Method and apparatus for small data transmission

Abstract

To provide a method and apparatus for small data transmission.SOLUTION: An exemplary method for small data transmission (SDT) includes: transmitting an indication associated with SDT scheme selection for user equipment (UE) from a central unit (CU) to a distributed unit (DU) (in step 302); receiving, by the CU from the DU, first configured granted (CG)-SDT resource configuration information for the UE in the case that CG-SDT is configured (in step 304); transmitting, by the CU to the DU, a radio resource control (RRC) release message for causing the UE to enter into a non-connected state with the first CG-SDT resource configuration information (in step 306); and transferring, by the DU to the UE, the RRC release message with the first CG-SDT resource configuration information to send the UE to a non-connected state (in step 310).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] FIELD Embodiments of the present application generally relate to wireless communication technologies, and more particularly, to methods and apparatus for small data transmission (SDT). [Background technology]

[0002] In 3GPP (registered trademark) (3rd generation partnership project) 5G systems, small data transmission has been introduced for some application scenarios. For example, according to the agreement of 3GPP TSG RAN Meeting #86, small data transmission may be used for smartphone applications, including traffic from instant messaging services, or for non-smartphone applications, including traffic from wearables. Small data transmission may also be referred to as small data packets. In general, any device that has intermittent small data transmission in a non-connected state, such as in a radio resource control (RRC) inactive state or an RRC idle state, would benefit from enabling small data transmission in a non-connected state.

[0003] According to the new radio (NR) Rel-17 work item, there are two methods for small data transmission in the RRC_INACTIVE state: - Uplink (UL) small data transmission using a RACH-based scheme (e.g., using 2-step RACH and 4-step RACH), also called random access (RA)-SDT or RA-based SDT or random access channel (RACH)-based SDT. - UL small data transmission on pre-configured physical uplink shared channel (PUSCH) resources (e.g., reusing CG type 1 PUSCH resources), called configured grant (CG)-SDT or CG-based SDT.

[0004] However, some issues related to CG-SDT have not yet been discussed, such as how a central unit (CU) and distributed unit (DU) split-based radio access network (RAN) architecture determines whether a CU or a DU is responsible for selecting (or deciding) the SDT scheme to be configured for a user equipment (UE); how the CU and DU reconfigure the previous (i.e., old) CG-SDT resource configuration information in a new logical F1 connection associated with the UE when the UE falls back from CG-SDT to RA-SDT or non-SDT; and how the UE context, the logical F1 connection associated with the UE, and the user plane resources between the CU and DU are released when the time alignment timer (TAT)-SDT expires. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above, the industry desires improved techniques for small data transmission, particularly for CG-SDT. [Means for solving the problem]

[0006] One objective of the embodiments of the present application is to provide a technical solution for small data transmission, such as CG-SDT configuration, reconfiguration, and release via the F1 interface.

[0007] According to some embodiments of the present application, a method for SDT includes the steps of: sending an indication associated with an SDT scheme selection for a UE from a CU to a DU; if CG-SDT is configured, receiving first CG-SDT resource configuration information for the UE from the DU by the CU; and sending an RRC release message by the CU to the DU together with the first CG-SDT resource configuration information to transition the UE to a disconnected state.

[0008] In some embodiments of the present application, when the CU determines that CG-SDT is to be configured for the UE, the indication associated with the SDT scheme selection is a CG-SDT request indication or a CG-SDT query indication, and the CG-SDT request indication or the CG-SDT query indication is associated with a data radio bearer (DRB).

[0009] In some embodiments of the present application, the indication associated with the SDT scheme selection is an SDT indication that indicates to the DU whether a DRB or a quality of service (QoS) flow or a protocol data unit (PDU) session is subject to SDT.

[0010] In some embodiments of the present application, the method may include storing, by a CU, first CG-SDT resource configuration information received from a DU. The method may further include receiving, by the CU, an RA-SDT indication from the DU indicating that RA-SDT is to be performed by a UE entering an unconnected state caused by an RRC release message, and transmitting, by the CU, the first CG-SDT resource configuration information to the DU, such that the CG-SDT resource configuration information is reconfigured for the UE based on the first CG-SDT resource configuration information after the RA-SDT. The first CG-SDT resource configuration information is an RRC container transmitted in an RRC container information element (IE) from the CU to the DU, or transmitted in a UE context modification request message.

[0011] In some embodiments of the present application, the method may include receiving, by a CU from a DU, an RA-SDT indication indicating that RA-SDT is to be performed by a UE entering a disconnected state caused by an RRC release message, and transmitting, by the CU, an identity (ID) of the first CG-SDT resource configuration information to the DU, so that the CG-SDT resource configuration information is reconfigured for the UE based on the first CG-SDT resource configuration information after the RA-SDT. The identity of the first CG-SDT resource configuration information is a cell-radio network temporary identifier (C-RNTI) associated with the UE or a DU UE F1 Application Protocol (F1AP) identity associated with the UE, and the DU UE F1AP identity is used to uniquely identify a previous F1 connection associated with the UE for the UE within the DU. The identity of the first CG-SDT resource configuration information is transmitted in a UE context modification request message.

[0012] In some embodiments of the present application, the method may include receiving, by the CU from the DU, second CG-SDT resource configuration information to replace the first CG-SDT resource configuration information, and transmitting, by the CU, another RRC release message for the UE to the DU together with the second CG-SDT resource configuration information. The method may further include storing, by the CU, the second CG-SDT resource configuration information. In some embodiments of the present application, the second CG-SDT resource configuration information is the complete CG-SDT resource configuration information.

[0013] In some embodiments of the present application, the method may include sending, by the CU to the DU, radio link measurement information for CG-SDT resource selection.

[0014] The method may further include receiving, by the CU, a TAT-SDT from the DU, starting the TAT-SDT by the CU in response to triggering a UE context release procedure, and stopping the TAT-SDT by the CU in response to receiving small data or a resume request message. The method may further include releasing, by the CU, a logical F1 connection and an associated UE context associated with the UE in response to expiration of the TAT-SDT.

[0015] In some embodiments of the present application, the method may include a step of receiving, by the CU, a UE context release request message from the DU to request the CU to release a logical F1 connection associated with the UE, wherein the UE context release request message includes a cause value indicating that the UE context release request message is caused by the expiration of the TAT-SDT.

[0016] According to some embodiments of the present application, a method for SDT includes receiving, by a DU from a CU, an indication associated with an SDT scheme selection for a UE; if CG-SDT is configured, sending, by the DU to the CU, first CG-SDT resource configuration information for the UE; and receiving, by the DU from the CU, an RRC release message together with the first CG-SDT resource configuration information to transition the UE to a disconnected state.

[0017] In some embodiments of the present application, the indication associated with the SDT scheme selection is a CG-SDT request indication or a CG-SDT query indication, which indicates to the DU that a CG-SDT needs or is requested to be configured for the UE. The CG-SDT request indication or the CG-SDT query indication is associated with a DRB.

