WO2025092005A1

WO2025092005A1 - Methods and apparatuses of a mobility robustness optimization (mro) mechanism for an l1/l2-triggered mobility (ltm) procedure or a subsequent ltm procedure

Info

Publication number: WO2025092005A1
Application number: PCT/CN2024/103666
Authority: WO
Inventors: Le Yan; Mingzeng Dai; Lianhai WU
Original assignee: Lenovo (Beijing) Limited
Priority date: 2024-07-04
Filing date: 2024-07-04
Publication date: 2025-05-08

Abstract

Various aspects of the present disclosure relate to methods and apparatuses of a mobility robustness optimization (MRO) mechanism for an L1/L2 -Triggered Mobility (LTM) procedure or a subsequent LTM procedure. According to an embodiment of the present disclosure, a unit of a base station (BS) includes at least one memory and at least one processor coupled to the at least one memory and configured to cause the unit to: obtain information regarding whether an LTM cell switch to wrong or sub-optimal beam occurs.

Description

METHODS AND APPARATUSES OF A MOBILITY ROBUSTNESS OPTIMIZATION (MRO) MECHANISM FOR AN L1/L2-TRIGGERED MOBILITY (LTM) PROCEDURE OR A SUBSEQUENT LTM PROCEDURE

TECHNICAL FIELD

The present disclosure relates to wireless communications, and more specifically to methods and apparatuses of a mobility robustness optimization (MRO) mechanism for an L1/L2-Triggered Mobility (LTM) procedure or a subsequent LTM procedure.

BACKGROUND

A wireless communications system may include one or multiple network communication devices, such as base stations, 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 a lower layer message, the lower layer message is an LTM cell switch command (i.e. LTM cell switch command MAC CE) . 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.

In the present disclosure, LTM may also be named as lower layer-Triggered Mobility 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 inter-CU LTM may also be named as inter-BS LTM, inter-gNB LTM, or the like. An intra-CU LTM may also be named as intra-BS LTM, intra-gNB LTM, or the like.

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 unit of a base station (BS) . The unit includes at least one memory; and at least one processor coupled to the at least one memory and configured to cause the unit to: obtain information regarding whether a L1/L2-Triggered Mobility (LTM) cell switch to wrong or sub-optimal beam occurs.

In some implementations of the unit described herein, to obtain the information, the at least one processor is configured to cause the unit to: receive first information related to a connection failure, wherein the connection failure occurs during an LTM cell switch execution or shortly after a successful completion of the LTM cell switch execution.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, the at least one processor is configured to cause the CU to further perform at least one of: determining whether an LTM cell switch to wrong or sub-optimal beam occurs; or transmitting the first information to a distributed unit (DU) of the BS.

In some implementations of the CU described herein, the at least one processor is configured to cause the CU to determine that the LTM cell switch to wrong or sub-optimal beam occurs in case that: the connection failure occurs during the LTM cell switch execution, or the connection failure occurs shortly after the successful completion of the LTM cell switch execution; and a user equipment (UE) attempts to recover or re-establish or reconnect a radio link connection in a cell where the connection failure occurs, wherein a first beam where the connection failure occurred and a second beam where the UE successfully recover or re-establish or reconnect a radio link connection are different beams but belong to a same cell.

In some implementations of the CU described herein, in response to determining that the LTM cell switch to wrong or sub-optimal beam occurs, the at least one processor is configured to cause the CU to transmit to a source DU of the BS: information indicating that the LTM cell switch to wrong or sub-optimal beam occurs; failure type information concerning a wrong or sub-optimal beam selection at the source DU; or a combination thereof.

In some implementations of the CU described herein, the at least one processor is configured to cause the CU to transmit the first information to a source DU of the BS.

In some implementations of the CU described herein, the at least one processor is configured to cause the CU to receive from the source DU: information indicating that the LTM cell switch to wrong or sub-optimal beam occurs; failure type information concerning a wrong or sub-optimal beam selection at the source DU; or a combination thereof.

In some implementations of the unit described herein, the first information includes information related to a beam where a beam failure recovery is performed.

In some implementations of the unit described herein, the unit is a source distributed unit (DU) of the BS, and the at least one processor is configured to cause the source DU to perform at least one of following operations: receiving at least one of the following: the first information related to the connection failure; information indicating that an LTM cell switch to wrong or sub-optimal beam occurs; or failure type information concerning a wrong or sub-optimal beam selection at the source DU; or determining whether the LTM cell switch to wrong or sub-optimal beam occurs.

In some implementations of the source DU described herein, the at least one processor is configured to cause the source DU to determine that the LTM cell switch to wrong or sub-optimal beam occurs in case that: the connection failure occurs during the LTM cell switch execution, or the connection failure occurs shortly after the successful completion of the LTM cell switch execution; and a user equipment (UE) attempts to recover or re-establish or reconnect a radio link connection in a cell where the connection failure occurs, wherein a first beam where the connection failure occurred and a second beam where the UE successfully recover or re-establish or reconnect a radio link connection are different beams but belong to a same cell.

In some implementations of the source DU described herein, in response to receiving the first information, the at least one processor is configured to cause the source DU to perform a root cause analysis or determine whether the LTM cell switch to wrong or sub-optimal beam occurs.

In some implementations of the source DU described herein, in response to receiving the first information and in response to determining that the LTM cell switch to wrong or sub-optimal beam occurs, the at least one processor is configured to cause the source DU to transmit to a centralized unit (CU) of the BS: information indicating that the LTM cell switch to wrong or sub-optimal beam occurs; failure type information concerning a wrong or sub-optimal beam selection at the source DU; or a combination thereof.

In some implementations of the source DU described herein, in response to determining that the LTM cell switch to wrong or sub-optimal beam occurs, the at least one processor is configured to cause the source DU to modify beam configuration information of a target cell in a lower layer message.

In some implementations of the unit described herein, the at least one processor is configured to cause the unit to: obtain configuration information of at least one trigger condition for a user equipment (UE) to store or report successful L1/L2-Triggered Mobility (LTM) related information, wherein the successful LTM related information is related to a near-failure successful LTM cell switch or subsequent LTM cell switch; and transmit the configuration information.

In some implementations of the unit described herein, the configuration information of the at least one trigger condition includes: a first condition concerning that an early timing advance (TA) acquisition procedure is not configured to the UE; a second condition concerning that the early TA acquisition procedure is not triggered by a physical downlink control channel (PDCCH) order; a third condition concerning that a UE-based TA measurement is not configured to the UE; a fourth condition concerning that a TA value acquired in the early TA acquisition procedure is not valid; a fifth condition concerning that a TA value provided in a lower layer message is not valid; a sixth condition concerning that no valid TA value is provided in the lower layer message; a seventh condition concerning that a TA value measured by the UE is not valid; an eighth condition concerning that no valid TA value is available via the UE-based TA measurement; a ninth condition concerning that a random access channel (RACH) -less LTM cell switch is not performed; a tenth condition concerning that the RACH-less LTM cell switch is not successful; a threshold related with accessing to a target cell; an eleventh condition concerning that a beam failure recovery is performed during an LTM cell switch procedure or a subsequent LTM cell switch procedure; a timer T310 related threshold related with a ratio between a value of elapsed running time of a timer T310 and a configured length value of the timer T310; a timer T312 related threshold related with a ratio between a value of elapsed running time of a timer T312 and a configured length value of the timer T312; a timer T304 related threshold related with a ratio between a value of elapsed running time of a timer T304 and a configured length value of the timer T304; or a combination thereof.

In some implementations of the unit described herein, the at least one processor is configured to cause the unit to receive successful LTM related information, and wherein the successful LTM related information includes at least one of: information related to a beam where a beam failure recovery is performed; a cause value for storing or reporting the successful LTM related information; time duration between receiving a lower layer message and successfully accessing to a target cell; time duration between receiving a radio resource control (RRC) reconfiguration message and successfully accessing to the target cell; or a time point for successfully accessing to the target cell.

In some implementations of the unit described herein, the successful LTM related information is included in: a successful handover report (SHR) ; a successful primary secondary cell (PSCell) addition or change report (SPR) ; or a combination thereof.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, and to obtain the configuration information, the at least one processor is configured to cause the CU to: generate the configuration information; or receive the configuration information from at least one DU, wherein the configuration information is generated by at least one of a source DU or a candidate DU of the BS.

In some implementations of the CU described herein, the configuration information is transmitted to the UE via: a radio resource control (RRC) message; a lower layer message; or a combination thereof.

In some implementations of the unit described herein, the unit is a source distributed unit (DU) of the BS, to obtain the configuration information, the at least one processor is configured to cause the source DU to receive the configuration information from a centralized unit (CU) of the BS, and wherein the configuration information is generated by at least one of the CU or a candidate DU of the BS.

In some implementations of the unit described herein, the unit is a source distributed unit (DU) of the BS, to obtain the configuration information, the at least one processor is configured to cause the source DU to generate the configuration information.

In some implementations of the source DU described herein, to transmit the configuration information, the at least one processor is configured to cause the source DU to transmit the configuration information to the CU, or transmit the configuration information to the UE, wherein the configuration information transmitted to the UE is included in: a radio resource control (RRC) message; a lower layer message; or a combination thereof.

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: obtain information regarding whether a L1/L2-Triggered Mobility (LTM) cell switch to wrong or sub-optimal beam occurs.

Some implementations of the present disclosure provide a method performed by a unit of a base station (BS) . The method includes: obtaining information regarding whether a L1/L2-Triggered Mobility (LTM) cell switch to wrong or sub-optimal beam occurs.

Some implementations of the present disclosure provide a user equipment (UE) for wireless communication. 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: store and report information related to a beam where a beam failure recovery is performed during a L1/L2-Triggered Mobility (LTM) cell switch procedure or a subsequent LTM cell switch procedure.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to store and report the information related to the beam in a radio link failure (RLF) report.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to obtain a first configuration of at least one trigger condition to store or report successful LTM related information, wherein the successful LTM related information is related to a near-failure successful LTM cell switch or subsequent LTM cell switch, and wherein to obtain the first configuration, the at least one processor is configured to cause the UE to: obtain the first configuration by pre-configuration; or receive the first configuration from a network equipment (NE) .

In some implementations of the UE described herein, the first configuration is received from the NE via: a radio resource control (RRC) message; a lower layer message; or a combination thereof.

In some implementations of the UE described herein, the first configuration is associated with at least one trigger condition for the UE to store or report the successful LTM related information, and wherein the first configuration includes: a first condition concerning that an early timing advance (TA) acquisition procedure is not configured to the UE; a second condition concerning that the early TA acquisition procedure is not triggered by a physical downlink control channel (PDCCH) order; a third condition concerning that a UE-based TA measurement is not configured to the UE; a fourth condition concerning that a TA value acquired in the early TA acquisition procedure is not valid; a fifth condition concerning that a TA value provided in a lower layer message is not valid; a sixth condition concerning that no valid TA value is provided in the lower layer message; a seventh condition concerning that a TA value measured by the UE is not valid; an eighth condition concerning that no valid TA value is available via the UE-based TA measurement; a ninth condition concerning that a random access channel (RACH) -less LTM cell switch is not performed; a tenth condition concerning that the RACH-less LTM cell switch is not successful; a threshold related with accessing to a target cell; an eleventh condition concerning that a beam failure recovery is performed during an LTM cell switch procedure or a subsequent LTM cell switch procedure; a timer T310 related threshold related with a ratio between a value of elapsed running time of a timer T310 and a configured length value of the timer T310; a timer T312 related threshold related with a ratio between a value of elapsed running time of a timer T312 and a configured length value of the timer T31; a timer T304 related threshold related with a ratio between a value of elapsed running time of a timer T304 and a configured length value of the timer T304; or a combination thereof.

