Method and device for TA acquisition failure and preamble transmission conflict

Abstract

Embodiments of the present application relate to a method and apparatus for lower layer based mobility with timing advance (TA) acquisition failure and preamble transmission conflicts in a 3rd generation partnership project (3GPP) 5G system or the like. According to an embodiment of the present application, a candidate decentralized unit (DU) of a base station (BS) comprises: a transceiver; and a processor coupled to the transceiver and configured to cause the candidate DU to: receive, from a centralized unit (CU) of the BS, a request for a cell handover procedure associated with a candidate cell; and transmitting a response including configuration information associated with the candidate cell to the CU based on the request.

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication techniques, and more particularly, to methods and apparatus for lower layer based mobility with timing advance (TA) acquisition failure and preamble transmission collision. Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. Wireless communication systems may employ a variety of access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of wireless communication systems may include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems, which may also be referred to as New Radio (NR) systems.

[0003] Currently, the details regarding TA acquisition failure and preamble transmission collision in lower layer based mobility scenarios have not been discussed in 3GPP 5G technology. Summary of the invention

[0004] Some embodiments of the present application provide a user equipment (UE). The UE includes: a transceiver; and a processor coupled to the transceiver; and the processor is configured to cause the UE to: receive radio resource control (RRC) configuration information associated with one or more candidate cells, the one or more candidate cells being related to a cell switching procedure; and receive a first indication to trigger a timing advance (TA) acquisition procedure or a TA re-acquisition procedure for a first candidate cell within the one or more candidate cells before performing the cell switching procedure.

[0005] In an embodiment of the present application, TA acquisition or early TA acquisition means that the UE is expected to perform a TA acquisition procedure before a cell switching procedure. TA reacquisition or early TA reacquisition means that the UE is expected to perform a TA reacquisition procedure before a cell switching procedure. TA acquisition, early TA acquisition, TA reacquisition or early TA reacquisition may be triggered by receiving an indication (e.g., a physical downlink control channel (PDCCH) command as downlink control information (DCI)) from a serving BS.

[0006] In some embodiments of the present application, the processor is configured to cause the UE to: determine whether a conflict occurs between an uplink (UL) transmission in a serving cell of the UE and a random access channel opportunity (RO) in a candidate cell within the one or more candidate cells, wherein the RO is associated with the TA acquisition procedure or the TA reacquisition procedure; and in response to the conflict, execute the TA acquisition procedure or the TA reacquisition procedure associated with the RO.

[0007] In some embodiments of the present application, if the first indication is received when the UE is initiating a first random access (RA) procedure in a serving cell, the processor is configured to cause the UE to: execute a second RA procedure for the TA acquisition procedure or the TA re-acquisition procedure; or suspend the first RA procedure.

[0008] In some embodiments of the present application, the processor is configured to cause the UE to continue to perform the suspended first RA procedure after completing the second RA procedure.

[0009] In some embodiments of the present application, the processor is configured to cause the UE to transmit a first preamble for the TA acquisition procedure or the TA re-acquisition procedure to the first candidate cell once or several times based on the RRC configuration information.

[0010] In some embodiments of the present application, the processor is configured to cause the UE to: receive a second indication for the TA reacquisition procedure associated with the first candidate cell; and transmit a second preamble for the TA reacquisition procedure associated with the first candidate cell at a higher power than the first preamble.

[0011] In some embodiments of the present application, in response to failure to receive a TA value after transmitting the first preamble code, the processor is configured to cause the UE to transmit failure information to a source distributed unit (DU) of a base station (BS) or to a centralized unit (CU) of the BS via the source DU.

[0012] Some embodiments of the present application provide a candidate distributed unit (DU) of a base station (BS). The candidate DU includes: a transceiver; and a processor, which is coupled to the transceiver; and the processor is configured to cause the candidate DU to: receive a request for a cell switching procedure associated with a candidate cell from a centralized unit (CU) of the BS; and transmit a response including configuration information associated with the candidate cell to the CU based on the request.

[0013] In some embodiments of the present application, the processor is configured to cause the candidate DU to: receive a preamble for a timing advance (TA) acquisition procedure or a TA reacquisition procedure; calculate a TA value based on the received preamble; and transmit the TA value, the identifier (ID) information of the candidate cell, or at least one of the ID information of a user equipment (UE) to the CU.

[0014] In some embodiments of the present application, the processor is configured to cause the candidate DU to receive at least one of the following from the CU: a first indication indicating the failure of a TA acquisition procedure or a TA reacquisition procedure; a request for random access channel (RACH) configuration information for the TA acquisition procedure or the TA reacquisition procedure; or a measurement result of a user equipment (UE).

[0015] In some embodiments of the present application, in response to failure to receive a preamble for a TA acquisition procedure or a TA reacquisition procedure in a RACH opportunity (RO), the processor is configured to cause the candidate DU to determine failure of the TA acquisition procedure or the TA reacquisition procedure.

[0016] In some embodiments of the present application, in response to receiving the first indication from the CU or in response to determining the failure of the TA acquisition procedure or the TA reacquisition procedure, the processor is configured to cause the candidate DU to transmit a first message to the CU, wherein the first message includes at least one of the following: identifier (ID) information of the candidate cell associated with the TA acquisition procedure or the TA reacquisition procedure; ID information of the UE; a second indication for indicating the failure of the TA acquisition procedure or the TA reacquisition procedure; a request for measurement results of the UE; a third indication for indicating the TA reacquisition procedure; or the RACH configuration information for the TA acquisition procedure or the TA reacquisition procedure.

[0017] In some embodiments of the present application, the response includes a random access channel (RACH) resource for a timing advance (TA) acquisition procedure, and the RACH resource includes a preamble or a RACH opportunity (RO).

[0018] Some embodiments of the present application provide a centralized unit (CU) of a base station (BS). The CU includes: a transceiver; and a processor coupled to the transceiver; and the processor is configured to cause the CU to: transmit a request to a candidate distributed unit (DU) of the BS, wherein the request includes identifier (ID) information of one or more candidate cells; receive a response corresponding to the request from the candidate DU, wherein the response is associated with a cell switching procedure; and transmit first configuration information to a user equipment (UE) via a source DU of the BS based on the response.

[0019] In some embodiments of the present application, the processor is configured to cause the CU to receive second configuration information from the candidate DU, the second configuration information including at least one of the following: a TA value calculated for a timing advance (TA) acquisition procedure or a TA reacquisition procedure; ID information of a candidate cell associated with the TA acquisition procedure or the TA reacquisition procedure; ID information of the UE; a first indication for indicating a failure of the TA acquisition procedure or the TA reacquisition procedure; a request for a measurement result of the UE; a second indication for indicating the TA reacquisition procedure; or random access channel (RACH) configuration information for the TA reacquisition procedure.

[0020] In some embodiments of the present application, after receiving the second configuration information from the candidate DU, the processor is configured to cause the CU to transmit the second configuration information to the source DU.

[0021] In some embodiments of the present application, the processor is configured to cause the CU to receive second information from the source DU, and wherein the second information includes at least one of the following: a third indication for indicating the failure of a TA acquisition procedure or a TA reacquisition procedure; ID information of a candidate cell associated with the TA acquisition procedure or the TA reacquisition procedure; or a layer 1 measurement result of the UE.

[0022] In some embodiments of the present application, the second information is received by the source DU from the UE.

[0023] In some embodiments of the present application, the processor is configured to cause the CU to transmit at least one of the following to the candidate DU: a fourth indication indicating the failure of the TA acquisition procedure or the TA re-acquisition procedure; or the layer 1 measurement result of the UE.

[0024] In some embodiments of the present application, the processor is configured to cause the CU to: receive failure information related to a TA acquisition procedure or a TA reacquisition procedure from the UE; and transmit at least one of the following to the candidate DU: a fifth indication indicating the failure of the TA acquisition procedure or the TA reacquisition procedure; or a request for random access channel (RACH) configuration information for the TA acquisition procedure or the TA reacquisition procedure.

