WO2025050684A1

WO2025050684A1 - Methods and apparatuses for an l1/l2-triggered mobility (ltm) procedure and a conditional handover (cho) procedure

Info

Publication number: WO2025050684A1
Application number: PCT/CN2024/091982
Authority: WO
Inventors: Lianhai WU; Shuigen Yang; Le Yan
Original assignee: Lenovo Beijing Ltd
Current assignee: Lenovo Beijing Ltd
Priority date: 2024-05-09
Filing date: 2024-05-09
Publication date: 2025-03-13
Anticipated expiration: 2026-11-09

Abstract

Various aspects of the present disclosure relate to methods and apparatuses for an L1/L2-Triggered Mobility (LTM) procedure and a conditional handover (CHO) procedure. According to an embodiment of the present disclosure, a master node (MN) includes at least one memory and at least one processor coupled to the at least one memory and configured to cause the MN to: receive, from a user equipment (UE), UE capability information related to L1/L2-Triggered Mobility (LTM); transmit a request for SN addition to a secondary node (SN), wherein the request for SN addition includes the UE capability information and a first identifier (ID) of the UE that is unique within the MN; receive, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN;and transmit, to the UE, configuration information related to the SN including the SCG configuration information.

Description

METHODS AND APPARATUSES FOR AN L1/L2-TRIGGERED MOBILITY (LTM) PROCEDURE AND A CONDITIONAL HANDOVER (CHO) PROCEDURE

TECHNICAL FIELD

The present disclosure relates to wireless communications, and more specifically to methods and apparatuses for an L1/L2-Triggered Mobility (LTM) procedure and a conditional handover (CHO) procedure. LTM may also be named as lower layer-Triggered Mobility or the like.

BACKGROUND

A wireless communications system may include one or multiple network communication devices, such as a base stations (BS) , which may support wireless communications for one or multiple user communication devices, which may be otherwise known as user equipment (UE) , or other suitable terminology. The wireless communications system may support wireless communications with one or multiple user communication devices by utilizing resources of the wireless communication system (e.g. time-domain resources (e.g. symbols, slots, subframes, frames, or the like) or frequency-domain resources (e.g. subcarriers, carriers, or the like) . Additionally, the wireless communications system may support wireless communications across various radio access technologies including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, among other suitable radio access technologies beyond 5G (e.g. sixth generation (6G) ) .

LTM is a procedure in which a network equipment (e.g. gNB) receives layer 1 (L1) measurement report (s) from a UE, and the network equipment (e.g. gNB) changes UE’s serving cell by an LTM cell switch command. LTM may also be named as a layer 1/layer 2 (L1/L2) lower layer-Triggered Mobility or the like. An LTM primary cell (PCell) switch procedure from a source cell (or source PCell) to a target cell (or target PCell) may also be named as a master cell group (MCG) LTM procedure. An LTM primary secondary cell group cell (PSCell) switch procedure from a source PSCell to a target PSCell may also be named as a secondary cell group (SCG) LTM procedure.

CHO is defined as a handover that is executed by a UE when CHO execution conditions for one or more handover are met. The UE starts evaluating the one or more CHO execution conditions upon receiving the CHO configuration information (e.g. including one or more configurations associated candidate PCell (s) and one or more CHO execution conditions) , and stops evaluating the CHO execution conditions during the CHO execution or once the one or more CHO execution conditions are met or fulfilled. The CHO execution means that when CHO execution condition (s) of a candidate PCell is satisfied or fulfilled, the UE decides the candidate PCell as a target PCell, and performs a PCell change or handover procedure with the target PCell, e.g. the UE performs a random access (RA) procedure towards the target PCell.

SUMMARY

An article "a" before an element is unrestricted and understood to refer to "at least one" of those elements or "one or more" of those elements. The terms "a, " "at least one, " "one or more, " and "at least one of one or more" may be interchangeable. As used herein, including in the claims, "or" as used in a list of items (e.g. a list of items prefaced by a phrase such as "at least one of" or "one or more of" or "one or both of" ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C) . Also, as used herein, the phrase "based on" shall not be construed as a reference to a closed set of conditions. For example, an example step that is described as "based on condition A" may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" shall be construed in the same manner as the phrase "based at least in part on. Further, as used herein, including in the claims, a "set" may include one or more elements.

Some implementations of the present disclosure provide a master node (MN) . The MN includes at least one memory; and at least one processor coupled to the at least one memory and configured to cause the MN to: receive, from a user equipment (UE) , UE capability information related to L1/L2-Triggered Mobility (LTM) ; transmit a request for SN addition to a secondary node (SN) , wherein the request for SN addition includes the UE capability information and a first identifier (ID) of the UE that is unique within the MN; receive, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN; and transmit, to the UE, configuration information related to the SN including the SCG configuration information.

In some implementations of the MN described herein, the UE capability information indicates that the UE supports an inter-centralized unit (CU) LTM.

In some implementations of the MN described herein, the at least one processor is configured to cause the MN to transmit, to the SN, one of the following: an inter-CU master cell group (MCG) LTM is configured for the UE; inter-CU SCG LTM configuration information is not allowed to be configured for the UE; or an inter-CU SCG LTM is not allowed.

In some implementations of the MN described herein, if the MN configures the UE to release configuration information for inter-CU MCG LTM, the at least one processor is configured to cause the MN to transmit, to the SN, one of the following: the configuration information for inter-CU MCG LTM is released; the inter-CU MCG LTM is not configured for the UE; or the inter-CU SCG LTM is allowed.

In some implementations of the MN described herein, the at least one processor is configured to cause the MN to receive, from the SN, a request message including SCG LTM configuration.

In some implementations of the MN described herein, the at least one processor is configured to cause the MN to transmit, to the SN, a first message for refusing the request message.

In some implementations of the MN described herein, the first message includes one of the following: an inter-CU MCG LTM is configured for the UE; or inter-CU SCG LTM configuration information is not allowed to be configured for the UE; or an inter-CU SCG LTM is not allowed.

In some implementations of the MN described herein, the first message is an SN modification refuse message.

Some implementations of the present disclosure provide a processor for wireless communication, comprising at least one controller coupled with at least one memory and configured to cause the processor to: receive, from a user equipment (UE) , UE capability information related to L1/L2-Triggered Mobility (LTM) ; transmit a request for SN addition to a secondary node (SN) , wherein the request for SN addition includes the UE capability information and a first identifier (ID) of the UE that is unique within the MN; receive, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN; and transmit, to the UE, configuration information related to the SN including the SCG configuration information.

Some implementations of the present disclosure provide a method performed by a master node (MN) . The method includes: receiving, from a user equipment (UE) , UE capability information related to L1/L2-Triggered Mobility (LTM) ; transmitting a request for SN addition to a secondary node (SN) , wherein the request for SN addition includes the UE capability information and a first identifier (ID) of the UE that is unique within the MN; receiving, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN; and transmitting, to the UE, configuration information related to the SN including the SCG configuration information.

Some implementations of the present disclosure provide a secondary node (SN) . The SN includes at least one memory; and at least one processor coupled to the at least one memory and configured to cause the SN to: receive a request for SN addition from a master node (MN) , wherein the request for SN addition includes user equipment (UE) capability information and a first identifier (ID) of a UE that is unique within the MN, wherein the UE capability information is related to L1/L2-Triggered Mobility (LTM) ; and transmit an acknowledge message for SN addition request to the MN, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN.

In some implementations of the SN described herein, the UE capability information indicates that the UE supports an inter-centralized unit (CU) LTM.

In some implementations of the SN described herein, the at least one processor is configured to cause the SN to receive, from the MN, one of the following: an inter-CU master cell group (MCG) LTM is configured for the UE; inter-CU SCG LTM configuration information is not allowed to be configured for the UE; or an inter-CU SCG LTM is not allowed.

In some implementations of the SN described herein, the at least one processor is configured to cause the SN to consider one of the following: the inter-CU MCG LTM is configured for the UE; the inter-CU SCG LTM configuration information is not allowed to be configured for the UE; or the inter-CU SCG LTM is not allowed.

In some implementations of the SN described herein, the at least one processor is configured to cause the SN to receive, from the MN, one of the following: configuration information for inter-CU MCG LTM is released; the inter-CU MCG LTM is not configured for the UE; or the inter-CU SCG LTM is allowed.

In some implementations of the SN described herein, the at least one processor is configured to cause the SN to consider one of the following: the configuration information for inter-CU MCG LTM is released; the inter-CU MCG LTM is not configured for the UE; or the inter-CU SCG LTM is allowed.

In some implementations of the SN described herein, the at least one processor is configured to cause the SN to transmit, to the MN, a request message including SCG LTM configuration.

In some implementations of the SN described herein, the at least one processor is configured to cause the SN to receive, from the MN, a first message for refusing the request message.

In some implementations of the SN described herein, the first message includes one of the following: an inter-CU MCG LTM is configured for the UE; or inter-CU SCG LTM configuration information is not allowed to be configured for the UE; or an inter-CU SCG LTM is not allowed.

In some implementations of the SN described herein, the at least one processor is configured to cause the SN to consider one of the following: the inter-CU MCG LTM is configured for the UE; or the inter-CU SCG LTM configuration information is not allowed to be configured for the UE; or the inter-CU SCG LTM is not allowed.

Some implementations of the present disclosure provide a processor for wireless communication, comprising at least one controller coupled with at least one memory and configured to cause the processor to: receive a request for secondary node (SN) addition from a master node (MN) , wherein the request for SN addition includes user equipment (UE) capability information and a first identifier (ID) of a UE that is unique within the MN, wherein the UE capability information is related to L1/L2-Triggered Mobility (LTM) ; and transmit an acknowledge message for SN addition request to the MN, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN.

Some implementations of the present disclosure provide a method performed by a secondary node (SN) . The method includes: receiving a request for SN addition from a master node (MN) , wherein the request for SN addition includes user equipment (UE) capability information and a first identifier (ID) of a UE that is unique within the MN, wherein the UE capability information is related to L1/L2-Triggered Mobility (LTM) ; and transmitting an acknowledge message for SN addition request to the MN, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN.

Some implementations of the present disclosure provide a user equipment (UE) . The UE includes at least one memory; and at least one processor coupled to the at least one memory and configured to cause the UE to: transmit, to a secondary node (SN) , UE capability information indicating that the UE supports an inter-centralized unit (CU) L1/L2-Triggered Mobility (LTM) ; receive configuration information including the following: LTM configuration information for master cell group (MCG) related to one or more LTM candidate cells; and conditional handover (CHO) configuration information for MCG related to one or more CHO candidate cells; and perform a cell selection after a failure.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to: receive first information indicating that the UE is allowed to execute an LTM cell switch if a selected cell is an LTM candidate cell; and receive second information indicating that the UE is allowed to perform CHO if the selected cell is a CHO candidate cell.

In some implementations of the UE described herein, the failure is at least one of the following: a radio link failure (RLF) , a re-configuration with synchronization failure of the MCG, or a mobility from new radio (NR) failure; and the at least one processor is configured to cause the UE to: in response to an occurrence of the failure, initiate a first reestablishment procedure and perform the cell selection; if a first selected cell is configured with CHO configuration, perform CHO; in response to an occurrence of a failure related to the CHO, initiate a second reestablishment procedure and perform a second cell selection; and transmit a reestablishment request to a second selected cell.

In some implementations of the UE described herein, the failure is at least one of the following: a radio link failure (RLF) of the MCG, a re-configuration with synchronization failure of the MCG which is not related to LTM based recovery, or a mobility from new radio (NR) failure; and the at least one processor is configured to cause the UE to perform CHO to a selected cell if the selected cell is a CHO candidate cell.

In some implementations of the UE described herein, the failure is related to LTM based recovery, and the at least one processor is configured to cause the UE to release LTM configuration information in response to: an occurrence of the failure related to LTM based recovery; and the second information is not configured to the UE.