In some implementations of the UE described herein, the successful LTM related information includes: the information related to the beam where the beam failure recovery is performed; a cause value for storing or reporting the successful LTM related information; time duration between receiving a lower layer message and successfully accessing to a target cell; time duration between receiving a radio resource control (RRC) reconfiguration message and successfully accessing to the target cell; a time point for successfully accessing to the target cell; or a combination thereof.

In some implementations of the UE described herein, the successful LTM related information is included in: a successful handover report (SHR) ; a successful primary secondary cell (PSCell) addition or change report (SPR) ; or a combination thereof.

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: store and report information related to a beam where a beam failure recovery is performed during a L1/L2-Triggered Mobility (LTM) cell switch procedure or a subsequent LTM cell switch procedure.

Some implementations of the present disclosure provide a method performed by a user equipment (UE) for wireless communication. The method includes: storing and reporting information related to a beam where a beam failure recovery is performed during a L1/L2-Triggered Mobility (LTM) cell switch procedure or a subsequent LTM cell switch procedure.

Some implementations of the present disclosure provide a unit of a base station (BS) . The unit includes at least one memory; and at least one processor coupled to the at least one memory and configured to cause the unit to: obtain first user equipment (UE) history information (UHI) regarding a L1/L2-Triggered Mobility (LTM) cell switch or a subsequent LTM cell switch of a UE; and store the first UHI or update previously stored UHI based on the first UHI.

In some implementations of the unit described herein, the LTM cell switch or the subsequent LTM cell switch is one of: an intra-DU LTM cell switch or an intra-DU subsequent LTM cell switch; or an inter-DU LTM cell switch or an inter-DU subsequent LTM cell switch.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the CU to collect the first UHI: upon receiving a DU-CU cell switch notification message upon receiving an access success message; upon receiving a uplink (UL) radio resource control (RRC) message transfer message; or a combination thereof.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the CU to: calculate that time duration of the UE staying in a first cell equals to time duration between receiving an access success message for the first cell and receiving a DU-CU cell switch notification message for a next target cell, wherein the next target cell is a cell where the UE stayed after the first cell; calculate that the time duration of the UE staying in the first cell equals to time duration between receiving a DU-CU cell switch notification message for the first cell and receiving the DU-CU cell switch notification message for the next target cell; calculate that the time duration of the UE staying in the first cell equals to time duration between receiving the access success message for the first cell and receiving a access success message for the next target cell; or calculate that the time duration of the UE staying in the first cell equals to time duration between receiving a UL RRC message transfer message for the first cell and receiving a UL RRC message transfer message for the next target cell.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the CU to: calculate that time duration of the UE staying in a first cell equals to time duration between receiving an access success message for the first cell and receiving a DU-CU cell switch notification message for a next target cell, wherein the next target cell is a cell where the UE stayed after the first cell; calculate that the time duration of the UE staying in the first cell equals to time duration between receiving a UL RRC message transfer message for the first cell and receiving the DU-CU cell switch notification message for the next target cell; calculate that the time duration of the UE staying in the first cell equals to time duration between receiving a DU-CU cell switch notification message for the first cell and receiving the DU-CU cell switch notification message for the next target cell; calculate that the time duration of the UE staying in the first cell equals to time duration between receiving the access success message for the first cell and receiving an access success message for the next target cell; or calculate that the time duration of the UE staying in the first cell equals to time between receiving a UL RRC message transfer message for the first cell and receiving a UL RRC message transfer message for the next target cell.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the CU to: receive the first UHI from a distributed unit (DU) of the BS, wherein the first UHI is collected by the DU; or receive the first UHI from the UE, wherein the first UHI is collected by the UE.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, and the at least one processor is configured to cause the CU to transmit the first UHI to a first distributed unit (DU) of the BS, and wherein the first DU is: a source DU of the BS; a candidate DU of the BS; a target DU of the BS; a serving DU of the BS; a DU of the BS where the ping-pong issue occurs; or a combination thereof.

In some implementations of the unit described herein, the unit is a distributed unit (DU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the DU to collect the first UHI: upon transmitting a lower layer message; upon transmitting a DU-CU cell switch notification message; upon transmitting an access success message; upon receiving a radio resource control (RRC) reconfiguration complete message after successfully accessing to a target cell; or upon transmitting a uplink (UL) RRC message transfer message.

In some implementations of the unit described herein, the unit is a distributed unit (DU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the DU to: calculate that time duration of the UE staying in a first cell equals to time duration between transmitting an access success message to a centralized unit (CU) of the BS for the first cell and transmitting a lower layer message to the UE for a next target cell, wherein the next target cell is a cell where the UE stayed after the first cell; calculate that the time duration of the UE staying in the first cell equals to time duration between transmitting the lower layer message to the UE for the first cell and transmitting the lower layer message to the UE for the next target cell; calculate that the time duration of the UE staying in the first cell equals to time duration between transmitting a DU-CU cell switch notification message to the CU for the first cell and transmitting a DU-CU cell switch notification message to the CU for the next target cell; calculate that the time duration of the UE staying in the first cell equals to time duration between transmitting an access success message to the CU for the first cell and transmitting an access success message to the CU for the next target cell; or calculate that the time duration of the UE staying in the first cell equals to time duration between transmitting a UL RRC message transfer message to the CU for the first cell and transmitting a UL RRC message transfer message to the CU for the next target cell.

In some implementations of the unit described herein, the unit is a distributed unit (DU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the DU to: calculate that time duration of the UE staying in a first cell equals to time duration between transmitting an access success message to a centralized unit (CU) of the BS for the first cell and transmitting a lower layer message to the UE for a next target cell, wherein the next target cell is a cell where the UE stayed after the first cell; calculate that the time duration of the UE staying in the first cell equals to time duration between transmitting a UL RRC message transfer message to the CU for the first cell and transmitting the lower layer message to the UE for the next target cell; or calculate that the time duration of the UE staying in the first cell equals to time duration between receiving an RRC reconfiguration complete message after successfully accessing to the first cell and transmitting the lower layer message to the UE for the next target cell.

In some implementations of the unit described herein, the unit is a distributed unit (DU) of the BS, and to obtain the first UHI, the at least one processor is configured to cause the DU to: receive the first UHI from a centralized unit (CU) of the BS, wherein the first UHI is collected by the CU; or receive the first UHI from the UE, wherein the first UHI is collected by the UE.

In some implementations of the unit described herein, the unit is a distributed unit (DU) of the BS, and the at least one processor is configured to cause the DU to transmit the first UHI to a centralized unit (CU) of the BS: upon collecting the first UHI; upon updating the first UHI; or upon the UE switches to another cell or another DU.

In some implementations of the unit described herein, the at least one processor is configured to cause the unit to detect whether a ping-pong issue associated with the LTM cell switch or the subsequent LTM cell switch occurs.

In some implementations of the unit described herein, the unit is a centralized unit (CU) of the BS, and if the ping-pong issue occurs, the at least one processor is configured to cause the CU to transmit information indicating the ping-pong issue to: a source distributed unit (DU) of the BS; a candidate DU of the BS; a target DU of the BS; a serving DU of the BS; a DU of the BS where the ping-pong issue occurs; or a combination thereof.

In some implementations of the unit described herein, the unit is a distributed unit (DU) of the BS, and if the ping-pong issue occurs, the at least one processor is configured to cause the DU to transmit information indicating the ping-pong issue to a centralized unit (CU) of the BS.

In some implementations of the unit described herein, the at least one processor is configured to cause the unit to receive information indicating a ping-pong issue associated with the LTM cell switch or the subsequent LTM cell switch.

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: obtain first user equipment (UE) history information (UHI) regarding a L1/L2-Triggered Mobility (LTM) cell switch or a subsequent LTM cell switch of a UE; and store the first UHI or update previously stored UHI based on the first UHI.

Some implementations of the present disclosure provide a method performed by a unit of a base station (BS) . The method includes: obtaining first user equipment (UE) history information (UHI) regarding a L1/L2-Triggered Mobility (LTM) cell switch or a subsequent LTM cell switch of a UE; and storing the first UHI or updating previously stored UHI based on the first UHI.

Some implementations of the present disclosure provide a user equipment (UE) for wireless communication. 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: collect first mobility history information (MHI) regarding a L1/L2-Triggered Mobility (LTM) cell switch or a subsequent LTM cell switch; and store the first MHI or update previously stored MHI based on the first MHI.

In some implementations of the UE described herein, the first MHI is collected: upon receiving a lower layer message; upon a successful completion of an LTM cell switch execution; or upon transmitting a radio resource control (RRC) reconfiguration complete message after successfully accessing to a target cell.

In some implementations of the UE described herein, the at least one processor is configured to cause the UE to detect whether a ping-pong issue associated with the LTM cell switch or the subsequent LTM cell switch occurs.

In some implementations of the UE described herein, if the ping-pong issue occurs, the at least one processor is configured to cause the UE to transmit information indicating the ping-pong issue to a centralized unit (CU) or a first distributed unit (DU) of a base station (BS) , and wherein the first DU is: a source DU of the BS; a candidate DU of the BS; a target DU of the BS; a serving DU of the BS; a DU of the BS where the ping-pong issue occurs; or a combination thereof.

In some implementations of the UE described herein, the information indicating the ping-pong issue is included in: a radio link failure (RLF) report; a successful handover report (SHR) ; a successful primary secondary cell (PSCell) addition or change report (SPR) ; a secondary cell group (SCG) failure information message; or a combination thereof.

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: collect first mobility history information (MHI) regarding a L1/L2-Triggered Mobility (LTM) cell switch or a subsequent LTM cell switch; and store the first MHI or update previously stored MHI based on the first MHI.

Some implementations of the present disclosure provide a method performed by a user equipment (UE) for wireless communication. The method includes: collecting first mobility history information (MHI) regarding a L1/L2-Triggered Mobility (LTM) cell switch or a subsequent LTM cell switch; and storing the first MHI or updating previously stored MHI based on the first MHI.

BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

Figure 5 illustrates a flowchart of a method related to UE history information (UHI) in accordance with some aspects of the present disclosure.

Figure 6 illustrates a flowchart of a method related to mobility history information (MHI) in accordance with some aspects of the present disclosure.

DETAILED DESCRIPTION

The detailed description of the appended drawings is intended as a description of the preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure may be practiced. It should be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present disclosure.

Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architectures and new service scenarios, such as the 3rd generation partnership project (3GPP) 5G (NR) , 3GPP long-term evolution (LTE) Release 8, and so on. It is contemplated that along with the developments of network architectures and new service scenarios, all embodiments in the present disclosure are also applicable to similar technical problems; and moreover, the terminologies recited in the present disclosure may change, which should not affect the principles of the present disclosure.

In 3GPP, LTM was approved to change a serving cell via a lower layer message, e.g. L1/L2 signalling, in order to reduce the latency, overhead and interruption time. LTM is a cell switch procedure that the network triggers via a MAC CE based on layer-1 (L1) measurements. In 3GPP, LTM was approved to change a serving cell via L1/L2 signalling, in order to reduce the latency, overhead and interruption time. 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 LTM/mobility: a UE moves between different cells within a DU.

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

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

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 lower layer message, e.g. a cell switch command signaled via a medium access control (MAC) control element (CE) , e.g. an LTM cell switch command MAC CE. The cell switch command indicates a target cell for LTM e.g. 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.

When configured by the network, it is possible to activate transmission configuration indication (TCI) states of one or multiple cells that are different from the current serving cell. For instance, the TCI states of the LTM candidate cells can be activated in advance before any of those cells become the serving cell. This allows the UE to be DL synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when cell switch is triggered.

When configured by the network, it is possible to initiate an uplink (UL) TA acquisition (called early TA) procedure of one or multiple cells that are different from the current serving cells. If the cell has the same N_TA as the current serving cells or N_TA=0, early TA acquisition procedure is not required. The network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition procedure is triggered by a physical downlink control channel (PDCCH) order or realized through a UE-based TA measurement as configured by RRC. In the former case, the gNB/gNB-DU to which the candidate cell belongs calculates the TA value and sends it to the gNB/gNB-DU to which the serving cell belongs via gNB-CU. The serving cell sends the TA value in the LTM cell switch command MAC CE when triggering LTM cell switch. In the latter case, the UE performs TA measurement for the candidate cells after being configured by RRC but the exact time the UE performs TA measurement is up to UE implementation. The UE applies the TA value measured by itself and performs RACH-less LTM upon receiving the cell switch command. The network may also send a TA value in the LTM cell switch command MAC CE without early TA acquisition.

Depending on the availability of a valid TA value, the UE performs either a RACH-less LTM or RACH-based LTM cell switch. If the valid TA value is provided in the cell switch command, the UE applies the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no valid TA value is provided in the cell switch command, the UE applies the valid TA value by itself if available. Meanwhile, the UE performs RACH-less LTM cell switch upon receiving the cell switch command. If no valid TA value is available, the UE performs RACH-based LTM cell switch.

Regardless of whether the UE is configured for UE-based TA measurement for a certain candidate cell, it will still follow the PDCCH order, which includes requesting a random access procedure towards the candidate cells. This also applies to the candidate cells for which the UE is capable of deriving TA values by itself. Additionally, regardless of whether the UE has already performed a random access procedure towards the candidate cells, it will still follow the UE-based measurement configuration if configured by the network.

For RACH-less LTM, the UE accesses the target cell using either a configured grant or a dynamic grant. The configured grant is provided in the LTM candidate configuration, and the UE selects the configured grant occasion associated with the beam indicated in the cell switch command. Upon initiation of LTM cell switch to the target cell, the UE starts to monitor PDCCH on the target cell for dynamic scheduling. Before RACH-less LTM procedure completion, the UE shall not trigger random access procedure if it does not have a valid PUCCH resource for triggered SRs.

"LTM candidate cell" refers to a candidate cell configured to the UE for LTM. There may be multiple LTM candidate cells prepared for the UE, where the LTM candidate cells may belong to the same or different candidate DUs.

"LTM candidate configuration" refers to a configuration associated with a candidate cell, e.g. for LTM. A candidate configuration can be a complete candidate configuration or a delta configuration relatively to a reference configuration.

"LTM reference configuration" refers to a configuration provided by the network to the UE that is common, within the same cell group, to a group of configured non-complete candidate configurations.

"L1/L2 Triggered Mobility" refers to a cell switch procedure that the network triggers via MAC CE based on L1 measurements.

"RACH-less LTM" refers to an LTM cell switch procedure where UE skips the random access procedure.

The following principles may apply to LTM:

- Security keys are maintained upon an LTM cell switch;

- Subsequent LTM is supported. "Subsequent LTM" refers to an LTM cell switch procedures between candidate cells without RRC reconfiguration by the network in between. In some cases, subsequent LTM may be supported. Subsequent LTM means subsequent LTM cell switch procedures between LTM candidate cells where a UE does not need to be reconfigured by the network in between.

LTM supports both intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. LTM supports both intra-frequency and inter-frequency mobility, including mobility to inter-frequency cell that is not a current serving cell. LTM is supported only for licensed spectrum. The following scenarios are supported:

- PCell change in non-CA scenario and non-DC scenario;

- PCell and SCell (s) change in CA scenario;

- Dual connectivity scenario: including PCell and MCG SCell (s) change and intra-SN PSCell and SCG SCell (s) change without MN involvement. LTM for simultaneous PCell and PSCell change is not supported.

While the UE has stored LTM candidate configurations, the UE can also execute any layer-3 (L3) handover except for dual active protocol stack (DAPS) handover.

In general, one of the functions of Mobility Robustness Optimization (MRO) is to detect connection failures that occur due to Too Early or Too Late Handovers, or Handover to Wrong Cell. The general procedure is that after an RLF or handover (HO) failure happen, a UE may access a new cell by re-establishment or connection setup. Once the UE enters the connected state, the UE transmits an RLF report and a RACH report to the serving cell. The serving cell will transmit Failure Indication including the RLF report to the last serving cell. Finally, the information is used to optimize the mobility. One of the functions of MRO is to detect connection failures that occur due to Too Early or Too Late Handovers, or Handover to Wrong Cell.

Currently, for analysis of connection failures, a UE may make an RLF Report available to the network. The UE stores the latest RLF Report, including both LTE and NR RLF report until the RLF report is fetched by the network or for 48 hours after the connection failure is detected. For example, the UE only indicates the RLF report availability and only provides the RLF report to the network if the current RPLMN is a PLMN that was present in the UE's EPLMN List or was the RPLMN at the time the connection failure was detected. In case an RLF happens in an E-UTRA cell, the UE makes the LTE RLF Report available to NG-RAN nodes and eNB (s) , and in case RLF happens in an NR cell the UE makes the NR RLF Report available to gNB (s) . If the LTE RLF Report is reported to a NG-RAN node, and the last serving node is an E-UTRAN node, the NG-RAN node may transfer it to the E-UTRAN node by triggering the Uplink RAN configuration transfer procedure over NG and the E-UTRAN node can take this into account as defined in 3GPP TS 36.300.

In 3GPP Rel-17, Successful Handover Report (SHR) is introduced for MRO of a PCell change procedure. In particular, the MRO function in NR needs to be enhanced to provide a more robust mobility via reporting failure events observed during successful handovers. A solution to this problem is to configure the UE to compile a report associated with a successful handover comprising a set of measurements collected during the handover phase, i.e. measurement at the handover trigger, measurement at the end of handover execution or measurement after handover execution. The UE could be configured with triggering conditions to compile a SHR, hence the report would be triggered only if the conditions are met. This limits UE reporting to relevant cases, such as underlying issues detected by RLM, or BFD detected upon a successful handover event.

Successful PCell change related information may be included in a SHR. The availability of a SHR may be indicated by the Handover Complete message (e.g. an RRC Reconfiguration Complete message) transmitted from a UE to target NG-RAN node over RRC. The target NG-RAN node may fetch information of a successful handover report via UE Information Request/Response mechanism. In addition, the target NG-RAN node could then forward the SHR to the source NR-RAN node to indicate failures experienced during a successful handover event.

Upon reception of a SHR, the receiving node is able to analyze whether its mobility configuration needs adjustment. Such adjustments may result in changes of mobility configurations, such as changes of RLM configurations or changes of mobility thresholds between the source and the target. In addition, target NG-RAN node, in the executed handover, may further optimize the dedicated RACH resources based on the measurements reported upon successful handovers.

The objective of successful PSCell addition or change Report (SPR) is to detect sub-optimal successful PSCell change/CPC or successful PSCell addition/CPA. For analysis of such sub-optimal successful PSCell change/CPC and successful PSCell addition/CPA, the UE may collect SPR based on the triggers configured by the network, if received, and makes the SPR available to the network as specified in 3GPP standard document TS 38.331. For PSCell addition/CPA and PSCell change/CPC (MN or SN initiated) , the target SN always decides the T304 trigger for SPR and performs root cause analysis. For SN-initiated PSCell change/CPC, the source SN decides the T310/T312 triggers for SPR and is responsible for SPR related optimizations e.g. to optimize PSCell change/CPC configuration or associated mobility thresholds or adjust T310/T312 timer values. For MN-initiated PSCell change/CPC, the MN decides the T310/T312 triggers for SPR. MN may optimize PSCell change/CPC configuration or associated mobility thresholds or both. Source SN may optimize lower layer issues e.g. adjust T310/T312 timer values. The SPR can be fetched from the UE by the MN only while the UE is still connected to the MN, or by a node different from the MN that sent the SPR configuration to the UE if the UE is not connected to the MN anymore. In case the SPR is retrieved in a node different from the MN that sent the SPR configuration to the UE, the SPR is first forwarded to that MN, which then forwards it to the respective SN (s) which should perform the SPR optimization.

In some cases, a UE may report UE history information (e.g. mobility history information (MHI) ) when connecting to a cell of the NG-RAN node, consisting of PCell mobility history information and optionally PSCell mobility history information, as specified in TS 38.331. When information needs to be discarded because the list is full, such information will be discarded in order of its position in the list, starting with the oldest cell record. If the list is full, and the UE history information from the UE is available, the UE history information from the UE should also be discarded. In some cases, a NG-RAN node collects and stores UE History Information (UHI) as long as a UE stays in one of its cells.

Currently, details for MRO for LTM have not been specifically discussed yet in a wireless communication system or the like. For example, the following issues need to be solved: if a beam of a target cell indicated in an LTM cell switch command is improper or sub-optimal, how to enable the network to detect a connection failure or a near-failure success which is caused due to a wrong beam or a sub-optimal beam of the target cell selected in a source DU; considering an LTM procedure is a mechanism mainly introduced for interruption time reduction, what is an LTM specific trigger condition for a successful report (e.g. SHR and/or SPR) ; and how to collect UE history information (UHI) at a network side for an LTM procedure; and how to collect mobility history information (MHI) at a UE side for an LTM procedure.

Embodiments of the present disclosure aim to resolve the abovementioned issues. For example, some embodiments of the present disclosure consider MRO analysis for an LTM cell switch to an improper beam. In particular, in an embodiment, a UE may store and report information of a beam (where a beam failure recovery is performed) in an RLF report. In an embodiment, a CU may analyze and determine whether it is a wrong beam selection for a target cell at a source DU, and the CU may send an indication concerning that it is a wrong beam selection at the source DU to the source DU. In another embodiment, a CU may perform an initial analysis, and decide to send an RLF report to a source DU for a root cause analysis, and then, the source DU analyses and determines whether it is a wrong beam selection at the source DU.

