WO2011137715A1

WO2011137715A1 - Method and system for realizing single radio voice call continuity

Info

Publication number: WO2011137715A1
Application number: PCT/CN2011/072887
Authority: WO
Inventors: 陶全军; 谢振华; 卢飞
Original assignee: 中兴通讯股份有限公司
Priority date: 2010-05-04
Filing date: 2011-04-15
Publication date: 2011-11-10
Also published as: CN102238678B; CN102238678A

Abstract

The present invention discloses a method and a system for realizing single radio voice call continuity. Wherein the method includes that: a universal mobile telecommunication system radio access network (UTRAN) or a GSM EDGE radio access network (GERAN) informs, via an enhanced mobile switch center (eMSC), a mobility management entity (MME) in a packet switch (PS) domain network to prepare to hand over a user equipment (UE) from a circuit switch (CS) domain network to the PS domain network; the MME determines there is not a bearer for the UE in the PS domain network, requests a packet data network gateway in the PS domain network to create a bearer for the UE, and informs an evolved universal mobile telecommunication system radio access network (E-UTRAN) to allocate air interface resources to the bearer; the MME informs the UE to hand over to the PS domain network via the CS domain network; and the UE uses the air interface resources allocated by the evolved UTRAN to transmit voice media between the UE and a remote end over the bearer created for the UE, after the UE hands over to the PS domain network. With the present invention, waiting time occupied before the voice call resumes can be saved, voice interruption time can be reduced, and user experience can be enhanced.

Description

TECHNICAL FIELD The present invention relates to the field of communications, and in particular to a method and system for implementing single-channel voice continuity. BACKGROUND OF THE INVENTION Figure 1 is an architecture diagram of an evolved packet domain system (Evolved Packet System, EPS for short), including: Evolved Universal Mobile Telecommunication System Radio Access Network (E-UTRAN or E-UTRAN) EUTRAN), Mobility Management Entity (MME), Serving Gateway (S-GW); Packet Data Network Gateway (PDN GW or P-GW), month The Serving GPRS Supporting Node (SGSN), the Policy and Charging Rule Function (PCRF), and the Home Subscriber Server (HSS). Among them, the P-GW and the S-GW may be combined in one physical entity. FIG. 1B is a single channel voice continuity in the related art (Single Radio Voice Call)

Continuity, referred to as SRVCC) System architecture diagram. The GSM EDGE radio access network (GERAN) is mainly used for 3G/2G Circuit Switch (CS) domain network access; E-UTRAN is mainly used for grouping. Switch (referred to as PS) domain network access; Source Mobile Switch Center (Source Mobile Switch Center, referred to as Source MSC) is mainly used for users in the source circuit switching network user plane and signaling exchange function; enhanced mobile switching center The enhanced mobile switch center (e.g., the eMSC) is used to help the single-channel (Single Radio, abbreviated as SR) UE to complete the voice continuity between the CS domain and the PS domain. The NE can be deployed on the same network element as the Source MSC.

IP Multimedia Core Network Subsystem (IMS) is a related network element in the IMS service system. In the IMS service system, the control layer and the service layer are separated, and the control layer does not provide specific services. The service layer provides the necessary functions of triggering, routing, and accounting. The service triggering and control functions in the control layer are implemented by the Call Session Control Function (CSCF). Call session control functions are divided into: Proxy call session control function (Proxy-CSCF, referred to as P-CSCF), query call session control function (Interrogating-CSCF, referred to as I-CSCF for short) and service call session control function (Serving-CSCF, S-CSCF for short). The service layer is composed of a series of application servers (Application Servers, AS for short), which can provide specific service services. The AS can be an independent entity or exist in the S-CSCF. 2 is a flow chart of the related art in which single channel voice service continuity is switched from a CS domain to a PS domain (which may be referred to as reverse handover), and the SR UE first establishes a session with the remote end in the circuit switched domain network, signaling and The service is anchored in the IMS network, and the SR UE subsequently has single-channel voice continuity. The SR UE accesses from the Long-Term Evolution (LTE) network, re-establishes the connection with the remote media, and maintains the continuous session. The method includes the following steps: 201. The GERAN/UTRAN network decides to initiate handover to the E-UTRAN according to the wireless measurement 4 of the SR UE.

202. The GERAN/UTRAN sends a handover request message (HO Required) to the source MSC, where the message carries a target cell identifier that points to the target E-UTRAN network.

203. The source MSC sends a handover preparation message (Prepare HO Request) to the eMSC according to the target cell identifier in the message, and notifies the target network to perform handover.

