Method and device for TA acquisition

Abstract

The embodiment of the invention relates to a method and equipment for early timing advance (TA) acquisition. In accordance with some embodiments of the present disclosure, a first distributed unit (DU) of a base station (BS) may: receive, from a centralized unit (CU) of the BS, configuration information regarding early TA acquisition of candidate cells for cell exchange; and transmitting a physical downlink control channel (PDCCH) command associated with the candidate cell to a user equipment (UE) served by the first DU, where the PDCCH command triggers the UE to transmit a signal (e.g., a preamble) to the candidate cell via a configured random access channel (RACH) occasion.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to wireless communication techniques, and more particularly to methods and apparatus for timing advance (TA) acquisition. Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services, such as telephony, video, data, messaging, broadcasts, and the like. 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 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] There is a need to handle TA acquisition in wireless communication systems. Summary of the Invention

[0004] Some embodiments of the present disclosure provide a first distributed unit (DU) of a base station (BS). The first DU may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: receive configuration information about early timing advance (TA) acquisition for a candidate cell for cell switching from a centralized unit (CU) of the BS; and transmit a physical downlink control channel (PDCCH) command associated with the candidate cell to a user equipment (UE) served by the first DU, wherein the PDCCH command triggers the UE to transmit a signal (e.g., a preamble) to the candidate cell. For example, the signal (e.g., a preamble) may be transmitted via a configured random access channel (RACH) opportunity.

[0005] In some embodiments, the processor may be further configured to, in response to transmitting the PDCCH command: receive a TA value related to the candidate cell from the candidate cell; and perform one of the following: receive a first indication from the candidate cell indicating whether the TA value will be transmitted to the UE via a random access response (RAR), a medium access control (MAC) control element (CE), or a cell exchange command, and transmit the TA value to the UE according to the first indication; if the first DU does not receive the first indication, transmit the TA value to the UE via the cell exchange command; receive a second indication from the CU indicating whether the TA value will be transmitted to the UE via the RAR, a MAC CE, or the cell exchange command, and transmit the TA value to the UE according to the second indication; if the first DU does not receive the second indication, transmit the TA value to the UE via the cell exchange command; if the first DU receives RAR-related information from the CU or the candidate cell, transmit the TA value to the UE via the RAR; or if the first DU does not receive any RAR-related information, transmit the TA value to the UE via the cell exchange command.

[0006] In some embodiments, the processor may be further configured to receive RAR-related information from a candidate DU via the CU, or configure the RAR-related information for the UE; and transmit the RAR-related information to the UE from a serving cell of the UE to monitor a RAR carrying a TA value.

[0007] In some embodiments, the RAR-related information may include a length of a RAR window used to monitor the RAR, an offset associated with the RAR window, or both.

[0008] In some embodiments, the processor may be further configured to: receive a TA value related to the candidate cell from the candidate cell in response to transmitting the PDCCH command; and transmit the TA value to the UE via the RAR using one of a cell radio network temporary identifier (C-RNTI), a random access RNTI (RA-RNTI), or a specific RNTI associated with the UE's serving cell.

[0009] In some embodiments, in a scenario where the first DU is instructed to transmit a TA value related to the candidate cell to the UE via the RAR while the first DU transmits a cell exchange command related to the candidate cell to the UE, the processor may be further configured to: transmit the cell exchange command including the TA value and skip the transmission of the RAR; transmit the cell exchange command without the TA value and skip the transmission of the RAR; or multiplex the cell exchange command and the RAR into the same MAC layer data unit.

[0010] Some embodiments of the present disclosure provide a user equipment (UE). The UE may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: receive a physical downlink control channel (PDCCH) command associated with a candidate cell for cell switching; transmit a signal (e.g., a preamble) to the candidate cell in response to receiving the PDCCH command; and receive a timing advance (TA) value associated with the candidate cell via a first distributed unit (DU) of a base station (BS), wherein the UE is served by the first distributed unit.

[0011] In some embodiments, the processor may be further configured to receive RAR-related information from a CU of the BS or the first DU, wherein the RAR-related information is configured by the candidate cell or the first DU.

[0012] In some embodiments, the RAR-related information may include the length of a RAR window used to monitor the RAR carrying the TA value, an offset associated with the RAR window, or both. In some embodiments, a start time of the RAR window is based on the offset, and a duration of the RAR window is based on the length of the RAR window. In some embodiments, the duration of the RAR window is based on the offset and the length of the RAR window.

[0013] In some embodiments, the processor may be further configured to, in response to successfully receiving the TA value, transmit an indication of successful receipt of the TA value to the BS. In some embodiments, the processor may be further configured to, in response to unsuccessfully receiving the TA value, transmit an indication of unsuccessfully receiving the TA value to the BS. In some embodiments, the indication may be transmitted via an L1 indication, a MAC CE, or an RRC message.

[0014] In some embodiments, the TA value may be received via an RAR. In some embodiments, the UE does not expect to receive another TA value associated with the candidate cell in a cell switch command associated with the candidate cell. In some embodiments, the processor may be further configured to receive the another TA value in the cell switch command and replace the TA value stored at the UE with the another TA value.

[0015] In some embodiments, the processor may be further configured to: receive another PDCCH command associated with the candidate cell, wherein the another PDCCH command triggers TA reacquisition; and delete the stored TA value related to the candidate cell in response to receiving the another PDCCH command.

[0016] In some embodiments, the processor may be further configured to: receive a RACH configuration for early TA acquisition associated with the candidate cell from the BS; and perform a compliance check on the RACH configuration.

[0017] In some embodiments, the compliance check may be performed in response to the receiving of the RACH configuration or in response to the receiving of the PDCCH order.

[0018] In some embodiments, the processor may be further configured to report failure information indicating one of the following to the BS in response to the failure of the compliance check: compliance check failure, reconfiguration failure, reference configuration failure, RACH configuration failure for early TA acquisition, and full lower layer triggered mobility (LTM) configuration failure.

[0019] In some embodiments, the TA value may be received via the RAR using a C-RNTI, a RA-RNTI, or a specific RNTI associated with a serving cell of the UE.

[0020] Some embodiments of the present disclosure provide a second distributed unit (DU) of a base station (BS). The second DU may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: receive a request for cell exchange associated with a candidate cell from a centralized unit (CU) of the BS; transmit a response to the CU, wherein the response may include configuration information associated with the candidate cell; receive a signal (e.g., a preamble) for early timing advance (TA) acquisition associated with the candidate cell from a user equipment (UE) served by a first DU of the BS; and transmit a TA value associated with the candidate cell to the first DU via the CU in response to receiving the signal.

[0021] In some embodiments, the request may indicate whether to use RAR, MAC CE, or cell switch command to carry the TA value.

[0022] In some embodiments, the processor may be further configured to transmit, in response to said receiving the signal, a first indication indicating whether the TA value is to be transmitted to the UE via a RAR, a MAC CE, or a cell switch command.

[0023] In some embodiments, the response may further include a length of a RAR window used to monitor the RAR carrying the TA value, an offset associated with the RAR window, or both.

[0024] In some embodiments, a start time of the RAR window is based on the offset, and a duration of the RAR window is based on the length of the RAR window. In some embodiments, the duration of the RAR window is based on the offset and the length of the RAR window.

[0025] Some embodiments of the present disclosure provide a method performed by a first distributed unit (DU) of a base station (BS). The method may include: receiving configuration information regarding early timing advance (TA) acquisition for a candidate cell for cell switching from a centralized unit (CU) of the BS; and transmitting a physical downlink control channel (PDCCH) command associated with the candidate cell to a user equipment (UE) served by the first DU, wherein the PDCCH command triggers the UE to transmit a signal to the candidate cell.

[0026] Some embodiments of the present disclosure provide a method performed by a user equipment (UE). The method may include: receiving a physical downlink control channel (PDCCH) command associated with a candidate cell for cell switching; transmitting a signal to the candidate cell in response to receiving the PDCCH command; and receiving a timing advance (TA) value associated with the candidate cell via a first distributed unit (DU) of a base station (BS), wherein the UE is served by the first DU.

