Downlink data transmission method and apparatus

Abstract

Embodiments of the present application disclose a downlink data transmission method, apparatus, electronic device, and storage medium. The method is applied to a serving base station and includes: when there is downlink data of a terminal in the Radio Resource Control Inactive (RRC_Inactive) state, sending indication information to the terminal, where the indication information is used to instruct the terminal to initiate a two-step random access; receiving a first random access message sent by the terminal; after identifying the identity of the terminal according to the first random access message, sending a second random access message to the terminal, where the second random access message carries the downlink data to implement Small Data Transmission (SDT). The downlink data transmission method of the embodiments of the present application enables the terminal in the RRC_Inactive state to quickly receive downlink data, reducing the latency and power consumption of the terminal.

Description

Technical Field

[0001] This application relates to a downlink data transmission technology, and provides a downlink data transmission method and apparatus. Background Art

[0002] The 3GPP R17 version introduced the Small Data Transmission (SDT) enhancement feature, which allows the terminal to quickly complete small packet data transmission in the RRC_Inactive state without transitioning to the RRC_Connect state. However, in related technologies, for downlink data packets, the terminal needs to transition to the RRC_Connect state to receive them, increasing network latency and terminal power consumption. Summary of the Invention

[0003] The purpose of this application is to provide a downlink data transmission method, a downlink data transmission apparatus, an electronic device, and a computer-readable storage medium, which enable a terminal in the RRC_Inactive state to quickly receive downlink data, reducing latency and terminal power consumption.

[0004] This application proposes a downlink data transmission method, characterized in that the method includes: when there is downlink data of a terminal in the Radio Resource Control Inactive (RRC_Inactive) state, sending indication information to the terminal, where the indication information is used to instruct the terminal to initiate a two-step random access; receiving a first random access message sent by the terminal; after identifying the identity of the terminal according to the first random access message, sending a second random access message to the terminal, where the second random access message carries the downlink data to implement Small Data Transmission (SDT).

[0005] In an example of this application, the indication information includes a paging message, where the paging message carries the terminal's Radio Network Temporary Identifier and an SDT indication field, and the SDT indication field is used to indicate that the reason for paging is for SDT transmission, so that the terminal can learn that the base station pre-transmits data through downlink SDT.

[0006] In an example of this application, the indication information includes Downlink Control Information (DCI), and the DCI is used to send a Physical Downlink Control Channel (PDCCH) to the terminal to trigger the terminal to initiate a contention-based two-step random access.

[0007] In an example of this application, the DCI includes a first indication field and a second indication field. The first indication field is used to indicate the preamble ID of the contention preamble used when the terminal initiates a two-step random access; the second indication field is used to indicate whether the random access is triggered by downlink SDT.

[0008] In an example of the present application, sending the second random access message to the terminal includes: sending a request message carrying a reason for the request to the previous serving base station according to the radio network temporary identifier of the terminal, where the reason for the request is to perform an SDT connection, and the request message is used to request the context information of the terminal; receiving the context information of the terminal sent by the previous serving base station, where the context information of the terminal is sent by the previous serving base station after deciding to migrate the context information of the terminal; determining that the terminal remains in RRC_Inactive for SDT transmission, and sending an interface address to the previous serving base station so that the previous serving base station forwards the received downlink data through the interface address; receiving the downlink data forwarded by the previous serving base station, and sending the second random access message to the terminal.

[0009] In an example of the present application, after sending the second random access message to the terminal, the method further includes: sending an RRC release message to the terminal, where the RRC release message carries a Suspendconfig field for configuring the RRC_Inactive of the terminal.

[0010] In an example of the present application, sending the second random access message to the terminal includes: sending a request message carrying a reason for the request to the previous serving base station according to the radio network temporary identifier of the terminal, where the reason for the request is to perform an SDT connection, and the request message is used to request the context information of the terminal; receiving partial context information sent by the previous serving base station, where the partial context information is sent by the previous serving base station after deciding not to migrate the context information of the terminal; sending an information confirmation message to the previous serving base station, where the information confirmation message includes a downlink transport network layer (TNL) address, so that the previous serving base station sends the downlink data through the TNL address; receiving the downlink data sent by the previous serving base station, and sending the second random access message to the terminal.

[0011] In an example of the present application, after sending the second random access message to the terminal, the method further includes: receiving a context acquisition failure message sent by the previous serving base station, where the context acquisition failure message carries an RRC release message, and the RRC release message carries a Suspendconfig field for configuring the RRC_Inactive of the terminal; forwarding the RRC release message to the terminal.

[0012] In an example of the present application, the method further includes: modifying the configuration information element IE in the RRC protocol to add a downlink SDT field; and allocating a random access channel RACH resource for random access through the downlink SDT field.

[0013] The present application also proposes a downlink data transmission device, including: a sending module, configured to send indication information to a terminal when there is downlink data of a terminal in the Radio Resource Control Inactive state (RRC_Inactive), where the indication information is used to instruct the terminal to initiate two-step random access; a receiving module, configured to receive a first random access message sent by the terminal; and the sending module is further configured to send a second random access message to the terminal after identifying the identity of the terminal according to the first random access message, where the second random access message carries the downlink data to implement small data transmission (SDT).

[0014] The present application also proposes an electronic device, where the electronic device includes: one or more processors; and a storage device, configured to store one or more programs, which, when executed by the one or more processors, cause the electronic device to implement the method as described above.