204. The eMSC determines that the SR UE does not have a network resource in the target E-UTRAN network, and determines whether the network resource is available, and the eMSC can query the target network MME or query the device.

205. The eMSC returns a handover preparation response message (Preparation HO Response) to the source MSC, where the message carries a Networl Access Indicator (NAI), and the indication is used to notify the SR UE to access the newly created network resource on the E-UTRAN network. Complete the switch;

206. The Source MSC returns a handover response message (HO Response) to the source GERAN/UTRAN network, where the message carries a network access indication.

207. The source GERAN/UTRAN sends a handover command (HO Command) to notify the SR UE to perform handover. The message carries a network access indication, indicating that the UE accesses the E-UTRAN network, and the new network resource completes the handover;

208. The SR UE receives the handover command, switches to the E-UTRAN network according to the network access indication, and initiates a Tracking Area Update (TAU). Since the SR UE switches to the E-UTRAN network, from this point on, the user plane connection between the SR UE and the GERAN/UTRAN is broken, and the voice between the SR UE and the remote end is temporarily unable to communicate.

209. The SR UE establishes a required load on the E-UTRAN network, and the establishment process is a standard PS bearer establishment process, which is not described in detail herein;

210. After the loading is completed, the SR UE registers with the IMS network to which the user belongs.

211. The registration is successful, and the SR UE sends a session invitation message (INVITE) to the home IMS network, and the message carries a session transfer indication statically configured in the UE (Session Transfer)

Indication, referred to as STI, indicates that the IMS network element is used for Service Continuity (SC). The IMS network element updates the remote process, so that the original IP media connection is directly connected to the Source MSC and is directly connected to the SR UE. In the middle, some EPS NEs and other network devices may be used. This step is a standard SC process and is not detailed here;

212. After the remote update succeeds, the IMS network element returns a success message (200 OK) to the SR UE. After receiving the 200 Ok message, the SR UE resumes voice communication with the remote end, and completes the SR UE to switch voice continuity between CS and PS. The inventor has found that in the above-mentioned single mode service continuity implementation method, after the SR UE switches to the E-UTRAN network, the voice communication between the SR UE and the remote end is temporarily interrupted, and the SR UE establishes the required bearer after the E-UTRAN network establishes the required bearer. And registering with the IMS network of the user's home, and performing the update operation on the remote end in steps 310-312 after the registration is successful, and recovering the voice communication between the SR UE and the remote end after performing the update operation on the remote end. . As a result, the call interruption time is too long, which reduces the user experience. SUMMARY OF THE INVENTION A primary object of the present invention is to provide a voice continuity implementation method and system for single channel reverse handover to solve at least one of the above problems. According to an aspect of the present invention, a method for implementing single channel voice continuity is provided, including:

