Method and device for TA acquisition and calculation

Abstract

Aspects of the present disclosure relate to methods and apparatus for timing advance (TA) acquisition and / or TA calculation during wireless communications. In accordance with an embodiment of the present disclosure, a user equipment (UE) comprises: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the UE to: receive a radio resource control (RRC) reconfiguration message from a base station (BS), where the RRC reconfiguration message includes a cell handover configuration for a set of candidate cells related to lower layer triggered mobility (LTM); receiving a cell handover command from the BS, wherein the cell handover command includes identifier (ID) information related to candidate cells in the set of candidate cells; and performing a cell handover to the candidate cell based on the cell handover command.

Description

Technical Field

[0001] The present disclosure relates to wireless communications, and more particularly, to methods and apparatus for timing advance (TA) acquisition and / or TA calculation during wireless communications. Background Art

[0002] A wireless communication system may include one or more network communication devices, such as base stations, which may support wireless communication with one or more user communication devices, which may also be referred to as user equipment (UE) or other appropriate terms. A wireless communication system may support wireless communication with one or more user communication devices by utilizing resources of the wireless communication system, such as time resources (e.g., symbols, time slots, subframes, frames, etc.) or frequency resources (e.g., subcarriers, carriers, etc.). In addition, a wireless communication system may support wireless communication across various radio access technologies, including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, and other appropriate radio access technologies above 5G (e.g., sixth generation (6G)). Summary of the Invention

[0003] The article "a" before an element is not limited and should be understood to mean "at least one" of those elements or "one or more" of those elements. The terms "one", "at least one", "one or more" and "at least one of one or more" are interchangeable. As used herein (included in the claims), as used in a project list (for example, a project list preceded by phrases such as "at least one of..." or "one or more of..." or "one or both of..."), the "or" indicates an inclusive list, so 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 (that is, A and B and C). Moreover, as used herein, the phrase "based on" should not be interpreted as a reference to a set of closed conditions. For example, the exemplary step described as "based on condition A" can be based on both condition A and condition B without departing from the scope of this disclosure. In other words, as used herein, the phrase "based on" should be interpreted in the same manner as the phrase "at least in part based on". Furthermore, as used herein, including in the claims, a "set" may comprise one or more elements.

[0004] Some embodiments of the present disclosure provide a user equipment (UE). The UE includes at least one memory; and at least one processor coupled to the at least one memory and configured to cause the UE to: receive a radio resource control (RRC) reconfiguration message from a base station (BS), wherein the RRC reconfiguration message includes a cell switching configuration for a set of candidate cells; receive a cell switching command from the BS, wherein the cell switching command includes identifier (ID) information related to a first candidate cell within the set of candidate cells; and perform a cell switching to the first candidate cell based on the cell switching command.

[0005] In some embodiments of the UE described herein, the cell switching command includes at least one of: index information of the candidate cell configuration of the first candidate cell; a first timing advance (TA) value for the first candidate cell; or a timer length of a timing advance timer (TAT) associated with the first TA value.

[0006] In some embodiments of the UE described herein, the processor is configured to cause the UE to: initiate a re-establishment procedure if the UE fails to access the first candidate cell; and maintain a first configuration if first information indicating that the set of candidate cells can be used for recovery has been configured to the UE, wherein the first configuration includes at least a configuration for a primary cell in a primary cell or a secondary cell group (SpCell), a configuration for one or more primary cell groups (MCG) secondary cells (SCells), a multi-radio dual connectivity (MR-DC) configuration, an overheat assistance configuration, and an in-device coexistence (IDC) assistance configuration; or release the first configuration if the first information is not configured to the UE.

[0007] In some implementations of the UE described herein, the processor is configured to cause the UE to: select a second candidate cell for an RRC re-establishment procedure; determine whether the second candidate cell is one candidate cell within the set of candidate cells; and if the second candidate cell is one candidate cell within the set of candidate cells, apply a cell switching configuration to the second candidate cell and perform a cell switching to the second candidate cell; or if the second candidate cell is not one candidate cell within the set of candidate cells and if the first information has been configured to the UE, release the first configuration.

[0008] In some implementations of the UE described herein, the processor is configured to cause the UE to: transmit an RRC reconfiguration complete message associated with the second candidate cell to the CU, and wherein the RRC reconfiguration complete message includes identifier (ID) information related to the second candidate cell.

[0009] In some implementations of the UE described herein, the RRC reconfiguration message includes second information instructing the UE to calculate at least one of: a first TA value for the first candidate cell; or a second TA value for a second candidate cell.

[0010] In some implementations of the UE described herein, whether the UE is to calculate a TA value is determined by a centralized unit (CU) of the BS, one or more candidate DUs of the BS, or a source distributed unit (DU) of the BS.

[0011] In some implementations of the UE described herein, the processor is configured to cause the UE to: in response to receiving the second information including ID information of the first candidate cell, regard the first TA value for the first candidate cell as not included in the cell switching command for the first candidate cell.

[0012] In some implementations of the UE described herein, the processor is configured to cause the UE to: after receiving the second information including ID information of both the first candidate cell and the second candidate cell, calculate the first TA value for the first candidate cell and the second TA value for the second candidate cell.

[0013] In some embodiments of the UE described herein, the first TA value or the second TA value is calculated based on at least one of: a reception timing difference between a source cell of the UE and the first candidate cell or the second candidate cell; or a TA value for the source cell.

[0014] In some implementations of the UE described herein, the processor is configured to cause the UE to: if a physical downlink control channel (PDCCH) command for a TA acquisition procedure for the first candidate cell is received, then: discard the first TA value for the first candidate cell; or maintain the first TA value for the first candidate cell before receiving a third TA value for the first candidate cell from a source distributed unit (DU) of the BS, and discard the first TA value for the first candidate cell after receiving the third TA value from the source DU; or if the cell switching command includes the third TA value, then: discard the first TA value for the first candidate cell and perform cell switching to the first candidate cell using the third TA value.

[0015] In some implementations of the UE described herein, the processor is configured to cause the UE to release or store the second TA value for the second candidate cell after the UE switches to the first candidate cell.

[0016] In some implementations of the UE described herein, the processor is configured to cause the UE to: in response to storing the second TA value for the second candidate cell, determine whether the second TA value is valid based on a timing advance timer (TAT) associated with the second TA value.

[0017] In some implementations of the UE described herein, the processor is configured to cause the UE to release or store the first TA value for the first candidate cell after the UE switches to the first candidate cell.

[0018] In some implementations of the UE described herein, the processor is configured to cause the UE to: in response to storing the first TA value for the first candidate cell, report the first TA value to a candidate DU associated with the first candidate cell via an RRC message or a media access control (MAC) control element (CE).

[0019] In some implementations of the UE described herein, the processor is configured to cause the UE to: receive an increment value for updating the first TA value from the candidate DU associated with the first candidate cell.

[0020] In some implementations of the UE described herein, the processor is configured to cause the UE to: in response to storing the first TA value for the first candidate cell, receive an absolute TA value for the first candidate cell from a candidate DU associated with the first candidate cell; release the first TA value; and store the absolute TA value for the first candidate cell.

[0021] In some implementations of the UE described herein, the processor is configured to cause the UE to continue updating the first TA value before receiving the incremental value or the absolute TA value from the candidate DU associated with the first candidate cell.

[0022] In some embodiments of the UE described herein, in order to continue updating the first TA value, the processor is configured to cause the UE to: store the TA value of the source cell of the UE; receive a timer length of a first timing advance timer (TAT) associated with the TA value of the source cell; continue to update the first TA value based on the TA value of the source cell before the first TAT expires; and consider the first TA value invalid immediately after the first TAT expires.

[0023] In some implementations of the UE described herein, the processor is configured to cause the UE to: in response to considering the first TA value as invalid, trigger a random access channel (RACH) procedure for uplink (UL) synchronization.

[0024] Some embodiments of the present disclosure provide a method performed by a user equipment (UE), the method comprising: receiving a radio resource control (RRC) reconfiguration message from a base station (BS), wherein the RRC reconfiguration message includes a cell handover configuration for a set of candidate cells; receiving a cell handover command from the BS, wherein the cell handover command includes identifier (ID) information related to a first candidate cell within the set of candidate cells; and performing a cell handover to the first candidate cell based on the cell handover command.

[0025] Some embodiments of the present disclosure provide a processor for wireless communications, comprising: at least one controller coupled to at least one memory and configured to cause the processor to: receive a radio resource control (RRC) reconfiguration message from a base station (BS), wherein the RRC reconfiguration message includes a cell switching configuration for a set of candidate cells; receive a cell switching command from the BS, wherein the cell switching command includes identifier (ID) information related to a first candidate cell within the set of candidate cells; and perform a cell switching to the first candidate cell based on the cell switching command.

[0026] Some embodiments of the present disclosure provide a source decentralized unit (DU) of a base station (BS). The source decentralized unit (DU) includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the source decentralized unit (DU) to: receive a first timing advance (TA) value list for a set of candidate cells from a centralized unit (CU) of the BS, wherein the first TA value list includes a first TA value for a first candidate cell within the set of candidate cells; and transmit a cell handover command to a user equipment (UE), wherein the cell handover command includes identifier (ID) information related to the first candidate cell.

[0027] In some implementations of the source DU described herein, the cell switching command includes at least one of: the first TA value for the first candidate cell; or a timer length of a timing advance timer (TAT) associated with the first TA value.

[0028] In some implementations of the source DU described herein, the first TA value list further includes a second TA value for a second candidate cell within the set of candidate cells.

[0029] In some implementations of the source DU described herein, the processor is configured to cause the source DU to: after transmitting the cell switching command, transmit at least one of the following to a candidate distributed unit (DU) of the BS associated with the first candidate cell via the CU: a second TA value list; or additional information associated with the second TA value list.

[0030] In some embodiments of the source DU described herein, the second TA value list includes all TA values ​​in the first TA value list, or includes all TA values ​​in the first TA value list except the first TA value for the first candidate cell included in the cell handover command.

[0031] In some implementations of the source DU described herein, the additional information associated with a TA value within the TA value list includes at least one of: an absolute time when the TA value is received; a time elapsed from receipt of the TA value; or a remaining validity period of the TA value.

[0032] Some embodiments of the present disclosure provide a method performed by a source decentralized unit (DU) of a base station (BS), the method comprising: receiving a first timing advance (TA) value list for a set of candidate cells from a centralized unit (CU) of the BS, wherein the first TA value list comprises a first TA value for a first candidate cell within the set of candidate cells; and transmitting a cell handover command to a user equipment (UE), wherein the cell handover command comprises identifier (ID) information related to the first candidate cell.

[0033] Some embodiments of the present disclosure provide a processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to cause the processor to: receive a first timing advance (TA) value list for a set of candidate cells from a centralized unit (CU) of the BS, wherein the first TA value list includes a first TA value for a first candidate cell within the set of candidate cells; and transmit a cell switching command to a user equipment (UE), wherein the cell switching command includes identifier (ID) information related to the first candidate cell.

[0034] Some embodiments of the present disclosure provide a centralized unit (CU) of a base station (BS). The CU includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the CU to: transmit a request for a cell switching configuration for a set of candidate cells to one or more candidate decentralized units (DUs) of the BS; receive responses corresponding to the request from the one or more candidate DUs, wherein the responses include the cell switching configurations for the set of candidate cells; and transmit the cell switching configurations for the set of candidate cells to a user equipment (UE) via a source DU of the BS based on the responses.

[0035] In some implementations of the CU described herein, the processor is configured to cause the CU to receive a radio resource control (RRC) reconfiguration complete message associated with a second candidate cell within the set of candidate cells from the UE after the UE fails to switch to the first candidate cell, wherein the RRC reconfiguration complete message includes identifier (ID) information related to the second candidate cell.