In some implementations of the UE described herein, the failure is related to LTM based recovery, and the at least one processor is configured to cause the UE to: initiate a reestablishment procedure in response to an occurrence of the failure related to LTM based recovery, wherein the cell selection is performed after initiating the reestablishment procedure; and start a timer for cell selection.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to: if a selected cell is a CHO candidate cell, perform a CHO based recovery; and if the selected cell is not the CHO candidate cell, transmit a reestablishment request to the selected cell.

In some implementations of the UE described herein, in response to the occurrence of the failure related to LTM based recovery, the at least one processor is configured to cause the UE to: release LTM configuration information; or keep the LTM configuration information.

In some implementations of the UE described herein, the failure is related to LTM based recovery, and the cell selection is performed in response to an occurrence of the failure related to LTM based recovery.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to receive information indicating whether a CHO based recovery is allowed after an occurrence of the failure related to the LTM based recovery.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to: perform an LTM based recovery; perform a CHO based recovery if the selected cell is configured with CHO configuration after the occurrence of the failure related to the LTM based recovery; and in response to an occurrence of a failure related to the CHO based recovery, transmit a reestablishment request.

In some implementations of the UE described herein, after completing the reestablishment procedure towards a selected cell, the at least one processor is configured to cause the UE to transmit a failure report to the target cell, and wherein the failure report includes information indicating one of the following: the failure related to the CHO based recovery occurs after the failure related to the LTM based recovery; the failure related to the LTM based recovery is followed by the CHO based recovery; the failure related to the LTM based recovery is followed by the failure related to the CHO based recovery; or the CHO based recovery is associated with the LTM based recovery.

In some implementations of the UE described herein, the failure report includes at least one of the following: identifier (ID) information of a candidate cell for the LTM based recovery; or ID information of the candidate cell for the CHO based recovery.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to: perform an LTM based recovery; perform a CHO based recovery after the occurrence of the failure related to the LTM based recovery; after completing the CHO based recovery towards a target CHO cell, transmit a successful handover report to the target CHO cell.

In some implementations of the UE described herein, the successful handover report includes at least one of the following: the CHO based recovery is successfully completed after the failure related to the LTM based recovery; the failure related to the LTM based recovery is followed by successful CHO based recovery; or the successful CHO based recovery is associated with the LTM based recovery.

In some implementations of the UE described herein, the successful handover report includes at least one of the following: identifier (ID) information of a candidate cell for the LTM based recovery; or ID information of the target CHO cell.

In some implementations of the UE described herein, the LTM based recovery is an LTM cell switch following the cell selection performed by the UE while a timer for cell selection is running.

In some implementations of the UE described herein, the CHO based recovery is a CHO procedure following the cell selection performed by the UE while a timer for cell selection is running.

Some implementations of the present disclosure provide a processor for wireless communication, comprising at least one controller coupled with at least one memory and configured to cause the processor to: transmit, to a secondary node (SN) , user equipment (UE) capability information indicating that the UE supports an inter-centralized unit (CU) L1/L2-Triggered Mobility (LTM) ; receive configuration information including the following: LTM configuration information for master cell group (MCG) related to one or more LTM candidate cells; and conditional handover (CHO) configuration information for MCG related to the one or more CHO candidate cells; and perform a cell selection after a failure.

Some implementations of the present disclosure provide a method performed by a user equipment (UE) . The method includes: transmitting, to a secondary node (SN) , UE capability information indicating that the UE supports an inter-centralized unit (CU) L1/L2-Triggered Mobility (LTM) ; receiving configuration information including the following: LTM configuration information for master cell group (MCG) related to one or more LTM candidate cells; and conditional handover (CHO) configuration information for MCG related to the one or more CHO candidate cells; and performing a cell selection after a failure.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates an example of a wireless communications system in accordance with some aspects of the present disclosure.

Figure 2 illustrates an example of a user equipment (UE) 200 in accordance with some aspects of the present disclosure.

Figure 3 illustrates an example of a processor 300 in accordance with some aspects of the present disclosure.

Figure 4 illustrates an example of a network equipment (NE) 400 in accordance with some aspects of the present disclosure.

Figures 5 and 6 illustrate flowcharts of methods related to an LTM cell switch procedure in accordance with some aspects of the present disclosure.

Figures 7 and 8 illustrate schematic diagrams of an LTM cell switch procedure in accordance with some aspects of the present disclosure.

Figure 9 illustrates a flowchart of a method of an LTM cell switch procedure in accordance with some aspects of the present disclosure.

Figures 10 and 11 illustrate schematic diagrams of an LTM cell switch procedure in accordance with some aspects of the present disclosure.

DETAILED DESCRIPTION

In general, when a UE moves from one cell to another cell, at some point a serving cell change needs to be performed. In the legacy, the serving cell change is done by explicit RRC reconfiguration signalling (e.g. a handover (HO) command) to trigger the synchronization of a target cell based on Layer-3 (L3) measurements report. It leads to longer latency, larger overhead, and longer interruption time than beam level mobility. Therefore, in 3GPP, LTM was approved to change a serving cell via L1/L2 signalling, in order to reduce the latency, overhead and interruption time.

LTM is a procedure in which a BS receives L1 measurement report (s) from a UE, and on their basis the BS changes UE’s serving cell by a cell switch command signaled via a MAC CE. The cell switch command indicates an LTM candidate cell configuration that the BS previously prepared and provided to the UE through RRC signalling. Then the UE switches to the target cell according to the cell switch command. The LTM procedure can be used to reduce the mobility latency.

A master cell group (MCG) LTM is a PCell switch procedure that the network triggers via a medium access control (MAC) control element (CE) based on L1 measurements. SCG LTM is a PSCell switch procedure that the network triggers via a medium access control (MAC) control element (CE) based on L1 measurements. The potential applicable scenarios of LTM include "intra-CU intra-DU LTM, " "intra-CU inter-DU LTM, " and "inter-CU LTM" as shown in Figures 5A-5C as described below.

(1) Intra-CU intra-DU mobility: a UE moves between different cells within a DU.

(2) Intra-CU inter-DU mobility: a UE moves between different cells belonging to different DUs but within a CU.

(3) Inter-CU mobility: a UE moves between different cells belonging to different DUs different CUs.

In a MCG LTM procedure or an LTM PCell switch procedure from a source cell (or source PCell) to a target cell (or target PCell) in a dual connectivity (DC) scenario, a node which generates an RRC Reconfiguration message for the MCG LTM switch procedure or the LTM PCell switch procedure, or which determines to initiate MCG LTM may be an MN or a CU of the MN.

In a secondary cell group (SCG) LTM procedure or an LTM PSCell switch procedure from a source PSCell to a target PSCell in a dual connectivity (DC) scenario, a node which generates an RRC Reconfiguration message for the SCG LTM switch procedure or the LTM PSCell switch procedure, or which determines to initiate SCG LTM may be an MN or an SN or a CU of the MN or a CU of the SN, furthermore, the SN may be a node to which the serving PSCell or source PSCell belongs (e.g. a source SN) , or the SN may be a node to which the target PSCell for LTM belongs (e.g. a target SN) .

One objective for mobility enhancements in 3GPP Rel-18 is to specify an LTM procedure (i.e. a PCell or PSCell switch procedure triggered by the network via MAC CE based on L1 measurement) . Currently, following issues regarding an LTM procedure need to be considered, including, e.g. how to avoid a case that both MCG and SCG are configured with inter-CU LTM, whether an LTM based recovery is allowed after a failure related to a CHO based recovery occurs, whether a CHO based recovery is allowed after a failure related to an LTM based recovery occurs, and what is a mobility robustness optimization (MRO) mechanism for a case that a CHO based recovery is allowed after a failure related to an LTM based recovery occurs. However, details regarding enhancements in a case configured with inter-CU LTM have not been discussed yet.

Embodiments of the present disclosure aim to resolve the abovementioned issues. For example, some embodiments design a mechanism for a case that both MCG and SCG are configured with Inter-CU LTM. Some embodiments design a mechanism for a case that an LTM based recovery is not allowed after a failure related to a CHO based recovery occurs. Some embodiments design a mechanism regarding whether a CHO based recovery is allowed after a failure related to an LTM based recovery occurs. Some embodiments design behaviors of a UE in such mechanism. Some other embodiments design a MRO mechanism for a case that a CHO based recovery is allowed after a failure related to an LTM based recovery occurs. Some embodiments design assistant information which may be reported for a failure case and a successful case.

In the embodiments of the present disclosure, an inter-CU LTM may also be named as inter-gNB LTM, inter-BS LTM, or the like. An LTM procedure may also be named as "an LTM cell switch procedure, " "an LTM cell switching procedure, " or the like. An LTM based recovery is an LTM cell switch procedure following the cell selection performed by the UE while a timer for cell selection (e.g. T311) is running. ACHO based recovery is a CHO procedure following the cell selection performed by the UE while a timer for cell selection (e.g. T311) is running.

More details of the embodiments of the present disclosure will be illustrated in the following text in combination with the appended drawings.

Figure 1 illustrates an example of a wireless communications system 100 in accordance with some aspects of the present disclosure. The wireless communications system 100 may include one or more NE 102, one or more UE 104, and a core network (CN) 106. The wireless communications system 100 may support various radio access technologies. In some implementations, the wireless communications system 100 may be a 4G network, such as an LTE network or an LTE-Advanced (LTE-A) network. In some other implementations, the wireless communications system 100 may be a NR network, such as a 5G network, a 5G-Advanced (5G-A) network, or a 5G ultrawideband (5G-UWB) network. In other implementations, the wireless communications system 100 may be a combination of a 4G network and a 5G network, or other suitable radio access technology including Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20. The wireless communications system 100 may support radio access technologies beyond 5G, for example, 6G. Additionally, the wireless communications system 100 may support technologies, such as time division multiple access (TDMA) , frequency division multiple access (FDMA) , or code division multiple access (CDMA) , etc.

The one or more NE 102 may be dispersed throughout a geographic region to form the wireless communications system 100. One or more of the NE 102 described herein may be or include or may be referred to as a network node, a base station, a network element, a network function, a network entity, a radio access network (RAN) , a NodeB, an eNodeB (eNB) , a next-generation NodeB (gNB) , or other suitable terminology. An NE 102 and a UE 104 may communicate via a communication link, which may be a wireless or wired connection. For example, an NE 102 and a UE 104 may perform wireless communication (e.g. receive signaling, transmit signaling) over a Uu interface.

An NE 102 may provide a geographic coverage area for which the NE 102 may support services for one or more UEs 104 within the geographic coverage area. For example, an NE 102 and a UE 104 may support wireless communication of signals related to services (e.g. voice, video, packet data, messaging, broadcast, etc. ) according to one or multiple radio access technologies. In some implementations, an NE 102 may be moveable, for example, a satellite associated with a non-terrestrial network (NTN) . In some implementations, different geographic coverage areas associated with the same or different radio access technologies may overlap, but the different geographic coverage areas may be associated with different NE 102.

The one or more UE 104 may be dispersed throughout a geographic region of the wireless communications system 100. A UE 104 may include or may be referred to as a remote unit, a mobile device, a wireless device, a remote device, a subscriber device, a transmitter device, a receiver device, or some other suitable terminology. In some implementations, the UE 104 may be referred to as a unit, a station, a terminal, or a client, among other examples. Additionally, or alternatively, the UE 104 may be referred to as an Internet-of-Things (IoT) device, an Internet-of-Everything (IoE) device, or machine-type communication (MTC) device, among other examples.

A UE 104 may be able to support wireless communication directly with other UEs 104 over a communication link. For example, a UE 104 may support wireless communication directly with another UE 104 over a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular-V2X deployments, the communication link may be referred to as a sidelink. For example, a UE 104 may support wireless communication directly with another UE 104 over a PC5 interface.