[0025] Some embodiments of the present application provide a source distributed unit (DU) of a base station (BS). The source DU includes: a transceiver; and a processor coupled to the transceiver; and the processor is configured to cause the source DU to: receive first configuration information associated with one or more candidate cells from a centralized unit (CU) of the BS, the one or more candidate cells being related to a cell switching procedure; transmit second configuration information to a user equipment (UE) based on the first configuration information received from the CU; and transmit a first indication to the UE to trigger a timing advance (TA) acquisition procedure or a TA reacquisition procedure for a first candidate cell within the one or more candidate cells before performing the cell switching procedure.

[0026] In some embodiments of the present application, the first indication is included in downlink control information (DCI).

[0027] In some embodiments of the present application, the first configuration information includes at least one of the following items: a TA value calculated for the TA acquisition procedure or the TA reacquisition procedure; identifier (ID) information of the first candidate cell; ID information of the UE; a second indication for indicating the TA reacquisition procedure; or random access channel (RACH) configuration information for the TA reacquisition procedure.

[0028] In some embodiments of the present application, if the first configuration information includes at least one of the second indication or the RACH configuration information for the TA reacquisition procedure, then the processor is configured to cause the source DU to transmit a third indication to trigger the TA reacquisition procedure to the candidate DU of the BS.

[0029] In some embodiments of the present application, the first configuration information is generated by the candidate DU and then transmitted to the CU.

[0030] In some embodiments of the present application, the processor is configured to cause the source DU to: determine whether a TA value is received from a candidate DU of the BS within a certain time period; and in response to determining that the TA value is not received within the time period, determine that the TA acquisition procedure or the TA re-acquisition procedure has failed.

[0031] In some embodiments of the present application, the processor is configured to cause the source DU to: start a timer associated with the TA value; and determine, upon expiration of the timer, that the TA value is not received within the time period.

[0032] In some embodiments of the present application, the timer is started immediately after transmitting downlink control information (DCI) for the TA acquisition procedure or the TA re-acquisition procedure, or the timer is started in a random access channel opportunity (RO).

[0033] In some embodiments of the present application, the processor is configured to cause the source DU to receive failure information about failure to acquire a TA value from the UE.

[0034] In some embodiments of the present application, in response to determining that the TA acquisition procedure or the TA re-acquisition procedure has failed or in response to receiving the failure information, the processor is configured to cause the source DU to transmit at least one of the following items to the CU: a fourth indication indicating a failure to acquire the TA value; ID information of the first candidate cell; or a layer 1 measurement result of the UE.

[0035] In some embodiments of the present application, the processor is configured to cause the source DU to receive first information from the UE, and wherein the first information includes at least one of the following: a fifth indication for indicating the failure of the TA acquisition procedure or the TA reacquisition procedure; ID information of the first candidate cell; or a layer 1 measurement result of the UE.

[0036] In some embodiments of the present application, the processor is configured to cause the source DU to transmit the first information to the CU.

[0037] Some embodiments of the present application provide a method performed by a UE. The method includes: receiving radio resource control (RRC) configuration information associated with one or more candidate cells, the one or more candidate cells being related to a cell switching procedure; and receiving a first indication to trigger a timing advance (TA) acquisition procedure or a TA re-acquisition procedure for a first candidate cell in the one or more candidate cells before performing the cell switching procedure.

[0038] Some embodiments of the present application provide a method performed by a candidate distributed unit (DU) of a base station (BS). The method includes: receiving a request for a cell switching procedure associated with a candidate cell from a centralized unit (CU) of the BS; and transmitting a response including configuration information associated with the candidate cell to the CU based on the request.

[0039] Some embodiments of the present application provide a method performed by a centralized unit (CU) of a base station (BS). The method includes: transmitting a request to a candidate distributed unit (DU) of the BS, wherein the request includes identifier (ID) information of one or more candidate cells; and receiving a response corresponding to the request from the candidate DU, wherein the response is associated with a cell switching procedure; and transmitting first configuration information to a user equipment (UE) via a source DU of the BS based on the response.

[0040] Some embodiments of the present application provide a method performed by a source distributed unit (DU) of a base station (BS). The method includes: receiving first configuration information associated with one or more candidate cells from a centralized unit (CU) of the BS, the one or more candidate cells being related to a cell switching procedure; transmitting second configuration information to a user equipment (UE) based on the first configuration information received from the CU; and transmitting a first indication to the UE to trigger a timing advance (TA) acquisition procedure or a TA re-acquisition procedure for a first candidate cell in the one or more candidate cells before performing the cell switching procedure.

[0041] Some embodiments of the present application provide a device for wireless communication. The device includes: a non-transitory computer-readable medium having computer-executable instructions stored thereon; a receiving circuit; a transmitting circuit; and a processor coupled to the non-transitory computer-readable medium, the receiving circuit, and the transmitting circuit, wherein the computer-executable instructions cause the processor to implement the above method performed by a UE or a network node (e.g., a base station (BS), a CU, or a DU).

[0042] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to describe the manner in which the advantages and features of the present application can be obtained, the description of the present application is carried out with reference to its specific embodiments, which are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present application and therefore should not be considered as limiting the scope thereof.

[0044] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present application is illustrated.

[0045] Figure 2 A schematic diagram illustrating inter-cell layer 1 / layer 2 (L1 / L2) mobility according to some embodiments of the present application is illustrated.

[0046] Figures 3 to 6An exemplary flow chart associated with a cell handover procedure according to some embodiments of the present application is illustrated.

[0047] Figures 7 to 10 An exemplary flow chart of performing a cell handover procedure according to some embodiments of the present application is illustrated.

[0048] Fig.11 A block diagram illustrating an exemplary apparatus according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0049] The detailed description of the accompanying drawings is intended to describe the preferred embodiments of the present application, but is not intended to represent the only form in which the present application can be practiced. It should be understood that the same or equivalent functions can be achieved by different embodiments intended to be included in the spirit and scope of the present application.

[0050] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architectures and new service scenarios such as 3GPP 5G, 3GPP LTE Release 8, etc. Please consider that, as network architectures and new service scenarios develop, all embodiments in the present application are also applicable to similar technical problems; and in addition, the terms stated in the present application may be changed, which should not affect the principles of the present application.

[0051] Figure 1 The diagram illustrates a schematic diagram of a wireless communication system according to some embodiments of the present application. Figure 1 , the wireless communication system 100 includes at least one base station (BS) 101 and at least one user equipment (UE) 102. Specifically, for illustrative purposes, the wireless communication system 100 includes one BS 101 and two UEs 102 (e.g., UE 102a and UE 102b). Figure 1 A specific number of BSs and UEs are illustrated in FIG. 1 , but please consider that in some other embodiments of the present application, the wireless communication system 100 may include more or fewer BSs and UEs.

[0052] The wireless communication system 100 is compatible with any type of network capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with wireless communication networks, cellular telephone networks, time division multiple access (TDMA)-based networks, code division multiple access (CDMA)-based networks, orthogonal frequency division multiple access (OFDMA)-based networks, LTE networks, 3GPP-based networks, 3GPP 5G networks, satellite communication networks, high altitude platform networks, and / or other communication networks.

[0053] BS 101 may communicate with a core network (CN) node (not shown) such as a mobility management entity (MME) or a serving gateway (S-GW), a mobility management function (AMF), or a user plane function (UPF) via an interface. BSs are also referred to as access points, access terminals, base stations, macro cells, Node Bs, enhanced Node Bs (eNBs), gNBs, home Node Bs, relay nodes, or devices, or are described using other terms used in the art. In 5G NR, BSs may also be referred to as RAN nodes or network equipment. Each BS may serve several UEs within a service area (for example, a cell or a cell sector) via wireless communication links. Neighboring BSs may communicate with each other as needed, such as during a handover procedure for a UE.

[0054] UE 102 (e.g., UE 102a and UE 102b) should be understood as any type of terminal device, which may include a computing device, such as a desktop computer, a laptop computer, a personal digital assistant (PDA), a tablet computer, a smart TV (e.g., a TV connected to the Internet), a set-top box, a game console, a security system (including a security camera), a car computer, a network device (e.g., a router, a switch and a modem), etc. According to an embodiment of the present application, UE 102 may include a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a device with a subscriber identity module, a personal computer, a selective call receiver, or any other device capable of sending and receiving communication signals on a wireless network. In some embodiments, UE 102 may include a wearable device, such as a smart watch, a fitness band, an optical head-mounted display, etc. In addition, UE 102 may be referred to as a subscriber unit, a mobile device, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal or a device, or described using other terms used in this technology. UE 102 may communicate directly with BS 101 via uplink (UL) communication signals.

