WO2022021278A1

WO2022021278A1 - Apparatus and methods for data transfer in connectionless way

Info

Publication number: WO2022021278A1
Application number: PCT/CN2020/106088
Authority: WO
Inventors: Yuanyuan Zhang; Chia-Chun Hsu
Original assignee: Mediatek Singapore Pte. Ltd.
Priority date: 2020-07-31
Filing date: 2020-07-31
Publication date: 2022-02-03
Also published as: CN114071804B; CN114071804A

Abstract

Apparatus and methods are provided to support data transmission in INACTIVE state in NR system. In one novel aspect, UE is configured with Inactive data transmission configuration, which contains at least physical layer configuration and MAC configuration. UE initiates data transmission without RRC connection in INACTIVE when a request is received from upper layer, restores UE INACTIVE AS CONTEXT, resumes one or multiple DRBs which require data transmission in INACTIVE state and performing one or multiple shots data transmission/reception for those DRBs.

Description

APPARATUS AND METHODS FOR DATA TRANSFER IN CONNECTIONLESS WAY

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communication, and, more particularly, to transmit and receive small and infrequent data traffic in a connectionless way without RRC connection in the new radio access system.

BACKGROUND

5G radio access technology will be a key component of the modern access network. It introduced RRC INACTIVE state in Rel-15 to reduce both control plane and user plane latency. In RRC Inactive state, the UE Access Stratum (AS) context, e.g. AS security context is stored in the UE and the RAN. The UE is always connected from the CN aspect. Therefore, the state transition from Inactive to Connected state can be achieved in a light signaling procedure. The signaling overhead can be reduced significantly, especially for UEs with services of frequent and small packets. The transfer of unicast data to/from the UE can only be performed in CONNECTED.

In Rel-15, UE should perform state transition from INACTIVE to CONNECTED state and complete connection resume procedures first for any DL and UL data. Connection setup and subsequently release to INACTIVE state happens for each data transmission. The transition comprises extensive signaling sequence between the UE and the network.

NR supports many services with infrequent and small data packets. For example, traffic from Instant Messaging services (WhatsApp, QQ, WeChat, etc. ) , heart-beat/keep-alive traffic from IM/email clients and other apps and push notifications from various applications are the typical use cases of smart phone applications. For non-smartphone applications, traffic from wearables, sensors and smart meters /smart meter networks sending periodic meter readings are the typical use cases. The amount of data that wireless devices typically exchange with the network is small and usually not urgent enough to justify the high battery consumption required to handle all the signaling involved in the legacy INACTIVE-to-CONNECTED transition.

When the UE is stationary or with limited mobility status, there is no much change in radio channel condition and resource reconfiguration as well as security update is not necessary required. In this case, UE can perform data transfer without RRC connection establishment, which can further reduce the RRC signaling overhead and RRC processing for state transition.

To address this issue, apparatus and mechanisms are sought to reduce signaling overhead and power consumption for the services with infrequent and small data packets in this invention.

SUMMARY

Apparatus and methods are provided to support data transmission in INACTIVE to reduce signaling overhead and power consumption for the services with infrequent and small data packets in NR system. In one novel aspect, the UE INACTIVE AS CONTEXT has a set of parameters configured for data transmission in INACTIVE, which at least includes the configurations for physical layer and MAC layer. In one embodiment, one or multiple particular DRBs are configured by network, whose data packets can be transmitted in INACTIVE. In one embodiment, the DRB is resumed when a burst of data is to be transmitted; the DRB is suspended when the transmission of data burst is finished. In one embodiment, one PDCP entity of the DRB supporting data transmission in INACTIVE maintains the PDCP SN among the multiple bursts data transmission in INACTIVE state. PDCP re-establishment is not performed when UE stays in INACTIVE state performing data transmission.

UE initiates data transmission in INACTIVE. UE does not need to resume RRC connection and go to CONNECTED state for data transmission. After the procedure initiation, UE performs data transfer in INACTIVE. If transmission of all the data in the buffer is completed, UE stops the data transmission and stays in INACTIVE state. If more data arrives, receives a command or UE moves out of an area, UE falls back to the procedure to resume RRC connection.