[0027] Some embodiments of the present disclosure provide a method performed by a second distributed unit (DU) of a base station (BS). The method may include: receiving a request for cell exchange associated with a candidate cell from a centralized unit (CU) of the BS; transmitting a response to the CU, wherein the response may include configuration information associated with the candidate cell; receiving a signal for early timing advance (TA) acquisition associated with the candidate cell from a user equipment (UE) served by a first DU of the BS; and transmitting, via the CU, a TA value associated with the candidate cell to the first DU in response to receiving the signal.

[0028] Some embodiments of the present disclosure provide an apparatus. According to some embodiments of the present disclosure, the apparatus may include: at least one non-transitory computer-readable medium having computer-executable instructions stored thereon; at least one receiving circuit system; at least one transmitting circuit system; and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving circuit system, and the at least one transmitting circuit system, wherein the at least one non-transitory computer-readable medium and the computer-executable instructions may be configured to cause the apparatus to perform a method according to some embodiments of the present disclosure using the at least one processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to describe the manner in which the advantages and features of the present disclosure can be obtained, the description of the present disclosure is presented by reference to specific embodiments of the present disclosure which are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present disclosure and therefore should not be considered to limit the scope of the present disclosure.

[0030] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present disclosure;

[0031] Figure 2 A schematic diagram illustrating an exemplary BS according to some embodiments of the present disclosure;

[0032] Figures 3 to 6 A flowchart illustrating an exemplary process for early TA acquisition according to some embodiments of the present disclosure;

[0033] Figures 7 to 9 a flowchart illustrating an exemplary process for wireless communication according to some embodiments of the present disclosure; and

[0034] Figure 10 Illustrated is a block diagram of an exemplary apparatus according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0035] The detailed description of the accompanying drawings is intended to be a description of the preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure can be practiced. It should be understood that the same or equivalent functions can be achieved by different embodiments that are intended to be encompassed within the spirit and scope of the present disclosure.

[0036] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. To facilitate understanding, the embodiments are provided in the context of specific network architectures and new services, such as 3rd Generation Partnership Project (3GPP) 5G (NR), 3GPP Long Term Evolution (LTE) Release 8, etc. Please note that as network architectures and new service scenarios develop, all embodiments of the present disclosure are also applicable to similar technical problems; and further, the terminology described in the present disclosure may change, which should not affect the principles of the present disclosure.

[0037] Figure 1 A schematic diagram illustrating a wireless communication system 100 is illustrated in accordance with some embodiments of the present disclosure.

[0038] like Figure 1 As shown in FIG, a wireless communication system 100 may include some UEs 101 (e.g., UE 101a and UE 101b) and a base station (e.g., BS 102). Figure 1 A specific number of UEs 101 and BSs 102 are depicted in FIG. 1 , but please consider that any number of UEs and BSs may be included in the wireless communication system 100 .

[0039] UE 101 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), an in-vehicle computer, a network device (e.g., a router, a switch, and a modem), etc. According to some embodiments of the present disclosure, UE 101 may include a portable wireless communication device, a smartphone, 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 over a wireless network. In some embodiments of the present disclosure, UE 101 includes a wearable device such as a smartwatch, a fitness tracker, an optical head-mounted display, etc. UE 101 may also 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 other terms used in the art to describe the device. UE 101 may communicate with BS 102 via uplink (UL) communication signals.

[0040] BSs 102 may be distributed throughout a geographic area. In certain embodiments of the present disclosure, BSs 102 may also be referred to as access points, access terminals, base stations, base units, macrocells, Node Bs, evolved Node Bs (eNBs), gNBs, Home Node Bs, relay nodes, or devices, or may be described using other terms used in the art. BSs 102 are typically part of a radio access network, which may include one or more controllers communicatively coupled to one or more corresponding BSs 102. BSs 102 may communicate with UEs 101 via downlink (DL) communication signals.

[0041] The wireless communication system 100 may be compatible with any type of network capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 may be compatible with a wireless communication network, a cellular telephone network, a time division multiple access (TDMA)-based network, a code division multiple access (CDMA)-based network, an orthogonal frequency division multiple access (OFDMA)-based network, an LTE network, a 3GPP-based network, a 3GPP 5G network, a satellite communication network, a high altitude platform network, and / or other communication networks.

[0042] In some embodiments of the present disclosure, the wireless communication system 100 may be compatible with the 5G NR of the 3GPP protocol. For example, the BS 102 may transmit data using an orthogonal frequency division multiplexing (OFDM) modulation scheme on the DL, and the UE 101 may transmit data using a discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) or cyclic prefix-OFDM (CP-OFDM) scheme on the UL. However, in general, the wireless communication system 100 may implement some other open or proprietary communication protocols, such as WiMAX and other protocols.

[0043] In some embodiments of the present disclosure, BS 102 and UE 101 may communicate using other communication protocols (e.g., the IEEE 802.11 series of wireless communication protocols). Furthermore, in some embodiments of the present disclosure, BS 102 and UE 101 may communicate via a licensed spectrum, while in some other embodiments, BS 102 and UE 101 may communicate via an unlicensed spectrum. The present disclosure is not intended to be limited to implementations of any particular wireless communication system architecture or protocol.

[0044] In some embodiments of the present disclosure, a BS (e.g., Figure 1 The BS 102 in FIG. 1 may include a CU (also referred to as a BS-CU) and one or more DUs (also referred to as a BS-DU). For example, Figure 2 , BS 202 may include CU 203, DU 204, and DU 205. Please consider that in some other embodiments of the present disclosure, BS 202 may include more or fewer DUs.

[0045] Each of DU 204 and DU 205 may include one or more cells, which may also be referred to as cells of BS 202. DU 204 and DU 205 may communicate with CU 203 via an F1 interface.

[0046] UE (not shown) Figure 2 202 is accessible to the UE. That is, BS 202 is the serving BS of the UE. The UE may have one or more serving cells, which may belong to the same or different DUs. For example, the serving cell of the UE may be the cell of DU 204. In this example, DU 204 may be referred to as the serving DU of the UE.

[0047] In some embodiments of the present disclosure, a communication system (e.g., NR) may support inter-cell mobility based on layer 1 / layer 2 (L1 / L2), which may also be referred to as "lower layer triggered mobility (LTM)".

[0048] For example, a UE may access a BS (i.e., a serving BS). The UE may report Layer 3 (L3, such as radio resource control (RRC)) measurement results based on the configuration from the serving BS. The BS (e.g., a CU of the BS) may decide to switch the UE to a candidate cell based on the measurement results. In some instances, the candidate cell of the UE and the current serving cell may belong to the same DU of the serving BS (i.e., intra-DU cell switching). In some instances, the candidate cell of the UE and the current serving cell may belong to different DUs of the serving BS (i.e., inter-DU cell switching). The DU with the current serving cell of the UE may be referred to as a source DU, and the DU with the candidate cell may be referred to as a candidate / target DU. The serving BS may request the corresponding candidate / target DU to prepare configurations for one or more candidate cells.

[0049] In response to receiving configurations for one or more candidate cells from a candidate / target DU, the serving BS may transmit an RRC reconfiguration message (e.g., including the received configurations) to the UE, indicating the one or more candidate cells. For example, the CU of the serving BS may transmit the RRC reconfiguration message to the UE via the source DU. The UE may transmit an RRC reconfiguration complete message to the serving BS (e.g., the CU) via the source DU.

[0050] In some embodiments of the present disclosure, the UE may ensure UL / DL synchronization before receiving a cell exchange command (e.g., a switch from a serving cell to a candidate cell). For example, the UE may obtain (early) TA via random access or preamble transmission. This may be referred to as early TA acquisition. That is, the UE may perform a TA acquisition process before the cell exchange process. For dynamic exchange purposes, the UE may report L1 measurement results to the serving BS (e.g., the source DU). For example, the L1 measurement results may be associated with one or more candidate cells. The serving BS may determine to perform cell exchange based on the measurement results. For example, the serving BS (e.g., the source DU) may transmit a cell exchange command (e.g., an L1 / L2 triggered mobility cell exchange command) to the UE via, for example, a MAC CE or downlink control information (DCI). The UE may apply an RRC reconfiguration message and start a timer in response to receiving a lower layer command.