An NE 102 may support communications with the CN 106, or with another NE 102, or both. For example, an NE 102 may interface with other NE 102 or the CN 106 through one or more backhaul links (e.g. S1, N2, or network interface) . In some implementations, the NE 102 may communicate with each other directly. In some other implementations, the NE 102 may communicate with each other or indirectly (e.g. via the CN 106. In some implementations, one or more NE 102 may include subcomponents, such as an access network entity, which may be an example of an access node controller (ANC) . An ANC may communicate with the one or more UEs 104 through one or more other access network transmission entities, which may be referred to as a radio heads, smart radio heads, or transmission-reception points (TRPs) .

The CN 106 may support user authentication, access authorization, tracking, connectivity, and other access, routing, or mobility functions. The CN 106 may be an evolved packet core (EPC) , or a 5G core (5GC) , which may include a control plane entity that manages access and mobility (e.g. a mobility management entity (MME) , an access and mobility management functions (AMF) ) and a user plane entity that routes packets or interconnects to external networks (e.g. a serving gateway (S-GW) , a Packet Data Network (PDN) gateway (P-GW) , or a user plane function (UPF) ) . In some implementations, the control plane entity may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management (e.g. data bearers, signal bearers, etc. ) for the one or more UEs 104 served by the one or more NE 102 associated with the CN 106.

The CN 106 may communicate with a packet data network over one or more backhaul links (e.g. via an S1, N2, or another network interface) . The packet data network may include an application server. In some implementations, one or more UEs 104 may communicate with the application server. A UE 104 may establish a session (e.g. a protocol data unit (PDU) session, or the like) with the CN 106 via an NE 102. The CN 106 may route traffic (e.g. control information, data, and the like) between the UE 104 and the application server using the established session (e.g. the established PDU session) . The PDU session may be an example of a logical connection between the UE 104 and the CN 106 (e.g. one or more network functions of the CN 106) .

In the wireless communications system 100, the NEs 102 and the UEs 104 may use resources of the wireless communications system 100 (e.g. time resources (e.g. symbols, slots, subframes, frames, or the like) or frequency resources (e.g. subcarriers, carriers) ) to perform various operations (e.g. wireless communications) . In some implementations, the NEs 102 and the UEs 104 may support different resource structures. For example, the NEs 102 and the UEs 104 may support different frame structures. In some implementations, such as in 4G, the NEs 102 and the UEs 104 may support a single frame structure. In some other implementations, such as in 5G and among other suitable radio access technologies, the NEs 102 and the UEs 104 may support various frame structures (i.e., multiple frame structures) . The NEs 102 and the UEs 104 may support various frame structures based on one or more numerologies.

One or more numerologies may be supported in the wireless communications system 100, and a numerology may include a subcarrier spacing and a cyclic prefix. A first numerology (e.g. μ=0) may be associated with a first subcarrier spacing (e.g. 15 kHz) and a normal cyclic prefix. In some implementations, the first numerology (e.g. μ=0) associated with the first subcarrier spacing (e.g. 15 kHz) may utilize one slot per subframe. A second numerology (e.g. μ=1) may be associated with a second subcarrier spacing (e.g. 30 kHz) and a normal cyclic prefix. A third numerology (e.g. μ=2) may be associated with a third subcarrier spacing (e.g. 60 kHz) and a normal cyclic prefix or an extended cyclic prefix. A fourth numerology (e.g. μ=3) may be associated with a fourth subcarrier spacing (e.g. 120 kHz) and a normal cyclic prefix. A fifth numerology (e.g. μ=4) may be associated with a fifth subcarrier spacing (e.g. 240 kHz) and a normal cyclic prefix.

A time interval of a resource (e.g. a communication resource) may be organized according to frames (also referred to as radio frames) . Each frame may have a duration, for example, a 10 millisecond (ms) duration. In some implementations, each frame may include multiple subframes. For example, each frame may include 10 subframes, and each subframe may have a duration, for example, a 1 ms duration. In some implementations, each frame may have the same duration. In some implementations, each subframe of a frame may have the same duration.

Additionally or alternatively, a time interval of a resource (e.g. a communication resource) may be organized according to slots. For example, a subframe may include a number (e.g. quantity) of slots. The number of slots in each subframe may also depend on the one or more numerologies supported in the wireless communications system 100. For instance, the first, second, third, fourth, and fifth numerologies (i.e., μ=0, μ=1, μ=2, μ=3, μ=4) associated with respective subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz may utilize a single slot per subframe, two slots per subframe, four slots per subframe, eight slots per subframe, and 16 slots per subframe, respectively. Each slot may include a number (e.g. quantity) of symbols (e.g. OFDM symbols) . In some implementations, the number (e.g. quantity) of slots for a subframe may depend on a numerology. For a normal cyclic prefix, a slot may include 14 symbols. For an extended cyclic prefix (e.g. applicable for 60 kHz subcarrier spacing) , a slot may include 12 symbols. The relationship between the number of symbols per slot, the number of slots per subframe, and the number of slots per frame for a normal cyclic prefix and an extended cyclic prefix may depend on a numerology. It should be understood that reference to a first numerology (e.g. μ=0) associated with a first subcarrier spacing (e.g. 15 kHz) may be used interchangeably between subframes and slots.

In the wireless communications system 100, an electromagnetic (EM) spectrum may be split, based on frequency or wavelength, into various classes, frequency bands, frequency channels, etc. By way of example, the wireless communications system 100 may support one or multiple operating frequency bands, such as frequency range designations FR1 (410 MHz –7.125 GHz) , FR2 (24.25 GHz –52.6 GHz) , FR3 (7.125 GHz –24.25 GHz) , FR4 (52.6 GHz –114.25 GHz) , FR4a or FR4-1 (52.6 GHz –71 GHz) , and FR5 (114.25 GHz –300 GHz) . In some implementations, the NEs 102 and the UEs 104 may perform wireless communications over one or more of the operating frequency bands. In some implementations, FR1 may be used by the NEs 102 and the UEs 104, among other equipment or devices for cellular communications traffic (e.g. control information, data) . In some implementations, FR2 may be used by the NEs 102 and the UEs 104, among other equipment or devices for short-range, high data rate capabilities.

FR1 may be associated with one or multiple numerologies (e.g. at least three numerologies) . For example, FR1 may be associated with a first numerology (e.g. μ=0) , which includes 15 kHz subcarrier spacing; a second numerology (e.g. μ=1) , which includes 30 kHz subcarrier spacing; and a third numerology (e.g. μ=2) , which includes 60 kHz subcarrier spacing. FR2 may be associated with one or multiple numerologies (e.g. at least 2 numerologies) . For example, FR2 may be associated with a third numerology (e.g. μ=2) , which includes 60 kHz subcarrier spacing; and a fourth numerology (e.g. μ=3) , which includes 120 kHz subcarrier spacing.

Figure 2 illustrates an example of a UE 200 in accordance with some aspects of the present disclosure. The UE 200 may include a processor 202, a memory 204, a controller 206, and a transceiver 208. The processor 202, the memory 204, the controller 206, or the transceiver 208, or various combinations thereof or various components thereof may be examples of means for performing various aspects of the present disclosure as described herein. These components may be coupled (e.g. operatively, communicatively, functionally, electronically, electrically) via one or more interfaces.

The processor 202, the memory 204, the controller 206, or the transceiver 208, or various combinations or components thereof may be implemented in hardware (e.g. circuitry) . The hardware may include a processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , or other programmable logic device, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure.

The processor 202 may include an intelligent hardware device (e.g. a general-purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination thereof) . In some implementations, the processor 202 may be configured to operate the memory 204. In some other implementations, the memory 204 may be integrated into the processor 202. The processor 202 may be configured to execute computer-readable instructions stored in the memory 204 to cause the UE 200 to perform various functions of the present disclosure.

The memory 204 may include volatile or non-volatile memory. The memory 204 may store computer-readable, computer-executable code including instructions when executed by the processor 202 cause the UE 200 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such the memory 204 or another type of memory. Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer.

In some implementations, the processor 202 and the memory 204 coupled with the processor 202 may be configured to cause the UE 200 to perform one or more of the functions described herein (e.g. executing, by the processor 202, instructions stored in the memory 204) . For example, the processor 202 may support wireless communication at the UE 200 in accordance with examples as disclosed with respect to Figure 9. The UE 200 may be configured to support: a means for transmitting, to an SN, UE capability information indicating that the UE supports an inter-CU LTM; a means for receiving configuration information including the following: LTM configuration information for MCG related to one or more LTM candidate cells; and CHO configuration information for MCG related to one or more CHO candidate cells; and a means for performing a cell selection after a failure.

The controller 206 may manage input and output signals for the UE 200. The controller 206 may also manage peripherals not integrated into the UE 200. In some implementations, the controller 206 may utilize an operating system such as or other operating systems. In some implementations, the controller 206 may be implemented as part of the processor 202.

In some implementations, the UE 200 may include at least one transceiver 208. In some other implementations, the UE 200 may have more than one transceiver 208. The transceiver 208 may represent a wireless transceiver. The transceiver 208 may include one or more receiver chains 210, one or more transmitter chains 212, or a combination thereof. The means for receiving abovementioned in the processor 202 or the means for transmitting in the processor 202 may be implemented via at least one transceiver 208.

A receiver chain 210 may be configured to receive signals (e.g. control information, data, packets) over a wireless medium. For example, the receiver chain 210 may include one or more antennas for receive the signal over the air or wireless medium. The receiver chain 210 may include at least one amplifier (e.g. a low-noise amplifier (LNA) ) configured to amplify the received signal. The receiver chain 210 may include at least one demodulator configured to demodulate the receive signal and obtain the transmitted data by reversing the modulation technique applied during transmission of the signal. The receiver chain 210 may include at least one decoder for decoding the processing the demodulated signal to receive the transmitted data.

A transmitter chain 212 may be configured to generate and transmit signals (e.g. control information, data, packets) . The transmitter chain 212 may include at least one modulator for modulating data onto a carrier signal, preparing the signal for transmission over a wireless medium. The at least one modulator may be configured to support one or more techniques such as amplitude modulation (AM) , frequency modulation (FM) , or digital modulation schemes like phase-shift keying (PSK) or quadrature amplitude modulation (QAM) . The transmitter chain 212 may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over the wireless medium. The transmitter chain 212 may also include one or more antennas for transmitting the amplified signal into the air or wireless medium.

Figure 3 illustrates an example of a processor 300 in accordance with some aspects of the present disclosure. The processor 300 may be an example of a processor configured to perform various operations in accordance with examples as described herein. The processor 300 may include a controller 302 configured to perform various operations in accordance with examples as described herein. The processor 300 may optionally include at least one memory 304, which may be, for example, an L1/L2/L3 cache. Additionally, or alternatively, the processor 300 may optionally include one or more arithmetic-logic units (ALUs) 306. One or more of these components may be in electronic communication or otherwise coupled (e.g. operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g. buses) .

The processor 300 may be a processor chipset and include a protocol stack (e.g. a software stack) executed by the processor chipset to perform various operations (e.g. receiving, obtaining, retrieving, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, reading) in accordance with examples as described herein. The processor chipset may include one or more cores, one or more caches (e.g. memory local to or included in the processor chipset (e.g. the processor 300) or other memory (e.g. random access memory (RAM) , read-only memory (ROM) , dynamic RAM (DRAM) , synchronous dynamic RAM (SDRAM) , static RAM (SRAM) , ferroelectric RAM (FeRAM) , magnetic RAM (MRAM) , resistive RAM (RRAM) , flash memory, phase change memory (PCM) , and others) .

The controller 302 may be configured to manage and coordinate various operations (e.g. signaling, receiving, obtaining, retrieving, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, reading) of the processor 300 to cause the processor 300 to support various operations in accordance with examples as described herein. For example, the controller 302 may operate as a control unit of the processor 300, generating control signals that manage the operation of various components of the processor 300. These control signals include enabling or disabling functional units, selecting data paths, initiating memory access, and coordinating timing of operations.