The UTRAN or GERAN informs the PS i or the MME of the network through the eMSC to prepare to handover the UE from the CS domain network to the PS domain network; the MME determines that the PS domain network does not have the bearer of the UE, and requests the packet data network gateway of the PS domain network to create the UE for the UE. Carrying, notifying E-UTRAN to allocate air interface resources for the bearer; the MME notifying the UE to switch to the PS domain network through the CS domain network; After the PS domain network, the voice media allocated between the UE and the remote end is transmitted by using the air interface resource allocated by the evolved UTRAN through the bearer created for the UE. The UTRAN or the GERAN notifies the MME to switch the UE from the CS i or the network to the PS domain network by using the eMSC. The UTRAN or the GERAN sends a handover preparation request message to the eMSC through the source MSC or directly to the eMSC, and the eMSC is notified to prepare to switch the UE from the CS domain network. Go to the PS domain network; the eMSC parses the location information of the target cell from the handover preparation request message, selects the MME according to the location information, and sends a CS to PS handover request message to the MME, where the CS to PS handover request message carries the identity of the UE. The MME notifies the UE that the handover to the PS domain network through the CS domain network includes: the MME sends a CS to PS handover response message to the eMSC; the eMSC returns a handover preparation response message through the source MSC or directly to the UTRAN or GERAN; the UTRAN or GERAN passes the handover command message The UE is notified to switch to the PS domain network. The MME determines that there is no bearer of the UE, and requests the packet data network gateway to create a bearer for the UE, and notifies the evolved UTRAN to allocate the air interface resource for the carrier, including: determining that the UE is not registered in the UI according to the identity of the UE; The subscription user data, selects the packet data network gateway according to the subscription data; 发送 sends a create session request message to the packet data network gateway, requests the packet data network gateway to create a default bearer for the UE; ΜΜΕ receives the create session request response returned by the packet data network gateway The message is sent to the evolved UTRAN to notify the evolved UTRAN to allocate the air interface resource of the default bearer; the MME receives the handover response message returned by the evolved UTRAN, and the signal in the handover response message has the access parameter of the air interface resource. The CS to the PS handover response message, the handover preparation response message, and the handover signaling message carry the access parameter of the air interface resource. After the handover command is sent to the UE, the method further includes: the UE accessing according to the access parameter of the air interface resource Go to the PS domain network. The MME obtains the subscription user data of the UE, and the MME obtains the subscription user data of the locally saved UE. The MME parses the address of the serving GPRS support node SGSN from the CS domain to the PS domain handover request message, and obtains the address of the serving GPRS support node SGSN. User information of the UE; The MME acquires user information of the UE from the home network server of the UE according to the identity of the UE. The method for creating a session carries the single-channel voice continuity identifier SI. After the MME sends the create session request message to the packet data network gateway, the method further includes: the packet data network gateway parses the SI from the create session request, according to the SI. Indicates that a voice-specific bearer is created for the UE. The create session request response message further carries a tunnel end identifier identifier for identifying a bearer allocated by the packet data network gateway, an IP address and a port number of the packet data network gateway access bearer, and a packet data network gateway allocates the UE IP address. The handover request message carries a tunnel end identifier list. After the MME sends the handover request message to the evolved UTRAN, the method further includes: the evolved UTRAN is the identifier allocated by each tunnel end identifier in the tunnel end identifier list. Air interface resources. The CS to PS handover response message, the handover preparation response message, and the handover command message carry the IP address of the UE and the IP address and port number of the packet data network gateway access bearer. After the MME sends the CS to PS handover response message to the eMSC, the method further includes: the eMSC allocates an IP address and a port number of the eMSC for the media connection between the UE and the eMSC; the handover preparation response message and the handover command carry The IP address and port number of the eMSC for the media connection; using the air interface resource allocated by the evolved UTRAN to transmit the voice media between the UE and the remote end by using the bearer created for the UE: the UE or the eMSC according to the IP address and the pair The IP address of the end uses the bearer created for the UE to create a media connection between the UE and the eMSC; and transmits the voice media between the UE and the remote end through the media connection. According to another aspect of the present invention, a single channel voice continuity implementation system is provided, comprising: UTRAN or GERAN, configured to notify an eMSC to prepare to handover a UE from a CS domain network to a PS domain network; eMSC, set to notify The MME of the PS domain network is ready to switch the UE to the PS domain network. The MME is configured to determine whether the PS domain network has a bearer of the UE. If the determination is no, the packet data network gateway requesting the PS domain network creates a bearer for the UE. And after receiving the response that the packet returned by the packet data network gateway is successfully created, notifying the evolved UTRAN to allocate the air interface resource for the bearer, and notifying the UE to switch to the PS domain network through the CS domain network; the packet data network gateway is set to The UE creates a bearer, and after the UE switches to the PS domain network, transmits the voice media between the UE and the remote end through the bearer; the evolved UTRAN is configured to allocate the air interface resource for the bearer created by the packet data network gateway, so that the UE switches. After the PS domain network is connected, the voice media between the UE and the remote end is transmitted through the bearer. The bearer allocated by the packet data network gateway to the UE includes a default bearer and a voice dedicated bearer. With the present invention, in the process of the single-channel UE being handed over from the CS domain network to the PS domain network, before the UE switches to the PS domain network, the PS domain network allocates bearer and air interface resources for the UE, and cuts the UE at the UE. After switching to the PS domain network, the voice media is delivered by using the bearer and air interface resources allocated to the UE, thereby saving the waiting time before the voice call is resumed, reducing the voice interruption time, and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are set to illustrate,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1A is a schematic diagram of an EPS system architecture in the related art; FIG. 1B is a single-mode service continuity architecture diagram in the related art; FIG. 2 is a related art single-mode voice service continuity switching packet switching from a circuit switched domain FIG. 3 is a schematic structural diagram of a system for implementing a single channel voice continuity according to Embodiment 1 of the present invention; FIG. 4 is a schematic structural diagram of a preferred system according to Embodiment 1 of the present invention; FIG. A flowchart of a method for implementing voice continuity of single channel reverse handover according to Embodiment 1 of the present invention; FIG. 6 is a flowchart of Embodiment 2 of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments in the present application and the features in the embodiments may be combined with each other without conflict. Embodiment 1 FIG. 3 is a schematic structural diagram of a single-channel voice continuity implementation system according to Embodiment 1 of the present invention, including: UTRAN/GERAN 10, eMSC 20, MME 30, and packet data network gateway (including S-GW and P-GW) 40 and E-UTRAN 50. The UTRAN/GERAN 10 is configured to notify the eMSC 20 to prepare to handover the UE from the CS domain network to the PS domain network accessed by the E-UTRAN 50; the eMSC 20 is configured to notify the MME 30 of the PS domain network to prepare to switch the UE to a PS domain network; the MME 30, configured to determine whether the current PS domain network has a UE bearer, If not, the packet data network gateway 40 that requests the PS domain network creates a bearer for the UE, and after receiving the bearer creation success response returned by the packet data network gateway 40, notifies the E-UTRAN to allocate air interface resources for the bearer. And notifying the UE to switch to the PS domain network through the source network (ie, the CS domain network); the packet data network gateway 40 is configured to create a bearer for the UE, and after the UE switches to the PS domain network, The voice media; the E-UTRAN 50, is configured to allocate air interface resources for the bearer created by the packet data network gateway 40, so that after the UE switches to the PS domain network, the voice media between the UE and the remote end is transmitted through the bearer. In this embodiment, if the MME 30 determines that the current PS i or the network has the UE's payload, it does not need to notify the packet data network gateway 40 to create a payload, and does not need to notify the E-UTRAN 50 to allocate air interface resources, and the UE switches to the PS domain. After the network, the bearer is used to transmit voice media between the UE and the remote end. In the related art, after the UE switches to the target network, the UE re-creates the required bearer in the target network, and then registers with the user's home IMS network and performs the update operation on the remote end, and then restores the voice between the UE and the remote end. Communication, resulting in longer voice interruptions. In the system provided by this embodiment, when performing the handover process from the CS domain to the PS domain to the SR UE, the MME 30 first notifies the packet data network gateway 40 and the E-UTRAN of the target network before notifying the UE to switch to the target network. 50 performs the process of creating and allocating resources, thereby reducing the time of voice interruption between the UE and the remote end, and improving the user experience. As an alternative embodiment of the present embodiment, the source MSC does not have enhanced capabilities. Therefore, the single channel voice continuity implementation system of this embodiment further includes a source MSC 60, and the source MSC is passed between the UTRAN/GERAN 10 and the eMSC 20. 60 performs message interaction, and FIG. 4 is a schematic diagram of a preferred system architecture according to the present embodiment. In FIG. 4, the existing eMSC 20 is extended, and the eMSC 20 receives the handover preparation request message sent by the source MSC 60 to forward the message to the target MME 30 according to the target cell in the message; the MME 30 can be used for receiving After the message to the eMSC 20, the target network (ie, the PS domain network) is requested to create a bearer for the UE, and the air interface resource is allocated, and the source MSC 60, the eMSC 20, and the UTRAN/GERAN 10 are switched to the PS i or the network through the UE. With the preferred embodiment, the source MSC 60 does not have the enhanced capability, and before the UE switches to the target network, the bearer is created for the UE in the target network, and the air interface resources are allocated, thereby ensuring that the source MSC 60 does not have the enhanced capability. In this case, the interruption time of the call between the UE and the remote end can also be reduced. FIG. 5 is a flowchart of a method for implementing single-channel voice continuity according to the first embodiment of the present invention. The method is used to maintain voice continuity in a process in which a UE switches from a CS domain network to a PS domain network, and mainly includes the following steps: Step 4: S502: Step 4: S508): Step S502, the UTRAN/GERAN notifies the PS i or the MME of the network through the eMSC to prepare to handover the UE from the CS domain network to the PS domain network; for example, the source MSC is an enhanced MSC (ie, eMSC), the UTRAN/GERAN decides to initiate an inter-network access handover according to the radio measurement report reported by the UE, and sends a handover request message to the eMSC to notify the eMSC to switch the UE to the target network, and the eMSC sends a notification to the MME to notify the UE to switch. To the target network; the source MSC is a non-enhanced MSC, and the UTRAN/GERAN decides to initiate an inter-network access handover according to the radio measurement report reported by the UE, and sends a handover request message to the source MSC, where the source MSC carries the target cell information carried by the handover request. And sending a handover preparation message to the eMSC to notify the eMSC to prepare to handover the UE to the target network, and the eMSC notifies the MME. Step S504, the MME determines that the PS domain network does not have the UE bearer, and the packet data network gateway (including the S-GW and the P-GW) that requests the PS domain network creates a bearer for the UE, and notifies the E-UTRAN to allocate the air interface resource for the bearer. For example, the MME may determine that the bearer of the UE does not exist in the PS domain network according to the identifier of the UE carried in the message sent by the UTRAN/GERAN through the eMSC, and the MME may further check whether the UE is already in the MME. If not, the user sends a location update request (for example, Update Location Request) to the HSS to which the UE belongs to obtain the user subscription data, and the HSS returns a location update response message (for example, Update Location Ack) to the MME, where the message is carried. The user subscription data includes the UE's Packet Data Network (PDN) context information and the default bearer related information QoS.

