CN114071804A

CN114071804A - Connectionless data transmission method in non-active state and user equipment

Info

Publication number: CN114071804A
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: 2022-02-18
Anticipated expiration: 2041-07-26
Also published as: CN114071804B; WO2022021278A1

Abstract

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

Description

Connectionless data transmission method in non-active state and user equipment

Technical Field

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

Background

The 5G radio access technology will become a key component of modern access networks, which will address the growing high traffic growth, energy efficiency and the growing demand for high bandwidth connections. It will also support massive connection devices, meeting the real-time, high reliability communication requirements of mission-critical applications. The 5G network introduces Radio Resource Control (RRC) inactive (inactive) states to reduce control plane and user plane latency. In the RRC inactive state, the UE is always connected to a Core Network (CN), and thus a transition from the inactive state to a connected (connected) state is more efficient than a transition from an idle (idle) state to a connected state. However, for any Downlink (DL) and Uplink (UL) data, the UE needs to first transition from the inactive state to the connected state and complete the connection recovery process, and the data is transmitted and received in the connected state, and each data transmission is performed with connection establishment and subsequent release to the inactive state. The transition involves a large number of signaling sequences between the UE and the network. The high power consumption required to handle all the signaling involved in a traditional inactive state to connected state transition is not justified when the amount of data that the wireless device exchanges with the network is small and often not urgent enough.

In view of the above, 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 method for connectionless data transmission in an inactive state, including: initiating, by a user equipment, one or more data transmissions in a user equipment inactive state without radio resource control connection, RRC, after determining one or more preconfigured transmission conditions in a wireless network; restoring an inactive access stratum context stored in the user equipment, wherein the inactive access stratum context comprises an inactive data transmission configuration; establishing uplink resources for one or more data transmissions in the user equipment inactive state based on the inactive access stratum 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 to transmit and receive 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 preconfigured transmission conditions in the wireless network; an access stratum context module to recover 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 the user equipment inactive state based on the inactive access stratum 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, which when executed, causes a ue to perform the method for connectionless data transmission in an inactive state according to the present invention.

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

Drawings

The drawings illustrate embodiments of the invention, in which like numerals refer to like elements.

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

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of the NR radio interface stack in accordance with 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 stalling and rollback procedures, according to an embodiment of the present invention.

Fig. 4 is an exemplary flow diagram 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 a process of performing data transfer in an inactive state according to an embodiment of the present invention.

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

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

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

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

Fig. 10 is an exemplary flow diagram of connectionless data transmission in an inactive state according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to some embodiments of the 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 5G technology or other radio access technologies. NRs, etc. may support various wireless communication services such as enhanced mobile broadband for wide bandwidths, millimeter waves for high carrier frequencies, massive MTC for non-backward compatible Machine Type Communication (MTC) technologies, and/or mission critical for ultra-reliable low latency communication. These services may have delay and reliability requirements. These services may also have different Transmission Time Intervals (TTIs) to meet respective 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 present invention. The wireless system 100 includes one or more fixed infrastructure elements that form a network distributed over a geographic area. The infrastructure elements 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 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), such as within a cell or a sector of a cell. In some systems, one or more base stations are coupled to a controller, forming an access network coupled to one or more core networks, the access network being coupled to the one or more core networks. gNB 106, gNB 107, and gNB 108 are base stations in a wireless network whose service areas may or may not overlap with each other. In an embodiment, a User Equipment (UE) or mobile station 101 is located in the service area covered by gNB 106 and gNB 107. As an example, UE or mobile station 101 is located only in the service area of gNB 106 and is connected to gNB 106. UE or mobile station 102 is located only in the service area of gNB 107 and is connected to gNB 107. The gNB 106 is connected to the gNB 107 via an Xn interface 121. The gNB 106 is connected to the gNB 108 through an Xn interface 122. The 5G network entity 109 is connected to the gnbs 106, 107 and 108 via

NG connections

131, 132 and 133, respectively. In an embodiment, the UE 101 is configured to be able to transmit data in an inactive state without transitioning to a connected state.

