CN1992957B - Wireless access network framework and method for realizing real-time service nondestructive emigration thereof - Google Patents

Abstract

The invention provides a wireless access network architecture and a method for realizing real-time service lossless migration thereof. The method mainly includes: when the cell handover occurs in the UE, the source ERS (border radio base station) uploads the configuration information of the radio interface protocol stack for the UE to the IAGW (IP Access Gateway), and the IAGW establishes a corresponding wireless network according to the configuration information. An instance of the interface protocol stack, through which the real-time service data of the UE is received and saved; when the UE cell handover is completed, the IAGW sends the configuration information of the wireless interface protocol stack of the UE to the target ERS of the UE, and the target ERS A corresponding wireless interface protocol stack instance is established according to the configuration information, and the real-time service data delivered by the IAGW is received through the instance. The present invention can realize the non-destructive migration of the real-time service data of the UE between the source base station and the destination base station while ensuring the real-time performance of the UE handover process.

Description

Wireless access network architecture and its implementation method for real-time service lossless migration

technical field

The invention relates to the field of network communication, in particular to a wireless access network architecture and a method for realizing lossless migration of real-time services.

Background technique

UMTS (Universal Mobile Telecommunications System, universal mobile communication system) is a third-generation mobile communication system that adopts WCDMA (Wideband Code Division Multiple Access, wideband code division multiple access) air interface technology, and the UMTS system is usually called WCDMA communication system. The UMTS system adopts a system structure similar to that of the second-generation mobile communication system, and its system structure is shown in Figure 1. The system structure mainly includes RAN (Radio Access Network, wireless access network) and CN (Core Network, core network). Among them, RAN is used to handle all wireless-related functions, while CN handles all voice calls and data connections in the UMTS system, and realizes switching and routing functions with external networks. CN is logically divided into circuit switched domain (Circuit Switched, CS) and PS (Packet Switched, packet switched domain). UTRAN (UMTS Territorial Radio Access Network, UMTS Terrestrial Radio Access Network), CN and user equipment together constitute the entire UMTS system.

The network structure of UTRAN is shown in Figure 2, including one or several RNS (Radio Network Subsystem). An RNS consists of an RNC (Radio Network Controller, radio network controller) and one or more NodeBs (base stations). The interface between the RNC and the CN is the lu interface, and the NodeB and the RNC are connected through the lub interface. In the UTRAN, RNCs are interconnected through lur, and lur can be connected through a direct physical connection between RNCs or through a transmission network. The RNC is used to allocate and control the wireless resources of the NodeB connected or related to it. The NodeB completes the conversion of the data flow between the lub interface and the Uu interface, and also participates in a part of radio resource management.

NodeB is the base station (that is, the wireless transceiver) of the WCDMA system, including the wireless transceiver and baseband processing components. Through the standard lub interface and RNC interconnection, it mainly completes the processing of the Uu interface physical layer protocol. Its main functions are spread spectrum, modulation, channel coding and despreading, demodulation, channel decoding, and also include functions such as mutual conversion of baseband signals and radio frequency signals.

The RNC is used to control the radio resources of the UTRAN, and mainly completes functions such as connection establishment and disconnection, handover, macro-diversity combination, and radio resource management and control. details as follows:

1. Perform system information broadcast and system access control functions;

2. Mobility management functions such as handover and RNC Relocation (migration) or relocation;

3. Radio resource management and control functions such as macro-diversity combining, power control, and radio bearer allocation.

3GPP (Third Generation Partnership Projects, Third Generation Partnership Projects) considers the competitiveness of the future network, and is currently considering how the network will evolve in the future. There are many evolution schemes discussed in 3GPP. The purpose of network evolution is to provide A low-latency, high data rate, high system capacity and coverage, low-cost, fully IP-based network.

An existing network evolution solution is a two-layer node architecture, and a schematic diagram of the architecture is shown in FIG. 3 . Under this architecture, ERS (Edge Radio Station, border wireless station) is an evolved NodeB, which has most of the functions of the previous RNC, and adopts new physical layer technologies, such as OFDM (orthogonal frequency division multiplexing, orthogonal frequency division multiplexing, Multiplexing), IAGW (IPAccess GateWay, IP Access Gateway) has part of the function of SGSN (Serving GPRSSupporting Node, Serving General Packet Radio Service Supporting Node) and the previous GGSN (Gateway GPRS Supporting Node, Gateway General Packet Radio Service Supporting Node) function.