[0051] Embodiments of the present disclosure provide solutions for handling various problems associated with early TA acquisition. For example, it is necessary to solve how to transmit (early) TA values ​​from the source DU to the UE. For example, a solution is provided for determining whether the TA value should be carried in a random access response (RAR) or a cell exchange command. For example, the UE may monitor the RAR in the RAR window. A solution is provided for determining the RAR window. For example, a conflict may occur between the RAR and the cell exchange command. A solution is provided for resolving the conflict. For example, when the UE may be triggered to reacquire TA for a specific candidate cell or the UE may receive another TA value related to a specific candidate cell (for example, in a cell exchange command), the (early) TA value related to the same candidate cell may already be stored at the UE. A solution is provided for handling the above scenarios on the UE side. For example, a solution is provided for handling compliance checks on configurations associated with early TA acquisition. More details will be illustrated in the following text in conjunction with the accompanying drawings.

[0052] In the context of the present disclosure, inter-DU mobility means that while the UE maintains its connection with the same CU, the UE switches from a source cell of a source DU to a target cell of a target DU, where both the source DU and the target DU are managed by the same CU. Intra-DU mobility means that while the UE maintains its connection with the same CU, the UE switches from a source cell to a target cell, where both the source cell and the target cell belong to the same DU. For clarity, the embodiments of the present disclosure may be described with respect to the inter-DU mobility scenario (e.g., BS-inter-DU LTM). Those skilled in the art can readily understand that these embodiments can be similarly applied to the intra-DU mobility scenario (e.g., BS-intra-DU LTM), for example, with minor modifications that should be apparent to those skilled in the art.

[0053] Figure 3A flowchart illustrating an exemplary process 300 for early TA acquisition according to some embodiments of the present disclosure is provided. Figure 3 The embodiments shown in .

[0054] like Figure 3 As shown in FIG3 , in operation 311, UE 301 may access BS 302 (i.e., serving BS) and may transmit a measurement report to BS 302. BS 302 may include a CU (i.e., CU 303) and at least one DU (e.g., DU 304 and DU 305). BS 302 may include one or more DUs (not shown) other than DU 304 and DU 305. Figure 7 Each of DU 304 and DU 305 may include one or more cells, which may also be referred to as a cell of BS 302. UE 301 may be served by the cell of DU 304; this cell may be referred to as a serving cell of UE 301, and DU 304 may be referred to as a serving DU of UE 301 and may be referred to as a source DU of UE 301.

[0055] In operation 313, BS 302 (e.g., CU 303) may determine to initiate L1 / L2-based inter-cell mobility configuration (e.g., LTM configuration) and transmit a request message (e.g., a UE context establishment request message) to one or more candidate DUs (e.g., DU 305) associated with one or more candidate cells. In some embodiments, the request message may indicate early TA acquisition. That is, the TA value associated with the candidate cell may be acquired before the cell switching process associated with the candidate cell.

[0056] In some embodiments, the candidate DU may be instructed to acquire the TA value with or without RAR from the serving cell. For example, the request message may indicate whether to use RAR, cell switch command, or MAC CE to carry the TA value.

[0057] If DU 305 decides to accept the request for LTM configuration related to the candidate cell (i.e., the cell of DU 305), DU 305 may generate a lower layer RRC configuration for the accepted candidate cell. In operation 315, DU 305 may transmit a response message including the generated lower layer RRC configuration (also referred to as the "candidate cell configuration for LTM") to CU 303. In some embodiments, random access channel (RACH) resources for early TA acquisition may be included in the response message. In some embodiments, the response message may be a UE context establishment response message.

[0058] In some embodiments, the DU 305 may be configured with RAR-related information (or RAR-related configuration) for early TA acquisition. In some examples, the DU 305 may transmit the RAR-related information to the DU 304 via the CU 303. For example, the RAR-related information may be transmitted to the CU 303 in operation 315 (e.g., in a response message), and then the RAR-related information may be transmitted from the CU 303 to the DU 304 in operation 317. The DU 304 may transmit the RAR-related information to the UE 301. In some examples, the RAR-related information may be transmitted to the CU 303, and then the RAR-related information may be transmitted from the CU 303 to the UE 301 (e.g., via RRC).

[0059] In some embodiments, the RAR-related information may include the length of the RAR window (e.g., ra-responsewindow) used to monitor the RAR (which may carry the TA value), an offset associated with the RAR window, or both. For example, the RAR-related information may be included in the ra-ResponseWindow information element (IE). Details of the RAR window will be described later. In some other embodiments described later, the RAR-related information may be configured by the source DU (e.g., DU 304) or serving cell rather than the candidate DU (e.g., DU 305) or candidate cell.

[0060] In operations 317 and 319, CU 303 may transmit the received configuration to DU 304 (source DU) and UE 301. For example, in some embodiments, CU 303 may generate an RRC reconfiguration message based on the received configuration for the candidate cell. For example, the RRC reconfiguration message may include the candidate cell configuration for LTM, RACH resources for early TA acquisition, RAR-related information (if configured by the candidate DU (e.g., DU 305) or the candidate cell), or any combination thereof. In operations 317 and 319, CU 303 may transmit the generated configuration to DU 304 (source DU) and UE 301. For example, CU 303 may transmit the generated configuration to UE 301 via DU 304. In some embodiments, CU 303 may further indicate whether early TA acquisition should be triggered.

[0061] In some embodiments, RAR-related information may be configured by DU 304 (i.e., the source DU). For example, DU 304 may configure a time window (e.g., a ra-response window) for monitoring RAR (which may carry a TA value). For example, the RAR-related information may include the length of the RAR window, an offset associated with the RAR window, or both. For example, the RAR-related information may be included in a ra-ResponseWindow IE. In some examples, the RAR-related information may be transmitted from the serving DU or serving cell to UE 301 via a MAC CE. In some examples, the RAR-related information may be transmitted to CU 303, which may transmit the information to UE 301 via RRC.

[0062] In operation 319 , the UE 301 may receive an RRC configuration message associated with one or more candidate cells for LTM configuration.

[0063] In operation 321, UE 301 may receive an indication from its serving cell or serving DU (e.g., DU 304) to trigger TA acquisition for a specific candidate cell among one or more candidate cells. The indication may be a PDCCH command associated with the candidate cell. For simplicity, it is assumed that the candidate cell is the cell of DU 305 (candidate DU). In response to the PDCCH command, in operation 323, UE 301 may transmit a signal (e.g., a preamble for (early) TA acquisition) to DU 305 (i.e., to the corresponding candidate cell).

[0064] In response to receiving the signal (e.g., the preamble), in operation 325, the DU 305 (or the candidate cell) may transmit a TA value associated with the candidate cell to the CU 303. The CU 303 may store the TA value received from the DU 305 (or the candidate cell). For example, if the DU 305 (or the candidate cell) may calculate or generate a TA value associated with the candidate cell based on the received preamble, the DU 305 (or the candidate cell) may transmit the calculated TA value to the CU 303. The DU 305 may store the TA value.

[0065] In some embodiments, DU 305 (or candidate cell) may also transmit one or more of the following to CU 303: the received preamble, the corresponding RACH timing, the beam indication, the UE ID, the random access-cell radio network temporary identifier (RA-RNTI), the target cell ID of the target cell (i.e., the ID of the candidate cell) and the transmission configuration indication (TCI) status index, as well as other necessary information.

[0066] In operation 327, CU 303 may transmit the information received from DU 305 in operation 325 to DU 304 (source DU). For example, CU 303 may transmit the received information to DU 304 via the F1 interface. As described above, the received information may include a TA value associated with the candidate cell. DU 304 may store the received TA value. In some embodiments, DU 304 (source DU) may determine how to transmit the TA value to the UE. For example, DU 304 (source DU) may need to know whether the TA value should be transmitted in a RAR, a cell switch command, or any other MAC CE. DU 304 (source DU) may make this determination based on explicit or implicit instructions.

[0067] For example, in some embodiments, DU 305 (or a candidate cell) may transmit an indication (labeled as indication #1 for clarity) to DU 304 (the source DU) via CU 303, indicating whether the TA value will be transmitted to the UE via RAR, MAC CE, or a cell switch command (e.g., in operations 325 and 327). DU 304 may then transmit the TA value to UE 301 according to indication #1 (e.g., in operation 329). If DU 304 does not receive indication #1, DU 304 may transmit the TA value to UE 301 in a cell switch command (e.g., in operation 329). For example, the cell switch command may include a TA value field for the target cell, which may be used to carry the TA value.