The MME selects the S-GW and the P-GW of the target network according to the user subscription data of the UE, and sends a Create Session Request message (for example, Create Session Request) to the S-GW/P-GW in the target network to create a default bearer. Upon receiving the Create Session Request Reply message (Example, Response Session Response) from the S-GW/P-GW, the MME sends a handover request message (for example, HO Request) to the E-UTRAN, and notifies the E-UTRAN to allocate the bearer. Wireless resources. Upon receiving the E-UTRAN handover response message (HO ACK ), a CS to PS handover response message (CS to PS HO Response) is returned to the eMSC, and the message carries an access parameter for accessing the allocated radio resource. After the UE switches to the target network, voice data between the UE and the remote end can also be transmitted through the dedicated bearer. Preferably, the create session request message sent by the MME to the S-GW/P-GW may further carry a single channel voice continuity identifier (SRVCC Indicator, abbreviated as SI), and the S-GW/P-GW receives the create session request. The message is allocated to the UE according to the SI, and the S-GW/P-GW carries the identifier of the dedicated bearer in the create session response message returned to the MME, and the MME sends the handover request message to the E-UTRAN to carry the dedicated bearer. The identifier of the E-UTRAN is assigned to the dedicated radio resource. After the UE switches to the target network, voice data between the UE and the remote end can also be transmitted through the dedicated bearer. Step S506, the MME informs the UE to switch to the PS domain network through the source network (ie, the CS domain network); for example, the MME sends a CS to PS handover response message to the eMSC, and the eMSC returns a handover preparation response message to the source MSC, and the source MSC sends the handover request message to the GERAN/UTRAN. The handover response message is returned (or, if the source MSC has enhanced capability, the eMSC and the source MSC are the same entity, and the eMSC directly returns a handover response message to the GERAN/UTRAN), and the GERAN/UTRAN informs the UE to switch to the EUTRAN through a handover command message. The CS to PS handover response message, the handover preparation response message, and the handover command message carry access parameters of the radio resource allocated by the EUTRAN, and the UE accesses the PS domain network according to the access parameter of the radio resource resource. Step S508: After the UE switches to the PS domain network, the voice media allocated between the UE and the remote end is transmitted by using the air interface resource allocated by the E-UTRAN through the bearer created for the UE. For example, the UE and the eMSC can exchange mutual IP addresses and port numbers through the foregoing process, and the UE or the eMSC can create a temporary media connection between the UE and the eMSC according to the IP address and port number of the peer. Media connection, the transmission of the UE to the PS domain network and the remote voice media, which can further reduce the time of voice interruption. Alternatively, instead of creating a temporary media connection between the UE and the eMSC,