In order to ensure the smooth evolution of the existing UTRAN architecture, the two-layer node architecture maximizes the reuse of existing protocols. On the wireless interface side, since ERS has merged most of the functions of the previous RNC, in addition to retaining the original physical layer function (L1), it has also added the MAC (Mium Access Control, Media Access Control layer) layer, RLC (Radio Link Control, radio link control) layer, PDCP (Packet Data Convergence Protocol, packet data convergence protocol) layer, RRC (Radio Resources Control, radio resource control) layer and other protocol layer functions. GTP-U (GPRS Tunneling Protocol for User Plane, GPRS Tunneling Protocol User Plane) tunnel transmission protocol is adopted between ERS and IAGW. The evolved two-layer node architecture, due to the downshifting of the wireless interface protocol stack or user plane protocol stack, reduces the number of transmission nodes, shortens call setup delay and transmission delay, and improves data transmission performance.

Under the above-mentioned two-layer node architecture, since the air interface protocol stack is moved down to the ERS for processing, when a handover process between ERS occurs, the source ERS must forward the UE context stored in it to the target ERS through the IAGW. The entire migration process is as follows: Figure 4 shows. In the process shown in Figure 4, SERS is the source ERS, and TERS is the target ERS. Including the following steps:

1. The SERS judges that the UE needs to switch to the TERS according to the collected measurement data. Since there is no lur interface between SERS and TERS in the evolution architecture, data cannot be exchanged. Therefore, the SERS judges that at the same time as the hard handover, the lu interface needs to be relocated, and a RELOCATION REQUIRED (relocation required) message is sent to the IAGW to trigger the Relocation process.

2. After receiving the above RELOCATION REQUIRED message, the IAGW sends a RELOCATION REQUEST (relocation request) message to TERS, requesting TERS to pre-allocate the required resources for the UE.

3. After receiving the RELOCATION REQUEST message, TERS starts the relevant resource allocation procedure, establishes RRC connection and RAB (Radio Access Bearer) bearer. The specific process is: establish a PDCP/RLC/MAC entity, establish a new wireless link, and start the transmission and reception on the new wireless link; at the same time start the establishment of GTP-U Tunnels for PS RABs (establish PS domain wireless access The GTP_U tunnel of the bearer) transmits the bearer, and establishes the user plane bearer between the TERS and the IAGW. After all necessary resources are successfully established and allocated, the target ERS will send a RELOCATION REQUEST ACKNOWEDGE (Relocation Request Confirmation) message to the IAGW to confirm that the resource allocation is successful.

4. After receiving the RELOCATiON REQUEST ACKNOWEDGE message, the IAGW judges that the resource allocation of the target system is ready, and decides to continue the relocation process. At this time, the IAGW will send a RELOCATION COMMAND (relocation command) message to the source ERS to notify the source ERS to trigger the execution of relocation.

5. After the source ERS receives the RELOCATION COMMAND message, it terminates the relocation preparation process, reads the handover-related parameters of the RELOCATION COMMAND message, prepares the PHYSICAL CHANNEL RECONFIGURATION (physical channel reconfiguration) message for hard handover, and transmits the PHYSICAL CHANNEL RECONFIGURATION message through the Uu interface. The RECONFIGURATION message is sent to the UE, triggering the UE to access the target cell.

6. After receiving the PHYSICAL CHANNEL RECONFIGURATION message, the UE will access the target cell according to the information provided by the PHYSICAL CHANNEL RECONFIGURATION message. After successfully accessing the target cell, the UE will send a PHYSICAL CHANNEL RECONFIGURATION COMPLETE (physical channel reconfiguration complete) message to TERS to notify TERS of the successful handover and trigger the execution of TERS relocation.

7. After receiving the PHYSICAL CHANNEL RECONFIGURATIONCOMPLETE message, TERS starts to execute the SERS function; and sends a RELOCATION DETECT (relocation detection) message to IAGW, indicating that SRNS (Serving Radio Network Subsystem, Serving Radio Network Subsystem) is detected for relocation. After receiving the message, the IAGW switches the user plane from SERS to TERS.

