., CSI measurements) on an LTM candidate cell, based on which the UE’s serving RAN node may make an informed decision about which beam (or TCI state) and / or cell to switch the UE. 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). In the case of LTM fast recovery, when a failure is detected and the UE selects an LTM candidate cell, the UE performs an LTM cell switch towards the selected LTM candidate cell (e.g., by applying the associated LTM candidate cell configuration) rather than performing RRC re-establishment.

[0112] The change of serving cell (e.g., PCell) may also lead to a change in SCell(s) of the same cell group, e.g., in case an LTM cell switch command triggers the UE to change to another cell group configuration of the same type (e.g., another MCG configuration). For example, an LTM cell switch may include a change in SpCell (e.g., PCell for MCG, PSCell for SCG) and a change (e.g., addition, modification and / or release) in SCells of the same cell group. This may happen when the command triggers the UE to change to another cell group configuration of the same type (e.g., another SCG configuration).

[0113] Before the UE receives the LTM cell switch command, the UE is configured by the network with one or more “LTM candidate cell configurations” via an RRCReconflguration message. The terms “(LTM) candidate configuration”, “(LTM) candidate target cell configuration”, and “(LTM) target candidate (cell) configuration” may be used interchangeably with LTM candidate cell configuration.

[0114] An LTM candidate cell configuration may be included in an RRC IE such as CellGroupConfig, SpCellConfig, or SCellConfig and / or an embedded RRCReconflguration message for an LTM candidate cell. An LTM candidate cell configuration includes configuration parameters the UE needs to operate in that LTM candidate cell when it performs an LTM cell switch procedure, e.g., upon reception of the LTM cell switch command. As some more specific examples, an LTM candidate cell configuration can include a PCell configuration and one or more SCell configurations of an MCG, or a PSCell configuration and one or more SCell configurations of an SCG. The exact content and / or structure of the IE and / or embedded message for an LTM candidate cell configuration may be called “RRC model for the candidate configuration” or more simply “RRC model”.

[0115] A UE may receive an LTM candidate cell configuration in complete form or as a delta (or difference) relative to a reference configuration (which may be signaled separately). In the latter case, the actual LTM candidate configuration is a combination of the delta configuration and the reference configuration.

[0116] The lower layer signaling from the RAN may include an identifier (or index) associated with an LTM candidate cell configuration. The identifier may be sent together with an LTM cell switch command, indicating for the UE to perform an LTM cell switch to the associated LTM candidate cell. The term “LTM configuration” refers to a data structure that is used for or related to UE LTM operations, and may include one or more of the following elements (non-exclusive):

[0117] • an LTM candidate cell configuration, such as one or more of the following for an LTM candidate cell: o lower layer information, such as Ll / PHY configuration, L2 / MAC / RLC configuration, cell group configuration, serving cell configuration, etc.; and o higher layer information, such as L3 / RRC parameter and / or timer values, PDCP configuration, radio bearer configuration, L3 / RRC measurement configuration, etc.;

[0118] • a measurement configuration, e.g., measurements for LTM, measurement reports for LTM, CSI resource configuration for LTM, CSI report configuration for LTM, etc.;

[0119] • a configuration for early DL synchronization, e.g., for early TCI state activation;

[0120] • a configuration for early UL synchronization, e.g., for PDCCH ordered preamble transmission and reception of timing advance (TA);

[0121] • a configuration for execution of an LTM cell switch procedure according to a given LTM candidate cell configuration (e.g., whether to perform RA, RLC reestablishment, MAC reset, PDCP recovery, etc.).;

[0122] • additional information needed for an intra-CU / gNB LTM cell switch procedure.

[0123] The term “part of an LTM configuration” may refer to a subset of the elements in the above list, and / or a subset of items comprising any of the elements present (e.g., subset of configurations for DL pre-sync).

[0124] The phrase “LTM cell switch procedure” refers to the process of a UE switching (or changing) from a source cell to a target cell (i.e., an LTM candidate cell) using LTM. An LTM cell switch procedure may also be referred to 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”. Similarly, the phrase “switching to an LTM candidate cell configuration” means that the UE applies an LTM candidate cell configuration such that the associated LTM candidate cell becomes its new special cell (SpCell, e.g., PCell for LTM in MCG or PSCell for LTM in SCG) or its new SCell. In other words, an LTM candidate cell can be a candidate for the UE’s PCell, PSCell, or SCell.

[0125] Furthermore, an LTM cell switch may involve a UE switching (or changing) from a source cell group to a target cell group using LTM. For example, this may involve a change in the SpCell for a cell group (e.g., PCell for MCG, PSCell for SCG), a change in SCells of the cell group (e.g., addition, modification, and / or release of one or more SCells), and / or a swap between SpCell and SCell roles for two cells in the same cell group. More generally, embodiments are not limited to cells but are applicable to any UE switch from a first (or source) set of radio resources to a second (or target) set of radio resources.

[0126] Figures 4-6 show signaling diagrams of various exemplary conditional LTM cell switch procedures, according to various embodiments of the present disclosure. All of the procedures shown in Figures 4-6 involve a UE (410), a source DU (S-DU, 420) that provides a source cell for the UE, a candidate CU (C-DU, 440) that provides an LTM candidate (target) cell, and a CU (430) that controls the S-DU and the C-DU. In other words, Figures 4-6 show intra-CU / inter-DU conditional LTM cell switch procedures. Although the operations shown in Figures 4-6 are given numerical labels, this is done to facilitate the following descriptions rather than to require or imply any particular operational order, unless expressly stated otherwise.

[0127] Figure 4 will be described first. In operation 1, the CU and the S-DU perform various actions to configure a cell provided by the C-DU as a conditional LTM candidate cell for the UE. This includes the C-DU providing the CU an LTM candidate cell configuration (e.g., an RRC Itm- CandidateConflg-r 18 IE) and an execution condition whose fulfillment triggers an LTM cell switch by the UE. Alternately, the CU or the S-DU may determine the execution condition.

[0128] In the embodiments shown in Figure 4, the C-DU also configures resources that enable a UE to perform RACH-less LTM cell switch to the LTM candidate cell when execution conditions are fulfilled. These resources may include an UL grant and / or an SR configuration. For example, the UL grant may be for periodic resources in the LTM candidate cell, and may include a single configured UL grant (i.e., with periodic resources) or multiple individual UL grants that are periodic in time. The C-DU may provide a configuration of the resources to the CU as part of or separate from the LTM candidate cell configuration. However, the resources for RACH-less LTM cell switch to the LTM candidate cell are not active when they are configured.

[0129] In operation 2, the CU creates an RRCReconflguration message that includes the information received from the C-DU in operation 1 and sends it to the S-DU encapsulated in a DLRRCMessageTransfer message. For example, the configuration of resources may be included in an RRC LTM-Candidate-r 18 IE of the RRCReconflguration message but separate from the Itm- CandidateConflg-r 18 IE for the LTM candidate cell included therein. As another example, the configuration of resources is included in the RRCReconflguration message but separate from the LTM-Candidate-r 18 IE included therein.

[0130] In operation 3, the S-DU sends the received RRCReconflguration message to the UE. In operation 4, the UE sends an RRCReconfigurationComplete message to the C-DU, which sends it to the CU encapsulated in an ULRRCMessageTransfer message in operation 5. Note at this point, the UE is not allowed to use the non-active resources for RACH-less LTM cell switch to the LTM candidate cell. In operation 6, the S-DU sends the UE a PDCCH order for early TA acquisition in the LTM candidate cell, which causes the UE to transmit a RA preamble towards the LTM candidate cell in operation 7. Upon detecting the RA preamble via the LTM candidate cell, in operation 8 the C-DU sends the CU a message (e.g., “DU-CU TA information transfer”) that includes a TA value determined based on the detected RA preamble, an index of the detected RA preamble, an ID of the LTM candidate cell, and an ID of the S-DU. In addition, the S-DU includes in the message an indication that the previously configured resources have been activated for use by the UE. Note that this indication may refer to only part of the configured resources, such as the part of the resources that occur later in time.

[0131] In operation 9, the CU forwards the information received in operation 8 to the S-DU in another message (e.g., “CU-DU TA information transfer”). In operation 10, the S-DU sends the UE a MAC CE for early UL synchronization, which includes the TA value, the LTM candidate cell ID, and the indication that the previously configured resources have been activated for use by the UE. In some embodiments, the TA value can also be considered part of the resources, since it also facilitates RACH-less LTM cell switch to the LTM candidate cell.

[0132] In operation 11, the execution condition configured in operation 3 is fulfilled at the UE. This causes the UE to perform a RACH-less LTM cell switch to the LTM candidate cell in operation 12 using the resources that were previously configured (operation 3) and activated (operation 10). For example, the UE can transmit an RRCReconfigurationComplete message to the C-DU via the LTM candidate (target) cell using resources of the UL grant, without first transmitting a RA preamble.

