CN101227648B - Method for implementing IP multimedia subsystem urgent call business - Google Patents

Abstract

A method for implementing an emergency call service of an IP multimedia subsystem. After receiving a session invitation request for a call initiated by a user equipment, the proxy call session control function P-CSCF checks the call attribute to determine the call type and session type of the call; If the P-CSCF determines that the call is an emergency call and is an IP Multimedia Subsystem Centralized Service ICS session, then return a replacement service response to the user equipment, and include an emergency call indication in the response, and notify the user equipment The call is an emergency call; after receiving the replacement service response, the user equipment initiates a new emergency call from the IP Multimedia Subsystem IMS domain or circuit domain. The invention overcomes the defect that the emergency call service cannot be realized because the ICS UE cannot determine the emergency call, and achieves the purpose of realizing the emergency call service.

Description

Realization Method of Emergency Call Service in IP Multimedia Subsystem

technical field

The invention relates to the communication field, in particular to a method for realizing an emergency call service of an IP multimedia subsystem.

Background technique

According to government regulations, telecommunications networks must be able to provide emergency voice calling services. When the user dials the emergency call number, or uses the default emergency call number stored in the terminal device, or uses the emergency call identifier to initiate an emergency call, the network will connect the emergency call to the local emergency communication reception center, such as police, fire, medical rescue, rescue etc.

An IP (Internet Protocol, Internet Protocol) multimedia subsystem (IP Multimedia CoreNetwork Subsystem, referred to as IMS) must also provide an emergency call service.

Figure 1 is a system reference framework for IMS emergency calls. The whole framework includes User Equipment (UE for short) 101, Proxy Call Session Control Function (P-CSCF for short) 102, Serving Call Session Control Function (S-CSCF for short) 103, attribution Home Subscriber Server (HSS for short) 104, Emergency Call Session Control Function (E-CSCF for short) 105, Location Retrieval Function (LRF for short) 106 and Public Safety Answering Point , referred to as PSAP) 107, in addition, the session process also involves the Interconnection Border Control Function (Interconnection Border Control Function, referred to as IBCF), query call session control function (Interrogating Call Session Control Function, referred to as I-CSCF), media gateway control function (Media Gateway Control Function, referred to as MGCF), media gateway (MediaGateway, referred to as MGW) and other functional entities (not shown in the figure).

Among them, E-CSCF 105 is a new functional entity introduced in the IMS domain, which is located in the same network as P-CSCF 102 (it is the user's visited network when the user roams), and is responsible for receiving emergency sessions from P-CSCF 102 Establish a request, according to the location information provided by the user or the location information and routing information obtained from the LRF 106, the emergency session establishment request is routed to the emergency communication acceptance center 107 connected to the IP network through the Mm interface, or routed to the connection through the Mi/Mg interface In the emergency communication acceptance center 107 of PSTN (Public Switched Telephone Network, Public Switched Telephone Network). At the same time, the emergency communication acceptance center can directly obtain user location information from the LRF 106 through the Le interface, and communicate with the home network through the Mm/Mw interface.

According to the different roaming status of the user and the location of the accessing P-CSCF in the network, the call scenarios are divided into:

Scenario 1: The user is not roaming (in the home network), and the P-CSCF is located in the home network;

Scenario 2: The user roams (in the visited network), and the P-CSCF is located in the home network;

Scenario 3: The user roams (in the visited network), and the P-CSCF is located in the visited network.

Fig. 2 is an IMS emergency call processing procedure, which describes the emergency call service processing procedure in different situations.

When the user initiates an emergency call, the UE judges the call type:

1) If the UE determines that the call is an emergency call, the steps include:

201. The UE adds an emergency call identifier to a session invitation request (INVITE), and sends it to the P-CSCF.

202. After receiving the session invitation request with the emergency call identifier, the P-CSCF forwards the request to the E-CSCF, and the E-CSCF forwards the request to the PSAP.

If the PSAP is located in the PSTN network, the E-CSCF sends it to the PSAP through the MGCF/MGW.

If the UE is not registered with IMS, or has already registered and is roaming (Scenario 2 and Scenario 3), it must also perform IMS emergency call registration before performing step 201, if it has been registered with IMS and is not roaming (Scenario 1), then in The IMS emergency call registration may not be performed before step 201 is performed.

2) The UE may not be able to confirm the emergency call. For example, on some UEs currently, when the user dials the international general emergency number 112 or 911, the UE considers the call as an emergency call and initiates an emergency call process; but when the user dials the Chinese emergency number When calling the number 110, the UE will consider the call as an ordinary call, and then initiate the call according to the ordinary call flow.