[0018] In some embodiments of the present application, the indication associated with the SDT scheme selection is an SDT indication that indicates to the DU whether the DRB, QoS flow, or PDU session is to undergo SDT, and the method further includes determining whether a CG-SDT is to be configured by the DU. The method may further include storing, by the DU, first CG-SDT resource configuration information and a C-RNTI associated with the UE in response to receiving a UE context release message from the CU. The first CG-SDT resource configuration information is pre-configured in the DU. The method may also include applying, by the DU, the first CG-SDT resource configuration information when releasing the UE to an unconnected state.

[0019] In some embodiments of the present application, the method may include: sending, by the DU to the CU, an RA-SDT indication indicating that RA-SDT is to be performed by a UE that has entered a disconnected state caused by an RRC release message; and receiving, by the DU from the CU, first CG-SDT resource configuration information such that the CG-SDT resource configuration information is reconfigured for the UE based on the first CG-SDT resource configuration information after the RA-SDT.

[0020] In some embodiments of the present application, the method may include: sending, by the DU to the CU, an RA-SDT indication indicating that RA-SDT is to be performed by a UE that has entered an unconnected state caused by an RRC release message; and receiving, by the DU from the CU, an identity of first CG-SDT resource configuration information, such that the CG-SDT resource configuration information is reconfigured for the UE based on the first CG-SDT resource configuration information after the RA-SDT.

[0021] In some embodiments of the present application, the method may include transmitting, by the DU to the CU, second CG-SDT resource configuration information to replace the first CG-SDT resource configuration information, and receiving, by the DU from the CU, another RRC release message for the UE together with the second CG-SDT resource configuration information. The method may further include transmitting, by the DU to the UE, a network indication indicating the release of the first CG-SDT resource configuration information. The network indication indicates the release of the first CG-SDT resource configuration information by including the second CG-SDT resource configuration information as complete CG-SDT resource configuration information in the another RRC release message.

[0022] In some embodiments of the present application, the method may include receiving, by the DU from the CU, radio link measurement information for CG-SDT resource selection.

[0023] In some embodiments of the present application, the method may include transmitting the TAT-SDT by the DU to the CU, and, if the TAT-SDT was initiated in response to the UE releasing to a disconnected state, transmitting a remaining value of the TAT-SDT by the DU to the CU.

[0024] In some embodiments of the present application, the method may include transmitting the TAT-SDT by the DU to the CU, and initiating the TAT-SDT by the DU in response to configuring the TAT-SDT or sending an RRC release message to the UE.

[0025] In some embodiments of the present application, the method may include a step of releasing, by the DU, a logical F1 connection and an associated UE context associated with the UE in response to expiration of the TAT-SDT.

[0026] In some embodiments of the present application, the method may include a step of sending a UE context release request message by the DU to the CU to request the CU to release a logical F1 connection associated with the UE, wherein the UE context release request message includes a cause value indicating that the UE context release request message is caused by the expiration of the TAT-SDT.

[0027] According to some embodiments of the present application, a method for SDT includes receiving, by a UE, an RRC release message from a network side together with first CG-SDT resource configuration information; entering a disconnected state in response to receiving the RRC release message; and releasing, by the UE, the first CG-SDT resource configuration information in response to one of receiving another RRC release message, falling back from CG-SDT to RA-SDT or non-SDT, receiving a network indication indicating release of the first CG-SDT resource configuration information, and expiration of a TAT-SDT associated with the first CG-SDT resource configuration information.

[0028] In some embodiments of the present application, the method may include, in response to receiving an RRC release message, releasing the first CG-SDT resource configuration information and applying the second CG-SDT resource configuration information, if any.

[0029] In some embodiments of the present application, the network indication indicates the release of the first CG-SDT resource configuration information by including the complete CG-SDT resource configuration information in another RRC release message.

[0030] In some embodiments of the present application, the method may include, in response to receiving another configuration of the TAT-SDT, stopping the TAT-SDT and starting another TAT-SDT as indicated by the another configuration of the TAT-SDT, or restarting the TAT-SDT as indicated by the another configuration of the TAT-SDT, or continuing to run the TAT-SDT if the TAT-SDT is in progress.

[0031] Some embodiments of the present application provide a CU of a RAN node, including a processor and a transceiver coupled to the processor, wherein the processor is configured to: send an instruction associated with an SDT scheme selection for the UE from the CU to a DU; if CG-SDT is configured, receive first CG-SDT resource configuration information for the UE from the DU by the CU; and send an RRC release message by the CU to the DU, together with the first CG-SDT resource configuration information, to transition the UE to an unconnected state.

[0032] Some embodiments of the present application provide a DU of a RAN node, including a processor and a transceiver coupled to the processor, wherein the processor is configured to: receive, by the DU from a CU, an indication associated with an SDT scheme selection for the UE; if CG-SDT is configured, send, by the DU to the CU, first CG-SDT resource configuration information for the UE; and receive, by the DU from the CU, an RRC release message together with the first CG-SDT resource configuration information to transition the UE to an unconnected state.

[0033] Some embodiments of the present application provide a UE including a processor and a transceiver coupled to the processor, wherein the processor is configured to receive an RRC release message by the UE from a network side together with first CG-SDT resource configuration information, enter a disconnected state in response to receiving the RRC release message, and release the first CG-SDT resource configuration information in response to one of receiving another RRC release message, falling back to RA-SDT or non-SDT, receiving a network indication indicating release of the first CG-SDT resource configuration information, and expiration of a TAT-SDT associated with the first CG-SDT resource configuration information.

[0034] The embodiments of the present application provide a method and apparatus for small data transmission that can solve problems related to CG-SDT, such as how to configure, reconfigure, and release CG-SDT resource configuration information over the F1 interface. Thus, the present application can facilitate and improve the implementation of NR.

[0035] To describe how the advantages and features of the present application may be obtained, the present application will be described by reference to specific embodiments that are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present application and therefore should not be considered limiting of its scope. [Brief explanation of the drawings]

[0036] [Figure 1] FIG. 1 illustrates a wireless communication system in accordance with some embodiments of the present application. [Figure 2] FIG. 1 is a schematic diagram of the internal structure of a RAN node according to some embodiments of the present application. [Figure 3] 1 is a flowchart illustrating exemplary steps of a method for small data transmission according to some embodiments of the present application. [Figure 4] 10 is a flowchart illustrating exemplary steps of a method for small data transmission according to some other embodiments of the present application. [Figure 5]10 is a flowchart illustrating exemplary steps of a method for small data transmission according to some further embodiments of the present application. [Figure 6] 10 is a flowchart illustrating exemplary steps of a method for small data transmission according to some further embodiments of the present application. [Figure 7] 10 is a flowchart illustrating exemplary steps of a method for small data transmission according to some further embodiments of the present application. [Figure 8] 1 is a block diagram of an apparatus for small data transmission according to some embodiments of the present application. [Figure 9] FIG. 10 is a block diagram of an apparatus for small data transmission according to some other embodiments of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0037] The detailed description of the accompanying drawings is intended as an illustration of a preferred embodiment of the present application and is not intended to represent the only form in which the present application may be practiced. It is to be understood that the same or equivalent function may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present application.

[0038] Reference will now be made in detail to several embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as 3GPP 5G and 3GPP long term evolution (LTE). With the development of network architectures and new service scenarios, it is contemplated that all embodiments of the present application are also applicable to similar technical problems. Furthermore, the terms used in the present application may be changed without affecting the principles of the present application.

