Method and device for initiating small data transmission in nr inactive state

Abstract

The present disclosure provides apparatus and methods for initiating ISDT. In one example, a UE verifies one or more sets of conditions to select an ISDT initiation procedure. The UE first verifies whether a set of ISDT conditions is met, and selects an ISDT initiation procedure according to one or more selected sets of conditions, otherwise the UE enters a connected state. In one embodiment, the ISDT conditions include a data volume less than or equal to a preconfigured ISDT data volume threshold, the UE has a valid inactive AS context, no fallback indication is received, and the wireless network supports ISDT. In another embodiment, the ISDT conditions further include a RSRP greater than or equal to a preconfigured RSRP threshold. In one embodiment, the ISDT initiation procedures include a RRC-based RA procedure, a RRC-based CG procedure, a RRC-less RA procedure, and a RRC-less CG procedure. By utilizing the present disclosure, small data transmission can be more efficiently initiated in the UE inactive state.

Description

[0001] Cross-references

[0002] This application is filed under 35 USC §111(a), and claims priority under 35 USC §120 and §365(c) based on and claims international application No. PCT / CN2020 / 115129, filed on September 14, 2020, entitled “Apparatus and methods to initiate small data transmission in NR inactive state”, and the above applications are incorporated herein by reference. Technical Field

[0003] This invention relates to wireless communication, and more particularly to initiating small data transmissions in the inactive state of a new radio (NR). Background Technology

[0004] 5G radio access technology will become a key component of modern access networks, addressing the growing demands for high traffic growth, energy efficiency, and high-bandwidth connectivity. It will also support massive numbers of connected devices, meeting the real-time, high-reliability communication requirements of mission-critical applications. 5G networks introduce a radio resource control (RRC) inactive state to reduce control plane and user plane latency. In the RRC inactive state, the UE is always connected to the core network (CN), making the transition from inactive to connected state more efficient than from idle to connected state. However, for any downlink (DL) and uplink (UL) data, the UE must first transition from inactive to connected state and complete the connection restoration process. Data transmission and reception occur in connected state, with each data transmission involving connection establishment and subsequent release to inactive state. The transition involves numerous signaling sequences between the UE and the network. When the amount of data exchanged between wireless devices and the network is small and often not urgent, the high power consumption required to handle all the signaling involved in the traditional inactive-to-connected state transition is unreasonable. The initiation process for small data transmissions in the UE inactive state presents a new challenge for achieving more efficient small data transmissions in inactive states.

[0005] Therefore, improvements are needed to more efficiently initiate small data transmissions when the UE is inactive. Summary of the Invention

[0006] This invention provides an apparatus and method for initiating ISDT in a wireless network. In one example, the UE verifies one or more sets of conditions to select an ISDT initiation process and initiates ISDT through the selected process. The UE first verifies whether an ISDT condition set is met to select an ISDT initiation process; otherwise, the UE enters a connected state for data transmission. In one embodiment, the ISDT conditions include a data volume less than or equal to a pre-configured ISDT data volume threshold, the UE having a valid inactive AS context, no fallback indication received, and the wireless network supporting ISDT. In another embodiment, the ISDT conditions further include RSRP greater than or equal to a pre-configured RSRP threshold. Different processes may define different sets of conditions. CG conditions without RRC include: the UE having a valid CG configuration, the UE having a valid time alignment value, the data volume less than or equal to the CG configuration value, no security update required, and no reconfiguration required. CG conditions based on RRC include: the UE having a valid CG configuration, the UE having a valid time alignment value, and the data volume less than or equal to the CG configuration value. RA conditions without RRC include: the data volume less than or equal to the ISDT configuration value, no security update required, no reconfiguration required, and support for ISDT without RRC. The RA conditions based on RRC include data volume less than or equal to the ISDT configuration value and support for ISDT. In one embodiment, when the UE initiates ISDT, the following conditions are further verified: the upper layer requests data transmission from the RB configured with ISDT, the UE has a valid UE inactive AS context, and no fallback indication has been received from the lower layer. In another embodiment, the ISDT conditions further include RSRP greater than or equal to a pre-configured RSRP threshold.

[0007] This section is not intended to define the invention; the invention is defined by the claims.

[0008] By utilizing this invention, small data transmission can be initiated more efficiently when the UE is inactive. Attached Figure Description

[0009] The accompanying drawings illustrate embodiments of the invention, wherein the same numbers indicate the same components.

[0010] Figure 1 This is a schematic system diagram of an exemplary wireless communication network that supports ISDT and small data transmission in an inactive state.

[0011] Figure 2 This is a schematic diagram of an exemplary NR wireless system with a centralized upper layer and an NR radio interface stack.

[0012] Figure 3 It is a model top-level flowchart for initiating ISDT.

[0013] Figure 4This is a sample flowchart of ISDT initiating process options, including RRC-based processes, non-RRC processes, RA processes, and CG processes.

[0014] Figure 5 This is a sample flowchart for ISDT initiating process selection.