[0036] In some implementations of the CU described herein, the processor is configured to cause the CU to transmit at least one of the following to the candidate DU associated with the second candidate cell after receiving the RRC reconfiguration complete message: a TA value list; or additional information associated with the TA value list.

[0037] In some implementations of the CU described herein, the processor is configured to cause the CU to receive at least one of the following from the source DU after the source DU transmits a cell switching command including identifier (ID) information related to a first candidate cell: a TA value list; or additional information associated with the TA value list.

[0038] In some implementations of the CU described herein, the additional information associated with the TA value within the TA value list includes at least one of: the absolute time when the TA value was received; the time elapsed from the receipt of the TA value; or the remaining valid period of the TA value.

[0039] In some implementations of the CU described herein, the processor is configured to cause the CU to transmit at least one of the list of TA values ​​or the additional information to the second candidate cell.

[0040] In some implementations of the CU described herein, the request for cell handover configuration includes first information indicating that the UE is to calculate a TA value for a candidate cell.

[0041] In some implementations of the CU described herein, the processor is configured to cause the CU to: receive at least one of the following from the one or more candidate DUs: second information indicating that the UE will calculate one or more TA values ​​for the set of candidate cells; or reference signal (RS) configuration information configured to the UE.

[0042] In some implementations of the CU described herein, the second information is included in the cell handover configuration to the UE.

[0043] Some embodiments of the present disclosure provide a method performed by a centralized unit (CU) of a base station (BS). The method includes: transmitting a request for a cell switching configuration for a set of candidate cells to one or more candidate decentralized units (DUs) of the BS; receiving a response corresponding to the request from the one or more candidate DUs, wherein the response includes the cell switching configuration for the set of candidate cells; and transmitting the cell switching configuration for the set of candidate cells to a user equipment (UE) via a source DU of the BS based on the response.

[0044] Some embodiments of the present disclosure provide a processor for wireless communications, comprising: at least one controller coupled to at least one memory and configured to cause the processor to: transmit a request for a cell switching configuration for a set of candidate cells to one or more candidate distributed units (DUs) of the BS; receive a response corresponding to the request from the one or more candidate DUs, wherein the response includes the cell switching configuration for the set of candidate cells; and transmit the cell switching configuration for the set of candidate cells to a user equipment (UE) via a source DU of the BS based on the response.

[0045] Some embodiments of the present disclosure provide a candidate distributed unit (DU) of a base station (BS). The candidate DU includes: at least one memory; and at least one processor coupled to the at least one memory and configured to cause the candidate DU to: receive a request for a cell switching configuration for a set of candidate cells for a user equipment (UE) from a centralized unit (CU) of the BS; and transmit a response to the CU based on the request, wherein the response includes a configuration related to the set of candidate cells for the UE, and wherein the set of candidate cells includes a first candidate cell.

[0046] In some implementations of the candidate DU described herein, the processor is configured to cause the candidate DU to: receive from the CU at least one of: a list of timing advance (TA) values ​​for the set of candidate cells; a list of TA values ​​other than a first TA value for the first candidate cell, to which the UE is configured to switch; or additional information associated with the list of TA values.

[0047] In some implementations of the candidate DU described herein, the additional information associated with the TA value within the TA value list includes at least one of: the absolute time when the TA value was received; the time elapsed since the TA value was received; or the remaining validity period of the TA value.

[0048] In some implementations of the candidate DU described herein, the processor is configured to cause the candidate DU to transmit to the CU at least one of: second information indicating that the UE will calculate one or more TA values ​​for the set of candidate cells; or reference signal (RS) configuration information configured to the UE.

[0049] In some implementations of the candidate DU described herein, the processor is configured to cause the candidate DU to determine whether the UE is to calculate the one or more TA values.

[0050] In some implementations of the candidate DU described herein, the processor is configured to cause the candidate DU to receive a first TA value for the first candidate cell from the UE via the CU, wherein the UE is configured to switch to the first candidate cell.

[0051] In some implementations of the candidate DU described herein, the processor is configured to cause the candidate DU to transmit, via the CU, to the UE, an increment value for updating the first TA value.

[0052] In some implementations of the candidate DU described herein, the processor is configured to cause the candidate DU to transmit, via the CU, an absolute TA value for the first candidate cell to the UE.

[0053] Some embodiments of the present disclosure provide a method performed by a candidate distributed unit (DU) of a base station (BS), the method comprising: receiving a request for a cell switching configuration for a set of candidate cells for a user equipment (UE) from a centralized unit (CU) of the BS; and transmitting a response to the CU based on the request, wherein the response includes a configuration related to the set of candidate cells for the UE, and wherein the set of candidate cells includes a first candidate cell.

[0054] Some embodiments of the present disclosure provide a processor for wireless communications, comprising: at least one controller coupled to at least one memory and configured to cause the processor to: receive a request for cell switching configuration for a set of candidate cells for a user equipment (UE) from a centralized unit (CU) of the BS; and transmit a response to the CU based on the request, wherein the response includes a configuration related to the set of candidate cells for the UE, and wherein the set of candidate cells includes a first candidate cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 Illustrated is an example of a wireless communication system in accordance with aspects of the present disclosure.

[0056] Figure 2 Illustrated is an example of a user equipment (UE) 200 in accordance with aspects of the present disclosure.

[0057] Figure 3 An example of a processor 300 is illustrated in accordance with aspects of the present disclosure.

[0058] Figure 4 An example of network equipment (NE) 400 is illustrated in accordance with aspects of the present disclosure.

[0059] Figure 5 A schematic diagram illustrating inter-cell layer 1 / layer 2 (L1 / L2) mobility in accordance with aspects of the present disclosure.

[0060] Figure 6 A flow chart illustrating a method performed by a UE according to aspects of the present disclosure is illustrated.

[0061] Figure 7 A flow chart illustrating a method performed by a source DU according to aspects of the present disclosure is illustrated.

[0062] Figure 8A flowchart illustrating a method performed by a CU according to aspects of the present disclosure is illustrated.

[0063] Figure 9 A flow chart illustrating a method performed by a candidate DU according to aspects of the present disclosure is shown.

[0064] Figure 10 Illustrated is an example of performing a cell handover according to aspects of the present disclosure.

[0065] Figure 11 Another example of performing a cell handover according to aspects of the present disclosure is illustrated.

[0066] Figure 12 Illustrated is an example of TA calculation according to aspects of the present disclosure. DETAILED DESCRIPTION

[0067] Some embodiments of the present disclosure may be applicable to the "lower layer triggered mobility" or "L1 / L2 triggered mobility" scenario, at least one of which may be abbreviated as "LTM." In the LTM scenario, a UE may access a serving BS (e.g., a serving gNB). The UE may report Layer 3 (L3) measurement results based on the configuration from the serving gNB. If the serving gNB (e.g., the CU of the serving gNB) decides to hand over the UE to a candidate cell based on the measurement results, the serving gNB may request the target DU to prepare the configuration for one or more candidate cells. After receiving the candidate cell configuration from the target DU of the serving gNB, the serving gNB may transmit an RRC reconfiguration message to the UE containing the ID information of the one or more candidate cells. For example, the CU may transmit the RRC reconfiguration message to the UE via the source DU of the serving gNB. The UE may transmit an RRC reconfiguration complete message to the serving gNB (e.g., the CU) via the source DU. The UE may ensure UL synchronization or DL ​​synchronization before receiving a cell handover command. For example, the UE may obtain or acquire a TA value via a random access (RA) or preamble transmission. For dynamic handover purposes, the UE may report Layer 1 (L1) measurements. The serving gNB (e.g., the source DU) may transmit a cell handover command, such as a MAC CE or downlink control information (DCI). The UE may apply an RRC reconfiguration message and start a timer upon receiving the lower layer command.

[0068] Currently, there are unresolved issues regarding TA acquisition and / or TA calculation in lower layer based mobility (LTM) scenarios in different scenarios. Embodiments of the present disclosure are intended to address such issues. For example, there may be a scenario for early TA acquisition based on PDCCH commands without the need for a random access response (RAR). In some embodiments of the present disclosure, in this scenario, the source DU stores some TA values ​​for some candidate cells for LTM. Some embodiments of the present disclosure study the maintenance of the TA values ​​stored in the source DU for successful LTM scenarios and LTM-based recovery scenarios. In some embodiments of the present disclosure, information related to the determination of TA value validity may be transmitted. For example, the source DU or CU may transmit information related to the determination of TA value validity.

[0069] For example, there may be scenarios where the UE can independently calculate or compute the TA value for a candidate cell, rather than acquiring or obtaining the TA value for the candidate cell from the NE or the network (e.g., TA acquisition or early TA acquisition). This scenario may also be referred to as a "UE-based TA measurement scenario" or a "UE-based TA calculation scenario," among others. UE-based TA measurement means that the UE independently calculates or computes the TA value based on, for example, the Rx timing difference between the UE's current serving cell and the candidate cell and the TA value for the UE's current serving cell. In this scenario, some embodiments of the present disclosure discuss the coexistence of UE-based TA measurement and early TA acquisition, for example, discussing the maintenance of the calculated TA value. Some embodiments of the present disclosure address the question of whether the UE should continue to maintain the calculated TA value. If so, the network may need to know the TA value for update purposes. The UE itself may continue to update the stored TA before receiving an update from the target cell. Some embodiments of the present disclosure address the question of which node is responsible for determining the use of UE-based TA measurement. Some embodiments of the present disclosure introduce F1 interface enhancements for the above scenarios.

[0070] In embodiments of the present disclosure, TA acquisition or early TA acquisition means that the UE is expected to perform a TA acquisition procedure before a cell handover procedure. TA reacquisition or early TA reacquisition means that the UE is expected to perform a TA reacquisition procedure before a cell handover procedure. TA acquisition, early TA acquisition, TA reacquisition, or early TA reacquisition may be triggered by receiving an indication (e.g., a PDCCH command as DCI) from the serving BS.

[0071] Specifically, in the present disclosure Figures 6 to 12In the embodiments, both inter-DU mobility and intra-DU mobility scenarios are considered, such as inter-gNB-DU LTM or intra-gNB-DU LTM. Inter-DU mobility means that the connection to the CU remains unchanged, while the UE can change from a source cell associated with a source DU to a target cell associated with a target DU due to mobility, while both the source DU and the target DU are managed by the CU. Intra-DU mobility means that the connection to the CU remains unchanged, while the UE can change from a source cell to a target cell associated with the same DU due to mobility. Aspects of the present disclosure are described in the context of a wireless communication system.

[0072] Figure 1 The diagram illustrates an example of a wireless communication system 100 according to various aspects of the present disclosure. The wireless communication system 100 may include one or more NEs 102, one or more UEs 104, and a core network (CN) 106. The wireless communication system 100 may support various radio access technologies. In some embodiments, the wireless communication system 100 may be a 4G network, such as an LTE network or an LTE-Advanced (LTE-A) network. In some other embodiments, the wireless communication system 100 may be an NR network, such as a 5G network, an Advanced 5G (5G-A) network, or a 5G Ultra-Wideband (5G-UWB) network. In other embodiments, the wireless communication system 100 may be a combination of a 4G network and a 5G network, or other suitable radio access technologies, including Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), or IEEE 802.20. The wireless communication system 100 may support radio access technologies beyond 5G, such as 6G. Additionally, the wireless communication system 100 may support technologies such as time division multiple access (TDMA), frequency division multiple access (FDMA), or code division multiple access (CDMA).

[0073] One or more NEs 102 may be dispersed throughout a geographic area to form a wireless communication system 100. One or more of the NEs 102 described herein may be, include, or be referred to as a network node, base station, network element, network function, network entity, radio access network (RAN), NodeB, eNodeB (eNB), next generation NodeB (gNB), or other appropriate terminology. The NEs 102 and the UEs 104 may communicate via a communication link, which may be a wireless or wired connection. For example, the NEs 102 and the UEs 104 may perform wireless communication (e.g., receive signaling, transmit signaling) via a Uu interface.