[0055] In 3GPP Release 18, support for inter-cell mobility based on Layer 1 / Layer 2 (L1 / L2) signaling has been discussed. Specifically, configurations from multiple cells may be provided to the UE in advance, and the BS (e.g., gNB) may switch the UE to a new cell using L1 / L2 signaling in consideration of received physical layer measurement results. According to the 3GPP standard document, a BS may be composed of a BS centralized unit (CU) and one or more BS decentralized units (DUs). The BS-CU and BS-DU are connected via the F1 interface, which is a logical interface. One BS-DU is connected to only one BS-CU.

[0056] Figure 2A schematic diagram illustrating inter-cell layer 1 / layer 2 (L1 / L2) mobility according to some embodiments of the present application is shown. Figure 2 As shown in , the CU can communicate with two DUs (ie, DU1 or DU2) via the F1 interface. Figure 2 The CU in may implement traditional mobility decisions based on layer 3 (L3) measurement results. Figure 2 DU1 or DU2 in the L1 / L2 mobility decision can be implemented based on the physical layer measurement results.

[0057] Compared with traditional L3 mobility, L1 / L2 mobility is considered to be faster and has less processing delay and signaling delay. In traditional L3 mobility, CU (e.g. Figure 2 ) makes mobility decisions based on received radio resource management (RRM) measurement reports. Unlike traditional L3 mobility, in L1 / L2 mobility, DUs (e.g., Figure 2 DU1 or DU2 shown in the figure makes mobility decisions based on physical layer measurements carried, for example, in channel state information (CSI) reports. In addition, in traditional L3 mobility, a handover command is sent from the SN CU to the UE via RRC signaling, while in L1 / L2 mobility, a "handover" command is sent from the DU to the UE via L1 / L2 signaling (e.g., downlink control information (DCI) or media access control (MAC) control element (CE)). The "handover" command in L1 / L2 mobility can be about cell activation or deactivation, such as activating a new serving PCell while deactivating an old serving PCell.

[0058] Currently, the problem of TA acquisition failure and preamble transmission conflict in the mobility scenario based on the lower layer has not been solved. The embodiments of the present application are intended to solve such problems. For example, in some embodiments of the present application, considering the situation of "random access response (RAR) required", three possible options are introduced, including candidate cell triggering, source cell triggering and CU triggering TA re-acquisition. In some embodiments of the present application, considering the situation of "no RAR required", UE-based triggered TA re-acquisition is introduced. In some embodiments of the present application, after the UE receives the PDCCH command, the UE will transmit the preamble in the indicated RACH opportunity (RO) of the candidate cell. In some embodiments of the present application, the problem of how to deal with the conflict between the uplink (UL) transmission (e.g., scheduling request (SR)) in the serving cell and the RO of the candidate cell is introduced. In some embodiments of the present application, when the UE receives the PDCCH command for triggering TA acquisition, the UE is initiating the RA procedure in the serving cell, for example, after the UL data arrives in the serving cell, the UL is no longer synchronized. In some embodiments of the present application, the problem of how to deal with the conflict between the two RA procedures is studied.

[0059] In an embodiment of the present application, TA acquisition or early TA acquisition means that the UE is expected to perform a TA acquisition procedure before a cell switching procedure. TA reacquisition or early TA reacquisition means that the UE is expected to perform a TA reacquisition procedure before a cell switching 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 a DCI) from a serving BS.

[0060] Some embodiments of the present application may be applicable to the scenario of "lower layer triggered mobility" or "L1 / L2 triggered mobility", and the abbreviation of at least one of them may be "LTM". In the LTM scenario, the 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., a CU of the serving gNB) decides to switch 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 including ID information of one or more candidate cells to the UE. 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 switching command. For example, the UE may obtain or acquire a TA value via a random access (RA) or preamble transmission. For dynamic switching purposes, the UE may report Layer 1 (L1) measurements. The serving gNB (e.g., source DU) may transmit a cell switching command, such as a MAC CE or DCI. The UE may apply an RRC reconfiguration message and start a timer upon receiving a lower layer command.

[0061] Specifically, in the present application Figures 3 to 11 In the embodiments of the present invention, both inter-DU mobility scenarios 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 with the CU remains the same, and the UE may 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 with the CU remains the same, and the UE may change from a source cell to a target cell associated with the same DU due to mobility. More details will be illustrated below in conjunction with the accompanying drawings.

[0062] Figure 3 Another exemplary flow chart associated with a cell handover procedure according to some embodiments of the present application is illustrated. Figure 3 The exemplary flowchart 300 in the embodiment of the present invention may be performed by a UE (e.g., Figure 1 Although described with respect to a UE, it should be understood that other devices may be configured to perform the same Figure 3 The details described in all other embodiments of the present application are applicable to Figure 3 In addition, Figure 3 The details described in the embodiments apply to Figure 1 ,2 And all embodiments from 4 to 11.

[0063] In such Figure 3 In the exemplary flow chart 300 shown in FIG. 1 , in operation 301, the UE may receive RRC configuration information associated with one or more candidate cells, the one or more candidate cells being related to a cell switching procedure. Figure 3 In operation 302 shown in FIG. 1 , the UE may receive an indication (denoted as indication #1 for simplicity) to trigger a TA acquisition procedure or a TA re-acquisition procedure for a candidate cell (denoted as candidate cell #1 for simplicity) within one or more candidate cells before performing a cell switching procedure.

[0064] In some embodiments, the UE may determine whether a conflict occurs between "UL transmission in the UE's serving cell" and "RO in a candidate cell within one or more candidate cells", where the RO is associated with a TA acquisition procedure or a TA reacquisition procedure. If the UE determines that a conflict occurs, the UE may perform a TA acquisition procedure or a TA reacquisition procedure associated with the RO.

[0065] In some embodiments, if indication #1 is received when the UE is initiating an RA procedure (denoted as RA procedure #1 for simplicity) in the UE's serving cell, the UE may perform another RA procedure (denoted as RA procedure #2 for simplicity) for a TA acquisition procedure or a TA reacquisition procedure, or suspend RA procedure #1. In an embodiment, the UE may continue to perform the suspended RA procedure #1 after completing RA procedure #2.

[0066] In some other embodiments, if indication #1 is received when the UE is initiating RA procedure #1, the UE may perform RA procedure #1 or suspend RA procedure #2. In an embodiment, the UE may continue to perform the suspended RA procedure #2 after completing RA procedure #1.

[0067] In some embodiments, based on the RRC configuration information received in operation 301, the UE may transmit a preamble (denoted as preamble #1 for simplicity) for a TA acquisition procedure or a TA reacquisition procedure to the candidate cell #1 once or several times. Figure 7 Specific examples are described in the embodiments of the present invention.

[0068] In some embodiments, the UE may receive another indication (denoted as indication #2 for simplicity) for a TA reacquisition procedure associated with candidate cell #1 and transmit another preamble for the TA reacquisition procedure associated with candidate cell #1 at a higher power than preamble #1.

[0069] In some embodiments, in response to failing to receive a TA value after transmitting preamble #1, the UE may send a source DU (e.g., Figure 2 DU2 shown and illustrated in FIG) or via a source DU to a CU of a BS (e.g., Figure 2 CU) transmission failure information shown and illustrated in FIG. Fig.10 Specific examples are described in the embodiments of the present invention.

[0070] Figure 4 An exemplary flow chart associated with a cell handover procedure according to some embodiments of the present application is illustrated. Figure 4 The exemplary flowchart 400 in the embodiment of the present invention may be composed of a candidate DU (e.g., Figure 2 In some cases, the candidate DU may also be referred to as the target DU. Although described with respect to the candidate DU, it should be understood that other devices may be configured to perform the same Figure 4 The details described in all other embodiments of the present application are applicable to Figure 4 In addition, Figure 4 The details described in the embodiments apply to Figures 1 to 3 and all embodiments from 5 to 11.

[0071] In exemplary flowchart 400, in operation 401, a candidate DU of a BS (e.g., Figure 2 DU1) can be obtained from a CU of a BS (e.g., Figure 2 A CU (shown and illustrated in FIG. 4 ) receives a request for a cell switching procedure associated with a candidate cell.

