WO2008046319A1 - A method and system to realize voice call continuity when dealing with emergency business - Google Patents

Abstract

A method to realize voice call continuity when dealing with emergency business includes: public safety answering point (PSAP) or user equipment (UE) within source domain initiates a emergency business request; network side judges whether the emergency business meets the qualification of triggering emergency call continuity business; when the qualification is met, the emergency business is anchored to voice call continuity (VCC) application server (AS) and a communication connection between UE within source domain and PSAP is established; VCC AS realizes voice call continuity business based on anchored emergency business. In addition, a emergency business call system and a emergency business call unit also were disclosed. The current project can realize voice call continuity as UE switches between source and destination domains when dealing with emergency business.

Description

 Method and system for realizing voice call continuity in handling emergency services

 The present invention relates to network communication technologies, and more particularly to a method and system for implementing voice call continuity when handling emergency services. Background of the invention

 Currently, the communication community has proposed the concept of Voice Call Continuity (VCC), which is a subscription IP Multimedia Subsystem (IMS) application service for the user's home domain. The so-called IMS is an IP multimedia subsystem defined by the 3rd Generation Mobile Communications Standardization Partnership Project (3GPP) standard. It is a third-generation mobile communication system (3G) mobile network that implements packet voice and packet data to provide unified multimedia services and applications. Target network.

 A user with simultaneous access capabilities of the IMS domain and the circuit switched (CS) domain is referred to as a VCC User Terminal (UE). In a normal voice call continuity service, all UE initiated or received calls must first be anchored to a VCC application server (AS) with domain switching control function in the IMS domain to which the UE belongs, anchored to the VCC AS. Up here means that the call information initiated or received by all UEs is saved on the VCC AS. When the connection between the UE and the 3GPP system is switched between the CS domain and the IMS domain, the VCC AS implements handover between the IMS domain and the CS domain, thereby ensuring that the voice call of the UE remains uninterrupted during the handover, and the user is made to voice. The experience of the service is not affected by changes in the UE connection.

 Currently, emergency services are services that provide users with emergency voice calls. For example, if the user dials the emergency call number 119, the network does not route the emergency call request according to the normal voice call, but directly routes the emergency call request directly to the Public Safety Access Point (PSAP) through the preset call session unit. The PSAP provides services to users.

In the prior art, when the UE initiates an emergency service in the visited IMS domain, the UE initiates an emergency service request by calling the call session unit of the IMS domain and a special user identifier, and the IMS domain call session unit routes the emergency service to the PSAP to establish the UE and the UE. The call connection between the PSAPs. In the above process, since the emergency service initiated by the user is handled by a special call session unit of the visited IMS domain, or the user does not have The card or card user is not registered to obtain the user's subscription information, and the call session unit cannot anchor the voice call to the VCC AS of the user's home IMS domain through the initial filtering rule (iFC).

 In the prior art, when the UE initiates an emergency service in the CS domain, the UE initiates an emergency service request to the CS domain call session unit, and the CS domain call session unit routes the emergency service to the PSAP to establish a call connection between the UE and the PSAP. In the above process, the intelligent service cannot be triggered, and therefore the emergency call cannot be anchored to the VCC AS of the user's home IMS domain.

 In summary, the disadvantage of the prior art is that, regardless of whether the UE initiates an emergency service in the IMS domain or the CS domain, since the emergency call cannot be anchored to the VCC AS, the UE cannot be guaranteed to switch between the source domain and the destination domain. Voice call continuity for emergency services. Summary of the invention

 In view of this, embodiments of the present invention provide a method and system for implementing voice call continuity when handling emergency services, ensuring that the UE can achieve voice call continuity when switching between the source domain and the destination domain.

 The method includes the following steps:

 The public safety access point PSAP or the user terminal UE in the source domain initiates an emergency service request; the network side anchors the emergency service to the voice call continuity VCC application server AS, and establishes the UE between the source domain and the PSAP. Call connection

 The VCC AS implements voice call continuity services based on the anchored emergency services.

 The embodiment of the present invention further discloses an emergency service call system, the system comprising: a UE in a source domain, an emergency service call session unit in the source domain, a PSAP and a VCC AS;

 The UE is configured to initiate an emergency service request carrying emergency call continuity information to the PSAP, and initiate a handover request from the source domain to the destination domain to the VCC AS;

 The emergency service call session unit is configured to anchor the emergency service request to the VCC AS, and establish a call connection between the UE and the PSAP;

The VCC AS anchors an emergency service according to a handover request sent by the UE, and the proxy UE is in the destination A call connection with the PSAP is established in the domain, and the session resources of the UE in the source domain are released.

 An embodiment of the present invention further discloses an emergency service call session unit, where the emergency service call session unit includes:

 a call connection establishing module, configured to establish a call connection between the UE and the PSAP according to an emergency service request from the PSAP or the UE;

 An emergency service anchoring module for anchoring emergency services to a VCC AS in the network.

 As can be seen from the technical solution of the present invention, the present invention provides a method and system for implementing voice call continuity in an emergency service. The system includes a VCC AS and an emergency service call session unit, and the emergency service call session control unit routes the emergency service to the PSAP, and anchors the emergency service to the VCC AS according to the obtained call continuity information. When the UE switches between the source domain and the destination domain, the VCC AS finds the anchored session, and the proxy UE and the PSAP re-negotiate, establish a new session connection, and then release the session resources of the UE in the source domain, thereby When performing emergency services, the continuity of voice calls can be achieved when the source domain and the destination domain are switched.

BRIEF DESCRIPTION OF THE DRAWINGS

 FIG. 1 is a schematic structural diagram of a system for implementing voice call continuity in an emergency service according to an embodiment of the present invention; FIG.

 2 is a flowchart of a method for implementing voice call continuity in an emergency service according to a first preferred embodiment of the present invention;

 2a is a message flow diagram of the method for implementing voice call continuity in an emergency service shown in FIG. 2;

 3 is a flowchart of a method for implementing voice call continuity in an emergency service according to a second preferred embodiment of the present invention;

 FIG. 3a is a message flow diagram of the method for implementing voice call continuity in an emergency service shown in FIG. 3;

4 is a diagram showing a method for implementing voice call continuity in an emergency service according to a third preferred embodiment of the present invention; Flow chart

 FIG. 4a is a message flow diagram of the method for implementing voice call continuity in an emergency service shown in FIG. 4; FIG.

 FIG. 5 is a flowchart of a method for implementing voice call continuity in an emergency service according to a fourth preferred embodiment of the present invention; FIG.

 FIG. 5a is a flow diagram of message interaction of the method for implementing voice call continuity in emergency services shown in FIG. 5. Mode for carrying out the invention

 In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings.