In an embodiment, the UE initiates connectionless data transmission and/or reception in the inactive state. Connectionless data transmission does not establish an RRC connection. In one embodiment, the data transfer is a small data transfer as shown at 110. NR networks support many services with infrequent and small packets, such as services from Instant Messaging (IM) services, heartbeat/keep-alive (heart-beat/keep-alive) services from IM/email clients and other applications, and push notifications from various applications are typical use cases for smartphone applications. For non-smartphone applications, traffic from wearable devices, sensors, and smart meter/smart meter networks that periodically send meter readings is a typical use case. 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 for transmitting and receiving radio signals. The RF transceiver circuit 163, which is 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). A first RF module is used for High Frequency (HF) transmission and reception, and another RF module is used for transmission and reception of a different frequency band than the HF transceiver. The RF transceiver 163 also converts a 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 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 (ROHC) state, stored QoS flow to Dedicated Radio Bearer (DRB) mapping rules, cell radio network temporary identifier (C-RNTI) used in the source PCell, cell identifier and physical cell identifier 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 (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 comprises 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 blocks may be implemented by circuitry, software, firmware, or a combination thereof. 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 stored in the UE (INACTIVE AS context), wherein the inactive AS context includes an inactive data transfer 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 the UL resources.

The control module may perform additional tasks to perform data transceiving in the inactive state. Data transmission 181 is performed at a Packet Data Convergence Protocol (PDCP) layer. The PDCP entity 188 and a Radio Link Control (RLC) entity 189 are configured for connectionless data transmission. The PDCP entity 188 is maintained in the UE inactive state without re-establishment 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 over multiple data transmissions. In one embodiment, the PDCP layer supports functions such as data transmission, maintenance of PDCP SNs, header compression and decompression using ROHC protocol, ciphering and deciphering, integrity protection and integrity verification, timer-based Service Data Unit (SDU) discard, bearer routing separation, duplication, reordering and in-order delivery, out-of-order transmission, and duplicate discard. In an embodiment, one PDCP entity of a DRB supporting data transmission in an inactive state maintains a PDCP SN and applies the same security key and security configuration in multiple burst data transmissions in the inactive state. When the UE performs data transmission in an inactive state, PDCP re-establishment is not performed. In an embodiment, the RLC entity state of the DRB is maintained and not re-established over multiple burst data transmissions in an inactive state, and is re-established only when a state transition occurs between the inactive and connected states.

According to an embodiment of the present invention, the UE may include a plurality of functional modules performing different tasks in the MAC layer. 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. A Configuration Grant (CG) module 183 performs data transmission on the preconfigured PUSCH resource. A Time Alignment (TA) module 184 controls and executes the UL time alignment procedure. 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 (SR) processes. A 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 multiple logical channels, and generates MAC Packet Data Units (PDUs).

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 a baseband signal received from the processor 152 into an RF signal and transmits to the antenna 156. Processor 152 processes the received baseband signals and invokes different functional blocks to perform functional features in the gNB 106. Memory 151 stores program instructions and data 154 to control the operation of gNB 106. The gNB 106 also includes a set of control modules 155 for performing functional tasks for communicating 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 RRC state by sending commands to the UE or providing conditional configuration. The DRB controller suspends or resumes DRBs of the UE. In an embodiment, the DRB is recovered when a data burst is to be transmitted. When the data burst transmission is completed, the DRB is suspended (suspended). The inactive AS context controller is used to store, restore or release UE inactive AS context. The protocol controller is used for controlling the establishment, reconstruction, release, reset and configuration of the user plane protocol including PDCP, RLC and MAC. In an embodiment, a Service Data Adaptation Protocol (SDAP) layer may be optionally configured. According to an embodiment of the present 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 a UL time alignment procedure for the UE. The HARQ module performs a HARQ process for one or more TBs. The assistance information module may receive assistance information from the UE for scheduling. The demultiplexing and de-assembling module demultiplexes and de-assembles the MAC PDU received from the UE.

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of the NR radio interface stack in accordance with an embodiment of the present invention. Different protocol partitioning options are possible between the upper layer of the Central Unit (CU)/gNB node and the lower layer of the Distributed Unit (DU)/gNB node. The functional division between the central unit and the lower layers of the gbb may depend on the transport layer. Since higher protocol layers have lower performance requirements on the transport layer in terms of bandwidth, delay, synchronization and jitter, low performance transmission between the central unit and the lower layers of the gbb may enable the high 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 a central unit, while the RLC, MAC layers, and physical layers are located in a distributed unit. A core unit (core unit)201 is connected to a central unit 211 having a gNB upper layer 252. In an embodiment, the gbb upper layers 252 include a PDCP layer and an optional SDAP layer. Central unit 211 is connected to distributed

units

221, 222, and 223, where distributed

units

221, 222, and 223 correspond to

cells

231, 232, and 233, respectively. Distributed

units

221, 222, and 223 include a gbb lower layer 251. In an embodiment, the gbb lower layer 251 includes PHY, MAC, and RLC layers. In another embodiment 260, each gNB has a protocol stack 261 that includes SDAP, PDCP, RLC, MAC, and PHY layers.