[0072] In such Figure 4 In operation 402 shown in , the candidate DU may transmit a response including configuration information associated with the candidate cell to the CU based on the request. In some embodiments, the response includes RACH resources for a TA acquisition procedure, and the RACH resources include a preamble or a RO.

[0073] In some embodiments, the candidate DU may receive a preamble for a TA acquisition procedure or a TA re-acquisition procedure, calculate a TA value based on the received preamble, and transmit at least one of the following to the CU:

[0074] (1) The calculated TA value,

[0075] (2) candidate cell ID information (e.g., candidate cell index), or

[0076] (3) UE (e.g. Figure 1102) as shown and illustrated in FIG. Figure 7 Specific examples are described in the embodiments of the present invention.

[0077] In some embodiments, the candidate DU may receive at least one of the following from the CU:

[0078] (1) an indication for indicating the failure of the TA acquisition procedure or the TA re-acquisition procedure (denoted as indication #3 for simplicity);

[0079] (2) a request for RACH configuration information for a TA acquisition procedure or a TA reacquisition procedure; or

[0080] (3) UE measurement results. Fig. 9 Specific examples are described in the embodiments of the present invention.

[0081] In some embodiments, in response to failing to receive a preamble for a TA acquisition procedure or a TA re-acquisition procedure in the RO, the candidate DU may determine a failure of the TA acquisition procedure or the TA re-acquisition procedure.

[0082] In some embodiments, in response to receiving indication #3 from the CU or in response to determining the failure of the TA acquisition procedure or the TA re-acquisition procedure, the candidate DU may transmit a message (denoted as message #1 for simplicity) to the CU. Message #1 may include at least one of the following:

[0083] (1) ID information (e.g., index) of candidate cells associated with a TA acquisition procedure or a TA reacquisition procedure;

[0084] (2) UE ID information;

[0085] (3) an indication for indicating the failure of the TA acquisition procedure or the TA re-acquisition procedure (denoted as indication #4 for simplicity);

[0086] (4) Request for UE measurement results;

[0087] (5) an indication for instructing the TA reacquisition procedure (denoted as indication #5 for simplicity); or

[0088] (6) RACH configuration information for TA acquisition procedure or TA re-acquisition procedure. Figure 8 Specific examples are described in the embodiments of the present invention.

[0089] Figure 5 Another exemplary flow chart associated with a cell handover procedure according to some embodiments of the present application is illustrated. Figure 5 The exemplary flowchart 500 in the embodiment of the present invention may be performed by a CU (e.g., Figure 2Although described with respect to a CU, it should be understood that other devices may be configured to perform the same Figure 5 The details described in all other embodiments of the present application are applicable to Figure 5 In addition, Figure 5 The details described in the embodiments apply to Figures 1 to 4 and all embodiments 6 to 11.

[0090] In such Figure 5 In the exemplary flowchart 500 shown in FIG. 5 , in operation 501, a CU (e.g., Figure 2 The CU shown and illustrated in FIG. 1 may transmit a request to a candidate DU of a BS. The request includes ID information of one or more candidate cells. Figure 5 In operation 502 shown in FIG. 1 , the CU may receive a response corresponding to the request from the candidate DU. The response is associated with a cell switching procedure. Figure 5 In operation 503 shown in FIG. 5 , the CU may, based on the response, send a source DU (eg, Figure 2 DU2) shown and illustrated in FIG. Figure 1 UE 102 shown and illustrated in FIG. 1 transmits configuration information.

[0091] In some embodiments, the CU may receive further configuration information from the candidate DU including at least one of the following:

[0092] (1) TA value calculated for the TA acquisition procedure or TA re-acquisition procedure;

[0093] (2) ID information of a candidate cell associated with a TA acquisition procedure or a TA re-acquisition procedure, such as an index of the candidate cell;

[0094] (3) UE ID information;

[0095] (4) An indication indicating the failure of a TA acquisition procedure or a TA re-acquisition procedure (e.g., Figure 4 Instruction #4) described in the embodiments;

[0096] (5) Request for UE measurement results;

[0097] (6) Instructions for instructing TA reacquisition procedures (e.g., in Figure 4 Instruction #5) as described in the embodiments of the present invention; or

[0098] (7) RACH configuration information for TA reacquisition procedure. Figure 7 or Figure 8 Specific examples are described in the embodiments of the present invention.

[0099] In some embodiments, after receiving the further configuration information from the candidate DU, the CU may transmit the further configuration information to the source DU.

[0100] In some embodiments, the CU may receive information (denoted as information #1 for simplicity) including at least one of the following from the source DU:

[0101] (1) an indication for indicating the failure of the TA acquisition procedure or the TA re-acquisition procedure (denoted as indication #6 for simplicity);

[0102] (2) ID information of candidate cells associated with the TA acquisition procedure or TA re-acquisition procedure; or

[0103] (3) UE layer 1 (L1) measurement results. Fig. 9 Specific examples are described in the embodiments of the present invention.

[0104] In some embodiments, information #1 is received by a source DU from a UE and then transmitted to a CU.

[0105] In some embodiments, the CU may transmit at least one of the following to the candidate DU:

[0106] (1) An indication indicating the failure of a TA acquisition procedure or a TA re-acquisition procedure (e.g., Figure 4 Instruction #3) as described in the embodiments of the present invention; or

[0107] (2) UE’s L1 measurement results.

[0108] In some embodiments, the CU may receive failure information related to the TA acquisition procedure or the TA re-acquisition procedure from the UE, and transmit at least one of the following to the candidate DU:

[0109] (1) An indication indicating the failure of a TA acquisition procedure or a TA re-acquisition procedure (e.g., Figure 4 Instruction #3) as described in the embodiments of the present invention; or

[0110] (2) Request for RACH configuration information for TA acquisition procedure or TA re-acquisition procedure. Fig. 9 Specific examples are described in the embodiments of the present invention.

[0111] Figure 6 Another exemplary flow chart associated with a cell handover procedure according to some embodiments of the present application is illustrated. Figure 6 The exemplary flowchart 600 in the embodiment of the present invention may be performed by a source DU (e.g., Figure 2Although described with respect to a source DU, it should be understood that other devices may be configured to perform the same Figure 6 The details described in all other embodiments of the present application are applicable to Figure 6 In addition, Figure 6 The details described in the embodiments apply to Figures 1 to 5 and all embodiments 7 to 11.

[0112] In such Figure 6 In the exemplary flowchart 600 shown in FIG. 6 , in operation 601, a source DU (e.g., Figure 2 DU2) may receive configuration information associated with one or more candidate cells from a CU of the BS, the one or more candidate cells being related to a cell switching procedure. In operation 602, the source DU may transmit further configuration information to the UE based on the configuration information received from the CU in operation 601. In operation 603, the source DU may transmit to the UE an indication (e.g., as in the example of the example in the example) that a TA acquisition procedure or a TA re-acquisition procedure is to be triggered for a candidate cell within the one or more candidate cells before performing the cell switching procedure. Figure 3 Indication #1 described in the embodiment of ). In an embodiment, the indication is included in the DCI (e.g., a PDCCH command).

[0113] In some embodiments, the configuration information received in operation 601 includes at least one of the following:

[0114] (1) TA value calculated for the TA acquisition procedure or TA re-acquisition procedure;

[0115] (2) ID information of candidate cells;

[0116] (3) UE ID information;

[0117] (4) an indication for instructing the TA reacquisition procedure (denoted as indication #7 for simplicity); or

[0118] (5) RACH configuration information used for TA re-acquisition procedure.

[0119] In some embodiments, if the configuration information received in operation 601 includes indication #7 and / or RACH configuration information for a TA reacquisition procedure, the source DU may send a RACH configuration information to a candidate DU of the BS (eg, Figure 2 DU1) shown and illustrated in FIG. 6 transmits an indication (denoted as indication #8 for simplicity) that a TA reacquisition procedure is to be triggered. In some embodiments, the configuration information received in operation 601 is generated by a candidate DU and then transmitted to the CU.

[0120] In some embodiments, the source DU may determine whether a TA value is received from a candidate DU of the BS within a certain period of time. If the source DU determines that a TA value is not received within the period of time, the source DU may determine that a TA acquisition procedure or a TA reacquisition procedure has failed.