[0015] Figure 6 This is a sample flowchart illustrating the process selection initiated by ISDT when it does not support RRC.

[0016] Figure 7 This is a flowchart illustrating the selection process for an exemplary ISDT initiation process that supports or does not support RRC-free.

[0017] Figure 8 This is a demonstrative flowchart of the ISDT initiation process, including the CG process without RRC, the RA process without RRC, the CG process based on RRC, and the RA process based on RRC.

[0018] Figure 9 This is an exemplary diagram illustrating the one-step selection of the ISDT initiating process based on the set of selection criteria corresponding to the possible ISDT initiating processes.

[0019] Figure 10 This is an exemplary diagram illustrating the calculation of the amount of data used for ISDT initiation process selection.

[0020] Figure 11 This is a sample flowchart for selecting the ISDT initiation process. Detailed Implementation

[0021] Some embodiments of the present invention are now given in detail for reference, examples of which are described in the accompanying drawings.

[0022] Figure 1This is a schematic system diagram of an exemplary wireless communication network 100 supporting ISDT and small data transmission in inactive states. The wireless communication network 100 includes one or more fixed infrastructure units forming a network distributed across a geographical area. Infrastructure units may also be referred to as access points, access terminals, base stations, Node Bs, evolved Node Bs (eNode-Bs), next-generation Node Bs (gNBs), or other terms used in the art. Base stations may serve multiple mobile stations within a service area (such as a cell or a sector of a cell). In some systems, one or more base stations are coupled to a controller to form an access network coupled to one or more core networks. gNBs 106, 107, and 108 are base stations in a wireless network whose service areas may or may not overlap. In one embodiment, a user equipment (UE) or mobile station 101 is located within the service areas covered by gNBs 106 and 107. As an example, a UE or mobile station 101 is located only within the service area of ​​gNB 106 and connected to gNB 106. UE or mobile station 102 is located only within the service area of ​​gNB 107 and connected to gNB 107. gNB 106 is connected to gNB 107 via Xn interface 121. gNB 106 is connected to gNB 108 via Xn interface 122. 5G network entity 109 is connected to gNB 106, 107, and 108 via NG connections 131, 132, and 133, respectively. In one embodiment, UE 101 is configured to transmit data in an inactive state without transitioning to a connected state.

[0023] In one embodiment, the UE initiates data transmission and / or reception in an inactive state. In one embodiment, data transmission is inactive small data transmission (ISDT) as shown in block 110. NR networks support many services with infrequent and small data packets, such as services from instant messaging (IM) services, heart-beat / keep-alive services from IM / email clients and other applications, and push notifications from various applications, which are typical use cases for smartphone applications. For non-smartphone applications, services from wearable devices, sensors, and smart meters / smart meter networks that periodically send meter readings are typical use cases. For these small data packets in block 110, data transmission and / or reception can be initiated in an inactive state.

[0024] Figure 1A simplified block diagram of the base station and mobile device / UE for data transmission and reception in an inactive state is further shown. Figure 1 A simplified block diagram of a UE, such as UE 101, is provided. The UE has an antenna 165 for transmitting and receiving radio signals. An RF transceiver circuit 163 coupled to the antenna receives RF signals from the antenna 165, converts the RF signals into baseband signals, and sends the baseband signals to a processor 162. In one embodiment, the RF transceiver may include two RF modules (not shown). A first RF module is used for high-frequency (HF) transmission and reception, and a second RF module is used for transmission and reception in a different frequency band than that of the HF transceiver. The RF transceiver 163 also converts the baseband signals received from the processor 162 into RF signals and sends them to the antenna 165. The processor 162 processes the received baseband signals and invokes different functional modules to perform functional features in UE 101. Memory 161 stores program instructions and data 164 to control the operation of UE 101. The memory also stores the UE inactive access stratum (AS) context, which includes the current KgNB and KRRCint keys, robust header compression (ROHC) state, stored QoS flow-to-dedicated radio bearer (DRB) mapping rules, the cell radio network temporary identifier (C-RNTI) used in the source PCell, the cell identifier and physical cell identifier of the source PCell, and / or other parameters. In one embodiment, the UE inactive AS context also includes another set of parameters configured for data transmission in the inactive state, including physical (PHY) layer and media access control (MAC) layer configurations. In one embodiment, the physical layer configuration includes pre-configured UL resources that can be used for UL data transmission in the inactive state. In one embodiment, the physical layer configuration includes MAC configuration, such as MAC cell group configuration (MAC-CellGroupConfig). Antenna 165 sends uplink transmissions to antenna 156 of gNB 101 and receives downlink transmissions from antenna 156 of gNB 101.