The controller 302 may be configured to fetch (e.g. obtain, retrieve, receive) instructions from the memory 304 and determine subsequent instruction (s) to be executed to cause the processor 300 to support various operations in accordance with examples as described herein. The controller 302 may be configured to track memory address of instructions associated with the memory 304. The controller 302 may be configured to decode instructions to determine the operation to be performed and the operands involved. For example, the controller 302 may be configured to interpret the instruction and determine control signals to be output to other components of the processor 300 to cause the processor 300 to support various operations in accordance with examples as described herein. Additionally, or alternatively, the controller 302 may be configured to manage flow of data within the processor 300. The controller 302 may be configured to control transfer of data between registers, arithmetic logic units (ALUs) , and other functional units of the processor 300.

The memory 304 may include one or more caches (e.g. memory local to or included in the processor 300 or other memory, such RAM, ROM, DRAM, SDRAM, SRAM, MRAM, flash memory, etc. In some implementations, the memory 304 may reside within or on a processor chipset (e.g. local to the processor 300) . In some other implementations, the memory 304 may reside external to the processor chipset (e.g. remote to the processor 300) .

The memory 304 may store computer-readable, computer-executable code including instructions that, when executed by the processor 300, cause the processor 300 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. The controller 302 and/or the processor 300 may be configured to execute computer-readable instructions stored in the memory 304 to cause the processor 300 to perform various functions. For example, the processor 300 and/or the controller 302 may be coupled with or to the memory 304, the processor 300, the controller 302, and the memory 304 may be configured to perform various functions described herein. In some examples, the processor 300 may include multiple processors and the memory 304 may include multiple memories. One or more of the multiple processors may be coupled with one or more of the multiple memories, which may, individually or collectively, be configured to perform various functions herein.

The one or more ALUs 306 may be configured to support various operations in accordance with examples as described herein. In some implementations, the one or more ALUs 306 may reside within or on a processor chipset (e.g. the processor 300) . In some other implementations, the one or more ALUs 306 may reside external to the processor chipset (e.g. the processor 300) . One or more ALUs 306 may perform one or more computations such as addition, subtraction, multiplication, and division on data. For example, one or more ALUs 306 may receive input operands and an operation code, which determines an operation to be executed. One or more ALUs 306 be configured with a variety of logical and arithmetic circuits, including adders, subtractors, shifters, and logic gates, to process and manipulate the data according to the operation. Additionally, or alternatively, the one or more ALUs 306 may support logical operations such as AND, OR, exclusive-OR (XOR) , not-OR (NOR) , and not-AND (NAND) , enabling the one or more ALUs 306 to handle conditional operations, comparisons, and bitwise operations.

The processor 300 may support wireless communication in accordance with examples as disclosed herein.

In some implementations, the processor 300 may be configured to support means for performing operations of an MN as described with respect to Figure 5. For example, the processor 300 may be configured to or operable to support: a means for receiving, from a UE, UE capability information related to LTM; a means for transmitting a request for SN addition to an SN, wherein the request for SN addition includes the UE capability information and a first identifier (ID) of the UE that is unique within the MN; a means for receiving, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes SCG configuration information and a second ID of the UE that is unique within the SN; and a means for transmitting, to the UE, configuration information related to the SN including the SCG configuration information.

In some implementations, the processor 300 may be configured to support means for performing operations of an SN as described with respect to Figure 6. The processor 300 may be configured to or operable to support: a means for receiving a request for SN addition from an MN, wherein the request for SN addition includes UE capability information and a first ID of a UE that is unique within the MN, wherein the UE capability information is related to LTM; and a means for transmitting an acknowledge message for SN addition request to the MN, wherein the acknowledge message includes SCG configuration information and a second ID of the UE that is unique within the SN.

In some implementations, the processor 300 may be configured to support means for performing operations of a UE as described with respect to Figure 9. The processor 300 may be configured to or operable to support: a means for transmitting, to an SN, UE capability information indicating that the UE supports an inter-CU LTM; a means for receiving configuration information including the following: LTM configuration information for MCG related to one or more LTM candidate cells; and CHO configuration information for MCG related to one or more CHO candidate cells; and a means for performing a cell selection after a failure.

It should be appreciated by persons skilled in the art that the components in exemplary processor 300 may be changed, for example, some of the components in exemplary processor 300 may be omitted or modified or new component (s) may be added to exemplary processor 300, without departing from the spirit and scope of the disclosure. For example, in some embodiments, the processor 300 may not include the ALUs 306.

Figure 4 illustrates an example of a NE 400 in accordance with some aspects of the present disclosure. The NE 400 may include a processor 402, a memory 404, a controller 406, and a transceiver 408. The processor 402, the memory 404, the controller 406, or the transceiver 408, or various combinations thereof or various components thereof may be examples of means for performing various aspects of the present disclosure as described herein. These components may be coupled (e.g. operatively, communicatively, functionally, electronically, electrically) via one or more interfaces.

The processor 402, the memory 404, the controller 406, or the transceiver 408, or various combinations or components thereof may be implemented in hardware (e.g. circuitry) . The hardware may include a processor, a digital signal processor (DSP) , an application-specific integrated circuit (ASIC) , or other programmable logic device, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure.

The processor 402 may include an intelligent hardware device (e.g. a general-purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination thereof) . In some implementations, the processor 402 may be configured to operate the memory 404. In some other implementations, the memory 404 may be integrated into the processor 402. The processor 402 may be configured to execute computer-readable instructions stored in the memory 404 to cause the NE 400 to perform various functions of the present disclosure.

The memory 404 may include volatile or non-volatile memory. The memory 404 may store computer-readable, computer-executable code including instructions when executed by the processor 402 cause the NE 400 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such the memory 404 or another type of memory. Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer.

In some implementations, the processor 402 and the memory 404 coupled with the processor 402 may be configured to cause the NE 400 to perform one or more of the functions described herein (e.g. executing, by the processor 402, instructions stored in the memory 404) . For example, the processor 402 may support wireless communication at the NE 400 in accordance with examples as disclosed herein. For example, the NE 400 may be configured to support means for performing the operations as described with respect to Figures 5 and 6 as described below.

In some implementations, the NE 400 may be an MN as described with respect to Figure 5. The NE 400 may be configured to support: a means for receiving, from a UE, UE capability information related to LTM; a means for transmitting a request for SN addition to an SN, wherein the request for SN addition includes the UE capability information and a first ID of the UE that is unique within the MN; a means for receiving, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes SCG configuration information and a second ID of the UE that is unique within the SN; and a means for transmitting, to the UE, configuration information related to the SN including the SCG configuration information.

In some implementations, the NE 400 may be an SN as described with respect to Figure 6. The NE 400 may be configured to support: a means for receiving a request for SN addition from an MN, wherein the request for SN addition includes UE capability information and a first ID of a UE that is unique within the MN, wherein the UE capability information is related to LTM; and a means for transmitting an acknowledge message for SN addition request to the MN, wherein the acknowledge message includes SCG configuration information and a second ID of the UE that is unique within the SN.

The controller 406 may manage input and output signals for the NE 400. The controller 406 may also manage peripherals not integrated into the NE 400. In some implementations, the controller 406 may utilize an operating system such as or other operating systems. In some implementations, the controller 406 may be implemented as part of the processor 402.

In some implementations, the NE 400 may include at least one transceiver 408. In some other implementations, the NE 400 may have more than one transceiver 408. The transceiver 408 may represent a wireless transceiver. The transceiver 408 may include one or more receiver chains 410, one or more transmitter chains 412, or a combination thereof. The means for receiving or the means for transmitting abovementioned in the processor 402 may be implemented via at least one transceiver 408.

A receiver chain 410 may be configured to receive signals (e.g. control information, data, packets) over a wireless medium. For example, the receiver chain 410 may include one or more antennas for receive the signal over the air or wireless medium. The receiver chain 410 may include at least one amplifier (e.g. a low-noise amplifier (LNA) ) configured to amplify the received signal. The receiver chain 410 may include at least one demodulator configured to demodulate the receive signal and obtain the transmitted data by reversing the modulation technique applied during transmission of the signal. The receiver chain 410 may include at least one decoder for decoding the processing the demodulated signal to receive the transmitted data.

A transmitter chain 412 may be configured to generate and transmit signals (e.g. control information, data, packets) . The transmitter chain 412 may include at least one modulator for modulating data onto a carrier signal, preparing the signal for transmission over a wireless medium. The at least one modulator may be configured to support one or more techniques such as amplitude modulation (AM) , frequency modulation (FM) , or digital modulation schemes like phase-shift keying (PSK) or quadrature amplitude modulation (QAM) . The transmitter chain 412 may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over the wireless medium. The transmitter chain 412 may also include one or more antennas for transmitting the amplified signal into the air or wireless medium.

It should be appreciated by persons skilled in the art that the components in exemplary NE 400 may be changed, for example, some of the components in exemplary NE 400 may be omitted or modified or new component (s) may be added to exemplary NE 400, without departing from the spirit and scope of the disclosure. For example, in some embodiments, the NE 400 may not include the controller 406.

Figure 5 illustrates a flowchart of a method related to an LTM cell switch procedure in accordance with some aspects of the present disclosure. The operations of the method may be implemented by a network node as described herein. In some implementations, the network node may be an MN, and may execute a set of instructions to control the function elements of the MN to perform the described functions. In some implementations, aspects of operations 502, 504, 506 and 508 may be performed by NE 400 as described with reference to Figure 4. Each of operations 502 to 508 may be performed in accordance with examples as described herein. Specific examples are described in the embodiments of Figures 7 and 8 as follows.

At operation 502, the method may include receiving UE capability information related to LTM by an MN from a UE. In some embodiments, the UE capability information may indicate that the UE supports an inter-CU LTM. In some other embodiments, the UE capability information may indicate that the UE supports both a dual connectivity (DC) and an inter-CU LTM. Inter-CU LTM may also be named as inter-gNB LTM, inter-BS LTM or the like.

At operation 504, the method may include transmitting a request for SN addition by the MN to an SN. The request for SN addition may include the UE capability information and an ID of the UE that is unique within the MN. For instance, the request is an SN ADDITION REQUEST message. The ID of the UE could be an M-NG-RAN node UE XnAP ID which shall be allocated so as to uniquely identify the UE over the Xn interface within an M-NG-RAN node for dual connectivity.

At operation 506, the method may include receiving an acknowledge message for SN addition request by the MN from the SN. The acknowledge message may include SCG configuration information and another ID of the UE that is unique within the SN. For instance, the acknowledge message is an SN ADDITION REQUEST ACKNOWLEDGE message. The another ID of the UE could be an S-NG-RAN node UE XnAP ID which shall be allocated so as to uniquely identify the UE over the Xn interface within an S-NG-RAN node for dual connectivity.

At operation 508, the method may include transmitting, by the MN to the UE, configuration information related to the SN (e.g. RRC configuration) which includes the SCG configuration information.

In some implementations of the method, the MN may transmit one of the following information (e.g. in an indication, denoted as indication #1 for simplicity) to the SN, for example, via Xn interface:

(1) an inter-CU MCG LTM is configured or has been configured for the UE;

(2) inter-CU SCG LTM configuration information is not allowed to be configured for the UE;

(3) an inter-CU SCG LTM is not allowed, e.g. for the UE.

In some implementations of the method, indication #1 may be transmitted in an ACTIVITY NOTIFICATION message or a new Xn message.

In some implementations of the method, if the MN configures the UE to release all configuration information for inter-CU MCG LTM, the MN may transmit one of the following information (e.g. in an indication, denoted as indication #2) to the SN, for example, via Xn interface:

(1) the configuration information for inter-CU MCG LTM is released or has been released;

(2) the inter-CU MCG LTM is not configured for the UE; or

(3) the inter-CU SCG LTM is allowed, e.g. for the UE.