[0015] The present application also proposes a computer-readable storage medium, on which computer-readable instructions are stored. When the computer-readable instructions are executed by a processor of a computer, the computer is caused to execute the method as described above.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] In the technical solution provided by the present application, when there is downlink data of a terminal in the RRC_Inactive state, the serving base station sends indication information to the terminal to instruct the terminal to initiate two-step random access. Then, during the random access process, the serving base station sends a second random access message to the terminal, and additionally attaches the downlink data in the second random access message, so as to enable the terminal in the RRC_Inactive state to quickly receive downlink data without transitioning to the RRC_Connected state, reducing the latency and terminal power consumption for services that infrequently receive downlink data packets. Description of the Drawings

[0018] Figure 1 is a schematic diagram of an implementation environment related to the present application;

[0019] Figure 2 is a flowchart of a downlink data transmission method shown in an exemplary embodiment of the present application;

[0020] Figure 3 ShowsFigure 2 The flowchart in step S130 in the illustrated embodiment in an exemplary embodiment;

[0021] Figure 4 shows Figure 2 The flowchart in step S130 in the illustrated embodiment in another exemplary embodiment;

[0022] Figure 5 The flowchart of the downlink transmission method for the MT RA-SDT with UE context relocation scenario shown in an exemplary embodiment of the present application;

[0023] Figure 6 The flowchart of the downlink transmission method for the MT RA-SDT without UE context relocation scenario shown in an exemplary embodiment of the present application;

[0024] Figure 7 is a schematic structural diagram of a downlink data transmission device shown in an exemplary embodiment of the present application;

[0025] Figure 8 shows the schematic structural diagram of the computer system of the electronic device suitable for implementing the embodiments of the present application. Detailed implementation manners

[0026] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all the implementation manners consistent with the present application. On the contrary, they are merely examples of the devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0027] The block diagrams shown in the drawings are only functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0028] The flowcharts shown in the drawings are only exemplary descriptions, not necessarily including all the contents and operations / steps, nor necessarily executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may be changed according to the actual situation.

[0029] It should also be noted that: "a plurality of" mentioned in this application means two or more. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the front and back associated objects.

[0030] Explanation of relevant technical terms is provided here.

[0031] RRC_Inactive state (inactive state):

[0032] A terminal (UE) state between RRC_Connect (connected state) and RRC_Idle (idle state). The UE still remains in the CM-CONNECTED state and can move within the radio access network notification area (RNA) without notifying the base station (gNB). If the gNB receives downlink data or signaling, the gNB will page the UE in all cells within the RNA where the UE is located.

[0033] When transitioning from the RRC_Inactive state to the RRC_Connect state, the names of the RRC messages in the access process are different from those in the access process initiated from the Idle state. Msg3, Msg4, and Msg5 are RRCResumeRequest / RRCResumeRequest1, RRCResume, and RRCResumeComplete respectively.

[0034] In the 5G Release R17 version, the uplink (MO) SDT for RRC_Inactive state terminals is divided into two types: RA-SDT (small packet data transmission based on random access) and CG-SDT (small packet transmission based on preconfigured resources):

[0035] RA-SDT, the UE initiates a small packet service on the PRACH (Physical Random Access Channel) resources configured by the base station and sends RRC signaling and small packet service data on Msg3 (4-step RACH) or MsgA (2-step RACH).

[0036] CG-SDT, the UE sends RRC signaling and small packet service data through the uplink unscheduled resources preconfigured by the base station.

[0037] The terminal determines whether SDT transmission can be performed based on the uplink data volume and whether the TA timer is valid. When it is possible to perform CG-SDT transmission, the terminal preferentially selects CG-based SDT.

[0038] This application proposes a downlink RA-SDT transmission method; please refer to Figure 1 , Figure 1 which is a schematic diagram of an implementation environment involved in this application. The implementation environment includes a terminal 10 and a serving base station 20, where the terminal 10 and the serving base station 20 communicate through a wired or wireless network;

[0039] The serving base station 20 is used to send indication information to the terminal when there is downlink data of a terminal in the RRC_Inactive state. The indication information is used to instruct the terminal to initiate a two-step random access; receive the first random access message sent by the terminal 10; after identifying the identity of the terminal according to the first random access message, send a second random access message to the terminal, where the second random access message carries downlink data to implement small data transmission SDT.

[0040] The terminal 10 is used to initiate a random access procedure, send a first random access message to the serving base station 20, and receive the second random access message carrying downlink data sent by the serving base station 20.

[0041] This application sends downlink data to RRC_Inactive state terminals by carrying downlink data in the random process.

[0042] Please refer to Figure 2 , Figure 2 which is a flowchart of a downlink data transmission method shown in an exemplary embodiment of this application. The downlink data transmission method is executed by the serving base station 20 shown in Figure 1 and the downlink data transmission method includes steps S110 to S140, which are introduced in detail as follows:

[0043] S110: When there is downlink data of a terminal in the RRC_Inactive state, send indication information to the terminal, and the indication information is used to instruct the terminal to initiate a two-step random access.

[0044] In the embodiment of this application, when the serving base station receives downlink data of a terminal in the RRC_Inactive state, it will send an indication message to the terminal; where the serving base station may receive the downlink data from the core network or from other base stations, which is not limited here.

[0045] It should be noted that the indication information is used to instruct the terminal to initiate a two-step random access. That is to say, after receiving the indication information, when the terminal determines that the conditions for initiating a two-step random access procedure are met, it will then initiate a two-step random access procedure.