[0039] FIG. 1 illustrates a schematic diagram of an exemplary wireless communication system 100 in accordance with some embodiments of the present application.

[0040] 1, wireless communication system 100 includes at least one BS 101 and at least one UE 102. Specifically, wireless communication system 100 includes, for illustrative purposes, one BS 101 and two terminal devices 102 (e.g., UE 102a and UE 102b). For simplicity, although a particular number of BSs and terminal devices are shown in FIG. 1, it is contemplated that wireless communication system 100 may include more or fewer BSs and terminal devices in certain other embodiments of the present application.

[0041] The wireless communication system 100 may be compatible with any type of network capable of transmitting 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] The BS 101 may communicate with a core network (CN) node (not shown), such as a mobility management entity (MME) or serving gateway (S-GW), a mobility management function (AMF), or a user plane function (UPF), via an interface. A BS may also be referred to as an access point, access terminal, base, macrocell, Node B, enhanced node B (eNB), gNB, Home Node B, relay node, or device, or may be described using other terms used in the art. In 5G NR, a BS may also be referred to as a radio access network (RAN) node. Each BS may serve several UEs, e.g., cells or cell sectors, within its serving area via wireless communication links. Neighboring BSs may communicate with each other as needed, for example, during a handover procedure for a UE.

[0043] The terminal devices 102, e.g., UE 102a and UE 102b, may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), in-vehicle computers, network devices (e.g., routers, switches, and modems). According to embodiments of the present application, the terminal devices may include portable wireless communication devices, smartphones, cellular telephones, flip phones, devices with subscriber identity modules, personal computers, selective call receivers, or any other devices capable of transmitting and receiving communication signals over a wireless network. In some embodiments, the terminal devices may include wearable devices such as smart watches, fitness bands, optical head-mounted displays, etc. Terminal devices may also be referred to as subscriber units, mobiles, mobile stations, users, terminals, mobile terminals, wireless terminals, fixed terminals, subscriber stations, user terminals, or devices, or may be described using other terms used in the art. In this specification (and throughout the specification), "UE" is used illustratively as a typical terminal device to illustrate a terminal device, but should be understood as any type of terminal device.

[0044] FIG. 2 is a schematic diagram illustrating the internal structure of a RAN node, e.g., a BS, according to some embodiments of the present application.

[0045] 2, in a CU-DU separation based RAN architecture, the internal structure of a RAN node (e.g., BS 101) may be separated into a CU 200 and at least one DU 202 (e.g., two DUs shown in FIG. 2). Although a specific number of DUs 202 are shown in FIG. 2, it is contemplated that any number of DUs 202 may be included in a BS.

[0046] The CU 200 and the DU 202 are connected to each other by an interface called F1 as specified in the 3GPP standard documents. The RRC layer functionality, the service data adaptation protocol (SDAP) functionality, and the packet data convergence protocol (PDCP) layer functionality are located in the CU 200. The radio link control (RLC) layer functionality, the medium access control (MAC) layer functionality, and the physical (PHY) layer functionality are located in the DU 202.

[0047] In LTE, when a terminal device 102, e.g., a UE, in an unconnected state wants to transmit data, the terminal device 102 may trigger an early data transmission (EDT) procedure. The EDT procedure may include an EDT procedure for control plane (CP) cellular internet of things (CIoT) evolved packet system (EPS) optimization and an EDT procedure for user plane (UP) CIoT EPS optimization. In the EDT procedure for CP CIoT EPS optimization, data may be transmitted through an RRC early data request message. In the EDT procedure for UP CIoT EPS optimization, data may be transmitted through an RRC connection resume request message.

[0048] The EDT procedure evolves into the SDT procedure in NR. According to the NR Rel-17 work item, there are two SDT methods (i.e., SDT types) for UEs in the RRC_INACTIVE state: RA-SDT and CG-SDT. In RAN2#113e, it was agreed that the UE can fall back from CG-SDT to RA-SDT. For example, the high-level procedure for selection between SDT and non-SDT in response only to the arrival of data on DRBs and / or signaling radio bearers (SRBs) for which SDT is enabled is as follows: If the criteria for CG-SDT are met, the UE selects CG-SDT and initiates the CG-SDT procedure. Otherwise, if the criteria for RA-SDT are met, the UE selects RA-SDT and initiates the RA-SDT procedure. Otherwise, the UE initiates the non-SDT procedure.

[0049] However, there is little agreement on CG-SDT. For example, regarding CG-SDT configuration for the UE, RAN2 agreed that CG-SDT resource configuration information is provided in the RRC release message, but there is no agreement on whether or how the CU or DU in a CU-DU split-based RAN architecture determines which SDT scheme should be configured during the RRC release procedure.

[0050] In another example, in the case of CG-SDT, the DU needs to store the UE context, including, for example, CG-SDT resource configuration information, and maintain the logical F1 connection associated with the UE in the RRC_INACTIVE state. During the SDT procedure, if the UE falls back from the CG-SDT procedure to the RA-SDT procedure or a non-SDT procedure, a new logical F1 connection associated with the UE during the RA-SDT procedure or a non-SDT procedure is set up for the UE. When the SDT procedure ends, the network side may decide to reconfigure or release the CG-SDT resource configuration information for the UE. However, because the new (relative to the previous connection) logical F1 connection associated with the UE was set up while the previous CG-SDT resource configuration information was linked to the previous logical F1 connection associated with the UE, the DU has no knowledge of the previous CG-SDT resource configuration information. Therefore, when the UE falls back from CG-SDT to the RA-SDT or a non-SDT, it is necessary to address how the CU and DU reconfigure or release the previous CG-SDT resource configuration information in the new logical F1 connection associated with the UE.

[0051] In yet another example, it has been agreed that the UE releases the CG-SDT resource configuration information when the associated TAT-SDT expires in RRC_INACTIVE state. The DU may also release the CG-SDT resource configuration information upon TAT-SDT expiration. In this case, it is also necessary to resolve how to release the UE context, the logical F1 connection associated with the UE, and the user plane resources between the CU and the DU. The TAT-SDT is an SDT-specific time alignment timer used to control how long the UE considers itself uplink time aligned for the CG-SDT resources.

[0052] In view of the above, the embodiments of the present application provide technical solutions for small data transmission, especially for CG-SDT, such as how to configure CG-SDT resource configuration information, how to reconfigure CG-SDT resource configuration information, and how to release CG-SDT resource configuration information.

[0053] 3 is a flowchart showing an example procedure of a method for small data transmission according to some embodiments of the present application. Although the method is illustrated at a system level by a UE on the remote side (i.e., the UE side) and a CU and DU of a RAN node on the network side (i.e., the BS side), those skilled in the art will understand that the method implemented on the remote side and the method implemented on the network side may be separately implemented by other devices with similar functions and integrated together. In some embodiments of the present application, the CU may be referred to as a gNB-CU, and the DU may be referred to as a gNB-DU. The same applies hereinafter.