[0133] The MAC CE used to convey the indication that the previously configured resources have been activated in operation 10 is only an example. Alternately, this indication may be sent to the UE in a different MAC CE, an RRC message, layer-1 downlink control information (DCI, e.g., PDCCH order), etc. A currently-defined message may be modified / extended or a new message may be defined to carry this indication. Additionally, this indication may be sent in the same message as a TA value for the LTM candidate cell (as in Figure 4) or in a different message than the TA value. For example, the indication may be sent in a message related to early UL synchronization of a different LTM candidate cell or in a message unrelated to early UL synchronization.

[0134] Although Figure 4 shows the TA value and the indication being sent to the UE by the S- DU, it is also possible that the TA value and the indication are sent to the UE directly by the C- DU via the LTM candidate cell, e.g., in a random-access response (RAR) or similar message.

[0135] Figure 5 shows another conditional LTM cell switch procedure according to other embodiments of the present disclosure. Operations 1-7 are similar to corresponding operations 1- 7 of Figure 4, except that in operation 1 the C-DU does not configure resources that enable the UE to perform RACH-less LTM cell switch to the LTM candidate cell when execution conditions are fulfilled. Thus, the RRCReconflguration message received by the UE in operation 3 does not include a configuration of such resources.

[0136] In operation 8, after detecting the UE’s RA preamble via the LTM candidate cell, the C- DU configures resources that enable the UE to perform RACH-less LTM cell switch to the LTM candidate cell when execution conditions are fulfilled. These resources may include an UL grant and / or an SR configuration, including any of the embodiments or variants described above in relation to Figure 4. In contrast to Figure 4, however, the resources are activated at time of configuration. The C-DU sends the CU a message (e.g., “DU-CU TA information transfer”) that includes a TA value determined based on the detected RA preamble, an index of the detected RA preamble, an ID of the LTM candidate cell, and an ID of the S-DU. In addition, the S-DU includes in the message a configuration of the resources that enable the UE to perform RACH-less LTM cell switch to the LTM candidate cell.

[0137] In operation 9, the CU forwards the information received in operation 8 to the S-DU in another message (e.g., “CU-DU TA information transfer”). In operation 10, the S-DU sends the UE a MAC CE for early UL synchronization, which includes the TA value, the LTM candidate cell ID, and the configuration of resources that are activated for use by the UE. In some embodiments, the TA value can also be considered part of the resources, since it also facilitates RACH-less LTM cell switch to the LTM candidate cell.

[0138] In operation 11, the execution condition configured in operation 3 is fulfilled at the UE. This causes the UE to perform a RACH-less LTM cell switch to the LTM candidate cell in operation 12 using the active resources that were previously configured (operation 10). For example, the UE can transmit an RRCReconfigurationComplete message to the C-DU via the LTM candidate (target) cell using resources of the UL grant, without first transmitting a RA preamble.

[0139] Although Figure 5 shows the TA value and the configuration of resources being sent to the UE by the S-DU, it is also possible that the TA value and the configuration of resources are sent to the UE directly by the C-DU via the LTM candidate cell, e.g., in a RAR or similar message.

[0140] Figure 6 shows another conditional LTM cell switch procedure according to other embodiments of the present disclosure. Operations 1-7 are substantially identical to corresponding operations 1-7 of Figure 4. Operations 8-10 are similar to corresponding operations 8-10 of Figure 4, except that during (or in relation to) operation 8, the C-DU does not activate the previously configured resources that enable the UE to perform RACH-less LTM cell switch to the LTM candidate cell. Thus, the messages of operations 8-10 do not include the indication that the previously configured resources have been activated. Note that even after receiving the MAC CE in operation 10, the UE is not allowed to use the previously configured resources for RACH-less LTM cell switch to the LTM candidate cell.

[0141] In operation 11, the S-DU sends the UE a MAC CE for TCI state activation as part of early DL synchronization. For example, the S-DU may send the UE a Candidate Cell TCI States Activation / Deactivation MAC CE that identifies one or more TCI states previously configured in CandidateTCI-State and / or CandidateTCI-UL-State IES (e.g., in operation 3). The MAC CE also includes an indication that the previously configured resources have been (or will be) activated for use by the UE in the LTM candidate cell. Note that in these embodiments, the S-DU rather than the C-DU makes the decision to activate the previously configured resources for RACH-less LTM cell switch.

[0142] In operation 12, the S-DU sends the CU a message (e.g., “DU-CU early UL / DL sync notification”) that includes an indication that the previously configured resources in the LTM candidate cell should be activated by the C-DU that provides that cell. The message may also include other information pertaining to early UL and / or DL synchronization of the UE to the LTM candidate cell. In operation 13, the CU forwards the information received in operation 12 to the S-DU in another message (e.g., “CU-DU early UL / DL sync notification”). In operation 14, the C- DU activates the previously configured resources for the UE in the LTM candidate cell.

[0143] In operation 15, the execution condition configured in operation 3 is fulfilled at the UE. This causes the UE to perform a RACH-less LTM cell switch to the LTM candidate cell in operation 16 using the resources that were previously configured (operation 3) and activated (operation 14). For example, the UE can transmit an RRCReconfigurationComplete message to the C-DU via an activated TCI state of the LTM candidate (target) cell using resources of the UL grant, without first transmitting a RA preamble.

[0144] The MAC CE used to convey the indication that the previously configured resources have been activated in Figure 6 operation 11 is only an example. Alternately, this indication may be sent to the UE in a different MAC CE, an RRC message, layer-1 DCI (e.g., PDCCH order), etc. A currently -defined message may be modified / extended or anew message may be defined to carry this indication. Additionally, this indication may be sent in the same message as a TCI state activation for the LTM candidate cell (as in Figure 6) or in a different message than the TCI state activation. For example, the indication may be sent in a message related to early DL synchronization of a different LTM candidate cell or in a message unrelated to early DL synchronization.

[0145] Although Figure 6 shows the TCI state activation and the indication being sent to the UE by the S-DU, it is also possible that the TCI state activation and the indication are sent to the UE directly by the C-DU via the LTM candidate cell, e.g., in a random-access response (RAR) MAC protocol data unit (PDU) or similar message.

[0146] To summarize, in the embodiments shown in Figures 4 and 6, the UE receives a configuration of resources for RACH-less LTM cell switch together with the LTM candidate cell configuration and a subsequent message that activates the configuration of resources. Figures 4 and 6 show different subsequent messages. In the embodiments shown in Figure 5, the UE receives the LTM candidate cell configuration and a subsequent message with the configuration of (activated) resources.

[0147] In some variants, a TA value for an LTM candidate cell (i.e., after UE transmission of RA preamble) implicitly indicates that previously-configured resources for RACH-less LTM cell switch have been activated. In other variants, activation of one or more TCI states for an LTM candidate cell (i.e., after UE transmission of RA preamble) implicitly indicates that previously- configured resources associated with the TCI state have been (or will be) activated. In other variants, a PDCCH order for an LTM candidate cell implicitly indicates that previously- configured resources for RACH-less LTM cell switch have been activated.

[0148] In some embodiments, the resources for RACH-less LTM cell switch are valid for use by the UE for a limited duration after they are configured or activated. In some variants, a validity duration may be included with the configuration of resources or with an indication that the configured resources have been (or will be) activated. The UE initiates a timer upon receiving the configuration or the activation indication and when the timer expires (i.e., reaches aterminal value of zero or validity duration) before the configured resources are used (or activated, if not configured as active), the UE considers the resources to be invalid (if timer initiated upon configuration) or deactivated (if timer initiated upon activation).

[0149] In other variants, the UE considers configured resources as active only while a TA value for the same LTM candidate cell is valid. For example, the UE starts a time alignment timer when it receives a TA value for an LTM candidate cell. The resources are considered valid (or activated) for RACH-less LTM cell switch only while the timer is running and not expired. For example, a TAT initiation value may be included in the same message as the TA value for the candidate target cell (e.g., Figures 4-6 operation 10) or in a separate message (e.g., with the LTM candidate cell configuration).

[0150] In some embodiments, the S-DU may send the UE an indication that previously- configured resources for an LTM candidate cell have been deactivated, such that they can no longer be used by the UE for RACH-less LTM cell switch to the LTM candidate cell. In some of these embodiments, the indication of deactivation sent to the UE may be based on a corresponding indication of deactivation received from the C-DU via the CU. In other embodiments, the C-DU may send the indication of deactivation to the UE while the UE is still being served by the S-DU (e.g., in a RAR or similar message).

[0151] If the condition for execution of the LTM cell switch is then fulfilled at the UE, the UE does not use the deactivated resources for the LTM cell switch. If the UE does not have any other active resources for RACH-less LTM cell switch to the LTM candidate cell (and optionally a particular beam of the LTM candidate cell), the UE would perform RACH-based LTM cell switch to the LTM candidate cell including transmission of a RA preamble.

