Method and apparatus for lower layer based mobility conditions

Abstract

Embodiments of the present application relate to a method and apparatus for uplink (UL) synchronization failure and compliance check in lower layer based mobility scenarios under third generation partnership project (3GPP) 5G systems or the like. In accordance with an embodiment of the present application, a user equipment (UE) comprises: a transceiver; and a processor coupled to the transceiver and configured to: receive, via the transceiver, a radio resource control (RRC) reconfiguration message, where the RRC reconfiguration message includes first configuration information about one or more candidate cells; after receiving the RRC reconfiguration message, obtaining one or more timing advance (TA) values associated with the one or more candidate cells by performing one or more random access (RA) procedures or by transmitting one or more reference signals to the one or more candidate cells; and upon receiving a first indication from a source cell associated with a first candidate cell of the one or more candidate cells, handover from the source cell to the first candidate cell.

Description

Technical Field

[0001] Embodiments of the present application relate generally to wireless communication techniques, and more particularly to methods and apparatus for underlying layer-based mobility scenarios. Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcast, etc. Wireless communication systems may employ multiple access technologies capable of supporting communication with multiple users by sharing available system resources such as 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 of uplink (UL) synchronization failure and compliance check in the case of lower layer based mobility 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, which is coupled to the transceiver; and the processor is configured to: receive a radio resource control (RRC) reconfiguration message via the transceiver, wherein the RRC reconfiguration message includes first configuration information about one or more candidate cells; after receiving the RRC reconfiguration message, obtain one or more timing advance (TA) values ​​related to the one or more candidate cells by performing one or more random access (RA) procedures or by transmitting one or more reference signals to the one or more candidate cells; and after receiving a first indication associated with a first candidate cell within the one or more candidate cells from the source cell, switch from the source cell to the first candidate cell.

[0005] In some embodiments, the RRC reconfiguration message includes at least one of: a value of a first timer for obtaining a RA for the TA; or a maximum total number of preamble transmissions.

[0006] In some embodiments, after receiving the RRC reconfiguration message including the value of the first timer, the processor of the UE is configured to: start the first timer in response to initiating a first RA procedure for obtaining a TA within the one or more RA procedures, wherein the first timer is associated with the first RA procedure.

[0007] In some embodiments, the processor of the UE is configured to: stop the first timer in response to successfully obtaining a TA value associated with a candidate cell within the one or more candidate cells by performing the first RA procedure on the candidate cell; or consider the first RA procedure to have failed in response to expiration of the first timer.

[0008] In some embodiments, after receiving the RRC reconfiguration message including the maximum total number of preamble transmissions, the processor of the UE is configured to: in response to reaching the maximum total number of preamble transmissions during a second RA procedure for obtaining a TA within the one or more RA procedures, consider the second RA procedure to have failed, wherein the maximum total number of preamble transmissions is associated with the second RA procedure.

[0009] In some embodiments, in response to a failure to obtain the one or more TA values ​​by executing the one or more RA procedures, the processor of the UE is configured to perform one of the following: transmitting a first message to the source cell via the transceiver; suspending the first configuration information regarding the one or more candidate cells; and restarting the one or more RA procedures for the one or more candidate cells after a first time period.

[0010] In some embodiments, the first message includes at least one of: a second indication indicating that the UE failed to obtain the one or more TA values ​​associated with the one or more candidate cells; or a third indication indicating that the one or more RA procedures are for obtaining the one or more TA values.

[0011] In some embodiments, the first indication is included in downlink control information (DCI) or a medium access control (MAC) control element (CE).

[0012] In some embodiments, in response to the first candidate cell being a primary-secondary cell group cell (PSCell), the first indication is received by the UE from at least one of a secondary node (SN) or a master node (MN).

[0013] In some embodiments, the processor of the UE is configured to start a switching timer after the RRC layer of the UE receives the first indication from a lower layer of the UE.

[0014] In some embodiments, the processor of the UE is configured to: after receiving the first indication, determine whether a first TA value associated with the first candidate cell is available; in response to determining that the first TA value is unavailable, perform one of the following: after determining that the first TA value is unavailable, prohibit initiation of a third RA procedure for the first candidate cell to obtain a TA; declare RA failure; determine whether the time elapsed since the first TA value was deemed unavailable is less than or equal to a second time period, and prohibit initiation of the third RA procedure in response to determining that the elapsed time is less than or equal to the second time period; and initiate the third RA procedure after determining that the first TA value is unavailable.

[0015] In some embodiments, the processor of the UE is configured to transmit failure-related information to the first candidate cell in response to successfully obtaining the first TA value by executing the third RA procedure, and wherein the failure-related information indicates that the first TA value was not available before initiating the third RA procedure.

[0016] In some embodiments, the processor of the UE is configured to perform a compliance check operation at the following times: after receiving the RRC reconfiguration message; after receiving the RRC reconfiguration message and before initiating the one or more RA procedures; after receiving the RRC reconfiguration message and before the UE is triggered to perform the one or more RA procedures; after initiating the one or more RA procedures; or after the UE is triggered to perform the one or more RA procedures.

[0017] In some embodiments, in response to successful completion of the compliance checking operation, the processor of the UE is configured to perform the one or more RA procedures.

[0018] In some embodiments, in response to successful completion of the compliance check operation and after receiving the first indication, the processor of the UE is configured to perform at least one of the following: transmitting the first indication to the RRC layer of the UE by the lower layer of the UE; or applying, by the RRC layer of the UE, second configuration information about the first candidate cell within the first configuration information.

[0019] In some embodiments, in response to the occurrence of a failure of the compliance check operation, the processor of the UE is configured to transmit a second message to the source cell via the transceiver, and wherein the second message includes at least one of: an identifier (ID) of a second candidate cell within the one or more candidate cells, wherein the second candidate cell is associated with the failure of the compliance check operation; an index of the RRC reconfiguration message of the second candidate cell; or a fourth indication for indicating the failure of the compliance check operation.

[0020] In some embodiments, the second message is at least one of: a Master Cell Group (MCG) Failure Information message; a Secondary Cell Group (SCG) Failure Information message; or a UE Assistance Information message.

[0021] In some embodiments, the one or more reference signals include at least one of: a preamble; or a sounding reference signal (SRS).

[0022] In some embodiments, the processor of the UE is configured to: receive, via the transceiver, third configuration information regarding the one or more reference signals generated by the first candidate cell; and transmit, via the transceiver, the one or more reference signals to the first candidate cell based on the third configuration information.

[0023] In some embodiments, the third configuration information includes a configuration of a first time-frequency domain resource associated with the SRS, and wherein, in order to transmit the one or more reference signals, the processor of the UE is configured to transmit the SRS to the first candidate cell via the transceiver on the first time-frequency domain resource.

[0024] In some embodiments, the third configuration information includes a configuration of second time-frequency domain resources associated with a preamble, and wherein, in order to transmit the one or more reference signals, the processor of the UE is configured to transmit the preamble to the first candidate cell via the transceiver on the second time-frequency domain resources.

[0025] In some embodiments, to transmit the one or more reference signals, the processor of the UE is configured to transmit the preamble to the first candidate cell during a time gap.

[0026] In some embodiments, the processor of the UE is configured to refrain from desiring to monitor for a response after transmitting the preamble.

[0027] In some embodiments, the processor of the UE is configured to receive a third message from the source cell via the transceiver, and wherein the third message includes at least one of the following: at least one TA value associated with at least one candidate cell within the one or more candidate cells; or at least one identifier (ID) of the at least one candidate cell.

[0028] In some embodiments, the third message is at least one of: downlink control information (DCI); a medium access control (MAC) control element (CE); or a RRC message.