[0025] UE 101 also includes a set of control modules for performing functional tasks. These functional modules can be implemented via circuitry, software, firmware, or a combination thereof. ISDT verification module 191 verifies a pre-configured set of ISDT conditions in the wireless network, wherein the UE is configured to perform small data transmission in the UE inactive state when the pre-configured ISDT conditions are met. Selection module 192 selects an ISDT initiation process based on one or more selection condition sets, including selection condition sets for radio resource control (RRC) processes and selection condition sets for UL resource acquisition processes. The RRC process is either an RRC-based process or an RRC-less process, and the UL resource acquisition process is a random access (RA) or configured grant (CG) process. Initiation module 193 initiates small data transmission in the UE inactive state according to the selected ISDT initiation process. ISDT module 194 performs one or more small data transmissions in the UE inactive state.

[0026] The UE may also be configured with other optional control modules, including an RRC state control module 181, a DRB control module 182, an AS context control module 183, and a protocol control module 184. The RRC state control module 181 controls the UE RRC state according to network commands and UE conditions. The UE RRC supports the following states: RRC idle, RRC connected, and RRC inactive. In one embodiment, the UE is configured to send UL data to the network once or multiple times in the inactive state. In one embodiment, UL data transmission in the inactive state is configured according to DRBs. When the total data volume of those DRBs arriving at the buffer is less than a threshold, the UE may initiate data transmission for these DRBs. In one embodiment, the network configures the data volume threshold through system information or dedicated RRC signaling. The DRB control module 182 suspends or resumes the DRB. In one embodiment, the network configures one or more specific DRBs whose data packets can be transmitted in the inactive state. In one embodiment, the DRB is resumed when a data burst is to be transmitted. The DRB is suspended when the data burst transmission is complete. The inactive AS context control module 183 is used to store, restore, or release the UE's inactive AS context. In one embodiment, the UE inactive AS context controller determines which parameters or sets of parameters to restore based on whether the UE initiated data transmission in an inactive state. In one embodiment, the UE restores all stored parameters, including MAC configuration and physical layer configuration. The protocol control module 184 controls the establishment, reconstruction, release, reset, and reconfiguration of user plane protocols, including the packet data convergence protocol (PDCP), radio link control (RLC), and MAC. In one embodiment, the service data adaptation protocol (SDAP) layer is an optional configuration.

[0027] Figure 1Further, a simplified block diagram of a gNB, such as gNB 106, is included. gNB 106 has an antenna 156 that transmits and receives radio signals. An RF transceiver circuit 153 coupled to this antenna receives RF signals from antenna 156, converts the RF signals into baseband signals, and sends the baseband signals to processor 152. RF transceiver 153 also converts baseband signals received from processor 152 into RF signals and sends them to antenna 156. Processor 152 processes the received baseband signals and invokes different functional modules to perform functional features in gNB 106. Memory 151 stores program instructions and data 154 to control the operation of gNB 106. Memory 151 also stores the UE inactive AS context. In one embodiment, the UE inactive AS context also includes another set of parameters configured for data transmission in the inactive state, including physical layer and MAC layer configurations. gNB 106 also includes a set of control modules 155 for performing functional tasks to communicate with mobile stations. The control module group 155 includes an RRC state controller, a DRB controller, an inactive AS context controller, and a protocol controller. The RRC state controller controls the UE's RRC state by sending commands to the UE or providing configuration of state transition conditions. The DRB controller suspends or resumes the UE's DRB. In one embodiment, the DRB is resumed when a data burst is to be transmitted. The DRB is suspended when the data burst transmission is complete. The inactive AS context controller is used to store, restore, or release the UE's inactive AS context. The protocol controller is used to control the establishment, reconstruction, release, reset, and configuration of user plane protocols, including PDCP, RLC, and MAC. In one embodiment, the SDAP layer can be optionally configured. The gNB may also include multiple functional modules. The RA module performs random access for the UE, supporting both 2-step and 4-step RA processes. The CG module receives data on pre-configured PUSCH resources. RRC-based modules receive ISDTs from the UE via RRC messages / processes (such as RRC Resume Request). RRC-free modules receive ISDTs from the UE without RRC messages.

[0028] Figure 2This is a schematic diagram of an exemplary NR wireless system with a centralized upper layer and an NR radio interface stack. Different protocol partitioning options may exist between the upper layer of the central unit (CU) / gNB node and the lower layer of the distributed unit (DU) / gNB node. The functional partitioning between the central unit and the lower gNB layer may depend on the transport layer. Since higher protocol layers have lower performance requirements for the transport layer in terms of bandwidth, latency, synchronization, and jitter, low-performance transmission between the central unit and the lower gNB layer can enable higher protocol layers of the NR radio stack to be supported in the central unit. In one embodiment, the SDAP and PDCP layers are located in the central unit, while the RLC, MAC, and physical layers are located in the distributed unit. The core unit 201 is connected to the central unit 211, which has a gNB upper layer 252. In one embodiment, the gNB upper layer 252 includes a PDCP layer and an optional SDAP layer. Central unit 211 is connected to distributed units 221, 222, and 223, which correspond to cells 231, 232, and 233, respectively. Distributed units 221, 222, and 223 include a gNB lower layer 251. In one embodiment, the gNB lower layer 251 includes PHY, MAC, and RLC layers. In another embodiment 260, each gNB has a protocol stack 261 including SDAP, PDCP, RLC, MAC, and PHY layers.