In some implementations of the method, the MN may receive, from the SN (e.g. a source SN) , a request message including SCG LTM configuration. The request message may include inter-CU SCG LTM configuration information. The request message may be named as "a request for preparing inter-CU SCG LTM" or the like. The request message may be based on a measurement report received from the UE. For instance, the request message may be an SN change required message, an SN modification required message, or an S-NODE MODIFICATION REQUIRED message. In some embodiments, the request for preparing inter-CU SCG LTM is received by the MN from the SN after the SN initiates an inter-CU MCG LTM. For example, the request message may include information (e.g. in an indication, denoted as indication #3) indicating that the SN aims to initiate the inter-CU SCG LTM. For instance, indication #3 may be carried in a cause IE of the request message.

In an implementation of the method, after receiving the request message, the MN may transmit a message (denoted as message #1) for refusing or rejecting the request message to the SN. For instance, message #1 may include one of the following information:

(1) an inter-CU MCG LTM is configured or has been configured for the UE;

(3) an inter-CU SCG LTM is not allowed, e.g. for the UE.

For example, such information may be carried in a cause information element (IE) included in message #1, and the cause IE may be denoted as indication #4. For example, message #1 may be an SN modification refuse message or an S-NODE MODIFICATION REFUSE message.

Figure 6 illustrates a flowchart of a method related to an LTM cell switch procedure in accordance with some aspects of the present disclosure. The operations of the method may be implemented by a network node as described herein. In some implementations, the network node may be an SN, and may execute a set of instructions to control the function elements of the SN to perform the described functions. In some implementations, aspects of operations 602 and 604 may be performed by NE 400 as described with reference to Figure 4. Each of operations 602 and 604 may be performed in accordance with examples as described herein. Specific examples are described in the embodiments of Figures 7 and 8 as follows.

At operation 602, the method may include receiving a request for SN addition by an SN from an MN. The request for SN addition may include UE capability information and an ID of a UE that is unique within the MN. The ID of the UE could be an M-NG-RAN node UE XnAP ID which shall be allocated so as to uniquely identify the UE over the Xn interface within an M-NG-RAN node for dual connectivity.

The UE capability information may be related to LTM. In some embodiments, the UE capability information may indicate that the UE supports an inter-CU LTM. In some other embodiments, the UE capability information may indicate that the UE supports both a dual connectivity (DC) and an inter-CU LTM (i.e. inter-gNB LTM or inter-BS LTM) .

At operation 604, the method may include transmitting an acknowledge message for SN addition request by the SN to the MN. The acknowledge message may include SCG configuration information and an ID of the UE that is unique within the SN. The ID of the UE could be an S-NG-RAN node UE XnAP ID which shall be allocated so as to uniquely identify the UE over the Xn interface within an S-NG-RAN node for dual connectivity.

In some implementations of the method, the SN may receive one of the following information (e.g. indication #1 as described in the embodiments of Figure 5) from the MN, e.g. via Xn interface:

(1) an inter-CU MCG LTM is configured or has been configured for the UE;

(2) inter-CU SCG LTM configuration information is not allowed to be configured for the UE;or

(3) an inter-CU SCG LTM is not allowed, e.g. for the UE.

In an implementation of the method, after receiving the above information, the SN may consider one of the following:

(1) the inter-CU MCG LTM is configured or has been configured for the UE;

(2) the inter-CU SCG LTM configuration information is not allowed to be configured for the UE;or

(3) the inter-CU SCG LTM is not allowed, e.g. for the UE.

In some implementations of the method, the SN may receive one of the following information (e.g. indication #2 as described in the embodiments of Figure 5) from the MN:

(1) configuration information for inter-CU MCG LTM is released or has been released, e.g. by the MN;

(2) the inter-CU MCG LTM is not configured for the UE; or

(3) the inter-CU SCG LTM is allowed, e.g. for the UE.

(1) the configuration information for inter-CU MCG LTM released or has been released, e.g. by the MN;

(2) the inter-CU MCG LTM is not configured for the UE; or

(3) the inter-CU SCG LTM is allowed, e.g. for the UE.

In some implementations of the method, the SN may transmit, to the MN, a request message including SCG LTM configuration. The request message may include inter-CU SCG LTM configuration information. The request message may be named as "a request for preparing inter-CU SCG LTM" or the like. The request message may be based on a measurement report received by the SN from the UE. For instance, the request message may be an SN change required message, an SN modification required message, or an S-NODE MODIFICATION REQUIRED message. In some embodiments, the request for preparing inter-CU SCG LTM is received by the MN from the SN after the SN initiates an inter-CU MCG LTM. For example, the request message may include information (e.g. indication #3 as described in the embodiments of Figure 5) indicating that the SN aims to initiate the inter-CU SCG LTM, which may be carried in a cause IE of the request message.

In an implementation of the method, the SN may receive a message (e.g. message #1 as described in the embodiments of Figure 5) for refusing or rejecting the request message from the MN. For instance, the message includes one of the following information, e.g. in a cause IE (e.g. indication #4 as described in the embodiments of Figure 5) :

(1) an inter-CU MCG LTM is configured or has been configured for the UE;

(2) inter-CU SCG LTM configuration information is not allowed to be configured for the UE; or

(3) an inter-CU SCG LTM is not allowed, e.g. for the UE.

For example, this message may be an SN modification refuse message or an S-NODE MODIFICATION REFUSE message. After receiving the message, the SN may consider one of the following:

(1) the inter-CU MCG LTM is configured or has been configured for the UE;

(3) the inter-CU SCG LTM is not allowed, e.g. for the UE.

It should be noted that the method described in Figure 5 or Figure 6 describes possible implementations, and that the operations and the steps may be rearranged or otherwise eliminated or modified and that other implementations are possible, without departing from the spirit and scope of the disclosure.

Figure 7 illustrates a schematic diagram of an LTM cell switch procedure in accordance with some aspects of the present disclosure. The embodiments of Figure 7 assume that an MN is aware of Inter-CU SCG LTM, and an SN is allowed to initiate configuration of Inter-CU SCG LTM. The embodiments of Figure 7 solves an issue of how to avoid the case that both MCG and SCG are configured with Inter-CU LTM. Details described in all other embodiments of the present disclosure are applicable for the embodiments of Figure 7.

As shown in Figure 7, in operation 711, UE 701 may access the network via Dual-connectivity (DC) including MCG and SCG. Namely, UE 701 accesses MN 702 and SN 703 via a DC scenario.

In some implementations of operation 711, UE 701 may report UE capability information to the network if receiving the enquiry from the network, e.g. MN 702. For example, the UE capability information includes at least one of the following:

(1) information to indicate whether UE 701 supports Inter-CU LTM;

(2) information to indicate whether UE 701 supports Inter-CU MCG LTM; or

(3) information to indicate whether UE 701 supports Inter-CU SCG LTM.

In some implementations of operation 711, MN 702 may transmit to SN 703 a request for SN addition, i.e., the SN addition request (e.g. an SN ADDITION REQUEST message) . The request may include the UE capability information and a UE ID of UE 701 that is unique within MN 702. The UE ID of UE 701 could be an M-NG-RAN node UE XnAP ID, which shall be allocated so as to uniquely identify the UE over the Xn interface within an M-NG-RAN node for dual connectivity. After SN 703 receives an M-NG-RAN node UE XnAP ID, SN 703 may store it for the duration of the UE-associated logical Xn-connection for UE 701. If SN 703 is able to admit the resource request, SN 703 may allocate respective radio resources. For example, SN 703 may assign SCG radio resources for UE 701 and generate the corresponding SN radio resource configuration information (e.g. SCG configuration information) . Then, SN 703 may decide for the PSCell and other SCG SCells and provide the SCG radio resource configuration information to MN 702 within an SN RRC configuration message contained in an acknowledge message for the SN addition request, e.g. an SN ADDITION REQUEST ACKNOWLEDGE message. The acknowledge message (e.g. the SN ADDITION REQUEST ACKNOWLEDGE message) may include an UE ID of UE 701 that is unique within SN. This UE ID of UE 701 could be an S-NG-RAN node UE XnAP ID, which shall be allocated so as to uniquely identify the UE over the Xn interface within an S-NG-RAN node for dual connectivity. After MN 702 receives an S-NG-RAN node UE XnAP ID, MN 702 may store it for the duration of the UE-associated logical Xn-connection for UE 701. Then, MN 702 may transmit configuration information related to SN 703 (e.g. RRC configuration information which includes the SCG configuration information) to UE 701.

In some implementations of operation 711, UE 701 may receive configuration information related to L1 or L3 measurement report. UE 701 may send a measurement report to MN 702 and/or SN 703 based on the configuration information.

In operation 712, MN 702 (i.e. the source MN) may initiate an inter-CU MCG LTM based on the measurement report. After MN 702 initiates the inter-CU MCG LTM, MN 702 may transmit a request, e.g. a handover request, to a candidate MN or a candidate gNB (e.g. another gNB not show in Figure 7) . After MN 702 receives the inter-CU LTM configuration information for a candidate cell, MN 702 may transmit an RRC reconfiguration message including Inter-CU LTM configuration information to UE 701. For example, the RRC configuration message may include LTM configuration information, e.g. LTM-Config IE. The LTM configuration information may further include the configuration, e.g. a random access channel (RACH) resource for early timing advance (TA) acquisition, to UE 701.

In some implementations of operation 712, to support early downlink (DL) synchronization (e.g. Early DL sync) using channel state information reference signal (CSI-RS) , when MN 702 (i.e. the source MN) transmits a request to a candidate MN or a candidate gNB (e.g. another gNB not show in Figure 7) to prepare Inter-CU MCG LTM or Inter-CU SCG LTM, an indication may be added in the request. The indication may indicate one of the following:

(1) Early DL synchronization is expected for UE 701.

(2) CSI-RS is needed for early DL synchronization.

(3) Dedicated Reference signalling is needed for early DL synchronization.

After receiving the request from MN 702 (i.e. the source MN) , the candidate gNB may transmit a response message. The response message may include dedicated reference signaling, e.g. CSI-RS for early DL synchronization.

In operation 713, MN 702 may transmit a message including an indication (e.g. indication #1 as described above) to SN 703 via Xn interface. The indication may indicate that Inter-CU MCG LTM or Inter-gNB MCG LTM has been configured for UE 701, or indicate that Inter-CU SCG LTM configuration or Inter-gNB SCG LTM configuration is not allowed, or indicate that Inter-CU SCG LTM or Inter-gNB SCG LTM is not allowed. The message could be an ACTIVITY NOTIFICATION or a new Xn message.

In operation 714, after SN 703 receives the message including the indication (e.g. indication #1) , SN 703 may consider that Inter-CU MCG LTM or Inter-gNB MCG LTM has been configured for UE 701, or consider that Inter-CU SCG LTM configuration or Inter-gNB SCG LTM configuration is not allowed, or consider that Inter-CU SCG LTM or Inter-gNB SCG LTM is not allowed.

In operation 715, MN 702 configures UE 701 to release all the configuration information for Inter-CU MCG LTM.

In operation 716, after MN 702 configures UE 701 to release all the configuration information for Inter-CU MCG LTM, MN 702 may transmit a message including an indication (e.g. indication #2 as described above) to SN 703. The indication could be one of the following:

(1) Inter-CU MCG LTM is released or has been released.

(2) Inter-CU MCG LTM is not configured to UE 701.

(3) Inter-CU SCG LTM is allowed.

In operation 717, after SN 703 receives the message including the indication (e.g. indication #2) , SN 703 may consider one of the following:

(1) Inter-CU MCG LTM is released or has been released.

(2) Inter-CU MCG LTM is not configured to UE 701.

(3) Inter-CU SCG LTM is allowed.