 A method and system for implementing voice call continuity in an emergency service according to an embodiment of the present invention, where an emergency service call session unit is set in a source domain, and a UE or a PSAP in the source domain initiates an emergency service request in the source domain, The service call session unit determines whether the emergency service satisfies the condition for triggering the call continuity service. When the condition for triggering the call continuity service is met, the emergency call is anchored to the VCC AS, and the anchored emergency service is implemented by the VCC AS. Continuity. In this way, when the UE switches between the source domain and the destination domain, the VCC AS can find the anchored session, and after the proxy UE and the PSAP reconnect, release the session resources in the source domain to realize the continuity of the emergency service voice call. .

 The emergency service includes: an emergency service request is initiated by the UE in the source domain to the PSAP, and an emergency service request is initiated by the PSAP to the UE in the source domain, and the emergency service request may carry the emergency call continuity information.

The emergency service call session unit determines, according to the emergency call continuity information, whether the condition for triggering the call continuity service is satisfied; the emergency call continuity information includes emergency service information that can be explicit, for example, emergency service indication, emergency user identification, emergency number Etc.; or implicit emergency service information, including: The call is routed to the session control unit E-CSCF that handles emergency services. The emergency call continuity information may further include terminal call continuity information, where the terminal call continuity information includes: terminal capability, user preference, etc., and may also include network call continuity information, for example, roaming status, access network Network type, contract data, etc.

 The subscription data in the network call continuity information is the subscription data of the UE that initiates the emergency service request, and the subscription data includes the VCC service. The subscription data may be the subscription data of the emergency user identifier of the UE that initiates the emergency service request, or the subscription data of the common public user identifier corresponding to the emergency user identifier of the UE that initiated the emergency service request, or the common public of the UE that initiates the emergency service request. The subscription data of the user identity, or the subscription data of the wildcard type in which the emergency user identity of the UE that initiated the emergency service request conforms.

 When the UE in the source domain makes an emergency service request to the PASP, the method for the emergency service call session unit to trigger to the VCC AS is as follows:

 The emergency service call session unit determines whether the emergency service request carries the displayed or implicit emergency service information, and if so, triggers the emergency service request to the VCC AS.

 Or the emergency service call session unit determines whether the emergency service request carries the displayed or implicit emergency service information, and if yes, and determines that the emergency service request carries at least one of the terminal call continuity information or the network call continuity information, The emergency service request is triggered to the VCC AS. The terminal call continuity information and the network call continuity information may be reported by the terminal, or carried in the service request message, or obtained by the emergency service call session unit to query the third party node.

 Further, before triggering the emergency service request to the VCC AS, the emergency service call session unit obtains the address of the VCC AS. The method for obtaining includes: the emergency service call session unit obtains the address of the VCC AS from the emergency service request; or queries the third-party node for the address of the VCC AS; or obtains the address of the VCC AS from its own configuration. The third party node can be a Home Subscriber Server (HSS), a Home Location Register (HLR), Device Management/Client Provisioning (DM/CP), and the like.

 The network needs to notify the UE of the obtained address of the VCC AS. For example, it may be sent to the UE in the subsequent emergency service request response message by the emergency service call conference unit or the VCC AS, or returned to the UE in the form of a message or the like.

 When the PSAP initiates an emergency service request to a UE in the source domain, such as an emergency service callback, the emergency service call session unit triggers the VCC AS as follows:

The emergency service call session unit can be urgent according to the PSAP identifier carried in the emergency service request. Call continuity information triggers emergency traffic to the VCC AS. For example, UE capabilities or emergency user identification, etc., or other emergency service signs trigger emergency service requests to the VCC AS.

 When the PSAP initiates an emergency service request to the registered user, the emergency service request is first routed to the emergency service call session unit registered by the user in the home domain, and the emergency service call session unit performs the emergency service according to the subscription data in the emergency call continuity information. The request is anchored to the VCC AS to which the user's home domain is contracted, and the emergency service request is further routed to the UE to establish a call connection.

 When the PSAP initiates an emergency service request to an unregistered user, it first obtains the address of the VCC AS from the emergency call continuity information, and then anchors the emergency service request to the VCC AS. The VCC AS establishes a call between the PSAP and the user terminal according to the latest user routing information obtained.

 The emergency call continuity information may be: emergency call continuity information set in advance on the PSAP; or the emergency call continuity information obtained by the PSAP according to the emergency user identifier to query the HSS, or the HLR, or the DM/CP where the user data is located. Or, the PSAP obtains emergency call continuity information obtained according to an emergency service request initiated by the UE and carrying emergency call continuity information.

 The subscription data in the network call continuity information may be downloaded to the subscription data of the emergency service call session unit when the user identification is registered, or the subscription data may be obtained by other means. The subscription data includes an initial filtering rule (iFC), and the information contained in the iFC indicates that the iFC can be used in an emergency service, and the information may be an emergency public identity (EMPU) or a wildcard form of the EMPU, and the information may also be an emergency. The service sign, for example, the emergency service call session unit uses a common public identity (PU) and iFC match, so the emergency service call session unit can identify that the current call is an emergency service to match the emergency service sign.

The source domain may be any one of an IMS domain, a CS domain, and a wireless local area network (WLAN); the destination domain may also be any one of an IMS domain, a CS domain, and a WLAN. The UE or the PSAP first initiates an emergency service request in the source domain, and the UE then switches to the destination domain as needed. When the UE or the PSAP switches between the source domain and the destination domain, the combination may be as follows: The UE or the PSAP may first be in the IMS. The domain initiates an emergency call request. When the UE needs to switch from the source domain to the destination domain, the UE can switch to any one of the IMS domain, the CS domain, and the WLAN. The UE or the PSAP can also initiate an emergency call request in the CS domain first. When switching from the source domain to the destination domain, you can switch to the IMS domain, CS Any one of the domain and the WLAN; the UE or the PSAP may also initiate an emergency call request on the WLAN first, and may switch to any one of the IMS domain, the CS domain, and the WLAN when the UE needs to switch from the source domain to the destination domain.

 The emergency service call session unit of the embodiment of the present invention includes:

 a call connection establishing module, configured to establish a call connection between the UE and the PSAP according to an emergency service request from the PSAP or the UE;

 An emergency service anchoring module for anchoring emergency services to a VCC AS in the network.

 The emergency service call session unit may further include:

 a triggering determining module, configured to determine, according to an emergency service request from the PSAP or the UE, whether the emergency service meets a condition for triggering an emergency call continuity service, and if yes, notifying the emergency service anchoring module to perform the emergency service anchoring The operation to the VCC AS.