Some other embodiments of the present disclosure consider MRO analysis for LTM cell switch to a sub-optimal beam. In particular, a beam failure recovery during an LTM cell switch procedure may be configured as a trigger condition for a successful report (e.g. SHR and/or SPR) to a UE, e.g. which is configured to the UE by default or configured to the UE by a CU or a source DU. The UE may store and report information of a beam (where beam failure recovery is performed) in a successful report (e.g. SHR and/or SPR) .

Some embodiments of the present disclosure introduce LTM specific trigger conditions for a successful report (e.g. SHR and/or SPR) . For instance, the successful report is generated when at least one of the following trigger conditions is fulfilled: an early TA acquisition procedure is not configured or is not triggered by a PDCCH order; a UE-based TA measurement is not configured; a TA value acquired in an early TA acquisition is invalid; a TA value measured by a UE is not valid; a RACH-less LTM cell switch is not successful; time duration for accessing to a target cell (e.g. time between receiving an LTM cell switch command (e.g. an LTM cell switch command MAC CE) and successfully accessing to the target cell is longer than a threshold, or time duration between receiving an RRC reconfiguration message for LTM and successfully accessing to the target cell) is longer than a threshold.

Some embodiments of the present disclosure consider methods of history information for an LTM cell switch procedure and an LTM ping-pong issue detection. In particular, in an embodiment, a DU collects UHI or updates its stored UHI. The DU may send the latest UHI to its CU upon the UHI is collected or updated. Then, the CU may send the UHI to other DU (s) timely. The DU may detect an LTM ping-pong issue, and send the identified LTM ping-pong issue to the CU. In another embodiment, a CU collects UHI or updates its stored UHI. The CU may detect an LTM ping-pong issue, and send the identified LTM ping-pong issue to a DU. In an additional embodiment, a UE collects MHI or updates its stored MHI. The UE may detect an LTM ping-pong issue, and send the identified LTM ping-pong issue to a DU or a CU.

In this disclosure, cell information includes PLMN-Identity, Cell Identity and TrackingAreaCode of the cell, or includes configuration identifier (ID) of the cell, or includes PCI and carrier frequency information (e.g. ARFCN) . Information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a synchronization signal block (SSB) index, or a channel state information reference signal (CSI-RS) index. The "successful cell change" refers to the UE's state, namely a successful completion of a random access (RA) procedure.

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 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 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 which may be configured to support: a means for storing and reporting information related to a beam where a beam failure recovery is performed during an LTM cell switch procedure or a subsequent LTM cell switch procedure. The information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a SSB index, or a CSI-RS index.

For example, the processor 202 may support wireless communication at the UE 200 in accordance with examples as disclosed with respect to Figure 6. The UE 200 may be configured to support: a means for collecting MHI regarding an LTM cell switch or a subsequent LTM cell switch; and a means for storing the MHI or updating previously stored MHI based on the MHI.

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 asor 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 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 a means for performing operations of a unit of a BS. The processor 300 may be configured to or operable to support: a means for obtaining information regarding whether an LTM cell switch to wrong or sub-optimal beam occurs.

In some implementations, the processor 300 may be configured to support a means for performing operations of a UE. The processor 300 may be configured to or operable to support: a means for storing and a means for reporting information related to a beam where a beam failure recovery is performed during an LTM cell switch procedure or a subsequent LTM cell switch procedure. The information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a SSB index, or a CSI-RS index.

In some implementations, the processor 300 may be configured to support a means for performing operations of a unit of a BS s described with respect to Figure 5. The processor 300 may be configured to or operable to support: a means for obtaining UHI regarding an LTM cell switch or a subsequent LTM cell switch of a UE; and a means for storing the UHI or updating previously stored UHI based on the UHI.

In some implementations, the processor 300 may be configured to support a means for performing operations of a UE as described with respect to Figure 6. The processor 300 may be configured to or operable to support: a means for collecting MHI regarding an LTM cell switch or a subsequent LTM cell switch; and a means for storing the MHI or updating previously stored MHI based on the MHI.

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 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.

In some implementations, the NE 400 may be a unit of a BS and may be configured to or operable to support: a means for obtaining information regarding whether an LTM cell switch to wrong or sub-optimal beam occurs.

In some implementations, the NE 400 may be a unit of a BS and may be configured to or operable to support: a means for obtaining UHI regarding an LTM cell switch or a subsequent LTM cell switch of a UE; and a means for storing the UHI or update previously stored UHI based on the UHI.

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 asor 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.

In accordance with some aspects of the present disclosure, a method related to an LTM cell switch procedure may be implemented by a unit of a BS as described herein. In some implementations, aspects of the operations of the unit of the BS may be performed by NE 400 as described with reference to Figure 4. It should be noted that the method implemented by the unit of the BS herein 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. Specific examples are described in Embodiments 1 and 2 as follows.

In particular, the method may include obtaining, by a unit of a BS, information regarding whether "an LTM cell switch to wrong or sub-optimal beam" occurs.

In some implementations, to obtain the information, the unit may receive information (denoted as information #1) related to a connection failure, e.g. the unit receives a radio link failure (RLF) report including information #1. The connection failure occurs during an LTM cell switch execution or shortly after a successful completion of the LTM cell switch execution. Information #1 may be named as "failure information" or the like. In some implementations, information #1 includes information related to a beam where a beam failure recovery is performed. The information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a SSB index, or a CSI-RS index.

In some implementations of the method, the unit is a CU of the BS, and the CU may perform at least one of the following operations:

(1) Transmitting information #1 to a DU of the BS. For example, the CU performs an initial analysis for information #1 and decide to transmit information #1 to a DU of the BS.

- In some implementations, the CU may transmit information #1 to a source DU of the BS, e.g. to enable the source DU to perform a root cause analysis. In some embodiments, the CU may receive at least one of the following from the source DU:

a) information indicating that the LTM cell switch to wrong or sub-optimal beam occurs; and/or

b) failure type information concerning a wrong or sub-optimal beam selection at the source DU.

(2) Determining whether "an LTM cell switch to wrong or sub-optimal beam" occurs. For example, the CU performs a root cause analysis for information #1 and determines whether "an LTM cell switch to wrong or sub-optimal beam" occurs based on information #1.

- In some implementations, the CU determines that the LTM cell switch to wrong or sub-optimal beam occurs, for example, in case that the connection failure occurs during the LTM cell switch execution, or the connection failure (e.g. the RLF) occurs shortly after the successful completion of the LTM cell switch execution; and a UE attempts to recover or re-establish or reconnect a radio link connection in a cell where the connection failure occurs, wherein "a beam where the connection failure occurred" and "a beam where the UE successfully recover or re-establish or reconnect a radio link connection" are different beams but belong to a same cell, the CU determines that the LTM cell switch to wrong or sub-optimal beam occurs.

- In some embodiments, if the LTM cell switch to wrong or sub-optimal beam occurs, the CU may transmit at least one of the following to a source DU of the BS:

In some implementations of the method, the unit is a source DU of the BS, and the source DU may perform at least one of the following operations:

(1) Receiving at least one of: information #1 related to the connection failure, information indicating that an LTM cell switch to wrong or sub-optimal beam occurs, and failure type information concerning a wrong or sub-optimal beam selection at the source DU.

(2) Determining whether the LTM cell switch to wrong or sub-optimal beam occurs. In some embodiments, the source DU may determine that the LTM cell switch to wrong or sub-optimal beam occurs in case that: the connection failure occurs during the LTM cell switch execution, or the connection failure occurs shortly after the successful completion of the LTM cell switch execution; and a UE attempts to recover or re-establish or reconnect a radio link connection in a cell where the connection failure occurs, wherein "a beam where the connection failure occurred" and "a beam where the UE successfully recover or re-establish or reconnect a radio link connection" are different beams but belong to a same cell.

In some implementations, in response to receiving information #1, the source DU may perform a root cause analysis or determine whether the LTM cell switch to wrong or sub-optimal beam occurs.

In some embodiments, in response to receiving information #1, if the LTM cell switch to wrong or sub-optimal beam occurs, the source DU may transmit, to a CU of the BS, information indicating that the LTM cell switch to wrong or sub-optimal beam occurs, and/or failure type information concerning a wrong or sub-optimal beam selection at the source DU.

In some embodiments, if the LTM cell switch to wrong or sub-optimal beam occurs, the source DU may perform MRO optimization e.g. modify beam configuration information of a target cell in a lower layer message. For example, the lower layer message is an LTM cell switch command, e.g. an LTM cell switch command MAC CE.

In some implementations of the method, the unit may obtain configuration information of at least one trigger condition for a UE to store or report successful LTM related information. The successful LTM related information is related to a near-failure successful LTM cell switch or a near-failure successful subsequent LTM cell switch. For example, the successful LTM related information may be reported in a SHR and/or a SPR. Then, the unit may transmit the configuration information, e.g. to the UE directly or to the UE indirectly. In some implementations, the unit may transmit the configuration information to the UE via: (1) an RRC message, e.g. an RRC reconfiguration message; and/or (2) a lower layer message, e.g. an LTM cell switch command MAC CE. For example, the unit is a CU of the BS, and the CU transmits the configuration information to the UE directly or indirectly via a source DU of the BS. For example, the unit is a source DU of the BS, and the source DU transmits the configuration information to the UE directly or indirectly via a CU of the BS.

In some implementations, the configuration information of the at least one trigger condition includes:

(1) a condition concerning that an early TA acquisition procedure is not configured to the UE;

(2) a condition concerning that the early TA acquisition procedure is not triggered by a PDCCH order;

(3) a condition concerning that a UE-based TA measurement is not configured to the UE;

(4) a condition concerning that a TA value acquired in the early TA acquisition procedure is not valid;

(5) a condition concerning that a TA value provided in a lower layer message (e.g. an LTM cell switch command MAC CE) is not valid;

(6) a condition concerning that no valid TA value is provided in the lower layer message;

(7) a condition concerning that a TA value measured by the UE is not valid;

(8) a condition concerning that no valid TA value is available via the UE-based TA measurement;

(9) a condition concerning that a RACH-less LTM cell switch is not performed;

(10) a condition concerning that the RACH-less LTM cell switch is not successful;

(11) a threshold related with accessing to a target cell;

(12) a condition concerning that a beam failure recovery is performed during an LTM cell switch procedure or a subsequent LTM cell switch procedure;

(13) a timer T310 related threshold related with a ratio between a value of elapsed running time of a timer T310 and a configured length value of the timer T310;

(14) a timer T312 related threshold related with a ratio between a value of elapsed running time of a timer T312 and a configured length value of the timer T312; and/or

(15) a timer T304 related threshold related with a ratio between a value of elapsed running time of a timer T304 and a configured length value of the timer T304.