The process shown in Figure 2 is performed. The difference is that after the UE is switched to the PS domain network, since the target network has created a bearer for the UE, step 209 is not required. After the IMS remote media update is successful, step S504 is used. The created bearer (missing bearer or dedicated bearer) establishes a post-switching path and transmits the voice media between the UE and the far end. The method for implementing the single-channel voice continuity in the foregoing embodiment can create a bearer for the UE in the target network before the UE switches to the target network, thereby avoiding creating a bearer after the UE switches to the target network, thereby causing the voice communication interruption time to be lengthened. The problem has improved the user experience. Embodiment 2 This embodiment describes a procedure for the SR UE to switch from the GERAN/UTRAN to the EUTRAN network when only the circuit domain voice service occurs in the GERAN/UTRAN network. FIG. 6 is a signaling flowchart of the embodiment. The GERAN/UTRAN determines to initiate an access network handover according to the measurement report reported by the SR UE, and sends a handover request message to the Source MSC, which mainly includes the following steps:

601. The GERAN/UTRAN decides to initiate an inter-network access handover according to the radio measurement report reported by the SR UE;

602. The GERAN/UTRAN sends a handover request message to the source MSC, where the target address location cell is the target EUTRAN network cell;

603. After receiving the handover request message, the source MSC selects the eMSC according to the target cell information, and sends a handover preparation message to the eMSC, where the message carries the source cell and the target cell information, and the user identity identifier, such as the IMSI, if the Source MSC determines the device. There is an SGSN address where the UE currently resides, and a 4 bar SGSN address is also included in the message;