[0029] Some embodiments of the present application provide a centralized unit (CU). The CU includes: a transceiver; and a processor, which is coupled to the transceiver; and the processor is configured to transmit information to a user equipment (UE) via the transceiver, and the information includes at least one of the following: configuration information about one or more candidate cells; at least one timing advance (TA) value related to at least one candidate cell within the one or more candidate cells; or at least one identifier (ID) of the at least one candidate cell.

[0030] In some embodiments, the information is included in at least one of: downlink control information (DCI); a medium access control (MAC) control element (CE); or a RRC message.

[0031] In some embodiments, the processor of the CU is configured to receive, via the transceiver, at least one of: the at least one TA value associated with the at least one candidate cell within the one or more candidate cells; or the at least one ID of the at least one candidate cell.

[0032] In some embodiments, the processor of the CU is configured to transmit a radio resource control (RRC) message to the UE via the transceiver, and wherein the RRC message includes a first indication associated with a cell change of a first candidate cell within the one or more candidate cells.

[0033] In some embodiments, the processor of the CU is configured to transmit an indication to a source DU managed by the CU via the transceiver, and wherein the indication instructs the source DU to transmit a first indication associated with a cell change of a first candidate cell within the one or more candidate cells to the UE.

[0034] In some embodiments, in response to the first candidate cell being a primary-secondary cell group cell (PSCell), the CU is associated with a secondary node (SN) or a master node (MN).

[0035] In some embodiments, the processor of the CU is configured to receive a first message from the UE via the transceiver, and wherein the first message includes at least one of: a second indication indicating that the UE failed to obtain one or more TA values ​​associated with the one or more candidate cells; or a third indication indicating that the one or more random access (RA) procedures performed by the UE are for obtaining the one or more TA values.

[0036] In some embodiments, the processor of the CU is configured to receive a second message from the UE via the transceiver, and wherein the second message includes at least one of: an identifier (ID) of a second candidate cell within the one or more candidate cells, wherein the second candidate cell is associated with a failure of a compliance check operation performed by the UE; an index of the RRC reconfiguration message of the second candidate cell; or a fourth indication for indicating the failure of the compliance check operation.

[0037] In some embodiments, the second message is at least one of: a Master Cell Group (MCG) Failure Information message; a Secondary Cell Group (SCG) Failure Information message; or a UE Assistance Information message.

[0038] Some embodiments of the present application provide a target distributed unit (DU). The target DU includes: a transceiver; and a processor coupled to the transceiver; and the processor is configured to transmit information to a centralized unit (CU) via the transceiver, wherein the information includes at least one of the following: at least one timing advance (TA) value related to at least one candidate cell among one or more candidate cells of a user equipment (UE); or at least one identifier (ID) of the at least one candidate cell.

[0039] In some embodiments, the information is transmitted to the CU via an F1 interface.

[0040] In some embodiments, the processor of the target DU is configured to receive one or more reference signals from the UE via the transceiver.

[0041] In some embodiments, the processor of the target DU is configured to: monitor the one or more reference signals; and calculate the at least one TA value associated with the at least one candidate cell based on the one or more reference signals.

[0042] In some embodiments, the one or more reference signals include at least one of: a preamble; or a sounding reference signal (SRS).

[0043] In some embodiments, in response to the one or more reference signals including the preamble, the processor of the target DU is configured to refrain from transmitting a response after receiving the preamble.

[0044] In some embodiments, the processor of the target DU is configured to generate configuration information regarding the one or more reference signals.

[0045] In some embodiments, the processor of the target DU is configured to transmit the configuration information regarding the one or more reference signals to the CU via the transceiver.

[0046] In some embodiments, the configuration information includes configuration of time-frequency domain resources associated with the one or more reference signals, and wherein the one or more reference signals are received on the time-frequency domain resources.

[0047] Some embodiments of the present application provide a method performed by a UE. The method includes: receiving a radio resource control (RRC) reconfiguration message, wherein the RRC reconfiguration message includes first configuration information about one or more candidate cells; after receiving the RRC reconfiguration message, obtaining one or more timing advance (TA) values ​​related to the one or more candidate cells by performing one or more random access (RA) procedures or by transmitting one or more reference signals to the one or more candidate cells; and after receiving a first indication associated with a first candidate cell in the one or more candidate cells from a source cell, switching from the source cell to the first candidate cell.

[0048] Some embodiments of the present application provide a method performed by a centralized unit (CU). The method includes: transmitting information to a user equipment (UE), wherein the information includes at least one of the following: configuration information about one or more candidate cells; at least one timing advance (TA) value associated with at least one candidate cell within the one or more candidate cells; or at least one identifier (ID) of the at least one candidate cell.

[0049] Some embodiments of the present application provide a method performed by a target distributed unit (DU). The method includes: transmitting information to a centralized unit (CU), wherein the information includes at least one of the following: at least one timing advance (TA) value associated with at least one candidate cell among one or more candidate cells of a user equipment (UE); or at least one identifier (ID) of the at least one candidate cell.

[0050] 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 system; a transmitting circuit system; and a processor coupled to the non-transitory computer-readable medium, the receiving circuit system, and the transmitting circuit system, 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).

[0051] 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

[0052] 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 presented by reference to specific embodiments of the present application illustrated in the accompanying drawings. These drawings depict only example embodiments of the present application and are therefore not to be considered limiting of its scope.

[0053] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present application.

[0054] Figure 2 Schematic diagram illustrating inter-cell layer 1 / layer 2 (L1 / L2) mobility according to some embodiments of the present application.

[0055] Figure 3 An exemplary signaling flow for lower layer-based handover according to some embodiments of the present application is described.

[0056] Figure 4 An exemplary flow chart illustrating obtaining TA according to some embodiments of the present application.

[0057] Figures 5 to 8 An exemplary flow chart illustrating performing a cell change procedure according to some embodiments of the present application.

[0058] Fig. 9 A block diagram illustrating an exemplary apparatus according to some embodiments of the present application. DETAILED DESCRIPTION

[0059] The detailed description of the accompanying drawings is intended as a description of the preferred embodiments of the present application, and 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 accomplished by different embodiments intended to be included in the spirit and scope of the present application.

[0060] 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 (e.g., 3GPP 5G, 3GPP LTE Release 8, etc.). It is considered that, with the development of network architectures and new service scenarios, all embodiments in the present application are also applicable to similar technical problems; and in addition, the terms cited in the present application may be changed, which should not affect the principles of the present application.

[0061] Figure 1 A schematic diagram illustrating 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 it is considered that in some other embodiments of the present application, the wireless communication system 100 may include more or fewer BSs and UEs.

[0062] 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.

[0063] BS 101 may communicate with a core network (CN) node (not shown) via an interface, such as a mobility management entity (MME) or a serving gateway (S-GW), a mobility management function (AMF), or a user plane function (UPF). A BS may also be referred to as an access point, an access terminal, a base station, a macro cell, a Node B, an enhanced Node B (eNB), a gNB, a home Node B, a relay node or a device, or described using other terms used in the art. In 5G NR, a BS may also be referred to as a RAN node or a network device. Each BS may serve several UEs within a service area, such as a cell or a cell sector, via a wireless communication link. Neighboring BSs may communicate with each other when necessary, for example, during a handover procedure of a UE.

[0064] 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), or the like. 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 bracelet, an optical head-mounted display, or the like. 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 the art. UE 102 may communicate directly with BS 101 via uplink (UL) communication signals.