In some implementations, the successful LTM related information includes the information related to a beam where a beam failure recovery is performed, in case that:

(1) a beam failure recovery is performed during the LTM cell switch or the subsequent LTM cell switch;

(2) a ratio between a value of elapsed running time of a timer T310 and a configured length value of the timer T310 is greater than at least one timer T310 related threshold;

(3) a ratio between a value of elapsed running time of a timer T312 and a configured length value of the timer T312 is greater than at least one timer T312 related threshold; and/or

(4) a ratio between a value of elapsed running time of a timer T304 and a configured length value of the timer T304 is greater than at least one timer T304 related threshold.

In some implementations of the method, the unit may receive successful LTM related information, which includes at least one of the following:

(1) information related to a beam where a beam failure recovery is performed, the information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a SSB index, or a CSI-RS index;

(2) a cause value for storing or reporting the successful LTM related information;

(3) time duration between receiving a lower layer message (e.g. an LTM cell switch command MAC CE) and successfully accessing to a target cell;

(4) time duration between receiving an RRC reconfiguration message and successfully accessing to the target cell; or

(5) a time point for successfully accessing to the target cell.

In some implementations of the method, the unit is a CU of the BS. To obtain the configuration information, in some embodiments, the CU may generate the configuration information, and in some other embodiments, the CU may receive the configuration information (e.g. which may be generated by a source DU and/or a candidate DU of the BS) from at least one DU. In some implementations, the CU may transmit the configuration information to the UE, for instance, the configuration information is transmitted to the UE via:

(1) an RRC message, e.g. an RRC reconfiguration message; and/or

(2) a lower layer message, e.g. an LTM cell switch command MAC CE.

In some implementations of the method, the unit is a source DU of the BS. To obtain the configuration information, in some embodiments, the source DU may receive the configuration information (e.g. which may be generated by the CU and/or a candidate DU of the BS) from a CU of the BS. In some other embodiments, the source DU may generate the configuration information.

In some implementations, the source DU may transmit the configuration information to the CU, or transmit the configuration information to the UE. For instance, the configuration information transmitted to the UE is included in:

(1) an RRC message, e.g. an RRC reconfiguration message; and/or

(2) a lower layer message, e.g. an LTM cell switch command MAC CE.

In accordance with some aspects of the present disclosure, a method related to an LTM cell switch procedure may be implemented by a UE as described herein. In some implementations, aspects of the operations of the UE may be performed by UE 200 as described with reference to Figure 2. It should be noted that the method implemented by the UE herein 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. Specific examples are described in Embodiments 1 and 2 as follows.

In particular, the method may include storing and reporting, by a UE, information related to a beam where a beam failure recovery is performed during an LTM cell switch procedure or a subsequent LTM cell switch procedure. The information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a SSB index, or a CSI-RS index.

In some implementations of the method, the UE may store and report the information related to the beam in an RLF report.

In some implementations of the method, the UE may obtain a configuration (denoted as configuration #1) of at least one trigger condition to store or report successful LTM related information. The successful LTM related information is related to a near-failure successful LTM cell switch or a near-failure successful subsequent LTM cell switch.

In some embodiments, the UE may obtain configuration #1 by pre-configuration. In some other embodiments, the UE may receive configuration #1 from a NE. For instance, configuration #1 is received from the NE via an RRC message and/or a lower layer message. For example, the lower layer message is an LTM cell switch command, e.g. an LTM cell switch command MAC CE.

In some embodiments, configuration #1 is associated with at least one trigger condition for the UE to store or report the successful LTM related information. For example, the successful LTM related information may be stored or reported in a SHR and/or a SPR. For instance, configuration #1 includes:

(7) a condition concerning that a TA value measured by the UE is not valid;

(9) a condition concerning that a RACH-less LTM cell switch is not performed;

(11) a threshold related with accessing to a target cell, e.g. a threshold related with time duration between receiving a lower layer message (e.g. an LTM cell switch command MAC CE) or an RRC reconfiguration message and successfully accessing to the target cell;

(14) a timer T312 related threshold related with a ratio between a value of elapsed running time of a timer T312 and a configured length value of the timer T31; and/or

In some implementations of the method, the successful LTM related information includes:

(1) the information related to the beam where the beam failure recovery is performed;

(4) time duration between receiving an RRC reconfiguration message and successfully accessing to the target cell; and/or

(5) a time point for successfully accessing to the target cell.

Figure 5 illustrates a flowchart of a method related to UE history information (UHI) in accordance with some aspects of the present disclosure. The operations of the method may be implemented by a unit of a BS as described herein. In some implementations, aspects of operations 502 and 504 may be performed by NE 400 as described with reference to Figure 4. Each of operations 502 and 504 may be performed in accordance with examples as described herein. Specific examples are described in Embodiment 3 as follows.

At operation 502, a unit of a BS may obtain UE history information (UHI) regarding an LTM cell switch or a subsequent LTM cell switch of a UE. At operation 504, the unit of the BS may store the UHI or update previously stored UHI based on the UHI.

In some implementations of the method, the LTM cell switch or the subsequent LTM cell switch is one of:

(1) an intra-DU LTM cell switch or an intra-DU subsequent LTM cell switch; or

(2) an inter-DU LTM cell switch or an inter-DU subsequent LTM cell switch.

In some implementations of the method, the unit is a CU of the BS. In some other embodiments, to obtain the UHI, the CU may collect the UHI in at least one of the following cases, e.g. in an intra-gNB-DU LTM cell switch or an inter-gNB-DU LTM cell switch:

(1) upon receiving a DU-CU cell switch notification message;

(2) upon receiving an access success message; and/or

(3) upon receiving a UL RRC message transfer message.

In some other embodiments, to obtain the UHI, the CU may perform at least one of the following operations, e.g. in an intra-gNB-DU LTM cell switch:

(1) calculate that time duration of the UE staying in a cell (denoted as cell #1) equals to time duration between receiving an access success message for cell #1 and receiving a DU-CU cell switch notification message for a next target cell, wherein the next target cell is a cell where the UE stayed after cell #1;

(2) calculate that the time duration of the UE staying in cell #1 equals to time duration between receiving a DU-CU cell switch notification message for cell #1 and receiving the DU-CU cell switch notification message for the next target cell;

(3) calculate that the time duration of the UE staying in cell #1 equals to time duration between receiving the access success message for cell #1 and receiving a access success message for the next target cell; or

(4) calculate that the time duration of the UE staying in cell #1 equals to time duration between receiving a UL RRC message transfer message for cell #1 and receiving a UL RRC message transfer message for the next target cell.

In some other embodiments, to obtain the UHI, the CU may perform at least one of the following operations, e.g. in an inter-gNB-DU LTM cell switch:

(1) calculate that time duration of the UE staying in a cell (denoted as cell #2) equals to time duration between receiving an access success message for cell #2 and receiving a DU-CU cell switch notification message for a next target cell, wherein the next target cell is a cell where the UE stayed after cell #2;

(2) calculate that the time duration of the UE staying in cell #2 equals to time duration between receiving a UL RRC message transfer message for cell #2 and receiving the DU-CU cell switch notification message for the next target cell;

(3) calculate that the time duration of the UE staying in cell #2 equals to time duration between receiving a DU-CU cell switch notification message for cell #2 and receiving the DU-CU cell switch notification message for the next target cell;

(4) calculate that the time duration of the UE staying in cell #2 equals to time duration between receiving the access success message for cell #2and receiving an access success message for the next target cell; or

(5) calculate that the time duration of the UE staying in cell #2 equals to time between receiving a UL RRC message transfer message for cell #2 and receiving a UL RRC message transfer message for the next target cell.

In some additional embodiments, to obtain the UHI, the CU may receive the UHI (which is collected by a DU of the BS) from the DU of the BS, or receive the UHI (which is collected by the UE) from the UE.

In some implementations of the method, the unit is a CU of the BS, and the CU may transmit the UHI to a DU of the BS. The DU may be: a source DU of the BS; a candidate DU of the BS;a target DU of the BS; a serving DU of the BS; and/or a DU of the BS where the ping-pong issue occurs.

In some implementations of the method, the unit is a DU of the BS. In some embodiments, to obtain the UHI, the DU may collect the UHI in at least one of the following cases, e.g. in an intra-gNB-DU LTM cell switch or an inter-gNB-DU LTM cell switch:

(1) upon transmitting a lower layer message (e.g. an LTM cell switch command MAC CE) ;

(2) upon transmitting a DU-CU cell switch notification message;

(3) upon transmitting an access success message;

(4) upon receiving an RRC reconfiguration complete message after successfully accessing to a target cell; or

(5) upon transmitting a UL RRC message transfer message.

In some other embodiments, to obtain the UHI, the DU may perform at least one of the following operations, e.g. in an intra-gNB-DU LTM cell switch:

(1) calculate that time duration of the UE staying in a cell (denoted as cell #3) equals to time duration between transmitting an access success message to a CU of the BS for cell #3 and transmitting a lower layer message (e.g. an LTM cell switch command MAC CE) to the UE for a next target cell, wherein the next target cell is a cell where the UE stayed after cell #3;

(2) calculate that the time duration of the UE staying in cell #3 equals to time duration between transmitting the lower layer message to the UE for cell #3 and transmitting the lower layer message to the UE for the next target cell;

(3) calculate that the time duration of the UE staying in cell #3 equals to time duration between transmitting a DU-CU cell switch notification message to the CU for cell #3 and transmitting a DU-CU cell switch notification message to the CU for the next target cell;

(4) calculate that the time duration of the UE staying in cell #3 equals to time duration between transmitting an access success message to the CU for cell #3 and transmitting an access success message to the CU for the next target cell; or

(5) calculate that the time duration of the UE staying in cell #3 equals to time duration between transmitting a UL RRC message transfer message to the CU for cell #3 and transmitting a UL RRC message transfer message to the CU for the next target cell.

In some other embodiments, to obtain the UHI, the DU may perform at least one of the following operations, e.g. in an inter-gNB-DU LTM cell switch:

(1) calculate that time duration of the UE staying in a cell (denoted as cell #4) equals to time duration between transmitting an access success message to a CU of the BS for cell #4 and transmitting a lower layer message (e.g. an LTM cell switch command MAC CE) to the UE for a next target cell, wherein the next target cell is a cell where the UE stayed after cell #4;

(2) calculate that the time duration of the UE staying in cell #4 equals to time duration between transmitting a UL RRC message transfer message to the CU for cell #4 and transmitting the lower layer message to the UE for the next target cell; or

(3) calculate that the time duration of the UE staying in cell #4 equals to time duration between receiving an RRC reconfiguration complete message after successfully accessing to cell #4 and transmitting the lower layer message to the UE for the next target cell.

In some additional embodiments, to obtain the UHI, the DU may receive the UHI (which is collected by the CU) from a CU of the BS, or receive the UHI (which is collected by the UE) from the UE.

In some implementations of the method, the unit is a DU of the BS, and the DU may transmit the UHI to a CU of the BS:

(1) upon collecting the UHI;

(2) upon updating the first UHI; or

(3) upon the UE switches to another cell or another DU.

In some implementations of the method, the unit may detect whether a ping-pong issue associated with the LTM cell switch or the subsequent LTM cell switch occurs. In some embodiments, the unit is a CU. If the ping-pong issue occurs, the CU may transmit information indicating the ping-pong issue to: a source DU of the BS; a candidate DU of the BS; a target DU of the BS; a serving DU of the BS; and/or a DU of the BS where the ping-pong issue occurs. In some other embodiments, the unit is a DU of the BS. If the ping-pong issue occurs, the DU may transmit information indicating the ping-pong issue to a CU of the BS.