In one novel aspect, UE stays in INACTIVE and enables HARQ, DRX, UL time alignment, BSR and data inactivity monitoring. UE performs TA alignment procedure to obtain or maintain the UL time alignment.

In one embodiment, the user plane of the UE receives the resume requested by NAS layer. In one embodiment, UE performs unified access control and initiate data transmission if the access attempt is not barred. Then UE checks whether it can transmit data direction without RRC connection based on certain conditions, which include:

● UE stays in the coverage of an area;

● The data amount is below a threshold;

● The network is capable of data transmission/reception without RRC connection in INACTIVE;

In one embodiment, the different areas with different sets of cells are configured by the network. UE can performs data transmission without RRC connections when it stays in the same area. When UE moves out of the area and goes in to another area, UE needs to resume RRC connection to perform data transmission.

UE monitors the suspension conditions to suspend data transmission. When one of the suspension condition is met, UE suspends the DRBs configured with data transmission in INACTIVE and stops data transmission:

● a command is received from the network;

● the L2 buffer is empty;

● the DataInactivityTimer expires;

● an indication is received from the upper layering, indicating that there is no further uplink or downlink data transmission and no further uplink data transmission subsequent to the uplink data transmission is expected.

UE monitors the fallback conditions to resume RRC. When the condition is met, UE resumes RRC connection and go to CONNECTED for further data transmission. The fall-back conditions includes:

● receiving a command from network to go to CONNECTED;

● More data arrives;

● An indication is received from the upper layer;

● L2 buffer is not empty and UE moves to another area.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 1 is a schematic system diagram illustrating an exemplary wireless network in accordance with embodiments of the current invention.

Fig. 2 illustrates an exemplary NR wireless system with centralization of the upper layers of the NR radio stacks in accordance with embodiments of the current invention.

Fig. 3 illustrates an exemplary flowchart to perform data transmission without RRC Connection in INACTIVE in accordance with embodiments of the current invention.

Fig. 4 illustrates an exemplary flowchart to initiate data transmission without RRC connection in INACTIVE in accordance with embodiments of the current invention.

Fig. 5 illustrates an exemplary flowchart to transmit data in INACTIVE in accordance with embodiments of the current invention.

Fig. 6 illustrates an exemplary flowchart to transmit data without RRC connection through RA procedure in INACTIVE in accordance with embodiments of the current invention.

Fig. 7 illustrates an exemplary flowchart to transmit data without RRC connection through pre-configured UL resources in INACTIVE in accordance with embodiments of the current invention.

Fig. 8 illustrates an exemplary flowchart to stop data transmission INACTIVE in accordance with embodiments of the current invention.

Fig. 9 illustrates an exemplary flowchart to fall back to resume RRC connection in accordance with embodiments of the current 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.

Fig. 1 is a schematic system diagram illustrating an exemplary wireless network in accordance with embodiments of the current invention. Wireless system includes one or more fixed base infrastructure units forming a network distributed over a geographical region. The base unit may also be referred to as an access point, an access terminal, a base station, a Node-B, an eNode-B, a gNB, or by other terminology used in the art. As an example, base stations serve a number of mobile stations within a serving area, for example, a cell, or within a cell sector. In some systems, one or more base stations are coupled to a controller forming an access network that is coupled to one or more core networks. gNB 1and gNB 2 are base stations in NR, the serving area of which may or may not overlap with each other. As an example, UE1 or mobile station is only in the service area of gNB 1 and connected with gNB1. UE2 or mobile station is only in the service area of gNB 2 and connected with gNB2. gNB1 is connected with gNB 102 via Xn interface. In one embodiment, UE 2 is configured to be able to transmit data in INACTIVE without the transition to CONNECTED state.