[0046] In an alternative embodiment of the present application, the indication information includes a paging message Paging, where the paging message carries the Radio Network Temporary Identity (RNTI) of the terminal, so that the terminal can determine whether to send its own paging message; among them, the RNTI can be an Inactive Radio Network Temporary Identity (I-RNTI), such as full-RNTI.

[0047] The paging message also carries an SDT indication field, which is used to indicate that the reason for paging is to perform SDT transmission, so that the terminal can learn that the base station pre-transmits data through downlink SDT, that is, the terminal knows through the SDT field that the base station will send data to itself through downlink SDT.

[0048] Among them, before sending the paging message, the base station also needs to modify the standard paging message to obtain a paging message used to indicate the terminal to initiate random access. Modifying the standard paging message includes adding a new paging cause value (pagingCause) to obtain the SDT indication field.

[0049] In another alternative embodiment of the present application, the indication information includes DCI (Downlink Control Information), which is used to send a PDCCH (Physical Downlink Control Channel) to a terminal in the RRC_Inactive state to trigger the terminal to initiate a two-step random access based on competition.

[0050] Among them, the DCI is scrambled with the terminal-specific RNTI. Scrambling means multiplying the scrambling code by the original information to obtain new information; compared with the original information, the new information is scattered in time and frequency. The advantage of doing this is to reduce the interference in adjacent intervals and randomize the information.

[0051] It should be understood that the time slot for sending the DCI can be the time slot for sending the paging message, or the time slot for the PEI (Paging Early Indicator), or a new period and time can be defined, which is not limited here.

[0052] It should be noted that the DCI includes a first indication field and a second indication field. The first indication field is used to indicate the preamble ID used by the terminal when initiating a two-step random access; the second indication field is used to indicate whether it is a random access triggered by downlink SDT. For example:

[0053] Random Access Preamble index–6bits: A value of 0 indicates that the terminal will use a common preamble ID for subsequent access.

[0054] MT-SDT Indicator–1bit: Used to indicate whether the access is triggered by MT (downlink)-SDT. 0 means no, 1 means yes.

[0055] It can be understood that the DCI format in this application can be a new DCI Format; it can also be obtained by modifying the standard DCI Format, for example, modifying the standard DCI Format 1_0. For example, the PDCCH DCI Format 1_0 for RRC_Inactive state terminals is scrambled with a certain proprietary RNTI, and all bits in the "Frequency domain resource assignment (indicating the type of frequency domain resource allocation)" field are 1. The definitions of other fields are as follows:

[0056] Random Access Preamble index–6bits: A value of 0 indicates that the terminal will use a common preamble ID for subsequent access.

[0057] MT-SDT Indicator–1bit: Used to indicate whether the access is triggered by MT-SDT. 0 means no, 1 means yes.

[0058] Reserved bits.

[0059] In the example, the DCI Format uses a scrambled RNTI, which can be P-RNTI (Paging Radio Network Temporary ID), or the RNTI used to scramble PEI (PEI-RNTI), or I-RNTI, or a newly defined RNTI used to scramble SDT (SDT-RNTI). If a new SDT-RNTI is defined, this RNTI can be carried in the RRC reconfiguration message or the RRC Release message to inform the terminal.

[0060] S120. Receive the first random access message sent by the receiving terminal.

[0061] When the terminal determines that the conditions for initiating two-step random access are met, it sends the first random access message to the serving base station, and then the serving base station receives this first random access message.

[0062] Preferably, the first random access message is MsgA, and MsgA includes RRC Resume Request or RRC Resume Request1.

[0063] S130. After identifying the identity of the terminal according to the first random access message, send a second random access message to the terminal, where the second random access message carries downlink data to implement small data transmission (SDT).

[0064] It should be noted that the first random access message carries the identification information of the terminal. Thus, the base station can identify the identity of the terminal based on the identification information in the first random access message. After determining that the terminal to which the second random access message is to be sent is the terminal in step S110, the base station sends the second random access message to the terminal. The second random access message carries the downlink data sent to the terminal to implement SDT.

[0065] Preferably, the second random access message is MsgB. The MsgB includes RAR (Request - Action - Response) and RRC Resume, and also includes downlink data.

[0066] In the embodiment of the present application, the serving base station sends downlink data in the two - step random access process, enabling the terminal in the RRC_Inactive state to quickly receive downlink data packets without transitioning to the RRC_Connect state. For services that infrequently receive downlink data packets (such as periodically receiving downlink heartbeat messages), the latency and terminal power consumption are reduced.

[0067] In an embodiment of the present application, when the terminal initiates two - step random access, it can use common RACH (Random Access Channel) resources, and the serving base station can also allocate dedicated RACH resources for SDT. It should be noted that in Release 17, the serving base station can allocate dedicated RACH resources for uplink SDT. Therefore, the terminal can share the dedicated RACH resources allocated for uplink SDT.

[0068] The serving base station can also allocate dedicated RACH resources for uplink SDT and downlink SDT respectively; in the embodiment of the present application, when allocating dedicated RACH resources for downlink SDT, relevant IEs in the RRC protocol need to be modified to add a downlink SDT field, and then dedicated RACH resources for random access are allocated for downlink SDT through the downlink SDT field.