[0121] In some embodiments, the source DU may start a timer associated with the TA value and determine that the TA value has not been received within the time period upon expiration of the timer. In an embodiment, the timer is started upon transmission of a DCI (e.g., a PDCCH command) for a TA acquisition procedure or a TA re-acquisition procedure. In another embodiment, the timer is started in the RO.

[0122] In some embodiments, if the UE is in a candidate cell (e.g., Figure 3 The candidate cell #1 described in the embodiment of FIG. 1 transmits a preamble for a TA acquisition procedure or a TA re-acquisition procedure (for example, as in FIG. Figure 3 If the source DU fails to receive the TA value after one or several times of the preamble code #1) described in the embodiment of the present invention, the source DU may receive failure information about the failure to obtain the TA value from the UE.

[0123] In some embodiments, in response to determining that the TA acquisition procedure or the TA re-acquisition procedure has failed or in response to receiving failure information about failure to acquire the TA value from the UE, the source DU may transmit at least one of the following to the CU:

[0124] (1) An indication for indicating that a TA value could not be obtained (e.g., Figure 5 Instruction #6) described in the embodiments;

[0125] (2) ID information of the first candidate cell; or

[0126] (3) UE layer 1 (L1) measurement results. Fig. 9 Specific examples are described in the embodiments of the present invention.

[0127] In some embodiments, the source DU may receive information from the UE including at least one of the following:

[0128] (1) an indication for indicating the failure of the TA acquisition procedure or the TA re-acquisition procedure (denoted as indication #9 for simplicity);

[0129] (2) ID information of the first candidate cell; or

[0130] (3) UE’s L1 measurement results.

[0131] In some embodiments of the present application, the source DU may transmit the received information to the CU. Fig.10 Specific examples are described in the embodiments of the present invention.

[0132] The following description is as follows Figures 3 to 6 A specific embodiment of the flowchart shown and illustrated in any of the embodiments. It should be understood by those skilled in the art that changes may be made without departing from the spirit and scope of the present disclosure. Figures 7 to 10 The operation sequence of any of the exemplary flowcharts 700, 800, 900 and 1000 in the embodiment of the present invention may be eliminated or modified. Figures 7 to 10 Some operations of any of the exemplary flowcharts 700, 800, 900 and 1000 in.

[0133] Figure 7 An exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application is illustrated. The details described in all other embodiments of the present application apply to Figure 7 The embodiments shown in .

[0134] like Figure 7 As shown in FIG. 7 , BS 705 has a CU-DU architecture and includes CU 704, source DU 702, and candidate DU 703. Figure 7 In the embodiment of , the cell switching operation performed by UE 701 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. Figure 7 The flowchart 700 shown in FIG. 7 only shows the cell switching operation in the inter-DU scenario for exemplary purposes. If the source DU 702 and the candidate DU 703 are the same DU, the flowchart 700 can also be applied to the intra-DU scenario.

[0135] In such Figure 7 In the exemplary flowchart 700 shown in FIG. 7 , in operation 711, UE 701 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 705). 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. There is an F1 interface between the DU and the CU. For example, Figure 7 , BS 705 includes CU 704, source DU 702, and candidate DU 703. BS 705 may include one or more other candidate DUs ( Figure 7 not shown).

[0136] In operation 712 , the UE 701 receives an RRCReconfiguration message associated with one or more candidate cells for LTM purposes from the CU 704 via the source DU 702 .

[0137] In some embodiments, CU 704 determines to initiate L1 / L2-based inter-cell mobility configuration. CU 704 may receive a message including an RRCReconfiguration message from candidate DU 703 via an F1 interface. Then, in operation 712, CU 704 may transmit an RRCReconfiguration message from candidate DU 703 to UE 701 via source DU 702.

[0138] In some embodiments, if the configuration information transmitted from the CU 704 to the source DU 702 includes instructions for instructing the TA re-acquisition procedure (e.g., as in Figure 6 If the source DU 702 has an indication #7 described in the embodiment of the present invention and / or RACH configuration information for the TA re-acquisition procedure, the source DU 702 may transmit an indication to the candidate DU 703 to trigger the TA re-acquisition procedure (e.g., as in Figure 6 Instruction #8) described in the embodiments.

[0139] In operation 713, UE 701 may receive information to trigger a TA acquisition procedure or a TA re-acquisition procedure for a candidate cell within one or more candidate cells (e.g., as in Figure 3 In some embodiments, the information may be DCI, MAC CE or RRC signaling. If the information is DCI, it may be a PDCCH command.

[0140] In some embodiments, a conflict may occur between "UL transmission (e.g., SR) triggered by UE 701 in the serving cell" and "RO of the candidate cell for the TA acquisition or reacquisition procedure triggered by the information received in operation 713". The RO of the candidate cell may have a higher priority than the UL transmission in the serving cell.

[0141] In some embodiments, when UE 701 receives a PDCCH command for triggering TA acquisition and UE 701 is initiating a RA procedure in a serving cell (for example, the UL is no longer synchronized immediately after the UL data arrives in the serving cell), there may be the following two options in the following different embodiments, namely Option A and Option B.

[0142] (1) Option A: If two parallel RA procedures are allowed, UE 701 may perform the two RA procedures in parallel. However, RACH timings may conflict between the two RA procedures. If RACH timings conflict, one of the two RA procedures should be prioritized. For example, the preamble used for TA acquisition in the RACH timing of the candidate cell should be prioritized.

[0143] (2) Option B: If two parallel RA procedures are not allowed, one of the two RA procedures should be prioritized. For example, the preamble used for TA acquisition in the RACH opportunity of the candidate cell should be prioritized. The RA procedure for UL synchronization in the serving cell of UE 701 may be suspended. When the RA procedure for TA acquisition is completed, UE 701 may continue the RA procedure for UL synchronization in the serving cell.

[0144] In some embodiments, UE 701 may receive multiple PDCCH commands to trigger TA acquisition for different candidate cells. Once overlapping RO occurs, UE 701 needs to select one TA to acquire. If another TA acquisition fails, UE 701 may report the failure to the source DU 702 or CU 704. The network may trigger TA acquisition again.

[0145] In operation 714, UE 701 may transmit a preamble for TA acquisition to candidate DU 703. In some embodiments, UE 701 may transmit the preamble once. In some other embodiments, UE 701 may transmit the preamble several times, which is configurable. The number of preamble transmissions may be configured by RRC signaling or PDCCH command.

[0146] In operation 715, if the candidate DU 703 successfully receives the dedicated preamble, the candidate DU 703 calculates the TA value.

[0147] In operation 716, the candidate DU 703 may transmit a message to the CU 704 via the F1 interface. The F1 message may include at least one of the following: the calculated TA value, ID information of the corresponding candidate cell, and ID information of the UE 701. The F1 message may be a UL RRC message transfer message or a UE context modification request message.

[0148] In operation 717, after CU 704 receives the TA value, CU 704 may transmit the received TA value to source DU 702. In some embodiments, CU 704 may transmit at least one of the TA value, ID information of the corresponding candidate cell, or ID information of UE 701 to source DU 702 via CU 704.

[0149] In operation 718 , the source DU 702 may transmit the TA value and the ID information of the corresponding candidate cell to the UE 701 .

[0150] Figure 8 Another exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application is illustrated. The details described in all other embodiments of the present application apply to Figure 8 The embodiments shown in .

[0151] like Figure 8 As shown in FIG. 8 , BS 805 has a CU-DU architecture and includes CU 804, source DU 802, and candidate DU 803. Figure 8 In the embodiment of , the cell switching operation performed by UE 801 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. Figure 8 The flowchart 800 shown in FIG. 8 only shows the cell switching operation in the inter-DU scenario for exemplary purposes. If the source DU 802 and the candidate DU 803 are the same DU, the flowchart 800 can also be applied to the intra-DU scenario.

[0152] In such Figure 8 In the exemplary flowchart 800 shown in FIG. 8 , in operation 811, UE 801 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 805). 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. There is an F1 interface between the DU and the CU. For example, Figure 8 , BS 805 includes CU 804, source DU 802, and candidate DU 803. BS 805 may include one or more other candidate DUs ( Figure 8 not shown).