Fig. 1 further illustrates simplified block diagrams for UE2 and gNB2, respectively. UE has an antenna, which transmits and receives radio signals. A RF transceiver, coupled with the antenna, receives RF signals from antenna, converts them to baseband signal, and sends them to processor. In one embodiment, the RF transceiver may comprise two RF modules (not shown) . A first RF module is used for transmitting and receiving on one frequency band, and the other RF module is used for different frequency bands transmitting and receiving which is different from the first transmitting and receiving. RF transceiver also converts received baseband signals from processor, converts them to RF signals, and sends out to antenna. Processor processes the received baseband signals and invokes different functional modules to perform features in UE. Memory stores program instructions and data to control the operations of mobile station. The Memory also stores UE INACTIVE AS CONTEXT, which includes the current KgNB and KRRCint keys, the ROHC state, the stored QoS flow to DRB mapping rules, the C-RNTI used in the source PCell, the cell Identity and the physical cell identity of the source PCell, and all other parameters. In one embodiment, the UE INACTIVE AS CONTEXT also has another set of parameters configured for data transmission in INACTIVE, which includes the configurations for physical layer and MAC layer. In one embodiment, the physical layer configuration includes pre-configured UL resources, which can be used for UL data transmission in INACTIVE. In one embodiment, the physical layer configuration includes MAC configuration, e.g. MAC-Cell Group Config. UE also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention.

A RRC State controller, which controls UE RRC state according to network’s command and UE conditions. RRC supports the following states, RRC_IDLE, RRC_CONNECTED and RRC_INACTIVE. In one embodiment, UE is configured to transmit UL data in INACTIVE with one ore multiple shots to network without RRC connection resume/establishment when one or more conditions are met. One condition is that the total data amount arrives for the one or more DRBs in the buffer is less than a threshold. One condition is that UE resumes in the same set of cells configured by the network. In one embodiment, the network configures the threshold of data amount through system information or dedicated RRC signaling. A DRB controller, which suspends or resumes the DRBs. In one embodiment, one or multiple particular DRBs are configured by network, whose data packets can be transmitted in INACTIVE. In one embodiment, the DRB is resumed when a burst of data is to be transmitted; the DRB is suspended when the transmission of data burst is finished. An INACTIVE AS CONTEXT controller, which manage to store, restore or release the UE INACTIVE AS CONTEXT. In one embodiment, the UE INACTIVE AS CONTEXT controller decides which parameters or which set of parameters are restored according to whether UE initiate data transmission or not in INACTIVE. In one embodiment, UE restores all the stored parameters including MAC configuration and physical layer configuration. A protocol controller, which controls the establishment, re-establishment, release, reset, reconfiguration of the user plane protocols including PDCP, RLC and MAC. In one embodiment, the SDAP layer is optionally configured.

In one embodiment, the PDCP layer supports the functions of transfer of data, maintenance of PDCP SN, header compression and decompression using the ROHC protocol, ciphering and deciphering, integrity protection and integrity verification, timer based SDU discard, routing for split bearer, duplication, re-ordering and in-order delivery; out of order delivery and duplication discarding. In one embodiment, one PDCP entity of the DRB supporting data transmission in INACTIVE maintains the PDCP SN and applies the same security keys and security configuration among the multiple bursts data transmission in INACTIVE state. PDCP re-establishment is not performed when UE stays in INACTIVE state performing data transmission. In one embodiment, the state of the RLC entity of the DRB is maintained and not re-established among the multiple bursts data transmission in INACTIVE state. It is re-established only when state transition between INACTIVE and CONNECTED occurs.

UE also includes multiple function modules in MAC layer that carry out different tasks in accordance with embodiments of the current invention. Random access (RA) module, which controls and performs random access. It supports 2-step RA procedure and 4-step RA procedure. Configured Grant (CG) module, which performs data transmission on the pre-configured PUSCH resources. Time alignment (TA) module, which controls and performs the UL time alignment procedure. HARQ module, which performs HARQ process for one or multiple TBs. Buffer Status Report (BSR) , which calculate the data amount available for transmission in L2 buffer and performs BSR. In one embodiment, it also controls the scheduling request (SR) procedure. Multiplex and assembly module, which performs logical channel prioritization, multiplex the data from multiple logical channels and generate the MAC PDUs.