Figure 8 illustrates a schematic diagram of an LTM cell switch procedure in accordance with some aspects of the present disclosure. The embodiments of Figure 8 assume that Inter-CU MCG LTM has been configured to a UE by an MN, and an SN is allowed to initiate configuration of Inter-CU SCG LTM. The embodiments of Figure 8 solves an issue of how to avoid the case that both MCG and SCG are configured with Inter-CU LTM. Details described in all other embodiments of the present disclosure are applicable for the embodiments of Figure 8.

As shown in Figure 8, in operation 811, UE 801 may access the network via Dual-connectivity (DC) including MCG and SCG. Namely, UE 801 accesses MN 802 and SN 803 via a DC scenario.

In some implementations of operation 811, UE 801 may report UE capability information to the network if receiving the enquiry from the network, e.g. MN 802. For example, the UE capability information includes at least one of the following:

(1) information to indicate whether UE 801 supports Inter-CU LTM;

(2) information to indicate whether UE 801 supports Inter-CU MCG LTM; or

(3) information to indicate whether UE 801 supports Inter-CU SCG LTM.

In some implementations of operation 811, MN 802 may transmit to SN 803 a request for SN addition, i.e., the SN addition request (e.g. an SN ADDITION REQUEST message) . The request may include the UE capability information and a UE ID of UE 801 that is unique within MN 802. The UE ID of UE 801 could be an M-NG-RAN node UE XnAP ID, which shall be allocated so as to uniquely identify the UE over the Xn interface within an M-NG-RAN node for dual connectivity. After SN 803 receives an M-NG-RAN node UE XnAP ID, SN 803 may store it for the duration of the UE-associated logical Xn-connection for UE 801. If SN 803 is able to admit the resource request, SN 803 may allocate respective radio resources. For example, SN 803 may assign SCG radio resources for UE 801 and generate the corresponding SN radio resource configuration information (e.g. SCG configuration information) . Then, SN 803 may decide for the PSCell and other SCG SCells and provide the SCG radio resource configuration information to MN 802 within an SN RRC configuration message contained in an acknowledge message for the SN addition request, e.g. an SN ADDITION REQUEST ACKNOWLEDGE message. The acknowledge message (e.g. the SN ADDITION REQUEST ACKNOWLEDGE message) may include an UE ID of UE 801 that is unique within SN. This UE ID of UE 801 could be an S-NG-RAN node UE XnAP ID, which shall be allocated so as to uniquely identify the UE over the Xn interface within an S-NG-RAN node for dual connectivity. After MN 802 receives an S-NG-RAN node UE XnAP ID, MN 802 may store it for the duration of the UE-associated logical Xn-connection for UE 801. Then, MN 802 may transmit configuration information related to SN 803 (e.g. RRC configuration information which includes the SCG configuration information) to UE 801.

In some implementations of operation 811, UE 801 may receive configuration information related to L1 or L3 measurement report. UE 801 may send a measurement report to MN 802 and/or SN 803 based on the configuration information.

In operation 812, SN 803 (i.e. the source SN) may transmit, to MN 802, a request message for preparing Inter-CU SCG LTM based on the measurement report received from UE 801. For example, the request message could be an SN MODIFICATION REQUIRED message. In some embodiments, after SN 803 initiates Inter-CU MCG LTM, SN 803 may transmit the request message, e.g. an S-NODE MODIFICATION REQUIRED message, to MN 802 in operation 812. In some example, the request message may include Inter-CU SCG LTM configuration information. In some example, the request message may include information (e.g. indication #3 as described above) indicating that SN 803 aims to initiate the inter-CU SCG LTM, e.g. in a cause IE of the request message.

In operation 813, after MN 802 receives the request message from SN 803, MN 802 may transmit a message (e.g. message #1 as described above) for refusing or rejecting the request message to SN 803 via Xn interface. For example, MN 802 may refuse or reject the request message for the cause that Inter-CU MCG LTM has been configured to UE 801. The message may include information (e.g. indication #4 as described above) , e.g. in a cause IE, to indicate to SN 803 that Inter-CU MCG LTM has been configured for UE 801 or Inter-CU SCG LTM configuration is not allowed. For instance, the message could be an SN modification refuse message or an S-NODE MODIFICATION REFUSE message.

In operation 814, after SN 803 receives the message (e.g. message #1) including the indication (e.g. indication #4) , SN 803 may consider that Inter-CU MCG LTM has been configured to UE 801, Inter-CU SCG LTM is not allowed, or Inter-CU SCG LTM is refused.

Figure 9 illustrates a flowchart of a method related to an LTM cell switch procedure in accordance with some aspects of the present disclosure. The operations of the method may be implemented by a UE as described herein. In some implementations, the UE may execute a set of instructions to control the function elements of the UE to perform the described functions. In some implementations, aspects of operations 902, 904, and 906 may be performed by UE 200 as described with reference to Figure 2. Each of operations 902-906 may be performed in accordance with examples as described herein. Specific examples are described in the embodiments of Figures 10 and 11 as follows.

At operation 902, the method may include transmitting, by a UE to an SN, UE capability information indicating that the UE supports an inter-CU LTM. In some embodiments, the UE capability information may indicate that the UE supports both a dual connectivity (DC) and an inter-CU LTM (i.e. inter-gNB LTM or inter-BS LTM) .

At operation 904, the method may include receiving configuration information by the UE. The configuration information may be carried in one or more RRC reconfiguration messages. For example, the configuration information includes: LTM configuration information for MCG related to one or more LTM candidate cells; and CHO configuration information for MCG related to one or more CHO candidate cells.

At operation 906, the method may include performing a cell selection by the UE after a failure. The failure may be a radio link failure (RLF) , a re-configuration with synchronization failure of the MCG (e.g. a handover failure) , and/or a mobility from new radio (NR) failure (e.g. when switching from a 5G network to a 4G network or a 3G network) .

In some implementations, the UE may receive information (e.g. an RRC reconfiguration message) indicating whether a CHO based recovery is allowed after an occurrence of the failure related to the LTM based recovery (e.g. an LTM recovery failure) . Specific examples are described in the embodiments of Figure 10 as follows.

In some embodiments of the method, the UE may receive information (denoted as information #1) indicating that the UE is allowed to execute an LTM cell switch if a selected cell is an LTM candidate cell. The UE may also receive information (denoted as information #2) indicating that the UE is allowed to perform CHO (e.g. a CHO based recovery) if a selected cell is a CHO candidate cell (e.g. a CHO candidate target cell) . For example, information #2 may be an attempt of conditional reconfiguration IE, e.g. attemptCondReconfig IE.

In some implementations of the method, in response to an occurrence of the failure (which may be at least one of the following: an RLF, a re-configuration with synchronization failure of the MCG, or a mobility from NR failure) , the UE may initiate a reestablishment procedure and perform the cell selection. If a selected cell is configured with CHO configuration, the UE may perform CHO (which may be named as "a CHO based recovery" ) . A CHO based recovery is a CHO procedure following the cell selection performed by the UE while a timer for cell selection (e.g. T311) is running. In response to an occurrence of a failure related to the CHO based recovery, the UE may initiate another reestablishment procedure and perform another cell selection. Then, the UE may transmit a reestablishment request (e.g. an RRC reestablishment request message) to a selected cell (which is selected by the UE via the abovementioned another cell selection) . A specific example is described in Embodiment 1 of Figure 10 as follows.

In some implementations of the method, the failure which occurs is an RLF of the MCG, "a re-configuration with synchronization failure of the MCG which is not related to LTM based recovery, " and/or a mobility from NR failure. "The re-configuration with synchronization failure of the MCG which is not related to LTM based recovery" does not include a failure related to LTM based recovery. "The re-configuration with synchronization failure of the MCG which is not related to LTM based recovery" includes a failure related to an LTM cell switch (e.g. an LTM failure) that is performed by the UE. An LTM based recovery is an LTM cell switch procedure following the cell selection performed by the UE while a timer for cell selection (e.g. T311) is running. In these implementations, the UE may perform CHO to a selected cell, if the selected cell (which is selected by the UE via the cell selection at operation 906 after an occurrence of the failure that does not include a failure related to LTM based recovery) is a CHO candidate cell. That is, in such implementations, a CHO based recovery is not allowed to be performed after a failure related to LTM based recovery. A specific example is described in Embodiment 2 of Figure 10 as follows.

In some implementations of the method, the failure related to LTM based recovery (e.g. an LTM recovery failure) may occur. In these implementations, the UE may release LTM configuration information, if the failure related to LTM based recovery occurs and if information #2 (e.g. attemptCondReconfig IE) is not configured to the UE.

In some implementations of the method, if the failure related to LTM based recovery (e.g. an LTM recovery failure) occurs, the UE may initiate a reestablishment procedure. The cell selection may be performed at operation 906 after initiating the reestablishment procedure. The UE may also start a timer for cell selection (e.g. T311) .

In some implementations of the method, if a selected cell is a CHO candidate cell, the UE may perform a CHO based recovery. If the selected cell is not the CHO candidate cell, the UE may transmit a reestablishment request (e.g. an RRC reestablishment request message) to the selected cell.

For example, if the failure related to LTM based recovery occurs, the UE may release LTM configuration information in some implementations, or may keep the LTM configuration information in some other implementations. A specific example is described in Embodiment 3 of Figure 10 as follows.

In some other implementations of the method, the failure related to LTM based recovery (e.g. an LTM recovery failure) may occur, and the cell selection is performed at operation 906 in response to the occurrence of the failure related to LTM based recovery. In other words, the UE does not initiate reestablishment procedure but perform cell selection directly in these implementations.

In some implementations of the method, the UE may perform an LTM based recovery. If the selected cell is configured with CHO configuration after the occurrence of the failure related to the LTM based recovery, the UE may perform a CHO based recovery. In response to an occurrence of a failure related to the CHO based recovery (which may also be named as a CHO failure or a CHO recovery failure) , the UE may transmit a reestablishment request (e.g. an RRC reestablishment request message) .

In some implementations of the method, after completing the reestablishment procedure towards a selected cell, the UE may transmit a failure report (e.g. an RLF report) to the target cell. The failure report may include information indicating at least one of the following:

(1) the failure related to the CHO based recovery (e.g. a CHO failure or a CHO recovery failure) occurs after the failure related to the LTM based recovery (e.g. an LTM recovery failure) ;

(2) the failure related to the LTM based recovery is followed by the CHO based recovery;

(3) the failure related to the LTM based recovery is followed by the failure related to the CHO based recovery; or

(4) the CHO based recovery is associated with the LTM based recovery, e.g. combination of LTM recovery and CHO recovery.

In some embodiments, the failure report further includes at least one of the following:

(1) ID information of a candidate cell for the LTM based recovery; or

(2) ID information of the candidate cell for the CHO based recovery. A specific example is described in Option #1 of the embodiments of Figure 11 as follows.

In some other implementations of the method, the UE may perform an LTM based recovery, and perform a CHO based recovery after the occurrence of the failure related to the LTM based recovery. After completing the CHO based recovery towards a target CHO cell, the UE may transmit a successful handover report (e.g. a Successful Handover Report (SHR) ) to the target CHO cell. For example, the successful handover report includes at least one of the following:

(1) the CHO based recovery is successfully completed after the failure related to the LTM based recovery;

(2) the failure related to the LTM based recovery is followed by successful CHO based recovery; or

(3) the successful CHO based recovery is associated with the LTM based recovery, e.g. combination of LTM recovery and CHO recovery.

In some embodiments, the successful handover report further includes at least one of the following:

(1) ID information of a candidate cell for the LTM based recovery; or

(2) ID information of the target CHO cell. A specific example is described in Option #2 of the embodiments of Figure 11 as follows.

It should be noted that the method described in Figure 9 describes possible implementations, and that the operations and the steps may be rearranged or otherwise eliminated or modified and that other implementations are possible, without departing from the spirit and scope of the disclosure.

