CN114071804B

CN114071804B - Connectionless data transmission method in inactive state and user equipment

Info

Publication number: CN114071804B
Application number: CN202110844835.5A
Authority: CN
Inventors: 张园园; 徐家俊
Original assignee: MediaTek Singapore Pte Ltd
Current assignee: MediaTek Singapore Pte Ltd
Priority date: 2020-07-31
Filing date: 2021-07-26
Publication date: 2024-03-29
Anticipated expiration: 2041-07-26
Also published as: WO2022021278A1; CN114071804A

Abstract

The embodiment of the invention provides a connectionless data transmission method in an inactive state and user equipment. The connectionless data transmission method in the inactive state provided in one embodiment includes: after determining one or more pre-configured transmission conditions in the wireless network, initiating, by the user equipment, one or more data transmissions in an inactive state of the user equipment without RRC; restoring an inactive access layer context stored in the user equipment, wherein the inactive access layer context comprises an inactive data transmission configuration; establishing uplink resources for one or more data transmissions in an inactive state of the user equipment based on the inactive access layer context; and performing the one or more data transmissions using the uplink resources in the user equipment inactive state. By utilizing the present invention, small data transmission and reception can be performed better.

Description

Connectionless data transmission method in inactive state and user equipment

Technical Field

The present invention relates to wireless communications, and more particularly to data transfer in a connectionless (connectionless) mode.

Background

The 5G radio access technology will become a key component of modern access networks, which will address the demands that it will address for high traffic growth, energy efficiency and the ever-increasing demand for high bandwidth connections. The system also supports mass connection equipment and meets the real-time and high-reliability communication requirements of mission-critical applications. The 5G network introduces a radio resource control (radio resource control, RRC) inactive (inactive) state to reduce control plane and user plane delays. In the RRC inactive state, the UE is always connected to a Core Network (CN), and thus the transition from the inactive state to the connected state is more efficient than the transition from the idle state to the connected state. However, for any Downlink (DL) and Uplink (UL) data, the UE needs to first switch from the inactive state to the connected state and complete the connection recovery procedure, and the data is sent and received in the connected state, and each data transmission is performed to establish a connection and then release the connection to the inactive state. The transition includes a large number of signaling sequences between the UE and the network. When the amount of data exchanged by a wireless device with a network is small and often not urgent enough, the high power consumption required to handle all the signaling involved in the traditional inactive state-to-connected state transition is not reasonable.

In view of this, improvements are needed to achieve more efficient small data (small data) transmission and reception using connectionless data transmission.

Disclosure of Invention

An embodiment of the present invention provides a connectionless data transmission method in an inactive state, including: initiating, by the user equipment, one or more data transmissions in an inactive state of the user equipment without radio resource control connection, RRC, after determining one or more pre-configured transmission conditions in the wireless network; restoring an inactive access layer context stored in the user equipment, wherein the inactive access layer context comprises an inactive data transmission configuration; establishing uplink resources for one or more data transmissions in an inactive state of the user equipment based on the inactive access layer context; and performing the one or more data transmissions using the uplink resources in the user equipment inactive state.

Another embodiment of the present invention provides a user equipment, including: a transceiver for transmitting and receiving wireless signals in a wireless network; a state control module for initiating one or more data transmissions in an inactive state of a user equipment without radio resource control connection, RRC, after determining one or more pre-configured transmission conditions in the wireless network; an access stratum context module for recovering an inactive access stratum context stored in the user equipment, wherein the inactive access stratum context comprises an inactive data transmission configuration; a resource module to establish uplink resources for one or more data transmissions in an inactive state of the user equipment based on the inactive access layer context; and a transmission control module to perform the one or more data transmissions using the uplink resources in the user equipment inactive state.

Another embodiment of the present invention provides a storage medium storing a program that, when executed, causes a user equipment to perform a connectionless data transfer method in an inactive state as set forth in the present invention.

By utilizing the present invention, small data transmission and reception can be performed better.