[0074] NE 102 may provide a geographic coverage area, and NE 102 may support services for one or more UEs 104 within the geographic coverage area. For example, NE 102 and UE 104 may support wireless communication of signals related to services (e.g., voice, video, packet data, messaging, broadcast, etc.) based on one or more radio access technologies. In some embodiments, NE 102 may be mobile, such as a satellite associated with a non-terrestrial network (NTN). In some embodiments, different geographic coverage areas 112 associated with the same or different radio access technologies may overlap, but different geographic coverage areas may be associated with different NE 102.

[0075] One or more UEs 104 may be dispersed throughout the geographic area of ​​the wireless communication 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, a UE 104 may be referred to as a unit, a station, a terminal, or a client, among other examples. Additionally or alternatively, a UE 104 may be referred to as an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or a Machine Type Communication (MTC) device, among other examples.

[0076] The UE 104 may be capable of supporting wireless communication directly with other UEs 104 via a communication link. For example, the UE 104 may support wireless communication directly with another UE 104 via 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 114 may be referred to as a sidelink. For example, the UE 104 may support wireless communication directly with another UE 104 via a PC5 interface.

[0077] NE 102 may support communication with CN 106, with another NE 102, or with both. For example, NE 102 may interface with other NEs 102 or CN 106 via one or more backhaul links (e.g., S1, N2, N2, or network interfaces). In some embodiments, NE 102 may communicate directly with each other. In some other embodiments, NE 102 may communicate with each other or indirectly (e.g., via CN 106). In some embodiments, one or more NEs 102 may include subcomponents such as access network entities, which may be instances of access node controllers (ANCs). The ANC may communicate with one or more UEs 104 via one or more other access network transport entities, which may be referred to as radio heads, smart radio heads, or transmit-receive points (TRPs).

[0078] The CN 106 may support user authentication, access authorization, tracking, connection, 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 control plane entities that manage access and mobility (e.g., a mobility management entity (MME), an access and mobility management function (AMF)) and user plane entities that route packets or interconnections 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 entities may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management (e.g., data bearer, signaling bearer, etc.) for one or more UEs 104 served by one or more NEs 102 associated with the CN 106.

[0079] The CN 106 may communicate with a packet data network via one or more backhaul links (e.g., via S1, N2, 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. The UE 104 may establish a session (e.g., a protocol data unit (PDU) session, etc.) with the CN 106 via the NE 102. The CN 106 may use the established session (e.g., the established PDU session) to route traffic (e.g., control information, data, etc.) between the UE 104 and the application server. A PDU session may be an instance of a logical connection between the UE 104 and the CN 106 (e.g., one or more network functions of the CN 106).

[0080] In the wireless communication system 100, the NE 102 and the UE 104 may use the resources of the wireless communication system 100 (e.g., time resources (e.g., symbols, time slots, subframes, frames, etc.) or frequency resources (e.g., subcarriers, carriers)) to perform various operations (e.g., wireless communication). In some implementations, the NE 102 and the UE 104 may support different resource structures. For example, the NE 102 and the UE 104 may support different frame structures. In some implementations, such as in 4G, the NE 102 and the UE 104 may support a single frame structure. In some other implementations, such as in 5G and other suitable radio access technologies, the NE 102 and the UE 104 may support various frame structures (i.e., multiple frame structures). The NE 102 and the UE 104 may support various frame structures based on one or more numerologies.

[0081] One or more parameter sets may be supported in the wireless communication system 100, and the parameter sets may include subcarrier spacing and cyclic prefixes. A first parameter set (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 parameter set (e.g., μ = 0) associated with the first subcarrier spacing (e.g., 15 kHz) may utilize one slot per subframe. A second parameter set (e.g., μ = 1) may be associated with a second subcarrier spacing (e.g., 30 kHz) and a normal cyclic prefix. A third parameter set (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 parameter set (e.g., μ = 3) may be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a normal cyclic prefix. A fifth parameter set (e.g., μ = 4) may be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a normal cyclic prefix.

[0082] The time intervals of resources (e.g., communication resources) may be organized according to frames (also referred to as radio frames). Each frame may have a duration, such as a duration of 10 milliseconds (ms). In some embodiments, each frame may include multiple subframes. For example, each frame may include 10 subframes, and each subframe may have a duration, such as a duration of 1 ms. In some embodiments, each frame may have the same duration. In some embodiments, each subframe of a frame may have the same duration.

[0083] Additionally or alternatively, time intervals of resources (e.g., communication resources) may be organized according to time slots. For example, a subframe may include a certain number (e.g., quantity) of time slots. The number of time slots in each subframe may also depend on one or more parameter sets supported in the wireless communication system 100. For example, the first parameter set, the second parameter set, the third parameter set, the fourth parameter set, and the fifth parameter set (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 one time slot per subframe, two time slots per subframe, four time slots per subframe, eight time slots per subframe, and 16 time slots per subframe, respectively. Each time slot may include a certain number (e.g., quantity) of symbols (e.g., OFDM symbols). In some implementations, the number (e.g., quantity) of time slots in a subframe may depend on the parameter set. For a normal cyclic prefix, a time slot may include 14 symbols. For an extended cyclic prefix (e.g., for a 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 the parameter set. It should be understood that references to a first parameter set (e.g., μ = 0) associated with a first subcarrier spacing (e.g., 15 kHz) may be used interchangeably between subframes and slots.

[0084] In the wireless communication system 100, the electromagnetic (EM) spectrum can be divided into various categories, frequency bands, channels, etc. based on frequency or wavelength. For example, the wireless communication system 100 can support one or more operating frequency bands, such as the frequency range designations FR1 (410 MHz to 7.125 GHz), FR2 (24.25 GHz to 52.6 GHz), FR3 (7.125 GHz to 24.25 GHz), FR4 (52.6 GHz to 114.25 GHz), FR4a or FR4-1 (52.6 GHz to 71 GHz), and FR5 (114.25 GHz to 300 GHz). In some embodiments, the NE 102 and the UE 104 can perform wireless communications on one or more of the operating frequency bands. In some embodiments, FR1 can be used by the NE 102 and the UE 104, as well as other equipment or devices for cellular communication traffic (e.g., control information, data). In some implementations, FR2 may be used by NEs 102 and UEs 104, as well as other equipment or devices for short-range, high data rate capabilities.

[0085] FR1 may be associated with one or more parameter sets (e.g., at least three parameter sets). For example, FR1 may be associated with a first parameter set (e.g., μ = 0) including a 15 kHz subcarrier spacing, a second parameter set (e.g., μ = 1) including a 30 kHz subcarrier spacing, and a third parameter set (e.g., μ = 2) including a 60 kHz subcarrier spacing. FR2 may be associated with one or more parameter sets (e.g., at least two parameter sets). For example, FR2 may be associated with a third parameter set (e.g., μ = 2) including a 60 kHz subcarrier spacing, and a fourth parameter set (e.g., μ = 3) including a 120 kHz subcarrier spacing.

[0086] Figure 2 An example of a UE 200 according to various aspects of the present disclosure is illustrated. 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.

[0087] The processor 202, memory 204, controller 206, or 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 to or otherwise support means for performing the functions described in the present disclosure.

[0088] 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, thereby causing the UE 200 to perform various functions of the present disclosure.

[0089] Memory 204 may include volatile or non-volatile memory. Memory 204 may store computer-readable, computer-executable code including instructions that, when executed by processor 202, cause UE 200 to perform the various functions described herein. The code may be stored in a non-transitory computer-readable medium, such as memory 204 or another type of memory. Computer-readable media includes both non-transitory computer storage media and communication media, including any media that facilitates the transfer of computer programs from one location to another. Non-transitory storage media may be any available media that can be accessed by a general-purpose or special-purpose computer.

[0090] In some implementations, the processor 202 and the memory 204 coupled to the processor 202 may be configured to cause the UE 200 to perform one or more of the functions described herein (e.g., execution of instructions stored in the memory 204 by the processor 202). For example, according to the examples disclosed herein, the processor 202 may support wireless communications at the UE 200. The UE 200 may be configured to support: means for receiving an RRC reconfiguration message from a BS, wherein the RRC reconfiguration message includes a cell handover configuration for a set of candidate cells; means for receiving a cell handover command from the BS, wherein the cell handover command includes ID information related to a candidate cell within the set of candidate cells; and means for performing a cell handover to a candidate cell based on the cell handover command.

[0091] The controller 206 may manage input and output signals of the UE 200. The controller 206 may also manage peripheral devices that are not integrated into the UE 200. In some implementations, the controller 206 may utilize, for example, In some embodiments, the controller 206 may be implemented as part of the processor 202 .

[0092] In some embodiments, the UE 200 may include at least one transceiver 208. In some other embodiments, 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 aforementioned means for receiving in the processor 202 or the means for transmitting in the processor 202 may be implemented via the at least one transceiver 208.

[0093] The receiver chain 210 may be configured to receive signals (e.g., control information, data, packets) via a wireless medium. For example, the receiver chain 210 may include one or more antennas for receiving signals over the air or via a 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 received signal and obtain the transmitted data by inverting the modulation technique applied during transmission of the signal. The receiver chain 210 may include at least one decoder for decoding the demodulated signal to receive the transmitted data.

[0094] The 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, thereby 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 such as 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 a wireless medium. The transmitter chain 212 may also include one or more antennas for transmitting the amplified signal into the air or wireless medium.

[0095] Figure 3 An example of a processor 300 according to various aspects of the present disclosure is illustrated. The processor 300 may be an example of a processor configured to perform various operations according to the examples described herein. The processor 300 may include a controller 302 configured to perform various operations according to the examples 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., a bus).

[0096] The processor 300 may be a processor chipset and include a protocol stack (e.g., a software stack) that is executed by the processor chipset to perform various operations according to the examples described herein (e.g., receiving, obtaining, retrieving, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, reading). The processor chipset may include one or more cores, one or more cache memories (e.g., memory local to or included in the processor chipset (e.g., 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)).

[0097] 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 according to the examples described herein. For example, the controller 302 may operate as a control unit for 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 operation timing.

[0098] The controller 302 may be configured to fetch (e.g., obtain, retrieve, receive) instructions from the memory 304 and determine subsequent instructions to be executed to cause the processor 300 to support various operations according to the examples described herein. The controller 302 may be configured to track the memory addresses of instructions associated with the memory 304. The controller 302 may be configured to decode the instructions to determine the operations to be performed and the operands involved. For example, the controller 302 may be configured to interpret the instructions and determine control signals to be output to other components of the processor 300 to cause the processor 300 to support various operations according to the examples described herein. Additionally or alternatively, the controller 302 may be configured to manage data flow within the processor 300. The controller 302 may be configured to control data transfers between registers, an arithmetic logic unit (ALU), and other functional units of the processor 300.

[0099] Memory 304 may include one or more cache memories (e.g., memory local to or included in processor 300 or other memory such as RAM, ROM, DRAM, SDRAM, SRAM, MRAM, flash memory, etc.). In some embodiments, memory 304 may reside within or on a processor chipset (e.g., local to processor 300). In some other embodiments, memory 304 may reside external to a processor chipset (e.g., remote from processor 300).

[0100] Memory 304 may store computer-readable, computer-executable code including instructions that, when executed by processor 300, cause processor 300 to perform the 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. Controller 302 and / or processor 300 may be configured to execute the computer-readable instructions stored in memory 304, thereby causing processor 300 to perform various functions. For example, processor 300 and / or controller 302 may be coupled together with or to memory 304, and processor 300, controller 302, and memory 304 may be configured to perform the various functions described herein. In some examples, processor 300 may include multiple processors and memory 304 may include multiple memories. One or more of the multiple processors may be coupled to one or more of the multiple memories, which may be individually or collectively configured to perform the various functions described herein.