 The trigger determination module further includes:

 An emergency call continuity information obtaining submodule, configured to obtain emergency call continuity information from the UE or the PSAP; or obtain emergency call continuity information from the emergency service request or a third party node; The emergency call continuity information acquisition sub-module obtains emergency call continuity information, and performs an operation of determining whether the emergency service satisfies a condition for triggering an emergency call continuity service.

 The emergency service anchoring module further includes:

 An anchor information obtaining submodule, configured to obtain a VCC AS address, emergency call continuity information, and/or a PSAP identifier;

 The VCC AS address is sent by the sub-module, and is used to send the VCC AS address obtained by the anchor information acquisition sub-module to the UE.

 Then, the emergency service anchoring module is configured to acquire the emergency service to the VCC AS according to the information acquired by the anchor information acquisition submodule.

The emergency service call session unit is an E-CSCF, an S-CSCF, an I-CSCF, a P-CSCF, an AGCF, a BGCF, an IBCF, an MGCF or an AS in the IMS domain; or a VMSC or a GMSC in the CS domain. Referring to FIG. 1, FIG. 1 is a schematic structural diagram of a system for implementing voice call continuity in an emergency service according to an embodiment of the present invention. The system includes a UE 101, an IMS domain emergency service call session unit 102, a CS domain emergency service call session unit 103, a VCC AS 104, and a PSAP 105.

 The UE 101 is respectively connected to the IMS domain emergency service call session unit 102 and the CS domain emergency service call session unit 103. The UE 101 first initiates an emergency service request in a domain in the IMS domain or the CS domain, where the emergency service request refers to An emergency call initiated by the UE 101.

 When the UE 101 initiates an emergency call in the IMS domain, the IMS domain emergency service call session unit 102 is connected to the UE 101, the VCC AS 104, and the PSAP 105, respectively, and anchors the emergency call to the VCC AS 104 according to the emergency call continuity information, where the IMS domain emergency service The call session unit 102 can be an emergency call session control function (E-CSCF) of the IMS domain, an inquiry call session control function (I-CSCF), a service call session control function (S-CSCF), a proxy call session control function (P- CSCF Access Gateway Control Function (AGCF), Border Gateway Control Function (BGCF), Interconnect Border Control Function (IBCF), AS or Media Gateway Control Function (MGCF).

 When the UE 101 initiates an emergency call in the CS domain, the CS domain emergency service call session unit 103 is connected to the UE 101, the VCC AS 104, and the PSAP 105, respectively, and anchors the call to the VCC AS 104 according to the emergency call continuity information; wherein the CS domain emergency service call session Unit 103 can be a visited mobile services switching center (VMSC) or a mobile gateway mobile switching center (GMSC).

 The VCC AS 104 receives emergency call anchoring from the IMS domain emergency service call session unit 102 or the CS domain emergency service call session unit 103 or PSAP 105, and the VCC AS 104 routes the emergency service request initiated by the UE 101 to the PSAP 105 in a proxy or redirect manner. Or routing the emergency service request initiated by the PSAP 105 to the UE 101, which is responsible for completing the control function of the emergency call continuity service. When the UE 101 switches between the IMS domain and the CS domain, the VCC AS 104 finds the anchored session, the proxy UE 101 renegotiates with the PSAP 105, establishes a new access, and releases the session resources in the source domain to implement an emergency call in the IMS. Switching between domain and CS domain.

The PSAP 105 is connected to the IMS domain emergency service call session unit 102, the CS domain emergency service call session unit 103, and the VCC AS 104, respectively. Can receive a call request initiated by the UE 101 and save emergency call continuity information; at the same time, the PSAP 105 can initiate an emergency user to the UE 101. Identify urgent business requests. When the UE 101 registers, the emergency user identifier is a user identifier, including a Session Initiation Protocol (SIP) Uniform Resource Identifier (URI) or a Telephone (TEL) URI, or when the UE 101 is not registered, the emergency user identifier is the UE 101 in the IMS domain. The assigned temporary emergency public user ID. When the PSAP 105 initiates an emergency service request to the UE 101, the emergency service request carries emergency call continuity information, and the emergency service call session unit 102 or 103 anchors the emergency service to the VCC AS 104 of the UE home domain, and routes the emergency service to The UE 101 establishes a call connection between the PASP 105 and the UE 101.

 The UE 101 or the PASP 105 initiates a call request in any of the IMS domain and the CS domain. If the UE 101 or the PASP 105 first initiates an emergency call to the IMS domain emergency service call session unit 102, the IMS domain emergency service call session unit 102 acts as the emergency service of the source domain. The call session unit, the CS domain emergency service call session unit 103 serves as the emergency service call session unit of the destination domain; after the UE 101 switches from the IMS domain to the CS domain, the UE 101 then initiates an emergency call request to the CS domain emergency service call session unit 103. If the UE 101 or the PASP 105 first initiates an emergency call to the CS domain emergency service call session unit 103, the CS domain emergency service call session unit 103 acts as the emergency service call session unit of the source domain, and the IMS domain emergency service call session unit 104 serves as the emergency of the destination domain. Business call session unit. After the UE 101 switches from the IMS domain to the CS domain, the UE 101 then initiates an emergency call request to the IMS domain emergency service call session unit 102.

 Referring to Figure 2, Figure 2 is a flow chart showing the continuity of voice calls during emergency services in accordance with a first preferred embodiment of the present invention. In this embodiment, the UE 101 first initiates an emergency service request in the IMS domain, and then the UE 101 switches to the CS domain as needed; the E-CSCF, the MGCF, and the I/S-CSCF of the IMS domain serve as the IMS domain emergency call session unit 102, the CS domain. The VMSC serves as the CS domain emergency service call session unit 103, and the IMS domain serves as the source domain of this embodiment. The CS serves as the destination domain of this embodiment. The implementation of this business consists of the following steps:

 Step 201: The UE 101 initiates an emergency call request to the E-CSCF of the IMS domain in the IMS domain.

 In this step 201, the emergency call request may carry emergency call continuity information.

Step 202: The E-CSCF of the IMS domain determines, according to the obtained emergency call continuity information, whether the service meets the condition for triggering the call continuity service, and if yes, executing step 203; The process of urgently calling a continuous business.

 The method for obtaining emergency call continuity information includes: the emergency service call session unit acquires emergency call continuity information from the UE 101 or the PSAP 105, or obtains emergency call continuity information from the emergency service request; or, the E-CSCF of the IMS domain The emergency call continuity information is directly or indirectly obtained by the HSS, the HLR or the DM/CP server, or the UE 101 can report the terminal call continuity information and the network call continuity information to the emergency service call session unit 102 in the form of a message.

 The emergency call continuity information mentioned above includes explicit emergency service information and/or terminal call continuity information;

 Further, the emergency call continuity information may further include network call continuity information obtained by querying a user subscription database.