Drawings

The drawings illustrate embodiments of the invention, wherein like numerals indicate like components.

Fig. 1 is a schematic system diagram of a wireless communication network (system) supporting connectionless data transmission and reception in accordance with an embodiment of the present invention.

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of NR radio interface stacks according to an embodiment of the present invention.

FIG. 3 is an exemplary top-level functional diagram for connectionless data transmission and reception with data suspension or stop and rollback procedures according to an embodiment of the invention.

Fig. 4 is an exemplary flow chart for initiating data transmission in an inactive state without an RRC connection according to an embodiment of the present invention.

Fig. 5 is an exemplary flowchart of performing a data transmission process in an inactive state according to an embodiment of the present invention.

Fig. 6 is an exemplary flowchart of performing connectionless data transfer using an RA procedure in an inactive state, according to an embodiment of the present invention.

Fig. 7 is an exemplary flowchart of performing connectionless data transmission through pre-configured UL resources in an inactive state according to an embodiment of the present invention.

Fig. 8 is an exemplary flowchart for stopping a connectionless data transfer process in an inactive state according to an embodiment of the present invention.

Fig. 9 is an exemplary flowchart for backing off to an RRC recovery procedure and entering a connected state according to an embodiment of the present invention.

Fig. 10 is an exemplary flow chart of connectionless data transfer in an inactive state according to an embodiment of the invention.

Detailed Description

Reference will now be made in detail to some embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

The present invention provides methods, apparatus, processing systems, and computer readable media for a New Radio (NR) access technology or a 5G technology or other radio access technology. NR, etc. may support various wireless communication services such as enhanced mobile broadband for wide bandwidth, millimeter waves for high carrier frequencies, massive MTC for non-backward compatible machine type communication (machine type communication, MTC) technology, and/or critical tasks for ultra-reliable low-latency communications. These services may have delay and reliability requirements. These services may also have different transmission time intervals (transmission time interval, TTI) to meet respective quality of service (quality of service, qoS) requirements. Furthermore, these services may coexist in the same subframe.

Fig. 1 is a schematic system diagram of a wireless communication network (system) 100 supporting connectionless data transmission and reception in accordance with an embodiment of the invention. The wireless system 100 includes one or more fixed infrastructure elements forming a network distributed over a geographic area. The infrastructure element may also be referred to as an access point, an access terminal, a base station, a node B, an evolved node B (eNode-B), a next generation node B (gNB), or other terminology used in the art. A base station may serve multiple mobile stations within a service area (e.g., a cell or a sector of a cell), e.g., a cell, or a cell sector. 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. The gnbs 106, 107, and 108 are base stations in a wireless network, and their service areas may or may not overlap with each other. In an embodiment, a User Equipment (UE) or mobile station 101 is located in a service area covered by the gnbs 106 and 107. As an example, the UE or mobile station 101 is located only in the service area of the gNB 106 and is connected with the gNB 106. The UE or mobile station 102 is located only in the service area of the gNB 107 and is connected to the gNB 107. gNB 106 is connected to gNB 107 through Xn interface 121. gNB 106 is connected to gNB 108 through Xn interface 122. 5G network entity 109 is connected to gnbs 106, 107, and 108 through NG connections 131, 132, and 133, respectively. In an embodiment, the UE 101 is configured to be capable of transmitting data in an inactive state without transitioning to a connected state.

In an embodiment, the UE initiates connectionless data transmission and/or reception in an inactive state. Connectionless data transfer does not establish an RRC connection. In one embodiment, the data transmission is a small data transmission as shown at 110. NR networks support many services with infrequent and small packets, such as traffic from instant messaging (instant messaging, IM) services, heartbeat/keep-alive (heart-beat/keep-alive) traffic from IM/email clients and other applications, and push notifications from various applications are typical use cases for smart phone applications. For non-smart phone applications, traffic from wearable devices, sensors, and smart meter/smart meter networks that send meter readings periodically are typical use cases. For these small data 110, data transmission and/or reception may be initiated in an inactive state without an RRC connection.