[0068] For example, in some embodiments, CU 303 may transmit an indication (labeled as indication #2 for clarity) to DU 304 (source DU) indicating whether the TA value will be transmitted to the UE via RAR, MACCE, or a cell switch command (e.g., in operation 327). DU 304 may then transmit the TA value to UE 301 according to indication #2 (e.g., in operation 329). If DU 304 does not receive indication #2, DU 304 may transmit the TA value to UE 301 in a cell switch command (e.g., in operation 329). For example, the cell switch command may include a TA value field for the target cell, which may be used to carry the TA value.

[0069] For example, in some embodiments, the DU 304 may determine whether to transmit the TA value via the RAR, MAC CE, or cell switch command based on whether the DU 304 receives any RAR-related information. For example, if the DU 304 receives RAR-related information from the CU 303 or the DU 305 (or a candidate cell), the DU 304 may transmit the TA value to the UE 301 in the RAR (e.g., in operation 329). If the DU 304 does not receive any RAR-related information, the DU 304 may transmit the TA value to the UE 301 in the cell switch command (or any other dedicated MAC CE) (e.g., in operation 329).

[0070] The description of RAR-related information in the previous embodiments is also applicable here. In some examples, the RAR-related information may include one or more of the following: information related to the RAR window (e.g., length, offset, or both), or the RNTI (e.g., RA-RNTI or any other specific RNTI) to be used for receiving the RAR in the serving cell. In some embodiments, DU 304 (serving DU) may configure UE 301 to receive the RAR in the serving cell, for example, using the RAR-related information.

[0071] In operation 329, UE 301 may receive a TA value from DU 304 (or a serving cell) and may store the received TA value. For example, UE 301 may receive the TA value from DU 304 (or a serving cell) via RAR, MAC CE, or a cell exchange command. If the TA value is carried using RAR, UE 301 may receive the TA value using one of the cell-RNTI (C-RNTI), RA-RNTI, or specific RNTI associated with the serving cell of UE 301 (or DU 304 may transmit the TA value using the same).

[0072] In some embodiments, UE 301 may determine a RAR window for monitoring RAR based on RAR-related information. For example, as described above, the RAR-related information may include the length of the RAR window for monitoring RAR, an offset associated with the RAR window, or both. In some embodiments, the offset may be in symbols, slots, milliseconds, or any other time unit. In some embodiments, at least for inter-frequency scenarios, the offset may cover the radio frequency (RF) exchange time. In some embodiments, for intra-frequency scenarios, the offset may be zero.

[0073] In some embodiments, the start time of the RAR window may be based on an offset, and the duration of the RAR window may be based on the length of the RAR window. For example, the RAR window may start at the first symbol of the earliest control resource set (CORESET) of the PDCCH of the Type 1-PDCCH common search space (CSS) set that the UE 301 is configured to receive, which is at least one symbol after the last symbol of the PRACH opportunity corresponding to the PRACH transmission (e.g., the preamble transmission in operation 323) plus the offset. The duration of the RAR window may be equal to the length of the RAR window.

[0074] In some embodiments, the duration of the RAR window may be based on the offset and the length of the RAR window. For example, the RAR window may begin at the first symbol of the earliest CORESET of the PDCCH of the Type 1-PDCCH CSS set for which the UE 301 is configured to receive, which is at least one symbol after the last symbol of the PRACH opportunity corresponding to the PRACH transmission. The duration of the RAR window may be equal to the length of the RAR window plus the offset.

[0075] In some embodiments, the offset may be predefined (e.g., fixed or specified in the 3GPP standard). The RAR-related information may not indicate an offset. For example, the RAR window may begin at the first symbol of the earliest CORESET of the PDCCH of the Type 1-PDCCH CSS set that the UE 301 is configured to receive, the first symbol being at least a specific time period after the last symbol of the PRACH opportunity corresponding to the PRACH transmission. The specific time period may be predefined (e.g., fixed or specified in the 3GPP standard) as x milliseconds, y time slots, or z symbols. The duration of the RAR window may be equal to the length of the RAR window.

[0076] In some embodiments, the length of the RAR window may take the offset into account. The RAR window may begin at the first symbol of the earliest CORESET of the PDCCH of the Type 1-PDCCH CSS set that the UE 301 is configured to receive, which is at least one symbol after the last symbol of the PRACH opportunity corresponding to the PRACH transmission. The duration of the RAR window may be equal to the length of the RAR window.

[0077] In some embodiments, in operation 331, UE 301 may perform a cell switch in response to receiving a cell switch command. The network (e.g., source DU (e.g., DU 304), CU (e.g., CU 303), candidate DU (e.g., DU 305)) may maintain or store the TA value received from the candidate DU (e.g., DU 305), regardless of whether the TA was transmitted to the UE via the RAR option or the non-RAR option. After UE 301 switches to the target cell (e.g., cell #1), UE 301 may release the stored (earlier) TA value associated with the target cell (e.g., cell #1). After UE 301 switches to the target cell (e.g., cell #1), the network node (e.g., source DU (e.g., DU 304), CU (e.g., CU 303), candidate DU (e.g., DU 305)) with the TA value may transmit the stored (earlier) TA value to the new source cell (e.g., cell #1) to which UE 301 switches.

[0078] Those skilled in the art will appreciate that the order of the operations in exemplary process 300 may be changed and some of the operations in exemplary process 300 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0079] Figure 4 A flowchart illustrating an exemplary process 400 for early TA acquisition according to some embodiments of the present disclosure is provided. Figure 4 The embodiments shown in .

[0080] like Figure 4 As shown in FIG4 , in operation 411, UE 401 may access BS 402 (i.e., serving BS) and may transmit a measurement report to BS 402. BS 402 may include a CU (i.e., CU 403) and at least one DU (e.g., DU 404 and DU 405). BS 402 may include one or more DUs (not shown) other than DU 404 and DU 405. Figure 7 404 and DU 405 may each include one or more cells, which may also be referred to as a cell of BS 402. UE 401 may be served by the cell of DU 404; this cell may be referred to as a serving cell of UE 401, and DU 404 may be referred to as a serving DU of UE 401 and may be referred to as a source DU of UE 401.

[0081] In operation 413, BS 402 (e.g., CU 403) may determine to initiate L1 / L2-based inter-cell mobility configuration (e.g., LTM configuration) and transmit a request message (e.g., a UE context establishment request message) to one or more candidate DUs (e.g., DU 405) associated with one or more candidate cells. In some embodiments, the request message may indicate early TA acquisition. That is, the TA value associated with the candidate cell may be acquired before the cell switching process associated with the candidate cell.

[0082] If DU 405 decides to accept the request for LTM configuration related to the candidate cell (i.e., the cell of DU 405), DU 405 may generate a lower layer RRC configuration for the accepted candidate cell. In operation 415, DU 405 may transmit a response message including the generated lower layer RRC configuration (also referred to as the "candidate cell configuration for LTM") to CU 403. In some embodiments, RACH resources for early TA acquisition may be included in the response message. In some embodiments, the response message may be a UE context establishment response message.

[0083] In operations 417 and 419, CU 403 may transmit the received configuration to DU 404 (source DU) and UE 401. For example, in some embodiments, CU 403 may generate an RRC reconfiguration message based on the received configuration for the candidate cell. For example, the RRC reconfiguration message may include the candidate cell configuration for LTM, RACH resources for early TA acquisition, RAR-related information (if configured), or any combination thereof. In operations 417 and 419, CU 403 may transmit the generated configuration to DU 404 (source DU) and UE 401. For example, CU 403 may transmit the generated configuration to UE 401 via DU 404. In some embodiments, CU 403 may further indicate whether early TA acquisition should be triggered.

[0084] In operation 419 , the UE 401 may receive an RRC configuration message associated with one or more candidate cells for LTM configuration.

[0085] In operation 421, UE 401 may receive an indication from its serving cell or serving DU (e.g., DU 404) to trigger TA acquisition for a specific candidate cell among one or more candidate cells. The indication may be a PDCCH command associated with the candidate cell. For simplicity, it is assumed that the candidate cell is the cell of DU 405 (candidate DU). In response to the PDCCH command, in operation 423, UE 401 may transmit a signal (e.g., a preamble for (early) TA acquisition) to DU 405 (i.e., to the corresponding candidate cell).