[0029] Figure 3 This is an exemplary top-level flowchart for initiating an ISDT. The UE initiates data transmission in an inactive state. In step 301, the UE verifies whether a pre-configured ISDT condition set is met to determine whether to initiate an ISDT or enter a connected state for data transmission. In step 302, if step 301 verifies that the pre-configured ISDT condition set is met, the UE selects an ISDT initiation process. The UE selects an ISDT initiation process based on one or more selection condition sets. According to embodiment 320, the selection condition sets include an RRC process selection condition set 321 and a UL resource acquisition process selection condition set 322. Selection 321 selects an RRC process from RRC-based processes and non-RRC processes. Selection 322 selects a UL resource acquisition process from RA processes and CG processes. The ISDT initiation process is an RRC-based RA process, an RRC-based CG process, a non-RRC RA process, or a non-RRC CG process. After initiating an ISDT using the selected ISDT initiation process, in step 303, the UE executes the ISDT.

[0030] Figure 4This is an exemplary flowchart of the ISDT initiation process options, including RRC-based processes, non-RRC processes, RA processes, and CG processes. Upon confirming that ISDT has been selected, UE 401 communicates with gNB 402 to select the initiation process for ISDT. UE 401 selects RRC process 481, such as RRC-based process 410 and non-RRC process 420. UE 401 also selects resource acquisition process 482, which includes RA process 483 and CG process 450. RA process 483 includes a 4-step RA process 430 and a 2-step RA process 440.

[0031] In RRC-based process 410, when UL data exists on an RB configured with ISDT, the upper layer requests the resumption of a suspended RRC connection. The UE transmits UL data during the RRC resumption process. In one embodiment, UE 401 sends an RRC resumption request message and UL data in step 411. In step 412, the UE receives an RRC release message with suspend configuration. Subsequently, UE 401 enters an inactive state after data transmission is complete. In another embodiment, when UL data exists on an RB configured with ISDT, the upper layer requests direct data transmission without resuming the suspended RRC connection. In RRC-free process 420, UE 401 directly transmits UL data in step 421 without any RRC message. In step 422, UE 401 receives an L1 or L2 acknowledgement (ACK) as a response.

[0032] The UE also selects the initiation process for UL resources, including the RA process and the CG process. If UL data is transmitted via the RA process, the UL data is transmitted via MSG3 (in the 4-step RA) / MSGA (in the 2-step RA). If UL data is transmitted via the CG process, the UL data is transmitted via the configured UL grant. The UL grant is provided by the network via RRC messages through a dedicated configuration. In the 4-step RA process 430, UE 401 sends MSG1 in step 431. In step 432, UE 401 receives MSG2 from gNB 402. In step 433, UE 401 sends MSG3 with data to gNB 402. In step 434, UE 401 receives MSG4 from gNB 402. In the 2-step process 440, UE 401 sends MSGA including data to gNB 402 in step 441. In step 442, UE 401 receives MSGB from gNB 402. In CG process 450, in step 451, UE 401 sends UL data using the resources provided by UL authorization.

[0033] Figure 5This is an exemplary flowchart for ISDT initiation process selection. In step 501, the UE determines, based on a predefined ISDT condition set 510, whether to initiate an ISDT process or restore the RRC connection (i.e., transition to a connected state) via a conventional process for data transmission. ISDT conditions 510 include the presence of UL data in the RB configured with ISDT, the data volume being less than or equal to a preconfigured ISDT data volume threshold, the UE having a valid inactive AS context, no fallback indication being received, and the radio network supporting ISDT. In other embodiments, ISDT conditions also include a reference signal received power (RSRP) greater than or equal to a preconfigured RSRP threshold. The preconfigured ISDT condition set, also known as the ISDT general conditions, applies to all ISDT initiation processes. If step 501 determines that the predefined ISDT condition set is met, the UE initiates ISDT. Otherwise, in step 511, the UE restores the RRC connection and transitions to an RRC connected state for data transmission. If step 501 determines to initiate ISDT, the UE determines in step 502 whether to use a process without RRC or based on RRC, and in step 503 whether to use a CG or RA process. The order of steps 502 and 503 is interchangeable. In step 502, the UE determines whether to use an RRC-free process based on selection condition 520. Selection condition 520 includes network support for RRC-free ISDT, no security update required, and no reconfiguration required. According to some embodiments, security updates include security configuration (such as security keys and algorithms) updates. If step 502 determines to select an RRC-free process, the UE determines in step 504 whether to use a CG or RA process. If step 502 determines to select an RRC-based process, in step 503, the UE determines in step 503 whether to carry the ISDT via RA or CG based on selection condition 530, which includes valid pre-configured UL resources, valid time alignment, and data volume less than or equal to a pre-configured CG data volume threshold. If step 503 determines yes, the UE selects the RRC-based CG process for ISDT initiation in step 531. Otherwise, the UE selects the RRC-based RA process for ISDT initiation in step 532. Similarly, if step 504 is determined to be yes according to selection condition 530, the UE selects a no-RRC CG process for ISDT initiation in step 521. If step 504 is determined to be no according to selection condition 530, the UE selects a no-RRC RA process for ISDT initiation in step 522. In one embodiment, when the UE selects an RA process for ISDT initiation, as shown in steps 522 and 532, the UE further determines whether to use a 2-step RA or a 4-step RA. When the RSRP is greater than the pre-configured 2-step RSRP threshold, the UE selects a 2-step RA process for ISDT initiation.