[0152] As briefly mentioned above, embodiments may enable a RAN node to configure a particular cell as an conditional LTM candidate cell for more UEs than conventional techniques. In some embodiments, the RAN node (e.g., C-DU) may configure the same (or at least partially overlapping) resources in the cell for multiple UEs in different source cells to use for RACH-less LTM cell switch to the cell (i.e., as LTM candidate cell). There will be no resource conflicts so long as no two of the UEs perform concurrent RACH-less LTM cell switches to the LTM candidate cell. For example, if a first UE performs a RACH-less LTM cell switch using the configured resources, the RAN node can then reconfigure the UE to use other resources of the cell. Subsequently, a second UE can use the same configured resources to perform a RACH-less LTM cell switch.

[0153] In other embodiments, the RAN node (e.g., C-DU) may configure the same (or at least partially overlapping) cell resources for a first UE currently being served by the cell and for a second UE (i.e., served by a source cell) to use for RACH-less LTM cell switch to the cell (i.e., as LTM candidate cell). The RAN node can use the configured resources for serving the first UE until receiving one of the following that indicates the configured resources are required by the second UE:

[0154] • a RA preamble transmitted by the second UE in the LTM candidate cell while the second UE is being served by the source cell; or

[0155] • an indication from the second UE’s source RAN node (e.g., S-DU in Figures 4-6) that the UE will (or is configured to) perform early UL and / or DL synchronization with the LTM candidate cell.

[0156] Upon receiving either of the above, the RAN node either configures the first UE to use different cell resources or deactivates the first UE’s use of the cell resources needed by the second UE (e.g., in case the cell resources are a configured UL grant).

[0157] Although various embodiments described above involve resources that facilitate a RACH- less LTM cell switch to the LTM candidate cell when execution conditions are fulfilled, resources configured for and / or provided to the UE may also include one or more of the following: • State information for SCells associated with the LTM candidate cell (e.g., within a cell group for which the LTM candidate cell is PCell);

[0158] • TCI state information for one or more beams of the LTM candidate cell;

[0159] • TCI state information for one or more beams of SCells associated with the LTM candidate cell (within the same cell group);

[0160] • CFRA resources, e.g., dedicated PRACH preamble and / or time / frequency RA resources to be used by the UE for transmission in the LTM candidate cell during LTM cell switch;

[0161] • Two-step RA resources for performing a CFRA Two-step RA to the LTM candidate cell during LTM cell switch.

[0162] Various features of the embodiments described above correspond to various operations illustrated in Figures 7-9, which show exemplary methods (e.g, procedures) for a UE, a first RAN node, and a second RAN node, respectively. In other words, various features of the operations described below correspond to various embodiments described above. Furthermore, the exemplary methods shown in Figures 6-7 can be used cooperatively to provide various benefits, advantages, and / or solutions to problems described herein. Although Figures 6-7 show specific blocks in particular orders, the operations of the exemplary methods can be performed in different orders than shown and can be combined and / or divided into blocks having different functionality than shown. Optional blocks or operations are indicated by dashed lines.

[0163] In particular, Figure 7 shows an exemplary method (e.g., procedure) for a UE configured for conditional LTM in a RAN, according to various embodiments of the present disclosure. The exemplary method can be performed by a UE (e.g, wireless device) such as described elsewhere herein.

[0164] The exemplary method includes the operations of block 710, where the UE receives, from a first RAN node via a source cell, a configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled. The exemplary method also includes the operations of blocks 760-770, where in response to determining that the execution condition is fulfilled, the UE performs an LTM cell switch from the source cell to the LTM candidate cell, including selectively performing a random access (RA) to the LTM candidate cell based on whether the configured resources are activated.

[0165] In some embodiments, the first and second RAN nodes may be the same RAN node, such as a DU. This may be the case for an intra-DU LTM cell switch, as discussed above. In other embodiments, the first and second RAN nodes may be different RAN nodes, such as different DUs. This may be the case for an inter-DU LTM cell switch, as discussed above. In some embodiments, selectively performing a RA to the LTM candidate cell in block 770 includes the following operations, labelled with corresponding sub-block numbers:

[0166] • (771) when the configured resources are activated, refraining from performing a RA to the LTM candidate cell and performing the initial transmission in the LTM candidate cell using at least part of the configured resources; and

[0167] • (772) when the configured resources are not activated, performing a RA to the LTM candidate cell without using the configured resources.

[0168] In some embodiments, the configuration of resources include one or more of the following: one or more grants of UL resources, and an SR configuration. In some of these embodiments, the initial transmission using at least part of the configured resources is one of the following: an RRCReconflgurationComplete message using resources from an UL grant, or an SR using resources specified by the SR configuration.

[0169] In some embodiments, the exemplary method also includes the operations of block 720, where the UE receives, from the first RAN node or the second RAN node before the execution condition is fulfilled, an indication that the configured resources are activated. Selectively performing a RA to the LTM candidate cell in block 770 is based on the indication.

[0170] In some of these embodiments, the LTM candidate cell configuration and the execution condition are received in a first message, the configuration of resources is received in the first message (e.g., as in Figures 4 and 6) or in a second message after the first message (e.g., as in Figure 5), and the indication is included in (e.g., Figures 4 and 6) or implicit from the second message (e.g., Figure 5).

[0171] In some variants of these embodiments, the exemplary method also includes the operations of block 750, where the UE transmits a RA preamble towards the LTM candidate cell before the execution condition is fulfilled. Either the second message is received in response to the RA preamble or the RA preamble is transmitted in response to receiving the second message.

[0172] In some variants of these embodiments, the indication is implicit from one of the following included in the second message: the configuration, a TA value for the LTM candidate cell, a second indication that one or more TCI states of the LTM candidate cell are activated, or a PDCCH order for the LTM candidate cell. In some variants of these embodiments, the second message is one of the following: a MAC CE, a MAC PDU, DCI, or an RRC message. In some further variants, the second message is associated with one of the following: early UL synchronization of the UE with the LTM candidate cell or a second LTM candidate cell, and early DL synchronization of the UE with the LTM candidate cell or the second LTM candidate cell.

[0173] In some of these embodiments, the exemplary method also includes the operations of block 730, where the UE receives, from the first RAN node or the second RAN node before the execution condition is fulfilled, a further indication that the configured resources are deactivated. Selectively performing a RA to the LTM candidate cell in block 770 is also based on the further indication.

[0174] In some of these embodiments, selectively performing a RA to the LTM candidate cell in block 770 is further based on a validity duration included in the first message or the second message. In some variants of these embodiments, the validity duration is associated with one of the following included in the second message: the configuration of resources, the indication, or a timing advance (TA) value for the LTM candidate cell that is included in the second message.

[0175] In some variants of these embodiments, the exemplary method also includes the operations of block 740, where the UE initiates a timer associated with the validity duration upon receiving the configuration of resources (e.g., in block 710) or the indication (e.g., in block 720). Selectively performing the RA to the LTM candidate cell in block 770 is further based on whether the timer has expired when the execution condition is fulfilled.

[0176] In some embodiments, determining that the execution condition is fulfilled in block 760 is based on measurements of one or more DL RS of the LTM candidate cell.

[0177] In some embodiments, the first RAN node is a first DU (e.g., S-DU in Figures 4-6), the second RAN node is a second DU (e.g., C-DU in Figures 4-6), and the third RAN node is a CU associated with the first and second DUs.

[0178] In addition, Figure 8 shows an exemplary method (e.g., procedure) for a first RAN node configured to facilitate conditional LTM for UEs, according to various embodiments of the present disclosure. The exemplary method can be performed by any appropriate RAN node (e.g., base station, eNB, gNB, ng-eNB, DU, etc.) such as described elsewhere herein.

[0179] The exemplary method includes the operations of block 820, where the first RAN node sends the following information to a UE via a source cell provided by the first RAN node: a configuration for an LTM candidate cell provided by the first RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled. The exemplary method also includes the operations of block 840, where the first RAN node sends, to the UE before the execution condition is fulfilled, an indication that the configured resources are activated.

[0180] In some embodiments, the configuration of resources include one or more of the following: one or more grants of UL resources, and an SR configuration. In some embodiments, the LTM candidate cell configuration and the execution condition are sent in a first message, the configuration of resources is sent in the first message or in a second message after the first message, and the indication is implicit from or included in the second message. In some of these embodiments, the indication is implicit from one of the following included in the second message: the configuration, a TA value for the LTM candidate cell, a second indication that one or more TCI states of the LTM candidate cell are activated, or a PDCCH order for the LTM candidate cell. In some of these embodiments, the second message is one of the following: a MAC CE, a MAC PDU, DCI, or an RRC message.

[0181] In some of these embodiments, the second message is associated with one of the following: early UL synchronization of the UE with the LTM candidate cell or a second LTM candidate cell, or early DL synchronization of the UE with the LTM candidate cell or the second LTM candidate cell. In some of these embodiments, the first message or the second message includes a validity duration that is associated with one of the following included in the second message: the configuration of resources, the indication, or a TA value for the LTM candidate cell that is included in the second message.