 The explicit emergency service information includes an emergency service indication, an emergency user identifier, an emergency number, etc., and the terminal call continuity information includes at least one of a terminal capability, a user preference, and a VCC AS address; and the network call continuity information includes at least a roaming state. One of the access network type and subscription data.

 In the IMS domain, if an emergency call is routed to the E-CSCF of the IMS domain, the emergency call continuity information is implicit emergency service information.

 The subscription data is the subscription data of the UE 101 that initiates the emergency service request, and includes at least one of the following: the subscription data of the emergency user identifier of the UE carrying the signed VCC service information, and the UE carrying the contracted VCC service information. The subscription data of the common public identity of the emergency user identity and the emergency user identity of the UE carrying the contracted VCC service information conform to the subscription data in the wildcard form. The iFC is included in the subscription data, the EMPU carried in the iFC, the wildcard form of the EMPU, or the emergency service sign indicates that the iFC can be used in emergency services, the iFC can be downloaded during emergency registration, or during normal registration. download. If the UE is a registered UE, the subscription information can be downloaded to the emergency service call session unit.

The emergency user identifier mentioned in the previous paragraph, when the UE registers, the emergency user identifier includes a public user identifier, and the public user identifier includes a SIP URI or a TEL URI; when the UE is not registered, the emergency user identifier may further include a temporary emergency public user identifier. The temporary emergency public user identifier is an emergency public user identifier temporarily allocated when an emergency call is initiated in the IMS domain, and the emergency user identifier may be a SIP URI or TEL URL

 The E-CSCF of the IMS domain determines, according to the emergency call continuity information, whether the service satisfies the condition for triggering the call continuity service, and the determining manner includes: the E-CSCF of the IMS domain judges according to the explicit emergency service information or the implicit emergency service information. Whether the service satisfies the condition for triggering the call continuity service; further includes: according to explicit emergency service information and terminal call continuity information; or explicit emergency service information and network call continuity information; or implicit emergency service information and Terminal call continuity information; or implicit emergency service information and network call continuity information; or explicit emergency service information, network call continuity information, and terminal call continuity information; or implicit emergency service information, network call The continuity information and the terminal call continuity information determine whether the service satisfies the condition for triggering the call continuity service.

 Step 203: The E-CSCF of the IMS domain routes the emergency call to the VCC AS 104, thereby anchoring the call to the designated VCC AS 104, and the VCC AS 104 routes the request to the PSAP 105 in a proxy or redirected manner.

 In this embodiment, the VCC AS address may be obtained by using any one of the following methods: The address of the VCC AS 104 is configured in advance on the UE 101;

 The UE obtains and saves the address of the pre-delivered VCC AS 104 from the network when the emergency service request is initiated. In step 201, the UE 104 carries the address of the VCC AS 104 in the initiated emergency service request.

 Query the third-party node to obtain the address of the VCC AS 104;

 The address of the VCC AS 104 is obtained from the terminal call continuity information or the network call continuity information. The E-CSCF of the IMS domain anchors the emergency service request to the VCC AS 104 based on the obtained VCC AS address. Among them, the third-party nodes can be HSS, HLR, DM/CP

When the UE 101 is in the IMS domain, the address of the VCC AS 104 is returned to the UE 101 in the form of a short message, an instant message or a subscription notification by the VCC AS 104, the HSS, the HLR, the DM/CP server or the E-CSCF of the IMS domain. Or the VCC AS address is carried in the response to the registration or call of the UE 101 in advance; when the UE 101 is in the CS domain, the address of the VCC AS 104 is pre-connected in the response message ANM. It is carried in the received number or returned to the UE 101 in the form of a short message.

 Alternatively, the VCC AS address is configured in advance on the E-CSCF of the IMS domain, and the E-CSCF of the IMS domain anchors the emergency service request to the VCC AS 104 according to the VCC AS address configured by itself.

 For the implementation of this step, see 3-5 in Figure 2a. The E-CSCF of the IMS domain puts the VCC AS 104 and its own address into the Route header field, and forwards the call request to the selected VCC AS 104. Call to the anchor of the selected VCC AS 104. The VCC AS 104 then sends an invitation to the E-CSCF of the IMS domain (invite M message to route the request back to the E-CSCF of the IMS domain, and then the E-CSCF of the IMS domain routes the emergency call request to the PSAP 105.

 Step 204, establishing a session connection between the UE 101 and the PSAP 105.

 See 6-14 in Figure 2a for specific steps. The PSAP 105 first performs Session Description Protocol (SDP) media negotiation with the UE 101, and the PSAP 105 transmits session establishment information to the E-CSCF of the IMS domain, and then transmits the session establishment information to the VCC AS 104 and the UE by the E-CSCF of the IMS domain. 101, and receiving their acknowledgment message, the E-CSCF of the IMS domain finally sends an acknowledgment message to the PSAP 105 to establish a call with the PSAP 105.

 Step 205, the VCC AS 104 returns its address to the UE 101.

 In this step, the VCC AS 104 notifies the UE 101 of its address in the form of a short message, an instant message or a subscription notification, or carries its address back to the UE 101 in the anchored session response message, and is saved by the UE 101. The PSAP 105 saves emergency call continuity information including the VCC AS address; when the UE 101 is an unregistered UE, the VCC AS 104, HSS, HLR, DM/CP server or emergency service call session unit 102 holds the UE 101 Routing information.

 Step 206: When the UE 101 determines that it needs to switch to the CS domain, it initiates a call request to the VMSC of the CS domain.

 For details, refer to 15-16 in Figure 2a. In this step, the UE 101 determines that the emergency call needs to be handed over to the CS domain due to the deterioration of the wireless environment or other reasons. The UE 101 uses the address of the VCC AS 104 in the CS domain. A call request is initiated for the called number.

 Step 207: The VMSC of the CS domain routes the handover request to the VCC AS 104.

The specific operation is completed by 17-19 in Figure 2a, first forwarded by the VMSC of the CS domain to the MGCF. The initial address message (IAM), the MGCF then routes the emergency call to the I/S-CSCF of the IMS domain with the invite message, and finally routes the emergency call to the VCC AS 104 by the I/S-CSCF of the IMS domain.

 The handover request is a handover request carrying an emergency service indication, indicating that the handover is an emergency call handover. The handover request may be: carrying an emergency indication handover request in a message header field, a parameter field or a message body of the handover request; carrying an emergency in a VCC domain handover number (VDN) and/or a VCC handover uniform resource identifier (VDI) number The handover request of the service indication; or the handover request carrying the emergency call continuity information of the emergency service indication.

 Step 208, the VCC AS 104 finds the anchored session, and the proxy UE 101 and the PSAP 105 re-negotiate. After the negotiation is completed, the CS domain access part call setup is completed.