Under this kind of request, there are two processing methods:

method one:

This method is suitable for all scenarios.

211. The UE sends a session invitation request (INVITE) to the P-CSCF.

Since the UE does not determine that it is an emergency call, the session invitation request does not include the emergency call identifier.

212. After receiving the session invitation request, the P-CSCF checks the called number according to the local number analysis strategy, and if it is found to be an emergency call, then executes step 213; otherwise, executes a normal process and forwards the call to the S-CSCF.

213. The P-CSCF returns an Alternative Service Response (Alternative Service Response) to the UE, including an emergency call indication, and notifies the UE that the call is an emergency call.

214. After receiving the replacement service response containing the emergency call indication, the UE re-initiates the emergency call in the manner described in 1), or re-initiates the emergency call from another access network (such as the CS network).

Method 2:

This method is applicable to scenario 1 (the user is not roaming and the P-CSCF is located in the home network) and scenario 3 (the user is roaming and the P-CSCF is located in the visited network), that is, the user and the P-CSCF are in the same network.

221. The UE sends a session invitation request (INVITE) to the P-CSCF.

Since the UE does not determine that it is an emergency call, the session invitation request does not include the emergency call identifier.

222. After receiving the session invitation request, the P-CSCF checks the called number according to the local number analysis strategy, and if it is found to be an emergency call, executes step 223; otherwise, executes a normal process and forwards the call to the S-CSCF.

223. The P-CSCF adds the emergency call identifier in the session invitation request, and forwards the request to the E-CSCF, and the E-CSCF forwards it to the PSAP.

If the PSAP is located in the PSTN network, the E-CSCF sends it to the PSAP through the MGCF/MGW.

Compared with the first method, the second method has the characteristics of high execution efficiency, but it is not suitable for the scenario 2 (the user roams, and the P-CSCF is located in the home network).

IMS has nothing to do with access technology, except that it can provide services for packet switching (Packet Switched, PS) access networks such as GPRS (General Packet Radio Service, General Packet Radio Service), WLAN (Wireless Local Area Network, Wireless Local Area Network), It can also provide basic voice services for GSM (Global System for Mobile communications, Global System for Mobile Communications), UMTS (Universal Mobile Telecommunications System, Unified Mobile Communications System) and other mobile cellular networks using Circuit Switched (CS) technology. And supplementary services based on voice services.

When the CS domain, that is, the circuit domain, accesses the IMS, it evolves into an access mode, and the service is completely provided by the IMS. This technology is called IMS Centralized Service (IMS Centralized Service), or ICS for short.

The IMS centralized service has the following characteristics:

(1) IMS provides consistent services for access modes such as circuit domain and packet domain, and supports network integration;

(2) Support the evolution from CS network to IMS network;

In addition to supporting voice services and supplementary services based on voice services, IMS centralized services must also be able to provide emergency call services.

In the IMS centralized service architecture, there are two types of UEs (User Equipment): UEs that support ICS capabilities (hereinafter referred to as ICS UEs) and UEs that do not support ICS capabilities (abbreviated as non-ICS UEs). The user equipment UE described in the present invention is an ICS UE.

Figure 3 is an architecture diagram of the IMS centralized business system, which includes the following functional entities:

IMS centralized service user equipment (ICS UE) 301;

IMS circuit domain control function (IMS CS Control Function, ICCF for short) module 302;

The Call Session Control Function (CSCF for short) module 303 is a session control network element in the IMS.

The control signaling transmission channel between the ICS UE 301 and the ICCF 302 is called an IMS session control channel ICCC (IMS CS Control Channel), also called a session control path. The channel can be borne on the CS domain, which is a CS session control path at this time, or can be borne on the PS domain, which is a PS session control path at this time. The CS session control path uses the Unstructured Supplementary Service Data (USSD) protocol; the PS session control path uses the Session Initial Protocol (SIP).

The IMS session control channel of the present invention adopts the mode of PS session control path.

When the PS session control path is adopted, the ICCF 302 contains a remote user agent (Remote UserAgent, referred to as RUA) function, which is a SIP (Session Initiation Protocol, Session Initiation Protocol) user agent, which is connected to the CSCF 303 on behalf of the user equipment, Access IMS. If CS session control is adopted, ICCF 302 also includes other functions, which will not be described in this paper.

ICS UE 301 completes functions such as IMS registration, session control, and service control through RUA in ICCF 302, and controls the call process in the CS domain, and uses the existing CS domain call mechanism to establish a voice bearer channel between UE and IMS.