In some implementations of the method, the unit may receive information indicating a ping-pong issue associated with the LTM cell switch or the subsequent LTM cell switch, e.g. from a DU of the BS or from a UE.

Figure 6 illustrates a flowchart of a method related to mobility history information (MHI) 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, aspects of operations 502 and 504 may be performed by UE 200 as described with reference to Figure 2. Each of operations 502 and 504 may be performed in accordance with examples as described herein. Specific examples are described in Embodiment 3 as follows.

At operation 602, the UE may collect MHI regarding an LTM cell switch or a subsequent LTM cell switch. At operation 604, the UE may store the MHI or update previously stored MHI based on the MHI.

In some implementations of the method, the MHI is collected by the UE:

(1) upon receiving a lower layer message (e.g. an LTM cell switch command MAC CE) ;

(2) upon a successful completion of an LTM cell switch execution; or

(3) upon transmitting an RRC reconfiguration complete message after successfully accessing to a target cell.

In some implementations of the method, the UE may detect whether a ping-pong issue associated with the LTM cell switch or the subsequent LTM cell switch occurs. In some embodiments, if the ping-pong issue occurs, the UE may transmit information indicating the ping-pong issue to a CU or to a DU of a BS. For example, the DU is a source DU of the BS, a candidate DU of the BS, a target DU of the BS, a serving DU of the BS, and/or a DU of the BS where the ping-pong issue occurs.

In an embodiment, the information indicating the ping-pong issue is included in: (1) an RLF report; (2) a SHR; (3) a SPR; and/or (4) a SCG failure information message.

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.

The following text describes specific embodiments of the flowcharts as shown and illustrated above, i.e. Embodiment 1, Embodiment 2 and Embodiment 3 as below.

Embodiment 1 (an LTM cell switch to a wrong beam or a sub-optimal beam)

Embodiment 1-1 (for a connection failure case)

In MCG LTM, there may be a case that a connection failure (e.g. an RLF) occurs shortly after a successful LTM cell switch from a source cell to a target cell, or a failure occurs during an LTM cell switch execution or the LTM cell switch execution fails; a UE attempts to recover or re-establish or reconnect the radio link connection in a cell where the connection failure occurs; while the beam where the connection failure happened (e.g. where the LTM cell switch execution failed or where the RLF occurred) and the beam where the UE succeeded to recover or re-establish or reconnect the radio link connection are of the same cell. This case can be treated or defined as "LTM cell switch to wrong beam" or the like.

A detection mechanism for the case of "LTM cell switch to wrong beam" may be that or a "LTM cell switch to wrong beam" may be defined that: there is a recent LTM cell switch for a UE prior to the connection failure, e.g. the length of the UE reported timer is less than a configured threshold (e.g. Tstore_UE_cntxt) ; the first re-establishment attempt cell, or the cell UE attempts to re-connect or recover, or the cell UE attempts an LTM failure recovery is either the cell that served the UE at the last initialization of the LTM cell switch or the cell that served the UE where the RLF happened or the cell that the LTM execution was initialized toward; and the beam where the connection failure happened (e.g. the beam where the LTM cell switch execution failed or the beam where the RLF occurred or the beam where the LTM execution was initialized toward) and the beam where the UE succeeded to recover or re-establish or reconnect the radio link connection are of the same cell.

For the case "LTM cell switch to wrong beam" , a UE may store and report information of beam where the RLF happened or where the LTM cell switch execution failed, and information of beam where the UE succeeded to recover or re-establish or reconnect the radio link connection in an RLF report. Furthermore, if the beam failure recovery is performed during the LTM cell switch execution or shortly after successful completing the LTM cell switch execution, the UE may store and report information of the beam where the beam failure recovery is performed in the RLF report. The information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a SSB index, or a CSI-RS index.

In Embodiment 1-1, to enable a network side (e.g. NE) to detect that the connection failure is caused due to a wrong beam of a target cell selected in a source DU, there may be following four options according to different embodiments, i.e. Option #1, Option #2, Option #3 and Option #4.

Option #1: a CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for an LTM procedure for a UE) analyses and determines that it is a wrong beam selection at a source DU, e.g. based on the received RLF report.

- In an example, the CU may send "an indication concerning that it is a wrong beam selection at the source DU" to the source DU, e.g. via a new introduced F1 message or an existing F1 message (e.g. Access and Mobility Indication message or other) .

- In another example, the CU may indicate to the source DU that it is "LTM cell switch to wrong beam, " e.g. via a new introduced F1 message or an existing F1 message (e.g. Access and Mobility Indication message or other) .

- In an additional example, the CU may indicate the failure type of "LTM cell switch to wrong beam" to a source DU, e.g. via a new introduced F1 message or an existing F1 message (e.g. Access and Mobility Indication message or other) .

- Then, based on an indication or a failure type received from the CU, the source DU may perform MRO optimization, e.g. to update a beam of the target cell in the LTM cell switch command (e.g. an LTM cell switch command MAC CE) .

Option #2: a CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for an LTM procedure for a UE) performs an initial analysis, and decides to send an RLF report to a source DU for a root cause analysis. The CU sends the RLF report (for example, the whole RLF report received by the CU, or only a part of the received RLF report that is relevant to the source DU) to the source DU. Then, the source DU analyses and determines whether it is a wrong beam selection at the source DU. Then, if the source DU determines that it is a wrong beam selection at the source DU, the source DU may perform MRO optimization, e.g. to update a beam of the target cell in the LTM cell switch command (e.g. an LTM cell switch command MAC CE) . Optionally, if the source DU determines that it is a wrong beam selection at the source DU, there may be following examples of Option #2 according to different embodiments:

- In an example, the source DU may send "an indication concerning that it is the wrong beam selection at the source DU" to the CU, e.g. via a new introduced F1 message or an existing F1 message.

- In another example, the source DU may indicate to the CU that it is "LTM cell switch to wrong beam, " e.g. via a new introduced F1 message or an existing F1 message.

- In an additional example, the source DU may indicate the failure type of "LTM cell switch to wrong beam" to the CU, e.g. via a new introduced F1 message or an existing F1 message.

Option #3: a CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for an LTM procedure for a UE) sends an RLF report to each relevant DU (involved DUs e.g. including a source DU, a candidate target DU or a target DU) separately for MRO analysis. Based on the received RLF report, the relevant DU performs a root cause analysis. For example, based on the received RLF report, a source DU analyses and determines whether it is a wrong beam selection at the source DU. Then, if the source DU determines that it is a wrong beam selection at the source DU, the source DU may perform MRO optimization, e.g. to update a beam of the target cell in a lower layer message (e.g. an LTM cell switch command MAC CE) . Optionally, if the source DU determines that it is a wrong beam selection at the source DU, there may be following examples of Option #3 according to different embodiments:

- In an example, the source DU may send "an indication concerning that it is a wrong beam selection at the source DU" to the CU, e.g. via a new introduced F1 message or an existing F1 message.

-In an additional example, the source DU may indicate the failure type of "LTM cell switch to wrong beam" to the CU, e.g. via a new introduced F1 message or an existing F1 message.

Option #4: a CU sends an RLF report to a target DU. Then, the target DU analyses and determines whether it is a wrong beam selection at the source DU. If the target DU determines that it is a wrong beam selection at the source DU, the target DU may perform the following operations:

- In an example, the target DU may send "an indication concerning that it is a wrong beam selection at the source DU" to the CU, e.g. via a new introduced F1 message or an existing F1 message. Then, the CU may send "the indication concerning that it is a wrong beam selection at the source DU" to the source DU, e.g. via a new introduced F1 message or an existing F1 message.

- In another example, target DU may indicate to the CU that it is "LTM cell switch to wrong beam, " e.g. via a new introduced F1 message or an existing F1 message. Then, the CU may indicate to the source DU that it is "LTM cell switch to wrong beam, " e.g. via a new introduced F1 message or an existing F1 message.

- In an additional example, the target DU may indicate the failure type of "LTM cell switch to wrong beam" to the CU, e.g. via a new introduced F1 message or an existing F1 message. Then, the CU may indicate the failure type of "LTM cell switch to wrong beam" to the source DU, e.g. via a new introduced F1 message or an existing F1 message.

Then, in Option #4, based on an indication or a failure type received from the CU, the source DU may perform MRO optimization, e.g. to update a beam of a target cell in a lower layer message (e.g. an LTM cell switch command MAC CE) .

Embodiment 1-2 (for a near-failure successful case)

In MCG LTM or SCG LTM, there may be a case that even an LTM cell switch execution is successful, a beam failure recovery is performed during the LTM cell switch execution which causes long interruption time. This case can be treated as "a near-failure successful LTM due to a sub-optimal beam of a target cell selected in a source DU, " "LTM cell switch to sub-optimal beam, " or the like.

In Embodiment 1-2, to enable a network side (e.g. a CU of a BS) to detect the near-failure successful LTM that is caused due to a sub-optimal beam of a target cell selected in a source DU, a beam failure recovery performed during an LTM cell switch may be configured as a trigger condition for a successful report (e.g. SHR and/or SPR) . For example, there may be following three options according to different embodiments, i.e. Option #A, Option #B and Option #C.

Option #A: a CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for an LTM procedure for a UE) generates "a condition that a beam failure recovery is performed during an LTM cell switch" as a trigger condition for a successful report (e.g. SHR and/or SPR) .

- In an example, this new trigger condition may be configured to the UE in an RRC Reconfiguration message, e.g. the last RRC Reconfiguration message for LTM procedure.

- In another example, this new trigger condition may be configured to the UE in a lower layer message (e.g. an LTM cell switch command MAC CE) . That is, the CU generates "a condition that a beam failure recovery is performed during an LTM cell switch" as the new trigger condition, and then, the CU sends the new trigger condition to the source DU; after that, the source DU sends the trigger condition to the UE via the LTM cell switch command.

Option #B: a source DU (e.g. which sends an LTM cell switch command to a UE) generates "a condition that a beam failure recovery is performed during an LTM cell switch" as a trigger condition for a successful report (e.g. SHR and/or SPR) .

- In an example, this new trigger condition may be configured to the UE in an RRC Reconfiguration message, e.g. the last RRC Reconfiguration message for LTM procedure. That is, a source DU generates "a condition that a beam failure recovery is performed during an LTM cell switch" as the new trigger condition, and then, the source DU sends the new trigger condition to the CU; after that, the CU sends the new trigger condition to the UE in an RRC Reconfiguration message via the source DU.

- In another example, this new trigger condition may be configured to the UE in a lower layer message (e.g. an LTM cell switch command MAC CE) . That is, the source DU generates "a condition that a beam failure recovery is performed during an LTM cell switch" as the new trigger condition, and then, the source DU sends the new trigger condition to the UE via the LTM cell switch command (e.g. an LTM cell switch command MAC CE) .