8. TERS sends a RELOCATION COMPLETE message to IAGW, notifying IAGW that the target ERS has completed the RELOCATION process. IAGW receives the RELOCATION COMPLETE message, executes the lu release command, and releases the lu interface connection to SERS. In the real-time case, the source ERS will discard its saved data frames,

The disadvantage of the above-mentioned migration process is that the whole migration process is relatively complicated. In order to ensure the delay of the handover process, during the migration process, the data in the source ERS, such as the UE context information it saves, cannot be transferred from the source ERS to the target ERS as in the lossless migration process, resulting in a large amount of data lost.

Contents of the invention

In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a wireless access network architecture and a method for implementing lossless migration of real-time services, so that real-time services of the UE can be realized while ensuring the real-time nature of the handover process of the UE. Data is migrated losslessly between the source base station and the destination base station.

The purpose of the present invention is achieved through the following technical solutions:

A wireless access network architecture, including border wireless base station ERS and IP access gateway IAGW,

The air interface protocol stack in ERS includes the extended media access control layer E-MAC and the extended radio link control layer E-RLC. In addition to the MAC layer function, E-MAC also adds the segmentation or cascading function of the RLC layer. ;

The IAGW includes the radio interface protocol stack of the E-RLC and the radio interface protocol stack of the radio resource control RRC layer. The radio interface protocol stack of the E-RLC and the radio interface protocol stack of the RRC layer are determined by the source when the user equipment UE switches After the ERS is activated, the ERS and the IAGW use the GPRS tunnel protocol user plane GTP-U tunnel or the mobile IP transmission protocol to carry high-level signaling and data.

The E-RLC includes:

Caching module: Provide caching capability for real-time services carried by non-response mode UM and communication management mode TM;

Automatic retransmission module: For the data service carried by the answer mode AM, it provides the automatic retransmission ARQ function of the execution buffer and retransmission mechanism of the RLC layer;

Sequence number maintenance module: provide the function of maintaining the PDCP sequence number of the packet data convergence protocol PDCP layer by maintaining the SDU sequence number of the RLC service data unit.

A method for real-time service data migration in a wireless access network, comprising the steps of:

A. When the UE undergoes cell handover, the source boundary radio base station ERS uploads the configuration information of the radio interface protocol stack for the UE to the IP access gateway IAGW, and the IAGW establishes a corresponding radio interface protocol stack instance according to the configuration information, through which Instance, receive and save real-time service data of UE;

B. After the cell handover of the UE is completed, the IAGW sends the configuration information of the radio interface protocol stack of the UE to the target ERS of the UE, and the target ERS establishes a corresponding radio interface protocol stack instance according to the configuration information, through which , receiving the real-time service data delivered by the IAGW.

Described step A specifically comprises:

A1. When the UE undergoes cell handover, the source ERS sends a Context TransferRequest message containing configuration information of the UE's radio interface protocol stack E-RLC layer and RRC layer instance to the IAGW;

A2. The IAGW establishes a corresponding radio interface protocol stack E-RLC layer and RRC layer instance for the UE according to the received Context Transfer Request message, and sends a Context Transfer Response message to the source ERS;

A3. After the source ERS receives the Context Transfer Response message, it transparently transmits the RRC message of the UE to the IAGW on the control plane, and transmits the delivered real-time service data and the E-RLC frame cached inside it on the user plane Passed to the E-RLC layer of IAGW for caching;

A4. After the wireless interface protocol stack instance established by the IAGW starts working, the IAGW notifies the target ERS to establish a wireless link and Iu+ transmission bearer for the UE, and the IAGW also notifies the UE through the source ERS to reconfigure the air interface protocol stack, Handover to the cell covered by the target ERS;

A5. After the UE reconfigures its air interface protocol stack, it sends a handover completion message to the IAGW. The handover completion message contains the frame number of the downlink E-RLC frame that the UE expects to receive. After receiving the message, the IAGW stores it in its buffer Delete the sent E-RLC frame;

Described step B specifically comprises:

B1. After the UE cell switching is completed, the IAGW sends a Context TransferRequest message to the target ERS, and the Context Transfer Request message includes configuration information of the radio interface protocol stack for the UE in the IAGW;

B2. After receiving the Context Transfer Request message, the target ERS establishes a corresponding wireless interface protocol stack instance for the UE, and sends a Context Transfer Response message to the IAGW;

B3. After receiving the Context Transfer Response message, the IAGW transmits the E-RLC frame containing the real-time service data buffered inside to the target ERS. .