[0182] In some of these embodiments, the exemplary method also includes the operations of block 810, where the first RAN node receives the LTM candidate cell configuration and the configuration of resources from one of the following: the second RAN node, or a third RAN node associated with the first RAN node and with the second RAN node. For example, the first RAN node may determine the execution condition that it sends to the UE together with the LTM candidate cell configuration and the configuration of resources received in block 810.

[0183] In some variants of these embodiments, the first RAN node is a first DU (e.g., S-DU in Figures 4-6), the second RAN node is a second DU (e.g., C-DU in Figures 4-6), and the third RAN node is a CU associated with the first and second DUs.

[0184] In some variants of these embodiments, the LTM candidate cell configuration is received in a third message before the first message, and one of the following applies:

[0185] • the configuration of resources is received in the third message and sent in the first message (e.g., as in Figures 4 and 6); or

[0186] • the configuration of resources is received in a fourth message after the third message and sent in the second message (e.g., as in Figure 5).

[0187] In some further variants, when the configuration of resources is received in the third message and sent in the first message (e.g., Figures 4 and 6), the indication is sent in the second message and the exemplary method also includes one of the following operations:

[0188] • (830) receiving the indication from the second or third RAN node in the fourth message that is after the third message but before the second message; or

[0189] • (860) sending, to the second or third RAN node, a request or command for the configured resources in the LTM candidate cell to be activated for the UE.

[0190] In some embodiments, the exemplary method also includes the operations of block 850, where the first RAN node sends, to the UE before the execution condition is fulfilled, a further indication that the configured resources in the LTM candidate cell are deactivated for the UE.

[0191] In addition, Figure 9 shows an exemplary method (e.g., procedure) for a second RAN node configured to facilitate conditional LTM for UEs, according to various embodiments of the present disclosure. The exemplary method can be performed by any appropriate RAN node (e.g., base station, eNB, gNB, ng-eNB, CU, DU, etc.) such as described elsewhere herein.

[0192] The exemplary method includes the operations of block 910, where the second RAN node sends the following information to a first RAN node that provides a source cell for a UE or to a third RAN node associated with the first and second RAN nodes: a configuration for an LTM candidate cell provided by the second RAN node, and a configuration of resources for an initial transmission by the UE in the LTM candidate cell after a configured execution condition is fulfilled. The exemplary method also includes the operations of block 970, where the second RAN node selectively activates or deactivates the configured resources for the UE in the LTM candidate cell. The exemplary method also includes the operations of block 980, where the second RAN subsequently facilitates an LTM cell switch by the UE from the source cell to the LTM candidate cell when the configured execution condition is fulfilled, including selectively receiving an initial transmission by the UE in the LTM candidate cell based on whether the configured resources are activated for the UE.

[0193] In some embodiments, selectively receiving an initial transmission by the UE in the LTM candidate cell in block 980 includes the following operations, labelled with corresponding subblock numbers:

[0194] • (981) when the configured resources are activated, receiving the initial transmission by the UE in the LTM candidate cell using at least part of the configured resources; and

[0195] • (982) when the configured resources are not activated, receiving a random access (RA) preamble from the UE in the LTM candidate cell without using the configured resources. In some embodiments, selectively activating or deactivating the configured resources for the UE in the LTM candidate cell in block 970 includes the operations of sub-block 971, where the second RAN node activates the configured resources for the UE responsive to sending the configuration of resources to the first RAN node.

[0196] In other embodiments, the exemplary method also includes the following operations, labelled with corresponding block numbers:

[0197] • (950) receiving a RA preamble from the UE in the LTM candidate cell before the execution condition is fulfilled; and

[0198] • (960) sending to the first or third RAN node a TA value for the UE in the LTM candidate cell, based on the received RA preamble. In some of these embodiments, selectively activating or deactivating the configured resources for the UE in the LTM candidate cell in block 970 includes the operations of sub-block 972, where the second RAN node activates the configured resources for the UE in response to receiving the RA preamble in block 950. An indication that the configured resources in the LTM candidate cell are activated for the UE is included with the TA value in block 960. Figure 4 shows an example of these embodiments.

[0199] In other of these embodiments, the exemplary method also includes the operations of block 940, where the second RAN node subsequently receives, from the first or third RAN node, a request or command for the configured resources in the LTM candidate cell to be activated for the UE. In such embodiments, selectively activating or deactivating the configured resources for the UE in the LTM candidate cell in block 970 includes the operations of sub-block 973, where the second RAN node activates the configured resources for the UE in response to the request or command from the first or third RAN node. Figure 6 shows an example of these embodiments.

[0200] In some embodiments, the resources configured for the UE in the LTM candidate cell are also configured for one or more of the following: a second UE configured with a further execution condition for LTM cell switch to the LTM candidate cell, and a third UE currently being served by second RAN node via the LTM candidate cell. In some of these embodiments, selectively activating or deactivating the configured resources for the UE in the LTM candidate cell in block 970 includes the operations of sub-block 974, where the second RAN node deactivates the configured resources for the UE in response to one of the following operations, labelled with corresponding block numbers:

[0201] • (920) receiving a RA preamble from the second UE in the LTM candidate cell before the further execution condition is fulfilled, or

[0202] • (940) determining that the third UE requires the configured resources.

[0203] In some embodiments, the first RAN node is a first DU (e.g., S-DU in Figures 4-6), the second RAN node is a second DU (e.g., C-DU in Figures 4-6), and the third RAN node is a CU associated with the first and second DUs.

[0204] 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.

[0205] Figure 10 shows an example of a communication system 1000 in accordance with some embodiments. In this example, communication system 1000 includes a telecommunication network 1002 that includes an access network 1004 (e.g., RAN) and a core network 1006, which includes one or more core network nodes 1008. Access network 1004 includes one or more access network nodes, such as network nodes lOlOa-b (one or more of which may be generally referred to as network nodes 1010), or any other similar 3GPP access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, telecommunication network 1002 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in telecommunication network 1002 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in telecommunication network 1002, including one or more network nodes 1010 and / or core network nodes 1008.

[0206] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU- CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e. g. , r App), or any combination thereof (the adj ective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. Network nodes 1010 facilitate direct or indirect connection of UEs, such as by connecting UEs 1012a-d (one or more of which may be generally referred to as UEs 1012) to core network 1006 over one or more wireless connections.

[0207] 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, communication system 1000 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. Communication system 1000 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0208] UEs 1012 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with network nodes 1010 and other communication devices. Similarly, network nodes 1010 are arranged, capable, configured, and / or operable to communicate directly or indirectly with UEs 1012 and / or with other network nodes or equipment in telecommunication network 1002 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in telecommunication network 1002.

[0209] In the depicted example, core network 1006 connects network nodes 1010 to one or more hosts, such as host 1016. 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. Core network 1006 includes one or more core network nodes (e.g., 1008) 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 core network node 1008. 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).

[0210] Host 1016 may be under the ownership or control of a service provider other than an operator or provider of access network 1004 and / or telecommunication network 1002, and may be operated by the service provider or on behalf of the service provider. Host 1016 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.

[0211] As a whole, communication system 1000 of Figure 10 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.

[0212] In some examples, telecommunication network 1002 is a cellular network that implements 3GPP standardized features. Accordingly, telecommunication network 1002 may support network slicing to provide different logical networks to different devices that are connected to telecommunication network 1002. For example, telecommunication network 1002 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.

[0213] In some examples, UEs 1012 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 1004 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 1004. 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).

[0214] In the example, hub 1014 communicates with access network 1004 to facilitate indirect communication between one or more UEs (e.g., 1012c and / or 1012d) and network nodes (e.g., 1010b). In some examples, hub 1014 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 1014 may be a broadband router enabling access to core network 1006 for the UEs. As another example, hub 1014 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 1010, or by executable code, script, process, or other instructions in hub 1014. As another example, hub 1014 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, hub 1014 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, hub 1014 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 1014 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, hub 1014 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0215] Hub 1014 may have a constant / persistent or intermittent connection to network node 1010b. Hub 1014 may also allow for a different communication scheme and / or schedule between hub 1014 and UEs (e.g., 1012c and / or 1012d), and between hub 1014 and core network 1006. In other examples, hub 1014 is connected to core network 1006 and / or one or more UEs via a wired connection. Moreover, hub 1014 may be configured to connect to an M2M service provider over access network 1004 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with network nodes 1010 while still connected via hub 1014 via a wired or wireless connection. In some embodiments, hub 1014 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to network node 1010b. In other embodiments, hub 1014 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1010b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0216] In some embodiments, any of UEs 1012 may be configured to perform operations attributed to a UE in various methods or procedures described above, including the exemplary method shown in Figure 7. In some embodiments, any of network nodes 1010 may be configured to perform operations attributed to a RAN node in various methods or procedures described above, including the exemplary methods shown in Figures 8-9.

[0217] Figure 11 shows a UE 1100 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), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by 3GPP, including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0218] 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).