[0153] In operation 812 , the UE 801 receives an RRCReconfiguration message associated with one or more candidate cells for LTM purposes from the CU 804 via the source DU 802 .

[0154] In some embodiments, CU 804 determines to initiate L1 / L2-based inter-cell mobility configuration. CU 804 may receive a message including an RRCReconfiguration message from candidate DU 803 via an F1 interface. Then, CU 804 may transmit an RRCReconfiguration message from candidate DU 803 to UE 801 via source DU 802.

[0155] In some embodiments, if the configuration information transmitted from CU 804 to source DU 802 includes instructions for instructing a TA reacquisition procedure (e.g., as in Figure 6 If the source DU 802 has an indication #7 described in the embodiment of the present invention and / or RACH configuration information for the TA re-acquisition procedure, the source DU 802 may transmit an indication to the candidate DU 803 that the TA re-acquisition procedure is to be triggered (e.g., as in Figure 6Instruction #8) described in the embodiments.

[0156] In operation 813, UE 801 receives information to trigger a TA acquisition procedure or a TA re-acquisition procedure for a candidate cell within one or more candidate cells (e.g., as in Figure 3 In some embodiments, the information may be DCI, MAC CE or RRC signaling. If the information is DCI, it may be a PDCCH command.

[0157] In operation 814, the UE 801 may transmit a preamble for a TA acquisition or TA reacquisition procedure.

[0158] In operation 815, if the candidate DU 803 fails to receive the preamble in the configured RO, the candidate DU 803 may determine the failure of the TA calculation. Then, in operation 816, the candidate DU 80 may transmit a message to the CU 804 (e.g., as in Figure 4 Message #1 described in the embodiment). In an embodiment, the message may be a UL RRC message transmission message or a UE context modification request message.

[0159] The message transmitted in operation 816 may include an indication indicating that TA acquisition or TA reacquisition has failed (e.g., as in Figure 4 In some embodiments, the RACH configuration for TA acquisition or TA reacquisition may include at least one of the following:

[0160] (1) RA preamble index.

[0161] (2) SS / PBCH Index This field may indicate the SS / PBCH to be used to determine the RACH opportunity for PRACH transmission.

[0162] (3) RO as a time-frequency domain resource for preamble transmission. For example, the field "PRACH mask index" indicates a RACH opportunity (RO) associated with the SS / PBCH indicated by the "SS / PBCH index" for PRACH transmission.

[0163] In some embodiments, before transmitting a message to the CU 804 in operation 816 , the candidate DU 803 needs to request the source DU 802 to provide the latest measurement result via the CU 804 .

[0164] In operation 817, CU 804 may transmit a message including the configuration received from candidate DU 803 to source DU 802. The configuration may include an indication of a TA acquisition or TA reacquisition procedure (e.g., Figure 4 Indication #5) described in the embodiment of the present invention and RACH configuration information used for the TA re-acquisition procedure (e.g., corresponding to RACH resources).

[0165] In operation 818, the source DU 802 transmits information to the candidate cell to trigger a TA acquisition or TA reacquisition procedure (e.g., as in Figure 3 Instruction #1) described in the embodiments.

[0166] In some embodiments, if UE 801 receives a PDCCH order for the same candidate cell (eg, the PDCCH order includes a cell index), UE 801 may transmit a preamble at a higher power than the previously transmitted preamble. For example, UE 801 may increase PREAMBLE_POWER_RAMPING_COUNTER by 1.

[0167] In operation 819, once the source DU 802 decides to perform LTM on the candidate target cell, i.e., to perform a cell switching procedure on the candidate target cell, the source DU 802 may transmit a cell switching command (e.g., a MAC CE including a candidate cell configuration index) to the UE 801 to trigger the cell switching procedure. In some embodiments, the cell switching command (e.g., DCI, MAC CE, or RRC signaling) is used to trigger the UE 801 to perform a TA acquisition or TA reacquisition procedure.

[0168] In operation 820, after the UE 801 receives the cell switching command from the source DU 802, the UE 801 may perform a cell switching procedure and synchronize to the candidate target cell, for example, perform UL synchronization and / or DL ​​synchronization operations on the candidate target cell.

[0169] Fig. 9 Another exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application is illustrated. The details described in all other embodiments of the present application apply to Fig. 9 The embodiments shown in .

[0170] like Fig. 9 As shown in FIG. 1 , BS 905 has a CU-DU architecture and includes CU 904, source DU 902, and candidate DU 903. Fig. 9 In the embodiment of , the cell change of UE 901 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. Fig. 9 The flowchart 900 shown in FIG. 9 shows only the cell change in the inter-DU scenario for exemplary purposes. If the source DU 902 and the candidate DU 903 are the same DU, the flowchart 900 can be applied to the intra-DU scenario.

[0171] In such Fig. 9 In the exemplary flowchart 900 shown in FIG. 1 , in operation 911, UE 901 may access a serving BS (e.g., a gNB) and send a measurement report to the serving BS (e.g., BS 905). 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. There is an F1 interface between the DU and the CU. For example, Fig. 9 , BS 905 includes CU 904, source DU 902, and candidate DU 903. BS 905 may include one or more other candidate DUs ( Fig. 9 not shown).

[0172] In operation 912, the UE 901 receives an RRCReconfiguration message associated with one or more candidate cells for LTM purposes.

[0173] In some embodiments, CU 904 may determine to initiate L1 / L2 based inter-cell mobility configuration. CU 904 will receive a message including an RRCReconfiguration message from candidate DU 903 via the F1 interface. Then, CU 904 may transmit the RRCReconfiguration message from candidate DU 903 to UE 901 via source DU 902.

[0174] In some embodiments, if the configuration information transmitted from the CU 904 to the source DU 902 includes instructions for instructing the TA re-acquisition procedure (e.g., as in Figure 6 If the source DU 902 has an indication #7 described in the embodiment of the present invention and / or RACH configuration information for the TA re-acquisition procedure, the source DU 902 may transmit an indication to the candidate DU 903 that the TA re-acquisition procedure is to be triggered (e.g., as in Figure 6 Instruction #8) described in the embodiments.

[0175] In operation 913, the UE 901 receives information to trigger a TA acquisition procedure or a TA re-acquisition procedure for a candidate cell within one or more candidate cells (e.g., Figure 3 Indication #1 described in the embodiment of the present invention). The information may be DCI, MAC CE or RRC signaling. If the information is DCI, it may be a PDCCH command.

[0176] In operation 914, the UE 901 may transmit a preamble for a TA acquisition or TA reacquisition procedure.

[0177] In operation 915, if the source DU 902 fails to receive a TA value from the corresponding candidate cell, the source DU 902 may determine that TA acquisition has failed.

[0178] In some embodiments, if the source DU 902 fails to receive the TA value within a certain period of time, the source DU 902 may determine that the TA acquisition has failed. In an embodiment, the source DU 902 may start a timer immediately after the PDCCH command transmission or RO. After the timer expires, the source DU 902 may immediately determine that the TA acquisition has failed.

[0179] In operation 916, after the source DU 902 determines that the TA acquisition fails, the source DU 902 may transmit at least one of the following to the CU 904:

[0180] (1) An indication of a failure to obtain a TA value (e.g., Figure 5 The indication may also be referred to as "an indication of failure to obtain a TA value" or "an indication for indicating a failure to obtain a TA value", etc. In some embodiments, the indication may be carried in a UL RRC message transmission message or a UE context modification request message.

[0181] (2) ID information of candidate cells.

[0182] (3) Measurement results of UE 901 , for example, L1 measurement results of UE 901 .

[0183] In operation 917, the CU 904 may transmit an indication of a failure to obtain a TA value to the candidate DU 903 (e.g., as in Figure 4 In some embodiments, the CU 904 transmits the indication of the failure to obtain the TA value received from the source DU 902 in operation 916 to the candidate DU 903. In some other embodiments, the CU 904 may also determine that the TA acquisition has failed, for example, if the CU 904 does not receive the TA value after a certain period of time (for example, after a timer expires), the CU 904 may determine that the TA acquisition has failed. Then, the CU 904 transmits the indication of the failure to obtain the TA value to the candidate DU 903.