[0065] In 3GPP Release 18, support for inter-cell mobility based on layer 1 / layer 2 (L1 / L2) signaling has been discussed. Specifically, the UE may be provided with configurations from multiple cells in advance, and the BS (e.g., gNB) may switch the UE to a new cell using L1 / L2 signaling, taking into account received physical layer measurement results. According to 3GPP standard documents, a BS may consist of a BS centralized unit (CU) and one or more BS distributed units (DUs). The BS-CU and the BS-DU are connected via the F1 interface, which is a logical interface. One BS-DU is connected to only one BS-CU.

[0066] Figure 2 Schematic diagram illustrating inter-cell layer 1 / layer 2 (L1 / L2) mobility according to some embodiments of the present application. Figure 2 As shown in FIG, 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.

[0067] 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 CU shown in FIG. 4 makes mobility decisions based on received radio resource management (RRM) measurement reports. Unlike conventional L3 mobility, in L1 / L2 mobility, the DU (e.g., Figure 2 DU1 or DU2 shown in Figure 1 makes mobility decisions based on physical layer measurements carried, for example, in channel state information (CSI) reports. In addition, in traditional L3 mobility, the handover command is sent from the SN CU to the UE via an RRC message, while in L1 / L2 mobility, the "handover" command is sent from the DU to the UE via L1 / L2 signaling (e.g., downlink control information (DCI) or medium 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 service PCell while deactivating the old service PCell.

[0068] Figure 3 An exemplary signaling flow for lower layer-based handover according to some embodiments of the present application is described. Figure 3 The signaling flow in describes the procedure of dynamic switching. Dynamic switching can be triggered by lower layer commands. Possible ways include DCI or MAC CE to activate cell change. L1 measurement results can be used to determine whether cell change is triggered. Therefore, DCI can be used. Otherwise, the physical layer needs to indicate the switching decision to the MAC layer. Then, the MAC entity can generate a MAC CE and deliver it to the physical layer.

[0069] Specifically, in Figure 3 In the exemplary signaling process 300 shown in FIG. 3 , in operation 310 , UE 301 accesses serving cell 302 . In operation 311 , UE 301 reports L3 measurement results based on the configuration from serving cell 302 .

[0070] In operation 312, the serving cell 302 decides to hand over the UE 301 to a candidate cell based on the measurement result. Next, in operation 313, the target DU will prepare configuration for one or more candidate cells.

[0071] In operation 314, the serving cell 302 transmits an RRC reconfiguration message including one or more candidate cells to the UE 301. In operation 315, the UE 301 responds to the serving cell 302 by transmitting an RRC reconfiguration complete message.

[0072] In operation 316 (optional), UE 301 may ensure UL or DL ​​synchronization before receiving DCI or MAC CE indication. For example, UE 301 may obtain TA via a random access (RA) procedure. In operation 317, UE 301 may report L1 measurement results for dynamic switching purposes.

[0073] In operation 318, the serving cell 302 transmits a lower layer command to the UE 301. In operation 319, the UE 301 may apply the RRC reconfiguration message and transmit / receive data after receiving the lower layer command.

[0074] Currently, the problem of UL synchronization failure and compliance check in the case of lower layer-based mobility has not been solved. Embodiments of the present application are intended to solve such problems. For example, some embodiments of the present application study the use case in which the UE receives the configuration of the candidate cell. Before performing a primary cell (SpCell) change of a primary or secondary cell group or performing a secondary cell (SCell) change, the UE is expected to obtain the TA via the RA procedure. Some embodiments of the present application study the behavior of the UE in the event of a failure of the RA for obtaining the TA. Some embodiments of the present application study a mechanism for how to handle the situation where the TA is not available when the UE receives a DCI or MAC CE indication. Some embodiments of the present application study a mechanism for when to perform a compliance check and how to handle the situation where the compliance check fails.

[0075] Some embodiments of the present application study a use case in which the UE transmits a preamble or SRS based on configuration information. For example, a neighboring cell may monitor the preamble or SRS and calculate the TA. The neighboring cell may transmit the TA to the serving cell. Then, the serving cell may transmit the TA to the UE. Some embodiments of the present application study a mechanism in which the UE may transmit a preamble or SRS based on configuration information to obtain the TA, and the UE may obtain the TA from the serving cell after the serving cell obtains the TA from the target cell.

[0076] Specifically, in the present application Figures 4 to 9 In the embodiment of the present invention, both inter-DU mobility scenarios and intra-DU mobility scenarios are considered. Inter-DU mobility means that the connection to the CU remains the same, and the UE can change from a source cell associated with a source DU to a target cell associated with a target DU due to mobility, and both the source DU and the target DU are managed by the CU. Intra-DU mobility means that the connection to the CU remains the same, and the UE can change from a source cell to a target cell associated with the same DU due to mobility. More details will be described below in conjunction with the accompanying drawings.

[0077] Figure 4 An exemplary flow chart illustrating obtaining TA according to some embodiments of the present application. Figure 4 The exemplary flowchart 400 in the embodiment of the present invention may be performed by a UE (eg, Figure 1 Although described with respect to a UE, it should be understood that other devices may be configured to perform the same Figure 4 The details described in all other embodiments of this 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 of 5 to 9.

[0078] exist Figure 4 In the exemplary flowchart 400 shown in FIG. 4 , in operation 401, the UE may receive an RRC reconfiguration message. The RRC reconfiguration message includes configuration information about one or more candidate cells (simply labeled as configuration#1). In some embodiments, the target DU (e.g., Figure 2 DU1 shown and described in FIG. 1 ) generates configuration # 1 and transmits configuration # 1 to the CU via the F1 interface (eg, Figure 2 ). Then, the CU sends a RRC reconfiguration message, such as via the source DU (e.g., Figure 2 DU2) shown and described in FIG. 1 transmits configuration #1 to the UE.

[0079] exist Figure 4 In operation 402 shown in , after receiving the RRC reconfiguration message, the UE may obtain one or more TA values ​​associated with one or more candidate cells "by performing one or more RA procedures on the one or more candidate cells" or "by transmitting one or more reference signals to the one or more candidate cells."

[0080] exist Figure 4 In operation 403 shown in FIG. 1 , the UE may switch from the source cell to the candidate cell #1 after receiving an indication (simply labeled as indication #1) associated with a candidate cell (simply labeled as candidate cell #1) among the one or more candidate cells from the source cell. Indication #1 may be associated with a cell change or a cell switch to the candidate cell #1.

[0081] In some embodiments, the RRC reconfiguration message received in operation 401 includes at least one of the following:

[0082] (1) The value of the timer for RA for obtaining the TA. The timer may be simply labeled as timer#1. For example, if a timer "T" is configured for the RA procedure for obtaining the TA, the UE may start the timer after the RA procedure for obtaining the TA is started. The UE may stop the timer after completing the RA procedure for obtaining the TA.

[0083] (2) Maximum total number of preamble transmissions: Once the maximum number of preamble transmissions is reached, the UE considers that the RA procedure for obtaining the TA has failed.

[0084] In an embodiment, after receiving the RRC reconfiguration message including the value of timer#1, the UE may start timer#1 in response to initiating an RA procedure (simply labeled as RA procedure#1) for obtaining TA within the one or more RA procedures, and timer#1 is associated with RA procedure#1. In an embodiment, the UE may stop timer#1 in response to successfully obtaining the TA value associated with the candidate cell by performing RA procedure#1 on the candidate cell within the one or more candidate cells. In an embodiment, the UE may consider RA procedure#1 to have failed in response to the expiration of timer#1.

[0085] In an embodiment, after receiving the RRC reconfiguration message including the maximum total number of preamble transmissions, the UE may consider RA procedure #2 failed in response to reaching the maximum total number of preamble transmissions during an RA procedure (simply denoted as RA procedure #2) for acquiring a TA within one or more RA procedures. The maximum total number of preamble transmissions is associated with RA procedure #2.