Figure 10 illustrate a schematic diagram of an LTM cell switch procedure in accordance with some aspects of the present disclosure. Details described in all other embodiments of the present disclosure are applicable for the embodiments of Figure 10. Following text describe three specific embodiments of Figure 10 according to different cases, i.e. Embodiment 1, Embodiment 2, and Embodiment 3 as below.

Embodiment 1

Embodiment 1 assume that both an LTM based recovery and a CHO based recovery are supported, and only one attempt is allowed for the LTM based recovery or the CHO based recovery. Embodiment 1 solves an issue of whether LTM based recovery can be allowed after a CHO recovery failure occurs, and provides a solution in which an LTM based recovery is not allowed after a CHO recovery failure occurs.

In particular, in Embodiment 1, at operation 11, UE 1001 may access the network via Dual-connectivity (DC) including MCG and SCG. Regarding a DC scenario, UE 1001 accesses MN 1002 and SN 1003 via dual connectivity. In some implementations of operation 11, UE 1001 may send a measurement report to MN 1002.

At operation 12, UE 1001 may configuration information from MN 1002. For example, UE 1001 receives CHO configuration information for one or more CHO candidate cells from the serving MCG, e.g. PCell. UE 1001 may also receive MCG LTM configuration information for one or more LTM candidate cells from the serving MCG, e.g. PCell. The one or more CHO candidate cells may be the same as or different from the one or more LTM candidate cells. In some embodiments, UE 1001 may receive information (e.g. information #1) indicating that UE 1001 is allowed to execute an LTM cell switch if a selected cell is an LTM candidate cell. UE 1001 may also receive information (e.g. information #2) indicating that UE 1001 is allowed to perform CHO (e.g. a CHO based recovery) if a selected cell is a CHO candidate cell.

In some embodiments of operation 12, an attempt of conditional reconfiguration IE, i.e. attemptCondReconfig IE (e.g. information #2) , may be configured to UE 1001. If this IE is configured, UE 1001 may perform CHO (e.g. a CHO based recovery) based on the CHO configuration information if a selected cell is a CHO candidate cell (which is selected via the first cell selection performed by UE 1001 after the failure) . A CHO based recovery is a CHO procedure following the cell selection performed by the UE while a timer for cell selection (e.g. T311) is running.

In some embodiments of operation 12, an attempt of LTM switch IE, i.e. attemptLTM-Switch IE, may be configured to UE 1001. If this IE is configured, UE 1001 may execute an LTM cell switch (e.g. an LTM based recovery) if a selected cell is an LTM candidate cell. An LTM based recovery is an LTM cell switch following a cell selection performed by UE 1001 while a timer for cell selection, e.g. T311, was running.

At operation 13, UE 1001 may detect an RLF on MCG, a re-configuration with sync failure of the MCG, or a mobility from NR failure. The re-configuration with sync failure of the MCG may be a failure of traditional L3 handover triggered by reception of a handover command, a CHO failure (i.e. a failure related to CHO) , a CHO recovery failure (i.e. a failure related to CHO based recovery) , an LTM failure (i.e. a failure related to LTM) , or an LTM recovery failure (i.e. a failure related to LTM based recovery) . The re-configuration with sync failure of the MCG may be that a mobility timer, e.g. T304, expires in the case of a traditional handover, a CHO, or a MCG LTM. A traditional handover refers to the case that a UE receives a handover command from the serving MCG or the serving gNB. A traditional handover may also be named as a handover, a normal handover, or ordinary handover, or the like.

At operation 14, UE 1001 initiates a reestablishment procedure due to an RLF detection, an occurrence of the re-configuration with sync failure of the MCG, or an occurrence of the mobility from NR failure. UE 1001 may perform a cell selection and start a timer for cell selection, e.g. T311. Once UE 1001 selects a suitable cell, UE 1001 stops the timer for cell selection, e.g. T311. If the selected cell is configured with CHO configuration information, UE 1001 may perform CHO (i.e. a CHO based recovery) and starts a timer for CHO.

At operation 15, if the CHO based recovery fails (i.e. a CHO recovery failure occurs) , UE 1001 performs a reestablishment procedure. In some embodiments, after the CHO recovery failure occurs, UE 1001 may transmit an RRC reestablishment request message towards the selected cell regardless of whether the selected cell is configured with LTM configuration information or not. Namely, an LTM based recovery is not allowed after a CHO recovery failure in Embodiment 1.

Embodiment 2

Embodiment 2 solves an issue of whether a CHO based recovery is allowed after an LTM recovery failure, and provides a solution in which a CHO based recovery is not allowed after an LTM recovery failure.

In particular, in Embodiment 2, at operation 11, UE 1001 may access the network via Dual-connectivity (DC) including MCG and SCG. Regarding a DC scenario, UE 1001 accesses MN 1002 and SN 1003 via dual connectivity. In some implementations of operation 11, UE 1001 may send a measurement report to MN 1002.

At operation 12, UE 1001 may configuration information from MN 1002. For example, UE 1001 receives CHO configuration information for one or more CHO candidate cells from the serving MCG, e.g. PCell. UE 1001 may also receive MCG LTM configuration information for one or more LTM candidate cells from the serving MCG, e.g. PCell. The one or more CHO candidate cells may be the same as or different from the one or more LTM candidate cells.

In some embodiments of operation 12, an attempt of conditional reconfiguration IE, i.e. attemptCondReconfig IE, may be configured to UE 1001. If the attempt of conditional reconfiguration IE is configured, UE 1001 may perform CHO (e.g. a CHO based recovery) based on the CHO configuration information if a selected cell is a CHO candidate cell (which is selected via the first cell selection performed by UE 1001 after the failure) .

In some embodiments of operation 12, an attempt of LTM switch IE, i.e. attemptLTM-Switch IE, may be configured to UE 1001. If the attempt of LTM switch IE is configured, UE 1001 may execute an LTM cell switch (e.g. an LTM based recovery) if a selected cell is an LTM candidate cell.

At operation 13, UE 1001 may detect an RLF on MCG or a re-configuration with sync failure of the MCG. The re-configuration with sync failure of the MCG may be a failure of traditional L3 handover triggered by reception of a handover command, a CHO failure (i.e. a failure related to CHO) , a CHO recovery failure (i.e. a failure related to CHO based recovery) , an LTM failure (i.e. a failure related to LTM) , or an LTM recovery failure (i.e. a failure related to LTM based recovery) . The re-configuration with sync failure of the MCG may be that a mobility timer, e.g. T304, expires in the case of a traditional handover, a CHO, or a MCG LTM. A traditional handover refers to the case that a UE receives a handover command from the serving MCG or the serving gNB. A traditional handover may also be named as a handover, a normal handover, or ordinary handover, or the like.

At operation 14, UE 1001 initiates a reestablishment procedure due to detection of the RLF on MCG or an occurrence of the re-configuration with sync failure of the MCG. UE 1001 may perform a cell selection and start a timer for cell selection, e.g. T311. Once UE 1001 selects a suitable cell, UE 1001 stops the timer for cell selection, e.g. T311.

At operation 14, different operations may be performed in different embodiments of Embodiment 2. For example:

(1) In some embodiments, if the cell selection is triggered by detecting an RLF of the MCG or a re-configuration with sync failure of the MCG, and if the selected cell is configured with MCG LTM configuration information, UE 1001 performs an LTM (i.e. an LTM based recovery) and starts a timer for LTM, e.g. T304. An LTM based recovery is an LTM cell switch following a cell selection performed by UE 1001 while a timer for cell selection, e.g. T311, was running.

(2) In some other embodiments, if the cell selection is triggered by detecting an RLF of the MCG, a re-configuration with sync failure of the MCG which is not related to LTM based recovery, or a mobility from NR failure, and if the selected cell is configured with CHO configuration information, UE 1001 performs CHO (i.e. a CHO based recovery) . In such embodiments, "the re-configuration with sync failure of the MCG which is not related to LTM based recovery" does not include an LTM recovery failure. That is, a CHO based recovery is not allowed after an LTM recovery failure. A CHO based recovery is a CHO procedure following the cell selection performed by UE 1001 while a timer for cell selection (e.g. T311) is running.

At operation 15, if the selected cell is configured with MCG LTM configuration information, UE 1001 performs an LTM based recovery. If the LTM based recovery fails (i.e. an LTM recovery failure occurs) , UE 1001 may perform a cell selection and transmits a reestablishment request (e.g. an RRC reestablishment request message) to the selected cell.

Embodiment 3

Embodiment 3 assume that both an LTM based recovery and a CHO based recovery are supported, and only one attempt is allowed for the LTM based recovery or the CHO based recovery. Embodiment 3 solves an issue of whether an LTM based recovery can be allowed after a CHO recovery failure occurs, and provides a solution in which an LTM based recovery is not allowed after a CHO recovery failure occurs.

In particular, in Embodiment 3, at operation 11, UE 1001 may access the network via Dual-connectivity (DC) including MCG and SCG. Regarding a DC scenario, UE 1001 accesses MN 1002 and SN 1003 via dual connectivity. In some implementations of operation 11, UE 1001 may send a measurement report to MN 1002.

At operation 12, UE 1001 may receive configuration information from MN 1002. For example, UE 1001 receives CHO configuration information for one or more CHO candidate cells from the serving MCG, e.g. PCell. UE 1001 may also receive MCG LTM configuration information for one or more LTM candidate cells from the serving MCG, e.g. PCell. The one or more CHO candidate cells may be the same as or different from the one or more LTM candidate cells.

In some embodiments of operation 12, an attempt of conditional reconfiguration IE, i.e. attemptCondReconfig IE, may be configured to UE 1001. If the attempt of conditional reconfiguration IE is configured, UE 1001 may perform CHO based on the CHO configuration information if a selected cell is a CHO candidate cell (which is selected via the first cell selection performed by UE 1001 after the failure) .

In some embodiments of operation 12, an attempt of LTM switch IE, i.e. attemptLTM-Switch IE, may be configured to UE 1001. If the attempt of LTM switch IE is configured, UE 1001 may execute an LTM cell switch if a selected cell is an LTM candidate cell.

At operation 14, UE 1001 initiates a reestablishment procedure due to an RLF detection or an occurrence of the re-configuration with sync failure of the MCG. UE 1001 may perform a cell selection and start the timer for cell selection, e.g. T311. Once UE 1001 selects a suitable cell, UE 1001 stops the timer for cell selection, e.g. T311.

At operation 14, there may be different operations performed in different embodiments of Embodiment 3. For example:

(2) In some other embodiments, if the cell selection is triggered by detecting an RLF of the MCG, a re-configuration with sync failure of the MCG which is not related to LTM based recovery, or mobility from NR failure, and if the selected cell is configured with CHO configuration information, UE 1001 performs CHO (i.e. a CHO based recovery) . In other words, in these embodiments, if the cell selection is triggered by detecting an RLF of the MCG or a re-configuration with sync failure of the MCG (except an LTM cell switch triggered by cell selection) or a mobility from NR failure, and if the selected cell is configured with CHO configuration information, UE 1001 performs CHO (i.e. a CHO based recovery) . In such embodiments, "the re-configuration with sync failure of the MCG which is not related to LTM based recovery" does not include an LTM recovery failure. That is, a CHO based recovery is not allowed after an LTM recovery failure. A CHO based recovery is a CHO procedure following the cell selection performed by the UE while a timer for cell selection (e.g. T311) is running.

At operation 15, if the selected cell is configured with MCG LTM configuration information, UE 1001 performs an LTM based recovery. If the LTM based recovery fails (i.e. an LTM recovery failure occurs) , UE 1001 may perform a cell selection. Then, there may be different operations performed in different embodiments of Embodiment 3. For example:

(1) If the selected cell is configured with CHO, UE 1001 performs CHO (i.e. a CHO based recovery) .