Fig. 1 further shows a simplified block schematic diagram of a base station and a mobile device/UE for connectionless data transmission and reception. Fig. 1 includes a simplified block diagram of a UE, such as UE 101. The UE has an antenna 165 to send and receive radio signals. An RF transceiver circuit 163 coupled to the antenna receives RF signals from the antenna 165, converts the RF signals to baseband signals, and sends the baseband signals to the processor 162. In one embodiment, the RF transceiver may include two RF modules (not shown). The first RF module is used for High Frequency (HF) transmission and reception, and the other RF module is used for transmission and reception of a different frequency band than the HF transceiver. The RF transceiver 163 also converts the baseband signal received from the processor 162 into an RF signal and transmits to the antenna 165. The processor 162 processes the received baseband signals and invokes different functional modules to perform the functional features in the UE 101. The memory 161 stores program instructions and data 164 to control the operation of the UE 101. The memory also stores UE inactive AS context including current KgNB and KRRCint keys, robust header compression (robust header compression, ROHC) status, stored QoS flow to dedicated radio bearer (dedicated radio bearer, DRB) mapping rules, cell radio network temporary identifiers (cell radio network temporary identifier, C-RNTI) used in the source PCell, cell and physical cell identifiers of the source PCell, and/or other parameters. In an embodiment, the UE inactive AS context further includes another set of parameters configured for data transmission in the inactive state, including configurations of a Physical (PHY) layer and a medium access control (media access control, MAC) layer. In an embodiment, the physical layer configuration includes pre-configured UL resources that may be used for UL data transmission in the inactive state. In an embodiment, the physical layer configuration includes a MAC configuration, such as a 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.

The UE 101 also includes a set of control modules for performing functional tasks. These functional modules may be implemented in circuitry, software, firmware, or a combination of the above. The state control module 191 initiates one or more data transmissions in the UE inactive state without RRC connection after determining one or more pre-configured transmission conditions in the wireless network. An Access Stratum (AS) context module 192 restores an inactive AS context (INACTIVE AS context) stored in the UE, wherein the inactive AS context includes an inactive data transmission configuration. The resource module 193 establishes UL resources for one or more data transmissions in the UE inactive state based on the inactive AS context. The transmission control module 194 performs one or more data transmissions in the UE inactive state using UL resources.

The control module may perform additional tasks to perform data transceiving in the inactive state. The data transmission 181 is performed at a packet data convergence protocol (packet data convergence protocol, PDCP) layer. The PDCP entity 188 and the radio link control (radio link control, RLC) entity 189 are configured for connectionless data transfer. The PDCP entity 188 is maintained in the UE inactive state without re-establishing for one or more data transmissions, wherein the PDCP entity maintains a PDCP Sequence Number (SN) and applies the same security key and security configuration in multiple data transmissions. In an embodiment, the PDCP layer supports data transmission, maintenance of PDCP SNs, header compression and decompression using ROHC protocol, ciphering and deciphering, integrity protection and verification, timer-based service data unit (service data unit, SDU) discard, routing of split bearers, repetition, reordering and in-order delivery, out-of-order delivery and repetition discard functions. In an embodiment, one PDCP entity of a DRB supporting data transmission in an inactive state maintains PDCP SNs and applies the same security keys and security configurations in a plurality of burst data transmissions in an inactive state. PDCP re-establishment is not performed when the UE performs data transmission in an inactive state. In an embodiment, the RLC entity state of the DRB is maintained and not re-established in a plurality of burst data transmissions in an inactive state, only upon a state transition between an inactive and a connected state.