[0054] As shown in FIG. 3 , according to some embodiments of the present application, for a UE to enter a disconnected state, the CU determines (or selects) which SDT scheme, for example, whether CG-SDT is configured for the UE or whether RA-SDT is configured for the UE, in step 300. Herein (throughout the specification), the disconnected state may be an inactive mode, for example, an RRC_INACTIVE state or an RRC_IDLE state. The CU sends an indication associated with the SDT scheme selection to the DU in step 302. If the CU determines that CG-SDT is configured for the UE, the indication associated with the SDT scheme selection is a CG-SDT request indication, which indicates to the DU that CG-SDT is required to be configured for the UE, or a CG-SDT query indication, which indicates to the DU that CG-SDT is required to be configured for the UE. For example, the CU sends the CG-SDT request indication or the CG-SDT query indication to the DU in a UE context modification request message. In some embodiments of the present application, a CG-SDT request instruction or a CG-SDT inquiry instruction is associated with a DRB, ie, is per DRB.

[0055] Therefore, the DU receives an instruction associated with the SDT scheme selection for the UE, for example, a CG-SDT request instruction or a CG-SDT query instruction, in the UE context modification request message. If the DU approves the CG-SDT, i.e., if the CG-SDT is configured by the DU, the DU provides CG-SDT resource configuration information, for example, first CG-SDT resource configuration information, to the CU in step 304, for example, in the UE context modification response message.

[0056] After receiving the first CG-SDT resource configuration information, the CU sends an RRC release message to the DU together with the first CG-SDT resource configuration information in step 306 to transition the UE to an unconnected state, for example, an RRC_INACTIVE state. For example, the RRC release message may be sent by the CU to the DU together with the first CG-SDT resource configuration information in a UE context release message, for example, a UE Context Release Command. In some embodiments of the present application, the CU may also store the received CG-SDT resource configuration information in step 308 for reconfiguration or other use, which may be performed after forwarding the RRC release message to the DU, or may be performed before or simultaneously with forwarding the RRC release message to the DU. In step 310, the DU forwards an RRC release message to the UE together with the first CG-SDT resource configuration information to transition the UE to an unconnected state. In some embodiments of the present application, in response to receiving a UE context release message from the CU, the DU may also store CG-SDT resource configuration information of the UE, e.g., first CG-SDT resource configuration information and a C-RNTI associated with the UE, for successive CG-SDTs, in step 312, which may be performed after forwarding an RRC release message to the UE, or may be performed before or simultaneously with forwarding the RRC release message to the UE. In some embodiments of the present application, in response to the UE context release message, the DU may also send a UE context release complete message to the CU in step 314 after forwarding the RRC release message to the UE.

[0057] In some other embodiments of the present application, the DU, rather than the CU, determines (or selects) which SDT scheme, for example CG-SDT or RA-SDT, will be configured for the UE.

[0058] 4 is a flowchart illustrating an exemplary procedure of a method for small data transmission according to some other embodiments of the present application. Similarly, although the present method is illustrated at a system level by a UE on the remote side (i.e., UE side) and a CU and DU of a RAN node on the network side (i.e., BS side), those skilled in the art will understand that the method implemented on the remote side and the method implemented on the network side may be separately implemented and integrated by other devices with similar functions.

[0059] 4, according to some embodiments of the present application, the CU sends an indication associated with SDT scheme selection to a DU, for example, a gNB-DU, in step 400. The indication associated with the SDT scheme selection is an SDT indication that indicates to the DU whether a DRB or a QoS flow or a PDU is subject to SDT. For example, during a DRB setup procedure, the CU may indicate to the DU whether a DRB or a QoS flow or a PDU session is subject to SDT by explicit indication or by implicit QoS parameters, for example, in a UE context modification request message.

[0060] Thus, the DU receives an indication associated with the SDT scheme selection for the UE. Based on the indication associated with the SDT scheme selection for the UE, the DU determines whether CG-SDT is configured for the UE in step 402. If the DU determines that CG-SDT is configured, the DU provides CG-SDT resource configuration information, for example, first CG-SDT resource configuration information, to the CU in a UE context modification response message in step 404.

[0061] After receiving the first CG-SDT resource configuration information, the CU sends an RRC release message to the DU together with the first CG-SDT resource configuration information in step 406 to transition the UE to an unconnected state, e.g., an RRC_INACTIVE state. For example, the RRC release message together with the first CG-SDT resource configuration information may be sent by the CU to the DU in a UE context release message, e.g., a UE Context Release Command. In some embodiments of the present application, the CU may also store the received CG-SDT resource configuration information in step 408 for reconfiguration or other use, which may be performed after forwarding the RRC release message to the DU, or may be performed before or simultaneously with forwarding the RRC release message to the DU. The DU forwards an RRC release message to the UE together with the first CG-SDT resource configuration information in step 410 to transition the UE to an unconnected state. In some embodiments of the present application, in response to receiving a UE context release message from the CU, the DU may also store the first CG-SDT resource configuration information and the C-RNTI associated with the UE for consecutive CG-SDT in step 412, which may be performed after forwarding an RRC release message to the UE, or may be performed before or simultaneously with forwarding the RRC release message to the UE. In response to the UE context release message, the DU may also send a UE context release complete message to the CU in step 414 after forwarding the RRC release message to the UE.

[0062] In some embodiments of the present application, the CG-SDT resource configuration information is pre-configured in the DU, and the DU applies the pre-configured CG-SDT resource configuration information when releasing the UE to an unconnected state, for example, an RRC_INACTIVE state, in step 410.

[0063] According to some embodiments of the present application, while the UE is in an unconnected state, e.g., an RRC_INACTIVE state, data may be generated in the UE and transmitted to the network side. Therefore, the UE triggers an SDT procedure to transmit the generated data, which may be RA-SDT or CG-SDT. In some other embodiments of the present application, a non-SDT procedure may be triggered to transmit the generated data.

[0064] The UE may perform the SDT scheme selection procedure as follows: If the CG-SDT criteria are met, the UE selects CG-SDT and initiates the CG-SDT procedure. Otherwise, if the RA-SDT criteria are met, the UE selects RA-SDT and initiates the RA-SDT procedure. If the RA-SDT criteria are also not met, the UE initiates a non-SDT procedure. The CG-SDT criteria are considered met if all of the following conditions are met: 1) the amount of available data is less than or equal to the data amount threshold. 2) the reference signal received power (RSRP) is greater than or equal to the configured threshold. 3) CG-SDT resources are configured and valid on the selected UL carrier. The RA-SDT criteria are also considered met if all of the following conditions are met: 1) the amount of available data is less than or equal to the data amount threshold. 2) the RSRP is greater than or equal to the configured threshold. 3) 4-step RA-SDT resources are configured on the selected UL carrier and the criteria for selecting 4-step RA-SDT are met, or 2-step RA-SDT resources are configured on the selected UL carrier and the criteria for selecting 2-step RA-SDT are met.

[0065] Therefore, for a UE with a CG-SDT configuration, if the CG-SDT criteria are not met, the UE may fall back from CG-SDT to RA-SDT or non-SDT according to the SDT scheme selection procedure.