[0101] The one or more ALUs 306 may be configured to support various operations according to the examples described herein. In some embodiments, the one or more ALUs 306 may reside within or on a processor chipset (e.g., processor 300). In some other embodiments, the one or more ALUs 306 may reside external to the processor chipset (e.g., processor 300). The one or more ALUs 306 may perform one or more operations on data, such as addition, subtraction, multiplication, and division. For example, the one or more ALUs 306 may receive input operands and an opcode, which determines the operation to be performed. The one or more ALUs 306 are configured with a variety of logic and arithmetic circuits, including adders, subtractors, shifters, and logic gates, to process and manipulate data according to the operation. Additionally or alternatively, the one or more ALUs 306 may support logical operations such as AND, OR, XOR, NOR, and NAND, enabling the one or more ALUs 306 to handle conditional operations, comparisons, and bitwise operations.

[0102] According to examples disclosed herein, processor 300 may support wireless communications.

[0103] In some embodiments, processor 300 may be configured to support Figure 6 For example, the processor 300 may be configured or operable to support: means for receiving an RRC reconfiguration message from a BS, wherein the RRC reconfiguration message includes a cell handover configuration for a set of candidate cells; means for receiving a cell handover command from the BS, wherein the cell handover command includes ID information related to a candidate cell within the set of candidate cells; and means for performing a cell handover to the candidate cell based on the cell handover command.

[0104] In some further embodiments, the processor 300 may be configured to support Figure 7 For example, the processor 300 may be configured or operable to support: a means for receiving a first timing advance (TA) value list for a set of candidate cells from a centralized unit (CU) of a BS, wherein the first TA value list includes a first TA value for a first candidate cell within the set of candidate cells; and a means for transmitting a cell handover command to a user equipment (UE), wherein the cell handover command includes identifier (ID) information related to the first candidate cell.

[0105] In some additional embodiments, processor 300 may be configured to support Figure 8 For example, the processor 300 may be configured or operable to support: means for transmitting a request for a cell switching configuration for a set of candidate cells to one or more candidate distributed units (DUs) of a BS; means for receiving a response corresponding to the request from the one or more candidate DUs, wherein the response includes the cell switching configuration for the set of candidate cells; and means for transmitting the cell switching configuration for the set of candidate cells to a user equipment (UE) via a source DU of the BS based on the response.

[0106] In yet other embodiments, the processor 300 may be configured to support Figure 9 For example, the processor 300 may be configured or operable to support: a means for receiving, from a centralized unit (CU) of a BS, a request for a cell handover configuration for a set of candidate cells for a user equipment (UE); and a means for transmitting a response to the CU based on the request, wherein the response includes a configuration related to the set of candidate cells for the UE, and wherein the set of candidate cells includes a first candidate cell.

[0107] Those skilled in the art will appreciate that the components in exemplary processor 300 may be changed, for example, some components in exemplary processor 300 may be omitted or modified, or new components may be added to exemplary processor 300, without departing from the spirit and scope of the present disclosure. For example, in some embodiments, processor 300 may not include ALU 306.

[0108] Figure 4 An example of an NE 400 according to various aspects of the present disclosure is illustrated. NE 400 may include a processor 402, a memory 404, a controller 406, and a transceiver 408. Processor 402, memory 404, controller 406, or 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.

[0109] The processor 402, memory 404, controller 406, or 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 to or otherwise support means for performing the functions described in the present disclosure.

[0110] 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 embodiments, the processor 402 may be configured to operate the memory 404. In some other embodiments, 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, thereby causing the NE 400 to perform various functions disclosed herein.

[0111] Memory 404 may include volatile or nonvolatile memory. Memory 404 may store computer-readable, computer-executable code including instructions that, when executed by processor 402, cause NE 400 to perform the various functions described herein. The code may be stored in a non-transitory computer-readable medium, such as memory 404 or another type of memory. Computer-readable media includes both non-transitory computer storage media and communication media, including any media that facilitates the transfer of computer programs from one location to another. Non-transitory storage media may be any available media that can be accessed by a general-purpose or special-purpose computer.

[0112] In some embodiments, the processor 402 and the memory 404 coupled to the processor 402 may be configured to cause the NE 400 to perform one or more of the functions described herein (e.g., execution of instructions stored in the memory 404 by the processor 402). For example, according to the examples disclosed herein, the processor 402 may support wireless communications at the NE 400. For example, the NE 400 may be configured to support instructions for performing operations related to Figures 7 to 9 The artifacts of the described operation.

[0113] In some embodiments, NE 400 may be a source DU and configured to support: a component for receiving a TA value list for a set of candidate cells from a CU of a BS, wherein the TA value list includes TA values ​​for candidate cells within the set of candidate cells; and a component for transmitting a cell switching command to a UE, wherein the cell switching command includes ID information related to the candidate cells.

[0114] In some embodiments, NE 400 may be a CU and configured to support: a component for transmitting a request for cell switching configuration for a set of candidate cells to one or more candidate DUs of a BS; a component for receiving a response corresponding to the request from the one or more candidate DUs, wherein the response includes the cell switching configuration for the set of candidate cells; and a component for transmitting the cell switching configuration for the set of candidate cells to a UE via a source DU of the BS based on the response.

[0115] In some embodiments, NE 400 may be a candidate DU and configured to support: a component for receiving a request for cell switching configuration for a set of candidate cells for a UE from a CU of a BS; and a component for transmitting a response to the CU based on the request, wherein the response includes a configuration related to the set of candidate cells for the UE, and wherein the set of candidate cells includes a first candidate cell.

[0116] The controller 406 may manage the input and output signals of the NE 400. The controller 406 may also manage peripheral devices that are not integrated into the NE 400. In some embodiments, the controller 406 may utilize, for example, In some embodiments, the controller 406 may be implemented as part of the processor 402 .

[0117] In some embodiments, NE 400 may include at least one transceiver 408. In some other embodiments, NE 400 may have more than one transceiver 408. Transceiver 408 may represent a wireless transceiver. Transceiver 408 may include one or more receiver chains 410, one or more transmitter chains 412, or a combination thereof. The aforementioned means for receiving or means for transmitting in processor 402 may be implemented via at least one transceiver 408.

[0118] The receiver chain 410 may be configured to receive signals (e.g., control information, data, packets) via a wireless medium. For example, the receiver chain 410 may include one or more antennas for receiving signals over the air or via a 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 received signal and obtain the transmitted data by inverting the modulation technique applied during transmission of the signal. The receiver chain 410 may include at least one decoder for decoding the demodulated signal to receive the transmitted data.

[0119] The 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, thereby 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 such as 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 for transmission over a wireless medium. The transmitter chain 412 may also include one or more antennas for transmitting the amplified signal into the air or wireless medium.

[0120] Those skilled in the art will appreciate that the components in exemplary NE 400 may be changed, for example, some components in exemplary NE 400 may be omitted or modified, or new components may be added to exemplary NE 400, without departing from the spirit and scope of the present disclosure. For example, in some embodiments, NE 400 may not include controller 406.

[0121] Figure 5 Schematic diagram illustrating inter-cell layer 1 / layer 2 (L1 / L2) mobility according to aspects of the present disclosure. Figure 5 As shown in , the CU can communicate with two DUs (ie, DU1 or DU2) via the F1 interface. Figure 5The CU in may implement legacy mobility decisions based on layer 3 (L3) measurement results. Figure 5 DU1 or DU2 in the L1 / L2 mobility decision can be implemented based on the physical layer measurement results.

[0122] Compared to legacy L3 mobility, L1 / L2 mobility is considered faster and has less processing delay and signaling delay. Figure 5 ) makes mobility decisions based on received Radio Resource Management (RRM) measurement reports. Unlike legacy L3 mobility, in L1 / L2 mobility, DUs (e.g. Figure 5 DU1 or DU2 shown in the figure makes mobility decisions based on physical layer measurements carried, for example, in channel state information (CSI) reports. Furthermore, in legacy L3 mobility, handover commands are sent from the SN CU to the UE via RRC messages, while in L1 / L2 mobility, "handover" commands are sent from the DU to the UE via L1 / L2 signaling (e.g., downlink control information (DCI) or media access control (MAC) control elements (CEs)). A "handover" command in L1 / L2 mobility can be about cell activation or deactivation, for example, activating a new serving PCell while deactivating an old serving PCell.

[0123] Figure 6 Flowchart illustrating a method according to various aspects of the present disclosure. The operations of the method may be implemented by a UE as described herein. In some embodiments, the UE may execute a set of instructions to control the functional elements of the UE to perform the described functions. In some embodiments, aspects of operations 602, 604, and 606 may be implemented by reference to Figure 2 Each of operations 602, 604, and 606 may be performed according to examples as described herein.

[0124] At operation 602, the method may include receiving, by the UE, an RRC reconfiguration message from a BS, and the RRC reconfiguration message includes a cell switching configuration for a set of candidate cells.

[0125] At operation 604, the method may include receiving, by the UE, a cell handover command from a base station (e.g., from a source DU of the base station). The cell handover command includes ID information associated with a candidate cell (denoted as cell #1 for simplicity) within the set of candidate cells. For example, the ID information may be a candidate cell configuration index for the candidate cell, such as an LTM configuration ID for the candidate cell.

[0126] At operation 606, the method may include performing, by the UE, a cell handover to cell #1 based on the cell handover command. That is, cell #1 is the target cell for the cell handover. In some implementations of the methods described herein, the cell handover command includes at least one of the following:

[0127] (1) Index information of the candidate cell configuration of cell #1 (e.g., LTM configuration ID cell #1);

[0128] (2) TA value of cell #1; or

[0129] (3) The timer length of the TAT associated with the TA value or cell #1.

[0130] In some implementations of the methods described herein, the UE may further perform the following operations:

[0131] (1) If the UE fails to access cell #1, e.g., timer T304 expires, the UE may initiate a re-establishment procedure; and

[0132] (2) If “information indicating a set of candidate cells available for recovery” (denoted as information #1) has been configured to the UE, the UE may maintain the relevant configuration (denoted as configuration #1); for example, information #1 may be an attempt LTM configuration information element (IE); or

[0133] (3) If information #1 is not configured to the UE, the UE may release configuration #1.

[0134] In the implementation of the method described herein, configuration #1 may include at least a configuration for SpCell, a configuration for one or more MCG SCells, an MR-DC configuration, an overheat assisted configuration, and an IDC assisted configuration. Figure 11 Specific examples are described in .

[0135] In implementations of the methods described herein, if the UE fails to access cell #1 and initiates a re-establishment procedure, the UE may further:

[0136] (1) Select another candidate cell (denoted as cell #2) for the RRC re-establishment procedure;

[0137] (2) determining whether cell #2 is a candidate cell within the set of candidate cells;

[0138] (3) if cell #2 is a candidate cell within the set of candidate cells, then applying the cell handover configuration for cell #2 and performing a cell handover to cell #2; or

[0139] (4) If cell #2 is not a candidate cell in the set of candidate cells and if information #1 has been configured to the UE, release configuration #1.

[0140] For example, configuration #1 may include at least one of the following:

[0141] (1) Reset MAC;

[0142] (2) Release the configuration for SpCell, such as spCellConfig (if configured);

[0143] (3) Suspend all RBs, BH RLC channels for IAB-MT, and Uu relay RLC channels for L2 U2N relay UEs, except SRB0 and broadcast MRBs

[0144] (4) Release the MCG SCell (if configured);

[0145] (5) Release the MR-DC configuration.

[0146] (6) Release delayBudgetReportingConfig (if configured) and stop timer T342 (if running);

[0147] (7) Release overheatingAssistanceConfig (if configured) and stop timer T345 (if running);

[0148] (8) Release idc-AssistanceConfig (if configured);

[0149] (9) Release btNameList (if configured);

[0150] (10) Release wlanNameList (if configured); or

[0151] (11) Release sensorNameList (if configured).