According to an embodiment of the present invention, the UE may include a plurality of functional modules in the MAC layer to perform different tasks. A Random Access (RA) module 182 controls and performs random access, which may support a two-step RA procedure and a 4-step RA procedure. The configuration grant (configuration grant, CG) module 183 performs data transmission on the pre-configured PUSCH resources. A Time Alignment (TA) module 184 controls and performs UL time alignment procedures. The buffer status report (buffer status report, BSR) module 185 calculates the amount of data available for transmission in the layer 2 (L2) buffer and performs BSR. In one embodiment, the BSR module 185 controls scheduling request (scheduling request, SR) procedures. A hybrid automatic repeat request (Hybrid Automatic Repeat Request, HARQ) module 186 performs HARQ processes for one or more Transport Blocks (TBs). The multiplexing and assembling module 187 performs logical channel prioritization, multiplexes data from a plurality of logical channels, and generates a MAC Packet Data Unit (PDU).

Fig. 1 includes a simplified block diagram of a gNB, such as gNB 106. The gNB 106 has an antenna 156 that transmits and receives radio signals. RF transceiver circuitry 153 coupled to the antenna receives RF signals from antenna 156, converts the RF signals to baseband signals, and sends the baseband signals to processor 152. The RF transceiver 153 also converts baseband signals received from the processor 152 into RF signals and sends to the antenna 156. The processor 152 processes the received baseband signals and invokes different functional modules to perform the functional features in the gNB 106. Memory 151 stores program instructions and data 154 to control the operation of the gNB 106. The gNB 106 also includes a set of control modules 155 for performing functional tasks to communicate with the mobile station. 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 RRC state by sending a command to the UE or providing a conditional configuration. The DRB controller suspends or resumes the DRB of the UE. In one embodiment, the DRB is restored when a burst of data is to be transmitted. When the data burst transmission is completed, the DRB is suspended (suspended). The inactive AS context controller is operable to store, restore or release UE inactive AS contexts. The protocol controller is used to control the establishment, reestablishment, release, reset, and configuration of user plane protocols including PDCP, RLC, and MAC. In one embodiment, a service data adaptation protocol (service data adaptation protocol, SDAP) layer may be optionally configured. According to an embodiment of the invention, the gNB further comprises a plurality of functional modules in the MAC layer for performing different tasks. The RA module performs random access for the UE, which may support a two-step RA procedure and a 4-step RA procedure. The CG module receives data on preconfigured PUSCH resources. The TA module controls and performs UL time alignment procedures for the UE. The HARQ module performs HARQ processes for one or more TBs. The assistance information module may receive assistance information from the UE for scheduling. The demultiplexing and reassembly module demultiplexes and reassembles MAC PDUs received from the UE.

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of NR radio interface stacks according to an embodiment of the present invention. Different protocol split options are possible between the upper layer (upper layer) of the Central Unit (CU)/gNB node and the lower layer (lower layer) of the Distributed Unit (DU)/gNB node. The functional division between the central unit and the gNB lower layers may depend on the transport layer. The low performance transmission between the central unit and the gNB lower layers may enable the higher protocol layers of the NR radio stack to be supported in the central unit, since the higher protocol layers have lower performance requirements on the transmission layers in terms of bandwidth, delay, synchronization and jitter. In one embodiment, the SDAP and PDCP layers are located at a central unit, while the RLC, MAC and physical layers are located at a distributed unit. The core unit (core unit) 201 is connected to a central unit 211 with a gNB upper layer 252. In an embodiment, the gNB upper layer 252 includes a PDCP layer and an optional SDAP layer. The central unit 211 is connected to distributed units 221, 222, and 223, wherein the distributed units 221, 222, and 223 correspond to cells 231, 232, and 233, respectively. Distributed units 221, 222, and 223 include a gNB underlayer 251. In an 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 a PHY layer.