Figure 4 is a schematic diagram of a session path in an IMS centralized service application scenario, which includes the following network elements:

User Equipment (UE for short) 401

Visited Mobile Switch Center (Visited Mobile Switch Center, VMSC for short) 402

Proxy Call Session Control Function (Proxy Call Session Control Function, P-CSCF for short) 403

Media Gateway Control Function (MGCF for short) 404

Media Gateway (MGW for short) 405

Interrogating Call Session Control Function (I-CSCF for short)/Serving Call Session Control Function (I-CSCF for short) 406

IMS circuit domain control function (IMS CS Control Function, ICCF for short) 407

Three paths are established from UE 401 to ICCF 406 in the IMS domain: PS session control path, bearer control path and bearer path.

In order to express clearly, the network entities E-CSCF 408 and PSAP 409 of the emergency call network are listed in the figure at the same time.

The session control path is carried on the PS domain, using the Session Initial Protocol (SIP) protocol, and the path passes through the P-CSCF 403 and the I-CSCF/S-CSCF 406 in the IMS domain to reach the ICCF 407.

The bearer control path UE 401 uses standard CS control signaling to access VMSC 402, accesses IMS through MGCF 404, and reaches ICCF 407 through I-CSCF/S-CSCF 406.

The bearer path is that the UE 401 accesses the IMS through the VMSC 402 and the MGW 405, and establishes a media connection with the remote user equipment of the session.

The session control path and the bearer control path converge at ICCF_407 to form an ICS UE call leg, and ICCF 407 acts as an IMS user agent to replace the user equipment to access the IMS to form a remote call leg.

The IMS centralized service uses the session control path to exchange session control information between UE 401 and ICCF 407, and establishes and controls media bearers through the bearer control path, so that the ICS UE can access the IMS.

Fig. 5 is the process flow of the calling (calling) process of the ICS UE in the prior art solution. The specific process is as follows:

501. The UE-A calling terminal initiates a bearer establishment request to the VMSC, and carries the Public Service Identify (PSI) number of the remote user agent (RUA) to be called;

502. The VMSC sends an initial address message (Initial Address Message, IAM for short) to the MGCF, including the RUA PSI number;

503. After receiving the request, the MGCF allocates MGW media resources, and creates an Invite session invitation request and sends it to the RUA in the ICCF through the CSCF;

504. UE-A sends a SIP session invitation request INVITE message to ICCF through the PS session control path. The message contains the SIP or TEL URI (Uniform Resource Identifier) number of UE-B. The request message is sent to ICCF;

This step can be executed simultaneously with steps 501-503.

505. The session control signaling and the bearer control signaling are merged in the RUA of the ICCF,

506. The RUA, as a Back to Back User Agent (B2BUA for short), initiates a session request to UE-B, and the session request passes through the S-CSCF;

507. The S-CSCF sends the message to the remote user through the IMS network, establishes the session between RUA and UE-B through the standard IMS session process, and finally establishes the session between the calling terminal of UE-A and the called terminal of UE-B.

It can be seen from the above process that when an ICS user initiates a call, the network first routes the call from the visited CS domain to the IMS domain to which the user belongs, and then performs subsequent service processing.

If the user initiates an emergency call and the ICS UE cannot confirm the emergency call, the ICS UE will use the ICS method to initiate the call (calling) process. According to the existing IMS emergency call mechanism and ICS session processing mechanism, the call process is shown in Figure 6 shown.

601-603, the same as steps 501-503, UE-A sends a CS bearer establishment request through the bearer control path, and sends it to RUA in ICCF through VMSC, MGCF, I-CSCF/S-CSCF; ICCF waits for the control information in the control path , for the next steps.

Since the emergency call requires the visited network to provide services, and the CS bearer is routed to the home network, it does not meet the requirements of the emergency call.

The following further analyzes the processing process of the control path, and it can be seen that more serious problems lead to call failure.

At the same time of steps 601-603, UE-A executes step 604.

604. Send a SIP session invitation request INVITE message to the P-CSCF through the PS session control path, and the message includes the SIP or TEL URI (Uniform Resource Identifier) number of UE-B;

605. After receiving the session invitation request, the P-CSCF checks the called number according to the local number analysis strategy. If it is found to be an emergency call, perform step 606a or 606b according to the emergency call processing method of the IMS described in FIG. 2, otherwise perform the normal process .

606a. According to the first IMS emergency call processing method, the P-CSCF returns an alternative service response (Alternative Service response) to the UE, including an emergency call indication, and notifies the UE that the call is an emergency call.

After the UE receives the replacement service response containing the emergency call indication, it will no longer use the ICS session call mode and initiate a new emergency call. The emergency call can be an IMS emergency call or a CS emergency call.

In this manner, the normal progress of the emergency call can be guaranteed.