[0152] In some implementations of the methods described herein, if the UE switches to cell #2, the UE may further transmit an RRC reconfiguration complete message associated with cell #2 to the CU. The RRC reconfiguration complete message includes ID information related to cell #2 (e.g., cell ID, cell #2 configuration index, or LTM configuration ID of cell #2). The cell ID may be a physical cell identifier (PCI) or an NR cell global index (NCGI).

[0153] In some implementations of the methods described herein, the RRC reconfiguration message at operation 602 includes information instructing the UE to calculate a TA value for a candidate cell (denoted as information #2). Information #2 may include ID information for the candidate cell. For example, information #2 instructs the UE to calculate a TA value for cell #1 (denoted as TA #1) and / or a TA value for another candidate cell (e.g., cell #2) (denoted as TA #2). Information #2 includes ID information for cell #1 and / or cell #2.

[0154] In some implementations of the methods described herein, whether the UE calculates the TA value is determined by a CU of the BS, one or more candidate DUs of the BS, or a source DU of the BS.

[0155] In an embodiment, in response to receiving information #2 including the ID information of cell #1, the UE may further determine that TA #1 for cell #1 is not included in the cell handover command for cell #1. Specifically, the UE determines that TA #1 for cell #1 is not included in the cell handover command for cell #1 based on the fact that received information #2 includes the ID information of cell #1. The UE may then independently calculate TA #1 for cell #1.

[0156] In another embodiment, after receiving information #2 including ID information for both cell #1 and cell #2, the UE may further calculate TA #1 for cell #1 and TA #2 for cell #2. Specifically, based on the fact that received information #2 includes ID information for both cell #1 and cell #2, the UE independently calculates TA #1 for cell #1 and TA #2 for cell #2.

[0157] For example, TA#1 for cell#1 may be calculated based on:

[0158] (1) The reception timing difference between the UE's source cell and cell #1 (e.g., the RS signal reception timing difference between the two cells), and / or

[0159] (2) TA value for the source cell.

[0160] For example, TA#2 for cell#2 may be calculated based on:

[0161] (1) The reception timing difference between the UE's source cell and cell #2 (e.g., the RS signal reception timing difference between the two cells), and / or

[0162] (2) TA value for the source cell. Figure 12 Specific examples are described in .

[0163] In some implementations of the methods described herein, the UE may further:

[0164] (1) If a PDCCH command for the TA acquisition procedure for cell #1 is received:

[0165] a) Abandon TA#1 for cell#1; or

[0166] b) maintain TA#1 for cell #1 until another TA value (denoted as TA#3) for cell #1 is received from the source DU of the BS, and discard TA#1 for cell #1 after receiving TA#3 from the source DU; or

[0167] (2) If the cell handover command includes TA#3, TA#1 for cell#1 is discarded and cell handover to cell#1 is performed using TA#3.

[0168] In some embodiments of the methods described herein, after the UE switches to cell #1, the UE may further release or store TA #2 for cell #2. In an embodiment, in response to storing TA #2 for cell #2, the UE may further determine whether TA #2 is valid based on the TAT associated with TA #2.

[0169] In some implementations of the methods described herein, after the UE switches to cell #1, the UE may further release or store TA #1 for cell #1.

[0170] In an embodiment, in response to storing TA#1 for cell#1, the UE may further report TA#1 to the candidate DU associated with cell#1 via an RRC message or MAC CE. In this embodiment, the UE may further receive an incremental value for updating TA#1 from the candidate DU associated with cell#1. For example, the UE updates TA#1 for cell#1 by applying the received incremental value to TA#1.

[0171] In another embodiment, in response to storing TA#1 for cell#1, the UE may further: receive an absolute TA value for cell#1 from a candidate DU associated with cell#1; release TA#1 for cell#1; and store the absolute TA value for cell#1. For example, the UE uses the received absolute TA value as the current TA value for cell#1 and releases TA#1 for cell#1.

[0172] In some implementations, the UE may continue to update TA#1 for cell #1 before receiving an incremental value or an absolute TA value from a candidate DU associated with cell #1. For example, the UE continues to independently update and / or calculate TA#1 for cell #1 before receiving an incremental value or an absolute TA value for updating.

[0173] In an implementation scheme, in order to continue updating TA#1, the UE may further: store the TA value of the UE's source cell; receive a timer length of a TAT (denoted as TAT#1) associated with the TA value of the source cell; continue to update TA#1 based on the TA value of the source cell before TAT#1 expires; and immediately consider TA#1 invalid after TAT#1 expires.

[0174] In some embodiments of the methods described herein, in response to considering TA#1 as invalid, the UE may further trigger a RACH procedure for UL synchronization. Figure 12 Specific examples are described in .

[0175] It should be noted that Figure 6 The methods described in the foregoing describe possible implementations, and operations and steps may be rearranged or otherwise eliminated or modified and other implementations are possible without departing from the spirit and scope of the present disclosure.

[0176] Figure 7 Flowchart illustrating a method according to various aspects of the present disclosure. As described herein, the operations of the method may be implemented by a source DU of a BS (e.g., a source DU of a NE). In some embodiments, the source DU may execute a set of instructions to control functional elements of the source DU to perform the described functions. In some embodiments, aspects of operations 702 and 704 may be implemented by reference to Figure 4 Each of operations 702 and 704 may be performed according to examples as described herein.

[0177] At operation 702, the method may include receiving, by a source DU of a BS from a CU of the BS, a list of TA values ​​for a set of candidate cells. The TA value list (denoted as list #1) refers to one or more TA values ​​or a set of TA values. List #1 may include TA values ​​for candidate cells within the set of candidate cells (e.g., Figure 6 In some embodiments, list #1 further includes another TA value for another candidate cell within the set of candidate cells (e.g., in Figure 6 TA#2 for cell #2 as described or illustrated in the method in ).

[0178] At operation 704, the method may include transmitting, by the source DU, a cell handover command to the UE. For example, the cell handover command includes ID information associated with cell #1 (i.e., the target candidate cell). In some implementations, the cell handover command includes at least one of (1) TA #1 for cell #1 or (2) a TAT associated with TA #1.

[0179] In some implementations of the methods described herein, after transmitting the cell switching command, the source DU may further transmit, via the CU, at least one of the following to the candidate DU of the BS associated with cell #1 (i.e., the target candidate cell):

[0180] (1) Another TA value list (denoted as List #2), which refers to one or more TA values ​​or a group of TA values. In one embodiment, List #2 includes all TA values ​​in List #1. In another embodiment, List #2 includes all TA values ​​in List #1 except TA #1 for cell #1 included in the cell handover command.

[0181] (2) Additional information associated with List #2 that can be used to determine whether List #2 is invalid. In an embodiment, the additional information associated with the TA value in List #2 includes at least one of the following:

[0182] (1) The absolute time (e.g., timestamp) when the TA value is received;

[0183] (2) The time that has passed since the TA value was received; or

[0184] (3) The remaining effective period of the TA value.

[0185] In some implementations of the methods described herein, the source DU may further transmit List #2 and / or additional information associated with List #2 to the CU. Figure 10 and 11 Specific examples are described in .

[0186] It should be noted that Figure 7 The methods described in the foregoing describe possible implementations, and operations and steps may be rearranged or otherwise eliminated or modified and other implementations are possible without departing from the spirit and scope of the present disclosure.

[0187] Figure 8 Flowchart illustrating a method according to various aspects of the present disclosure. As described herein, the operations of the method may be implemented by a CU of a BS (e.g., a CU of a NE). In some embodiments, the CU may execute a set of instructions to control the functional elements of the CU to perform the described functions. In some embodiments, aspects of operations 802, 804, and 806 may be described with reference to FIG. Figure 5 Each of operations 802, 804, and 806 may be performed according to examples as described herein.

[0188] At operation 802, the method may include transmitting, by a CU of a BS to one or more candidate DUs of the BS, a request for a cell switching configuration for a set of candidate cells.

[0189] At operation 804, the method may include receiving, by the CU, a response corresponding to the request from one or more candidate DUs. The response includes a cell switching configuration for the set of candidate cells (e.g., an LTM configuration associated with the set of candidate cells). The one or more candidate DUs may be in an inter-DU scenario or an intra-DU scenario.

[0190] At operation 806, the method may include transmitting, via a source DU of the BS, a cell switching configuration for the set of candidate cells to the UE based on the response.

[0191] In some implementations of the methods described herein, after the UE fails to switch to a candidate cell, the CU may further receive from the UE an RRC reconfiguration complete message associated with another candidate cell within the set of candidate cells (i.e., the target cell to which the UE switches). Figure 6 In the method described or illustrated in , after the UE fails to switch to cell #1, the CU may receive an RRC reconfiguration complete message associated with cell #2 from the UE. The RRC reconfiguration complete message may include ID information related to cell #2.

[0192] In some implementations of the methods described herein, after receiving the RRC reconfiguration complete message, the CU may further transmit at least one of the following to the candidate DU associated with cell #2:

[0193] (1) TA value list (denoted as list #3), which refers to one or more TA values ​​or a group of TA values. In an embodiment, list #3 contains a list of TA values ​​for all candidate cells configured with TA acquisition (e.g., Figure 6 In another embodiment, list #3 includes all TA values ​​in list #1 except the TA value for the target cell included in the RRC reconfiguration complete message (e.g., TA #2 for cell #2).

[0194] (2) Additional information associated with List #3 that can be used to determine whether List #3 is invalid. In an embodiment, the additional information associated with the TA value within List #3 includes at least one of: the absolute time when the TA value was received; the time that has elapsed since the TA value was received; or the remaining validity period of the TA value.

[0195] In some embodiments of the methods described herein, when a source DU transmits a message containing information related to a candidate cell (e.g., Figure 6After the cell handover command is executed with the ID information of the cell #1) described or illustrated in the method in, the CU may receive at least one of the following from the source DU:

[0196] (1) TA value list (for example, in Figure 6 as described or illustrated in the method in Listing #2); or

[0197] (2) Additional information associated with list #2 that can be used to determine whether list #2 is invalid. In an embodiment, the additional information associated with the TA value in list #2 includes at least one of the following: the absolute time when the TA value was received; the time that has elapsed since the TA value was received; or the remaining validity period of the TA value.

[0198] In some implementations of the methods described herein, the CU may further transmit List #2 and / or additional information associated with List #2 to the candidate DU of the BS associated with the target cell (e.g., Cell #2). Figure 10 and 11 Specific examples are described in .

[0199] In some implementations of the methods described herein, the request for cell handover configuration at operation 802 includes information (denoted as information #3) indicating that the UE is to calculate a TA value for the candidate cell.

[0200] In some implementations of the methods described herein, the CU may further receive at least one of the following from the one or more candidate DUs (e.g., in a response at operation 804):

[0201] (1) Information instructing the UE to calculate one or more TA values ​​for the set of candidate cells (denoted as information #4). The information may be included in the cell handover configuration sent to the UE.

[0202] (2) Reference signal (RS) configuration information configured for the UE. Figure 12 Specific examples are described in .

[0203] It should be noted that Figure 8 The methods described in the foregoing describe possible implementations, and operations and steps may be rearranged or otherwise eliminated or modified and other implementations are possible without departing from the spirit and scope of the present disclosure.

[0204] Figure 9Flowchart illustrating a method according to various aspects of the present disclosure. As described herein, the operations of the method may be implemented by a candidate DU of a BS (e.g., a candidate DU of a NE). In some embodiments, the NE may execute a set of instructions to control functional elements of the NE to perform the described functions. In some embodiments, aspects of operations 902 and 904 may be implemented by reference to Figure 4 Each of operations 902 and 904 may be performed according to examples as described herein.

[0205] At operation 902, the method may include receiving, by a candidate DU of a BS from a CU of the BS, a request for a cell switching configuration for a set of candidate cells for a UE.