Described step A3 also includes:

After the source ERS receives the Context Transfer Response message, it stops its internal work on the wireless interface protocol stack instance of the UE, and at the user plane, while continuing to deliver real-time service data, stops its internal E-RLC layer protocol Stack cache function.

Described step B3 also includes:

After the IAGW transmits the E-RLC frame buffered in it to the target ERS, it deletes its internal radio interface protocol stack instance for the UE, and after clearing the E-RLC frame in its buffer area, cancels the buffer area.

Described step B also includes:

After the UE cell handover is completed, the IAGW locally starts the E-RLC buffer data upload timer, and after the timing of the timer arrives, the IAGW notifies the source ERS to delete the radio link for the UE, releases the For the transmission bearer resources allocated for the UE, after the radio link of the UE is deleted, the source ERS deletes the context information for the UE.

Described step B also includes:

When the UE that initiates the handover is moving at high speed or roaming around the edge of the cell, after the handover process is completed, the IAGW will not send the configuration information of the radio interface protocol stack of the UE to the target ERS of the UE.

The Context Transfer Request message and the Context Transfer Response message are realized by modifying the radio network subsystem application protocol RANAP protocol of the Iu interface.

Described step B also includes:

After the process of moving down the air interface protocol stack function is completed, the target ERS that accepts the downshifting of the air interface protocol stack function is responsible for realizing the management of the wireless link for the UE and the caching and transmission of wireless frames, and the UE is under the control of the target ERS Next, carry out the communication and switching process according to the normal protocol flow.

It can be seen from the above-mentioned technical solution provided by the present invention that the present invention redesigns the functions of the ERS and IAGW of the existing two-layer node network architecture, and uses the method of moving up and down the air interface protocol stack to replace the transfer of the UE context , which simplifies the migration process of real-time service data of the UE. On the premise of not interrupting data transmission, the reconstruction of downlink data cache can be completed at the handover anchor point, which ensures the lossless migration of real-time service data during the handover process while ensuring the real-time performance of the handover process.

Description of drawings

FIG. 1 is a schematic structural diagram of a UMTS system;

Fig. 2 is a schematic diagram of the network structure of UTRAN;

FIG. 3 is a schematic diagram of an existing wireless access network two-layer node architecture;

FIG. 4 is a flow chart of the accompanying migration process in the existing two-layer node architecture of the wireless access network;

FIG. 5 is a schematic diagram of a user plane protocol stack in a normal transmission process of the wireless access network architecture according to the present invention;

FIG. 6 is a schematic diagram of a user plane protocol stack in a handover state of the wireless access network architecture according to the present invention;

Fig. 7 is the processing flowchart of the specific implementation manner of the method of the present invention;

Fig. 8 is a flowchart of the process of moving up the function of the air interface protocol stack in the method of the present invention;

FIG. 9 is a schematic diagram of user data flow after UE handover is completed;

FIG. 10 is a flow chart of the downshifting process of the function of the air interface protocol stack in the method of the present invention.

Detailed ways

The present invention provides a wireless access network architecture and a method for implementing lossless migration of real-time services. The core of the present invention is to replace UE context transfer by moving up and down the air interface protocol stack, which simplifies the migration process.

The wireless access network architecture proposed by the present invention is a new two-layer node network architecture. This architecture redesigns the functions of ERS and IAGW of the existing two-layer node network architecture. details as follows:

The air interface protocol stack in ERS has evolved from the original MAC/RLC/PDCP to E-MAC (extended MAC)/E-RLC (extended RLC). In addition to retaining the original MAC layer functions, E-MAC also Added the original division/cascade function of the RLC layer. For data services carried in AM (Answer Mode) mode. E-RLC inherits the ARQ (Automatic Repeat Request) function of the original RLC layer that performs the buffering and retransmission mechanism to ensure the sequential delivery of data.