[0086] In some embodiments, in response to failure to obtain one or more TA values ​​by performing one or more RA procedures (e.g., failure of RA to obtain TA, which may also be referred to as “RA failure” or the like), the UE may perform one of the following:

[0087] (1) The UE may transmit a message (simply labeled as message#1) to the source cell. For example, a new trigger condition is introduced to transmit message#1 including failure-related information via the RRC layer or the MAC layer. For example, after a failure in obtaining a RA for a TA, the UE reports the failure-related information to the serving cell. In some embodiments, message#1 includes at least one of the following:

[0088] a) An indication used to indicate that the UE failed to obtain one or more TA values ​​associated with one or more candidate cells.

[0089] b) An indication for indicating that one or more RA procedures are for obtaining one or more TA values. This indication may indicate that the intention of one or more RA procedures is to obtain TA. This indication may be added to message #1 triggered by the failure of RA for obtaining TA. A specific example is Figure 5 The embodiments are described as follows.

[0090] (2) The UE may suspend configuration #1 included in the RRC reconfiguration message. Then, the BS (e.g., gNB) may reconfigure configuration information about one or more candidate cells.

[0091] (3) The UE may restart one or more RA procedures for one or more candidate cells for obtaining a TA after a certain period of time. For example, the period of time may be (pre-)configured by the BS (e.g., gNB). In this way, the UE may not suspend configuration #1. That is, even after receiving a DCI or MAC CE indication (e.g., indication #1), the UE does not apply this configuration information.

[0092] In some embodiments, the indication #1 in operation 403 is included in an RRC message. For example, the CU may transmit an RRC message including the indication #1 to the UE.

[0093] In some other embodiments, indication #1 is included in the DCI or MAC CE. For example, the CU may send a signal to a source DU (e.g., Figure 2 DU2) transmits another indication to instruct the source DU to transmit indication #1 to the UE. For example, the source DU may decide to activate a cell change to a candidate cell. The source DU may directly transmit a DCI or MAC CE including indication #1 to the UE.

[0094] In some embodiments, in response to candidate cell#1 being a PSCell, indication#1 may be received by the UE from at least one of the SN or the MN. In some embodiments, the UE may start a handover timer (e.g., T304 defined in the 3GPP standard document) after the RRC layer of the UE receives indication#1 from the lower layer of the UE.

[0095] In some embodiments, after receiving indication #1, the UE may determine whether the TA value associated with candidate cell #1 (simply denoted as TA value #1) is available. In response to determining that TA value #1 is not available, the UE may perform one of the following:

[0096] (1) After determining that TA value #1 is unavailable, the UE may refrain from initiating another RA procedure (simply labeled as RA procedure #3) for candidate cell #1 to obtain the TA.

[0097] (2) The UE may declare RA failure.

[0098] (3) The UE may declare mobility failure.

[0099] (4) The UE may determine whether the "time elapsed since TA value #1 was deemed unavailable" is less than or equal to a certain period (e.g., which is (pre-)configured by the BS), and may refrain from initiating RA procedure #3 in response to determining that the elapsed time is less than or equal to the period.

[0100] (5) The UE may initiate RA procedure #3 after determining that TA value #1 is unavailable.

[0101] In some embodiments, in order to determine whether TA value #1 is available, the UE may determine whether TA value #1 is obtained. If TA value #1 has not been obtained, the UE may determine that TA value #1 is not available. If TA value #1 has been obtained, the UE may further determine whether TA value #1 is valid. For example, the UE may determine whether TA value #1 is valid based on a (pre-)configured time period or based on a change in reference signal received power (RSRP). If the UE determines that TA value #1 is invalid, the UE may determine that TA value #1 is not available.

[0102] In some embodiments, the UE may transmit failure-related information to candidate cell #1 in response to successfully obtaining TA value #1 by performing RA procedure #3. The failure-related information may indicate that TA value #1 was not available before initiating RA procedure #3. Figure 6 The embodiments are described as follows.

[0103] In some embodiments, the UE may perform a compliance check operation at any of the following time points:

[0104] (1) Figure 4 After receiving the RRC reconfiguration message in operation 401 shown in FIG;

[0105] (2) after receiving the RRC reconfiguration message and before initiating one or more RA procedures for obtaining the TA;

[0106] (3) after receiving the RRC reconfiguration message and before the UE is triggered to perform one or more RA procedures for obtaining the TA;

[0107] (4) after initiating one or more RA procedures for obtaining a TA; or

[0108] (5) After the UE is triggered to perform one or more RA procedures for obtaining a TA.

[0109] In some embodiments, in response to successful completion of the compliance check operation, the UE may perform one or more RA procedures for obtaining a TA.

[0110] In some embodiments, in response to successful completion of the compliance check operation and upon receiving indication #1, the UE may perform at least one of the following:

[0111] (1) The lower layer of the UE may transmit indication#1 to the RRC layer of the UE.

[0112] (2) The RRC layer of the UE may apply “configuration information about candidate cell#1 in configuration#1”.

[0113] In some embodiments, in response to the occurrence of a failure of the compliance check operation, the UE may transmit another message (simply labeled as message #2) to the source cell. The failure of the compliance check operation may also be referred to as "compliance check failure" or the like. Message #2 may include at least one of the following:

[0114] (1) An ID of a candidate cell among the one or more candidate cells (simply denoted as candidate cell#2). Candidate cell#2 is associated with a failure of the compliance check operation.

[0115] (2) Index of the RRC reconfiguration message of candidate cell#2.

[0116] (3) An indication indicating a failure of a compliance check operation.

[0117] In some embodiments, message#2 may be: an MCG failure information message; an SCG failure information message; and / or a UE assistance information message. Figure 7 The embodiments are described as follows.

[0118] In some embodiments, Figure 4 The one or more reference signals transmitted to one or more candidate cells in operation 402 shown in may include a preamble and / or an SRS.

[0119] In some embodiments, the UE may receive configuration information about one or more reference signals (simply labeled as configuration#3). For example, configuration#3 may be generated by candidate cell#1 or other candidate cells in the one or more candidate cells. The UE may transmit one or more reference signals to candidate cell#1 based on configuration#3.

[0120] In an embodiment, configuration #3 includes configuration of time-frequency domain resources associated with SRS. UE may transmit SRS to candidate cell #1 on this time-frequency domain resources.

[0121] In another embodiment, configuration#3 includes configuration of time-frequency domain resources associated with the preamble. The UE may transmit the preamble to candidate cell#1 on the time-frequency domain resources.

[0122] In some embodiments, the UE may transmit a preamble to candidate cell#1 during the time gap. In some embodiments, the UE may prohibit the expectation of monitoring for a response (e.g., a random access response (RAR)) after transmitting the preamble. That is, the UE does not expect to monitor for a response (e.g., a RAR) after transmitting the preamble.

[0123] In some embodiments, the UE may receive another message (simply labeled as message#3) from the source cell. Message#3 may include at least one of the following:

[0124] (1) At least one TA value associated with at least one candidate cell among the one or more candidate cells.

[0125] (2) At least one ID of at least one candidate cell.

[0126] In some embodiments, message #3 is at least one of: a MAC CE; or an RRC message. For example, multiple TA values ​​and multiple IDs of corresponding candidate cells can be carried in a single DCI segment, a single MAC CE, or a single RRC message. Figure 8 The embodiments are described as follows.