Option #C: a UE is configured with "a condition that a beam failure recovery is performed during an LTM cell switch" as a trigger condition for a successful report (e.g. SHR and/or SPR) by default.

In Embodiment 1-2, a timer T310 or T312 or T304 related trigger threshold as legacy can be configured to the UE for a successful report (e.g. SHR and/or SPR) , when the timer T310 or T312 or T304 related trigger threshold or the above new trigger condition is fulfilled, the UE may store and report successful LTM related information, for example, information of the beam where a beam failure recovery is performed may be stored and reported in the successful report (e.g. SHR and/or SPR) . The information related to the beam may be TCI state or a beam ID, for example, the beam ID may be a SSB index, or a CSI-RS index.

For example, the timer T310 or T312 or T304 related trigger threshold being fulfilled means that :

(1) a ratio between a value of elapsed running time of a timer T310 and a configured value of the timer T310 is greater than at least one timer T310 related threshold;

(2) a ratio between a value of elapsed running time of a timer T312 and a configured value of the timer T312 is greater than at least one timer T312 related threshold; or

(3) a ratio between a value of elapsed running time of a timer T304 and a configured value of the timer T304 is greater than at least one timer T304 related threshold.

Embodiment 2 (a new trigger condition for a near-failure LTM)

LTM is a procedure intended to reduce interruption time during mobility, that is why an early TA acquisition procedure may be triggered by a PDCCH order or realized through a UE-based TA measurement as configured by RRC signaling. In the case of triggering an early TA acquisition procedure by a PDCCH order, a gNB or gNB-DU to which a candidate cell belongs calculates a TA value and sends the TA value to the gNB or gNB-DU to which the serving cell belongs via a gNB-CU. The serving cell sends the TA value in a lower layer message (e.g. an LTM cell switch command MAC CE) when triggering an LTM cell switch. In the case of a UE-based TA measurement, the UE performs a TA measurement for one or more candidate cells after being configured by RRC signaling, and then the UE applies the TA value measured by itself and performs a RACH-less LTM upon receiving the cell switch command. If the valid TA value is provided in the cell switch command, the UE applies the TA value as instructed by the network. In the case where a UE-based TA measurement is configured, but no valid TA value is provided in the cell switch command, the UE applies the valid TA value measured by itself if available. Meanwhile, the UE performs a RACH-less LTM cell switch upon receiving the cell switch command. If no valid TA value is available, the UE performs a RACH-based LTM cell switch. If a RACH-less based LTM is not configured or is not initiated or failed, the interruption time will increase even if the LTM procedure is successful. Therefore, it is necessary to log early TA acquisition related information or early UL synchronization related information or RACH-less LTM related information or RACH based LTM related information, to optimize the LTM related configuration.

In Embodiment 2, in order to log successful LTM related information in a successful report (e.g. SHR and/or SPR) , one or more new trigger conditions are considered. For example, the UE may be configured of at least one of following LTM specific trigger conditions for a successful report (e.g. SHR and/or SPR) :

- an early TA acquisition procedure is not configured to a UE or is not triggered by a PDCCH order (e.g. which may be generated by a CU or a source DU or configured to the UE by default) ;

- a UE-based TA measurement is not configured to a UE (e.g. which may be generated by a CU or a source DU or configured to the UE by default) ;

- a TA value acquired in an early TA acquisition is invalid (e.g. expiry of TAT) , or a TA value provided in an LTM cell switch command is not valid, or no valid TA value is provided in the LTM cell switch command (e.g. which may be generated by a CU or a source DU or configured to the UE by default) ;

- a TA value measured by a UE is not valid (e.g. which may be generated by a CU or a source DU or configured to the UE by default) ;

- no valid TA value is available or a RACH-less LTM cell switch is not performed (e.g. which may be generated by a CU or a source DU or configured to the UE by default) ;

- a RACH-less LTM cell switch is not successful (e.g. which may be generated by a CU or a source DU or configured to the UE by default) ; or

- a time threshold which is related to time duration between receiving a lower layer message (e.g. an LTM cell switch command MAC CE) and successfully accessing to a target cell, or related to time duration between receiving an RRC reconfiguration message for LTM and successfully accessing to the target cell (e.g. the time threshold may be generated by a CU or a source DU or a target DU or a candidate target DU or configured to the UE by default) . When time duration for accessing to the target cell (e.g. time between receiving the LTM cell switch command (e.g. an LTM cell switch command MAC CE) and successfully accessing to the target cell, or time between receiving the RRC reconfiguration message for LTM and successfully access to the target cell) is longer than the time threshold, the successful report (e.g. SHR and/or SPR) may be generated by the UE.

The above LTM specific trigger conditions for a successful report (e.g. SHR and/or SPR) may be configured to the UE by default or via an RRC message or via a lower layer message (e.g. an LTM cell switch command MAC CE) .

In Embodiment 2, the successful report (e.g. SHR and/or SPR) may be triggered when at least one of the above LTM specific trigger conditions is fulfilled. When the successful report (e.g. SHR and/or SPR) is triggered, the UE may store or report at least one of following information in the successful report (e.g. SHR and/or SPR) :

- a corresponding cause value (e.g. a cause value indicating which trigger condition is fulfilled) ; or

- time duration for accessing to a target cell (e.g. time duration between receiving a lower layer message (e.g. an LTM cell switch command MAC CE) and successfully accessing to the target cell, or time duration between receiving an RRC reconfiguration message for LTM and successfully access to the target cell) .

Embodiment 3 (UHI for LTM or MHI for LTM)

In an LTM cell switch procedure, a ping-pong issue may happen due to pre-configured LTM candidate cell configurations and unstable L1 measurements. Therefore, UE history information (UHI) or mobility history information (MHI) , and ping-pong detection or ping-pong optimization for LTM are considered in Embodiment 3.

Embodiment 3-1 (UHI stored in a DU)

For Intra-gNB-DU LTM, regarding UHI stored in a DU, there may be following embodiments.

A (serving) DU collects UHI or updates its stored UHI (in a new cell) upon transmitting a lower layer message (e.g. an LTM cell switch command MAC CE) message or upon sending the DU-CU CELL SWITCH NOTIFICATION message or upon sending the ACCESS SUCCESS message or upon reception of the RRC reconfiguration complete message after successful access to the target cell or upon sending the UL RRC MESSAGE TRANSFER message. For instance, the DU may perform one of the following operations:

- the DU calculates that time duration of a UE staying in a first cell equals to "time duration between sending an ACCESS SUCCESS message to a CU for the first cell and sending a lower layer message (e.g. an LTM cell switch command MAC CE) to the UE for a next target cell" , the next target cell is a cell where the UE stayed after the first cell;

- the DU calculates that time duration of a UE staying in a first cell equals to "time duration between sending a lower layer message (e.g. an LTM cell switch command MAC CE) to the UE for the first cell and sending the LTM cell switch command (e.g. MAC CE) to the UE for the next target cell" ;

- the DU calculates that time duration of a UE staying in a first cell equals to "time duration between sending a DU-CU CELL SWITCH NOTIFICATION message to a CU for the first cell and sending the DU-CU CELL SWITCH NOTIFICATION message to the CU for the next target cell" ;

- the DU calculates that time duration of a UE staying in a first cell equals to "time duration between sending an ACCESS SUCCESS message to a CU for the first cell and sending the ACCESS SUCCESS message to the CU for the next target cell" ; and/or

- the DU calculates that time duration of a UE staying in a first cell equals to "time duration between sending a UL RRC MESSAGE TRANSFER message to a CU for the first cell and sending a UL RRC MESSAGE TRANSFER message to the CU for the next target cell" .

For Inter-gNB-DU LTM, regarding UHI stored in a DU, there may be following embodiments.

A DU collects UHI or updates its stored UHI upon transmitting a lower layer message (e.g. an LTM cell switch command MAC CE) message or upon sending a DU-CU CELL SWITCH NOTIFICATION message or upon reception of an RRC reconfiguration complete message after successful accessing to a target cell or upon sending a UL RRC MESSAGE TRANSFER message. For instance, the DU may perform one of the following operations:

- the DU calculates the time duration of a UE staying in a first cell equals to "time duration between sending an ACCESS SUCCESS message to a CU for the first cell and sending a lower layer message (e.g. an LTM cell switch command MAC CE) to the UE for a next target cell” , the next target cell is a cell where the UE stayed after the first cell;

- the DU calculates time duration of a UE staying in a first cell equals to "time duration between sending a UL RRC MESSAGE TRANSFER message to a CU for the first cell and sending a lower layer message (e.g. an LTM cell switch command MAC CE) to the UE for the next target cell; " and/or

- the DU calculates time duration of a UE staying in a first cell equals to "time duration between receiving an RRC reconfiguration complete message after successful accessing to the first cell and sending a lower layer message (e.g. an LTM cell switch command MAC CE) to the UE for the next target cell. "

In Embodiment 3-1, for Intra-gNB-DU LTM or Inter-gNB-DU LTM, a DU may detect whether there is a ping-pong issue, e.g. based on the UHI (e.g. which is collected by the DU itself, or which is stored or reported by the UE) . Optionally, the DU may send the identified ping-pong issue to its CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for the LTM procedure for the UE) , e.g. via a new introduced F1 message or an existing F1 message.

In Embodiment 3-1, for Intra-gNB-DU LTM or Inter-gNB-DU LTM, a DU may send the latest UHI (e.g. which is collected by the DU itself) to its CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for the LTM procedure for the UE) timely upon that the UHI is collected or updated or upon that the UE is switched to another cell or another DU, e.g. via a new introduced F1 message or an existing F1 message (e.g. a UE CONTEXT MODIFICATION RESPONSE message, a UL RRC MESSAGE TRANSFER message, a DU-CU CELL SWITCH NOTIFICATION message, an ACCESS SUCCESS message, or a UL RRC MESSAGE TRANSFER message) . Optionally, the CU may send the UHI (e.g. which is received from the DU, or which is stored or reported by the UE) to other DU (s) timely, e.g. via a new introduced F1 message or an existing F1 message (e.g. a CU-DU CELL SWITCH NOTIFICATION message) . The CU may detect whether there is a ping-pong issue, e.g. based on UE history information (e.g. which is received from the DU, or which is stored or reported by the UE) . Optionally, CU may send the identified ping-pong issue to relevant DU (e.g. the DU where ping-pong happens) , e.g. via a new introduced F1 message or an existing F1 message.

In Embodiment 3-1, MRO optimization may be performed (e.g. by the CU or the DU) , to avoid a ping-pong issue.

Embodiment 3-2 (UHI stored in a CU)

For Intra-gNB-DU LTM, regarding UHI stored in a CU, there may be following embodiments.

A CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for an LTM procedure for a UE) collects UHI or updates its stored UHI upon receiving a DU-CU CELL SWITCH NOTIFICATION message or upon receiving an ACCESS SUCCESS message or upon receiving a UL RRC MESSAGE TRANSFER message. For instance, the CU may perform one of the following operations:

- the CU calculates that time duration of a UE staying in a first cell equals to "time duration between receiving the ACCESS SUCCESS message for the first cell and receiving DU-CU CELL SWITCH NOTIFICATION message for next target cell" , the next target cell is a cell where the UE stayed after the first cell;

- the CU calculates that time duration of a UE staying in a first cell equals to "time duration between receiving the DU-CU CELL SWITCH NOTIFICATION message for the first cell and receiving the DU-CU CELL SWITCH NOTIFICATION message for the next target cell" ;

- the CU calculates that time duration of a UE staying in a first cell equals to "time duration between receiving the ACCESS SUCCESS message for the first cell and receiving the ACCESS SUCCESS message for the next target cell" ; and/or

- the CU calculates that time duration of a UE staying in a first cell equals to "time duration between receiving the UL RRC MESSAGE TRANSFER message for the first cell and receiving the UL RRC MESSAGE TRANSFER message for the next target cell" .

For Inter-gNB-DU LTM, regarding UHI stored in a CU, there may be following embodiments.

- the CU calculates that time duration of a UE staying in a first cell equals to "time duration between receiving the ACCESS SUCCESS message for the first cell and receiving the DU-CU CELL SWITCH NOTIFICATION message for a next target cell" , the next target cell is a cell where the UE stayed after the first cell;

- the CU calculates that time duration of a UE staying in a first cell equals to "time duration between receiving the UL RRC MESSAGE TRANSFER message for the first cell and receiving the DU-CU CELL SWITCH NOTIFICATION message for the next target cell" ;

In Embodiment 3-2, for Intra-gNB-DU LTM or Inter-gNB-DU LTM, a CU may detect whether there is a ping-pong issue, e.g. based on the UHI (e.g. which is collected by the CU itself, or which is stored or reported by the UE) . Optionally, the CU may send the identified ping-pong issue to the corresponding DU (e.g. a source DU or a target DU or a serving DU or a DU where a ping-pong happens) , e.g. via a new introduced F1 message or an existing F1 message.

In Embodiment 3-2, for Intra-gNB-DU LTM or Inter-gNB-DU LTM, a CU may send the latest UHI (e.g. which is collected by the CU itself, or which is stored or reported by the UE) to a DU (e.g. a source DU, a target DU, or a candidate target DU or a serving DU) , e.g. via a new introduced F1 message or an existing F1 message (e.g. a UE CONTEXT MODIFICATION REQUEST message or a DL RRC MESSAGE TRANSFER message or other) . The DU may detect whether there is a ping-pong issue, e.g. based on the UHI (e.g. which is received from the CU, or which is stored or reported by the UE) . Optionally, the DU may send the identified ping-pong issue to the CU, e.g. via a new introduced F1 message or an existing F1 message.

In Embodiment 3-2, MRO optimization may be performed (e.g. by the CU or the DU) , to avoid a ping-pong issue.

Embodiment 3-3 (MHI stored in a UE)

For Intra-gNB-DU or Inter-gNB-DU LTM, regarding MHI stored in a UE, there may be following embodiments.

A UE collects MHI or updates its stored MHI upon receiving a lower layer message (e.g. an LTM cell switch command MAC CE) , or upon an LTM cell switch execution is successful, or upon sending an RRC reconfiguration complete message e.g. after successful accessing to a target cell. The UE may detect a ping-pong issue, e.g. based on the MHI (e.g. which is collected by the UE itself) .

- Optionally, in an example, the UE may send the identified ping-pong issue to the corresponding DU (e.g. a source DU or a target DU or a serving DU or a DU where ping-pong happens) . Optionally, the DU (e.g. e.g. the source DU or the target DU or the serving DU or the DU where ping-pong happens) may send the identified ping-pong issue to the CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures an RRC Reconfiguration message for the LTM procedure for the UE) .

- In an example, the UE may report the identified ping-pong issue, e.g. in an RLF report or a SHR or a SPR or a SCG Failure Information message or other message. Optionally, the CU (e.g. which determines to initiate one or more LTM configurations or which generates or configures the RRC Reconfiguration message for the LTM procedure for the UE) may send the identified ping-pong issue (e.g. which is received from the UE) to the DU (e.g. the source DU or the target DU or the serving DU or the DU where ping-pong happens) .

In Embodiment 3-3, MRO optimization may be performed (e.g. by the CU or the DU) , to avoid a ping-pong issue.

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 unit of a base station (BS) , comprising:

at least one memory; and

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

obtain information regarding whether a L1/L2-Triggered Mobility (LTM) cell switch to wrong or sub-optimal beam occurs.
The unit of Claim 1, wherein to obtain the information, the at least one processor is configured to cause the unit to:

receive first information related to a connection failure, wherein the connection failure occurs during an LTM cell switch execution or shortly after a successful completion of the LTM cell switch execution.
The unit of Claim 2, wherein the unit is a centralized unit (CU) of the BS, the at least one processor is configured to cause the CU to further perform at least one of:

determining whether an LTM cell switch to wrong or sub-optimal beam occurs; or

transmitting the first information to a distributed unit (DU) of the BS.
The unit of Claim 3, wherein the at least one processor is configured to cause the CU to determine that the LTM cell switch to wrong or sub-optimal beam occurs in case that:

the connection failure occurs during the LTM cell switch execution, or the connection failure occurs shortly after the successful completion of the LTM cell switch execution; and

a user equipment (UE) attempts to recover or re-establish or reconnect a radio link connection in a cell where the connection failure occurs, wherein a first beam where the connection failure occurred and a second beam where the UE successfully recover or re-establish or reconnect a radio link connection are different beams but belong to a same cell.
The unit of Claim 3 or Claim 4, wherein in response to determining that the LTM cell switch to wrong or sub-optimal beam occurs, the at least one processor is configured to cause the CU to transmit to a source DU of the BS:

information indicating that the LTM cell switch to wrong or sub-optimal beam occurs;

failure type information concerning a wrong or sub-optimal beam selection at the source DU; or

a combination thereof.
The unit of Claim 3, wherein the at least one processor is configured to cause the CU to transmit the first information to a source DU of the BS.
The unit of Claim 6, wherein the at least one processor is configured to cause the CU to receive from the source DU:

information indicating that the LTM cell switch to wrong or sub-optimal beam occurs;

failure type information concerning a wrong or sub-optimal beam selection at the source DU; or

a combination thereof.
The unit of Claim 2, wherein the first information includes information related to a beam where a beam failure recovery is performed.
The unit of Claim 2, wherein the unit is a source distributed unit (DU) of the BS, and the at least one processor is configured to cause the source DU to perform at least one of following operations:

receiving at least one of the following:

the first information related to the connection failure;

information indicating that an LTM cell switch to wrong or sub-optimal beam occurs; or

failure type information concerning a wrong or sub-optimal beam selection at the source DU; or

determining whether the LTM cell switch to wrong or sub-optimal beam occurs.
The unit of Claim 9, wherein the at least one processor is configured to cause the source DU to determine that the LTM cell switch to wrong or sub-optimal beam occurs in case that:

the connection failure occurs during the LTM cell switch execution, or the connection failure occurs shortly after the successful completion of the LTM cell switch execution; and

a user equipment (UE) attempts to recover or re-establish or reconnect a radio link connection in a cell where the connection failure occurs, wherein a first beam where the connection failure occurred and a second beam where the UE successfully recover or re-establish or reconnect a radio link connection are different beams but belong to a same cell.
The unit of Claim 9, wherein in response to receiving the first information, the at least one processor is configured to cause the source DU to perform a root cause analysis or determine whether the LTM cell switch to wrong or sub-optimal beam occurs.
The unit of any of Claims 9-11, wherein in response to receiving the first information and in response to determining that the LTM cell switch to wrong or sub-optimal beam occurs, the at least one processor is configured to cause the source DU to transmit to a centralized unit (CU) of the BS:

information indicating that the LTM cell switch to wrong or sub-optimal beam occurs;

failure type information concerning a wrong or sub-optimal beam selection at the source DU; or

a combination thereof.
The unit of Claim 1, wherein the at least one processor is configured to cause the unit to:

obtain configuration information of at least one trigger condition for a user equipment (UE) to store or report successful L1/L2-Triggered Mobility (LTM) related information, wherein the successful LTM related information is related to a near-failure successful LTM cell switch or subsequent LTM cell switch; and

transmit the configuration information.
The unit of Claim 13, wherein the configuration information of the at least one trigger condition includes:

a first condition concerning that an early timing advance (TA) acquisition procedure is not configured to the UE;

a second condition concerning that the early TA acquisition procedure is not triggered by a physical downlink control channel (PDCCH) order;

a third condition concerning that a UE-based TA measurement is not configured to the UE;

a fourth condition concerning that a TA value acquired in the early TA acquisition procedure is not valid;

a fifth condition concerning that a TA value provided in a lower layer message is not valid;

a sixth condition concerning that no valid TA value is provided in the lower layer message;

a seventh condition concerning that a TA value measured by the UE is not valid;

an eighth condition concerning that no valid TA value is available via the UE-based TA measurement;

a ninth condition concerning that a random access channel (RACH) -less LTM cell switch is not performed;

a tenth condition concerning that the RACH-less LTM cell switch is not successful;

a threshold related with accessing to a target cell;

an eleventh condition concerning that a beam failure recovery is performed during an LTM cell switch procedure or a subsequent LTM cell switch procedure;

a timer T310 related threshold related with a ratio between a value of elapsed running time of a timer T310 and a configured length value of the timer T310;

a timer T312 related threshold related with a ratio between a value of elapsed running time of a timer T312 and a configured length value of the timer T312;

a timer T304 related threshold related with a ratio between a value of elapsed running time of a timer T304 and a configured length value of the timer T304; or

a combination thereof.
The unit of Claim 13, wherein the at least one processor is configured to cause the unit to receive successful LTM related information, and wherein the successful LTM related information includes at least one of:

information related to a beam where a beam failure recovery is performed;

a cause value for storing or reporting the successful LTM related information;

time duration between receiving a lower layer message and successfully accessing to a target cell;

time duration between receiving a radio resource control (RRC) reconfiguration message and successfully accessing to the target cell; or

a time point for successfully accessing to the target cell.
The unit of Claim 13, wherein the unit is a centralized unit (CU) of the BS, and wherein to obtain the configuration information, the at least one processor is configured to cause the CU to:

generate the configuration information; or

receive the configuration information from at least one DU, wherein the configuration information is generated by at least one of a source DU or a candidate DU of the BS.
The unit of Claim 13, wherein the unit is a source distributed unit (DU) of the BS, to obtain the configuration information, the at least one processor is configured to cause the source DU to receive the configuration information from a centralized unit (CU) of the BS, and wherein the configuration information is generated by at least one of the CU or a candidate DU of the BS.
The unit of Claim 13, wherein the unit is a source distributed unit (DU) of the BS, to obtain the configuration information, the at least one processor is configured to cause the source DU to generate the configuration information.
A processor for wireless communication, comprising:

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

obtain information regarding whether a L1/L2-Triggered Mobility (LTM) cell switch to wrong or sub-optimal beam occurs.
A method performed by a unit of a base station (BS) , comprising:

obtaining information regarding whether a L1/L2-Triggered Mobility (LTM) cell switch to wrong or sub-optimal beam occurs.