[0219] UE 1100 includes processing circuitry 1102 that is operatively coupled via a bus 1104 to an input / output interface 1106, a power source 1108, a memory 1110, a communication interface 1112, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure 11. 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.

[0220] Processing circuitry 1102 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 memory 1110. Processing circuitry 1102 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, processing circuitry 1102 may include multiple central processing units (CPUs).

[0221] In the example, input / output interface 1106 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 UE 1100. 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.

[0222] In some embodiments, power source 1108 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. Power source 1108 may further include power circuitry for delivering power from power source 1108 itself, and / or an external power source, to the various parts of UE 1100 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging power source 1108. Power circuitry may perform any formatting, converting, or other modification to the power from power source 1108 to make the power suitable for the respective components of UE 1100 to which power is supplied.

[0223] Memory 1110 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, memory 1110 includes one or more application programs 1114, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1116. Memory 1110 may store, for use by UE 1100, any of a variety of various operating systems or combinations of operating systems.

[0224] Memory 1110 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.’ Memory 1110 may allow UE 1100 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 memory 1110, which may be or comprise a device-readable storage medium.

[0225] Processing circuitry 1102 may be configured to communicate with an access network or other network using communication interface 1112. Communication interface 1112 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1122. Communication interface 1112 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 1118 and / or a receiver 1120 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, transmitter 1118 and receiver 1120 may be coupled to one or more antennas (e.g., antenna 1122) and may share circuit components, software, or firmware, or alternatively be implemented separately.

[0226] In the illustrated embodiment, communication functions of communication interface 1112 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / intemet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0227] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1112, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0228] 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.

[0229] 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 UE 1100 shown in Figure 11.

[0230] 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 3GPP 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.

[0231] 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.

[0232] In some embodiments, UE 1100 may be configured to perform operations attributed to a UE in various methods or procedures described above, including the exemplary method shown in Figure 7.

[0233] Figure 12 shows a network node 1200 in accordance with some embodiments. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (e.g., radio base stations, Node Bs, eNBs, gNBs), and O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU).

[0234] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0235] 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).

[0236] Network node 1200 includes processing circuitry 1202, memory 1204, communication interface 1206, and power source 1208. Network node 1200 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 network node 1200 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, network node 1200 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1204 for different RATs) and some components may be reused (e.g., a same antenna 1210 may be shared by different RATs). Network node 1200 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1200, 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 1200.

[0237] Processing circuitry 1202 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 1200 components, such as memory 1204, to provide network node 1200 functionality. In some embodiments, processing circuitry 1202 includes a system on a chip (SOC). In some embodiments, processing circuitry 1202 includes one or more of radio frequency (RF) transceiver circuitry 1212 and baseband processing circuitry 1214. In some embodiments, RF transceiver circuitry 1212 and baseband processing circuitry 1214 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 1212 and baseband processing circuitry 1214 may be on the same chip or set of chips, boards, or units.

[0238] Memory 1204 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 processing circuitry 1202. Memory 1204 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 1204a, which may be in the form of a computer program product) capable of being executed by processing circuitry 1202 and utilized by network node 1200. Memory 1204 may be used to store any calculations made by processing circuitry 1202 and / or any data received via communication interface 1206. In some embodiments, processing circuitry 1202 and memory 1204 is integrated.

[0239] Communication interface 1206 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, communication interface 1206 comprises port(s) / terminal(s) 1216 to send and receive data, for example to and from a network over a wired connection. Communication interface 1206 also includes radio frontend circuitry 1218 that may be coupled to, or in certain embodiments a part of, antenna 1210. Radio front-end circuitry 1218 comprises filters 1220 and amplifiers 1222. Radio front-end circuitry 1218 may be connected to an antenna 1210 and processing circuitry 1202. The radio front-end circuitry may be configured to condition signals communicated between antenna 1210 and processing circuitry 1202. Radio front-end circuitry 1218 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. Radio front-end circuitry 1218 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1220 and / or amplifiers 1222. The radio signal may then be transmitted via antenna 1210. Similarly, when receiving data, antenna 1210 may collect radio signals which are then converted into digital data by radio front-end circuitry 1218. The digital data may be passed to processing circuitry 1202. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0240] In certain alternative embodiments, network node 1200 does not include separate radio front-end circuitry 1218, instead, processing circuitry 1202 includes radio front-end circuitry and is connected to antenna 1210. Similarly, in some embodiments, all or some of RF transceiver circuitry 1212 is part of communication interface 1206. In still other embodiments, communication interface 1206 includes one or more ports or terminals 1216, radio front-end circuitry 1218, and RF transceiver circuitry 1212, as part of a radio unit (not shown), and communication interface 1206 communicates with baseband processing circuitry 1214, which is part of a digital unit (not shown).

[0241] Antenna 1210 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. Antenna 1210 may be coupled to radio front-end circuitry 1218 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, antenna 1210 is separate from network node 1200 and connectable to network node 1200 through an interface or port.

[0242] Antenna 1210, communication interface 1206, and / or processing circuitry 1202 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, antenna 1210, communication interface 1206, and / or processing circuitry 1202 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.

[0243] Power source 1208 provides power to the various components of network node 1200 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 1208 may further comprise, or be coupled to, power management circuitry to supply the components of network node 1200 with power for performing the functionality described herein. For example, network node 1200 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 power source 1208. As a further example, power source 1208 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.

[0244] Embodiments of network node 1200 may include additional components beyond those shown in Figure 12 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, network node 1200 may include user interface equipment to allow input of information into network node 1200 and to allow output of information from network node 1200. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 1200.

[0245] In some embodiments, network node 1200 may be configured to perform operations attributed to a RAN node in various methods or procedures described above, including the exemplary methods shown in Figures 8-9.

[0246] Figure 13 is a block diagram illustrating a virtualization environment 1300 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 1300 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 1300 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface.

[0247] Applications 1302 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1300 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein. For example, In some embodiments, one or more virtual nodes 1302 may be configured to perform operations attributed to a RAN node in various methods or procedures described above, including the exemplary methods shown in Figures 8-9.

[0248] Hardware 1304 includes processing circuitry, memory that stores software and / or instructions (collectively denoted computer program 1304a, which may be in the form of a computer program product) 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 1306 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1308a-1308b (one or more of which may be generally referred to as VMs 1308), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. Virtualization layer 1306 may present a virtual operating platform that appears like networking hardware to the VMs 1308.

[0249] VMs 1308 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1306. Different embodiments of the instance of a virtual appliance 1302 may be implemented on one or more of VMs 1308, 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.

[0250] In the context of NFV, each VM 1308 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 1308, and that part of hardware 1304 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 1308 on top of the hardware 1304 and corresponds to the application 1302.

[0251] Hardware 1304 may be implemented in a standalone network node with generic or specific components. Hardware 1304 may implement some functions via virtualization. Alternatively, hardware 1304 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 function 1310, which, among others, oversees lifecycle management of applications 1302. In some embodiments, hardware 1304 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 1312 which may alternatively be used for communication between hardware nodes and radio units.

[0252] 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.

[0253] 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.

[0254] 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 to one or more embodiments of the present disclosure.

[0255] 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.

[0256] 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.

[0257] 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 such terms may be used synonymously herein, there may be instances when such terms are not intended to be used synonymously.

[0258] Embodiments of the techniques and apparatus described herein also include, but are not limited to, the following enumerated examples:

[0259] Al. A method for a user equipment (UE) configured for conditional 1 ay er- 1 / layer-2 triggered inter-cell mobility (LTM) in a radio access network (RAN), the method comprising: receiving the following information from a first RAN node via a source cell: a configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; in response to determining that the execution condition is fulfilled, performing an LTM cell switch from the source cell to the LTM candidate cell, including selectively performing a random access (RA) to the LTM candidate cell based on whether the configured resources are activated.

[0260] Ala. The method of embodiment Al, wherein selectively performing a RA to the LTM candidate cell comprises: when the configured resources are activated, refraining from performing a RA to the

[0261] LTM candidate cell and performing the initial transmission in the LTM candidate cell using at least part of the configured resources; and when the configured resources are not activated, performing a RA to the LTM candidate cell without using the configured resources.

[0262] A2. The method of any of embodiments Al -Al a, wherein the configuration of resources include one or more of the following: one or more grants of uplink (UL) resources, and a scheduling request (SR) configuration. A2a. The method of embodiment A2, wherein the initial transmission using at least part of the configured resources is one of the following: an RRCReconflgurationComplete message using resources from an UL grant, or an SR using resources specified by the SR configuration.

[0263] A3. The method of any of embodiments A2-A2a, further comprising receiving, from the first RAN node or the second RAN node before the execution condition is fulfilled, an indication that the configured resources are activated, wherein selectively performing a RA to the LTM candidate cell is based on the indication.

[0264] A3a. The method of embodiment A3, wherein: the LTM candidate cell configuration and the execution condition are received in a first message, the configuration of resources is received in the first message or in a second message after the first message, and the indication is implicit from or included in the second message.