[0066] As described above, in some embodiments of the present application, the CU stores CG-SDT resource configuration information. When the UE falls back from CG-SDT to RA-SDT or non-SDT, the CU sends the stored CG-SDT resource configuration information to the DU for reconfiguration of the CG-SDT resource configuration information.

[0067] 5 is a flowchart illustrating an exemplary procedure of a method for small data transmission according to some further embodiments of the present application. Although the method is illustrated at a system level by a UE on a remote side (i.e., a UE side) and a RAN node on a network side (i.e., a BS side), such as a CU and DU of a BS, those skilled in the art will understand that the method implemented on the remote side and the method implemented on the network side may be separately implemented by other devices with similar functions and integrated together.

[0068] As shown in FIG. 5, in step 500, a CU, for example, a gNB-CU, stores CG-SDT resource configuration information, for example, first CG-SDT resource configuration information for a UE in step 500 that is to be sent to an unconnected state, such as an RRC_INACTIVE state. The first CG-SDT resource configuration information may be provided according to the embodiment shown in FIG. 3 or FIG. 4 or in another manner, and therefore will not be repeated. In step 501, the CU sends an RRC release message to the DU together with the first CG-SDT resource configuration information to transition the UE to the unconnected state. Then, in step 502, the DU forwards an RRC release message to the UE together with the first CG-SDT resource configuration information to send the UE to the unconnected state. The UE receives the first CG-SDT resource configuration information forwarded by the DU together with the RRC release message, and then enters the unconnected state in response to the RRC release message.

[0069] If a disconnected UE has data to transmit but the CG-SDT criteria are not met, the UE may fall back to RA-SDT in step 503. In step 504, the UE triggers the RA-SDT procedure and sends an RRC Resume Request message to the DU along with the data to be transmitted. After transmitting the data and the RRC Resume Request message, the DU sends an RA-SDT indication indicating that RA-SDT is to be performed by the UE to the CU in step 506, for example, in an INITIAL UL RRC MESSAGE TRANSFER message not associated with the UE. In some embodiments of the present application, the RA-SDT indication may be a cause value so that the CU knows that the RRC Resume Request message was caused by RA-SDT and the UE falls back to RA-SDT from CG-SDT. In step 508, the CU allocates a CU UE F1AP ID and sends a UE Context Setup Request message including a UE context for RA-SDT to the DU. Therefore, during the RA-SDT procedure, a new C-RNTI (relative to the previous one) is allocated by the DU, and a new UE context and a logical F1 connection associated with the UE are established between the CU and the DU. If the CU identifies that a new logical F1 connection associated with the UE is set up, for example according to the UE identity (e.g., I-RNTI) in the RRC Resume Request message, the CU triggers a UE context release procedure to release the previous (i.e., old) logical F1 connection associated with the UE in step 510. The DU releases the stored previous UE context including the previous CG-SDT resource configuration information, for example, the first CG-SDT resource configuration information.

[0070] The CU may determine that the UE may be sent to a disconnected state again after the RA-SDT procedure. In some embodiments of the present application, the CU may determine that CG-SDT is configured for the UE, as shown in FIG. 3. In some other embodiments of the present application, whether CG-SDT is configured for the UE may be determined by the DU, as shown in FIG. 4, and the CU indicates to the DU, by explicit instruction or implicit QoS parameters, whether the DRB, QoS flow, or PDU session is subject to SDT. In step 512, the CU transmits the stored (old) CG-SDT resource configuration information, for example, the first CG-SDT resource configuration information, to the DU so that the CG-SDT resource configuration information is reconfigured for the UE based on the first CG-SDT resource configuration information after the RA-SDT. The first CG-SDT resource configuration information may be an RRC container included in an RRC container IE from the CU to the DU. In some other embodiments of the present application, the first CG-SDT resource configuration information may be included in a UE context modification request message. The CU may also provide radio link measurement information, eg, RSRP, to the DU so that the DU selects CG-SDT resources based on the radio link measurement information.

[0071] After receiving the stored (previous or old) CG-SDT resource configuration information, the DU decides whether to update (or reconfigure) the CG-SDT resource configuration information. In step 514, if the DU decides to reconfigure the CG-SDT resource configuration information, the DU generates new CG-SDT resource configuration information, for example, second CG-SDT resource configuration information, based on the previous CG-SDT resource configuration information. The new CG-SDT resource configuration information may be a delta configuration information of the previous CG-SDT resource configuration information or the complete CG-SDT resource configuration information. In step 516, the DU transmits the new CG-SDT resource configuration information to the CU. For example, the new CG-SDT resource configuration information may be an RRC container included in an RRC container IE from the DU to the CU. In another example, the new CG-SDT resource configuration information may be included in a UE context modification response message.

[0072] After receiving the new CG-SDT resource configuration information, e.g., the second CG-SDT resource configuration information, the CU sends an RRC release message to the DU together with the second CG-SDT resource configuration information in step 518 to transition the UE to an unconnected state, e.g., the RRC_INACTIVE state. The DU forwards the RRC release message to the UE together with the second CG-SDT resource configuration information in step 520. Similarly, the CU also stores the second CG-SDT resource configuration information in step 522 to further support reconfiguration of the CG-SDT resource configuration information. The old CG-SDT resource configuration information is replaced with the new CG-SDT resource configuration information in the CU, e.g., the first CG-SDT resource configuration information is replaced with the second CG-SDT resource configuration information. The RRC release message, together with the second CG-SDT resource configuration information, can be sent by the CU to the DU in a UE context release message, e.g., a UE Context Release Command. In some embodiments of the present application, in response to receiving a UE context release message from the CU, the DU may also store the second CG-SDT resource configuration information of the UE and the C-RNTI associated with the UE for consecutive CG-SDT in step 524. In response to the UE context release message, the DU may also send an RRC release message to the UE and then send a UE context release complete message to the CU in step 526.

[0073] In some embodiments of the present application, the CU does not store CG-SDT resource configuration information. Alternatively, even if the CU stores CG-SDT resource configuration information, the CU does not transmit the stored CG-SDT resource configuration information to the DU for reconfiguration. When the UE falls back from CG-SDT to RA-SDT or non-SDT, the CU sends the old (i.e., previous) CG-SDT resource configuration information, for example, the ID of the first CG-SDT resource configuration information, so that the DU can retrieve the old CG-SDT resource configuration information to reconfigure the CG-SDT resource configuration information for the UE.

[0074] 6 is a flowchart illustrating an exemplary procedure of a method for small data transmission according to some further embodiments of the present application. Although the method is illustrated at a system level by a UE and a CU and DU of a RAN node on the remote side (i.e., UE side), and a BS on the network side (i.e., BS side), those skilled in the art will understand that the method implemented on the remote side and the method implemented on the network side may be separately implemented and integrated by other devices with similar functions.