[0086] In response to receiving the signal (e.g., the preamble), in operation 425, the DU 405 (or the candidate cell) may transmit a TA value associated with the candidate cell to the CU 403. For example, if the DU 405 (or the candidate cell) may calculate or generate a TA value associated with the candidate cell based on the received preamble, the DU 405 (or the candidate cell) may transmit the calculated TA value to the CU 403. In some embodiments, the DU 405 (or the candidate cell) may also transmit one or more of the following to the CU 403: the received preamble, the corresponding RACH opportunity, the beam indication, the UE ID, the RA-RNTI, the target cell ID and TCI state index of the target cell, and other necessary information.

[0087] In operation 427, CU 403 may transmit the information received from DU 405 in operation 425 to DU 404 (source DU). For example, CU 403 may transmit the received information to DU 404 via an F1 interface. As described above, the received information may include a TA value related to the candidate cell.

[0088] In some embodiments, while DU 404 (source DU) transmits a cell switching command related to a candidate cell to UE 401, DU 404 may be instructed to transmit a TA value related to the same candidate cell to UE 401 via RAR. For example, DU 404 (source DU) is instructed to transmit the TA value related to the candidate cell to UE 401 via RAR MAC CE, but DU 404 must immediately transmit a cell switching command related to the same candidate cell to UE 401.

[0089] In some embodiments, the DU 404 may transmit a cell switch command including a TA value and skip transmission of an RAR to the UE 401 in operation 429. In some embodiments, the DU 404 may transmit a cell switch command without a TA value and skip transmission of an RAR to the UE 401 in operation 429. In some embodiments, the DU 404 may multiplex the cell switch command and the RAR into the same MAC layer data unit (e.g., the same MAC protocol data unit (PDU)) in operation 429 and transmit the MAC layer data unit to the UE 401.

[0090] In some embodiments, UE 401 may perform a cell switch to a candidate cell in response to receiving a cell switch command associated with the candidate cell.

[0091] Those skilled in the art will appreciate that the order of the operations in exemplary process 400 may be changed and some of the operations in exemplary process 400 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0092] Figure 5 A flowchart illustrating an exemplary process 500 for early TA acquisition according to some embodiments of the present disclosure is provided. Figure 5 The embodiments shown in .

[0093] like Figure 5 As shown in FIG5 , in operation 511, UE 501 may access BS 502 (i.e., serving BS) and may transmit a measurement report to BS 502. BS 502 may include a CU (i.e., CU 503) and at least one DU (e.g., DU 504 and DU 505). BS 502 may include one or more DUs (not shown) other than DU 504 and DU 505. Figure 7 Each of DU 504 and DU 505 may include one or more cells, which may also be referred to as a cell of BS 502. UE 501 may be served by the cell of DU 504; this cell may be referred to as a serving cell of UE 501, and DU 504 may be referred to as a serving DU of UE 501 and may be referred to as a source DU of UE 501.

[0094] In operation 513, BS 502 (e.g., CU 503) may determine to initiate L1 / L2-based inter-cell mobility configuration (e.g., LTM configuration) and transmit a request message (e.g., a UE context establishment request message) to one or more candidate DUs (e.g., DU 505) associated with one or more candidate cells. In some embodiments, the request message may indicate early TA acquisition. That is, the TA value associated with the candidate cell may be acquired before the cell switching process associated with the candidate cell.

[0095] If DU 505 decides to accept the request for LTM configuration related to the candidate cell (i.e., the cell of DU 505), DU 505 may generate a lower layer RRC configuration for the accepted candidate cell. In operation 515, DU 505 may transmit a response message including the generated lower layer RRC configuration (also referred to as the "candidate cell configuration for LTM") to CU 503. In some embodiments, RACH resources for early TA acquisition may be included in the response message. In some embodiments, the response message may be a UE context establishment response message.

[0096] In operations 517 and 519, CU 503 may transmit the received configuration to DU 504 (source DU) and UE 501. For example, in some embodiments, CU 503 may generate an RRC reconfiguration message based on the received configuration for the candidate cell. For example, the RRC reconfiguration message may include the candidate cell configuration for LTM, RACH resources for early TA acquisition, RAR-related information (if configured), or any combination thereof. In operations 517 and 519, CU 503 may transmit the generated configuration to DU 504 (source DU) and UE 501. For example, CU 503 may transmit the generated configuration to UE 501 via DU 504. In some embodiments, CU 503 may further indicate whether early TA acquisition should be triggered.

[0097] In operation 519 , the UE 501 may receive an RRC configuration message associated with one or more candidate cells for LTM configuration.

[0098] In operation 521, UE 501 may receive an indication from its serving cell or serving DU (e.g., DU 504) to trigger TA acquisition for a specific candidate cell among one or more candidate cells. The indication may be a PDCCH command associated with the candidate cell. For simplicity, it is assumed that the candidate cell is the cell of DU 505 (candidate DU). In response to the PDCCH command, in operation 523, UE 501 may transmit a signal (e.g., a preamble for (early) TA acquisition) to DU 505 (i.e., to the corresponding candidate cell).

[0099] In response to receiving the signal (e.g., the preamble), in operation 525, the DU 505 (or the candidate cell) may transmit a TA value associated with the candidate cell to the CU 503. For example, if the DU 505 (or the candidate cell) may calculate or generate a TA value associated with the candidate cell based on the received preamble, the DU 505 (or the candidate cell) may transmit the calculated TA value to the CU 503. In some embodiments, the DU 505 (or the candidate cell) may also transmit one or more of the following to the CU 503: the received preamble, the corresponding RACH opportunity, the beam indication, the UE ID, the RA-RNTI, the target cell ID and TCI state index of the target cell, and other necessary information.

[0100] In some other embodiments, if DU 505 (candidate DU) is unable to calculate a TA value based on the received preamble, RACH resources may be transmitted to DU 504 (source DU) via CU 503. In some embodiments, if DU 505 (candidate DU) is unable to receive a preamble at a configured RACH opportunity (RO), DU 505 (candidate DU) may indicate this failure to DU 504 (source DU) via CU 503. DU 504 (source DU) may then trigger TA reacquisition. Alternatively, DU 505 (candidate DU) may use an explicit indication to indicate TA reacquisition. DU 504 (or the serving cell) may then transmit a PDCCH command to UE 501.

[0101] In operation 527, CU 503 may transmit the information received from DU 505 in operation 525 to DU 504 (source DU). For example, CU 503 may transmit the received information to DU 504 via an F1 interface. As described above, the received information may include a TA value related to the candidate cell.

[0102] In operation 529, DU 504 (source DU) may transmit a TA value to UE 501 via, for example, a RAR MAC CE. In some embodiments, UE 501 may successfully receive the TA value from the serving cell. For example, if UE 501 receives the TA value within the RAR window, UE 501 may determine that the TA value has been successfully received. In response to the determination or successful receipt of the TA value, UE 501 may transmit an indication of successful receipt of the TA value to BS 502. In some embodiments, the indication may be transmitted via an L1 indication, a MAC CE, or an RRC message.

[0103] In some embodiments, UE 501 may receive an (earlier) TA value associated with a candidate cell (designated as cell #2) via the RAR. In some instances, UE 501 then does not expect to receive another (earlier) TA value associated with cell #2 in a cell switch command associated with the same candidate cell (i.e., cell #2). In some instances, UE 501 may receive another (earlier) TA value associated with cell #2 in a cell switch command associated with the same candidate cell (i.e., cell #2). UE 501 may then use the latest TA value for cell #2. For example, UE 501 may replace the TA value associated with cell #2 stored at UE 501 with the other TA value. In other words, when the TA field is configured to be present in a cell switch command, UE 501 may use the TA value indicated by the TA field in the cell switch command even if it has already received an (earlier) TA associated with the same cell via the RAR.

[0104] In some embodiments, when a candidate cell (designated as cell #3) determines that the TA value associated with cell #3 stored in UE 501 is invalid, cell #3 (or a DU of cell #3) may instruct DU 504 (the source DU) to trigger TA acquisition. DU 504 (the source DU) may transmit a PDCCH command to UE 501 for TA reacquisition. From the perspective of UE 501, UE 501 may receive a PDCCH command associated with cell #3, wherein the PDCCH command triggers TA reacquisition. In response to receiving the PDCCH command, UE 501 may delete the stored TA value associated with cell #3.