(2) Whether an LTM based recovery is allowed after a CHO based recovery can be configured by network. For example, information to indicate whether an LTM based recovery is allowed after a CHO based recovery can be added in an RRC reconfiguration message that is transmitted to UE 1001. In some embodiments, if UE 1001 receives information indicating that an LTM based recovery is allowed after a CHO based recovery,

(3) UE 1001 may release the LTM configuration information upon an occurrence of the failure related to LTM based recovery (e.g. an LTM recovery failure) and if attemptCondReconfig IE (e.g. information #2) is not configured to UE 1001.

(4) In some embodiments, UE 1001 may re-initiate a reestablishment procedure after the LTM recovery failure. Then, UE 1001 performs a cell selection and starts a timer for cell selection (e.g. T311) . If the selected suitable cell is configured with CHO configuration information (i.e. a CHO candidate cell) , UE 1001 performs a CHO based recovery. Otherwise, if the selected cell is not configured with CHO configuration information (i.e. not the CHO candidate cell) , UE 1001 performs a re-establishment procedure.

(5) In an embodiment, after the LTM recovery failure occurs, if UE 1001 initiates a reestablishment procedure, UE 1001 may release all the LTM configuration information. Otherwise, in another embodiment, UE 1001 may keep the LTM configuration information.

(6) Alternatively, in some other embodiments, after the LTM recovery failure occurs, UE 1001 does not initiate a reestablishment procedure, but perform a cell selection directly.

Figure 11 illustrates another schematic diagram of an LTM cell switch procedure in accordance with some aspects of the present disclosure. The embodiments of Figure 11 provide a MRO mechanism for the case that CHO based recovery is allowed after LTM recovery failure, including a CHO recovery failure after LTM recovery failure and a successful CHO recovery after LTM recovery failure. Details described in all other embodiments of the present disclosure are applicable for the embodiments of Figure 11.

In particular, at operation 111, UE 1101 may access the network via Dual-connectivity (DC) including MCG and SCG. Regarding a DC scenario, UE 1101 accesses MN 1102 and SN 1103 via dual connectivity. In some implementations of operation 111, UE 1101 may send a measurement report to MN 1102.

At operation 112, UE 1101 may receive configuration information from MN 1102. For example, UE 1101 receives CHO configuration information for one or more CHO candidate cells from the serving MCG, e.g. PCell. UE 1101 may also receive MCG LTM configuration information for one or more LTM candidate cells from the serving MCG, e.g. PCell. The one or more CHO candidate cells may be the same as or different from the one or more LTM candidate cells.

In some embodiments of operation 112, an attempt of conditional reconfiguration IE, i.e. attemptCondReconfig IE, may be configured to UE 1101. If the attempt of conditional reconfiguration IE is configured, UE 1101 may perform CHO based on the CHO configuration information if a selected cell is a CHO candidate cell (which is selected via the first cell selection performed by UE 1101 after the failure) .

In some embodiments of operation 112, an attempt of LTM switch IE, i.e. attemptLTM-Switch IE, may be configured to UE 1101. If the attempt of LTM switch IE is configured, UE 1101 may execute an LTM cell switch if a selected cell is an LTM candidate cell.

At operation 113, UE 1101 may detect an RLF on MCG, a re-configuration with sync failure of the MCG, or a mobility from NR failure. The re-configuration with sync failure of the MCG may be a failure of traditional L3 handover triggered by reception of a handover command, a CHO failure (i.e. a failure related to CHO) , a CHO recovery failure (i.e. a failure related to CHO based recovery) , an LTM failure (i.e. a failure related to LTM) , or an LTM recovery failure (i.e. a failure related to LTM based recovery) . The re-configuration with sync failure of the MCG may be that a mobility timer, e.g. T304, expires in the case of a traditional handover, a CHO, or a MCG LTM. A traditional handover refers to the case that a UE receives a handover command from the serving MCG or the serving gNB. A traditional handover may also be named as a handover, a normal handover, or ordinary handover, or the like.

At operation 114, UE 1101 initiates a reestablishment procedure due to an RLF detection or an occurrence of the re-configuration with sync failure of the MCG. UE 1101 may perform a cell selection and start the timer for cell selection, e.g. T311. Once UE 1101 selects a suitable cell, UE 1101 stops the timer for cell selection, e.g. T311.

At operation 114, there may be different operations performed in different embodiments. For example:

(1) In some embodiments, if the cell selection is triggered by detecting an RLF of the MCG or a re-configuration with sync failure of the MCG, and if the selected cell is configured with MCG LTM configuration information, UE 1101 performs an LTM (i.e. an LTM based recovery) and starts a timer for LTM, e.g. T304. An LTM based recovery is an LTM cell switch following a cell selection performed by UE 1101 while a timer for cell selection, e.g. T311, was running.

(2) In some other embodiments, if the cell selection is triggered by detecting an RLF of the MCG, a re-configuration with sync failure of the MCG which is not related to LTM based recovery, or mobility from NR failure, and if the selected cell is configured with CHO configuration information, UE 1101 performs CHO (i.e. a CHO based recovery) . In such embodiments, "the re-configuration with sync failure of the MCG which is not related to LTM based recovery" does not include an LTM recovery failure. That is, a CHO based recovery is not allowed after an LTM recovery failure. A CHO based recovery is a CHO procedure following the cell selection performed by the UE while a timer for cell selection (e.g. T311) is running.

At operation 115, if the selected cell is configured with MCG LTM configuration information, UE 1101 performs an LTM based recovery. If the LTM based recovery fails (i.e. an LTM recovery failure occurs) , UE 1101 may perform a cell selection. In some embodiments, if the selected cell is configured with CHO, UE 1101 performs CHO (i.e. a CHO based recovery) .

After operation 115, different operations may be performed at operation 116 in different embodiments of Figure 10, i.e. Option #1 and Option #2.

Option #1

In Option #1, if the CHO based recovery fails (i.e. a CHO recovery failure occurs) , UE 1101 performs a reestablishment procedure at operation 116. In some embodiments, after UE 1101 re-establishes towards a cell, UE 1101 may transmit a failure report (e.g. an RLF report) to the re-established base station (e.g. a target gNB) . The failure report includes information to indicate that a CHO failure (i.e. a CHO recovery failure) occurs after an LTM recovery failure. For example, information regarding the candidate cell for LTM recovery may be included in the failure report. The target cell for CHO recovery may be included in the failure report. After receiving the failure report, the network side may optimize and configure the related configuration information and parameters.

Option #2

In Option #2, if UE 1101 successfully accesses the target cell via CHO at operation 115, UE 1101 may be triggered to report a successful handover report, e.g. a Successful Handover Report (SHR) , to the target gNB at operation 116. The successful handover report may include information to indicate a successful CHO recovery after an LTM recovery failure. For example, information regarding the candidate cell for LTM recovery may be included in the successful handover report. The target cell for CHO recovery may be included in the successful handover report. After receiving the successful handover report, the network side may optimize and configure the related configuration information and parameters.

The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

A master node (MN) , comprising:

at least one memory; and

at least one processor coupled to the at least one memory and configured to cause the MN to:

receive, from a user equipment (UE) , UE capability information related to L1/L2-Triggered Mobility (LTM) ;

transmit a request for SN addition to a secondary node (SN) , wherein the request for SN addition includes the UE capability information and a first identifier (ID) of the UE that is unique within the MN;

receive, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN; and

transmit, to the UE, configuration information related to the SN including the SCG configuration information.
The MN of Claim 1, wherein the UE capability information indicates that the UE supports an inter-centralized unit (CU) LTM.
The MN of Claim 1, wherein the at least one processor is configured to cause the MN to transmit, to the SN, one of the following:

an inter-CU master cell group (MCG) LTM is configured for the UE;

inter-CU SCG LTM configuration is not allowed to be configured for the UE; or

an inter-CU SCG LTM is not allowed.
The MN of any of Claims 1-3, wherein if the MN configures the UE to release configuration information for inter-CU MCG LTM, the at least one processor is configured to cause the MN to transmit, to the SN, one of the following:

the configuration information for inter-CU MCG LTM is released;

the inter-CU MCG LTM is not configured for the UE; or

the inter-CU SCG LTM is allowed.
The MN of Claim 1, wherein the at least one processor is configured to cause the MN to receive, from the SN, a request message including SCG LTM configuration.
The MN of Claim 5, wherein the at least one processor is configured to cause the MN to transmit, to the SN, a first message for refusing the request message.
The MN of Claim 6, wherein the first message includes one of the following:

an inter-CU MCG LTM is configured for the UE;

inter-CU SCG LTM configuration is not allowed to be configured for the UE; or

an inter-CU SCG LTM is not allowed.
The MN of Claim 6, wherein the first message is an SN modification refuse message.
A secondary node (SN) , comprising:

at least one memory; and

at least one processor coupled to the at least one memory and configured to cause the SN to:

receive a request for SN addition from a master node (MN) , wherein the request for SN addition includes user equipment (UE) capability information and a first identifier (ID) of a UE that is unique within the MN, wherein the UE capability information is related to L1/L2-Triggered Mobility (LTM) ; and

transmit an acknowledge message for SN addition request to the MN, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN.
The SN of Claim 9, wherein the UE capability information indicates that the UE supports an inter-centralized unit (CU) LTM.
The SN of Claim 9 or Claim 10, wherein the at least one processor is configured to cause the SN to receive, from the MN, one of the following:

an inter-CU master cell group (MCG) LTM is configured for the UE;

inter-CU SCG LTM configuration is not allowed to be configured for the UE; or

an inter-CU SCG LTM is not allowed.
The SN of Claim 11, wherein the at least one processor is configured to cause the SN to consider one of the following:

the inter-CU MCG LTM is configured for the UE;

the inter-CU SCG LTM configuration is not allowed to be configured for the UE;or

the inter-CU SCG LTM is not allowed.
The SN of any of Claims 9-12, wherein the at least one processor is configured to cause the SN to receive, from the MN, one of the following:

configuration information for inter-CU MCG LTM is released;

the inter-CU MCG LTM is not configured for the UE; or

the inter-CU SCG LTM is allowed.
The SN of Claim 13, wherein the at least one processor is configured to cause the SN to consider one of the following:

the configuration information for inter-CU MCG LTM is released;

the inter-CU MCG LTM is not configured for the UE; or

the inter-CU SCG LTM is allowed.
The SN of Claim 9 or Claim 10, wherein the at least one processor is configured to cause the SN to transmit, to the MN, a request message including SCG LTM configuration.
The SN of Claim 15, wherein the at least one processor is configured to cause the SN to receive, from the MN, a first message for refusing the request message.
The SN of Claim 16, wherein the first message includes one of the following:

an inter-CU MCG LTM is configured for the UE; or

inter-CU SCG LTM configuration is not allowed to be configured for the UE; or

an inter-CU SCG LTM is not allowed.
The SN of Claim 17, wherein the at least one processor is configured to cause the SN to consider one of the following:

the inter-CU MCG LTM is configured for the UE; or

the inter-CU SCG LTM configuration is not allowed to be configured for the UE;or

the inter-CU SCG LTM is not allowed.
A method performed by a master node (MN) , comprising:

receiving, from a user equipment (UE) , UE capability information related to L1/L2-Triggered Mobility (LTM) ;

transmitting a request for SN addition to a secondary node (SN) , wherein the request for SN addition includes the UE capability information and a first identifier (ID) of the UE that is unique within the MN;

receiving, from the SN, an acknowledge message for SN addition request, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN; and

transmitting, to the UE, configuration information related to the SN including the SCG configuration information.
A method performed by a secondary node (SN) , comprising:

receiving a request for SN addition from a master node (MN) , wherein the request for SN addition includes user equipment (UE) capability information and a first identifier (ID) of a UE that is unique within the MN, wherein the UE capability information is related to L1/L2-Triggered Mobility (LTM) ; and

transmitting an acknowledge message for SN addition request to the MN, wherein the acknowledge message includes secondary cell group (SCG) configuration information and a second ID of the UE that is unique within the SN.