[0075] As shown in FIG. 6, if a UE in a disconnected state, e.g., an RRC_INACTIVE state, has data to transmit and the CG-SDT criteria are not met, the UE may fall back to RA-SDT in step 600. In step 602, the UE triggers the RA-SDT procedure and sends an RRC resume message to the DU along with the data to transmit. After receiving the data and the RRC resume request message, the DU sends an RA-SDT indication to the CU in step 604, indicating that RA-SDT is to be implemented by the UE, for example, in an INITIAL UL RRC MESSAGE TRANSFER message not associated with the UE. In some embodiments of the present application, the RA-SDT indication may be a cause value so that the CU knows that the RRC resume request message was caused by RA-SDT and the UE falls back to RA-SDT from CG-SDT. In step 606, the CU allocates a CU UE F1AP ID and sends a UE context setup request message including a UE context for RA-SDT to the DU. Therefore, during the RA-SDT procedure, a new C-RNTI is allocated by the DU, and a new UE context and a logical F1 connection associated with the UE are established between the CU and the DU. If the CU identifies that a new logical F1 connection associated with the UE is set up, for example, according to the UE identity (e.g., I-RNTI) in the RRC Resume Request message, the CU triggers a UE context release procedure to release the previous (i.e., old) logical F1 connection associated with the UE in step 608. The DU releases the stored previous UE context including the previous CG-SDT resource configuration information, for example, the first CG-SDT resource configuration information.

[0076] The CU may determine that the UE may be sent to a disconnected state again after the RA-SDT procedure. In some embodiments of the present application, the CU may determine that CG-SDT is configured for the UE, as shown in FIG. 3. In some other embodiments of the present application, whether CG-SDT is configured for the UE may be determined by the DU, as shown in FIG. 4, and the CU indicates to the DU, by explicit instruction or by implicit QoS parameters, whether the DRB, QoS flow, or PDU session is subject to SDT. In step 610, the CU sends old CG-SDT resource configuration information, for example, the ID of the first CG-SDT resource configuration information, to the DU, so that the CG-SDT resource configuration information is configured for the UE based on the first CG-SDT resource configuration information after RA-SDT. The ID of the old CG-SDT resource configuration information may be the old C-RNTI associated with the UE or the old DU UE F1AP ID, and is used to uniquely identify the old F1 connection associated with the UE for the UE in the DU. The stored ID of the old CG-SDT resource configuration information may be included in the UE CONTEXT MODIFICATION REQUEST message. The CU may also provide radio link measurement information, e.g., RSRP, to the DU so that the DU selects CG-SDT resources based on the radio link measurement information.

[0077] After receiving the old CG-SDT resource configuration information, e.g., the ID of the first CG-SDT resource configuration information, the DU retrieves the old RRC CG-SDT resource configuration information and determines whether to update (or reconfigure) the CG-SDT resource configuration information. In step 612, if the DU determines to reconfigure the CG-SDT resource configuration information, the DU generates new CG-SDT resource configuration information, e.g., second CG-SDT resource configuration information, based on the previous CG-SDT resource configuration information. The new CG-SDT resource configuration information may be a delta configuration information of the previous CG-SDT resource configuration information or a complete CG-SDT resource configuration. In step 614, the DU transmits the new CG-SDT resource configuration information to the CU. For example, the new CG-SDT resource configuration information may be an RRC container included in an RRC container IE from the DU to the CU. In another example, the new CG-SDT resource configuration information may be included in a UE context modification response message.

[0078] After receiving new CG-SDT resource configuration information, e.g., second CG-SDT resource configuration information, the CU sends an RRC release message to the DU together with the second CG-SDT resource configuration information in step 616 to transition the UE to an unconnected state, e.g., RRC_INACTIVE state. For example, the RRC release message may be sent in a UE context release message together with the second CG-SDT resource configuration information. The DU forwards the RRC release message together with the second CG-SDT resource configuration information to the UE in step 618. Similarly, in some embodiments of the present application, in step 620, the DU may also store the second CG-SDT resource configuration information and a C-RNTI associated with the UE for successive CG-SDTs in response to receiving the UE context release message from the CU. The DU may also send a UE context release complete message to the CU in step 622 after forwarding the RRC release message to the UE in response to the UE context release message.

[0079] The embodiments of the present application also provide technical solutions for how to release UE contexts and logical F1 connections associated with the UE, such as CG-SDT resource configuration information.

[0080] According to some embodiments of the present application, a DU, e.g., a gNB-DU, sends a TAT-SDT to a CU, e.g., a gNB-CU. The TAT-SDT is a time alignment timer used to control how long the UE considers itself uplink time aligned for CG-SDT resources. When the TAT-SDT expires, both the DU and the CU locally release the stored F1 connection and related CG-SDT resource configuration information associated with the TAT-SDT. That is, the release of the CG-SDT configuration in the CU, DU, and UE is separate.

[0081] 7 is a flowchart illustrating an exemplary procedure of a method for small data transmission according to some further embodiments of the present application. Although the method is illustrated at a system level by a UE and a CU and DU of a RAN node on the remote side (i.e., UE side), and a BS on the network side (i.e., BS side), those skilled in the art will understand that the method implemented on the remote side and the method implemented on the network side may be separately implemented and integrated by other devices with similar functions.

[0082] As shown in FIG. 7, in step 700, the DU may transmit a TAT-SDT, e.g., a first TAT-SDT, to the CU. In some embodiments of the present application, the TAT-SDT may be included in CG-SDT resource configuration information, e.g., the first CG-SDT resource configuration information. For example, when the DU generates CG-SDT resource configuration information, e.g., the first CG-SDT resource configuration information including the TAT-SDT, the DU sends the TAT-SDT to the CU in an F1AP message, e.g., a UE context modification response message. If the TAT-SDT is started when releasing the UE to an unconnected state, e.g., an RRC_INACTIVE state, the DU may send the remaining value of the TAT-SDT to the CU. In some embodiments of the present application, the TAT-SDT is included in the F1AP message but outside the CG-SDT resource configuration information.

[0083] In step 702, the DU initiates the TAT-SDT in response to sending a TAT-SDT configuration or RRC release message to the UE.

[0084] In step 704, the CU starts the TAT-SDT in response to triggering a UE context release procedure, such as sending the UE to the RRC_INACTIVE state, in response to receiving a TAD-SDT, or in response to sending an RRC release message to the UE. The CU stops the TAT-SDT in response to receiving small data or an RRC resume request message.

[0085] When the TAT-SDT expires, the DU and CU locally release the logical F1 connection associated with the UE and the associated UE context, e.g., CG-SDT resource configuration information. For example, when the TA-SDT expires in the DU, the DU releases the logical F1 connection associated with the UE and the associated UE context in step 706. When the TA-SDT expires in the CU, the CU releases the logical F1 connection associated with the UE and the associated UE context in step 708.

[0086] If the UE receives a new configuration of the TAT-SDT in the RRC release message in step 710, the UE stops the ongoing TAT-SDT, e.g., the first TAT-SDT, and starts a new TAT-SDT, e.g., the second TAT-SDT, indicated in the new configuration of the TAT-SDT. In some other embodiments of the present application, the UE may resume the TAT-SDT indicated in the new configuration of the TAT-SDT. In some still other embodiments of the present application, the UE may continue to run the ongoing TAT-SDT, if one is running. When the TAT-SDT expires according to the value indicated in the TAT-SDT configuration, the UE releases the CG-SDT resource configuration information, e.g., the first CG-SDT resource configuration information, in step 712.