604. The eMSC receives the handover preparation message, and selects the MME according to the target cell, and sends a CS to PS handover request message to the message, where the message carries the source cell and the target cell information, and the user identity identifier, such as the IMSI, is also included if the SGSN address is received. In the message. If the Source MSC and the eMSC are the same entity, the source is not required to be transmitted.

a message between the MSC and the eMSC;

605. The MME receives the CS to PS handover request message, determines whether the user information is saved in the local area, and whether the received message has an SGSN address. If neither is available, the MME obtains the user subscription data according to the user identity identifier, for example, , user's context information, etc.;

606. If the MME determines that the received message has SGSN address information, the MME obtains user context information from the SGSN. 607 - 608, the MME selects the S-GW and the P-GW of the monthly service according to the user context information, and sends a create session request to the S-GW/P-GW to create a default bearer of the EPS network, where the message carries the single mode voice. Continuity identification (SRVCC Indicator, SI);

609. After receiving the request for creating a session, the P-GW allocates a default bearer resource, allocates an IP address to the UE, and allocates a voice dedicated bearer according to the SI indication in the message. After the creation, the P-GW allocates a downlink TFT. (Down Link TFT, DL TFT) and Tunnel Endpoint Identifier (TEID), and bind the relationship between them. The TEID is used to identify the assigned bearer. The DL TFT is used by the P-GW to select the allocated bearer to transmit the received external data packet to the user terminal, where the DL TFT sets the UE side IP port number as the network default value; 610. The P-GW returns to the S-GW. Creating a session response message, where the IP address and port number of the bearer connected to the P-GW, the list of the identifier TEID, the DL TFT, and the UE IP related information are included in the message;

611. After receiving the P-GW creation session request, the S-GW allocates the corresponding resource according to the TEID list, and returns a create session request response message to the MME, where the message carries the P-GW and the S-GW assigned bearer. Connected IP address and port number, ? The identifier TEID list, the DL TFT and the UE IP related information are included; if the MME detects that the UE has performed the attachment registration on the network, and the default bearer of the UE has been established, the MME is directly 604 from 4 to 612. ;

612. After the default creation is completed, the target cell information selects the target EUTRAN, sends a handover request message to the target EUTRAN, and notifies the EUTRAN to allocate the air interface resource, and the message carries the 601-611 created carrier, S-GW user plane connection. The connection address of EUTRAN. After the EUTRAN allocates the air interface resource, the media connection between the EUTRAN and the S-GW is established, and the handover response message is returned to the MME, where the message carries the allocated air interface resource access parameter;

613. The MME returns a CS to PS handover response message to the eMSC, where the message carries an EUTRAN air interface resource access parameter, an IP address of the UE, and a DL TFT;

614. After receiving the CS to PS handover response message, the eMSC allocates a user plane IP address and port number for the media connection between the eMSC and the SR UE, and generates a voice service flow template (Traffic Flow Template, TFT) according to the received DL TFT address. The template is used to indicate that the UE and the eMSC establish an SR UE and media connection and receive/send voice media between the eMSC before the IMS remote media update succeeds. Body. The TFT includes a UE side and an eMSC side IP address and a port number, and the UE side port sets a value in the DL TFT;

615. The eMSC returns a handover preparation response message to the Source MSC, where the message carries the TFT generated by step 614, the user establishes the handover number of the CS bearer, and the EUTRAN air interface access parameter;

616a. The source MSC receives the handover preparation response message, and establishes a CS bearer between the Source MSC and the eMSC according to the handover number;

616b. In the step 615, the eMSC returns the handover preparation response message without carrying the handover number, and the eMSC initiates the update remote process, and the remote media is updated to be connected to the eMSC, that is, the media connection between the eMSC and the remote end is established. In practical applications, you can choose to perform any of the above steps 616a and 616b.