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

Fig. 4 is an exemplary flow diagram 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 the inactive state. A threshold for the amount of data may be provided in the system information. In an embodiment, in step 402, the user plane of the UE receives a NAS layer recovery request. In an embodiment, in step 403, if the access attempt is not barred, the UE performs unified access control and initiates data transmission. In an embodiment, the UE does not need to perform unified access control. Whether the UE can skip the unified access control may be configurable by the network.

In step 410, the UE determines whether data can be transmitted without 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 transmit/receive data without RRC connection in the inactive state. In an embodiment, the current coverage area is a set of cells including a current cell of the UE, wherein the current coverage area is configurable by the wireless network through messages 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 may 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 one particular case, if such an area is not configured and the UE moves within the same cell (i.e., no cell reselection occurs), the UE may initiate data transmission without an RRC connection. In another embodiment, the preconfigured small data threshold and the network capability may be configured by system information.

If it is determined in step 410 that one or more RRC-free transmission conditions are satisfied, 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 restores the UE inactive AS context and applies the corresponding configuration. The configuration may include security keys, ROHC status, stored QoS flow to DRB mapping rules, C-RNTI used in the source PCell, cell identifier and physical cell identifier 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 a logical channel DTCH carrying DRBs, which have data to be transmitted in the inactive state.

Fig. 5 is an exemplary flowchart of a process of performing data transfer 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 times out, the UE needs to initiate an RA procedure to acquire UL time alignment. In step 502, the UE performs a BSR procedure to transmit a BSR to the network. If no UL grant is available, the UE will initiate the SR procedure. In step 503, the UE performs a HARQ operation for one or more transmissions. In step 504, if DRX is configured for data transmission in the inactive state, the UE enables and performs DRX. In step 505, the UE performs data inactivity monitoring if the data inactivity timer is configured for data transmission in the inactive state.

Fig. 6 is an exemplary flowchart of performing connectionless data transmission using an RA process 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. Step 602, the UE acquires the TA in a 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 recovery request (RRCResumeReqest)), an (optional) BSR, and (optional) data in the 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 a TEMPORARY C-RNTI (TEMPORARY _ 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 monitor the PDCCH and perform data transmission/reception in the inactive state.

Fig. 7 is an exemplary flowchart of performing connectionless data transmission through preconfigured 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. The entire packet is split into different parts and carried by different TBs as shown at 610. In step 701, the UE multiplexes BSR and UL data in one MAC PDU. In an embodiment, in step 702, the UE transmits a MAC PDU in a first UL transmission opportunity. In other words, the MAC PDU is transmitted in the first pre-configured UL resource. In an embodiment, the UL resources are network pre-configured CG resources. In another embodiment, the UE acquires UL resources through a RA procedure. In step 703, the UE continues to monitor the PDCCH and perform data transmission/reception in the 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 pre-configured UL resource if the UL TA is valid (valid). In step 710, the UE determines whether the UL TA is valid. If the UL is valid, the UE uses the pre-configured UL resource in step 711. In an embodiment, if UL TA is not valid, the UE performs a RA procedure to acquire UL time alignment, but retains pre-configured UL resources in step 721. Thereafter, in step 711, the UE continues data transmission through the preconfigured UL resources (and the resources dynamically scheduled by the network). In another embodiment, if step 710 determines that the TA is not valid, the UE releases the pre-configured UL resources and performs a RA procedure to acquire UL time alignment in step 722. Thereafter, the UE continues data transmission by monitoring the PDCCH corresponding to the C-RNTI (C-RNTI is monitored on the PDCCH) in step 712.

Fig. 8 is an exemplary flowchart of a process of stopping connectionless data transfer 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 detecting one or more preconfigured stop conditions 800. In step 811, the UE monitors a suspend/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 pause/stop is controlled by the network. Pause/stop condition 801 is the receipt of a command from the network. In an embodiment, the command is an RRC release (rrcreelease) message in response to an RRC recovery request (RRCResumeRequest) previously sent by the UE. In another embodiment, the suspension/stop is controlled by the UE, and the conditions may be evaluated by the UE itself. For example, the 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 the datainactivity timer expires, which means that the UE has a period of time without data for transmission/reception. Conditional 804 is receiving an indication 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, in step 821, the UE triggers and sends a BSR report with a value of "0" to the network. In an embodiment, in step 822, the UE sends an indication to the network when one of the conditions evaluated by the UE is satisfied. In an embodiment, the UE receives the rrcreelease message and remains in the inactive state.