[0206] At operation 904, the method may include transmitting, by the candidate DU, a response to the CU based on the request. The response includes a configuration related to a set of candidate cells for the UE, and the set of candidate cells includes candidate cells (e.g., Figure 6 Cell #1 or Cell #2 described or illustrated in the method).

[0207] In some implementations of the methods described herein, the candidate DU may receive at least one of the following from the CU:

[0208] (1) A list of TA values ​​for the set of candidate cells.

[0209] (2) A list of TA values ​​other than the TA values ​​for the candidate cells (eg, cell #1 or cell #2 to which the UE is configured to handover).

[0210] (3) Additional information associated with the TA value list that can be used to determine whether a TA value within the TA value list is invalid. In an embodiment, the additional information associated with the TA value within the TA value list includes at least one of the following: (1) an absolute time when the TA value is received; (2) a time that has elapsed since the TA value was received; or (3) a remaining validity period of the TA value.

[0211] For example, in the case where the CU is responsible for maintaining or storing the TA value (e.g., after receiving the TA value from the source DU or candidate DU) and the source DU transmits a cell handover command to cell #1, the candidate DU may receive a TA value (denoted as list #4) from the CU. In an embodiment, list #4 includes a list of TA values ​​for all candidate cells (e.g., in Figure 6 In another embodiment, list #4 includes all TA values ​​in list #1 except the TA value for cell #1 included in the cell handover command.

[0212] For example, in the case where the CU receives an RRC reconfiguration complete message from the UE after the UE switches to cell #2, the candidate DU may receive an RRC reconfiguration complete message from the CU. Figure 8 In an embodiment, List #3 comprises a list of TA values ​​for all candidate cells (e.g., Figure 6 In another embodiment, list #3 includes all TA values ​​in list #1 except the TA value for the target cell included in the RRC reconfiguration complete message (e.g., TA #2 for cell #2).

[0213] In some implementations of the methods described herein, the candidate DU may transmit at least one of: (1) information instructing the UE to calculate one or more TA values ​​for the set of candidate cells, or (2) RS configuration information configured to the UE. Figure 8 In the method described or illustrated in , the candidate DU may transmit information #4 configured for the UE and / or RS configuration information to the CU.

[0214] In some implementations, the candidate DU may further determine whether the UE will calculate one or more TA values.

[0215] In some implementations, the candidate DU may further receive a TA value for cell #1 from the UE via the CU, and the UE is configured to switch to cell #1. In one implementation, the candidate DU may transmit an incremental value to the UE via the CU for updating the TA value for cell #1. For example, the UE may update the TA value for cell #1 by applying the received incremental value.

[0216] In some implementations, the candidate DU may further transmit an absolute TA value for cell #1 to the UE via the CU. For example, the UE may use the received absolute TA value as the current TA value for cell #1 and release its stored TA value for cell #1. Figure 12 Specific examples are described in .

[0217] It should be noted that Figure 9 The methods described in the foregoing describe possible implementations, and operations and steps may be rearranged or otherwise eliminated or modified and other implementations are possible without departing from the spirit and scope of the present disclosure.

[0218] Figure 10 The diagram illustrates an example of performing a cell handover according to various aspects of the present disclosure. The details described in all other embodiments of the present disclosure apply to Figure 10 The embodiments shown in .

[0219] like Figure 10 As shown in FIG, BS 1005 adopts a CU-DU architecture and includes CU 1004, source DU 1002 and candidate DU 1003. Figure 10 In the embodiment of the present invention, the cell handover operation performed by the UE 1001 may refer to an intra-DU situation in which the source cell and the target cell are located in the same DU, or may refer to an inter-DU situation in which the source cell and the target cell are located in different DUs. For example, for exemplary purposes, Figure 10 The flowchart 1000 shown in FIG. 1 only shows the cell switching operation in the inter-DU scenario. If the source DU 1002 and the candidate DU 1003 are the same DU, the flowchart 1000 can also be applied to the intra-DU scenario.

[0220] In such Figure 10 In the exemplary flowchart 1000 shown in FIG. 1 , in operation 1011, UE 1001 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 1005). The serving BS may include a CU (e.g., a gNB-CU) and one or more DUs (e.g., a gNB-DU). The serving cell is associated with the CU and the DU. An F1 interface exists between the DU and the CU. For example, Figure 10 As shown in FIG, BS 1005 includes CU 1004, source DU 1002, and candidate DU 1003. BS 1005 may include one or more other candidate DUs ( Figure 10 In some implementations, the UE 1001 may send a measurement report to the CU 1004 via the source DU 1002.

[0221] In operation 1012 , the CU 1004 may determine to initiate an L1 / L2-based inter-cell mobility configuration procedure, that is, make an L1 / L2-based inter-cell mobility configuration decision.

[0222] In operation 1013, CU 1004 may send a request message containing candidate cell ID information to candidate DU 1003 via the F1 interface. In the inter-DU scenario, the request message may be a UE context setup request message. In the intra-DU scenario, the request message may be a UE context modification request message.

[0223] In operation 1014, if candidate DU 1003 decides to accept the request for LTM configuration related to the candidate cell, candidate DU 1003 may transmit a response message to CU 1004 via the F1 interface. The response message includes the RRC configuration for the accepted target candidate cell. In the inter-DU scenario, the response message may be a UE context setup response message. In the intra-DU scenario, the response message may be a UE context modification response message.

[0224] In some embodiments, the response message may include a lower layer RRC configuration for the candidate cell, which is referred to as "lower layer RRC configuration for LTM," "L1 / L2 RRC configuration information for LTM," "RRC configuration for LTM," "LTM configuration information," etc. In some embodiments, RACH resources for early TA acquisition may be included in the response message transmitted to CU 1004. The candidate cell may be referred to as "candidate cell for LTM," etc.

[0225] In operation 1015, the CU 1004 transmits the configuration to the source DU 1002. In some implementations, the CU 1004 may transmit the configuration, such as RACH resources for early TA acquisition, to the source DU. The CU 1004 may further indicate whether early TA acquisition should be triggered.

[0226] In some implementations, the CU 1004 may generate an RRC reconfiguration message based on the configuration from the candidate cell and transmit the RRC reconfiguration message to the source DU 1002. For example, the RRC reconfiguration message includes the candidate cell configuration for LTM and / or RACH resources for early TA acquisition.

[0227] In operation 1016 , the UE 1001 may receive an RRC reconfiguration message associated with one or more candidate cells configured for LTM from the source DU 1002 .

[0228] In operation 1017 , the UE 1001 may receive a PDCCH command for triggering TA acquisition for a specific candidate cell (eg, a candidate cell associated with the candidate DU 1003 ).

[0229] In operation 1018, UE 1001 may transmit a preamble for TA acquisition to candidate DU 1003. In some implementations, if candidate DU 1003 can calculate a TA value for a particular candidate cell based on the received preamble, candidate DU 1003 may transmit the preamble and corresponding RACH opportunity, beam indication, UE 1001 ID, RA-RNTI, ID information of the candidate cell ID (i.e., target cell ID), TCI state index of the candidate cell, or similar information, and / or the calculated TA value to source DU 1002 via CU 1004. In some implementations, candidate DU 1003 may store the calculated TA value. In operation 1018, after CU 1004 receives the information from candidate DU 1003, it transmits the information, such as the calculated TA value, to source DU 1002 via the F1 interface.

[0230] In operation 1019, the source DU 1002 may transmit a cell switching command for the candidate cell to the UE 1001. The candidate cell may also be referred to as a "target candidate cell" or the like. For example, the candidate cell is associated with the candidate DU 1003 (e.g., in Figure 6 In some implementations, in operation 1019, the source DU 1002 transmits an indication to the CU 1004 to perform a cell handover to the candidate cell. In some implementations, the cell handover command includes at least one of: (1) a candidate cell configuration index of the candidate cell; (2) a TA value for the candidate cell; or (3) a timer length for a TAT associated with the TA value.

[0231] In some implementations, the cell switching command includes at least one of: a candidate cell configuration index of the candidate cell; a TA value for the candidate cell; or a timer length for a TAT associated with the TA value. In some embodiments, after receiving the cell switching command including the TA value or the timer length for the TAT for the candidate cell, the UE 1001 may continue to maintain the received TA value and / or the timer length for the TAT for the candidate cell.

[0232] In operation 1020 , in response to receiving the cell switching command, the UE 1001 performs cell switching to a corresponding candidate cell (eg, cell # 1 ) of the candidate DU 1003 .

[0233] In operation 1020, the candidate DU 1003 (ie, target DU) may receive information including at least one of the following from the CU 1004:

[0234] (1) A cell switching instruction, for example, includes ID information of a corresponding candidate cell (for example, cell #1).

[0235] (2) TA value list, for example Figure 8 In an embodiment, List #3 comprises a list of TA values ​​for all candidate cells (e.g., Figure 6 In another embodiment, list #3 includes all TA values ​​in list #1 except the TA value for cell #1.

[0236] (3) Additional information associated with the TA value list, which can be used to determine whether a TA value in the TA value list is invalid.

[0237] There may be three options in different embodiments of operation 1020, namely option #1, option #2, or option #3, as shown below.

[0238] (1) Option #1: The source DU 1002 needs to forward the stored TA value (e.g., a TA value list) and / or additional information that can be used to determine whether the TA value is invalid. For example, the additional information associated with the TA value may include at least one of the following: (1) the absolute time when the TA value was received (e.g., a timestamp), (2) the time that has elapsed since the TA value was received, or (3) the remaining validity period of the TA value. The remaining validity period of the TA value is the difference between the timer length of the TAT and the time that has elapsed since the TA value was received.

[0239] In an embodiment, the source DU 1002 forwards all stored TA values ​​and related additional information to the candidate DU 1003 via the CU 1004. In other words, the source DU 1002 forwards the TA values ​​and / or related additional information related to all candidate cells including the target cell to the candidate DU 1003.

[0240] In another embodiment, the source DU 1002 forwards all stored TA values ​​and / or related additional information except the TA value of the candidate cell (i.e., the target cell) associated with the candidate DU 1003 to the candidate DU 1003 (i.e., the target DU) via the CU 1004. In other words, the source DU 1002 forwards the TA values ​​and / or related additional information associated with all candidate cells except the target cell to the candidate DU 1003.

[0241] (2) Option #2: The CU 1004 may be responsible for maintaining or storing the TA value, for example, in the case where the CU 1004 stores the TA value after receiving it from the source DU 1002. In this embodiment, the CU 1004 may provide a list of TA values ​​to the candidate DU 1003 (i.e., the target DU) (e.g., in Figure 9 4) and / or additional information that may be used to determine whether a TA value in the TA value list is invalid. For example, the additional information associated with a TA value within the TA value list may include at least one of the following: an absolute time (e.g., a timestamp) at which the TA value was received, a time elapsed since the TA value was received, or a remaining validity period of the TA value.

[0242] (3) Option #3: CU 1004 may not be responsible for maintaining or storing TA values. In this embodiment, CU 1004 may transmit a request to source DU 1002 to inquire about the TA value and / or additional information that may be used to determine whether the TA value is invalid. CU 1004 may then transmit a list of TA values ​​received from source DU 1002 to candidate DU 1003 (i.e., target DU) (e.g., in Figure 7) and / or related additional information. For example, the additional information associated with the TA value in the TA value list may include at least one of the following: (1) an absolute time (e.g., a timestamp) at which the TA value was received, (2) a time elapsed since the TA value was received, or (3) a remaining validity period of the TA value.

[0243] Figure 11 The diagram illustrates another example of performing a cell handover according to various aspects of the present disclosure. The details described in all other embodiments of the present disclosure apply to Figure 11 The embodiments shown in .