606b. According to the second IMS emergency call processing method, the P-CSCF adds the emergency call identifier in the session invitation request, and forwards the request to the E-CSCF, and the E-CSCF forwards it to the PSAP. If the PSAP is located in the PSTN network, the E-CSCF sends it to the PSAP through the MGCF/MGW.

Since the session invitation request of the session control path is sent to the E-CSCF/PSAP by the P-CSCF, and the CS bearer control signaling is routed to the ICCF, the two control paths cannot be merged, and the session control path cannot control the bearer control path and the CS bearer. , causing the session to fail, preventing the user from making normal emergency calls.

Further, according to the description of FIG. 2 , since scenario 1 (the user is not roaming and the P-CSCF is located in the home network) and scenario 3 (the user is roaming and the P-CSCF is located in the visited network) may adopt the second method, there may be problems, and For scenario 2 (the user roams and the P-CSCF is located in the home network), only the first method can be adopted, and there will be no problem.

From the above analysis, it can be seen that when the user initiates an emergency call, the ICS UE may not be able to determine the emergency call, but using the ICS call process, if the P-CSCF located on the session control path adopts the method of adding an emergency call identifier in the session request , the network will route the CS call initiated by the user back to the IMS domain to which the user belongs, and at the same time send the session invitation request of the session path to the PSAP. At this time, the session control path and the bearer control path cannot be merged, and normal call processing cannot be performed.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for realizing the emergency call service of the IP multimedia subsystem, which overcomes the defect that the emergency call service cannot be realized due to the inability of the ICS UE to determine the emergency call service, and achieves the purpose of realizing the emergency call service.

From the analysis in Figure 6, if the P-CSCF located in the control path can find that the call initiated by the user is an emergency call and is an ICS session, then adopting the first method in the IMS emergency call can avoid this problem.

Considering further that the P-CSCF accessed by the user may be located in the home network or in the visited network, the above method has certain requirements for the P-CSCF, requiring the P-CSCF to be able to identify the ICS session when it finds that it is an emergency call . When the operator introduces ICS services in the home network and requires the P-CSCF of the home network to adopt the method described above, this requirement is reasonable, but for the P-CSCF of the visited network, since it may not belong to the same operator, then This method may not be possible. Therefore, the present invention proposes another method, focusing on solving the problem in the user roaming scenario. If the visited P-CSCF located on the control path can find that the call initiated by the user is an emergency call, and the user is a roaming user or a roaming user from a designated operator, then only method 1 of the IMS emergency call is used, This avoids the problem.

In order to solve the above-mentioned technical problems, the invention provides a kind of realization method of IP multimedia subsystem emergency call service, comprising the following steps:

(a) After receiving the session invitation request of the call initiated by the user equipment, the proxy call session control function P-CSCF checks the call attribute, and judges the call type and session type of the call;

(b) If the P-CSCF judges that the call is an emergency call and is an IP Multimedia Subsystem Centralized Service ICS session, it returns a replacement service response to the user equipment, and includes an emergency call indication in the response, and notifies The call of the user equipment is an emergency call;

(c) After receiving the replacement service response, the user equipment initiates a new emergency call from the IP Multimedia Subsystem IMS domain or CS domain.

Further, the above method can also have the following characteristics:

In step (a), the emergency call identifier is not added to the session invitation request, and the P-CSCF judges the call type according to the encoding scheme of the emergency call number in the local policy. If the called number in the session invitation request is the same as the local If the encoding scheme of the emergency call number in the policy matches, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call.

Further, the above method can also have the following characteristics:

In step (a), the P-CSCF judges the session type according to the ICS session identification tag or the ICS session media type in the session invitation request, and if it is found that the ICS session identification tag or ICS session identification tag or ICS If the session media type is used, it is regarded as an ICS session, otherwise it is a normal SIP session.

Further, the above method can also have the following characteristics:

If the P-CSCF determines that the call type of the call is an ordinary call, it forwards the session invitation request to the serving call session control function S-CSCF of the home network.

If the P-CSCF determines that the call is an emergency call but not an ICS session, the P-CSCF returns to the user equipment a replacement service response containing an emergency call indication, and notifies the user equipment that the call is an emergency call; Or, the P-CSCF adds the emergency call identifier in the session invitation request, and forwards the request to the emergency call session control function E-CSCF.

Further, the above method can also have the following characteristics:

The user equipment is an ICS user equipment;

In step (a), the user equipment initiates an emergency call using a packet-switched domain session control path, and the user equipment does not recognize that it is an emergency call;

In step (c), before initiating a new emergency call, the user equipment will release the CS domain call and the corresponding bearer established on the bearer control path.