Fig. 9 is an exemplary flowchart of fallback 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 fallback conditions 900. In step 911, the UE monitors a fallback condition to resume the RRC connection. When the conditions are 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. Conditional 901 is that a command is received from the network. In an embodiment, the command is an RRC recovery (RRCResume) message in response to a RRCResumeRequest previously sent by the UE. In an embodiment, RRC connection recovery is controlled by the UE and the conditions are evaluated by the UE itself. Conditional 902 is that an amount of data arriving at the L2 buffer exceeds a preconfigured backoff threshold. Conditional 903 is an indication to transition from the upper layer reception state to the connection state. Conditional 904 is that the L2 buffer is not empty before the new transmission opportunity runs out. In an embodiment, when one or more preconfigured fallback conditions are met, the UE reverts back to the existing mechanism and initiates the RRC recovery procedure by sending an RRCResumeRequest message in step 931.

Fig. 10 is an exemplary flow diagram of connectionless data transmission in an inactive state according to an embodiment of the present invention. In step 1001, the UE initiates one or more data transmissions in the UE inactive state without RRC connection after determining one or more preconfigured 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 the 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 various embodiments of the present invention.

Although the present invention has been described in connection with the specified embodiments for the purpose of illustration, the present 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 transmission method in an inactive state, comprising:

initiating, by a user equipment, one or more data transmissions in a user equipment inactive state without radio resource control connection, RRC, after determining one or more preconfigured transmission conditions in a wireless network;

restoring an inactive access stratum context stored in the user equipment, wherein the inactive access stratum context comprises an inactive data transmission configuration;

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

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

2. The connectionless data transmission method in an inactive state according to claim 1, wherein the inactive data transmission configuration comprises a physical layer configuration and a medium access control layer configuration.

3. The method of claim 1, wherein the one or more preconfigured transmission conditions comprise: the user equipment transmits a data packet with a size smaller than a pre-configured small data threshold in the current coverage area, and the network capability of the wireless network supports data transceiving without RRC connection.

4. The method of claim 3, wherein the current coverage area is a set of cells including a current cell of the UE, and wherein the current coverage area is configured by the wireless network through system information or RRC signaling messages.

5. The method of claim 3, wherein the preconfigured small data threshold and the network capability of the wireless network are configured by system information.

6. The method of claim 1, wherein the uplink resource is a network pre-configured configuration grant resource.

7. The method of claim 6, wherein the time alignment of the uplink resources is valid.

8. The method of claim 6, wherein if the time alignment of the uplink resource is invalid, the UE performs a random access procedure to obtain uplink time alignment.

9. The method of claim 8, wherein the preconfigured configuration grant resources are released and the UE continues the one or more data transmissions by monitoring a physical downlink control channel with a cell radio network temporary identifier.

10. The method of claim 8, wherein after obtaining the uplink time alignment, the UE continues the one or more data transmissions via the preconfigured configuration grant resources.

11. The method of claim 1, wherein the UE acquires the uplink resource through a random access procedure and acquires time alignment in a random access response.

12. The method of claim 1, further comprising:

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

upon detecting the one or more preconfigured suspend/stop conditions, stopping the one or more data transmissions in the user equipment inactive state; and

performing a state change from the user equipment inactive state to a user equipment connected state upon detection of the one or more preconfigured fallback conditions.

13. The method of claim 12, wherein the one or more preconfigured fallback conditions comprise: receiving a command from the wireless network to enter the user equipment connected state, the number of consecutive data packets arriving exceeding a preconfigured fallback threshold, receiving an indication from an upper layer of the user equipment to transition state to the user equipment connected state, a layer 2 buffer not being empty when the user equipment moves to another coverage area.

14. The method of claim 1, wherein a packet data convergence protocol entity is maintained in the inactive state of the UE without re-establishing for the one or more data transmissions, wherein the packet data convergence protocol entity maintains a packet data convergence protocol sequence number and applies the same security key and security configuration for the plurality of data transmissions.

15. A user device, comprising:

a transceiver to transmit and receive 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 preconfigured transmission conditions in the wireless network;

an access stratum context module to recover 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 the user equipment inactive state based on the inactive access stratum context; and

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

16. The UE of claim 15, wherein the one or more preconfigured transmission conditions comprise: the user equipment transmits a data packet with a size smaller than a pre-configured small data threshold in the current coverage area, and the network capability of the wireless network supports data transceiving without RRC connection.

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

18. The UE of claim 16, wherein the preconfigured small data threshold and network capabilities of the wireless network are configured via system information.

19. The UE of claim 15, wherein the uplink resource is a network pre-configured configuration grant resource.

20. The UE of claim 19, wherein if the time alignment of the uplink resource is invalid, the UE performs a random access procedure to obtain uplink time alignment.

21. A storage medium storing a program which, when executed, causes a user equipment to perform the steps of the method for connectionless data transmission in an inactive state as claimed in any one of claims 1 to 14.