[0127] Some other embodiments of the present application refer to the CU (e.g., Figure 2 1 and 2. The exemplary flowchart of the CU shown and described in the embodiment of the present invention is executed. Although described with respect to the CU, it should be understood that other devices can be configured to execute similar flowcharts. The details described in all other embodiments of the present application are applicable to this exemplary flowchart.

[0128] Specifically, in the exemplary flow chart, the CU sends a signal to the UE (eg, Figure 1 The UE 102 shown and described in FIG. 1 transmits information. The information may include at least one of the following:

[0129] (1) Configuration information about one or more candidate cells (e.g. Figure 4 In some embodiments, the target DU (e.g., Figure 2 1) generates configuration #1 and transmits configuration #1 to the CU via the F1 interface. Then, the CU sends the configuration #1 to the CU in an RRC reconfiguration message, for example, via the source DU (e.g., Figure 2 DU2) shown and described in FIG. 1 transmits configuration #1 to the UE.

[0130] (2) At least one TA value associated with at least one candidate cell among the one or more candidate cells.

[0131] (3) At least one ID of at least one candidate cell.

[0132] In some embodiments, the information is included in at least one of: a DCI; a MAC CE; or an RRC message.

[0133] In some embodiments, a CU may select a target DU (e.g., Figure 2 DU1) as shown and described in the specification receives at least one of the following:

[0134] (1) At least one TA value associated with at least one candidate cell among the one or more candidate cells.

[0135] (2) At least one ID of at least one candidate cell. Figure 8 The embodiments are described as follows.

[0136] In some embodiments, the CU may transmit an RRC message to the UE. The RRC message may include information related to a candidate cell (e.g., Figure 4 The indication associated with the cell change of candidate cell#1) described in the embodiment of Figure 4 indication #1) described in the embodiments of the present invention.

[0137] In some other embodiments, the CU may send a request to a source DU (e.g., Figure 2The source DU may transmit another indication to the UE in accordance with the embodiment of the present invention. The source DU may transmit an indication #1 associated with a cell change to a candidate cell #1 to the UE in accordance with the embodiment of the present invention. For example, the source DU may decide to activate a cell change to a candidate cell. The source DU may directly transmit a DCI or MAC CE including indication #1 to the UE.

[0138] In some embodiments, in response to candidate cell#1 being a PSCell, the CU is associated with a SN or a MN. Figure 6 The embodiments are described as follows.

[0139] In some embodiments, the CU may receive a message from the UE (eg, Figure 4 Message #1 described in the embodiment of FIG. 1 ). Message #1 may include at least one of the following:

[0140] (1) An indication used to indicate that the UE failed to obtain one or more TA values ​​associated with one or more candidate cells.

[0141] (2) An indication used to indicate that one or more RA procedures performed by the UE are used to obtain one or more TA values.

[0142] In some embodiments, the CU may receive another message from the UE (eg, Figure 4 message#2 described in the embodiment of FIG. 1 ). message#2 includes at least one of the following:

[0143] (1) ID of a candidate cell within one or more candidate cells (e.g., Figure 4 candidate cell#2 described in the embodiment of the present invention). candidate cell#2 is associated with a failure of a compliance check operation performed by the UE.

[0144] (2) Index of the RRC reconfiguration message of candidate cell#2.

[0145] (3) An indication indicating a failure of a compliance check operation.

[0146] In some embodiments, message #2 is at least one of: an MCG failure information message; an SCG failure information message; and / or a UE assistance information message. Figure 7 The embodiments are described as follows.

[0147] Some additional embodiments of the present application refer to a target DU (e.g., Figure 21 or 2) shown and described in the exemplary flowchart of the DU1 or DU2 executed. Although described with respect to the target DU, it should be understood that other devices can be configured to execute similar flowcharts. The details described in all other embodiments of the present application are applicable to this exemplary flowchart.

[0148] Specifically, in the exemplary flowchart, the target DU may send a signal to the CU (eg, Figure 2 The information includes at least one of the following:

[0149] (1) With UE (e.g. Figure 1 At least one TA value associated with at least one candidate cell within one or more candidate cells of the UE 102 shown and described in FIG.

[0150] (2) At least one ID of at least one candidate cell.

[0151] In some embodiments, the information is transmitted to the CU via the F1 interface.

[0152] In some embodiments, the target DU may receive one or more reference signals from the UE. In some embodiments, the target DU may monitor the one or more reference signals and calculate at least one TA value associated with at least one candidate cell based on the one or more reference signals.

[0153] In some embodiments, the one or more reference signals include a preamble and / or an SRS. In an embodiment, in response to the one or more reference signals including a preamble, the target DU may refrain from transmitting a response (eg, a RAR) after receiving the preamble.

[0154] In some embodiments, the target DU may generate configuration information about one or more reference signals (e.g., Figure 4 In some embodiments, the target DU may transmit configuration information about one or more reference signals to the CU, for example, via an F1 interface.

[0155] In some embodiments, the configuration information includes a configuration of a time-frequency domain resource associated with one or more reference signals. The one or more reference signals may be received on the time-frequency domain resource. Figure 8 The embodiments are described as follows.

[0156] Figure 5 An exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application. The details described in all other embodiments of the present application apply to Figure 5 The embodiments shown in FIG. A person skilled in the art will appreciate that Figure 5 The sequence of operations in the exemplary flowchart 500 may be modified and Figure 5 Some operations in the exemplary flowchart 500 may be omitted or modified without departing from the spirit and scope of the present disclosure.

[0157] like Figure 5 As shown in FIG. 5 , BS 505 has a CU-DU architecture and includes CU 504, source DU 502, and target DU 503. Figure 5 In the embodiment of , the cell change of UE 501 may refer to an intra-DU situation where the source cell and the target cell are in the same DU or to an inter-DU situation where the source cell and the target cell are located at different DUs. For example, for exemplary purposes, Figure 5 The flowchart 500 shown in FIG. 5 only shows the cell change in the inter-DU case.

[0158] exist Figure 5 In the exemplary flow chart 500 shown in FIG. 5 , in operation 511, the UE 501 reports, to a serving cell associated with the CU 504, for example, an indication indicating that the UE 501 supports a capability of cell change based on DCI or MAC CE.

[0159] In operation 512, the UE 501 reports the measurement result via an RRC message to, for example, a serving cell related to the CU 504. For example, the UE 501 may report the measurement result based on an RRC reconfiguration including a measurement configuration.

[0160] In operation 513, UE 501 receives the configuration of the candidate cell from CU 504, for example, in an RRC reconfiguration message. In some embodiments, the configuration may include the value of the timer (e.g., the length of "T") and / or the maximum total number of preamble transmissions. Some parameters in the configuration of the candidate cell are generated from target DU 503.

[0161] In an embodiment, if a timer (e.g., "T") is configured, the UE 501 may start the timer after the initiation of the RA procedure for obtaining the TA. The UE 501 may stop the timer after completing the RA procedure for obtaining the TA. In some cases, the "RA procedure for obtaining the TA" may also be referred to as the "RA procedure for obtaining an early TA" or the like.

[0162] The maximum total number of preamble transmissions may be used to determine whether the RA procedure has failed. In an embodiment, if the configuration contains the maximum total number of preamble transmissions, once the maximum total number of preamble transmissions is reached, the UE 501 considers the RA procedure to have failed.

[0163] In operation 514, after UE 501 receives the configuration of the candidate cell from CU 504, UE 501 performs a RA procedure for obtaining a TA for the candidate cell. Figure 5 The target DU 503 shown in FIG. 5 performs the RA procedure.

[0164] In operation 515 , the UE 501 performs measurement on the serving cell and the candidate cell and reports the L1 measurement result to the source DU 502 .