 For the specific process, refer to 20-28 in Figure 2a. The method for the VCC AS 104 to find an anchor session in this embodiment is as follows:

 In step 203, the E-CSCF of the IMS domain has anchored the emergency call carrying the emergency subscriber identity to the VCC AS 104, which is the emergency subscriber identity described in step 201. In this step 208, the VCC AS 104 finds the anchored session based on the emergency user identity; or the VCC AS 104 finds the anchored session based on the anchor index it sends to the UE 101 and is held by the UE 101. The VCC AS 104 may carry the anchor index to the UE 101 in the form of a short message or an instant message or a subscription notification or in the anchored session response message, and are saved by the UE 101, the anchor described here. The index is the index identifier. And the latest emergency user identity is saved by one of the PSAP 105 and the VCC AS 104 or both.

The specific operation of the VCC AS 104 to find an anchored session according to the emergency user identity is as follows: When the UE 101 is a registered UE, the emergency user identity is a public user identity, including a SIP URI or a TEL URI, and the VCC AS 104 finds an anchor according to the user identity. The scheduled session. When the UE 101 is an unregistered UE, the emergency user identity is a temporary emergency public user identity assigned to the UE 101 in the IMS domain, which may be a SIP URI or a TEL URI. When the temporary emergency public user identity is a TEL URI, the VCC AS 104 finds the anchored session based on the emergency public user identity, or the VCC AS 104 assigns an anchor index number on the VCC AS 104 for this call and returns to the UE 101. The VCC AS 104 finds the anchored session based on the index number and records the route of the handover request; when the temporary emergency public user identity is a SIP URI, VCC The AS 104 assigns an anchor index number on the VCC AS 104 for this call and returns it to the UE 101, which finds the anchored session based on the index number. The UE in the destination domain of the VCC AS 104 and the PSAP 105 establish a call connection or establish a call connection, and the VCC AS 104, HSS, HLR, DM/CP server or CS domain emergency service call session unit 103 saves the destination domain. Routing information for UE101.

 In this embodiment, the VCC AS 104 proxy UE 101 and the PSAP 105 negotiate, and the implementation process of reestablishing the call connection is:

 The VCC AS 104 proxy UE 101 re-initiates the call request to the PSAP 105, and receives the session establishment information of the PSAP 105, and the VCC AS 104 sends the session establishment information to the MGCF through the I/S-CSCF of the IMS domain;

 The MGCF sends the session establishment information to the VMSC. After receiving the session establishment information, the VMCS sends the connection request information to the UE 101, the UE 101 returns the acknowledgement information, and finally sends the acknowledgement information to the VCC AS 104, thereby establishing the UE 101 and The PSAP 105 is connected to the call in the CS domain.

 Step 209, the VCC AS 104 releases the session resources of the UE 101 in the IMS domain.

 For details, refer to 29-30 in Figure 2a. The VCC AS 104 sends a BYE message to the E-CSCF of the IMS domain, and then forwards the BYE message to the UE 101 by the E-CSCF of the IMS domain to notify the UE 101 of the IMS domain. The session ends.

 Referring to FIG. 3, FIG. 3 is a flowchart of implementing voice call continuity in an emergency service according to a second preferred embodiment of the present invention. The PSAP 105 first initiates an emergency service request to the UE 101 of the IMS domain in the IMS domain, and the emergency service request is an emergency call request or a callback request for an emergency call. When the UE 101 determines that the emergency call needs to be handed over to the CS domain according to the wireless environment, the PSAP 105 re-establishes an emergency call connection with the UE 101 in the CS domain in the CS domain; wherein, the E/S-CSCF, MGCF, I/S- of the IMS domain The CSCF serves as the IMS domain emergency service call session unit 102, and the VMSC of the CS domain serves as the CS domain emergency service call session unit 103. The IMS domain serves as the source domain of this embodiment, and the CS serves as the destination domain of this embodiment.

 Step 301: The PSAP 105 initiates an emergency service request to the E/S-CSCF of the IMS domain in the IMS domain, where the emergency service request is an emergency call request or a callback request of the emergency call.

Step 302: Acquire emergency call continuity information by the E/S-CSCF of the IMS domain, according to the emergency call The continuity information is used to determine whether the service satisfies the condition for triggering the call continuity service. If yes, step 303 is performed; otherwise, the process of triggering the call continuity service is ended.

 In this step, the E/S-CSCF obtains emergency call continuity information, including: the E/S-CSCF of the IMS domain obtains emergency call continuity information from the emergency service request initiated by the PSAP 105; or, the E of the IMS domain - The CSCF obtains emergency call continuity information directly or indirectly from the subscriber subscription database or the DM/CP server.

 Prior to the PSAP 105 initiating an emergency service request, the PSAP 105 needs to first obtain emergency call continuity information. The method for obtaining emergency call continuity information by the PSAP 105 includes: setting emergency call continuity information on the PSAP 105 in advance, or the PSAP 105 obtaining emergency call continuity information from an emergency service request initiated by the UE 101, or the PSAP 105 The emergency call continuity information is obtained by querying the HSS, HLR, and DM/CP servers where the user data is located according to the user identifier; or the emergency call continuity information is obtained in a manner that can be thought of by those skilled in the art.

 In this step 302, the E/S-CSCF of the IMS domain determines whether the immediate service satisfies the condition for triggering the call continuity service condition, and the E-CSCF of the IMS domain described in step 202 determines whether the service satisfies the triggering call continuity. The method of business conditions is exactly the same.

 Step 303: The E/S-CSCF of the IMS domain routes the emergency service request to the VCC AS 104, thereby anchoring the call to the selected VCC AS 104; the VCC AS 104 routes the emergency service request to the proxy or redirected manner to UE 101.

 In this step 303, the E/S-CSCF of the IMS domain anchors the callback request of the emergency call request or the emergency call to the VCC AS 104 as follows: The E/S-CSCF obtains emergency call continuity information and/or the PSAP 105. Identify and anchor emergency services to VCC AS 104 based on emergency call continuity information or PSAP 105 identification.

 The E/S-CSCF of the IMS domain anchors the emergency traffic to the VCC AS 104 based on the emergency call continuity information containing the emergency subscriber identity.

 When the emergency service request initiated by the PSAP 105 is an emergency call request, the E-CSCF of the IMS domain anchors the emergency call request to the VCC AS 104 based on the emergency call continuity information.