[0184] In operation 918, the candidate DU 903 may transmit a RACH configuration for TA acquisition or TA reacquisition (e.g., RACH resources) to the source DU 902 via the CU 904. In some embodiments, the RACH configuration includes at least one of the following:

[0185] (1) RA preamble index.

[0186] (2) SS / PBCH Index This field may indicate the SS / PBCH to be used to determine the RACH opportunity for PRACH transmission.

[0187] (3) RO as a time-frequency domain resource for preamble transmission. For example, the field "PRACH mask index" indicates a RACH opportunity (RO) associated with the SS / PBCH indicated by the "SS / PBCH index" for PRACH transmission.

[0188] In operation 919, once the source DU 902 decides to perform LTM on the candidate target cell, ie, to perform a cell switching procedure on the candidate target cell, the source DU 902 may transmit a cell switching command (eg, a MAC CE including a candidate cell configuration index) to the UE 801 to trigger the cell switching procedure.

[0189] In some embodiments, a cell switching command (eg, DCI, MAC CE, or RRC signaling) is used to trigger UE 901 to perform a TA acquisition or TA reacquisition procedure.

[0190] In operation 920, after the UE 901 receives the cell switching command from the source DU 902, the UE 901 may perform a cell switching procedure and synchronize to the candidate target cell, for example, perform UL synchronization and / or DL ​​synchronization operations on the candidate target cell.

[0191] Fig.10 Another exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application is illustrated. The details described in all other embodiments of the present application apply to Fig.10 The embodiments shown in .

[0192] like Fig.10 As shown in FIG. 1 , BS 1005 has a CU-DU architecture and includes CU 1004, source DU 1002, and candidate DU 1003. Fig.10 In the embodiment of , the cell change of 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. Fig.10 The flowchart 1000 shown in FIG. 1 only shows the cell change in the inter-DU scenario for exemplary purposes. If the source DU 1002 and the candidate DU 1003 are the same DU, the flowchart 1000 can be applied to the intra-DU scenario.

[0193] In such Fig.10In the exemplary flowchart 1000 shown in FIG. 1001 , 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. There is an F1 interface between the DU and the CU. For example, Fig.10 , BS 1005 includes CU 1004, source DU 1002, and candidate DU 1003. BS 1005 may include one or more other candidate DUs ( Fig.10 not shown).

[0194] In operation 1012 , the UE 1001 receives an RRCReconfiguration message associated with one or more candidate cells for LTM purposes from the CU 1004 via the source DU 1002 .

[0195] In some embodiments, CU 1004 may determine to initiate L1 / L2 based inter-cell mobility configuration. CU 1004 will receive a message including an RRCReconfiguration message from the candidate cell via the F1 interface. Then, CU 1004 may transmit the RRCReconfiguration message from the candidate cell to UE 1001 via source DU 1002.

[0196] In some embodiments, if the configuration information transmitted from CU 1004 to source DU 1002 includes instructions for instructing a TA reacquisition procedure (e.g., as in Figure 6 If the source DU 1002 has an indication #7 described in the embodiment of the present invention and / or RACH configuration information for the TA reacquisition procedure, the source DU 1002 may transmit an indication to the candidate DU 1003 to trigger the TA reacquisition procedure (e.g., as in Figure 6 Instruction #8) described in the embodiments.

[0197] In operation 1013, the UE 1001 receives information to trigger a TA acquisition procedure or a TA re-acquisition procedure for a candidate cell within one or more candidate cells (e.g., Figure 3 Indication #1 described in the embodiments of the present invention). In some embodiments, the information may be DCI (e.g., PDCCH command), MAC CE or RRC signaling.

[0198] In operation 1014, UE 1001 performs an RA procedure to obtain a TA value (which may be referred to as an "early TA value", etc.). In some embodiments, UE 1001 may transmit a preamble once. In some other embodiments, UE 1001 may transmit a preamble several times, which is configurable. In addition, the number of times may be a maximum number of preamble transmissions. Once the maximum number of preamble transmissions is reached and no RAR is received, UE 1001 may consider that the TA acquisition procedure has failed, i.e., TA acquisition has failed.

[0199] In some embodiments, a conflict may occur between "UL transmission (e.g., SR) triggered by UE 1001 in the serving cell" and "RO of the candidate cell for the TA acquisition or reacquisition procedure triggered by the information received in operation 1013". The RO of the candidate cell may have a higher priority than the UL transmission in the serving cell.

[0200] In some embodiments, when UE 1001 receives a PDCCH command for triggering TA acquisition and UE 1001 is initiating RA in a serving cell (for example, the UL is no longer synchronized immediately after UL data arrives in the serving cell), there may be the following two options in different embodiments, namely Option X and Option Y.

[0201] (1) Option X: If two parallel RA procedures are allowed, then UE 1001 may perform two RA procedures. However, RACH timings may conflict between the two RA procedures. If RACH timings conflict, then one of the two RA procedures should be prioritized. For example, the preamble used for TA acquisition in the RACH timing of the candidate cell should be prioritized.

[0202] (2) Option Y: If two parallel RA procedures are not allowed, one of the two RA procedures should be prioritized. For example, the preamble used for TA acquisition in the RACH opportunity of the candidate cell should be prioritized. The RA procedure for UL synchronization in the serving cell of UE 701 may be suspended. When the RA procedure for TA acquisition is completed, UE 701 may continue the RA procedure for UL synchronization in the serving cell.

[0203] In some embodiments, UE 1001 may fail to obtain a TA value via a RA procedure. For example, UE 1001 does not receive a RAR after transmitting a preamble. After UE 1001 fails to obtain a TA value via a RA procedure, UE 1001 may report failure information to the network. In some embodiments, UE 1001 reports failure information to source DU 1002, for example, via MAC CE. In some other embodiments, UE 1001 reports failure information to CU 1004 via source DU 1002 (e.g., via RRC signaling). Then, CU 1004 may indicate at least one of the following: TA acquisition failure, or requesting candidate DU 1003 to update RACH configuration, such as new beam information and measurement results. Specifically, there may be the following two options, namely Option M and Option N, in the following different embodiments:

[0204] (1) Option M: Perform operations 1015A, 1016A, 1017, 1018, 1019, and 1020.

[0205] In operation 1015A, UE 1001 reports the failure information to source DU 1002 via MAC CE. In operation 1016A, source DU 1002 indicates the failure of TA acquisition or TA re-acquisition procedure to CU 1004 via F1 interface (e.g., as in Figure 6 Indication #9 described in the embodiment of the present invention). The measurement result may be transmitted to the CU 1004 together with the failure information. In operation 1017, the CU 1004 requests the candidate DU 1003 to update the RACH configuration, such as new beam information. The measurement result may also be transmitted to the candidate DU 1003. In operation 1018, the candidate DU 1003 prepares a new or updated RACH configuration for TA reacquisition based on the received measurement result and transmits the updated RACH configuration to the CU 1004. In operation 1019, the CU 1004 transmits the updated RACH configuration to the source DU 1002. In operation 1020, after the source DU 1002 receives the updated RACH configuration, the source DU 1002 transmits an indication of a TA reacquisition procedure associated with the candidate cell to the UE 1001 (e.g., as in Figure 3 For example, in operation 1020, the source DU 1002 transmits a PDCCH command to the UE 1001 again.

[0206] (2) Option N: Execute operations 1015B, 1017, 1018, 1019, and 1020.

[0207] In operation 1015B, UE 1001 reports the failure information to CU 1004 via RRC signaling. In operation 1017, CU 1004 transmits at least one of the following to candidate DU 1003: an indication of TA acquisition failure (e.g., as in Figure 4 In operation 1018, the candidate DU 1003 prepares a new or updated RACH configuration for TA reacquisition based on the received measurement result and transmits the updated RACH configuration to the CU 1004. In operation 1019, the CU 1004 transmits the updated RACH configuration to the source DU 1002. In operation 1020, after the source DU 1002 receives the updated RACH configuration, the source DU 1002 transmits an indication for a TA reacquisition procedure associated with the candidate cell to the UE 1001 (e.g., as in Figure 3 For example, in operation 1020, the source DU 1002 transmits a PDCCH command to the UE 1001 again.

[0208] In operation 1021 , the UE 1001 will perform a RA procedure for TA reacquisition after receiving a PDCCH order from the source DU 1002 .