[0069] It should be noted that in FeatureCombination-r17, a new field is added for MT-SDT, or a new FeatureCombination-r18 IE is created, which contains the MT-SDT field. Examples of the fields include: MT-smallData-r18 ENUMERATED{true} OPTIONAL, -- Need R.

[0070] It should be noted that in some examples, after sending the second random access message to the terminal, if the serving base station receives the confirmation message from the terminal for the second random access message, it then sends an RRC release message (RRCRelease) to the terminal to release the RRC connection.

[0071] Furthermore, after receiving the confirmation message from the terminal for the second random access message, it is confirmed whether there is new downlink data of the terminal that needs to be scheduled for transmission. If there is no new downlink data that needs to be scheduled, an RRC release message is directly sent to the terminal. If there is new data that needs to be scheduled, an uplink DCI is sent to the terminal so that the terminal sends RRCResumeComplete, and then enters the dynamic scheduling process of RRC_Connect.

[0072] In some examples, after sending the second random access message to the terminal, if a negative message from the terminal for the second random access message is received, the second random access message is retransmitted.

[0073] Here, an explanation is given that the serving base station obtains the downlink data of the terminal from other serving base stations, and then transmits the downlink data to the terminal through the second random access message.

[0074] It can be understood that the terminal can move within the RNA area without notifying the serving base station. If the terminal makes a move in the RRC_Inactive state and the serving base station changes, Figure 2 the base station is the current serving base station, and the current serving base station needs to obtain the downlink data of the terminal from the previous serving base station (Last serving gNB).

[0075] At this time, the current serving base station will receive the paging message sent by the previous serving base station, learn from the paging message that the previous serving base station has received the downlink data of the terminal, and then send the aforementioned indication message to the terminal, and then perform downlink SDT transmission through the second random access message.

[0076] The downlink SDT includes MT RA-SDT with UE context relocation (downlink SDT based on random access with context relocation), that is, the previous serving base station decides to provide the UE context to the current serving base station, and the current serving base station manages the terminal context again.

[0077] The downlink SDT also includes MT RA-SDT without UE Context relocation (downlink SDT based on random access without context relocation), that is, the previous serving base station decides not to provide the UE context to the current serving base station, and the previous serving base station still manages the terminal context.

[0078] In the scenario of MT RA-SDT with UE context relocation, as Figure 3 shown, sending a second random access message to the terminal includes:

[0079] S310. Send a request message carrying a request reason to the previous serving base station according to the radio network temporary identity of the terminal. The request reason is to perform SDT connection, and the request message is used to request the context information of the terminal.

[0080] In the embodiment of the present application, the first random access message carries the radio network temporary identity of the terminal. The current base station sends a request message to the previous serving base station according to the radio network temporary identity of the terminal and the Xn-AP interface. The request message is used to request the context information of the terminal, and it indicates in the request message that the request reason is to perform SDT connection.

[0081] S320. Receive the context information of the terminal sent by the previous serving base station. The context information of the terminal is sent by the previous serving base station after deciding to migrate the context information of the terminal.

[0082] If the previous serving base station decides to migrate the context information of the terminal, it feeds back the context information of the terminal to the current serving base station. For example, the previous serving base station determines that the terminal moves out of the configured RNA and decides to migrate the context information of the terminal.

[0083] S330. Determine that the terminal remains in RRC_Inactive for SDT transmission, and send an interface address to the previous serving base station so that the previous serving base station forwards the received downlink data through the interface address.

[0084] S340. Receive the downlink data forwarded by the previous serving base station, and send a second random access message to the terminal.

[0085] The current base station decides to keep the terminal in the RRC_Inactive state for MT SDT, that is, it does not change the state of the terminal, and sends the interface address, such as Xn-U, to the previous serving base station, so that the previous serving base station can forward the previously received downlink data through the interface address. Then, after receiving the downlink data, the terminal is sent a second random access message.

[0086] In an embodiment of the present application, after sending the second random access message to the terminal, it further includes:

[0087] Sending an RRC release message to the terminal, and the RRC release message carries a Suspendconfig field for configuring the RRC_Inactive of the terminal.

[0088] In an embodiment of the present application, that is, after the downlink SDT transmission is completed, the current base station sends a release message to the terminal to release the RRC connection, and the release message also carries Suspendconfig for configuring the terminal to be in RRC_Inactive.

[0089] In the MT RA-SDT with UE context relocation scenario, as Figure 4 shown, sending the second random access message to the terminal includes:

[0090] S410. Sending a request message carrying a reason for the request to the previous serving base station according to the radio network temporary identifier of the terminal, the reason for the request is to perform SDT connection, and the request message is used to request the context information of the terminal.

[0091] For details, please refer to S310, which will not be elaborated here.

[0092] S420. Receiving partial context information sent by the previous serving base station, and the partial context information is sent by the previous serving base station after deciding not to migrate the context information of the terminal.

[0093] The previous serving base station decides not to migrate the context information of the terminal, and sends a partial UEcontext message to the current base station. Then, the current base station extracts partial context information from the partial UE context message, and the partial context information includes RLC (Radio Link Control protocol) context related to SDT.

[0094] S430. Sending an information confirmation message to the previous serving base station, and the information confirmation message includes a downlink transport network layer TNL address, so that the previous serving base station can send downlink data through the TNL address.

[0095] S440: Receive the downlink data sent by the previous serving base station and send a second random access message to the terminal.