When the emergency service request initiated by the PSAP 105 is a callback request for an emergency call, the IMS domain The specific operation of the E-CSCF to the VCC AS 104 anchoring is: when the UE 101 is a registered UE, the emergency user identifier is a user identifier, including a SIP URI or a TEL URI, and the E/S-CSCF of the IMS domain queries according to the user identifier. The user subscription database obtains the VCC AS address subscribed by the user, anchors the emergency service between the PSAP 105 and the UE 101 to the home domain VCC AS 104 to which the user subscribes, and then routes the emergency service to the UE 101; when the UE 101 is not When registering the UE, the emergency user identity is a temporary emergency public user identity assigned to the UE 101 in the IMS domain, including a SIP URI or a TEL URI, and the E/S-CSCF of the IMS domain will be based on the VCC AS address obtained in the emergency call. The emergency service is anchored to the VCC AS 104, and the routing information between the UE 101 and the VCC AS 104 stored in the callback routing information unit is routed to the UE 101. In this embodiment, the callback routing information unit refers to the VCC AS 104. HSS, HLR, DM/CP server or emergency service call session unit 102. The VCC AS 104 assigns an index number on the VCC AS 104 to the emergency service according to the temporary emergency public user identity assigned to the UE 101, and returns it to the UE 101 for saving. The VCC AS 104 routes the callback request of the emergency call according to the routing information. UE 101.

 When the routing information of the UE 101 is saved by the VCC AS 104, the VCC AS 104 routes the callback information of the emergency call to the UE 101 according to the saved routing information of the UE 101; when the routing information of the UE 101 is by the HSS When the HLR, the DM/CP server, or the emergency service call session unit is saved, the VCC AS 104 may obtain the routing information of the UE 101 from the HSS, the HLR, the DM/CP server, or the emergency service call session unit in the emergency call callback, according to The routing information of the UE 101 routes the callback of the emergency call to the UE 101; the routing information is the destination domain information after the UE 101 switches.

 The subsequent steps 304 to 309 are basically the same as all the descriptions of the steps 204 to 209 in the first embodiment except that the E-CSCF of the IMS domain is replaced with the E/S-CSCF of the IMS domain.

 See Figure 3a for details.

Referring to FIG. 4, FIG. 4 is a flowchart of implementing voice call continuity in an emergency service according to a third preferred embodiment of the present invention. In this embodiment, the UE 101 initiates an emergency call service in the CS domain, anchors the session with the PSAP 105 to the VCC AS 104, and when the UE 101 moves to the IMS domain, the VCC AS 104 proxyes the UE 101 to initiate a new call to the PSAP 105. Session connection, E/S-CSCF, MGCF, I/S-CSCF of the IMS domain as the IMS domain emergency service call session unit 102, and the VMSC of the CS domain as the CS domain emergency service call It is called the session unit 103, the CS domain is used as the source domain of this embodiment, and the IMS is used as the destination domain of this embodiment. The steps to achieve are as follows:

 Step 401: The UE 101 initiates an emergency call request to the VMSC of the CS domain in the CS domain.

 In this step 401, the emergency call request may carry emergency call continuity information.

 Step 402: The VMSC in the CS domain determines, according to the obtained emergency call continuity information, whether the service meets the condition for triggering the call continuity service, and if yes, performs step 403; otherwise, ends the process of triggering the call continuity service.

 The method in which the VMSC of the CS domain obtains emergency call continuity information and determines whether the service satisfies the condition for triggering the call continuity service is exactly the same as the corresponding method in step 202.

 Step 403: As described in step 207, the VMSC of the CS domain anchors the call to the VCC AS 104 by means of a special prefix or the like, and the VCC AS 104 routes the emergency call request to the PSAP 105 in a proxy or redirect manner.

 For details, refer to steps 3-5 in Figure 4a. The VMSC in the CS domain first routes the emergency call request to the VCC AS 104 through the MGCF of the IMS domain and the I/S-CSCF of the IMS domain, and anchors the emergency call to the designated VCC. AS 104.

 The case of anchoring the emergency call to the designated VCC AS 104 mentioned in the previous paragraph is exactly the same as the implementation of the VCC AS 104 anchoring in step 203, except that in this step the emergency is completed by the VMSC of the CS domain. The call is anchored to the operation of the VCC AS 104.

 Step 404, similar to step 208, establishing a session connection between the UE 101 and the PSAP 105. For the specific implementation process of step 404, refer to 6-14 in FIG. 4a. The technology for establishing a session connection between the UE 101 and the PSAP 105 is prior art, so the can be described as: VCC AS 104 initiates an emergency call request to the PSAP 105. After receiving the emergency call request, the PSAP 105 performs SDP media negotiation with the MGCF of the IMS domain, and sends the session establishment information to the VCC AS 104. Finally, the I/S-CFCS and VCC AS 104 of the IMS domain return confirmation information to the PSAP 105 to establish a call connection between the PSAP 105 and the UE 101, while the PSAP 105 maintains emergency call continuity information.

 Step 405, VCC AS 104 returns its address to UE 101.

The address of the VCC AS 104 can be notified to the UE 101 by means of an instant message or the like, and is advanced by the UE 101. Line save, while PSAP 105 saves emergency call continuity information including VCC AS 104 address; VCC AS 104, HSS, HLR, DM/CP server or emergency service call session unit when UE 101 is unregistered UE 101 The routing information of the UE 101 is saved.

 Step 406: In the same manner as step 206, when the UE 101 determines that it needs to switch to the IMS domain, it initiates an emergency call request to the I/S-CSCF of the IMS domain.

 For the implementation of this step 406, refer to 15-16 in FIG. 4a. When the UE 101 determines that the call needs to be handed over to the IMS domain according to the wireless environment, the UE 101 initiates the call to the I/S-CFCS of the IMS domain with the VCC AS 104 address as the called number. Emergency call request.

 Step 407: The I/S-CSCF of the IMS domain routes the handover request to the VCC AS 104.

 Step 408, the VCC AS 104 finds the anchored session, and re-establishes the UE 101 with the IMS domain.

The call connection of the PSAP 105.

 For the specific operation of step 408, see 18-21 in FIG. 4a, the VCC AS 104 finds the anchored session. The method for the VCC AS 104 to find the anchor session in this step is: VCC AS 104 is found by registering the user identifier of the UE 101. The anchored session; or the VCC AS 104 finds the anchored session based on the anchor index it sends to the UE 101 and is held by the UE 101, the anchor index being an index identifier.

 The VCC AS 104 proxy UE 101 re-initiates a session request to the PSAP 105. After receiving the request, the PSAP 105 notifies the UE 101 through the VCC AS 104 and the I/S-CSCF of the IMS domain to establish the UE 101 and The call connection between the PSAPs 105; after establishing the call connection or after establishing the call connection, when the UE 101 is the unregistered UE 101, the VCC AS 104, HSS, HLR, DM/CP server or emergency service call session unit saves the IMS domain Routing information of the UE 101 in the middle.