[0034] The order of steps 502 and 503 can be changed; the UE can first choose between RA and CG, and then choose between RRC-based and RRC-free schemes. In one embodiment, the pre-configured ISDT data volume threshold for ISDT initiation and the pre-configured CG data volume threshold for CG transmission are the same. In another embodiment, the pre-configured CG data volume threshold for CG transmission is the value of the transmission block (TB) size. The UE compares the sum of the sizes of the total data volume with the maximum TB size configured by the network. After the two-step selection, the UE initiates ISDT by combining the two selections (including RRC-based RA process, RRC-free RA process, RRC-based CG process, and RRC-free CG process).

[0035] Figure 6This is an exemplary flowchart illustrating the ISDT initiation process selection when ISDT does not support RRC-free initiation. In one embodiment, ISDT is always performed via RRC messages, eliminating the need to choose between RRC-based and RRC-free initiation. When the wireless network does not support RRC-free initiation for ISDT, the ISDT initiation process is selected from both RRC-based RA and RRC-based CG processes. In step 601, the UE determines whether to initiate an ISDT process or transition to a connected state for data transmission based on a predefined ISDT condition set 610. ISDT conditions 610 include the presence of UL data in the RB configured with ISDT, data volume less than or equal to a pre-configured ISDT data volume threshold, a valid inactive AS context for the UE, no fallback indication received, and the wireless network supporting ISDT. In other embodiments, ISDT conditions 610 also include RSRP greater than or equal to a pre-configured RSRP threshold. The pre-configured ISDT condition set, also known as ISDT general conditions, applies to all ISDT initiation processes. If step 601 determines that the predefined ISDT condition set is met, the UE initiates ISDT. Otherwise, in step 611, the UE restores the RRC connection and transitions to the RRC connection state for data transmission. Since ISDT without RRC is not supported, when determining whether to use ISDT, the UE selects either the CG or RA process to initiate ISDT. In step 602, the UE determines whether the pre-configured CG condition set 620 is met. CG condition 620 includes having valid pre-configured UL resources, having valid time alignment, and a data volume less than or equal to a pre-configured CG data volume threshold. If step 602 determines yes, the UE selects the RRC-based CG process for ISDT initiation. If step 602 determines no, the UE selects the RRC-based RA process for ISDT initiation. In one embodiment, the UE further determines in step 604 whether to use a 2-step RA or 4-step RA process based on a pre-configured 2-step RA condition 630, where the 2-step RA condition 630 includes RSRP greater than a pre-configured 2-step RSRP threshold. If step 604 determines yes, the UE selects the RRC-based 2-step RA to initiate ISDT; otherwise, it selects the RRC-based 4-step RA to initiate ISDT.

[0036] Figure 7This is a flowchart illustrating the selection of an exemplary ISDT initiation process that supports or does not support RRC-free ISDT. In step 701, the UE selects an ISDT initiation process. In step 702, the UE initiates the ISDT using the selected initiation process. When selecting an ISDT initiation process, the UE determines in step 711 whether the network supports RRC-free ISDT. If the network supports RRC-free ISDT, the UE selects from ISDT initiation process list 721, which includes RRC-free CG processes, RRC-free RA processes, RRC-based CG processes, and RRC-based RA processes. If the network does not support RRC-free ISDT, the UE selects from ISDT initiation process list 722, which includes RRC-based CG processes and RRC-based RA processes.

[0037] Figure 8 This is an exemplary flowchart of the ISDT initiation process, including the CG process without RRC, the RA process without RRC, the CG process based on RRC, and the RA process based on RRC. UE 801 connects to gNB 802 in the wireless network and selects the ISDT initiation process. The ISDT initiation process includes the CG process without RRC 810, the CG process based on RRC 820, the RA process without RRC 830, and the RA process based on RRC 840. The RA process without RRC 830 includes a 4-step process 8301 and a 2-step process 8302, and the RA process based on RRC 840 includes a 4-step process 8401 and a 2-step process 8402.