In order to solve the above-mentioned technical problems, the present invention provides a kind of realization method of IP multimedia subsystem emergency call service again, comprises the following steps:

(a) After receiving the session invitation request of the call initiated by the user equipment, the proxy call session control function P-CSCF checks the call attribute, and judges the call type of the call and the roaming state of the user;

(b) If the P-CSCF determines that the call is an emergency call and the user is in a roaming state, then return a replacement service response to the user equipment, including an emergency call indication, and notify the user equipment that the call is an emergency call;

(c) After receiving the replacement service response, the user equipment initiates a new emergency call from the IP Multimedia Subsystem IMS domain or CS domain.

Further, the above method can also have the following characteristics:

In step (a), the emergency call identifier is not added to the session invitation request, and the P-CSCF judges the call type according to the encoding scheme of the emergency call number in the local policy. If the called number in the session invitation request is the same as the local If the encoding scheme of the emergency call number in the policy matches, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call.

Further, the above method can also have the following characteristics:

In step (a), the P-CSC judges whether the user is a roaming user according to the home network information carried in the user identifier and the user's current access network information:

If the user's home network information is the same as the P-CSCF's network information and the user's current access network is not in the home location, or the user's home network information is different from the P-CSCF's network information, the P-CSCF determines that the user is in a roaming state;

If the user's home network information is the same as the P-CSCF's network information and the user's current access network is at home, the P-CSCF judges that the user is in a non-roaming state.

Further, the above method can also have the following characteristics:

If the P-CSCF determines that the call type of the call is an ordinary call, the P-CSCF forwards the session invitation request to the serving call session control function S-CSCF of the home network.

If the P-CSCF determines that the call is an emergency call and the user is in a non-roaming state, the P-CSCF returns a replacement service response containing an emergency call indication to the user equipment, and notifies the user equipment of the call It is an emergency call; or, the P-CSCF adds an emergency call identifier in the session invitation request, and forwards the request to the emergency call session control function E-CSCF.

Further, the above method can also have the following characteristics:

The user equipment is an ICS user equipment;

In step (a), the user equipment initiates an emergency call using a packet-switched domain session control path, and the user equipment does not recognize that it is an emergency call;

In step (c), before initiating a new emergency call, the user equipment will release the CS domain call and the corresponding bearer established on the bearer control path.

In order to solve the above-mentioned technical problems, the invention provides a kind of realization method of IP multimedia subsystem emergency call service, comprising the following steps:

(a) After receiving the session invitation request of the call initiated by the user equipment, the proxy call session control function P-CSCF checks the call attribute, and judges the call type of the call, the roaming state of the user and the operator to which it belongs;

(b) If the P-CSCF judges that the call is an emergency call and the user is a roaming user of a specified operator set in advance, then return a replacement service response to the user equipment, including an emergency call indication, and notify the The call of the user equipment is an emergency call;

(c) After receiving the replacement service response, the user equipment initiates a new emergency call from the IP Multimedia Subsystem IMS domain or CS domain.

Further, the above method can also have the following characteristics:

In step (a), the emergency call identifier is not added to the session invitation request, and the P-CSCF judges the call type according to the encoding scheme of the emergency call number in the local policy. If the called number in the session invitation request is the same as the local If the encoding scheme of the emergency call number in the policy matches, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call.

Further, the above method can also have the following characteristics:

In step (a), the P-CSC judges whether the user is a roaming user according to the home network information carried in the user identifier and the user's current access network information:

If the user's home network information is the same as the P-CSCF's network information and the user's current access network is not at home, or the user's home network information is different from the P-CSCF's network information, then the P-CSCF judges The user is roaming;

If the user's home network information is the same as the P-CSCF's network information and the user's current access network is at home, the P-CSCF determines that the user is in a non-roaming state.

Further, the above method can also have the following characteristics:

If the P-CSCF determines that the call type of the call is an ordinary call, it forwards the session invitation request to the serving call session control function S-CSCF of the home network.

If the P-CSCF determines that the call is an emergency call and the user is in a non-roaming state, or that the call is an emergency call and the user is in a roaming state but is not a roaming user of the specified operator, the The P-CSCF returns a replacement service response containing an emergency call indication to the user equipment, notifying the user equipment that the call is an emergency call; or, the P-CSCF adds an emergency call identifier to the session invitation request, and sends the request Forward to the Emergency Call Session Control Function E-CSCF.

Further, the above method can also have the following characteristics:

The user equipment is an ICS user equipment;

In step (a), the user equipment initiates an emergency call using a packet-switched domain session control path, and the user equipment does not recognize that it is an emergency call;

In step (c), before initiating a new emergency call, the user equipment will release the CS domain call and the corresponding bearer established on the bearer control path.