[0165] In some embodiments, there is a certain period of time between receiving the configuration of the candidate cell and receiving the DCI or MAC CE indication. UE 501 does not know the time point when the DCI or MAC CE indication is received. UE 501 will perform the RA procedure for obtaining the TA. However, UE 501 may fail to obtain the TA via the RA procedure. If a timer (e.g., "T") is configured, UE 501 starts the timer after the start of the RA procedure for obtaining the TA. UE 501 stops the timer after completing the RA procedure for obtaining the TA. If the maximum total number of preamble transmissions is configured, UE 501 considers that the RA procedure has failed once the maximum total number of preamble transmissions is reached.

[0166] In some embodiments, after UE 501 fails to obtain a TA via the RA procedure, UE 501 may perform the following actions in different embodiments, namely, operation 516A or operation 516B.

[0167] In operation 516A (optional), UE 501 reports the failure-related information to, for example, a serving cell associated with SpCell. The failure-related information may be carried in an RRC message or a MAC CE.

[0168] In some embodiments, a new trigger condition is introduced to transmit a message containing failure related information (e.g., Figure 4 For example, UE 501 reports failure-related information to the serving cell after the failure of the RA procedure for obtaining the TA.

[0169] In some embodiments, a new indication for the purpose of obtaining a TA may be added in a message (eg, message #1) triggered by a failure of a RA procedure for obtaining a TA. The indication may indicate that the intention of the RA procedure is for obtaining a TA.

[0170] In operation 516B (optional), there may be two options, Option 1 and Option 2, as follows in different embodiments.

[0171] (1) Option 1: UE 501 may suspend configuration of candidate cells. Then, BS 505 may reconfigure configuration of candidate cells.

[0172] (2) Option 2: UE 501 may re-perform the RA procedure after a period configured by BS 505. In this way, UE 501 may not suspend configuration of candidate cells.

[0173] Figure 6 Another exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application. The details described in all other embodiments of the present application apply to Figure 6 The embodiments shown in FIG. A person skilled in the art will appreciate that Figure 6 The sequence of operations in the exemplary flowchart 600 may be modified and Figure 6 Some operations in the exemplary flowchart 600 may be omitted or modified without departing from the spirit and scope of the present disclosure.

[0174] like Figure 6 As shown in FIG. 6 , BS 605 has a CU-DU architecture and includes CU 604, source DU 602, and target DU 603. Figure 6 In the embodiment of , the cell change of UE 601 may refer to an intra-DU situation where the source cell and the target cell are in the same DU or to an inter-DU situation where the source cell and the target cell are located at different DUs. For example, for exemplary purposes, Figure 6 The flowchart 600 shown in FIG. 6 only shows the cell change in the inter-DU case.

[0175] exist Figure 6 In the exemplary flowchart 600 shown in FIG. 6 , in operation 611, the UE 601 reports, to a serving cell associated with, for example, the CU 604, an indication indicating that the UE 601 supports a capability of cell change based on DCI or MAC CE.

[0176] In operation 612, the UE 601 reports the measurement result via an RRC message to, for example, a serving cell related to the CU 604. For example, the UE 601 may report the measurement result based on an RRC reconfiguration including a measurement configuration.

[0177] In operation 613, CU 604 may transmit a request to prepare a configuration for a candidate cell to target DU 603. In operation 613A, target DU 603 generates a configuration of the candidate cell and transmits the configuration of the candidate cell to CU 604, for example, via an F1 interface. In operation 613B, CU 604 transmits the configuration of the candidate cell to UE 601 (e.g., through source DU 602) in an RRC reconfiguration message.

[0178] In operation 614, after UE 601 receives the configuration of the candidate cell from CU 604, UE 601 performs a RA procedure for obtaining a TA on the candidate cell (e.g., associated with target DU 603). In some cases, the "RA procedure for obtaining a TA" may also be referred to as an "RA procedure for obtaining an early TA" or the like.

[0179] In operation 615 , the UE 601 performs measurement on the serving cell and the candidate cell (eg, related to the target DU 603 ) and reports the L1 measurement result to the source DU 602 .

[0180] In some embodiments, in operation 616, the source DU 602 may transmit a DCI or MAC CE indication to the UE 601 to trigger a cell change procedure. For example, the source DU 602 may decide to activate a cell change to a candidate cell. The source DU 602 may directly transmit a DCI or MAC CE indication to the UE 601 including indication #1 (e.g., Figure 4 In some embodiments, CU 604 may transmit an indication to source DU 602, for example, via an F1 interface, to instruct source DU 602 to transmit an indication "associated with a cell change to a candidate cell within a candidate cell" to UE 601.

[0181] In some embodiments, there may be a certain period of time between receiving the configuration of the candidate cell and receiving the DCI or MAC CE indication. UE 601 does not know the time point of receiving the DCI or MAC CE indication. Therefore, the problem of when to perform the RA procedure for obtaining the TA needs to be solved. "Obtaining the TA" means that UE 601 needs to ensure UL synchronization before performing the cell change procedure.

[0182] If the candidate cell is a PSCell, the DCI or MAC CE indication may be transmitted by the SN or MN.

[0183] In some embodiments, the UE 601 may determine whether the TA value associated with the candidate cell is available upon receiving the DCI or MAC CE indication. For example, the UE 601 may determine whether the TA value associated with the candidate cell has been obtained. If the TA value has not been obtained, the UE 601 may determine that the TA value is not available. If the TA value has been obtained, the UE 601 may further determine whether the TA value is valid. If the UE 601 determines that the TA value is invalid, the UE 601 may determine that the TA value is not available.

[0184] In some embodiments, UE 601 starts a handover timer (eg, T304 defined in 3GPP standard documents) when the RRC layer of UE 601 receives a DCI or MAC CE indication from a lower layer of UE 601 .

[0185] In some embodiments, after receiving the DCI or MAC CE indication in operation 616B, UE 501 may perform the following actions in different embodiments, namely, operation 617A or operation 617B.

[0186] In operation 617A (optional), there may be two options, Option A and Option B, as follows in different embodiments.

[0187] (1) Option A: If UE 601 determines that the TA value associated with the candidate cell is not available when receiving the DCI or MAC CE indication, then UE 601 does not perform the RA procedure (e.g., Figure 4 RA procedure #3) described in the embodiment of the present invention, and UE601 may declare RA failure or mobility failure.

[0188] (2) Option B: If UE 601 determines that the TA value associated with the candidate cell is unavailable when receiving the DCI or MAC CE indication and if the time that has passed since the TA value was deemed unavailable is less than or equal to a certain period of time, then UE 601 does not perform the RA procedure (e.g., RA procedure #3), and UE 601 may declare RA failure or mobility failure.

[0189] In operation 617B (optional), if the UE 601 determines that the TA value associated with the candidate cell is not available when receiving the DCI or MAC CE indication, the UE 601 performs an RA procedure (e.g., RA procedure #3) on the candidate cell, for example, associated with the target DU 603. If the RA procedure is successfully performed, the UE 601 will report failure-related information to the target cell (i.e., the candidate cell associated with the target DU 603). The failure-related information may indicate that the TA value associated with the target cell is not available before initiating RA procedure #3.

[0190] Figure 7 Another exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application. The details described in all other embodiments of the present application apply to Figure 7 The embodiments shown in FIG. A person skilled in the art will appreciate that Figure 7 The sequence of operations in the exemplary flowchart 700 may be modified and Figure 7 Some operations in the exemplary flowchart 700 in may be omitted or modified without departing from the spirit and scope of the present disclosure.