Similarly, gNB 2 has an antenna, which transmits and receives radio signals. A RF transceiver, coupled with the antenna, receives RF signals from antenna, converts them to baseband signals, and sends them to processor. RF transceiver also converts received baseband signals from processor, converts them to RF signals, and sends out to antenna. Processor processes the received baseband signals and invokes different functional modules to perform features in gNB2. Memory stores program instructions and data to control the operations of gNB2. The Memory also stores UE INACTIVE AS CONTEXT. In one embodiment, the UE INACTIVE AS CONTEXT also has another set of parameters configured supporting data transmission in INACTIVE, which includes the configurations for physical layer and MAC layer. gNB2 also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention.

A RRC State controller, which controls UE RRC state by sending command to UE or providing configuration for the conditions. A DRB controller, which suspends or resumes the DRBs of a UE. In one embodiment, the DRB is resumed when a burst of data is to be transmitted; the DRB is suspended when the transmission of data burst is finished. An INACTIVE AS CONTEXT controller, which manage to store, restore or release the UE INACTIVE AS CONTEXT. A protocol controller, which controls the establishment, re-establishment, release, reset, reconfiguration of the user plane protocols including PDCP, RLC and MAC for the UE. In one embodiment, the SDAP layer is optionally configured.

The gNB also includes multiple function modules in MAC layer that carry out different tasks in accordance with embodiments of the current invention. Random access (RA) module, which performs random access for a UE. It supports 2-step RA procedure and 4-step RA procedure. Configured Grant (CG) module, which receives data on the pre-configured PUSCH resources. Time alignment (TA) module, which controls and performs the UL time alignment procedure for a UE. HARQ module, which performs HARQ process for one or multiple TBs. Assistant information module, which receives assistant information from the UE for scheduling. De- multiplex and de-assembly module, which de-multiplex and de-assemble the MAC PDUs received from the UE.

Fig. 2 illustrates an exemplary NR wireless system with centralization of the upper layers of the NR radio stacks in accordance with embodiments of the current invention. Different protocol split options between Central Unit and lower layers of gNB nodes may be possible. The functional split between the Central Unit and lower layers of gNB nodes may depend on the transport layer. Low performance transport between the Central Unit and lower layers of gNB nodes can enable the higher protocol layers of the NR radio stacks to be supported in the Central Unit, since the higher protocol layers have lower performance requirements on the transport layer in terms of bandwidth, delay, synchronization and jitter. In one embodiment, SDAP and PDCP layer are located in the central unit, while RLC, MAC and PHY layers are located in the distributed unit.

Fig. 3 illustrates an exemplary flowchart to perform data transmission without RRC Connection in INACTIVE in accordance with embodiments of the current invention. UE initiates data transmission in INACTIVE. UE does not need to send RRC signaling and resume RRC connection for data transmission. UE restores the UE AS INACTIVE CONTEXT. After the procedure initiation, UE performs data transmission and optionally reception in INACTIVE. If transmission of all the data in the buffer is completed, UE stops the data transmission and stays in INACTIVE state. If more data arrives, receives a command or UE moves out of an area, UE falls back to the procedure to resume RRC connection.

Fig. 4 illustrates an exemplary flowchart to initiate data transmission without RRC connection in INACTIVE in accordance with embodiments of the current invention. UE in INACTIVE receives system information. In one embodiment, the system information provides configuration for UE to initiate small data transmission without RRC CONNECTION in INACTIVE. In one embodiment, the user plane of the UE receives the resume requested by NAS layer. In one embodiment, UE performs unified access control and initiate data transmission if the access attempt is not barred. In one embodiment, UE doesn’t need to perform the unified access control. Whether UE can skip the unified access control is configured by the network. Then UE checks whether it can transmit data direction without RRC connection based on certain conditions, which include:

● UE stays in the coverage of an area;

● The data amount is below a threshold;

For the condition that UE stays in the coverage of an area, in one embodiment, the different areas with different sets of cells are configured by the network. UE can performs data transmission without RRC connections when it stays in the same area. When UE moves out of the area and goes in to another area, UE needs to resume RRC connection to perform data transmission. The information for the area is provided by the system information or by dedicated RRC signaling. In one particular case, if such area is not configured, UE can initiate data transmission without RRC connection if UE moves within the same cell, i.e. no cell reselection occurs.