In the present invention, the P-CSCF is used in the IMS to judge whether the call is an emergency call and is an ICS session or the user is in a roaming state, then rejects the call by returning a replacement service response, and indicates that the call is an emergency call, and the UE makes an emergency call again according to the instruction Therefore, when the ICS UE cannot determine the emergency call, the purpose of still ensuring the normal progress of the emergency call is achieved.

Description of drawings

Fig. 1 is a system frame diagram of an IMS emergency call.

Fig. 2 is a flowchart of an IMS emergency call processing procedure in the prior art.

FIG. 3 is a system architecture diagram of an IMS centralized service.

Fig. 4 is a schematic diagram of a session path in an IMS centralized service application scenario.

Fig. 5 is a flow chart of the calling (calling) process of the ICS UE in the prior art.

Fig. 6 is a flow chart of the calling (calling) process when the ICS UE does not recognize the emergency call in the prior art.

Fig. 7 is a flow chart of the calling (calling) process when the ICS UE does not recognize the emergency call in the first embodiment of the present invention.

Fig. 8 is a flow chart of the process of P-CSCF handling roaming users in the second embodiment of the present invention.

Detailed ways

The core idea of the present invention is: in the IMS, when the P-CSCF judges that the call is an emergency call and is an ICS session, or that the call is an emergency call and the user is in a roaming state, the call is rejected by returning a replacement service response and indicating The call is an emergency call, and the UE repeats the emergency call process according to the instruction. Therefore, when the ICS UE cannot determine the emergency call, the purpose of still ensuring the normal progress of the emergency call is achieved.

The technical solution of the present invention will be described in more detail below with reference to the drawings and embodiments.

first embodiment

Fig. 7 is the emergency call processing flow of the IMS centralized service when the PS session control path is adopted in the IMS centralized service in this embodiment, and describes the call processing process when the user initiates an emergency call, but the ICS UE does not recognize that it is an emergency call . Include the following steps:

701-703, the same as steps 501-503, UE-A sends a CS bearer establishment request through the bearer control path, and sends it to RUA in ICCF through VMSC, MGCF, I-CSCF/S-CSCF; ICCF waits for the control information in the control path , for the next steps.

At the same time of steps 701-703, UE-A executes step 704.

704. UE-A sends a SIP session invitation request INVITE message to the P-CSCF through the PS session control path, and the message includes the SIP or TEL URI (Uniform Resource Identifier) number of UE-B;

The message further carries an ICS session identification tag or an ICS session media type, and indicates that the session invitation request is an ICS session through the above parameters, so as to distinguish it from a normal SIP session.

705. After receiving the session invitation request, the P-CSCF analyzes the call attribute, and the analyzed content includes:

1) Call type: Check the called number according to the local number analysis strategy to determine whether it is an emergency call or a normal call;

2) Session type: According to the ICS session identification tag carried in the session invitation request or the ICS session media type, it is judged whether it is an ICS session or a common SIP session.

706. If the P-CSCF judges that the call is an emergency call and is an IMS centralized service session, return an alternative service response (Alternative Service response) to the UE, and include an emergency call indication, and notify the UE that the call is an emergency call;

The P-CSCF further determines the type and priority of the emergency call and the access network used to re-initiate the emergency call, and notifies the UE in the response.

If the P-CSCF determines that the call type is an ordinary call, it forwards the session invitation request to the S-CSCF of the home network regardless of whether the session type is an ICS session or an ordinary SIP session. If the session type is an ICS session, the S-CSCF will forward the session to the ICCF to merge with the bearer control path, otherwise it will be processed as a normal SIP session.

If the P-CSCF determines that the call is an emergency call but not an ICS session, it can either return an Alternative Service Response (Alternative Service Response) to the UE and include an emergency call indication to inform the UE that the call is an emergency call, or it can be included in the session invitation request Add emergency call identification and forward the request to E-CSCF.

707. After receiving the replacement service response, the UE releases the CS domain call and the corresponding bearer established on the bearer control path;

708. The UE replaces the instruction in the service response to initiate a new emergency call, which may be an IMS emergency call or a CS emergency call.

second embodiment

Fig. 8 is the process flow of P-CSCF in this embodiment to the roaming user processing procedure, describes the call processing procedure when the user initiates an emergency call, but UE (including ICS UE) does not recognize the situation that is an emergency call. Include the following steps:

If the UE is an ICS UE, steps 801 to 803 need to be performed, and if the UE is an ordinary IMS UE, steps 801 to 803 do not need to be performed.