[0191] like Figure 7As shown in FIG. 7 , BS 705 has a CU-DU architecture and includes CU 704, source DU 702, and target DU 703. Figure 7 In the embodiment of , the cell change of UE 701 may refer to an intra-DU situation where the source cell and the target cell are in the same DU or to an inter-DU situation where the source cell and the target cell are located at different DUs. For example, for exemplary purposes, Figure 7 The flowchart 700 shown in FIG. 7 only shows the cell change in the inter-DU case.

[0192] exist Figure 7 In the exemplary flow chart 700 shown in FIG. 7 , in operation 711, the UE 701 reports, to a serving cell associated with the CU 704, for example, an indication indicating that the UE 701 supports a capability of cell change based on DCI or MAC CE.

[0193] In operation 712, the UE 701 reports the measurement result via an RRC message to, for example, a serving cell related to the CU 704. For example, the UE 701 may report the measurement result based on an RRC reconfiguration including a measurement configuration.

[0194] In operation 713, UE 701 receives the configuration of the candidate cell from CU 704, for example, in an RRC reconfiguration message. In some embodiments, the configuration of the candidate cell includes the value of the timer (e.g., the length of "T") and / or the maximum total number of preamble transmissions, which is used to determine whether the RA procedure fails. In some embodiments, the target DU 703 generates the configuration of the candidate cell and transmits the configuration of the candidate cell to CU 704, for example, via the F1 interface. Then, in operation 713, CU 704 transmits the configuration of the candidate cell to UE 701 (e.g., through source DU 702) in an RRC reconfiguration message.

[0195] In operation 714, after UE 701 receives the configuration of the candidate cell from the serving cell, UE 701 needs to perform a compliance check operation on the RRC reconfiguration message. In some embodiments, UE 701 may perform a compliance check operation at any of the following time points:

[0196] (1) UE 701 performs a compliance check operation after receiving the RRC reconfiguration message (which includes the configuration of the candidate cells).

[0197] (2) UE 701 performs a compliance check operation after receiving the RRC reconfiguration message and before UE 701 initiates a RA procedure for obtaining a TA.

[0198] (3) UE 701 performs a compliance check operation after receiving the RRC reconfiguration message and before UE 701 is triggered to perform a RA procedure for obtaining a TA.

[0199] (4) UE 701 performs a compliance check operation after UE 701 initiates the RA procedure for obtaining a TA.

[0200] (5) UE 701 performs a compliance check operation after UE 701 is triggered to perform a RA procedure for obtaining a TA.

[0201] After operation 714, UE 501 may perform the following actions in different embodiments, namely, operation 715A or operation 715B.

[0202] In operation 715A (optional), in some embodiments, after the UE 701 successfully performs the compliance check operation, the UE 701 performs a RA procedure for obtaining a TA on, for example, a candidate cell associated with the target DU 703 .

[0203] In some embodiments, after receiving a lower layer command (e.g., a DCI or MAC CE indication for activating a cell change), the lower layer of UE 701 should indicate the DCI or MAC CE indication to the RRC layer of UE 701. Then, the RRC layer of UE 701 may apply the configuration of the candidate cell.

[0204] In operation 715B (optional), if UE 701 fails to complete the compliance check operation, UE 701 may report failure related information to the source cell. For example, for SpCell change or SCell change, failure related information may include the ID of the candidate cell, the index of the RRC reconfiguration of the candidate cell, and / or a compliance check failure indication. For example, UE 701 may perform the following actions in different embodiments of operation 715B to report failure related information. Failure related information may be reported to CU 704 via an RRC message or to source DU 702 via a MAC CE.

[0205] (1) UE 701 may transmit a MCGfailureinformation message containing failure related information.

[0206] (2) UE 701 may transmit an SCGfailureinformation message containing failure related information.

[0207] (3) UE 701 may transmit a UEassistanceinformation message including failure related information. For example, for SpCell change or SCell change, the UEassistanceinformation message may include failure related information, including the ID of the candidate cell, the index of the RRC reconfiguration of the candidate cell and / or a compliance check failure indication.

[0208] Figure 8 Another exemplary flow chart illustrating the execution of a cell change procedure according to some embodiments of the present application. The details described in all other embodiments of the present application apply to Figure 8 The embodiments shown in FIG. A person skilled in the art will appreciate that Figure 8 The sequence of operations in the exemplary flowchart 800 may be modified and Figure 8 Some operations in the exemplary flowchart 800 may be omitted or modified without departing from the spirit and scope of the present disclosure.

[0209] like Figure 8 As shown in FIG. 8 , BS 805 has a CU-DU architecture and includes CU 804, source DU 802, and target DU 803. Figure 8 In the embodiment of , the cell change of UE 801 may refer to an intra-DU situation where the source cell and the target cell are in the same DU or to an inter-DU situation where the source cell and the target cell are located at different DUs. For example, for exemplary purposes, Figure 8 The flowchart 800 shown in FIG. 8 only shows the cell change in the inter-DU case.

[0210] exist Figure 8 In the exemplary flow chart 800 shown in FIG. 8 , in operation 811, the UE 801 reports, to a serving cell associated with, for example, the CU 804, an indication indicating that the UE 801 supports a capability of cell change based on DCI or MAC CE.

[0211] In operation 812, the UE 801 reports the measurement result via an RRC message to, for example, a serving cell related to the CU 804. For example, the UE 801 may report the measurement result based on an RRC reconfiguration including a measurement configuration.

[0212] In operation 813, CU 804 transmits a request for cell change via the F1 interface to, for example, a target cell associated with target DU 803. In some embodiments, CU 804 requests target DU 803 to provide a configuration for obtaining a TA. In some cases, target DU 803 may also be referred to as a "neighboring cell" or a "candidate cell" or a "candidate target cell" or the like.

[0213] In operation 814, for example, a target cell associated with the target DU 803 transmits a response to the CU 804. In some embodiments, the target cell may provide a configuration of an SRS and / or a preamble. With respect to the configured SRS, time-frequency domain resources may also be configured. In operation 816 described below, the UE 801 may transmit an SRS based on the configured time-frequency domain resources. With respect to the configured preamble, in operation 816 described below, the UE 801 may transmit a preamble in the configured time-frequency domain resources or in a time gap. After the UE 801 transmits the preamble, it is not expected that the UE 801 monitors for a response, such as a RAR.

[0214] In some embodiments, in operation 814, the target DU 803 generates a configuration of the candidate cells and transmits the configuration of the candidate cells to the CU 804, for example, via an F1 interface.

[0215] In operation 815, after receiving a response from a target cell, for example, related to the target DU 803, the CU 804 transmits an RRC reconfiguration message including "configuration of candidate cells" and / or "configuration of SRS and / or preamble" to the UE 801 (eg, through the source DU 802).

[0216] In operation 816 , after receiving the configuration of the candidate cell and / or the configuration of the SRS and / or the preamble from the CU 804 , the UE 801 may transmit the SRS and / or the preamble to the target cell related to the target DU 803 , for example, based on the configuration of the candidate cell.

[0217] In some embodiments, the target DU 803 may monitor the SRS and / or the preamble, and may calculate at least one TA value associated with at least one candidate cell based on the SRS and / or the preamble received from the UE 801 in operation 816. After the target DU 803 calculates at least one TA value based on the SRS and / or the preamble, there may be two options, namely, option X and option Y, as follows in different embodiments.

[0218] (1) Option X: Perform operations 817A and 818A.

[0219] a) In operation 817A, the target DU 803 transmits the calculated TA value to the CU 804 via the F1 interface.

[0220] b) In operation 818A, after receiving at least one TA value from the target DU 803, the CU 804 transmits at least one TA value and a cell ID (which is associated with the at least one TA value) of at least one candidate cell to the UE 801 (e.g., through the source DU 802) via an RRC message. For example, multiple TA values ​​and cell IDs corresponding to multiple candidate cells may be carried in a single RRC message.