 Step 409, the VCC AS 104 releases the session resources of the UE 101 in the CS domain.

 The VCC AS 104 releases the session resources of the UE 101 in the IMS domain. Referring to 22-24 in FIG. 4a, the VCC AS 104 sends the BYE information to the I/S-CSCF in the IMS domain, and the I/S-CSCF of the IMS domain will be the BYE. The information informs the MGCF of the IMS domain that the MGCF of the IMS domain sends the release (REL) information to the VMSC of the CS domain after receiving the BYE information, and finally the VMSC of the CS domain notifies the UE 101 of the REL information, thereby releasing the session resources of the UE 101 in the CS domain. .

See Figure 4a for specific operations. Referring to FIG. 5, FIG. 5 is a flowchart of implementing voice call continuity in an emergency service according to a fourth preferred embodiment of the present invention. In this embodiment, the PSAP 105 initiates an emergency service request to the UE 101 of the CS domain, and the emergency service request is an emergency call request or a callback request for an emergency call, and the session with the PSAP 105 is anchored to the VCC AS 104, when the UE After moving to the IMS domain, the VCC AS 104 proxy UE 101 initiates a new session connection to the PSAP 105, and the E/S-CSCF, MGCF, I/S-CSCF of the IMS domain acts as the IMS domain emergency service call session unit 102, CS. The VMSC of the domain serves as the CS domain emergency service call session unit 103, and the CS domain serves as the source domain of this embodiment. The IMS serves as the destination domain of this embodiment. The steps implemented by this method are as follows:

 Step 501: The PSAP 105 initiates an emergency service request to the S-CSCF of the IMS domain, where the emergency service request is a callback request for the emergency call request for the emergency call.

 Step 502: The S-CSCF of the IMS domain determines, according to the obtained emergency call continuity information, whether the service meets the condition for triggering the call continuity service, and if yes, performs step 503; otherwise, ends the process of triggering the call continuity service.

 In this step 502, the method for obtaining the emergency call continuity information by the S-CSCF of the IMS domain is exactly the same as the method for obtaining the emergency call continuity information of the E/S-CSCF of the IMS domain described in step 302.

 The method for obtaining emergency call continuity information by the S-CSCF of the IMS domain is the same as that described in step 302.

 The S-CSCF of the IMS domain determines whether the service satisfies the condition for triggering the call continuity service. The method for determining whether the service meets the condition for triggering the call continuity service is the same as the E-CSCF of the IMS domain described in step 202.

 Step 503: The S-CSCF of the IMS domain routes the emergency service to the VCC AS 104, thereby implementing anchoring of the emergency service on the designated VCC AS 104, and the VCC AS 104 routes the emergency service request to the UE in a proxy or redirect manner. 101.

 The method of anchoring the emergency service to the VCC AS 104 by the E/S-CSCF of the IMS domain is the same as that described in step 303.

 Step 504, establishing a session connection between the PSAP 105 and the UE 101.

The step of establishing a session connection between the PSAP 105 and the UE 101 is prior art content, here Just for the tube to introduce. Referring to 3-14 in FIG. 5a, the VCC AS 104 receives the emergency call request from the S-CSCF, and the VCC AS 104 address can be notified to the UE 101 in the form of a short message, an instant message, etc., and the UE 101 sends the response message to FIG. 5a. 6-11 is sent to the PSAP 105. After receiving the session establishment information, the PSAP 105 sends an acknowledgement message to the S-CSCF, and finally sends the response message to the VCC AS 104 and the MGCF via 13, 14, respectively, in FIG. 5a, thereby establishing a PSAP. A session with the UE 101.

 Steps 505 to 509 are exactly the same as all the descriptions of steps 405 to 409 except that the I/S-CSCF of the IMS domain shown in FIG. 4a is replaced with the S-CSCF of FIG. 5a, and the S-CSCF is used as the IMS domain. Emergency service call session unit.

 In all of the above embodiments, the IMS domain and the CS domain are taken as the source domain or the destination domain, respectively. In the embodiment shown in FIG. 1, the IMS domain emergency service call session unit 102 and the CS domain are urgent. Any one of the service call session units 103 is an emergency service call session unit of the source domain. When the UE 101 switches from the source domain to the destination domain, the IMS domain emergency service call session unit 102 and the CS domain emergency service call session unit 103 Either one can call the session unit for the emergency service of the destination domain. In the embodiment shown in FIG. 2, the UE 101 uses the IMS domain as the source domain for initiating an emergency call request, and the CS domain serves as the handover destination domain. In the embodiment shown in FIG. 3, the PSAP 105 initiates the UE 101 in the IMS domain. The emergency service request, the IMS domain is the source domain, and the CS domain is the destination domain of the handover. In the embodiment shown in FIG. 4, the UE 101 uses the CS domain as the source domain for initiating the emergency call request, and the IMS domain serves as the handover destination domain. In the embodiment shown in FIG. 5, the PSAP 105 initiates an emergency service request to the UE 101 in the CS domain, the CS domain being the source domain and the IMS domain being the destination domain of the handover.

 In addition to the above, other cases include: IMS domain as the source domain and IMS domain as the destination domain; or IMS domain as the source domain and WLAN as the destination domain; or CS domain as the source domain and CS domain as the source domain Or the WLAN as the destination domain, or the WLAN as the source domain, and the IMS domain as the destination domain; or the WLAN as the source domain and the CS domain as the destination domain; or WLAN as the source domain. The case where the WLAN is used as the destination domain is basically the same as the execution method described in the above embodiment, and is not described here.

 In summary, the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention.