For the condition that the data amount is below a threshold, in one embodiment, if the total data amount is below the threshold, UE can initiate data transmission without RRC connection in INACTIVE. Otherwise, UE needs to resume RRC connection to perform data transfer.

In one embodiment, the capability of support data transfer without RRC connection in INACTIVE is provided in the system information.

Then UE restores the UE INACTIVE AS CONTEXT and applies the configuration including the security keys, the ROHC state, the stored QoS flow to DRB mapping rules, the C-RNTI used in the source PCell, the cell Identity and the physical cell identity of the source PCell, and all other parameters configured for data transmission in INACTIVE. UE resumes the DRBs which are configured to be able to transmit data in INACTIVE. The MAC layer multiplex the logical channels DTCH carrying DRBs, which have data for transmission in INACTIVE.

Fig. 5 illustrates an exemplary flowchart to transmit data in INACTIVE in accordance with embodiments of the current invention. In one novel aspect, UE stays in INACTIVE and enables HARQ, DRX, UL time alignment, BSR and data inactivity monitoring. UE performs TA alignment procedure to obtain or maintain the UL time alignment. If TA timer expires, UE needs to initiate RA procedure to acquire the UL time alignment. UE performs BSR procedure to send BSR to the network. If there is no UL grant available, UE will initiate SR procedure. Then UE performs HARQ operation for one or more shots transmission. UE enables and performs DRX if DRX for data transmission in INATIVE is configured. UE performs data inactivity monitoring if DataInactivityTimer for data transmission in INACTIVE is configured.

Fig. 6 illustrates an exemplary flowchart to transmit data without RRC connection through RA procedure in INACTIVE in accordance with embodiments of the current invention. In one novel aspect, the data available for transmission in L2 is large and cannot be carried by Msg3/MsgA. The overall data packets are segmented into different parts and carried in different transport blocks (TBs) . UE initiates RA procedure and acquires TA in RAR. UE transmits the MAC CE containing UE Identity in Msg3/MsgA. In one embodiment, the short MAC-I for authentication is transmitted in MAC CE and multiplex with the MAC CE containing UE Identity in a MAC PDU. In one embodiment, the UE Identity is C-RNTI. In one embodiment, the UE Identity is I-RNTI. If contention is resolved, UE sets the C-RNTI to the value of the TEMPORARY_C-RNTI (4-step RA) or the value received in the success RAR (2-step RA) . Then it continues monitoring PDCCH and performs data transmission/reception in INACTIVE. In one embodiment, UE multiplex BSR, the MAC CE containing UE Identity and optionally UL data in Msg3/MsgA.

Fig. 7 illustrates an exemplary flowchart to transmit data without RRC connection through pre-configured UL resources in INACTIVE in accordance with embodiments of the current invention. In one embodiment, the overall data packets are segmented into different parts and carried in different transport blocks (TBs) . UE multiplexes BSR and UL data in one MAC PDU and transmits the MAC PDU in the first UL transmission opportunity. Then it continues monitoring PDCCH and performs data transmission/reception in INACTIVE. In one embodiment, UE additionally provides UE ID in each UL transmission. The MAC CE containing UE ID is multiplexed with the UL data. In one embodiment, UE can only transmit data through pre-configured UL resources if UL TA is valid. If UL TA is not valid, UE release the pre-configured UL resources and performs RA procedure to acquire the UL time alignment. After that, UE continues data transfer by monitoring PDCCH address C-RNTI. In one embodiment, if UL TA is not valid, UE performs RA procedure to acquire the UL time alignment but keeps the per-configured UL resources. After that, UE continues data transfer by both the pre-configured UL resources and the resources dynamically scheduled by network.

Fig. 8 illustrates an exemplary flowchart to stop data transmission INACTIVE in accordance with embodiments of the current invention. UE monitors the suspension conditions to suspend data transmission. When one of the suspension condition is met, UE suspends the DRBs configured with data transmission in INACTIVE and stops data transmission. In one embodiment, the suspension is controlled by network. Therefore, one of the condition is that a command is received from the network. In one embodiment, the command is a PDCCH with HARQ ACK. In one embodiment, the command is a MAC CE indicating data transmission suspension.