[0096] After receiving partial context information, the current base station sends an information confirmation message to the previous serving base station, which includes a downlink TNL address, enabling the previous serving base station to send downlink data through this downlink TNL address.

[0097] The current base station receives the downlink data sent by the previous serving base station through the downlink TNL address and sends a second random access message to the terminal.

[0098] In the embodiments of this application, in the MT RA-SDT with UE context relocation scenario, after sending the second random access message to the terminal, it further includes:

[0099] Receive the context acquisition failure message sent by the previous serving base station. The context acquisition failure message carries an RRC release message, and the RRC release message carries a Suspendconfig field for configuring the RRC_Inactive of the terminal; forward the RRC release message to the terminal.

[0100] In the embodiments of this application, after the downlink SDT transmission is completed, the previous serving base station will send a context acquisition failure message to the current serving base station. The context acquisition failure message contains an RRC release message, and the RRCRelease message contains a Suspendconfig field to configure the RRC_Inactive state of the terminal. Then, the current serving base station forwards the RRCRelease message to the terminal, enabling the terminal to be configured in the RRC_Inactive state.

[0101] In some examples, after the current base station receives the downlink data sent by the previous serving base station, it will send a RETRIEVE UE CONTEXT CONFIRM to the previous serving base station to end the SDT connection.

[0102] For ease of understanding, this embodiment describes the downlink data transmission method with a relatively specific application scenario and specific examples;

[0103] Among them, the terminal is in the RRC_Inactive state. As Figure 5 shown, the downlink transmission method in the MT RA-SDT with UE context relocation scenario includes:

[0104] S510: The Last serving gNB triggers RAN paging within the RNA area.

[0105] S520. The Last serving gNB sends RAN paging to the Receiving gNB.

[0106] S530. The Receiving gNB sends the paging message paging or DCI to the UE.

[0107] In addition to carrying the full-RNTI (I-RNTI) information of the terminal, the Paging message also carries an SDT indication field.

[0108] Among them, for the changes to the Paging message sent by the Receiving gNB to the terminal, a new pagingCause (identifying the cause value of paging) can be added. Example:

[0109]

[0110]

[0111] S540. The UE sends MsgA to the Receiving gNB.

[0112] After receiving the Paging message, the terminal in the RRC_Inactive state determines from the full-RNTI in it that it is a Paging message sent to itself, and knows through the SDT indication field that the base station will send data to itself through downlink SDT. The terminal determines that the conditions for two-step RACH are met, so it initiates a two-step random access procedure, that is, first sends MsgA (preamble + RRCResumeRequest), where the I-RNTI information of itself is carried in the RRCResumeRequest.

[0113] S550. The Receiving gNB sends a Retrieve UE Context Request to the Last serving gNB.

[0114] The Receiving gNB obtains the context information of the terminal from the Last Serving gNB through the I-RNTI information and the Xn-AP interface. The Receiving gNB indicates in the message that the request Request is for the SDT connection.

[0115] S560. The Last serving gNB feeds back a RETRIEVE UE CONTEXT RESPONSE to the Receiving gNB.

[0116] The Last Serving gNB decides to migrate the UE context information and feeds back a RETRIEVE UE CONTEXT RESPONSE message to the Receiving gNB to request the UE context information.

[0117] S570. The Receiving gNB determines to keep the UE in RRC INACTIVE, sends the Xn-U interface address to the Last serving gNB, and receives the downlink data forwarded by the Last serving gNB.

[0118] The Receiving gNB decides to keep the UE in the RRC INACTIVE state for MT SDT, and sends the Xn-U interface address to the Last serving gNB to enable the Last serving gNB to forward the previously received downlink data.

[0119] S580. The Receiving gNB sends a message carrying MsgB to the UE.

[0120] After receiving the forwarded downlink data, the Receiving gNB sends MsgB (RAR + RRCResume + DL data) to the UE, where the DL data is the downlink data.

[0121] S590. The Receiving gNB sends a PATH SWITCH Request to the AMF.

[0122] S5100. The AMF sends a PATH SWITCH Request ACK to the Receiving gNB.

[0123] The Receiving gNB initiates a PATH SWITCH procedure on the NGAP (NG Application Protocol, an application layer protocol between 5G-AN and AMF (Access and Mobility Management Function)) interface to establish a signaling connection between the UE and the serving AMF.

[0124] S5110. The Receiving gNB decides to stop SDT transmission.

[0125] S5120. The Receiving gNB sends an RRC Release message carrying the Suspend config field to the UE.

[0126] After the SDT downlink data transmission is completed, the receiving gNB sends an RRC Release message to the terminal and includes the Suspendconfig field to configure the RRC INACTIVE state of the terminal.

[0127] S5130, the Receiving gNB sends a UE Context Release message to the Last serving gNB.

[0128] In the embodiments of the present application, when the terminal is in the RRC_Inactive state, such as Figure 6 shown, the downlink transmission method for the MT RA-SDT without UEcontext relocation scenario includes:

[0129] S610, the Last serving gNB triggers RAN paging within the RNA area.

[0130] S620, the Last serving gNB sends the RAN paging to the Receiving gNB.

[0131] S630, the Receiving gNB sends a paging message paging or DCI to the UE.

[0132] The DCI is scrambled with the RNTI dedicated to the terminal, and the DCI message instructs the terminal to initiate contention-based random access.

[0133] The DCI is used to send a PDCCH to the RRC_Inactive state terminal to trigger the terminal to initiate random access. The time slot for sending the DCI can be the time slot for sending Paging, can be the time slot of the PEI, or a new period and moment can be defined.