[0265] A3b. The method of embodiment A3a, further comprising transmitting a RA preamble towards the LTM candidate cell before the execution condition is fulfilled, wherein one of the following applies: the second message is received in response to the RA preamble, or the RA preamble is transmitted in response to receiving the second message.

[0266] A3c. The method of any of embodiments A3a-A3b, wherein the indication is implicit from one of the following included in the second message: the configuration, a timing advance (TA) value for the LTM candidate cell, a second indication that one or more transmission configuration indicator (TCI) states of the LTM candidate cell are activated, or a physical downlink control channel (PDCCH) order for the LTM candidate cell.

[0267] A3d. The method of any of embodiments A3a-A3c, wherein the second message is one of the following: a medium access control (MAC) control element (CE), a MAC protocol data unit (PDU), downlink control information (DCI), or a radio resource control (RRC) message.

[0268] A3e. The method of embodiments A3a-A3d, wherein the second message is associated with one of the following: early uplink (UL) synchronization of the UE with the LTM candidate cell or a second LTM candidate cell, or early downlink (DL) synchronization of the UE with the LTM candidate cell or the second LTM candidate cell. A3f. The method of any of embodiments A3-A3e, further comprising receiving, from the first RAN node or the second RAN node before the execution condition is fulfilled, a further indication that the configured resources are deactivated, wherein selectively performing a RA to the LTM candidate cell is also based on the further indication.

[0269] A3g. The method of any of embodiments A3-A3f wherein selectively performing a RA to the LTM candidate cell is further based on a validity duration included in the first message or the second message.

[0270] A3h. The method of embodiment A3g, further comprising initiating a timer associated with the validity duration upon receiving the configuration of resources or the indication, wherein selectively performing the RA to the LTM candidate cell is further based on whether the timer has expired when the execution condition is fulfilled.

[0271] A3i. The method of any of embodiments A3g-A3h, wherein the validity duration is associated with one of the following included in the second message: the configuration of resources, the indication, or a timing advance (TA) value for the LTM candidate cell that is included in the second message.

[0272] A4. The method of any of embodiments Al-A3i, wherein determining that the execution condition is fulfilled is based on measurements of one or more downlink (DL) reference signals (RS) of the LTM candidate cell.

[0273] BL A method for a first radio access network (RAN) node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), the method comprising: sending the following information to a UE via a source cell provided by the first RAN node: a configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; sending, to the UE before the execution condition is fulfilled, an indication that the configured resources are activated.

[0274] B2. The method of any of embodiments Bl -Bl a, wherein the configuration of resources include one or more of the following: one or more grants of uplink (UL) resources, and a scheduling request (SR) configuration.

[0275] B3. The method of any of embodiments B1-B2, wherein: the LTM candidate cell configuration and the execution condition are sent in a first message, the configuration of resources is sent in the first message or in a second message after the first message, and the indication is implicit from or included in the second message.

[0276] B3a. The method of embodiment B3, wherein the indication is implicit from one of the following included in the second message: the configuration, a timing advance (TA) value for the LTM candidate cell, a second indication that one or more transmission configuration indicator (TCI) states of the LTM candidate cell are activated, or a physical downlink control channel (PDCCH) order for the LTM candidate cell.

[0277] B3b. The method of any of embodiments B3-B3a, wherein the second message is one of the following: a medium access control (MAC) control element (CE), a MAC protocol data unit (PDU), downlink control information (DCI), or a radio resource control (RRC) message.

[0278] B3c. The method of embodiments B3-B3b, wherein the second message is associated with one of the following: early uplink (UL) synchronization of the UE with the LTM candidate cell or a second LTM candidate cell, or early downlink (DL) synchronization of the UE with the LTM candidate cell or the second LTM candidate cell.

[0279] B3d. The method of any of embodiments B3-B3c, wherein the first message or the second message includes a validity duration that is associated with one of the following included in the second message: the configuration of resources, the indication, or a timing advance (TA) value for the LTM candidate cell that is included in the second message..

[0280] B3e. The method of any of embodiments B3-B3d, further comprising receiving the LTM candidate cell configuration, the execution condition, and the configuration of resources from one of the following: the second RAN node, or a third RAN node associated with the first RAN node and with the second RAN node.

[0281] B3f The method of embodiment B3e, wherein the first RAN node is a first distributed unit (DU), the second RAN node is a second DU, and the third RAN node is a centralized unit (CU) associated with the first and second DUs.

[0282] B3g. The method of any of embodiments B3e-B3f, wherein the LTM candidate cell configuration and the execution condition are received in a third message before the first message, and one of the following applies: the configuration of resources is received in the third message and sent in the first message, or the configuration of resources is received in a fourth message after the third message and sent in the second message.

[0283] B3h. The method of embodiment B3g, wherein when the configuration of resources is received in the third message and sent in the first message, the indication is sent in the second message and the method further comprises one of the following: receiving the indication from the second or third RAN node in the fourth message that is after the third message but before the second message; or sending, to the second or third RAN node, a request or command for the configured resources in the LTM candidate cell to be activated for the UE.

[0284] B4. The method of any of embodiments Bl-B3h, further comprising sending, to the UE before the execution condition is fulfilled, a further indication that the configured resources in the LTM candidate cell are deactivated for the UE.

[0285] CL A method for a second radio access network (RAN) node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), the method comprising: sending the following information to a first RAN node that provides a source cell for a UE or to a third RAN node associated with the first and second RAN nodes: a configuration for an LTM candidate cell provided by the second RAN node, an execution condition for LTM cell switch by the UE to the LTM candidate cell, and a configuration of resources for an initial transmission by the UE in the LTM candidate cell after the execution condition is fulfilled; selectively activating or deactivating the configured resources for the UE in the LTM candidate cell; and subsequently facilitating an LTM cell switch by the UE from the source cell to the LTM candidate cell when the execution condition is fulfilled, including selectively receiving an initial transmission by the UE in the LTM candidate cell based on whether the configured resources are activated for the UE.

[0286] Cl a. The method of embodiment Cl, wherein selectively receiving an initial transmission by the UE in the LTM candidate cell comprises: when the configured resources are activated, receiving the initial transmission by the UE in the LTM candidate cell using at least part of the configured resources; and when the configured resources are not activated, receiving a random access (RA) preamble from the UE in the LTM candidate cell without using the configured resources.

[0287] C2. The method of any of embodiments Cl -Cl a, wherein the configured resources are activated for the UE in the LTM candidate cell responsive to sending the configuration of resources to the first RAN node.

[0288] C3. The method of any of embodiments Cl -Cl a, further comprising: receiving a random access (RA) preamble from the UE in the LTM candidate cell before the execution condition is fulfilled; and sending to the first or third RAN node a timing advance (TA) value for the UE in the LTM candidate cell, based on the received RA preamble.

[0289] C3a. The method of embodiment C3, wherein the configured resources are activated for the UE in response to receiving the RA preamble, and an indication that the configured resources in the LTM candidate cell are activated for the UE is included with the TA value.

[0290] C3b. The method of embodiment C3, further comprising subsequently receiving from the first or third RAN node, a request or command for the configured resources in the LTM candidate cell to be activated for the UE, wherein the configured resources are activated for the UE in response to the request or command. C4. The method of any of embodiments Cl-C3b, wherein the resources configured for the UE in the LTM candidate cell are also configured for one or more of the following: a second UE configured with a further execution condition for LTM cell switch to the LTM candidate cell, and a third UE currently being served by second RAN node via the LTM candidate cell.

[0291] C4a. The method of embodiment C4, wherein the configured resources are deactivated for the UE in the LTM candidate cell in response to one of the following: receiving a RA preamble from the second UE in the LTM candidate cell before the further execution condition is fulfilled, or determining that the third UE requires the configured resources.

[0292] C5. The method of any of embodiments Cl-C4a, wherein the first RAN node is a first distributed unit (DU), the second RAN node is a second DU, and the third RAN node is a centralized unit (CU) associated with the first and second DUs.

[0293] DI. A user equipment (UE) configured for conditional 1 ay er- 1 / layer-2 triggered inter-cell mobility (LTM) in a radio access network (RAN), the UE comprising: communication interface circuitry configured to communicate with RAN nodes; and processing circuitry operatively coupled to the communication interface circuitry, whereby the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the methods of any of embodiments A1-A4.

[0294] D2. A user equipment (UE) configured for conditional 1 ay er- 1 / layer-2 triggered inter-cell mobility (LTM) in a radio access network (RAN), the UE being further configured to perform operations corresponding to the methods of any of embodiments A1-A4.

[0295] D3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a user equipment (UE) configured for conditional layer-l / layer-2 triggered inter-cell mobility (LTM) in a radio access network (RAN), configure the UE to perform operations corresponding to the methods of any of embodiments A1-A4.

[0296] D4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of user equipment (UE) configured for conditional layer- l / layer-2 triggered inter-cell mobility (LTM) in a radio access network (RAN), configure the UE to perform operations corresponding to the methods of any of embodiments A1-A4.