[0209] In operation 1022, once the source DU 1002 decides to perform LTM on the candidate target cell, that is, to perform a cell switching procedure on the candidate target cell, the source DU 1002 may transmit a cell switching command (e.g., a MAC CE including a candidate cell configuration index) to the UE 1001 to trigger the cell switching procedure. In some embodiments, the cell switching command (e.g., DCI, MAC CE, or RRC signaling) is used to trigger the UE 1001 to perform a TA acquisition or TA reacquisition procedure.

[0210] In operation 1023, after the UE 1001 receives the cell switching command from the source DU 1002, the UE 1001 may perform a cell switching procedure and synchronize to the candidate target cell, for example, perform UL synchronization and / or DL ​​synchronization operations on the candidate target cell.

[0211] Fig.11 The block diagram of an exemplary device 1100 is illustrated according to some embodiments of the present application. Fig.11, the apparatus 1100 may include at least one processor 1106 and at least one transceiver 1102 coupled to the processor 1106. Although in this figure, elements such as at least one transceiver 1102 and processor 1106 are described in singular form, plural forms are also considered unless limitation to the singular form is explicitly stated. In some embodiments of the present application, the transceiver 1102 may be divided into two devices, such as a receiving circuit and a transmitting circuit. In some embodiments of the present application, the apparatus 1100 may further include an input device, a memory, and / or other components.

[0212] In some embodiments of the present application, the device 1100 may be a UE or a network node (eg, a BS, a CU, or a DU). The transceiver 1102 and the processor 1106 may interact with each other to execute the above, for example, Figures 1 to 10 The operations of the UE or the network node described in any one of the foregoing.

[0213] In some embodiments of the present application, the device 1100 may further include at least one non-transitory computer-readable medium. For example, in some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1106 to implement the method described above with respect to the UE or network node (e.g., BS, CU, or DU). For example, when the computer-executable instructions are executed, the processor 1106 interacting with the transceiver 1102 executes Figures 1 to 10 The operations of the UE or network node described in.

[0214] Those skilled in the art will appreciate that the operations or steps of the methods described in conjunction with the various aspects disclosed herein may be directly embodied in hardware, a software module executed by a processor, or a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the operations or steps of the methods may reside as one or any combination or set of codes and / or instructions on a non-transitory computer-readable medium, which may be incorporated into a computer program product.

[0215] In this document, the term "includes, including" or any other variations thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements does not only include those elements, but may include other elements that are not explicitly listed or inherent to this process, method, article or equipment. Without more constraints, the elements starting with "a, an" etc. do not exclude the existence of additional identical elements in the process, method, article or equipment comprising the elements. In addition, the term "another" is defined as at least the second or more. As used herein, the term "having" etc. is defined as "including". For example, expressions such as "A and / or B" or "at least one of A and B" may include any and all combinations of words listed together with the expression. For example, expressions such as "A and / or B" or "at least one of A and B" may include A, B or both A and B. The wordings "first", "second" etc. are only used to clearly illustrate the embodiments of the application, rather than to limit the essence of the application.

Claims

1. A candidate distributed unit DU of a base station BS, comprising: Transceiver; as well as a processor coupled to the transceiver, wherein the processor is configured to cause the candidate DU to: receiving, from a centralized unit CU of the BS, a request for a cell switching procedure associated with a candidate cell; and A response including configuration information associated with the candidate cell is transmitted to the CU based on the request.

2. The candidate DU of claim 1, wherein the processor is configured to cause the candidate DU to: receiving a preamble for a timing advance TA acquisition procedure or a TA reacquisition procedure; calculating a TA value based on the received preamble; and At least one of the TA value, the identifier ID information of the candidate cell, or the ID information of the user equipment UE is transmitted to the CU.

3. The candidate DU of claim 1 , wherein the processor is configured to cause the candidate DU to receive at least one of the following from the CU: A first indication for indicating a failure of a TA acquisition procedure or a TA re-acquisition procedure; a request for random access channel (RACH) configuration information for said TA acquisition procedure or said TA re-acquisition procedure; or Measurement results of user equipment UE.

4. The candidate DU of claim 1 , in response to failure to receive a preamble for a TA acquisition procedure or a TA re-acquisition procedure in a RACH opportunity RO, the processor is configured to cause the candidate DU to determine a failure of the TA acquisition procedure or the TA re-acquisition procedure.

5. The candidate DU according to claim 3 or claim 4, in response to receiving the first indication from the CU or in response to determining the failure of the TA acquisition procedure or the TA re-acquisition procedure, the processor is configured to cause the candidate DU to transmit a first message to the CU, wherein the first message includes at least one of the following: Identifier ID information of a candidate cell associated with the TA acquisition procedure or the TA re-acquisition procedure; ID information of the UE; a second indication for indicating the failure of the TA acquisition procedure or the TA re-acquisition procedure; a request for measurement results of the UE; a third indication for indicating the TA reacquisition procedure; or The RACH configuration information used for the TA acquisition procedure or the TA re-acquisition procedure.

6. The candidate DU according to claim 1, wherein the response comprises a random access channel (RACH) resource for a timing advance (TA) acquisition procedure, and the RACH resource comprises a preamble or a RACH opportunity (RO).

7. A centralized unit CU of a base station BS, comprising: Transceiver; as well as a processor coupled to the transceiver, wherein the processor is configured to cause the CU to: Transmitting a request to a candidate distributed unit DU of the BS, wherein the request includes identifier ID information of one or more candidate cells; receiving a response corresponding to the request from the candidate DU, wherein the response is associated with a cell handover procedure; and First configuration information is transmitted to a user equipment UE via a source DU of the BS based on the response.

8. The CU of claim 7, wherein the processor is configured to cause the CU to receive second configuration information from the candidate DU, the second configuration information comprising at least one of: a TA value calculated for a timing advance TA acquisition procedure or a TA reacquisition procedure; ID information of a candidate cell associated with the TA acquisition procedure or the TA reacquisition procedure; ID information of the UE; a first indication for indicating a failure of the TA acquisition procedure or the TA re-acquisition procedure; a request for measurement results of the UE; a second indication for indicating the TA reacquisition procedure; or Random Access Channel (RACH) configuration information used for the TA reacquisition procedure. 9 . The CU of claim 8 , after receiving the second configuration information from the candidate DU, the processor is configured to cause the CU to transmit the second configuration information to the source DU.

10. The CU of claim 7, wherein the processor is configured to cause the CU to receive second information from the source DU, and wherein the second information includes at least one of: a third indication for indicating a failure of a TA acquisition procedure or a TA re-acquisition procedure; ID information of a candidate cell associated with the TA acquisition procedure or the TA re-acquisition procedure; or The layer 1 measurement result of the UE. The CU according to claim 10 , wherein the second information is received by the source DU from the UE.

12. The CU of claim 10, the processor being configured to cause the CU to transmit at least one of the following to the candidate DU: a fourth indication for indicating the failure of the TA acquisition procedure or the TA re-acquisition procedure; or The layer 1 measurement result of the UE.

13. The CU of claim 7, wherein the processor is configured to cause the CU to: receiving, from the UE, failure information related to a TA acquisition procedure or a TA re-acquisition procedure; and Transmitting at least one of the following to the candidate DU: a fifth indication for indicating a failure of the TA acquisition procedure or the TA re-acquisition procedure; or A request for random access channel (RACH) configuration information for the TA acquisition procedure or the TA re-acquisition procedure.

14. A user equipment UE, comprising: Transceiver; as well as a processor coupled to the transceiver, wherein the processor is configured to cause the UE to: receiving radio resource control (RRC) configuration information associated with one or more candidate cells, the one or more candidate cells being related to a cell handover procedure; and A first indication is received to trigger a timing advance TA acquisition procedure or a TA re-acquisition procedure for a first candidate cell among the one or more candidate cells before performing the cell switching procedure.

15. The UE of claim 14, wherein the processor is configured to cause the UE to: determining whether a collision occurs between an uplink (UL) transmission in a serving cell of the UE and a random access channel opportunity (RO) in a candidate cell among the one or more candidate cells, wherein the RO is associated with the TA acquisition procedure or the TA re-acquisition procedure; and In response to the conflict, the TA acquisition procedure or the TA re-acquisition procedure associated with the RO is performed.

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