The E-RLC includes:

Buffering module: For the real-time services carried by the non-response mode UM and the communication management mode TM, it provides buffering capabilities, and provides a flow control mechanism between the E-RLC protocol layer and the E-MAC protocol layer during data transmission.

Automatic retransmission module: For the data service carried by the answering mode AM, it provides the automatic retransmission ARQ function of the RLC layer to perform buffering and retransmission mechanism, so as to ensure the sequential delivery of data.

Sequence number maintenance module: provide the function of maintaining the PDCP sequence number of the packet data convergence protocol PDCP layer by maintaining the SDU sequence number of the RLC service data unit.

In addition to realizing the original core network node function, IAGW also includes the wireless protocol stack of the E-RLC layer and the RRC layer. However, the radio interface protocol stack in the IAGW is only used in some cases, such as being activated by the source ERS during handover, and is not used in general cases. Between the ERS and the IAGW, multiple transmission protocols such as GTP-U tunnel and mobile IP can be used to carry high-level signaling and data.

FIG. 5 is a schematic diagram of a user plane protocol stack of the radio access network architecture of the present invention during normal transmission, and FIG. 6 is a schematic diagram of a user plane protocol stack of the radio access network architecture of the present invention in a switching state.

Based on the above wireless access network architecture, the present invention provides a method for migrating real-time service data. The processing flow of the specific implementation of the method is shown in Figure 7, including the following steps:

Step 7-1. The source ERS moves up the function of the air interface protocol stack.

In the wireless access network architecture proposed by the present invention, the source ERS serving the UE periodically sends measurement control information to the UE, requesting the UE to report the measurement result of the wireless propagation environment. When the UE is at the edge of a certain cell, the source ERS will make a handover decision based on the measurement report reported by the UE. The handover decision will trigger the UE handover process, and at the same time, the UE will perform the real-time service data migration process.

When the migration process of the real-time service starts, the function of the air interface protocol stack is moved up first. The process of moving up the function of the air interface protocol stack is shown in FIG. 8 . The specific description is as follows:

The source ERS first sends a Context Transfer Request (Context Transfer Request) message to the IAGW through the interface with the IAGW, requesting the IAGW to activate the high-layer instance of the wireless interface protocol stack for the corresponding UE. This message mainly includes the configuration information of the radio interface protocol stack instance E-RLC layer and RRC layer of the UE in the current source ERS. After receiving this message, the IAGW will establish the corresponding radio interface protocol stack E-RLC layer and RRC layer. Instance, after the instance starts working, it starts to buffer the received E-RLC frame while continuing to deliver data, and sends a Context Transfer Response (Context Transfer Response) message to the source ERS at the same time. After the source ERS receives this message, it will Stop the work of its own internal related wireless interface protocol stack instance. On the control plane, the source ERS stops processing the RRC message of the corresponding UE, and only performs the transparent transmission function between the UE and the IAGW. On the user plane, while the source ERS continues to deliver real-time service data, it stops its own internal E-RLC layer protocol stack caching function, and transmits the real-time service data and the E-RLC frames cached in it through the link between the ERS and the IAGW. The interface is sent to the IAGW, which is cached by the E-RLC layer of the IAGW.

Step 7-2, the target ERS establishes a new radio link for the UE.

After the wireless interface protocol stack instance established for the corresponding UE in the above IAGW starts to work, the IAGW will notify the target ERS to establish a wireless link and lu+ transmission bearer for the UE through the lu+ interface with the target ERS, and at the same time notify the UE through the source ERS to carry out the air interface The protocol stack is reconfigured, and the cell is switched to the cell covered by the target ERS. After the UE reconfigures its air interface protocol stack, it sends a handover completion message to the IAGW, indicating that the handover process is complete. The handover completion message contains the frame number of the downlink E-RLC frame that the UE expects to receive. After the IAGW receives the message, it deletes the delivered E-RLC frame in its internal buffer. The data transmission after the handover is completed starts from the first unsent E-RLC frame. The first unsent E-RLC frame is a downlink E-RLC frame expected to be received by the UE.