[0297] El . A first radio access network (RAN) node configured to facilitate conditional layer- l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), the first RAN node comprising: communication interface circuitry configured to communicate with UEs and with other RAN nodes; and processing circuitry operatively coupled to the communication interface circuitry, whereby the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the methods of any of embodiments B1-B4.

[0298] E2. A first radio access network (RAN) node configured to facilitate conditional layer- l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), the first RAN node being further configured to perform operations corresponding to the methods of any of embodiments B1-B4.

[0299] E3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a first radio access network (RAN) node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), configure the first RAN node to perform operations corresponding to the methods of any of embodiments B1-B4.

[0300] E4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a first radio access network (RAN) node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), configure the first RAN node to perform operations corresponding to the methods of any of embodiments B1-B4.

[0301] FL A second radio access network (RAN) node configured to facilitate conditional layer- l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), the second RAN node comprising: communication interface circuitry configured to communicate with UEs and with other RAN nodes; and processing circuitry operatively coupled to the communication interface circuitry, whereby the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the methods of any of embodiments C1-C5.

[0302] F2. A second radio access network (RAN) node configured to facilitate conditional layer- l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), the second RAN node being further configured to perform operations corresponding to the methods of any of embodiments C1-C5.

[0303] F3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a second radio access network (RAN) node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), configure the second RAN node to perform operations corresponding to the methods of any of embodiments C1-C5.

[0304] F4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a second radio access network (RAN) node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility (LTM) by user equipment (UEs), configure the second RAN node to perform operations corresponding to the methods of any of embodiments C1-C5.

Claims

CLAIMS1. A method for a user equipment, UE, configured for conditional layer-l / layer-2 triggered inter-cell mobility, LTM, in a radio access network, RAN, the method comprising: receiving (710) the following information from a first RAN node via a source cell: a configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; in response to determining (760) that the execution condition is fulfilled, performing (770) an LTM cell switch from the source cell to the LTM candidate cell, including selectively performing a random access, RA, to the LTM candidate cell based on whether the configured resources are activated.

2. The method of claim 1, wherein selectively performing a RA to the LTM candidate cell comprises: when the configured resources are activated, refraining (771) from performing a RA to the LTM candidate cell and performing the initial transmission in the LTM candidate cell using at least part of the configured resources; and when the configured resources are not activated, performing (772) a RA to the LTM candidate cell without using the configured resources.

3. The method of any of claims 1-2, wherein the configuration of resources include one or more of the following: one or more grants of uplink, UL, resources; and a scheduling request, SR, configuration.

4. The method of claim 3, wherein the initial transmission using at least part of the configured resources is one of the following: an RRCReconflgurationComplete message using resources from an UL grant, or an SR using resources specified by the SR configuration.

5. The method of any of claims 1-4, further comprising receiving (720), from the first RAN node or the second RAN node before the execution condition is fulfilled, an indication that the configured resources are activated, wherein selectively performing a RA to the LTM candidate cell is based on the indication.

6. The method of claim 5, wherein: the LTM candidate cell configuration and the execution condition are received in a first message, the configuration of resources is received in the first message or in a second message after the first message, and the indication is implicit from or included in the second message.

7. The method of claim 6, further comprising transmitting (750) a RA preamble towards the LTM candidate cell before the execution condition is fulfilled, wherein one of the following applies: the second message is received in response to the RA preamble, or the RA preamble is transmitted in response to receiving the second message.

8. The method of any of claims 6-7, wherein the indication is implicit from one of the following included in the second message: the configuration, a timing advance, TA, value for the LTM candidate cell, a second indication that one or more transmission configuration indicator, TCI, states of the LTM candidate cell are activated, or a physical downlink control channel, PDCCH, order for the LTM candidate cell.

9. The method of any of claims 6-8, wherein the second message is one of the following: a medium access control, MAC, control element, CE; a MAC protocol data unit, PDU; downlink control information, DCI; or a radio resource control, RRC, message.

10. The method of claims 6-9, wherein the second message is associated with one of the following: early uplink, UL, synchronization of the UE with the LTM candidate cell or a second LTM candidate cell; or early downlink, DL, synchronization of the UE with the LTM candidate cell or the second LTM candidate cell.

11. The method of any of claims 5-10, further comprising receiving (730), from the first RAN node or the second RAN node before the execution condition is fulfilled, a further indication that the configured resources are deactivated, wherein selectively performing a RA to the LTM candidate cell is also based on the further indication.

12. The method of any of claims 5-11, wherein selectively performing a RA to the LTM candidate cell is further based on a validity duration included in the first message or the second message.

13. The method of claim 12, further comprising initiating (740) a timer associated with the validity duration upon receiving the configuration of resources or the indication, wherein selectively performing the RA to the LTM candidate cell is further based on whether the timer has expired when the execution condition is fulfilled.

14. The method of any of claims 12-13, wherein the validity duration is associated with one of the following included in the second message: the configuration of resources, the indication, or a timing advance, TA, value for the LTM candidate cell.

15. The method of any of claims 1-14, wherein determining (760) that the execution condition is fulfilled is based on measurements of one or more downlink, DL, reference signals, RS, of the LTM candidate cell.

16. A method for a first radio access network, RAN, node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs, the method comprising: sending (820) the following information to a UE via a source cell provided by the first RAN node: a configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; sending (840), to the UE before the execution condition is fulfilled, an indication that the configured resources are activated.

17. The method of claim 16, wherein the configuration of resources include one or more of the following: one or more grants of uplink, UL, resources; and a scheduling request, SR, configuration.

18. The method of any of claims 16-17, wherein:the LTM candidate cell configuration and the execution condition are sent in a first message, the configuration of resources is sent in the first message or in a second message after the first message, and the indication is implicit from or included in the second message.

19. The method of claim 18, wherein the indication is implicit from one of the following included in the second message: the configuration, a timing advance, TA, value for the LTM candidate cell, a second indication that one or more transmission configuration indicator, TCI, states of the LTM candidate cell are activated, or a physical downlink control channel, PDCCH, order for the LTM candidate cell.

20. The method of any of claims 18-19, wherein the second message is one of the following: a medium access control, MAC, control element, CE; a MAC protocol data unit, PDU; downlink control information, DCI; or a radio resource control, RRC, message.

21. The method of claims 18-20, wherein the second message is associated with one of the following: early uplink, UL, synchronization of the UE with the LTM candidate cell or a second LTM candidate cell; or early downlink, DL, synchronization of the UE with the LTM candidate cell or the second LTM candidate cell.

22. The method of any of claims 18-21, wherein the first message or the second message includes a validity duration that is associated with one of the following included in the second message: the configuration of resources, the indication, or a timing advance, TA, value for the LTM candidate cell.

23. The method of any of claims 18-22, further comprising receiving (810) the LTM candidate cell configuration and the configuration of resources from one of the following: the second RAN node, or a third RAN node associated with the first and second RAN nodes.

24. The method of claim 23, wherein the first RAN node is a first distributed unit, DU„ the second RAN node is a second DU, and the third RAN node is a centralized unit, CU, associated with the first and second DUs.

25. The method of any of claims 23-24, wherein the LTM candidate cell configuration is received in a third message before the first message, and one of the following applies: the configuration of resources is received in the third message and sent in the first message, or the configuration of resources is received in a fourth message after the third message and sent in the second message.

26. The method of claim 25, wherein when the configuration of resources is received in the third message and sent in the first message, the indication is sent in the second message, and the method further comprises one of the following: receiving (830) the indication from the second or third RAN node in the fourth message that is after the third message but before the second message; or sending (860), to the second or third RAN node, a request or command for the configured resources in the LTM candidate cell to be activated for the UE.

27. The method of any of claims 16-26, further comprising, before the execution condition is fulfilled, sending (850) to the UE a further indication that the configured resources in the LTM candidate cell are deactivated for the UE.

28. A method for a second radio access network, RAN, node configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs, the method comprising: sending (910) the following information to a first RAN node that provides a source cell for a UE or to a third RAN node associated with the first and second RAN nodes: a configuration for an LTM candidate cell provided by the second RAN node, and a configuration of resources for an initial transmission by the UE in the LTM candidate cell after a configured execution condition is fulfilled; selectively activating or deactivating (970) the configured resources for the UE in the LTM candidate cell; and subsequently facilitating (980) an LTM cell switch by the UE from the source cell to the LTM candidate cell when the configured execution condition is fulfilled, including selectively receiving an initial transmission by the UE in the LTMcandidate cell based on whether the configured resources are activated for the UE.

29. The method of claim 28, wherein selectively receiving an initial transmission by the UE in the LTM candidate cell comprises: when the configured resources are activated, receiving (981) the initial transmission by the UE in the LTM candidate cell using at least part of the configured resources; and when the configured resources are not activated, receiving (982) a random access, RA, preamble from the UE in the LTM candidate cell without using the configured resources.