Fig. 3 is an exemplary top-level functional diagram for connectionless data transmission and reception with data pause (suspend) or stop and fall back (fallback) processes according to an embodiment of the present invention. In an embodiment, the UE performs one or more data transmissions of the data packet in the inactive state. In an embodiment, after determining one or more pre-configured transmission conditions in the wireless network, one or more data transmissions are initiated in a UE inactive state without RRC connection. In step 310, the ue determines whether one or more preconfigured transmission conditions (RRC-free conditions) are met. In an embodiment, the preconfigured transmission conditions include that the UE is in the current coverage area, the size of the transmitted data packet is smaller than a preconfigured small data threshold, and the network capability of the wireless network supports data transceiving without RRC connection. If step 310 determines no, the UE performs RRC-based data transmission 320. In one embodiment, the RRC-based transmission is UL CG-based process 321. In another embodiment, the RRC-based transmission is an RA-based process 322. If step 310 determines yes, the UE performs RRC-free (RRC-less) data transmission in the inactive state, i.e., data transmission without RRC connection. In step 301, the ue initiates a data transmission in an inactive state without RRC connection. In step 302, the ue performs one or more data transmissions and (optionally) receptions in an inactive state without RRC connection. The connectionless/RRC-free data transfer 330 may have a RRC CG-free based process 331 or an RRC RA-free based process 332. According to some embodiments of the present invention, for RRC-based and RRC-free data transmissions in an inactive state, the ue monitors one or more preconfigured backoff conditions and/or one or more suspension/stop conditions in step 350. If the UE detects one or more preconfigured suspension/stop conditions, the UE stops data transmission and remains in an inactive state in step 304. In an embodiment, the one or more pre-configured suspension/stop conditions include receiving a command from the wireless network indicating one or more DRBs to suspend, the L2 buffer being empty, receiving a stop indication from an upper layer of the UE, a data inactivity timer (datainactivity timer) expiring, the L2 buffer being empty not reaching a maximum number of new TB transmissions. If the UE detects one or more pre-configured backoff conditions, the UE rolls back to the process of recovering the RRC connection in step 305. In an embodiment, the one or more preconfigured backoff conditions include receiving a command from the wireless network to enter a connected state, a number of arriving consecutive data packets exceeding a preconfigured backoff threshold, receiving an indication from an upper layer of the UE to transition state to a connected state, the L2 buffer not being empty when the UE moves to another coverage area.

Fig. 4 is an exemplary flow chart for initiating data transmission in an inactive state without an RRC connection according to an embodiment of the present invention. In step 401, a UE in an inactive state receives system information. In an embodiment, the system information provides configuration for the UE to initiate small data transmissions in an inactive state. A threshold for the amount of data may be provided in the system information. In an embodiment, in step 402, a user plane of a ue receives a resume request of a NAS layer. In an embodiment, in step 403, if the access attempt is not prohibited, the UE performs unified access control and initiates data transmission. In an embodiment, the UE need not perform unified access control. Whether the UE can skip the unified access control or not can be configured by the network.

In step 410, the UE determines whether data can be transmitted without an RRC connection based on certain conditions, which may include: the UE is in the current coverage area, the amount of data is below a threshold, and the network is able to perform data transmission/reception without RRC connection in an inactive state. In an embodiment, the current coverage area is a set of cells including the current cell of the UE, where the current coverage area may be configured by the wireless network through a message such as system information or RRC signaling. Different coverage areas with different sets of cells may be configured by the network. When the UE stays in the same area, data transmission can be performed without RRC connection. When the UE moves out of the area into another area, the UE needs to resume the RRC connection for data transmission. The information of the region may be provided by system information or dedicated RRC signaling. In a particular case, if no such region is configured and the UE moves within the same cell (i.e., no cell reselection occurs), the UE may initiate the data transmission without an RRC connection. In another embodiment, the preconfigured small data thresholds and network capabilities may be configured by system information.

If step 410 determines that one or more RRC-free transmission conditions are met, the UE performs RRC-free data transmission in step 430. Otherwise, the UE moves to step 420 and initiates data transmission through RRC in the inactive state. In step 431, for no RRC transmission, the UE resumes the UE inactive AS context and applies the corresponding configuration. The above configuration may include security keys, ROHC status, stored QoS flow to DRB mapping rules, C-RNTI used in the source PCell, cell and physical cell identifiers of the source PCell, and/or other parameters configured for data transmission in the inactive state. In step 432, the ue resumes the DRB to be configured to be able to transmit data in the inactive state. The MAC layer multiplexes the logical channel DTCH carrying the DRBs with data for transmission in the inactive state.