[0221] (2) Option Y: Execute operations 817A, 817B, and 818B.

[0222] a) In operation 817A, the target DU 803 transmits the calculated at least one TA value to the CU 804, for example via the F1 interface.

[0223] b) In operation 817B, the CU 804 sends at least one candidate cell to the CU 804, for example, via the F1 interface.

[0224] The TA value and cell ID are transmitted to the source DU 802 .

[0225] c) In operation 818B, the source DU 802 transmits at least one TA value and cell ID of at least one candidate cell to the UE 801 via DCI or MAC CE. For example, multiple TA values ​​and cell IDs corresponding to multiple candidate cells may be carried in a single DCI segment or a single MAC CE.

[0226] In operation 819, UE 801 changes the serving cell and starts receiving or transmitting using the pre-configured UE-dedicated channel.

[0227] Fig. 9 900 is a block diagram illustrating an exemplary apparatus 900 according to some embodiments of the present application. Fig. 9 900, the apparatus 900 may include at least one processor 906 and at least one transceiver 902 coupled to the processor 906. Although elements such as at least one transceiver 902 and the processor 906 are described in the singular in this figure, the plural form is contemplated unless limitation to the singular form is explicitly stated. In some embodiments of the present application, the transceiver 902 may be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present application, the apparatus 900 may further include an input device, a memory, and / or other components.

[0228] In some embodiments of the present application, the device 900 may be a UE or a network node (eg, a BS, a CU, or a DU). The transceiver 902 and the processor 906 may interact with each other to execute the above, for example, Figures 1 to 8 The operations of the UE or the network node described in any one of the foregoing.

[0229] In some embodiments of the present application, the device 900 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 to enable the processor 906 to implement the method for the UE or network node (e.g., BS, CU, or DU) as described above. For example, when the computer-executable instructions are executed, the processor 906 interacts with the transceiver 902 to perform the Figures 1 to 8 The operations of the UE or network node described in.

[0230] It will be appreciated by those skilled in the art that the operations or steps of the methods described in conjunction with the aspects disclosed herein may be directly embodied 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 may be incorporated into a computer program product.

[0231] In this document, the term "includes, including" or any other variation thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment containing the element list not only includes those elements but also may include other elements that are not explicitly listed or inherent to this process, method, article or equipment. The element starting with "a / an" or the like does not exclude the existence of additional identical elements in the process, method, article or equipment containing the element without more constraints. Moreover, the term "another" is defined as at least the second or more. As used herein, the term "having" and the like are defined as "including". For example, the expression of "A and / or B" or "at least one of A and B" may include any one and all combinations of the words enumerated together with the expression. For example, the expression "A and / or B" or "at least one of A and B" may include A, B or both A and B. The wording "first", "second" or the like is only used to clearly illustrate the embodiments of the present application, and is not used to limit the substantive content of the present application.

Claims

1. A user equipment UE, comprising: Transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receiving, via the transceiver, a radio resource control (RRC) reconfiguration message, wherein the RRC reconfiguration message includes first configuration information about one or more candidate cells; After receiving the RRC reconfiguration message, obtaining one or more timing advance TA values ​​associated with the one or more candidate cells by performing one or more random access RA procedures or by transmitting one or more reference signals to the one or more candidate cells; and After receiving a first indication associated with a first candidate cell among the one or more candidate cells from a source cell, switching is performed from the source cell to the first candidate cell.

2. The UE according to claim 1, wherein the RRC reconfiguration message comprises at least one of the following: The value of the first timer used to obtain the TA's RA; or Maximum total number of preamble transmissions.

3. The UE of claim 2, wherein after receiving the RRC reconfiguration message including the value of the first timer, the processor of the UE is configured to: The first timer is initiated in response to initiating a first RA procedure for obtaining a TA within the one or more RA procedures, wherein the first timer is associated with the first RA procedure.

4. The UE of claim 3, wherein the processor of the UE is configured to: stopping the first timer in response to successfully obtaining a TA value associated with a candidate cell among the one or more candidate cells by performing the first RA procedure on the candidate cell; or The first RA procedure is deemed to have failed in response to expiration of the first timer.

5. The UE of claim 2, wherein upon receiving the RRC reconfiguration message including the maximum total number of preamble transmissions, the processor of the UE is configured to: A second RA procedure within the one or more RA procedures for obtaining a TA is deemed failed in response to reaching the maximum total number of preamble transmissions during the second RA procedure, wherein the maximum total number of preamble transmissions is associated with the second RA procedure.

6. The UE of claim 1 , wherein in response to failure to obtain the one or more TA values ​​by performing the one or more RA procedures, the processor of the UE is configured to perform one of the following: transmitting, via the transceiver, a first message to the source cell; suspending the first configuration information about the one or more candidate cells; and The one or more RA programs are restarted after the first period of time.

7. The UE according to claim 6, wherein the first message includes at least one of the following: a second indication for indicating that the UE fails to obtain the one or more TA values ​​associated with the one or more candidate cells; or A third indication is used to indicate that the one or more RA procedures are used to obtain the one or more TA values.

8. The UE according to claim 1, wherein the first indication is contained in downlink control information (DCI) or medium access control (MAC) control element (CE). 9 . The UE according to claim 1 , wherein in response to the first candidate cell being a primary-secondary cell group cell (PSCell), the first indication is received by the UE from at least one of a secondary node (SN) or a primary node (MN).

10. The UE of claim 1, wherein the processor of the UE is configured to start a switching timer after an RRC layer of the UE receives the first indication from a lower layer of the UE.

11. The UE of claim 1 , wherein the processor of the UE is configured to: After receiving the first indication, determining whether a first TA value associated with the first candidate cell is available; In response to determining that the first TA value is not available, performing one of the following: After determining that the first TA value is unavailable, prohibiting initiating a third RA procedure for the first candidate cell to obtain a TA; Declare RA failure; determining whether a time elapsed since the first TA value was deemed unavailable is less than or equal to a second period of time, and prohibiting initiation of the third RA procedure in response to determining that the elapsed time is less than or equal to the second period of time; and The third RA procedure is initiated after determining that the first TA value is unavailable.

12. The UE according to claim 11, wherein the processor of the UE is configured to transmit failure-related information to the first candidate cell in response to successfully obtaining the first TA value by executing the third RA procedure, and wherein the failure-related information indicates that the first TA value was not available before the third RA procedure was initiated.

13. The UE of claim 1, wherein the processor of the UE is configured to perform a compliance check operation at the following times: After receiving the RRC reconfiguration message; after receiving the RRC reconfiguration message and before initiating the one or more RA procedures; after receiving the RRC reconfiguration message and before the UE is triggered to perform the one or more RA procedures; After initiation of said one or more RA procedures; or After the UE is triggered to perform the one or more RA procedures.

14. A centralized unit CU, comprising: Transceiver; and a processor coupled to the transceiver, wherein the processor is configured to transmit information to a user equipment (UE) via the transceiver, and wherein the information includes at least one of: configuration information about one or more candidate cells; at least one timing advance (TA) value associated with at least one candidate cell within the one or more candidate cells; or At least one identifier ID of the at least one candidate cell.

15. A target distributed unit DU, comprising: Transceiver; and A processor coupled to the transceiver, wherein the processor is configured to transmit information to a centralized unit (CU) via the transceiver, and wherein the information includes at least one of: at least one timing advance TA value associated with at least one candidate cell of the one or more candidate cells of the user equipment UE; or At least one identifier ID of the at least one candidate cell.

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