617. The Source MSC returns a handover response message to the GERAN/UTRAN, where the message carries the EUTRAN null access parameter and the TFT;

618. The GERAN/UTRAN notifies the SR UE to perform the handover by switching the command message, and the message carries the EUTRAN air interface access parameter and the TFT;

619. The SR UE switches to the EUTRAN network according to the EUTRAN air interface access parameter;

620. The SR UE sends a handover complete message to the EUTRAN network;

621. The EUTRAN receives the handover complete message, and notifies the MME by using a handover notification message;

622. The MME returns a handover complete message to the eMSC, and the eMSC notifies the Source MSC;

623. The Source MSC receives the handover complete message of the target network, and releases the radio resources of the GERAN/UTRAN network (ie, the CS domain network);

624. The eMSC and the SR UE establish a media connection, and the SR UE receives and sends the IP voice data packet according to the voice TFT. The media connection includes two parts: the first part of the connection between the eMSC and the P-GW is an IP data bearer, and the connection complies with The SGi port standard protocol; the other part is that the P-GW sees the media connection with the SR UE, and the connection is an EPS bearer, which complies with the EPS network related protocol. The IP data bearer between the eMSC and the P-GW does not need to be established separately. Only the destination IP and the source IP can be transmitted to each other during the transmission process. eMSC Establishing both direct media connection with the SR UE requires establishing an EPS bearer connection between the SR UE and the P-GW. After receiving the handover complete message, the eMSC directly sends a voice packet to the SR UE according to the voice TFT, and the eMSC converts the circuit domain voice data packet received by the source MSC into an IP data packet, and sends the data packet according to the TFT through the media connection between the two. The SR UE receives the IP voice data packet from the SR UE and converts it into a circuit domain voice packet and forwards it to the Source MSC. The SR UE receives and sends the IP voice data packet according to the voice TFT.

625. If the SR UE has not registered with the IMS, the SR UE performs IMS registration with the user's home IMS;

626. After the registration is completed, the SR UE sends a session invitation message to the IMS network element to notify the IMS to perform the remote update. The message carries the SR UE media IP address and the newly assigned port number and the session transfer identification (Session Transfer Identification) „ IMS Update the remote media connection after the session invitation message;

627. After the remote update succeeds, a completion message is returned, where the message carries the IP address and port number of the remote media, and the far-end voice data packet is sent to the source UE to the SR UE, and the UE receives the completion message. Afterwards, the termination is sent to the eMSC, and the packet is sent to the remote media IP and port.

628. Release the media connection between the SR UE and the eMSC, and the UE initiates release of the dedicated bearer, and the eMSC receives the Source MSC release message, and releases the media connection IP and port. In this embodiment, the eMSC notifies the target network to prepare network resources for the UE, establishes the default load and voice of the UE, and allocates an IP address to the UE in the process of establishing the default load, before notifying the UE to switch to the target network. This reduces the time for voice interruption during the handover. From the above description, it can be seen that, in the embodiment of the present invention, in the process of the single-channel UE being switched from the CS domain network to the PS domain network, the PS domain network allocates a bearer to the UE before the UE switches to the PS domain network. And the air interface resource, after the UE switches to the PS domain network, the voice media is transmitted by using the bearer and air interface resources allocated for the UE, thereby saving the waiting time before the voice call is resumed, reducing the voice interruption time, and improving the user body risk. Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general-purpose computing device, which can be concentrated on a single computing device or distributed over a network composed of multiple computing devices. Alternatively, they may be implemented by program code executable by the computing device, such that they may be stored in the storage device by the computing device and, in some cases, may be different from the order herein. Perform the steps shown or described, or They are separately fabricated into individual integrated circuit modules, or a plurality of modules or steps thereof are fabricated into a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the present invention are intended to be included within the scope of the present invention.

Claims

A method for implementing a single-channel voice continuity for maintaining voice continuity in a process in which a user equipment switches from a circuit switched CS domain network to a packet switched PS domain network, the method comprising:

Global mobile communication system radio access network UTRAN or GSM EDGE radio access network GERAN informs the mobility management entity MME of the PS domain network by the enhanced mobile switching center eMSC to prepare to switch the user terminal UE from the CS domain network to the PS domain network; Determining, by the MME, that the PS domain network does not have a bearer of the UE, requesting a packet data network gateway of the PS domain network to create a bearer for the UE, and notifying the evolved UTRAN to allocate an air interface resource for the bearer;

The MME notifies the UE to switch to the PS domain network through the CS domain network;

After the UE is handed over to the PS domain network, the voice media allocated between the UE and the remote end is transmitted by using the air interface resource allocated by the evolved UTRAN through the bearer created for the UE.