Fig. 5 is an exemplary flowchart of performing a data transmission process in an inactive state according to an embodiment of the present invention. In an embodiment, the UE stays in an inactive state and enables HARQ, DRX, UL time alignment, BSR, and data inactivity monitoring. In step 501, the ue performs a TA procedure to obtain or maintain UL time alignment. If the TA timer expires, the UE needs to initiate an RA procedure to acquire the UL time alignment. In step 502, the ue performs a BSR procedure to send a BSR to the network. If there is no UL grant available, the UE will start the SR procedure. In step 503, the ue performs HARQ operations for one or more transmissions. In step 504, if the data transmission in the inactive state is configured with DRX, the UE enables and performs DRX. In step 505, if the data transmission in the inactive state configures a data inactivity timer, the UE performs data inactivity monitoring.

Fig. 6 is an exemplary flowchart of performing connectionless data transfer using an RA procedure in an inactive state, according to an embodiment of the present invention. In one embodiment, the data available for transmission in L2 is large and cannot be carried by Msg 3/MsgA. As shown at 610, the entire packet is split into different parts and carried by different TBs 611, 612 and 613. In step 601, the ue initiates an RA procedure. In step 602, the ue acquires a TA in a random access response (random access response, RAR). In step 603, the ue multiplexes BSR and UL data in one MAC PDU and stores the MAC PDU in the Msg3/MsgA buffer. In an embodiment, the UE multiplexes an RRC message (such as an RRC resume request (rrcreseumereqest)), an (optional) BSR, and (optional) data in a first UL transmission opportunity. In step 604, the ue performs contention resolution. If the contention is resolved, the ue sets the C-RNTI to a value of TEMPORARY C-RNTI (temp_c-RNTI) (4-step RA) or a value received in RAR success (success RAR) (two-step RA) in step 605. In step 606, the ue continues to listen to the PDCCH and performs data transmission/reception in an inactive state.

Fig. 7 is an exemplary flowchart of performing connectionless data transmission through pre-configured UL resources in an inactive state according to an embodiment of the present invention. In one embodiment, the data available for transmission in L2 is large and cannot be carried by Msg 3/MsgA. As shown at 610, the entire packet is split into different portions and carried by different TBs. In step 701, the ue multiplexes BSR and UL data in one MAC PDU. In an embodiment, the ue transmits a MAC PDU in a first UL transmission opportunity in step 702. In other words, the MAC PDU is transmitted in the first preconfigured UL resource. In an embodiment, the UL resources are CG resources pre-configured by the network. In another embodiment, the UE acquires UL resources through an RA procedure. In step 703, the ue continues to listen to the PDCCH and performs data transmission/reception in an inactive state. In an embodiment, the UE additionally provides a UE ID in each UL transmission. The MAC CE containing the UE ID is multiplexed with UL data. In an embodiment, the UE can only transmit data through the preconfigured UL resources if UL TA is valid (valid). In step 710, the ue determines whether UL TA is valid. If the UL is valid, the ue uses the preconfigured UL resources in step 711. In an embodiment, if the UL TA is not valid, the ue performs an RA procedure to acquire UL time alignment but reserves pre-configured UL resources in step 721. Thereafter, in step 711, the ue continues data transmission through the pre-configured UL resources (and resources dynamically scheduled by the network). In another embodiment, if step 710 determines that the TA is invalid, the ue releases the pre-configured UL resources and performs an RA procedure to acquire UL time alignment in step 722. Thereafter, the ue continues data transmission by monitoring a PDCCH corresponding to the C-RNTI (monitoring the C-RNTI on the PDCCH) in step 712.