In one embodiment, the suspension is controlled by UE. Therefore, the conditions are evaluated by the UE itself. One of the condition is that the L2 buffer is empty. One of the conditions is that the DataInactivityTimer expires and it implies that UE has no data for transmission/reception for a while. One of the conditions is that an indication is received from the upper layering, indicating that there is no further uplink or downlink data transmission and no further uplink data transmission subsequent to the uplink data transmission is expected. In one novel aspect, UE sends an indication to network when one of the conditions evaluated by itself is satisfied. In one embodiment, UE sends BSR with the value ‘0’ to network.

Fig. 9 illustrates an exemplary flowchart to fall back to resume RRC connection in accordance with embodiments of the current invention. UE monitors the fallback conditions to resume RRC. When the condition is met, UE resumes RRC connection. In one embodiment, RRC connection resume is controlled by network. Therefore, one of the condition is that a command is received from the network. In one embodiment, the command is Paging message.

In one embodiment, RRC connection resume is controlled by UE. Therefore, the conditions are evaluated by the UE itself. One of the condition is that the more data arrives in the L2 buffer. One of the conditions is that an indication is received from the upper layering, indicating that there is further uplink or downlink data transmission or further uplink data transmission subsequent to the uplink data transmission is expected. In one embodiment, the condition is that the buffer is not empty and UE moves to another area. In one novel aspect, UE sends an indication to network when one of the conditions evaluated by itself is satisfied. In one embodiment, UE triggers and reports BSR to network. Then UE waits for the network command, e.g. paging message. In another embodiment, when one of the conditions is satisfied, UE fallbacks to the legacy mechanism and initiates RRC resume procedure by transiting RRCResumeRequest message.

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

Claims

A method for a UE with stored UE INACTIVE AS CONTEXT to perform one or multiple shots of data transmission without RRC connection in INACTIVE comprising:

initiating data transmission without RRC connection in INACTIVE when a request is received from upper layer;

restoring UE INACTIVE AS CONTEXT, wherein the UE INACTIVE AS CONTEXT contains the INACTIVE data transmission configuration;

resuming one or multiple DRBs which require data transmission in INACTIVE state and performing data transmission/reception for those DRBs;

stopping data transmission/reception and suspending the DRBs when one of the suspension conditions is met; and

resuming RRC connection to perform data transmission/reception when one of the fallback conditions is met.
The method of claim 1, wherein the INACTIVE data transmission configuration includes at least physical layer configuration and MAC configuration.
The method of claim 1, wherein the UE initiates data transmission without RRC connection when one or more conditions are met:

UE stays in the coverage of an area;

The data amount is below a threshold;

The network is capable of data transmission/reception without RRC connection in INACTIVE.
The method of claim 3, wherein the area consists of a sets of cells and the information of the area is provided by the system information or RRC signaling.
The method of claim 3, wherein the data amount threshold and the network capability to perform data transmission/reception without RRC connection is provided in system information.
The method of claim 1 further comprising: maintaining the PDCP SN when resuming and suspending the DRB.
The method of claim 1, UE performs data transmission/reception in INACTIVE further comprising: performing DRX, HARQ, UL time alignment, BSR and data inactivity monitoring in INACTIVE.
The method of claim 1, UE performs data transmission/reception in INACTIVE further comprising: performing segmentation for the UL packets, using RA procedure and monitoring PDCCH addressed to C-RNTI for data transmission.
The method of claim 1, UE performs data transmission/reception in INACTIVE further comprising: performing segmentation for the UL packets, using per-configured PUSCH resource if UL TA is valid and performing RA procedure first to acquire the UL TA if UL TA is invalid.
The method of claim 1, wherein the suspension conditions comprising:

receiving a command from network to suspend the DRBs;

L2 buffer is empty;

An indication is received from the upper layer;

DataInactivityTimer expires.
The method of claim 10, further comprising sending an indication to network to stop the data transmission.
The method of claim 10, further comprising triggering and sending BSR with value 0 to the network.
The method of claim 1, wherein the fallback conditions comprising:

receiving a command from network;

More data arrives;

An indication is received from the upper layer;

L2 buffer is not empty and UE moves to another area.