[0244] like Figure 11 As shown in FIG, BS 1105 adopts a CU-DU architecture and includes a CU 1104, a source DU 1102, and a candidate DU 1103. Figure 11 In the embodiment of the present invention, the cell handover operation performed by the UE 1101 may refer to an intra-DU situation in which the source cell and the target cell are located in the same DU, or may refer to an inter-DU situation in which the source cell and the target cell are located in different DUs. For example, for exemplary purposes, Figure 11 The flowchart 1110 shown in FIG. 1 only shows the cell switching operation in the inter-DU scenario. If the source DU 1102 and the candidate DU 1103 are the same DU, the flowchart 1110 can also be applied to the intra-DU scenario.

[0245] In such Figure 11 In the exemplary flowchart 1110 shown in FIG. 1 , in operation 1111, UE 1101 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 1105). The serving BS may include a CU (e.g., a gNB-CU) and one or more DUs (e.g., a gNB-DU). The serving cell is associated with the CU and the DU. An F1 interface exists between the DU and the CU. For example, Figure 11 , BS 1105 includes CU 1104, source DU 1102, and candidate DU 1103. BS 1105 may include one or more other candidate DUs (e.g., Figure 11 In some implementations, UE 1101 may send a measurement report to CU 1104 via source DU 1102.

[0246] In operation 1112 , the CU 1104 may determine to initiate an L1 / L2-based inter-cell mobility configuration procedure, ie, make an L1 / L2-based inter-cell mobility configuration decision.

[0247] In operation 1113, CU 1104 may send a request message containing candidate cell ID information to candidate DU 1103 via the F1 interface. In the inter-DU scenario, the request message may be a UE context setup request message. In the intra-DU scenario, the request message may be a UE context modification request message.

[0248] In operation 1114, if candidate DU 1103 decides to accept the request for LTM configuration related to the candidate cell, candidate DU 1103 may transmit a response message to CU 1104 via the F1 interface. The response message includes the RRC configuration for the accepted target candidate cell. In the inter-DU scenario, the response message may be a UE context setup response message. In the intra-DU scenario, the response message may be a UE context modification response message.

[0249] In some embodiments, the response message may include a lower layer RRC configuration for the candidate cell, which is referred to as "lower layer RRC configuration for LTM," "L1 / L2 RRC configuration information for LTM," "RRC configuration for LTM," "LTM configuration information," etc. In some embodiments, RACH resources for early TA acquisition may be included in the response message transmitted to CU1104. The candidate cell may be referred to as "candidate cell for LTM," etc.

[0250] In operation 1115, CU 1104 transmits the received configuration to source DU 1102. In some implementations, CU 1104 may transmit the received configuration, such as RACH resources for early TA acquisition, to source DU 1102. CU 1104 may further indicate to source DU 1102 whether early TA acquisition should be triggered.

[0251] In some implementations, CU 1104 may generate an RRC reconfiguration message based on the configuration received from candidate DU 1106 and transmit the RRC reconfiguration message to source DU 1102. For example, the RRC reconfiguration message includes candidate cell configuration for LTM and / or RACH resources for early TA acquisition.

[0252] In operation 1116 , the UE 1101 may receive an RRC reconfiguration message associated with one or more candidate cells configured for LTM (ie, candidate cells for LTM) from the source DU 1102 .

[0253] In operation 1117 , the UE 1101 may receive a PDCCH command for triggering TA acquisition of a specific candidate cell (eg, a candidate cell associated with the candidate DU 1103 ).

[0254] In operation 1118, UE 1101 may transmit a preamble for TA acquisition to candidate DU 1103. In some implementations, if candidate DU 1103 can calculate a TA value for a candidate cell based on the received preamble, candidate DU 1103 may transmit the preamble and corresponding RACH opportunity, beam indication, UE 1101 ID, RA-RNTI, ID information of the candidate cell (i.e., target cell ID), TCI state index of the candidate cell, or similar information to source DU 1102 via CU 1104. In some implementations, candidate DU 1103 may store the calculated TA value. In operation 1118, after CU 1104 receives the information from candidate DU 1103, it transmits the received information, such as one or more TA values, to source DU 1102 via the F1 interface.

[0255] In operation 1119, the source DU 1102 transmits a cell switching command for a candidate cell (ie, a target candidate cell) to the UE 1101. For example, the candidate cell is associated with the candidate DU 1003 (eg, Figure 6 In some implementations, in operation 1119, the source DU 1102 may transmit an indication of a cell handover to the candidate cell to the CU 1104. In some implementations, the cell handover command includes at least one of: (1) a candidate cell configuration index of the candidate cell; (2) a TA value for the candidate cell; or (3) a timer length for a TAT associated with the TA value.

[0256] In operation 1119, there may be the following two situations in different embodiments:

[0257] (1) Scenario #1: UE 1101 receives a cell handover command. In operation 1120 (which is optional and marked with a dashed line), in response to receiving the cell handover command, UE 1101 performs a cell handover to the corresponding candidate cell of candidate DU 1103 (i.e., target DU). In some implementations, UE 1101 starts the LTM timer immediately after receiving the cell handover command. In operation 1120, candidate DU 1103 (i.e., target DU) may receive information from CU 1104, the information including a cell handover indication, ID information of the corresponding candidate cell, a TA value list, and / or related additional information.

[0258] (2) Scenario #2: Radio Link Failure (RLF) occurs on the source DU 1102 before the UE 1101 receives the cell handover command (operation 1119 is therefore marked as a dashed line).

[0259] In operation 1121 , once the LTM timer expires in case #1 or RLF occurs on the source DU 1102 before the UE 1101 receives a cell handover command in case #2, the UE 1101 may initiate a re-establishment procedure.

[0260] In operation 1121, if the "indication indicating that the LTM candidate cell is available for recovery" (for example, in Figure 6 If the information #1 described or illustrated in the method in FIG. 1 , e.g., the Try LTM Configuration IE) is not configured for UE 1101, UE 1101 may release the relevant configuration (e.g., in Figure 6 Otherwise, if the "indication indicating that the LTM candidate cell is available for recovery" is configured for UE 1101, UE 1101 may maintain the relevant configuration. For example, the relevant configuration (e.g., configuration #1) may include at least one of the following:

[0261] (1) Reset MAC;

[0262] (2) Release the configuration for SpCell, such as spCellConfig (if configured);

[0263] (3) Suspend all RBs, BH RLC channels for IAB-MT, and Uu relay RLC channels for L2 U2N relay UEs, except for SRB0 and broadcast MRB;

[0264] (4) Release the MCG SCell (if configured);

[0265] (5) Release MR-DC configuration;

[0266] (6) Release delayBudgetReportingConfig (if configured) and stop timer T342 (if running);

[0267] (7) Release overheatingAssistanceConfig (if configured) and stop timer T345 (if running);

[0268] (8) Release idc-AssistanceConfig (if configured);

[0269] (9) Release btNameList (if configured);

[0270] (10) Release wlanNameList (if configured); or

[0271] (11) Release sensorNameList (if configured).

[0272] For example, in operation 1121, once the UE 1101 selects a suitable cell (e.g., the cell of the candidate DU 1106), if the “indication indicating that the LTM candidate cell is available for recovery” has been configured for the UE 1101 and the selected cell is one of the candidate cells for LTM, the UE 1101 may apply the LTM configuration to the selected candidate cell. If the “indication indicating that the LTM candidate cell is available for recovery” has not been configured for the UE 1101 or the selected cell is not one of the candidate cells for LTM, the UE 1101 may release the configuration (e.g., configuration #1).

[0273] In operation 1122 , the UE 1101 accesses the selected cell (eg, the cell of the candidate DU 1106 ) via the stored TA value or RACH resource.

[0274] In operation 1123, UE 1101 transmits an RRC reconfiguration complete message to the selected cell (via CU 1104). The ID information of the cell handover configuration related to the candidate cell (e.g., the candidate cell configuration index or LTM configuration ID for the candidate cell) should be added to the RRC reconfiguration complete message. For example, the RRC reconfiguration complete message includes the following:

[0275]

[0276] After operation 1123 , there may be two options, Option #A and Option #B, in different embodiments.

[0277] (1) Option #A: In operation 1124, once CU 1104 receives the RRC reconfiguration complete message, CU 1104 may transmit the TA value list and additional information associated with the TA value list to the new serving DU (e.g., candidate DU 1106). In addition, CU 1104 may indicate candidate DU 1103 related to the candidate cell indicated in the cell handover command for UE 1101 to access another cell (i.e., the selected cell of candidate DU 1106).

[0278] (2) Option #B: Once CU 1104 receives the RRC reconfiguration complete message, CU 1104 may request source DU 1102 to provide a TA value list upon receiving the RRC reconfiguration complete message from UE 1101 or receiving the corresponding F1AP message including the cell handover from source DU 1102. Then, in operation 1124, CU 1104 may forward the TA value list and the additional information associated with the TA value list (received from source DU 1102) to candidate DU 1106.

[0279] Figure 12 The diagram illustrates an example of TA calculation according to various aspects of the present disclosure. The details described in all other embodiments of the present disclosure apply to Figure 12 The embodiments shown in .

[0280] like Figure 12 As shown in FIG, BS 1205 adopts a CU-DU architecture and includes CU 1204, source DU 1202 and candidate DU 1203. Figure 12 In the embodiment of the present invention, the cell handover operation performed by the UE 1201 may refer to an intra-DU situation in which the source cell and the target cell are located in the same DU, or may refer to an inter-DU situation in which the source cell and the target cell are located in different DUs. For example, for exemplary purposes, Figure 12 The flowchart 1200 shown in FIG. 1 only shows the cell switching operation in the inter-DU scenario. If the source DU 1202 and the candidate DU 1203 are the same DU, the flowchart 1200 can also be applied to the intra-DU scenario.

[0281] In such Figure 12 In the exemplary flowchart 1200 shown in FIG. 1 , in operation 1211, UE 1201 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 1205). The serving BS may include a CU (e.g., a gNB-CU) and one or more DUs (e.g., a gNB-DU). The serving cell is associated with the CU and the DU. An F1 interface exists between the DU and the CU. For example, Figure 12 , BS 1205 includes CU 1204, source DU 1202, and candidate DU 1203. BS 1205 may include one or more other candidate DUs ( Figure 12 In some implementations, UE 1201 may send a measurement report to CU 1204 via source DU 1202.

[0282] In operation 1212 , the CU 1204 may determine to initiate an L1 / L2-based inter-cell mobility configuration procedure, that is, make an L1 / L2-based inter-cell mobility configuration decision.

[0283] In operation 1213, CU 1204 may send a request message containing candidate cell ID information to candidate DU 1203 via the F1 interface. In the inter-DU scenario, the request message may be a UE context setup request message. In the intra-DU scenario, the request message may be a UE context modification request message.

[0284] In some embodiments, the request message in operation 1213 may optionally include an indication (e.g., as in Figure 8 The indication includes information #3 described or illustrated in the method of FIG. 1 ), indicating that UE 1201 is to calculate a TA value for a candidate cell. This indication may be referred to as an "instruction to perform UE-based TA measurement on the candidate cell," or the like. UE-based TA measurement means that the UE independently calculates or computes a TA value based on, for example, the Rx timing difference between the UE's current serving cell and the candidate cell and the TA value for the UE's current serving cell.

[0285] In operation 1214, if candidate DU 1203 decides to accept the request for LTM configuration related to the candidate cell, candidate DU 1203 may transmit a response message to CU 1204 via the F1 interface. The response message includes the RRC configuration for the accepted target candidate cell. In the inter-DU scenario, the response message may be a UE context setup response message. In the intra-DU scenario, the response message may be a UE context modification response message.

[0286] In some embodiments, the response message may include lower layer RRC configuration for the candidate cell, which is referred to as "lower layer RRC configuration for LTM," "L1 / L2 RRC configuration information for LTM," "RRC configuration for LTM," "LTM configuration information," "candidate cell configuration for LTM," etc. In some embodiments, RACH resources for early TA acquisition may be included in the response message transmitted to the CU 1204. The candidate cell may be referred to as "candidate cell for LTM," etc.