[0105] In some other embodiments, UE 501 may fail to receive a TA value from the serving cell. For example, if UE 501 does not receive a TA value within the RAR window, UE 501 may determine that the TA value was not successfully received. In response to the determination or the failure to successfully receive the TA value, UE 501 may transmit an indication of the failure to successfully receive the TA value (or a failure to receive the TA value) to BS 502. In some embodiments, the indication may be transmitted via an L1 indication, a MAC CE, or an RRC message.

[0106] Those skilled in the art will appreciate that the order of the operations in exemplary process 500 may be changed and some of the operations in exemplary process 500 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0107] Figure 6 A flowchart illustrating an exemplary process 600 for early TA acquisition according to some embodiments of the present disclosure is provided. Figure 6 The embodiments shown in .

[0108] like Figure 6 As shown in FIG6 , in operation 611, UE 601 may access BS 602 (i.e., serving BS) and may transmit a measurement report to BS 602. BS 602 may include a CU (i.e., CU 603) and at least one DU (e.g., DU 604 and DU 605). BS 602 may include one or more DUs (not shown) other than DU 604 and DU 605. Figure 7 Each of DU 604 and DU 605 may include one or more cells, which may also be referred to as the cell of BS 602. UE 601 may be served by the cell of DU 604; this cell may be referred to as the serving cell of UE 601, and DU 604 may be referred to as the serving DU of UE 601 and may be referred to as the source DU of UE 601.

[0109] In operation 613, BS 602 (e.g., CU 603) may determine to initiate L1 / L2-based inter-cell mobility configuration (e.g., LTM configuration) and transmit a request message (e.g., a UE context establishment request message) to one or more candidate DUs (e.g., DU 605) associated with one or more candidate cells. In some embodiments, the request message may indicate early TA acquisition. That is, the TA value associated with the candidate cell may be acquired before the cell switching process associated with the candidate cell.

[0110] If DU 605 decides to accept the request for LTM configuration related to the candidate cell (i.e., the cell of DU 605), DU 605 may generate a lower layer RRC configuration for the accepted candidate cell. In operation 615, DU 605 may transmit a response message including the generated lower layer RRC configuration (also referred to as the "candidate cell configuration for LTM") to CU 603. In some embodiments, RACH resources for early TA acquisition may be included in the response message. In some embodiments, the response message may be a UE context establishment response message.

[0111] In operations 617 and 619, CU 603 may transmit the received configuration to DU 604 (source DU) and UE 601. For example, in some embodiments, CU 603 may generate an RRC reconfiguration message based on the received configuration for the candidate cell. For example, the RRC reconfiguration message may include the candidate cell configuration for LTM, RACH resources for early TA acquisition, RAR-related information (if configured), or any combination thereof. In operations 617 and 619, CU 603 may transmit the generated configuration to DU 604 (source DU) and UE 601. For example, CU 603 may transmit the generated configuration to UE 601 via DU 604. In some embodiments, CU 603 may further indicate whether early TA acquisition should be triggered.

[0112] In operation 619 , the UE 601 may receive an RRC configuration message associated with one or more candidate cells for LTM configuration.

[0113] In operation 621, the UE 601 may perform a compliance check on the RRC configuration message. For example, the compliance check may be performed on one or more of the following: a reference configuration, a RACH configuration for early TA acquisition, a candidate cell configuration, and a full LTM configuration. For example, the compliance check on the RACH configuration may be performed in response to receiving a RACH configuration for early TA acquisition associated with a candidate cell or in response to receiving a PDCCH order associated with the candidate cell.

[0114] In some embodiments, in response to a compliance check failure, UE 601 may report failure information associated with the compliance check to BS 602. For example, UE 601 may report a reason for the compliance check failure. For example, UE 601 may report to BS 602 an indication indicating one of the following: compliance check failure, reconfiguration failure, reference configuration failure, RACH configuration failure for early TA acquisition, or LTM configuration failure.

[0115] In some embodiments, in response to a failure in the compliance check of the master cell group (MCG) configuration, the UE 601 may perform a reestablishment procedure. The UE 601 may continue to use the configuration used before the time when the failure to comply with the RRC reconfiguration message was detected. That is, the UE 601 may use the current configuration instead of the configuration received in operation 619.

[0116] In some embodiments, in response to a failure in the compliance check on the MCG configuration, if the MCG is not suspended, a secondary cell group (SCG) failure information procedure is initiated. Otherwise, the UE may perform a reestablishment procedure. The UE 601 may continue to use the configuration used before the time when the failure to comply with the RRC reconfiguration message was detected. That is, the UE 601 may use the current configuration instead of the configuration received in operation 619.

[0117] Those skilled in the art will appreciate that the order of the operations in exemplary process 600 may be changed and some of the operations in exemplary process 600 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0118] Figures 3 to 6 The exemplary processes 300 to 600 in FIG. 3 are described with respect to the inter-DU mobility scenario. A person skilled in the art can easily understand that the exemplary processes 300 to 600 can be similarly applied to the intra-DU mobility scenario. For example, in Figure 3 In the exemplary process 300 in FIG. 3 , DU 304 and DU 305 may be the same DU of BS 302. Therefore, the interaction between DU 304 and DU 305 may be omitted. For example, Figure 3 Operations 315 and 317 and operations 325 and 327 in can be omitted.

[0119] Figure 7 700 for wireless communication according to some embodiments of the present disclosure. Figure 7 The exemplary process 700 may be performed by a BS (eg, a DU of the BS).

[0120] refer to Figure 7In operation 711, the first DU of the BS may receive configuration information about early TA acquisition of candidate cells for cell switching from the CU of the BS. For example, the first DU may be used as Figure 3 DU 304, Figure 4 DU 404, Figure 5 DU 504 or Figure 6 For example, regarding Figure 3 Operation 317, Figure 4 Operation 417, Figure 5 Operation 517 and Figure 6 The description of operation 617 in can be applied to operation 711.

[0121] In operation 713, the first DU may transmit a PDCCH command associated with the candidate cell to the UE served by the first DU, wherein the PDCCH command triggers the UE to transmit a signal (e.g., a preamble) to the candidate cell. For example, the signal (e.g., a preamble) may be transmitted via a configured RO. For example, the UE may be used as Figure 3 UE 301 in Figure 4 UE401 in Figure 5 UE 501 or Figure 6 For example, regarding the UE 601 in Figure 3 Operation 321, Figure 4 Operation 421 and Figure 5 The description of operation 521 in can be applied to operation 713.

[0122] In some embodiments, in response to transmitting a PDCCH command, the first DU may receive a TA value related to the candidate cell (e.g., an early TA value) from the candidate cell; and perform one of the following: receive a first indication (e.g., indication #1) from the candidate cell indicating whether the TA value will be transmitted to the UE via RAR, MAC CE, or cell exchange command, and transmit the TA value to the UE according to the first indication; transmit the TA value to the UE via the cell exchange command if the first DU does not receive the first indication; receive a second indication (e.g., indication #2) from the CU indicating whether the TA value will be transmitted to the UE via RAR, MAC CE, or cell exchange command, and transmit the TA value to the UE according to the second indication; transmit the TA value to the UE via the cell exchange command if the first DU does not receive the second indication; transmit the TA value to the UE via the cell exchange command if the first DU does not receive the second indication; transmit the TA value to the UE via the RAR if the first DU receives RAR-related information from the CU or the candidate cell; or transmit the TA value to the UE via the cell exchange command if the first DU does not receive any RAR-related information.

[0123] In some embodiments, the first DU may receive RAR-related information from the candidate DU via the CU, or configure RAR-related information for the UE; and transmit RAR-related information from the UE's serving cell to the UE to monitor the RAR carrying the TA value.

[0124] In some embodiments, the RAR-related information may include the length of the RAR window used to monitor the RAR, an offset associated with the RAR window, or both.

[0125] In some embodiments, the first DU may receive a TA value related to the candidate cell from the candidate cell in response to transmitting a PDCCH command; and use one of the C-RNTI, RA-RNTI or specific RNTI associated with the UE's serving cell to transmit the TA value to the UE via the RAR.