[0087] According to some other embodiments of the present application, the DU requests the CU to release the UE context and the logical F1 connection associated with the UE in response to the expiration of the TAT-SDT. That is, the release of the first CG-SDT resource configuration information is not local to the DU and the CU. For example, the DU may initiate a TAT-SDT, e.g., the first TAT-SDT, in response to the configuration of the TAT-SDT or when sending an RRC release message to the UE. When the TAT-SDT expires in the DU, the DU triggers a UE context release request procedure to request the CU to release the logical F1 connection associated with the UE. For example, the DU sends a UE context release request message to the CU, and the UE context release request message includes a cause value, e.g., "TAT-SDT expired," to indicate to the CU that the RRC release request is caused by the TAT-SDT expiration. The CU then releases the logical F1 connection associated with the UE.

[0088] There are several ways for the UE to release CG-SDT resource configuration information other than the expiration of the TAT-SDT associated with the CG-SDT resource configuration information as shown above. For example, the UE can receive an RRC release message from the network side, e.g., a gNB-DU, along with CG-SDT resource configuration information, e.g., first CG-SDT resource configuration information, and then enter a disconnected state in response to receiving the RRC release message. The UE releases the first CG-SDT resource configuration information in response to receiving another RRC release message, i.e., a new (i.e., next) RRC release message. In some other embodiments of the present application, the UE releases the first CG-SDT resource configuration information in response to a fallback from CG-SDT to RA-SDT or non-SDT. In some other embodiments of the present application, the UE releases the first CG-SDT resource configuration information in response to receiving a network indication indicating the release of the first CG-SDT resource configuration information. The network indication may indicate the release of the first CG-SDT resource configuration information by including the complete CG-SDT resource configuration information in a new RRC release message. According to some embodiments of the present application, in response to receiving the RRC release message, the UE releases the previous CG-SDT resource configuration information and applies the new CG-SDT resource configuration information, if any. For example, the UE releases the first CG-SDT resource configuration information and applies the second CG-SDT resource configuration information.

[0089] It should be understood by those skilled in the art that the technical solutions for configuring, reconfiguring, and releasing CG-SDT resource configuration information disclosed in this application may be implemented separately or integrated with each other. For example, the configuration embodiment shown in Figure 3 may be integrated with the reconfiguration embodiment shown in Figure 5 or Figure 6, and / or with the release embodiment shown in Figure 7 or other release embodiments disclosed in this application. The configuration embodiment shown in Figure 4 may be integrated with the reconfiguration embodiment shown in Figure 5 or Figure 6, and / or with the release embodiment shown in Figure 7 or other release embodiments disclosed in this application.

[0090] Additionally, while the steps are shown in order, those skilled in the art will understand that this is merely for the sake of clarity. The order of description or step numbering should not be considered a limitation on the order between steps, unless the performance of a step is dependent on a previous step. Terms such as "first," "second," "new," and "old" are merely used to distinguish between steps for the sake of clarity and should not be considered a limitation.

[0091] Besides the method, the embodiments of the present application also propose an apparatus for small data transmission. For example, Figure 8 shows a block diagram of an apparatus 800 for small data transmission according to some embodiments of the present application.

[0092] 8, the apparatus 800 may include at least one non-transitory computer-readable medium 801, at least one receiving circuit 802, at least one transmitting circuit 804, and at least one processor 806 coupled to the non-transitory computer-readable medium 801, the receiving circuit 802, and the transmitting circuit 804. The apparatus 800 may be a terminal device (e.g., a UE) configured to perform methods such as those presented above.

[0093] In this figure, elements such as at least one processor 806, transmit circuitry 804, and receive circuitry 802 are described in the singular, but the plural is contemplated unless limitation to the singular is expressly stated. In some embodiments of the present application, the receive circuitry 802 and the transmit circuitry 804 may be combined into a single device, such as a transceiver. In some embodiments of the present application, the apparatus 800 may further include an input device, a memory, and / or other components.

[0094] In some embodiments of the present application, the non-transitory computer-readable medium 801 may store computer-executable instructions for causing a processor to perform a method relating to a terminal device as described above. For example, the computer-executable instructions, when executed, cause the processor 806 to interact with the receiving circuitry 802 and the transmitting circuitry 804 to perform steps relating to a UE as shown above.

[0095] In some embodiments of the present application, the non-transitory computer-readable medium 801 may store computer-executable instructions for causing a processor to perform a method related to a CU or DU as described above. For example, the computer-executable instructions, when executed, cause the processor 806 to interact with the receiving circuit 802 and the transmitting circuit 804 to perform steps related to a CU or DU as shown above.

[0096] FIG. 9 is a block diagram of an apparatus for small data transmission according to some other embodiments of the present application.

[0097] 9, an apparatus 900, such as a UE, a RAN node, a CU or DU of a RAN node, may include at least one processor 902 and at least one transceiver 904. The transceiver 904 may include at least one separate receiving circuit 906 and transmitting circuit 908 or at least one integrated receiving circuit 906 and transmitting circuit 908.

[0098] According to some embodiments of the present application, when the apparatus 900 is a UE, the processor is configured to receive, by the UE, an RRC release message from the network side along with CG-SDT resource configuration information, e.g., first CG-SDT resource configuration information; enter a disconnected state in response to receiving the RRC release message; and release the first CG-SDT resource configuration information in response to one of receiving another RRC release message, falling back to RA-SDT or non-SDT, receiving a network indication indicating release of the first CG-SDT resource configuration information, and expiration of a TAT-SDT associated with the first CG-SDT resource configuration information.

[0099] According to some other embodiments of the present application, when the apparatus 900 is a CU of a RAN node, the processor may be configured to send an indication associated with an SDT scheme selection for the UE from the CU to the DU, and if CG-SDT is configured, receive CG-SDT resource configuration information, e.g., first CG-SDT resource configuration information for the UE, by the CU from the DU, and send an RRC release message by the CU to the DU together with the first CG-SDT resource configuration information to transition the UE to an unconnected state.

[0100] According to some still other embodiments of the present application, when the apparatus 900 is a DU of a RAN node, the processor may be configured to: receive, by the DU, an indication associated with an SDT scheme selection for the UE from the CU; and, if CG-SDT is configured, send, by the DU, CG-SDT resource configuration information, e.g., first CG-SDT resource configuration information for the UE, to the CU; and receive, by the DU, an RRC release message from the CU together with the first CG-SDT resource configuration information, to transition the UE to an unconnected state.

[0101] The methods according to the embodiments of the present application may be implemented on a programmed processor. However, the controller, flowcharts, and modules may also be implemented on a general-purpose or special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, integrated circuits, discrete element circuits, or other hardware electronic or logic circuits, programmable logic devices, etc. In general, any device on which a finite state machine capable of implementing the flowcharts shown in the figures exists may be used to implement the processor functions of the present application. For example, the embodiments of the present application provide an apparatus including a processor and a memory. Computer-programmable instructions for implementing the method are stored in the memory, and the processor is configured to execute the computer-programmable instructions to implement the method. The method may be any of the methods described above or other methods according to the embodiments of the present application.