A schematic diagram of the user data flow after the UE handover is completed is shown in FIG. 9 .

Step 7-3, the source ERS deletes the old radio link of the UE.

After the UE handover process is completed, the IAGW starts the E-RLC buffer data upload timer locally, and after the timing of the timer reaches the timing, the IAGW will notify the source ERS to delete the release the transmission bearer resource allocated for the UE. After the previous radio link of the UE is deleted, the source ERS will delete the context information for the UE.

In step 7-4, the IAGW moves down the functions of the air interface protocol stack.

Because the E-RLC air interface protocol layer is located in the IAGW, certain data transmission problems will be introduced, such as generating a large number of flow control frames on the backhaul link between the ERS and the IAGW. Therefore, after a relocation process of the UE is completed, the IAGW will trigger the process of moving down the function of the air interface protocol stack. The flow of the downshifting process of the air interface protocol stack function is shown in FIG. 10 . The specific description is as follows:

During the downshifting of the air interface protocol stack function, the IAGW will send a Context Transfer Request message to the target ERS through the lu+ interface, requesting the target ERS to create a corresponding high-level instance of the wireless interface protocol stack for the UE, that is, the E-RLC and RRC layer instances. The Context Transfer Request message includes current configuration information of the relevant wireless interface protocol stack in the IAGW. After the target ERS receives this message, it will establish the relevant wireless interface protocol stack instance, and send the Context TransferResponse message to the IAGW. After receiving the message, the IAGW will buffer the E-RLC frame containing real-time service data inside it through and The lu+ interface between the target ERS is transmitted to the target ERS, and then the internal wireless interface protocol stack instance for the UE is deleted, and the E-RLC frame in the buffer area is cleared, and the buffer area is canceled.

After the process of moving down the function of the air interface protocol stack and the handover process are completed, the target ERS that accepts the downshifting of the function of the air interface protocol stack is responsible for realizing the management of the wireless link for the UE and the caching and transmission of wireless frames. The UE is in the target ERS Under the control, the communication and switching process are carried out according to the normal protocol flow.

During the above-mentioned real-time service migration process, if the UE that initiates the handover is moving at high speed or roaming back and forth at the edge of the cell. If the IAGW moves the air interface protocol stack instance down to the target ERS after the handover process is completed, the UE will frequently initiate the migration process. In order to avoid waste of air interface resources caused by frequent migration of UEs in the two-layer node architecture, in this case, it may also be considered not to initiate the process of moving down the air interface protocol stack function in step 7-4. However, for UEs moving at low speed, the above real-time service migration process will be continuously performed due to their low handover frequency.

The Context Transfer Request/Response message in the above real-time service migration process can be realized by modifying the existing lu interface RANAP (RNS Application Protocol, RNS application protocol) protocol.

In a word, the switching process and real-time service migration process in the improved two-layer node architecture of the present invention are simpler than the existing switching process and real-time service migration process, and can handle more exceptions.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (8)