[0134] A new DCI Format (format) can be defined, and the DCI fields are defined as follows (example):

[0135] -Random Access Preamble index–6bits: The value is 0, indicating that the terminal will use a common preamble ID for subsequent access.

[0136] -MT-SDT Indicator–1bit: Used to indicate whether the access is triggered by MT-SDT. 0 means no, 1 means yes.

[0137] -Reserved bits

[0138] The new DCI Format uses a scrambled RNTI, which can utilize the P-RNTI, or the PEI-RNTI, or the I-RNTI, or define a new SDT-RNTI. If a new SDT-RNTI is defined, this RNTI can be carried in the RRC reconfiguration message or the RRC Release message to inform the terminal.

[0139] The above DCI for the access of RRC_Inactive state terminals can also utilize the existing DCI Format1_0 to define a new usage mode. The following is an example:

[0140] The PDCCH DCI1_0 for RRC_Inactive state terminals is scrambled with a certain proprietary RNTI (which can be P-RNTI / PEI-RNTI / I-RNTI / SDT-RNTI), and all bits in the "Frequency domain resource assignment" field are 1. The other fields are defined as follows:

[0141] - Random Access Preamble index – 6 bits: A value of 0 indicates that the terminal will use a common preamble ID for subsequent access.

[0142] - MT-SDT Indicator – 1 bit: Used to indicate whether the access is triggered by MT-SDT. 0 means no, and 1 means yes.

[0143] - Reserved bits

[0144] S640. The UE sends MsgA to the Receiving gNB.

[0145] S650. The Receiving gNB sends a Retrieve UE Context Request to the Last serving gNB.

[0146] For S640 and S650, please refer to S540 and S550, which will not be elaborated here.

[0147] S660. The Last serving gNB decides to migrate the UE CONTEX.

[0148] S670. The Last serving gNB sends a Partial UE context to the Receiving gNB.

[0149] The Last Serving gNB decides not to migrate the UE context information and sends partial context information to the Receiving gNB, which includes the RLC context related to SDT.

[0150] S680. The Receiving gNB feeds back ACK to the Last Serving gNB.

[0151] After receiving the partial context information, the Receiving gNB feeds back ACK to the Last Serving gNB and includes the downlink TNL address in it, so that the Last Serving gNB can send downlink data packets to the Receiving gNB.

[0152] It should be noted that the Receiving gNB will create an SDT RLC (Radio Link Control) entity; the Last Serving gNB will maintain a PDCP (Packet Data Convergence Protocol) entity.

[0153] S690. The Receiving gNB sends MsgB to the UE.

[0154] After receiving the downlink data packet sent by the Last Serving gNB, the Receiving gNB sends MsgB (RAR + RRCResume + DL data) to the UE. Then the UPF transmits downlink small data to the UE through the Last Serving gNB and the Receiving gNB, and the UE transmits uplink small data to the UPF through the Last Serving gNB and the Receiving gNB.

[0155] S6100. The Last Serving gNB sends RETRIEVE UE CONTEXT FAILURE to the Receiving gNB.

[0156] S6110. The Receiving gNB sends an RRCRelease message to the UE.

[0157] After the SDT downlink data transmission is completed, the Last serving gNB feeds back a failure message for obtaining context information to the Receiving gNB, which includes an RRCRelease message. The RRCRelease message contains a Suspendconfig field to configure the RRC_Inactive state of the terminal. The Receiving gNB forwards the RRC Release message to the terminal.

[0158] In addition, before step 10, the Receiving gNB may send a RETRIEVE UECONTEXT CONFIRM to the Last serving gNB to end the SDT connection.

[0159] In Figure 5 and Figure 6 For the two-step random access of the terminal triggered by the downlink SDT, common two-step RACH resources can be used, and the base station can also allocate dedicated RACH resources for SDT. In Release 17, the base station can allocate dedicated RACH resources for the uplink SDT. The newly introduced downlink SDT can share this part of the dedicated RACH resources with the uplink SDT, and the base station can also allocate dedicated RACH resources for the uplink and downlink SDTs respectively.

[0160] If the uplink and downlink SDTs do not share the dedicated RACH resources allocated by the base station, that is, the RACH resources allocated by the base station are only for the downlink SDT, which involves changes to the RRC protocol-related IEs. A new field needs to be added for MT-SDT in FeatureCombination-r17, or a new FeatureCombination-r18 IE needs to be created, which contains the MT-SDT field. For example:

[0161]

[0162]

[0163] The following introduces the device embodiments of the present application, which can be used to execute the data synchronization method in the above embodiments of the present application. For the details not disclosed in the device embodiments of the present application, please refer to the embodiments of the above data synchronization method of the present application.

[0164] As Figure 7 shown, Figure 7 is a schematic structural diagram of a downlink data transmission device shown in an exemplary embodiment of the present application, including:

[0165] A sending module 710, configured to send indication information to a terminal when there is downlink data of a terminal in a Radio Resource Control Inactive (RRC_Inactive) state, where the indication information is used to instruct the terminal to initiate a two-step random access;

[0166] A receiving module 720, configured to receive a first random access message sent by the terminal;

[0167] The sending module 710 is further configured to send a second random access message to the terminal after identifying the identity of the terminal according to the first random access message, where the second random access message carries downlink data to implement Small Data Transmission (SDT).