2. The method according to claim 1, wherein the UTRAN or the GERAN notifying, by the eMSC, that the MME is ready to switch the UE from the CS domain network to the PS domain network includes:

The UTRAN or the GERAN sends a handover preparation request message to the eMSC through the source MSC or directly, to notify the eMSC to prepare to switch the UE from the CS domain network to the PS i or the network;

The eMSC parses the location information of the target cell from the handover preparation request message, selects the MME according to the location information, and sends a CS to PS handover request message to the MME, where the CS to PS handover request message is used. Carrying the identity of the UE;

And the MME notifying, by the CS domain network, that the UE switches to the PS domain network includes:

Sending, by the MME, a CS to PS handover response message to the eMSC; Returning, by the eMSC, the handover preparation response message to the UTRAN or the GERAN through the source MSC;

The UTRAN or GERAN informs the UE to switch to the PS i or the network through a handover command message. The method according to claim 2, wherein the MME determines that there is no carrier of the UE, requests the packet data network gateway to create a bearer for the UE, and notifies the evolved UTRAN to allocate air interface resources for the bearer. :

The identity of the MME in the UE determines that the UE is not registered in the MME;

The MME acquires subscription user data of the UE, and selects the packet data network gateway by using the subscription data;

Sending, by the MME, a create session request message to the packet data network gateway, requesting the packet data network gateway to create a default load for the UE;

Receiving, by the MME, a create session request response message returned by the packet data network gateway;

Sending, by the MME, a handover request message to the evolved UTRAN, and informing the evolved UTRAN to allocate the air interface resource of the default bearer;

The MME receives the handover response message returned by the evolved UTRAN, and the signal in the handover response message has an access parameter of the air interface resource. The method according to claim 3, wherein the CS to PS handover response message, the handover preparation response message, and the handover signaling message carry an access parameter of the air interface resource; After the handover command is sent, the method further includes: the UE accessing the PS domain network according to the access parameter of the air interface resource. The method according to claim 3, wherein the acquiring, by the MME, the subscription user data of the UE includes one of the following:

Obtaining, by the MME, locally signed subscription user data of the UE;

The MME parses an address of the serving GPRS support node SGSN from the CS domain to the PS domain handover request message, and acquires user information of the UE from the SGSN; The MME acquires user information of the UE from the home network server of the UE according to the identity identifier of the UE.

The method according to claim 3, wherein the create session request carries a single channel voice continuity identifier SI; after the MME sends the create session request message to the packet data network gateway, The method further includes: the packet data network gateway parsing the SI from the create session request, and creating a voice dedicated payload for the UE according to the indication of the SI.

The method according to claim 6, wherein the creation session request response message further carries a tunnel end identifier identifier for identifying a bearer allocated by the packet data network gateway, and the packet data network gateway is connected. The IP address and port number of the bearer, and the IP address assigned by the packet data network gateway to the UE.

The method according to claim 7, wherein the handover request message carries the tunnel end point identifier list; after the MME sends the handover request message to the evolved UTRAN, the method further The method includes: the evolved UTRAN is an allocated air interface resource identified by each tunnel end identifier in the tunnel end identifier list.

The method according to claim 7, wherein the CS to PS handover response message, the handover preparation response message, and the handover command message carry an IP address of the UE and the packet data network gateway Access the 7-digit IP address and port number.

10. The method according to claim 9, wherein after the MME sends a CS to PS handover response message to the eMSC, the method further includes: the eMSC assigning the eMSC for the IP address and port number of the media connection between the UE and the eMSC;

The handover preparation response message and the handover command carry an IP address and a port number of the eMSC for the media connection;

Transmitting the voice media between the UE and the remote end by using the air interface resource allocated by the evolved UTRAN by using the bearer created for the UE includes:

The UE or the eMSC creates a media connection between the UE and the eMSC by using the bearer created for the UE according to the IP address and the IP address of the peer;

Transmitting voice media between the UE and the far end through the media connection.

11. A single channel voice continuity implementation system, comprising:

UTRAN or GERAN, configured to notify the eMSC to prepare to switch the UE from the CS domain network to the PS domain network;

The eMSC is configured to notify the MME of the PS domain network to prepare to switch the UE to a PS domain network;

The MME is configured to determine whether the bearer of the UE exists in the PS domain network. If the determination is no, the packet data network gateway requesting the PS domain network creates a bearer for the UE, and receives the bearer. After the bearer data network gateway returns a successful response, the evolved UTRAN is configured to allocate an air interface resource to the bearer, and the UE is notified by the CS domain network to switch to the PS domain network.

The packet data network gateway is configured to create a bearer for the UE, and after the UE switches to the PS domain network, transmit, by using the bearer, a voice media between the UE and the remote end;

The evolved UTRAN is configured to allocate an air interface resource to the bearer created by the packet data network gateway, so that after the UE switches to the PS domain network, the UE is transmitted by the bearer and the far Voice media between the ends.

12. The system according to claim 11, wherein the bearer allocated by the packet data network gateway to the UE comprises a default bearer and a voice dedicated bearer.