[0126] In some embodiments, when the first DU is instructed to transmit a TA value related to the candidate cell to the UE via the RAR while transmitting a cell exchange command related to the candidate cell to the UE, the first DU may: transmit the cell exchange command including the TA value and skip the transmission of the RAR; transmit the cell exchange command without the TA value and skip the transmission of the RAR; or multiplex the cell exchange command and the RAR into the same MAC layer data unit (e.g., MAC PDU).

[0127] Those skilled in the art will appreciate that the order of the operations in exemplary process 700 may be changed and some of the operations in exemplary process 700 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0128] Figure 8 800 for wireless communication according to some embodiments of the present disclosure. Figure 8 The exemplary process 800 may be performed by a UE.

[0129] refer to Figure 8 In operation 811, the UE may receive a PDCCH command associated with a candidate cell for cell switching. For example, the UE may be used as Figure 3 UE 301 in Figure 4 UE 401 in Figure 5 UE 501 or Figure 6 For example, regarding the UE 601 in Figure 3 Operation 321, Figure 4 Operation 421 and Figure 5 The description of operation 521 in can be applied to operation 811.

[0130] In operation 813, the UE may transmit a signal (eg, a preamble) to the candidate cell in response to receiving the PDCCH command. Figure 3 Operation 323, Figure 4 Operation 423 and Figure 5 The description of operation 523 in can be applied to operation 813.

[0131] In operation 815, the UE may receive a TA value associated with a candidate cell via a first DU of the BS, wherein the UE is served by the first DU. For example, the first DU may be used as Figure 3 DU 304, Figure 4 DU 404, Figure 5 DU 504 or Figure 6 For example, regarding Figure 3 Operation 329, Figure 4 Operation 429 and Figure 5 The description of operation 529 in can be applied to operation 815.

[0132] In some embodiments, the UE may receive RAR-related information from a CU or a first DU of a BS, wherein the RAR-related information is configured by the candidate cell or the first DU.

[0133] In some embodiments, the RAR-related information may include the length of the RAR window used to monitor the RAR carrying the TA value, an offset associated with the RAR window, or both. In some embodiments, the start time of the RAR window is based on the offset, and the duration of the RAR window is based on the length of the RAR window. In some embodiments, the duration of the RAR window is based on the offset and the length of the RAR window.

[0134] In some embodiments, in response to successfully receiving the TA value, the UE may transmit an indication of successful receipt of the TA value to the BS. In some embodiments, in response to unsuccessful receipt of the TA value, the UE may transmit an indication of unsuccessful receipt of the TA value to the BS. In some embodiments, the indication may be transmitted via an L1 indication, a MAC CE, or an RRC message.

[0135] In some embodiments, the TA value may be received via the RAR. In some embodiments, the UE does not expect to receive another TA value associated with the candidate cell in a cell switch command associated with the candidate cell. In some embodiments, the UE may receive another TA value in the cell switch command and replace the TA value stored at the UE with the other TA value.

[0136] In some embodiments, the UE may receive another PDCCH order associated with the candidate cell, wherein the another PDCCH order triggers TA reacquisition; and delete the stored TA value related to the candidate cell in response to receiving the another PDCCH order.

[0137] In some embodiments, a UE may receive a RACH configuration for early TA acquisition associated with a candidate cell from a base station (BS) and perform a compliance check on the RACH configuration. In some embodiments, the compliance check may be performed in response to receiving the RACH configuration or in response to receiving a PDCCH command. In some embodiments, in response to a compliance check failure, the UE may report failure information to the base station indicating one of the following: compliance check failure, reconfiguration failure, reference configuration failure, RACH configuration failure for early TA acquisition, or full LTM configuration failure.

[0138] In some embodiments, the TA value may be received via the RAR using a C-RNTI, RA-RNTI, or a specific RNTI associated with the UE's serving cell.

[0139] Those skilled in the art will appreciate that the order of the operations in exemplary process 800 may be changed and some of the operations in exemplary process 800 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0140] Figure 9 900 for wireless communication according to some embodiments of the present disclosure. Figure 9 The exemplary process 900 may be performed by a BS (eg, a DU of the BS).

[0141] refer to Figure 9 In operation 911, the second DU of the BS may receive a request for cell exchange associated with the candidate cell from the CU of the BS. For example, the second DU may be used as Figure 3 DU 305, Figure 4 DU 405, Figure 5 DU 505 or Figure 6 DU 605 in; and CU can be used as Figure 3 CU 303, Figure 4 CU 403, Figure 5 CU 503 or Figure 6 For example, regarding CU603 Figure 3 Operation 313, Figure 4 Operation 413, Figure 5 Operation 513 and Figure 6The description of operation 613 in can be applied to operation 911.

[0142] In operation 913, the second DU may transmit a response to the CU, wherein the response includes configuration information associated with the candidate cell. Figure 3 Operation 315, Figure 4 Operation 415, Figure 5 Operation 515 and Figure 6 The description of operation 615 in can be applied to operation 913.

[0143] In operation 915, the second DU may receive a signal (eg, a preamble) for early TA acquisition related to a candidate cell from a UE served by the first DU of the BS. For example, the first DU may be used as Figure 3 DU 304, Figure 4 DU 404, Figure 5 DU 504 or Figure 6 For example, regarding Figure 3 Operation 323, Figure 4 Operation 423 and Figure 5 The description of operation 523 in can be applied to operation 915.

[0144] In operation 917, the second DU may transmit the TA value related to the candidate cell to the first DU via the CU in response to receiving the signal. Figure 3 Operations 325 and 327 in Figure 4 Operations 425 and 427 and Figure 5 The description of operations 525 and 527 in can be applied to operation 917.

[0145] In some embodiments, the request may indicate whether to use RAR, MAC CE, or cell switch command to carry the TA value.

[0146] In some embodiments, the second DU may transmit a first indication (eg, indication #1) indicating whether the TA value will be transmitted to the UE via RAR, MAC CE, or cell switch command in response to receiving the signal.

[0147] In some embodiments, the response may further include the length of the RAR window used to monitor the RAR carrying the TA value, an offset associated with the RAR window, or both. In some embodiments, the start time of the RAR window is based on the offset, and the duration of the RAR window is based on the length of the RAR window. In some embodiments, the duration of the RAR window is based on the offset and the length of the RAR window.

[0148] Those skilled in the art will appreciate that the order of the operations in exemplary process 900 may be changed and some of the operations in exemplary process 900 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0149] Figure 10 A block diagram illustrating an exemplary device 1000 according to some embodiments of the present disclosure is shown. Figure 10 , the apparatus 1000 may include at least one processor 1006 and at least one transceiver 1002 coupled to the processor 1006. The apparatus 1000 may be a UE, a BS, a CU of a BS, or a DU of a BS.

[0150] Although elements such as at least one transceiver 1002 and processor 1006 are described in the singular in this figure, the plural is contemplated unless otherwise explicitly stated. In some embodiments of the present disclosure, transceiver 1002 may be divided into two devices, such as receive circuitry and transmit circuitry. In some embodiments of the present disclosure, apparatus 1000 may further include an input device, memory, and / or other components.

[0151] In some embodiments of the present disclosure, the device 1000 may be a UE. The transceiver 1002 and the processor 1006 may interact with each other to perform Figures 1 to 9 In some embodiments of the present disclosure, the device 1000 may be a BS. The transceiver 1002 and the processor 1006 may interact with each other to perform Figures 1 to 9 In some embodiments of the present disclosure, the device 1000 may be a DU of a BS. The transceiver 1002 and the processor 1006 may interact with each other to perform Figures 1 to 9 In some embodiments of the present disclosure, the device 1000 may be a CU of a BS. The transceiver 1002 and the processor 1006 may interact with each other to perform Figures 1 to 9 The operations on CU described in .

[0152] In some embodiments of the present disclosure, the apparatus 1000 may further include at least one non-transitory computer-readable medium.

[0153] For example, in some embodiments of the present disclosure, a non-transitory computer-readable medium may store thereon computer-executable instructions to cause the processor 1006 to implement the method described above with respect to the UE. For example, when the computer-executable instructions are executed, the processor 1006 interacts with the transceiver 1002 to perform Figures 1 to 9 The operations of the UE are described in .