[0168] In some embodiments of the present application, based on the foregoing solution, the indication information includes a paging message, where the paging message carries a Radio Network Temporary Identifier (RNTI) of the terminal and an SDT indication field, and the SDT indication field is used to indicate that the reason for paging is to perform SDT transmission, so that the terminal can learn that the base station pre-transmits data through downlink SDT.

[0169] In some embodiments of the present application, based on the foregoing solution, the indication information includes Downlink Control Information (DCI), and the DCI is used to send a Physical Downlink Control Channel (PDCCH) to the terminal to trigger the terminal to initiate a contention-based two-step random access.

[0170] In some embodiments of the present application, based on the foregoing solution, the DCI includes a first indication field and a second indication field. The first indication field is used to indicate a preamble ID of a contention preamble used by the terminal when initiating a two-step random access; the second indication field is used to indicate whether the random access is triggered by downlink SDT.

[0171] In some embodiments of the present application, based on the foregoing solution, the sending module 710 is specifically configured to send a request message carrying a request reason to a previous serving base station according to the Radio Network Temporary Identifier of the terminal, where the request reason is to perform an SDT connection, and the request message is used to request context information of the terminal; the receiving module 720 is specifically configured to receive the context information of the terminal sent by the previous serving base station, and the context information of the terminal is sent by the previous serving base station after deciding to migrate the context information of the terminal; the sending module 710 is further configured to determine that the terminal remains in RRC_Inactive for SDT transmission, and send an interface address to the previous serving base station, so that the previous serving base station forwards the received downlink data through the interface address; the receiving module 720 is further configured to receive the downlink data forwarded by the previous serving base station, and send a second random access message to the terminal.

[0172] In some embodiments of the present application, based on the foregoing solution, the sending module 710 is further configured to send an RRC release message to the terminal, and the RRC release message carries a Suspendconfig field for configuring RRC_Inactive of the terminal.

[0173] In some embodiments of the present application, based on the foregoing solution, the sending module 710 is specifically configured to send a request message carrying a reason for the request to the previous serving base station according to the radio network temporary identifier of the terminal. The reason for the request is to perform an SDT connection, and the request message is used to request the context information of the terminal. The receiving module 720 is specifically configured to receive partial context information sent by the previous serving base station. The partial context information is sent by the previous serving base station after deciding not to migrate the context information of the terminal. The sending module 710 is further configured to send an information confirmation message to the previous serving base station. The information confirmation message includes a downlink transport network layer (TNL) address, so that the previous serving base station sends downlink data through the TNL address. The receiving module 720 is further configured to receive the downlink data sent by the previous serving base station and send a second random access message to the terminal.

[0174] In some embodiments of the present application, based on the foregoing solution, the sending module 710 is further configured to receive an obtain context failure message sent by the previous serving base station. The obtain context failure message carries an RRC release message, and the RRC release message carries a Suspendconfig field for configuring RRC_Inactive of the terminal. Forward the RRC release message to the terminal.

[0175] In some embodiments of the present application, based on the foregoing solution, the apparatus further includes a modification module, configured to modify a configuration information element (IE) in the RRC protocol to add a downlink SDT field; and allocate a random access channel (RACH) resource for random access through the downlink SDT field.

[0176] It should be noted that the apparatus provided in the above embodiments and the method provided in the above embodiments belong to the same concept. The specific manners in which each module and unit perform operations have been described in detail in the method embodiments and will not be repeated here.

[0177] In an exemplary embodiment, an electronic device includes one or more processors; a storage device for storing one or more programs, which when executed by the one or more processors, cause the electronic device to implement the method as described above.

[0178] Figure 8 The structural schematic diagram of a computer system of an electronic device suitable for implementing the embodiments of the present application is shown.

[0179] It should be noted thatFigure 8 The computer system 800 of the illustrated electronic device is merely an example and should not impose any limitation on the functions and scope of use of the embodiments of the present application.

[0180] As Figure 8 shown, the computer system 800 includes a central processing unit (CPU) 801, which can perform various appropriate actions and processes according to the programs stored in the read-only memory (ROM) 802 or the programs loaded from the storage section 808 into the random access memory (RAM) 803, such as executing the methods described in the above embodiments. In the RAM 803, various programs and data required for system operation are also stored. The CPU 801, ROM 802, and RAM 803 are connected to each other via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0181] The following components are connected to the I / O interface 805: an input section 806 including a keyboard, a mouse, etc.; an output section 807 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc. and speakers, etc.; a storage section 808 including a hard disk, etc.; and a communication section 809 including a network interface card such as a LAN (Local Area Network) card, a modem, etc. The communication section 809 performs communication processing via a network such as the Internet. A drive 810 is also connected to the I / O interface 805 as required. A removable medium 811, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 810 as required so that the computer program read from it can be installed into the storage section 808 as required.

[0182] Specifically, according to the embodiments of the present application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, the embodiments of the present application include a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a computer program for executing the methods shown in the flowcharts. In such an embodiment, the computer program can be downloaded and installed from the network through the communication section 809 and / or installed from the removable medium 811. When the computer program is executed by the central processing unit (CPU) 801, various functions defined in the system of the present application are executed.

[0183] In an exemplary embodiment, a computer-readable storage medium stores a computer program, which, when executed by a processor, implements the method as described above. The computer-readable storage medium may be included in the electronic device described in the above embodiment, or may exist independently without being assembled into the electronic device.