Fig. 8 is an exemplary flowchart for stopping a connectionless data transfer process in an inactive state according to an embodiment of the present invention. In an embodiment, the UE stops data transmission in the inactive state upon detection of one or more preconfigured stop conditions 800. In step 811, the ue monitors a suspension/stop condition for suspending data transmission. When one of the suspension/stop conditions is satisfied, the ue suspends the DRB configured with data transmission in the inactive state and stops data transmission in step 812. In one embodiment, the suspension/stop is controlled by the network. The pause/stop condition 801 is the receipt of a command from the network. In an embodiment, the command is an RRC release (RRCRelease) message in response to an RRC resume request (RRCResumeRequest) previously sent by the UE. In another embodiment, suspension/stopping is controlled by the UE, and the conditions may be evaluated by the UE itself. For example, pause/stop condition 802 is that the L2 buffer is empty. In an embodiment, a threshold number N of new TB transmission opportunities may be configured. Another condition 803 is that datainactivatytimer expires, which means that the UE has some time without data for transmission/reception. Condition 804 is an indication received from an upper layer that there is no further uplink or downlink data transmission. Of course, there may be other conditions, such as the L2 buffer being empty before the new transmission opportunity is exhausted. In another embodiment, the ue triggers and transmits a BSR report with a value of "0" to the network in step 821. In an embodiment, the UE sends an indication to the network when one of the conditions evaluated by the UE is met, step 822. In an embodiment, the UE receives the RRCRelease message and remains in an inactive state.

Fig. 9 is an exemplary flowchart for backing off to an RRC recovery procedure and entering a connected state according to an embodiment of the present invention. The UE may configure one or more backoff conditions 900. In step 911, the ue monitors a backoff condition for recovering the RRC connection. When the condition is satisfied, the ue resumes the RRC connection and goes to the connected state for subsequent data transmission in step 912. In an embodiment, RRC connection recovery is controlled by the network. Condition 901 is the receipt of a command from the network. In an embodiment, the command is an RRC resume (rrcrume) message in response to a rrcrumerequest previously sent by the UE. In an embodiment, RRC connection recovery is controlled by the UE and conditions are evaluated by the UE itself. Condition 902 is that the amount of data arriving at the L2 buffer exceeds a preconfigured backoff threshold. Condition 903 is an indication to transition from the upper layer reception state to the connection state. Condition 904 is that the L2 buffer is not empty before the new transmission opportunity runs out. In an embodiment, when one or more preconfigured backoff conditions are met, the ue rolls back to the existing mechanism and initiates an RRC recovery procedure by sending an rrcresmerequest message in step 931.

Fig. 10 is an exemplary flow chart of connectionless data transfer in an inactive state according to an embodiment of the invention. In step 1001, the UE initiates one or more data transmissions in a UE inactive state without RRC connection after determining one or more pre-configured transmission conditions in the wireless network. In step 1002, the UE restores an inactive AS context stored in the UE, wherein the inactive AS context includes an inactive data transmission configuration. In step 1003, the UE establishes UL resources for one or more data transmissions in the UE inactive state based on the inactive AS context. In step 1004, the UE performs one or more data transmissions using UL resources in a UE inactive state.

In one embodiment, a storage medium (e.g., a computer-readable storage medium) stores a program that, when executed, causes a UE to perform embodiments of the present invention.

Although the invention has been described in connection with specific embodiments for purposes of illustration, the invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims

1. A connectionless data transfer method in an inactive state, comprising:

initiating, by the user equipment, one or more data transmissions in an inactive state of the user equipment without radio resource control connection, RRC, after determining one or more pre-configured transmission conditions in the wireless network;

recovering an inactive access layer context stored in the user equipment, wherein the inactive access layer context comprises an inactive data transmission configuration comprising a physical layer configuration and a medium access control layer configuration;

establishing uplink resources for one or more data transmissions in an inactive state of the user equipment based on the inactive access layer context; and

the one or more data transmissions are performed using the uplink resources in the user equipment inactive state.

2. The connectionless data transfer method of claim 1, wherein the one or more preconfigured transfer conditions comprise: the user equipment is in the current coverage area, the size of the transmitted data packet is smaller than a pre-configured small data threshold value, and the network capability of the wireless network supports data receiving and transmitting without RRC connection.