[0154] In some embodiments of the present disclosure, a non-transitory computer-readable medium may store thereon computer-executable instructions to cause the processor 1006 to implement the method described above with respect to the BS. For example, when the computer-executable instructions are executed, the processor 1006 interacts with the transceiver 1002 to perform Figures 1 to 9 The operations of BS are described in .

[0155] In some embodiments of the present disclosure, a non-transitory computer-readable medium may store thereon computer-executable instructions to cause the processor 1006 to implement the method described above regarding the DU of the BS. For example, when the computer-executable instructions are executed, the processor 1006 interacts with the transceiver 1002 to perform Figures 1 to 9 The operations of DU of BS are described in .

[0156] In some embodiments of the present disclosure, a non-transitory computer-readable medium may store thereon computer-executable instructions to cause the processor 1006 to implement the method described above regarding the CU of the BS. For example, when the computer-executable instructions are executed, the processor 1006 interacts with the transceiver 1002 to perform Figures 1 to 9 The operations of the CU of the BS are described in .

[0157] 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 implemented directly in hardware, in a software module executed by a processor, or in 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 that can be incorporated into a computer program product.

[0158] Although the present disclosure has been described with respect to specific embodiments thereof, it is apparent that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, the various components of an embodiment may be interchangeable, added, or replaced in other embodiments. Furthermore, all elements in each figure are not essential for the operation of the disclosed embodiments. For example, one of ordinary skill in the art of the disclosed embodiments will be able to make and use the teachings of the present disclosure by simply adopting elements of an independent technical solution. Therefore, the embodiments of the present disclosure set forth herein are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0159] In this document, the terms "includes," "including," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process step, method, article, or device comprising a series of elements does not include only those elements, but may include other elements that are not explicitly listed or that are inherent to such process step, method, article, or device. The words "a," "an," and the like preceding an element do not exclude the presence of additional identical elements in the process step, method, article, or device comprising the element without further constraints. Furthermore, the term "another" is defined as at least a second or more. The terms "having," etc. used herein, are defined as "including." For example, expressions such as "A and / or B" or "at least one of A and B," etc. may include any and all combinations of the words listed together with the expression. For example, the expression "A and / or B" or "at least one of A and B," etc. may include A, B, or both A and B. The terms "first," "second," and the like are used only to clearly illustrate embodiments of the present disclosure, but are not intended to limit the essence of the present disclosure.

Claims

1. A first distributed unit DU of a base station BS, comprising: transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receiving, from a centralized unit CU of the BS, configuration information regarding early timing advance (TA) acquisition of candidate cells for cell switching; and A physical downlink control channel (PDCCH) command associated with the candidate cell is transmitted to a user equipment (UE) served by the first DU, wherein the PDCCH command triggers the UE to transmit a signal to the candidate cell.

2. The first DU of claim 1 , wherein the processor is further configured to, in response to transmitting the PDCCH command: receiving, from the candidate cell, a TA value associated with the candidate cell; and Do one of the following: receiving a first indication from the candidate cell indicating whether the TA value will be transmitted to the UE via a random access response RAR, a media access control MAC control element CE, or a cell switch command, and transmitting the TA value to the UE according to the first indication; In a case where the first DU does not receive the first indication, transmitting the TA value to the UE via the cell switch command; receiving a second indication from the CU indicating whether the TA value is to be transmitted to the UE via the RAR, the MAC CE, or the cell switch command, and transmitting the TA value to the UE according to the second indication; In a case where the first DU does not receive the second indication, transmitting the TA value to the UE via the cell switch command; In a case where the first DU receives RAR-related information from the CU or the candidate cell, transmitting the TA value to the UE via the RAR; or In a case where the first DU does not receive any RAR-related information, the TA value is transmitted to the UE via the cell switch command.

3. The first DU of claim 1 , wherein the processor is further configured to: receiving random access response (RAR) related information from a candidate DU via the CU, or configuring the RAR related information for the UE; and The RAR-related information is transmitted from a serving cell of the UE to the UE to monitor the RAR carrying a TA value. 4 . The first DU according to claim 2 , wherein the RAR-related information comprises a length of an RAR window for monitoring the RAR, an offset associated with the RAR window, or both.

5. The first DU of claim 1 , wherein the processor is further configured to: receiving, from the candidate cell, a TA value associated with the candidate cell in response to transmitting the PDCCH command; and The TA value is transmitted to the UE via a random access response (RAR) using one of a cell radio network temporary identifier (C-RNTI), a random access RNTI (RA-RNTI), or a specific RNTI associated with a serving cell of the UE.

6. The first DU according to claim 1 , wherein, in a case where the first DU is instructed to transmit a TA value related to the candidate cell to the UE via a random access response (RAR) while the first DU transmits a cell switch command related to the candidate cell to the UE, the processor is further configured to: transmitting the cell switch command including the TA value and skipping the transmission of the RAR; transmitting the cell switch command without the TA value and skipping the transmission of the RAR; or The cell switch command and the RAR are multiplexed into the same media access control MAC layer data unit.

7. A user equipment (UE), comprising: transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receiving a physical downlink control channel (PDCCH) order associated with a candidate cell for cell switching; transmitting a signal to the candidate cell in response to receiving the PDCCH command; and A timing advance TA value associated with the candidate cell is received via a first distributed unit DU of a base station BS, wherein the UE is served by the first DU.

8. The UE according to claim 7, wherein the processor is further configured to receive random access response (RAR) related information from a centralized unit (CU) of the BS or the first DU, and wherein the RAR related information is configured by the candidate cell or the first DU. 9 . The UE of claim 8 , wherein the RAR-related information comprises a length of an RAR window for monitoring the RAR carrying the TA value, an offset associated with the RAR window, or both.

10. The UE of claim 9, wherein a start time of the RAR window is based on the offset, and a duration of the RAR window is based on the length of the RAR window; or Wherein the duration of the RAR window is based on the offset and the length of the RAR window.

11. The UE of claim 7, wherein the processor is further configured to: In response to successfully receiving the TA value, transmitting an indication of successful receipt of the TA value to the BS; or In response to unsuccessful receipt of the TA value, an indication of unsuccessful receipt of the TA value is transmitted to the BS. 12 . The UE according to claim 11 , wherein the indication is transmitted via a Layer 1 (L1) indication, a Medium Access Control (MAC) Control Element (CE), or a Radio Resource Control (RRC) message.

13. The UE according to claim 7, wherein the TA value is received via a random access response (RAR); and wherein the UE does not expect to receive another TA value associated with the candidate cell in a cell switch command associated with the candidate cell, or Wherein the processor is further configured to receive the another TA value in the cell switch command and replace the TA value stored at the UE with the another TA value.

14. The UE of claim 7, wherein the processor is further configured to: receiving another PDCCH command associated with the candidate cell, wherein the another PDCCH command triggers TA reacquisition; and The stored TA value associated with the candidate cell is deleted in response to receiving the another PDCCH order.

15. The UE of claim 7, wherein the processor is further configured to: receiving, from the BS, a random access channel (RACH) configuration for early TA acquisition associated with the candidate cell; and A compliance check is performed on the RACH configuration. 16 . The UE of claim 15 , wherein the compliance check is performed in response to the receiving of the RACH configuration or in response to the receiving of the PDCCH order.

17. The UE according to claim 15, wherein the processor is further configured to report failure information indicating one of the following to the BS in response to the failure of the compliance check: compliance check failure, reconfiguration failure, reference configuration failure, RACH configuration failure for early TA acquisition, and complete lower layer triggered mobility LTM configuration failure.

18. The UE of claim 7, wherein the TA value is received via a random access response (RAR) using a cell radio network temporary identifier (C-RNTI), a random access RNTI (RA-RNTI), or a specific RNTI associated with a serving cell of the UE.

19. A second distributed unit DU of a base station BS, comprising: transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receiving, from a centralized unit CU of the BS, a request for cell exchange associated with a candidate cell; transmitting a response to the CU, wherein the response includes configuration information associated with the candidate cell; receiving, from a user equipment UE served by a first DU of the BS, a signal for early timing advance (TA) acquisition associated with the candidate cell; and In response to the receiving the signal, a TA value associated with the candidate cell is transmitted to the first DU via the CU.

20. The second DU according to claim 19, wherein the request indicates whether a random access response (RAR), a medium access control (MAC) control element (CE), or a cell switch command is used to carry the TA value.

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