1. A wireless access network architecture, comprising a border wireless base station ERS and an IP access gateway IAGW, characterized in that: The air interface protocol stack in ERS includes the extended media access control layer E-MAC and the extended radio link control layer E-RLC. In addition to the MAC layer function, E-MAC also adds the segmentation or cascading function of the RLC layer. ; The IAGW includes the radio interface protocol stack of the E-RLC and the radio interface protocol stack of the radio resource control RRC layer. The radio interface protocol stack of the E-RLC and the radio interface protocol stack of the RRC layer are determined by the source when the user equipment UE switches After the ERS is activated, the ERS and the IAGW use the GPRS tunnel protocol user plane GTP-U tunnel or the mobile IP transmission protocol to carry high-level signaling and data. The E-RLC includes: Caching module: Provide caching capability for real-time services carried by non-response mode UM and communication management mode TM; Automatic retransmission module: For the data service carried by the answer mode AM, it provides the automatic retransmission ARQ function of the execution buffer and retransmission mechanism of the RLC layer; Sequence number maintenance module: provide the function of maintaining the PDCP sequence number of the packet data convergence protocol PDCP layer by maintaining the SDU sequence number of the RLC service data unit. 2. A real-time service data migration method in a wireless access network, characterized in that, comprising steps: A. When the UE undergoes cell handover, the source boundary radio base station ERS uploads the configuration information of the radio interface protocol stack for the UE to the IP access gateway IAGW, and the IAGW establishes a corresponding radio interface protocol stack instance according to the configuration information, through which Instance, receive and save real-time service data of UE; B. After the cell handover of the UE is completed, the IAGW sends the configuration information of the radio interface protocol stack of the UE to the target ERS of the UE, and the target ERS establishes a corresponding radio interface protocol stack instance according to the configuration information, through which , receiving the real-time service data issued by the IAGW; Described step A specifically comprises: A1. When the UE undergoes cell handover, the source ERS sends a Context TransferRequest message containing configuration information of the UE's radio interface protocol stack E-RLC layer and RRC layer instance to the IAGW; A2. The IAGW establishes a corresponding radio interface protocol stack E-RLC layer and RRC layer instance for the UE according to the received Context Transfer Request message, and sends a Context Transfer Response message to the source ERS; A3. After the source ERS receives the Context Transfer Response message, it transparently transmits the RRC message of the UE to the IAGW on the control plane, and transmits the delivered real-time service data and the E-RLC frame cached inside it on the user plane Passed to the E-RLC layer of IAGW for caching; A4. After the wireless interface protocol stack instance established by the IAGW starts working, the IAGW notifies the target ERS to establish a wireless link and Iu+ transmission bearer for the UE, and the IAGW also notifies the UE through the source ERS to reconfigure the air interface protocol stack, Handover to the cell covered by the target ERS; A5. After the UE reconfigures its air interface protocol stack, it sends a handover completion message to the IAGW. The handover completion message contains the frame number of the downlink E-RLC frame that the UE expects to receive. After receiving the message, the IAGW stores it in its buffer Delete the sent E-RLC frame; Described step B specifically comprises: B1. After the UE cell switching is completed, the IAGW sends a Context TransferRequest message to the target ERS, and the Context Transfer Request message includes configuration information of the radio interface protocol stack for the UE in the IAGW; B2. After receiving the Context Transfer Request message, the target ERS establishes a corresponding wireless interface protocol stack instance for the UE, and sends a Context Transfer Response message to the IAGW; B3. After receiving the Context Transfer Response message, the IAGW transmits the E-RLC frame containing the real-time service data buffered inside to the target ERS. 3. method according to claim 2, is characterized in that, described step A3 also comprises: After the source ERS receives the Context Transfer Response message, it stops its internal work on the wireless interface protocol stack instance of the UE, and at the user plane, while continuing to deliver real-time service data, stops its internal E-RLC layer protocol Stack cache function. 4. according to the described method of claim 2 or 3, it is characterized in that, described step B3 also comprises: After the IAGW transmits the E-RLC frame buffered in it to the target ERS, it deletes its internal radio interface protocol stack instance for the UE, and after clearing the E-RLC frame in its buffer area, cancels the buffer area. 5. method according to claim 2 or 3, is characterized in that, described step B also comprises: After the UE cell handover is completed, the IAGW locally starts the E-RLC buffer data upload timer, and after the timing of the timer arrives, the IAGW notifies the source ERS to delete the radio link for the UE, releases the For the transmission bearer resources allocated for the UE, after the radio link of the UE is deleted, the source ERS deletes the context information for the UE. 6. method according to claim 2 or 3, is characterized in that, described step B also comprises: When the UE that initiates the handover is moving at high speed or roaming around the edge of the cell, after the handover process is completed, the IAGW will not send the configuration information of the radio interface protocol stack of the UE to the target ERS of the UE. 7. according to the method described in claim 2 or 3, it is characterized in that, described Context TransferRequest message and Context Transfer Response message are realized by revising the Radio Network Subsystem Application Protocol RANAP protocol of Iu interface. 8. method according to claim 2 or 3, is characterized in that, described step B also comprises: After the process of moving down the air interface protocol stack function is completed, the target ERS that accepts the downshifting of the air interface protocol stack function is responsible for realizing the management of the wireless link for the UE and the caching and transmission of wireless frames, and the UE is under the control of the target ERS Next, the communication and handover process is carried out according to the normal protocol flow.

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