[0038] For the CG process 810 without RRC, UE 801 directly sends UL data in step 811 without any RRC message. In step 812, UE 801 receives an L1 or L2 acknowledgment from gNB 802 in response. UL data can be transmitted based on the configured UL grant, which can be provided by the network through dedicated configuration and RRC messages. For the RRC-based CG process 820, when UL data exists in an RB configured with ISDT, the upper layer requests the resumption of a suspended RRC connection. UE 801 sends UL data during the RRC resumption process. In one embodiment, in step 821, UE 801 sends UL data including an RRC resumption request message through the configured UL resources. In one embodiment, in step 822, UE 801 subsequently receives an RRC release message with a suspended configuration, which transitions UE 801 to an inactive state after data transmission is complete. In one embodiment, UE 801 receives an L1 / L2 ACK in response to the RRC resumption request, which transitions UE 801 to an inactive state.

[0039] In the RA process 830 without RRC, UE 801 directly transmits UL data without any RRC messages. In one embodiment, when an RB with ISDT is configured to transmit UL data, the upper layer requests direct data transmission without restoring the suspended RRC connection. The UE transmits UL data in MSG3 (4-step RA) / MSGA (2-step RA). For the 4-step RA process 8301 without RRC, UE 801 transmits MSG1 to gNB 802 in step 831. In step 832, UE 801 receives MGS2 from gNB 802. In step 833, UE 801 transmits MSG3 with data to gNB 802. In step 834, UE 801 receives MSG4 from gNB 802. For the 2-step RA process 8302 without RRC, in step 836, UE 801 transmits MSGA with data to gNB 802. In step 837, UE 801 receives MSGB from gNB 802.

[0040] In the RRC-based RA process 840, when an RB configured with ISDT has UL data, the upper layer requests the resumption of a suspended RRC connection. UE 801 transmits UL data during the RRC resumption process. In one embodiment, the UE transmits UL data with an RRC resumption request message in MSG3 (4-step RA) / MSGA (2-step RA). In another embodiment, the UE receives an RRC release message with a suspended configuration in MSG4 (4-step RA) / MSGB (2-step RA), and then transitions the UE to an inactive state after data transmission is complete. For the RRC-based 4-step RA process 8401, in step 841, UE 801 sends MSG1 to gNB 802. In step 842, UE 801 receives MGS2 from gNB 802. In step 843, UE 801 sends MSG 3 with an RRC resumption request and data to gNB 802. In step 844, UE 801 receives MSG4 with an RRC release message from gNB 802. For the two-step RA process 8402 based on RRC, in step 846, UE 801 sends an MSGA containing an RRC recovery request and data to gNB 802. In step 847, UE 801 receives an MSGB containing an RRC release message from gNB 802. When the ISDT condition is not met, the UE can switch to the connected state to send data packets. The upper layer can request the resumption of the suspended RRC connection. The UE can execute the RRC connection recovery process and switch to the connected state through the RA process. Subsequently, the UE begins UL data transmission. After the data transmission is completed, the RRC release message can be received.

[0041] Figure 9This is an exemplary diagram illustrating the one-step selection of an ISDT initiation process based on a set of selection conditions corresponding to possible ISDT initiation processes. To initiate an ISDT, the upper layer requests data transmission from the RB configured with the ISDT. The UE checks different sets of conditions to determine which process to use to initiate the ISDT. In step 9001, the UE determines whether the ISDT general condition 900 is met. The ISDT general condition 900 includes a data volume less than or equal to a pre-configured data volume threshold, the UE having a valid inactive AS context, no fallback indication received, and the radio network supporting ISDT. In another embodiment, the ISDT general condition 900 also includes an RSRP greater than or equal to a pre-configured RSRP threshold. In step 901, when the ISDT condition is met and the RRC-free CG condition 910 is met, the RRC-free CG process 911 is selected. The RRC-free CG condition 910 includes the presence of a valid pre-configured UL resource, the presence of valid time alignment, a data volume less than or equal to a pre-configured CG data volume threshold, and support for RRC-free ISDT. In step 902, when the ISDT condition is met and the RRC-based CG condition 920 is met, the RRC-based CG process 921 is selected. The RRC-based CG condition 920 includes the existence of valid pre-configured UL resources, valid time alignment, and data volume less than or equal to the pre-configured CG data volume threshold. In step 903, when the ISDT condition and the RRC-free RA condition 930 are met, the RRC-free RA process 931 is selected. The RRC-free RA condition 930 includes no security update required, no reconfiguration required, data volume less than or equal to the pre-configured ISDT data volume threshold, and support for RRC-free ISDT. In step 904, when the ISDT condition and the RRC-based RA condition 940 are met, the RRC-based RA process 941 is selected. In step 905, when the connection state transmission condition 950 is met, the UE enters the connected state. The connection state transmission condition 950 includes data volume greater than the pre-configured ISDT data volume threshold and network not supporting ISDT. Steps 901 to 905 can be performed as follows: Figure 9 The execution order shown gives the highest priority to CGs without RRC. Of course, any other selection order can also be used. The UE can pre-configure different preferences or priorities for available ISDT initiation processes. ISDT initiation process preferences / priors can also be dynamically configured and changed.