30. The method of any of claims 28-29, wherein selectively activating or deactivating (970) the configured resources for the UE in the LTM candidate cell comprises activating (971) the configured resources for the UE in response to sending (910) the configuration of resources to the first RAN node.

31. The method of any of claims 28-29, further comprising: receiving (950) a random access, RA, preamble from the UE in the LTM candidate cell before the configured execution condition is fulfilled; and sending (960) to the first or third RAN node a timing advance, TA, value for the UE in the LTM candidate cell, based on the received RA preamble.

32. The method of claim 31 , wherein: selectively activating or deactivating (970) the configured resources for the UE in the LTM candidate cell comprises activating (972) the configured resources in response to receiving the RA preamble; and an indication that the configured resources in the LTM candidate cell are activated for the UE is included with the TA value.

33. The method of claim 31 , wherein: the method further comprises subsequently receiving (940) from the first or third RAN node a request or command for the configured resources in the LTM candidate cell to be activated for the UE; andselectively activating or deactivating (970) the configured resources for the UE in the LTM candidate cell comprises activating (973) the configured resources in response to the request or command.

34. The method of any of claims 28-33, wherein the resources configured for the UE in the LTM candidate cell are also configured for one or more of the following: a second UE configured with a further execution condition for LTM cell switch to the LTM candidate cell, and a third UE currently being served by second RAN node via the LTM candidate cell.

35. The method of claim 34, wherein selectively activating or deactivating (970) the configured resources for the UE in the LTM candidate cell comprises deactivating (974) the configured resources for the UE in the LTM candidate cell in response to one of the following: receiving (920) a RA preamble from the second UE in the LTM candidate cell before the further execution condition is fulfilled, or determining (930) that the third UE requires the configured resources.

36. The method of any of claims 28-35, wherein the first RAN node is a first distributed unit, DU, the second RAN node is a second DU, and the third RAN node is a centralized unit, CU, associated with the first and second DUs.

37. User equipment, UE (210, 310, 410, 1012, 1100) configured for conditional layer- l / layer-2 triggered inter-cell mobility, LTM, in a radio access network, RAN (199, 1004), the UE comprising: communication interface circuitry (1112) configured to communicate with RAN nodes; and processing circuitry (1102) operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to: receive the following information from a first RAN node (100, 120, 220, 320, 420, 1010, 1200, 1302) via a source cell: a configuration for an LTM candidate cell provided by a second RAN node (100, 130, 220, 320, 440, 1010, 1200, 1302), an execution condition for LTM cell switch by a UE to the LTM candidate cell, anda configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; in response to a determination that the execution condition is fulfilled, perform an LTM cell switch from the source cell to the LTM candidate cell, including selectively performing a random access, RA, to the LTM candidate cell based on whether the configured resources are activated.

38. The UE of claim 37, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the methods of any of claims 2-15.

39. User equipment, UE (210, 310, 410, 1012, 1100) configured for conditional layer- l / layer-2 triggered inter-cell mobility, LTM, in a radio access network, RAN (199, 1004), the UE being further configured to: receive the following information from a first RAN node (100, 120, 220, 320, 420, 1010, 1200, 1302) via a source cell: a configuration for an LTM candidate cell provided by a second RAN node (100, 130, 220, 320, 440, 1010, 1200, 1302), an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; in response to a determination that the execution condition is fulfilled, perform an LTM cell switch from the source cell to the LTM candidate cell, including selectively performing a random access, RA, to the LTM candidate cell based on whether the configured resources are activated.

40. The UE of claim 39, being further configured to perform operations corresponding to the methods of any of claims 2-15.

41. Non-transitory, computer-readable medium (1110) storing computer-executable instructions that, when executed by processing circuitry (1102) of user equipment, UE (210, 310, 410, 1012, 1100) configured for conditional 1 ay er- 1 / layer-2 triggered inter-cell mobility, LTM, in a radio access network, RAN (199, 1004), configure the UE to perform operations corresponding to the methods of any of claims 1-15.

42. Computer program product (1114) comprising computer-executable instructions that, when executed by processing circuitry (1102) of user equipment, UE (210, 310, 410, 1012, 1100) configured for conditional 1 ay er- 1 / layer-2 triggered inter-cell mobility, LTM, in a radio access network, RAN (199, 1004), configure the UE to perform operations corresponding to the methods of any of claims 1-15.

43. First radio access network, RAN, node (100, 120, 220, 320, 420, 1010, 1200, 1302) configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), the first RAN node comprising: communication interface circuitry (1206, 1304) configured to communicate with UEs and with other RAN nodes; and processing circuitry (1202, 1304) operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to: send the following information to a UE via a source cell provided by the first RAN node: a configuration for an LTM candidate cell provided by a second RAN node, an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; send, to the UE before the execution condition is fulfilled, an indication that the configured resources are activated.

44. The first RAN node of claim 43, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the methods of any of claims 17-27.

45. First radio access network, RAN, node (100, 120, 220, 320, 420, 1010, 1200, 1302) configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), the first RAN node being further configured to: send the following information to a UE via a source cell provided by the first RAN node: a configuration for an LTM candidate cell provided by a second RAN node,an execution condition for LTM cell switch by a UE to the LTM candidate cell, and a configuration of resources for an initial transmission in the LTM candidate cell after the execution condition is fulfilled; send, to the UE before the execution condition is fulfilled, an indication that the configured resources are activated.

46. The first RAN node of claim 45, being further configured to perform operations corresponding to the methods of any of claims 17-27.

47. Non-transitory, computer-readable medium (1204, 1304) storing computer-executable instructions that, when executed by processing circuitry (1202, 1304) of a first radio access network, RAN, node (100, 120, 220, 320, 420, 1010, 1200, 1302) configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), configure the first RAN node to perform operations corresponding to the methods of any of claims 16-27.

48. Computer program product (1204a, 1304a) comprising computer-executable instructions that, when executed by processing circuitry (1202, 1304) of a first radio access network, RAN, node (100, 120, 220, 320, 420, 1010, 1200, 1302) configured to facilitate conditional layer- l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), configure the first RAN node to perform operations corresponding to the methods of any of claims 16-27.

49. Second radio access network, RAN, node (100, 130, 220, 320, 440, 1010, 1200, 1302) configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), the second RAN node comprising: communication interface circuitry (1206, 1304) configured to communicate with UEs and with other RAN nodes; and processing circuitry (1202, 1304) operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to: send the following information to a first RAN node (100, 120, 220, 320, 420, 1010, 1200, 1302) that provides a source cell for a UE or to a third RANnode (100, 110, 220, 320, 430, 1010, 1200, 1302) associated with the first and second RAN nodes: a configuration for an LTM candidate cell provided by the second RAN node, and a configuration of resources for an initial transmission by the UE in the LTM candidate cell after a configured execution condition is fulfilled; selectively activate or deactivate the configured resources for the UE in the LTM candidate cell; and subsequently facilitate an LTM cell switch by the UE from the source cell to the LTM candidate cell when the configured execution condition is fulfilled, including selective reception of an initial transmission by the UE in the LTM candidate cell based on whether the configured resources are activated for the UE.

50. The second RAN node of claim 49, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the methods of any of claims 29-36.

51. Second radio access network, RAN, node (100, 130, 220, 320, 440, 1010, 1200, 1302) configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), the second RAN node being further configured to: send the following information to a first RAN node (100, 120, 220, 320, 420, 1010, 1200, 1302) that provides a source cell for a UE or to a third RAN node (100, 110, 220, 320, 430, 1010, 1200, 1302) associated with the first and second RAN nodes: a configuration for an LTM candidate cell provided by the second RAN node, and a configuration of resources for an initial transmission by the UE in the LTM candidate cell after a configured execution condition is fulfilled; selectively activate or deactivate the configured resources for the UE in the LTM candidate cell; and subsequently facilitate an LTM cell switch by the UE from the source cell to the LTM candidate cell when the configured execution condition is fulfilled, includingselective reception of an initial transmission by the UE in the LTM candidate cell based on whether the configured resources are activated for the UE.

52. The second RAN node of claim 51, being further configured to perform operations corresponding to the methods of any of claims 29-36.

53. Non-transitory, computer-readable medium (1204, 1304) storing computer-executable instructions that, when executed by processing circuitry (1202, 1304) of a second radio access network, RAN, node (100, 130, 220, 320, 440, 1010, 1200, 1302) configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), configure the second RAN node to perform operations corresponding to the methods of any of claims 28-36.

54. Computer program product (1204a, 1304a) comprising computer-executable instructions that, when executed by processing circuitry (1202, 1304) of a second radio access network, RAN, node (100, 130, 220, 320, 440, 1010, 1200, 1302) configured to facilitate conditional layer-l / layer-2 triggered inter-cell mobility, LTM, by user equipment, UEs (210, 310, 410, 1012, 1100), configure the second RAN node to perform operations corresponding to the methods of any of claims 28-36.

Images