801-803, the same as steps 501-503, UE-A sends a CS bearer establishment request through the bearer control path, and sends it to RUA in ICCF through VMSC, MGCF, I-CSCF/S-CSCF; ICCF waits for the control information in the control path , for subsequent steps;

At the same time as steps 801-803, UE-A performs step 804:

804. UE-A sends a SIP session invitation request INVITE message to the P-CSCF, and the message includes the SIP or TEL URI (Uniform Resource Identifier) number of UE-B.

805. After receiving the session invitation request, the P-CSCF analyzes the call type and roaming state.

1) Call type: Check the called number according to the local number analysis strategy to determine whether it is an emergency call or a normal call;

2) Roaming state: judge whether the user is a roaming user according to the home network information carried in the user ID and the user's current access network information: if the user's home network information is the same as the network information of the P-CSCF and the user's current access network is not in the home network or the user’s home network information is different from the P-CSCF’s network information, the P-CSCF judges that the user is roaming; if the user’s home network information is the same as the P-CSCF’s network information and the user’s current access network is in the home , the P-CSCF judges that the user is in a non-roaming state.

806. If the P-CSCF judges that the call is an emergency call and the user is in a roaming state, return an alternative service response (Alternative Service response) to the UE, including an emergency call indication, and notify the UE that the call is an emergency call;

The P-CSCF further determines the type and priority of the emergency call and the access network used to re-initiate the emergency call, and notifies the UE in the response.

If the P-CSCF determines that the call type is an ordinary call, it forwards the session invitation request to the S-CSCF of the home network regardless of whether the user is in a roaming state. If it is a session initiated by the ICS UE, the S-CSCF will forward the session to the ICCF to merge with the bearer control path, otherwise it will be processed as a normal SIP session.

If the P-CSCF determines that the call is an emergency call but the user is in a non-roaming state, it can either return an Alternative Service Response (Alternative Service Response) to the UE and include an emergency call indication to inform the UE that the call is an emergency call, or it can The emergency call identifier is added to the request, and the request is forwarded to the E-CSCF.

In another embodiment, the roaming user may only be for a roaming user from a specified operator, that is, in this step, only when the call is an emergency call and the user is a roaming user from a specified operator, it is necessary to notify the UE Returns the replacement business response. If the call is an emergency call, but the user is not a roaming user from the specified operator, an alternative service response can be returned to the UE to notify the UE that the call is an emergency call, or an emergency call identifier can be added to the session invitation request, and the The request is forwarded to the E-CSCF. The designated operator may be preset in the P-CSCF. Correspondingly, the P-CSCF needs to first determine the operator to which the user belongs.

807. After the UE receives the replacement service response, if the session initiated by the UE is an ICS session, it needs to release the CS domain call and the corresponding bearer established on the bearer control path;

808. The UE initiates a new emergency call according to the indication in the replacement service response, which may be an IMS emergency call or a CS emergency call.

In summary, the method of the present invention is applied to the IMS call initiation process, and the P-CSCF checks the call attribute. If it is an emergency call and is an ICS session or the user is in a roaming state, the replacement service response is returned to reject the call, and in The response contains an emergency call indication, which instructs the user equipment to re-initiate the emergency call, and achieves the purpose of ensuring the normal progress of the emergency call when the ICS UE cannot recognize the emergency call.

Of course, the present invention can also have other various embodiments, and those skilled in the art can make various corresponding changes and deformations according to the present invention without departing from the spirit and essence of the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (15)