[0042] Figure 10This is an exemplary schematic diagram of the data volume calculation used for ISDT initiation process selection. In step 1001, the UE determines the data volume calculation to consider ISDT initiation process selection. In one embodiment 1010, the data volume calculation considers both the signalalling radio bearer (SRB) and the dedicated radio bearer (DRB). In one embodiment 1020, the data volume calculation considers only the DRB. In one embodiment 1030, the data volume calculation considers only the DRB configured with ISDT. For each RB, from the perspective of PDCP 1050, the data volume considers: PDCP SDU 1051 that has not been constructed into a PDCP data PDU, PDCP data PDU 1052 that has not yet been submitted to the lower layer, PDCP control PDU 1053, PDCP SDU 1054 that needs to be retransmitted for acknowledged mode (AM) DRB, and PDCP data PDU that needs to be retransmitted for AM DRB. From the perspective of RLC 1060, the data volume is considered as follows: RLC SDU and RLCSDU segments 1061 not yet included in the RLC data PDU, RLC data PDU 1062 waiting for initial transmission, and RLC data PDU 1063 waiting for retransmission (RLC AM).

[0043] Figure 11 This is an exemplary flowchart for selecting an ISDT initiation process. In step 1101, the UE verifies a pre-configured set of ISDT conditions in the wireless network, whereby the UE can perform small data transmission in an inactive state when the pre-configured ISDT conditions are met. In step 1102, the UE selects an ISDT initiation process based on one or more selection condition sets, including a selection condition set for RRC processes and a selection condition set for UL resource acquisition processes, wherein the RRC process is an RRC-based process or a process without RRC, and the UL resource acquisition process is an RA process or a CG process. In step 1103, the UE initiates small data transmission in an inactive state according to the selected ISDT initiation process. In step 1104, the UE performs one or more data transmissions in an inactive state.

[0044] While the invention has been described in conjunction with specific embodiments for illustrative purposes, it is not limited thereto. Therefore, various modifications, adaptations, and combinations of the features of the described embodiments can be made without departing from the scope of the invention as set forth in the claims.

Claims

1. A method of initiating small data transmission in an inactive state, comprising: verifying, by a user equipment, a set of preconfigured inactive small data transmission (ISDT) conditions in a wireless network, wherein the user equipment performs small data transmission in a user equipment inactive state when the set of preconfigured ISDT conditions is met; selecting an ISDT initiation procedure based on one or more sets of selection conditions, wherein the one or more sets of selection conditions comprise a set of selection conditions for a radio resource control (RRC) procedure, the RRC procedure being an RRC-based procedure or an RRC-less procedure, and a set of selection conditions for an uplink resource acquisition procedure, the uplink resource acquisition procedure being a random access (RA) procedure or a configured grant (CG) procedure; initiating small data transmission in the user equipment inactive state according to the selected ISDT initiation procedure; and performing one or more data transmissions in the user equipment inactive state, wherein the set of selection conditions for the uplink resource acquisition procedure is to select the CG procedure when a CG condition is met, and otherwise to select the RA procedure, wherein the CG condition comprises having a valid preconfigured uplink resource, having a valid time alignment, and a data volume being less than or equal to a preconfigured CG data volume threshold. 2.The method of initiating small data transmission in inactive state according to claim 1, characterized in that, when the set of preconfigured ISDT conditions fails to be verified, the user equipment resumes an RRC connection and enters a connected state without ISDT. 3.The method of initiating small data transmission in inactive state according to claim 1, wherein, the set of preconfigured ISDT conditions comprises a data volume being less than or equal to a preconfigured ISDT data volume threshold, the user equipment having a valid inactive access stratum context, no back-off indication being received, and the wireless network supporting ISDT. 4.The method of initiating small data transmission in inactive state according to claim 3, characterized in that, the set of preconfigured ISDT conditions further comprises a reference signal received power (RSRP) being greater than or equal to a preconfigured RSRP threshold. 5.The method of initiating small data transmission in inactive state according to claim 1, wherein, the set of selection conditions for the RRC procedure is to select the RRC-less procedure when an RRC-less condition is met, and otherwise to select the RRC-based procedure, wherein the RRC-less condition comprises the wireless network supporting RRC-less for ISDT, no security update being needed, and no RRC reconfiguration being needed. 6.The method of initiating small data transmission in inactive state according to claim 1, wherein, when the RA procedure is selected for the uplink resource acquisition procedure based on the set of selection conditions, a 2-step RA procedure is selected when a RSRP is greater than a preconfigured 2-step RSRP threshold. 7.The method of initiating small data transmission in inactive state according to claim 1, wherein, the ISDT initiation procedure is an RRC-based RA procedure, an RRC-based CG procedure, an RRC-less RA procedure, or an RRC-less CG procedure. 8.The method of initiating small data transmission in inactive state according to claim 7, wherein, the ISDT initiation procedure is selected by one set of selection conditions. the ISDT initiation procedure is selected by one set of selection conditions. 9.The method of initiating small data transmission in inactive state according to claim 8, wherein, The RRC-less CG procedure is selected when a set of RRC-less CG conditions is met, the RRC-based CG procedure is selected when a set of RRC-based CG conditions is met, the RRC-less RA procedure is selected when a set of RRC-less RA conditions is met, and the RRC-based RA procedure is selected when a set of RRC-based RA conditions is met, wherein the set of RRC-less CG conditions comprises: there is a valid preconfigured UL resource, there is a valid time alignment, a data volume is less than or equal to a preconfigured CG data volume threshold, and ISDT without RRC is supported; the set of RRC-based CG conditions comprises: there is a valid preconfigured UL resource, there is a valid time alignment, and a data volume is less than or equal to a preconfigured CG data volume threshold; the set of RRC-less RA conditions comprises: no security update is needed, no reconfiguration is needed, ISDT without RRC is supported, and a data volume is less than or equal to a preconfigured IDST data volume threshold; and the set of RRC-based RA conditions comprises: a data volume is less than or equal to a preconfigured IDST data volume threshold, and ISDT is supported. 10.The method of initiating small data transmission in inactive state according to claim 7, wherein, When the wireless network does not support a RRC-less procedure for ISDT, the ISDT initiation procedure is a RRC-based RA procedure or a RRC-based CG procedure. 11.A user equipment comprising: a radio frequency transceiver configured to transmit and receive radio signals in a wireless network; a non-active small data transmission (ISDT) validation module configured to validate a set of preconfigured ISDT conditions in the wireless network, wherein the user equipment performs small data transmission in a user equipment non-active state when the set of preconfigured ISDT conditions is met; a selection module configured to select an ISDT initiation procedure based on one or more sets of selection conditions, wherein the one or more sets of selection conditions comprise a set of selection conditions for a radio resource control (RRC) procedure, a set of selection conditions for an uplink resource acquisition procedure, wherein the RRC procedure is a RRC-based procedure or a RRC-less procedure, and the uplink resource acquisition procedure is a random access (RA) procedure or a configured grant (CG) procedure, wherein the set of selection conditions for the uplink resource acquisition procedure is to select the CG procedure when a CG condition is met, and otherwise to select the RA procedure, wherein the CG condition comprises having a valid preconfigured uplink resource, having a valid time alignment, and a data volume being less than or equal to a preconfigured CG data volume threshold; an initiation module configured to initiate small data transmission in the user equipment non-active state according to the selected ISDT initiation procedure; and an ISDT module configured to perform one or more data transmissions in the user equipment non-active state. When the set of preconfigured ISDT conditions validation fails, the user equipment resumes a RRC connection and enters a connected state without performing ISDT.