[0184] It should be noted that the computer-readable medium shown in the embodiments of the present application may be a computer-readable signal medium, a computer-readable storage medium, or any combination of the two. A computer-readable storage medium may be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the above. More specific examples of the computer-readable storage medium may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above.

[0185] In the present application, a computer-readable storage medium may be any tangible medium that contains or stores a program, which can be used by or in conjunction with an instruction execution system, apparatus, or device. In the present application, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, which carries a computer-readable computer program. Such a propagated data signal may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in conjunction with an instruction execution system, apparatus, or device. The computer program included on the computer-readable medium may be transmitted by any appropriate medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0186] The units described in the embodiments of the present application may be implemented in software or in hardware, and the described units may also be provided in a processor. Among them, the names of these units do not constitute a limitation to the unit itself in some cases.

[0187] Those skilled in the art will readily conceive of other embodiments of the present application after considering the specification and practicing the embodiments disclosed herein. The present application is intended to cover any variations, uses, or adaptations of the present application, which follow the general principles of the present application and include the common general knowledge or conventional technical means in the technical field not disclosed in the present application.

[0188] The above content is only a preferred exemplary embodiment of the present application and is not used to limit the implementation of the present application. Those of ordinary skill in the art can easily make corresponding changes or modifications according to the main concept and spirit of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope required by the claims.

Claims

1. A downlink data transmission method, characterized in that, The method includes: When there is downlink data for a terminal in the Radio Resource Control Inactive (RRC_Inactive) state, sending indication information to the terminal, where the indication information is used to instruct the terminal to initiate a two-step random access; the indication information includes Downlink Control Information (DCI), and the DCI is used to send a Physical Downlink Control Channel (PDCCH) to the terminal to trigger the terminal to initiate a contention-based two-step random access; the DCI includes a first indication field and a second indication field, where the first indication field is used to indicate the preamble ID of the contention preamble used when the terminal initiates a two-step random access; the second indication field is used to indicate whether it is a random access triggered by downlink SDT; the time slot in which the DCI is sent includes the time slot in which the paging message is sent or the time slot indicated by the paging preview. Receiving a first random access message sent by the terminal. After identifying the identity of the terminal based on the first random access message, sending a second random access message to the terminal, where the second random access message carries the downlink data to implement Small Data Transfer (SDT).

2. The method according to claim 1, wherein The sending of the second random access message to the terminal includes: Sending a request message carrying a request reason to the previous serving base station according to the terminal's Radio Network Temporary Identifier (RNTI), where the request reason is for SDT connection, and the request message is used to request the context information of the terminal. Receiving the context information of the terminal sent by the previous serving base station, where the context information of the terminal is sent by the previous serving base station after deciding to migrate the context information of the terminal. Determining that the terminal remains in RRC_Inactive for SDT transmission, and sending an interface address to the previous serving base station so that the previous serving base station forwards the received downlink data through the interface address. Receiving the downlink data forwarded by the previous serving base station, and sending the second random access message to the terminal.

3. The method according to claim 2, wherein After sending the second random access message to the terminal, the method further includes: Sending an RRC release message to the terminal, where the RRC release message carries a Suspendconfig field for configuring the RRC_Inactive of the terminal.

4. The method according to claim 1, wherein The sending of the second random access message to the terminal includes: Sending a request message carrying a request reason to the previous serving base station according to the terminal's Radio Network Temporary Identifier (RNTI), where the request reason is for SDT connection, and the request message is used to request the context information of the terminal. Receiving partial context information sent by the previous serving base station, where the partial context information is sent by the previous serving base station after deciding not to migrate the context information of the terminal. Sending an information confirmation message to the previous serving base station, where the information confirmation message includes a Downlink Transport Network Layer (TNL) address, so that the previous serving base station sends the downlink data through the TNL address. Receive the downlink data sent by the previous serving base station and send a second random access message to the terminal.

5. The method according to claim 4, wherein After sending the second random access message to the terminal, the method further includes: Receive a context acquisition failure message sent by the previous serving base station, where the context acquisition failure message carries an RRC release message, and the RRC release message carries a Suspendconfig field for configuring RRC_Inactive of the terminal; Forward the RRC release message to the terminal.

6. The method according to any one of claims 1 to 5, characterized in that, The method further includes: Modify the configuration information element IE in the RRC protocol to add a downlink SDT field; Allocate a random access channel RACH resource for random access through the downlink SDT field for downlink SDT.

7. A downlink data transmission device, characterized in that, Includes: A sending module, configured to send indication information to the terminal when there is downlink data of a terminal in the radio resource control inactive state (RRC_Inactive), where the indication information is used to instruct the terminal to initiate two-step random access; the indication information includes downlink control information (DCI), and the DCI is used to send a physical downlink control channel (PDCCH) to the terminal to trigger the terminal to initiate contention-based two-step random access; the DCI includes a first indication field and a second indication field, where the first indication field is used to indicate the preamble ID of the contention preamble used when the terminal initiates two-step random access; the second indication field is used to indicate whether it is a random access triggered by downlink SDT; the time slot in which the DCI is sent includes the time slot in which the paging message is sent or the time slot indicated by the paging preview; A receiving module, configured to receive a first random access message sent by the terminal; The sending module is further configured to send a second random access message to the terminal after identifying the identity of the terminal according to the first random access message, where the second random access message carries the downlink data to implement small data transmission (SDT).

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