[0287] In some implementations, the candidate DU 1203 may configure UE-based TA measurements for the candidate cell. For example, the response message may include an indication (e.g., as in Figure 8 The response message may further include information #4 described or illustrated in the method of FIG. 4 ) to instruct UE 1201 to perform UE-based TA measurement on the candidate cell. In addition, the response message may also include the corresponding RS configuration configured for UE 1201. The RS configuration is external to the lower layer RRC configuration for the candidate cell (i.e., the candidate cell configuration for LTM).

[0288] In operation 1215, the CU 1204 transmits the received configuration to the source DU 1202. In some implementations, the CU 1204 may transmit RACH resources and / or corresponding RS configuration for early TA acquisition to the source DU 1202. The CU 1204 may also transmit information indicating whether early TA acquisition should be triggered.

[0289] In some implementations, the CU 1204 may generate an RRC reconfiguration message based on the configuration from the candidate cells and transmit the RRC reconfiguration message to the source DU 1202. For example, the RRC reconfiguration message includes the candidate cell configuration for LTM and / or RACH resources for early TA acquisition.

[0290] In operation 1216, UE 1201 may receive an RRC reconfiguration message associated with candidate cells configured for LTM from source DU 1202. In the RRC reconfiguration message, it may be configured for which cell UE 1201 should calculate the TA value. For example, UE 1201 is configured to perform UE-based TA measurements for cell #1 and cell #2, as shown in FIG. Figure 6 In the case where the serving cell of UE 1201 and the candidate cell are not synchronized, the system frame number (SFN) offset between the serving cell and the candidate cell may be included in the RRC reconfiguration message of UE 1201.

[0291] In some implementations, if the CU 1204 determines whether the UE 1201 is to calculate a TA value for a candidate cell, an indication to perform UE-based TA measurements on the candidate cell may be configured via an RRC reconfiguration message to the UE 1201 (e.g., as in Figure 6 Information described or illustrated in the methods in #2).

[0292] In operation 1217, UE 1201 calculates TA values ​​for one or more candidate cells (e.g., for both cell #1 and cell #2). After UE 1201 successfully calculates the TA value via UE-based TA measurement, UE 1201 may transmit an indication of successful calculation to the serving cell of UE 1201 or report the calculated TA value.

[0293] In operation 1218, source DU 1202 transmits a cell handover command to UE 1201, the cell handover command including a candidate cell configuration index of a candidate cell (e.g., a target candidate cell associated with candidate DU 1203). In different embodiments, there may be two options, Option #M or Option #N, as shown below.

[0294] (1) Option #M: If UE-based TA measurement for candidate cells is configured for UE 1201 and if a cell handover command is received for a target candidate cell (e.g., cell #1), UE 1201 expects that the TA value for the target candidate cell (i.e., cell #1) will not be included in the cell handover command.

[0295] (2) Option #N: UE 1201 calculates the TA value for cell #1 based on the configuration for UE-based TA measurement (e.g., as in Figure 6 After TA#1) as described or illustrated in the method in:

[0296] a) If UE 1201 receives a PDCCH command for early TA acquisition for the same cell #1, UE 1201 may, for example, receive another TA value for cell #1 from the source DU (e.g., as in Figure 6 TA#3) and then discard the calculated TA value for cell #1.

[0297] b) If UE 1201 receives a cell handover command that includes a TA value for cell #1 (e.g., TA #3), UE 1201 may discard the calculated TA value for cell #1. The TA value for cell #1 (i.e., TA #3) included in the cell handover command will be used for cell handover.

[0298] In operation 1219 , the UE 1201 performs cell switching to the corresponding target candidate cell of the candidate DU 1203 after receiving the cell switching command from the source DU 1202 .

[0299] In operation 1220 , the UE 1201 may perform at least one of the following operations in different implementations.

[0300] Regarding the calculated TA value for the target candidate cell (eg, cell #1), there may be two options in different embodiments, Option #V or Option #W, as shown below.

[0301] (1) Option #V: UE 1201 may release the calculated TA value for cell #1.

[0302] (2) Option #W: After UE 1201 performs cell handover using the TA value for cell #1 calculated through UE-based TA measurement, UE 1201 may store the calculated TA value for cell #1 (ie, target cell).

[0303] In option #W, if UE 1201 stores the calculated TA value for cell #1, UE 1201 may need to report the stored TA value to the network node. The network node may then configure an incremental value on top of the stored TA value to update the TA value for cell #1. The incremental value may be included in a MAC CE. If UE 1201 is not expected to report the stored TA to the network node, the network node may configure an absolute TA value for UE 1201. Once UE 1201 receives the absolute TA value, UE 1201 may use the absolute TA value as the current TA value for cell #1 instead of the calculated TA value. The MAC CE may be used to notify UE 1201 of the absolute TA value. For example, the absolute TA value may be included in an Absolute Timing Advance Command MAC CE (e.g., an Absolute Timing Advance Command MAC CE).

[0304] Before receiving the update information of the TA value (e.g., incremental value or absolute TA value) from the target cell (i.e., cell #1), the UE 1201 itself may continue to update the TA value for the target cell. This means that the UE 1201 stores the TA value based on the UE-based TA measurement, the TA value of the source cell, and the TAT associated with the TA value of the source cell (e.g., as in Figure 6 ). Before the TAT associated with the TA value of the source cell expires, UE 1201 may continue to update the TA value for the target cell based on the TA value of the source cell. After the corresponding TAT expires (before receiving TA value update information from the target cell), UE 1201 may consider the TA value for the target cell invalid. UE 1201 may then trigger a RACH procedure for UL synchronization.

[0305] Regarding the calculated TA values ​​for other candidate cells (instead of the target cell to which the UE 1201 is handed over), there may be two options in different embodiments, namely Option #X or Option #Y, as shown below.

[0306] (1) Option #X: After UE 1201 switches to the target cell (eg, cell #1), UE 1201 should release the calculated TA values ​​for other candidate cells (eg, cell #2).

[0307] (2) Option #Y: UE 1201 maintains the calculated TA values ​​for other candidate cells. If yes, the UE 1201 may be configured with a corresponding TAT for determining whether the calculated TA value is invalid.

[0308] The description herein is provided to enable one skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A user equipment (UE), comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to cause the UE to: receiving a radio resource control (RRC) reconfiguration message from a base station (BS), wherein the RRC reconfiguration message includes a cell handover configuration for a set of candidate cells; receiving a cell handover command from the BS, wherein the cell handover command includes identifier ID information associated with a first candidate cell in the set of candidate cells; and A cell handover is performed to the first candidate cell based on the cell handover command.

2. The UE according to claim 1, wherein the cell switching command comprises at least one of the following: index information of the candidate cell configuration of the first candidate cell; a first timing advance (TA) value for the first candidate cell; or A timer length of a timing advance timer TAT associated with the first TA value.

3. The UE of claim 1 , wherein the processor is configured to cause the UE to: If the UE fails to access the first candidate cell, initiating a re-establishment procedure; and If first information indicating that the set of candidate cells can be used for recovery has been configured for the UE, maintaining the first configuration, wherein the first configuration includes at least a configuration for a primary cell or a primary cell in a secondary cell group (SpCell), a configuration for one or more primary cell groups (MCGs) (SCells), a multi-radio dual connectivity (MR-DC) configuration, an overheat assistance configuration, and an in-device coexistence (IDC) assistance configuration; or If the first information is not configured for the UE, the first configuration is released.

4. The UE of claim 3, wherein the processor is further configured to cause the UE to: selecting a second candidate cell for the RRC re-establishment procedure; determining whether the second candidate cell is a candidate cell within the set of candidate cells; and If the second candidate cell is the one candidate cell within the set of candidate cells, applying a cell handover configuration to the second candidate cell and performing a cell handover to the second candidate cell; or If the second candidate cell is not the one candidate cell within the set of candidate cells, and if the first information has been configured to the UE, releasing the first configuration.

5. The UE according to claim 4, wherein the processor is configured to cause the UE to transmit an RRC reconfiguration complete message associated with the second candidate cell to the CU, and wherein the RRC reconfiguration complete message includes identifier (ID) information related to the second candidate cell.

6. The UE according to claim 1 , wherein the RRC reconfiguration message includes second information instructing the UE to calculate at least one of the following: a first timing advance (TA) value for the first candidate cell; or A second TA value for the second candidate cell.

7. The UE according to claim 6, after receiving the second information including ID information of both the first candidate cell and the second candidate cell, the processor is configured to cause the UE to calculate the first TA value for the first candidate cell and the second TA value for the second candidate cell.

8. The UE according to claim 6, wherein the first TA value or the second TA value is calculated based on at least one of the following: a reception timing difference between a source cell of the UE and the first candidate cell or the second candidate cell; or The TA value for the source cell.

9. The UE according to claim 6 or claim 7, wherein the processor is configured to cause the UE to release or store the second TA value for the second candidate cell after the UE switches to the first candidate cell.

10. The UE of claim 9, in response to storing the second TA value for the second candidate cell, the processor is configured to cause the UE to determine whether the second TA value is valid based on a timing advance timer (TAT) associated with the second TA value.

11. The UE according to claim 6 or claim 7, wherein the processor is configured to cause the UE to release or store the first TA value for the first candidate cell after the UE switches to the first candidate cell.

12. The UE of claim 11, in response to storing the first TA value for the first candidate cell, the processor is configured to cause the UE to report the first TA value to a candidate DU associated with the first candidate cell via an RRC message or a media access control (MAC) control element (CE).

13. A distributed source unit (DU) of a base station (BS), comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to cause the source DU to: receiving, from a centralized unit (CU) of the BS, a first timing advance (TA) value list for a group of candidate cells, wherein the first TA value list comprises a first TA value for a first candidate cell in the group of candidate cells; and A cell handover command is transmitted to a user equipment (UE), wherein the cell handover command includes identifier (ID) information related to the first candidate cell.

14. The source DU according to claim 13, wherein the cell switching command comprises at least one of the following: the first TA value for the first candidate cell; or A timer length of a timing advance timer TAT associated with the first TA value.

15. The source DU of claim 13, wherein the first TA value list further comprises a second TA value for a second candidate cell within the set of candidate cells.

16. The source DU of claim 13 , after transmitting the cell switching command, the processor is configured to cause the source DU to transmit, via the CU, at least one of the following to a candidate distributed unit DU of the BS associated with the first candidate cell: A second TA value list; or Additional information associated with the second TA value list.

17. The source DU according to claim 16, wherein the second TA value list includes all TA values ​​in the first TA value list, or includes all TA values ​​in the first TA value list except the first TA value for the first candidate cell included in the cell handover command.

18. The source DU of claim 16, wherein the additional information associated with a TA value within the TA value list includes at least one of: The absolute time when the TA value is received; The time elapsed since the receipt of the TA value; or The remaining valid period of the TA value.

19. A centralized unit CU of a base station BS, comprising: at least one memory; as well as at least one processor coupled to the at least one memory and configured to cause the CU to: transmitting a request for cell handover configuration for a set of candidate cells to one or more candidate distributed units DU of the BS; receiving a response corresponding to the request from the one or more candidate DUs, wherein the response includes the cell handover configuration for the set of candidate cells; and The cell handover configuration for the set of candidate cells is transmitted to a user equipment (UE) via a source DU of the BS based on the response.

20. A processor for wireless communication, comprising: at least one controller coupled to at least one memory and configured to cause the processor to: receiving a radio resource control (RRC) reconfiguration message from a base station (BS), wherein the RRC reconfiguration message includes a cell handover configuration for a set of candidate cells; receiving a cell handover command from the BS, wherein the cell handover command includes identifier ID information associated with a first candidate cell in the set of candidate cells; and A cell handover is performed to the first candidate cell based on the cell handover command.

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