[0102] An alternative embodiment preferably implements a method according to an embodiment of the present application in a non-transitory computer-readable storage medium having stored thereon computer-programmable instructions. These instructions are preferably executed by a computer-executable component, preferably integrated with the network security system. The non-transitory computer-readable storage medium may be stored in any suitable computer-readable medium, such as RAM, ROM, flash memory, EEPROM, an optical storage device (CD or DVD), a hard drive, a floppy drive, or any suitable device. The computer-executable component is preferably a processor, although the instructions may alternatively or additionally be executed by any suitable dedicated hardware device. For example, an embodiment of the present application provides a non-transitory computer-readable storage medium having stored thereon computer-programmable instructions. The computer-programmable instructions are configured to implement the method described above or other methods according to embodiments of the present application.

[0103] While the present application has been described using specific embodiments, it is apparent that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in other embodiments. Also, not all elements in each drawing are necessarily required for the operation of the disclosed embodiments. For example, one skilled in the art of the disclosed embodiments will be able to make and use the teachings of the present application by simply employing the elements of the independent claims. Accordingly, the embodiments of the present application described herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the present application. [Explanation of symbols]

[0104] 100 Wireless Communication System 101 BS 102 UE, Terminal Device 102a UE 102b UE 200 CU 202 DU 800 equipment 801 Non-Transitory Computer-Readable Medium 802 receiving circuit 804 Transmitting circuit 806 processor 900 equipment 902 processor 904 Transceiver 906 Receiver circuit, integrated receiver circuit 908 Transmitting circuit, integrated transmitting circuit

Claims

1. 1. A method for small data transmission (SDT), comprising: sending an indication associated with an SDT scheme selection for a user equipment (UE) from a central unit (CU) to a distributed unit (DU); If a configured grant (CG)-SDT is configured, receiving first CG-SDT resource configuration information for the UE from the DU by the CU; sending a radio resource control (RRC) release message to the DU by the CU together with the first CG-SDT resource configuration information to transition the UE to an unconnected state; A method comprising:

2. 2. The method of claim 1, wherein if the CU determines that a CG-SDT will be configured for the UE, the instruction associated with SDT scheme selection is a CG-SDT request instruction or a CG-SDT query instruction.

3. 2. The method of claim 1, wherein the indication associated with SDT scheme selection is an SDT indication that indicates to the DU whether a Data Radio Bearer (DRB) or a Quality of Service (QoS) flow or a Protocol Data Unit (PDU) session is subject to SDT.

4. storing, by the CU, the first CG-SDT resource configuration information received from the DU; receiving, by the CU, from the DU, a random access (RA)-SDT indication indicating that RA-SDT is to be performed by the UE entering the disconnected state caused by the RRC release message; transmitting the first CG-SDT resource configuration information to the DU by the CU, such that CG-SDT resource configuration information is reconfigured for the UE based on the first CG-SDT resource configuration information after the RA-SDT; 2. The method of claim 1, comprising:

5. receiving, by the CU, from the DU, a random access (RA)-SDT indication indicating that RA-SDT is to be performed by the UE entering the disconnected state caused by the RRC release message; transmitting, by the CU, an identity of the first CG-SDT resource configuration information to the DU, so that CG-SDT resource configuration information is reconfigured for the UE based on the first CG-SDT resource configuration information after the RA-SDT; 2. The method of claim 1, comprising:

6. receiving a time alignment timer (TAT)-SDT by the CU from the DU; initiating the TAT-SDT by the CU in response to triggering a UE context release procedure; stopping the TAT-SDT by the CU in response to receiving small data or a resume request message; 2. The method of claim 1, comprising:

7. 7. The method of claim 6, comprising: in response to expiration of the TAT-SDT, releasing, by the CU, a logical F1 connection and associated UE context associated with the UE.

8. 2. The method of claim 1, comprising: receiving, by the CU from the DU, a UE context release request message to request the CU to release a logical F1 connection associated with the UE, wherein the UE context release request message includes a cause value indicating that the UE context release request message is caused by expiry of a time alignment timer (TAT)-SDT.

9. 1. A method for small data transmission (SDT), comprising: receiving, by a distributed unit (DU) from a central unit (CU), an indication associated with an SDT scheme selection for a user equipment (UE); If a configured grant (CG)-SDT is configured, sending first CG-SDT resource configuration information for the UE to the CU by the DU; receiving, by the DU from the CU, a Radio Resource Control (RRC) Release message for transitioning the UE to an unconnected state, together with the first CG-SDT resource configuration information; A method comprising:

10. The method of claim 9, wherein the indication associated with an SDT scheme selection is a CG-SDT request indication or a CG-SDT query indication, which indicates to the DU that a CG-SDT is needed or requested to be configured for the UE.

11. The indication associated with SDT scheme selection is an SDT indication that indicates to the DU whether a Data Radio Bearer (DRB) or a Quality of Service (QoS) flow or a Protocol Data Unit (PDU) session is subject to SDT; The method further includes determining whether a CG-SDT is to be configured by the DU. The method of claim 9.

12. 1. A method for small data transmission (SDT), comprising: receiving a radio resource control (RRC) release message from a network side by the UE, together with a first configured grant (CG)-SDT resource configuration information; entering a disconnected state in response to receiving the RRC release message; Receipt of another RRC release message, Fallback from CG-SDT to Random Access (RA)-SDT or non-SDT, receiving a network indication indicating release of the first CG-SDT resource configuration information; and expiration of a time alignment timer (TAT)-SDT associated with the first CG-SDT resource configuration information; releasing, by the UE, the first CG-SDT resource configuration information in response to one of A method comprising:

13. A central unit (CU) of a radio access network (RAN) node, comprising: a processor; a transceiver coupled to the processor; Including, the processor: Sending an indication associated with an SDT scheme selection for a user equipment (UE) from the CU to a distributed unit (DU); If a configured grant (CG)-SDT is configured, receiving first CG-SDT resource configuration information for the UE from the DU by the CU; A radio resource control (RRC) release message for transitioning the UE to an unconnected state is sent by the CU to the DU together with the first CG-SDT resource configuration information. It is configured as follows: Central Unit (CU).

14. A distributed unit (DU) of a radio access network (RAN) node, comprising: a processor; a transceiver coupled to the processor; Including, the processor: receiving, by the DU from a central unit (CU), an indication associated with an SDT scheme selection for a user equipment (UE); If a configured grant (CG)-SDT is configured, sending first CG-SDT resource configuration information for the UE to the CU by the DU; receiving, by the DU from the CU, a radio resource control (RRC) release message for transitioning the UE to an unconnected state, together with the first CG-SDT resource configuration information; It is configured as follows: Distributed Unit (DU).

15. A user equipment (UE), a processor; a transceiver coupled to the processor; Including, the processor: receiving a radio resource control (RRC) release message by the UE from a network side, together with a first configured grant (CG)-SDT resource configuration information; entering a disconnected state in response to receiving the RRC release message; Receipt of another RRC release message, Random Access (RA) - Fallback to SDT or non-SDT, receiving a network indication indicating release of the first CG-SDT resource configuration information; and expiration of a time alignment timer (TAT)-SDT associated with the first CG-SDT resource configuration information; and releasing the first CG-SDT resource configuration information in response to one of the following: It is configured as follows: User Equipment (UE).

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