3. The connectionless data transfer method according to claim 2, wherein the current coverage area is a set of cells including a current cell of the user equipment and the current coverage area is configured by the wireless network through system information or RRC signaling messages.

4. The connectionless data transfer method according to claim 2, wherein the pre-configured small data threshold and the network capabilities of the wireless network are configured by system information.

5. The connectionless data transfer method according to claim 1, wherein the uplink resource is a network pre-configured configuration grant resource.

6. The connectionless data transfer method according to claim 5, wherein the time alignment of the uplink resources is efficient.

7. The connectionless data transfer method according to claim 5, wherein if the time alignment of the uplink resources is invalid, the user equipment performs a random access procedure to acquire the uplink time alignment.

8. The connectionless data transfer method according to claim 7, wherein the pre-configured configuration grant resources are released and the user equipment continues the one or more data transfers by monitoring a physical downlink control channel with a cell radio network temporary identifier.

9. The connectionless data transfer method according to claim 7, wherein after the uplink time alignment is acquired, the user equipment continues the one or more data transfers via the preconfigured grant resources.

10. The connectionless data transmission method according to claim 1, wherein the user equipment acquires the uplink resources through a random access procedure and acquires time alignment in a random access response.

11. The connectionless data transfer method according to claim 1, further comprising:

monitoring one or more preconfigured pause/stop conditions, and one or more preconfigured fallback conditions;

stopping the one or more data transmissions in the user equipment inactive state upon detection of the one or more preconfigured pause/stop conditions; and

upon detecting the one or more preconfigured fallback conditions, a state change from the user equipment inactive state to a user equipment connected state is performed.

12. The connectionless data transfer method of claim 11, wherein the one or more preconfigured backoff conditions comprise: receiving a command from the wireless network to enter the user equipment connection state, the number of arriving consecutive data packets exceeding a pre-configured backoff threshold, receiving an indication from an upper layer of the user equipment that state transitions to the user equipment connection state, the layer 2 buffer not being empty when the user equipment moves to another coverage area.

13. The connectionless data transfer method according to claim 1, characterized in that a packet data convergence protocol entity is maintained in the user equipment inactive state without re-establishing for the one or more data transfers, wherein the packet data convergence protocol entity maintains a packet data convergence protocol sequence number and applies the same security key and security configuration in multiple data transfers.

14. A user equipment, comprising:

a transceiver for transmitting and receiving wireless signals in a wireless network;

a state control module for initiating one or more data transmissions in an inactive state of a user equipment without radio resource control connection, RRC, after determining one or more pre-configured transmission conditions in the wireless network;

an access stratum context module for recovering an inactive access stratum context stored in the user equipment, wherein the inactive access stratum context comprises an inactive data transmission configuration, and the inactive data transmission configuration comprises a physical layer configuration and a medium access control layer configuration;

a resource module to establish uplink resources for one or more data transmissions in an inactive state of the user equipment based on the inactive access layer context; and

a transmission control module to perform the one or more data transmissions using the uplink resources in the user equipment inactive state.

15. The user equipment of claim 14, wherein the one or more preconfigured transmission conditions comprise: the user equipment is in the current coverage area, the size of the transmitted data packet is smaller than a pre-configured small data threshold value, and the network capability of the wireless network supports data receiving and transmitting without RRC connection.

16. The user equipment of claim 15, wherein the current coverage area is a set of cells including a current cell of the user equipment, and wherein the current coverage area is configured by the wireless network via system information or RRC signaling messages.

17. The user equipment of claim 15, wherein the pre-configured small data threshold and network capabilities of the wireless network are configured by system information.

18. The user equipment of claim 14, wherein the uplink resource is a network pre-configured configuration grant resource.

19. The user equipment of claim 18, wherein if the time alignment of the uplink resources is invalid, the user equipment performs a random access procedure to obtain the uplink time alignment.

20. A storage medium storing a program which, when executed, causes a user equipment to perform the steps of the connectionless data transfer method in an inactive state of any one of claims 1-13.