Claims

Claim A method for implementing voice call continuity in handling emergency services, the method comprising:  The public safety access point PSAP or the user terminal UE in the source domain initiates an emergency service request; the network side anchors the emergency service to the voice call continuity VCC application server AS, establishing the UE between the source domain and the PS AP Call connection  The VCC AS implements voice call continuity services based on the anchored emergency services.  The method according to claim 1, wherein the initiating an emergency service request by the PSAP or the UE in the source domain includes:  The UE in the source domain initiates an emergency service request to the PSAP, or the PSAP initiates an emergency service request to the UE in the source domain.  The method according to claim 1, wherein the network side before the step of anchoring the emergency service to the voice call continuity VCC application server AS further comprises: determining, by the network side, whether the emergency service satisfies the trigger The condition of the emergency call continuity service, and if so, the subsequent steps are performed.  The method according to claim 3, wherein the determining, by the network side, whether the emergency service meets the condition for triggering the emergency call continuity service further comprises: acquiring, by the network side, emergency call continuity information;  The network side determines whether the emergency service meets the condition for triggering the emergency call continuity service: the network side determines, according to the obtained emergency call continuity information, whether the emergency service meets the condition for triggering the emergency call continuity service.  5. The method according to claim 4, wherein the step of obtaining emergency call continuity information by the side comprises:  The network side obtains emergency call continuity information from the UE or the PSAP;  Or, the network side obtains emergency call continuity information from the emergency service request; Alternatively, the network side obtains emergency call continuity information from a third party node. 6. The method according to claim 5, wherein the third party node is: a home subscriber server, a local location register or a device management/client provisioning DM/CP server.  The method according to claim 4, wherein the PSAP further includes: the PSAP acquiring emergency call continuity information before initiating an emergency service request to the UE in the source domain;  Then, the emergency service request initiated by the PSAP to the UE in the source domain is an emergency call request or a callback request of the emergency call.  8. The method according to claim 7, wherein the step of obtaining emergency call continuity information by the PSAP comprises:  The PSAP obtains emergency call continuity information set in advance on the PSAP; or the PSAP queries the home subscriber server where the UE data is located according to the emergency user identifier. The HSS or the home location register HLR or the DM/CP server obtains emergency call continuity information; or the PSAP obtains the emergency call continuity information according to an emergency service request initiated by the UE and carrying emergency call continuity information.  9. The method according to claim 1, wherein the source domain is any one of an IP Multimedia Subsystem IMS, a Circuit Switched CS, and a Wireless Local Area Network WLAN.  The method according to any one of claims 1 to 9, wherein the step of the network side anchoring the emergency service request to the VCC AS comprises:  The network side obtains the VCC AS address, the emergency call continuity information, and/or the PSAP identifier, and anchors the emergency service to the VCC AS according to the obtained VCC AS address, emergency call continuity information, and/or PSAP identifier.  The method according to claim 10, wherein the emergency service request is initiated by the UE, and the emergency service request initiated by the UE carries the VCC AS address;  Then, the network side obtains the VCC AS address as follows: The network side acquires the VCC AS address in the emergency service request. The method according to claim 11, wherein, before the UE initiates an emergency service request, the method further includes: configuring an address of the VCC AS on the UE; or sending, by the network side, the VCC AS address to the UE. The method according to claim 10, wherein the acquiring, by the network side, the VCC AS address comprises:  The network side queries a third-party node to obtain an address of the VCC AS.  Or, the network side obtains the address of the locally configured VCC AS.  The method according to any one of claims 1 to 9, wherein the establishing the call connection between the UE in the source domain and the PSAP further comprises: sending the VCC AS address to the UE for saving .  The method according to any one of claims 1 to 9, wherein, when the UE is not registered, the network side anchors the emergency service to the VCC AS according to the emergency call continuity information, further comprising: The callback routing information unit saves the routing information of the UE.  The method according to any one of claims 1 to 9, wherein when the UE needs to switch to the destination domain, the VCC AS implements a voice call continuity service according to the anchored emergency service:  The UE initiates a handover request by using the obtained VCC AS address as the called number.  After receiving the handover request, the VCC AS finds the anchored session, and the proxy UE and the PSAP re-negotiate, and establish a call connection in the destination domain after the negotiation is completed.  17. The method according to claim 16, wherein the VCC AS finds the anchored session as: The VCC AS finds the anchored session according to the emergency user identity or the anchor index.  18. The method according to claim 16, wherein the handover request is a handover request carrying an emergency service indication.  The method according to claim 16, wherein during or after the VCC AS proxy UE and the PSAP establish a call connection in the destination domain, the method further comprises: when the UE is not registered, saving the destination by the callback routing information unit. Routing information of the UE in the domain. An emergency service call system, the system includes: a UE, a PSAP, and a VCC AS. The system further includes an emergency service call session unit in a source domain where the UE is located, where the UE is configured to initiate an emergency call. An emergency service request for continuity information to the PSAP, and a handover request from the source domain to the destination domain to the VCC AS; The emergency service call session unit is configured to anchor the emergency service request to the VCC AS, and establish a call connection between the UE and the PSAP;  The VCC AS is configured to anchor the emergency service according to the handover request sent by the UE, and the proxy UE establishes a call connection with the PSAP in the destination domain, and releases the session resources of the UE in the source domain.  The system according to claim 20, wherein the PSAP is configured to initiate an emergency service request carrying emergency call continuity information to the UE.  22. The system according to claim 20, wherein the system further comprises: an emergency service call session unit in the destination domain, configured to route the handover request sent by the UE to 23. A system according to claim 20, 21 or 22, characterized in that  When the source or destination domain is an IMS domain, the emergency call session unit is: E-CSCF, S-CSCF, I-CSCF, P-CSCF, AGCF, BGCF, IBCF, MGCF or AS.  24. A system according to claim 20, 21 or 22, characterized in that  When the source or destination domain is a CS domain, the emergency call session unit is a VMSC or a GMSC.  An emergency service call session unit, wherein the emergency service call session unit comprises:  a call connection establishing module, configured to establish a call connection between the UE and the PSAP according to an emergency service request from the PSAP or the UE;  An emergency service anchoring module for anchoring emergency services to a VCC AS in the network.  The emergency service call session unit according to claim 25, wherein the emergency service call session unit further comprises:  a triggering determining module, configured to determine, according to an emergency service request from the PSAP or the UE, whether the emergency service meets a condition for triggering an emergency call continuity service, and if yes, notifying the emergency service anchoring module to perform the emergency service anchoring The operation to the VCC AS. The emergency service call session unit according to claim 25, wherein the trigger determination module further comprises: An emergency call continuity information obtaining submodule, configured to obtain emergency call continuity information from the UE or the PSAP; or obtain emergency call continuity information from the emergency service request or a third party node; The emergency call continuity information acquisition sub-module obtains emergency call continuity information, and performs an operation of determining whether the emergency service satisfies a condition for triggering an emergency call continuity service.  The emergency service call session unit according to claim 25, wherein the emergency service anchoring module further comprises:  An anchor information obtaining submodule, configured to obtain a VCC AS address, emergency call continuity information, and/or a PSAP identifier;  Then, the emergency service anchoring module is configured to acquire the emergency service to the VCC AS according to the information acquired by the anchor information acquisition submodule.  The emergency service call session unit according to claim 28, wherein the emergency service anchoring module further comprises:  The VCC AS address is sent by the sub-module, and is used to send the VCC AS address obtained by the anchor information acquisition sub-module to the UE.  The emergency service call session unit according to any one of claims 25 to 29, wherein the emergency service call session unit is an E-CSCF, an S-CSCF, an I-CSCF, a P- in an IMS domain. CSCF, AGCF, BGCF, IBCF, MGCF or AS; or, is a VMSC or GMSC in the CS domain.