12. The user equipment of claim 11, wherein, ​ 13. The user equipment of claim 11, wherein, The set of preconfigured ISDT conditions comprises: a data volume less than or equal to a preconfigured ISDT data volume threshold, the user equipment having a valid inactive access stratum context, no fallback indication received, and the wireless network supporting ISDT.

14. The user equipment of claim 13, wherein, The set of preconfigured ISDT conditions further comprises a reference signal received power, RSRP, greater than or equal to a preconfigured RSRP threshold.

15. The user equipment of claim 11, wherein, The set of selection conditions for the RRC procedure is to select the no RRC based procedure when a no RRC condition is met, and otherwise select the RRC based procedure, wherein the no RRC condition comprises the wireless network supporting no RRC for ISDT, no security update needed, and no RRC reconfiguration needed.

16. The user equipment of claim 11, wherein, When the RA procedure is selected for the uplink resource acquisition procedure based on the selection conditions, a 2-step RA procedure is selected when the RSRP is greater than a preconfigured 2-step RSRP threshold.

17. The user equipment of claim 11, wherein, The ISDT initiation procedure is a RRC based RA procedure, a RRC based CG procedure, a no RRC based RA procedure, or a no RRC based CG procedure.

18. The user equipment of claim 17, wherein, The no RRC based CG procedure is selected when a set of no RRC based CG conditions is met, the RRC based CG procedure is selected when a set of RRC based CG conditions is met, the no RRC based RA procedure is selected when a set of no RRC based RA conditions is met, and the RRC based RA procedure is selected when a set of RRC based RA conditions is met, wherein the set of no RRC based CG conditions comprises: a valid preconfigured UL resource exists, a valid time alignment exists, a data volume is less than or equal to a preconfigured CG data volume threshold, and no RRC based ISDT is supported; the set of RRC based CG conditions comprises: a valid preconfigured UL resource exists, a valid time alignment exists, and a data volume is less than or equal to a preconfigured CG data volume threshold; the set of no RRC based RA conditions comprises: no security update needed, no reconfiguration needed, no RRC based ISDT supported, and a data volume is less than or equal to a preconfigured IDST data volume threshold; and the set of RRC based RA conditions comprises: a data volume is less than or equal to a preconfigured IDST data volume threshold, and ISDT is supported.

19. A storage medium storing a program which, when executed, causes a user equipment to perform the steps of the method of initiating a small data transmission in an inactive state of any one of claims 1-10.

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