1. A method for realizing an IP multimedia subsystem emergency call service, comprising the steps of: (a) After receiving the session invitation request of the call initiated by the user equipment, the proxy call session control function P-CSCF checks the call attribute, and judges the call type and session type of the call; (b) If the P-CSCF judges that the call is an emergency call and is an IP Multimedia Subsystem Centralized Service ICS session, it returns a replacement service response to the user equipment, and includes an emergency call indication in the response, and notifies The call of the user equipment is an emergency call; (c) After receiving the replacement service response, the user equipment initiates a new emergency call from the IP Multimedia Subsystem IMS domain or circuit domain; If the P-CSCF determines that the call is an emergency call but not an ICS session, it adds an emergency call identifier to the session invitation request and forwards it to the emergency call session control function E-CSCF. 2. The realization method as claimed in claim 1, characterized in that: In step (a), the emergency call identifier is not added to the session invitation request, and the P-CSCF judges the call type according to the encoding scheme of the emergency call number in the local policy. If the called number in the session invitation request is the same as the local If the encoding scheme of the emergency call number in the policy matches, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call. 3. The realization method as claimed in claim 1 or 2, characterized in that: In step (a), the P-CSCF judges the session type according to the ICS session identification tag or the ICS session media type in the session invitation request, and if it is found that the ICS session identification tag or ICS session identification tag or ICS If the session media type is used, it is regarded as an ICS session, otherwise it is a normal SIP session. 4. the realization method as claimed in claim 1, is characterized in that, in step (b): If the P-CSCF determines that the call type of the call is an ordinary call, it forwards the session invitation request to the serving call session control function S-CSCF of the home network. 5. The implementation method according to claim 1, characterized in that: The user equipment is an ICS user equipment; In step (a), the user equipment initiates an emergency call using a packet-switched domain session control path, and the user equipment does not recognize that it is an emergency call; In step (c), before initiating a new emergency call, the user equipment will release the CS domain call and the corresponding bearer established on the bearer control path. 6. A method for realizing an IP multimedia subsystem emergency call service, comprising the steps of: (a) After receiving the session invitation request of the call initiated by the user equipment, the proxy call session control function P-CSCF checks the call attribute, and judges the call type of the call and the roaming state of the user; (b) If the P-CSCF determines that the call is an emergency call and the user is in a roaming state, then return a replacement service response to the user equipment, including an emergency call indication, and notify the user equipment that the call is an emergency call; (c) After receiving the replacement service response, the user equipment initiates a new emergency call from the IP Multimedia Subsystem IMS domain or circuit domain; If the P-CSCF determines that the call is an emergency call but the user is in a non-roaming state, the P-CSCF adds an emergency call identifier to the session invitation request and forwards it to the emergency call session control function E-CSCF. 7. The realization method as claimed in claim 6, characterized in that: In step (a), the emergency call identifier is not added to the session invitation request, and the P-CSCF judges the call type according to the encoding scheme of the emergency call number in the local policy. If the called number in the session invitation request is the same as the local If the encoding scheme of the emergency call number in the policy matches, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call. 8. The realization method as claimed in claim 6 or 7, characterized in that: In step (a), the P-CSC judges whether the user is a roaming user according to the home network information carried in the user identifier and the user's current access network information: If the user's home network information is the same as the P-CSCF's network information and the user's current access network is not in the home location, or the user's home network information is different from the P-CSCF's network information, the P-CSCF determines that the user is in a roaming state; If the user's home network information is the same as the P-CSCF's network information and the user's current access network is at home, the P-CSCF judges that the user is in a non-roaming state. 9. the realization method as claimed in claim 6, is characterized in that, in step (b): If the P-CSCF determines that the call type of the call is an ordinary call, it forwards the session invitation request to the serving call session control function S-CSCF of the home network. 10. The implementation method according to claim 6, characterized in that: The user equipment is an ICS user equipment; In step (a), the user equipment initiates an emergency call using a packet-switched domain session control path, and the user equipment does not recognize that it is an emergency call; In step (c), before initiating a new emergency call, the user equipment will release the CS domain call and the corresponding bearer established on the bearer control path. 11. A method for realizing an IP multimedia subsystem emergency call service, comprising the steps of: (a) After receiving the session invitation request of the call initiated by the user equipment, the proxy call session control function P-CSCF checks the call attribute, and judges the call type of the call, the roaming state of the user and the operator to which it belongs; (b) If the P-CSCF judges that the call is an emergency call and the user is a roaming user of a specified operator set in advance, then return a replacement service response to the user equipment, including an emergency call indication, and notify the The call of the user equipment is an emergency call; (c) After receiving the replacement service response, the user equipment initiates a new emergency call from the IP Multimedia Subsystem IMS domain or circuit domain; If the call is an emergency call but the user is not a roaming user from the specified operator, the emergency call identifier is added to the session invitation request and forwarded to the emergency call session control function E-CSCF. 12. The implementation method according to claim 11, characterized in that: In step (a), the emergency call identifier is not added to the session invitation request, and the P-CSCF judges the call type according to the encoding scheme of the emergency call number in the local policy. If the called number in the session invitation request is the same as the local If the encoding scheme of the emergency call number in the policy matches, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call. 13. The implementation method according to claim 11 or 12, characterized in that: In step (a), the P-CSC judges whether the user is a roaming user according to the home network information carried in the user identifier and the user's current access network information: If the user's home network information is the same as the P-CSCF's network information and the user's current access network is not at home, or the user's home network information is different from the P-CSCF's network information, then the P-CSCF judges The user is roaming; If the user's home network information is the same as the P-CSCF's network information and the user's current access network is at home, the P-CSCF determines that the user is in a non-roaming state. 14. the realization method as claimed in claim 11, is characterized in that, in step (b): If the P-CSCF determines that the call type of the call is an ordinary call, it forwards the session invitation request to the serving call session control function S-CSCF of the home network. 15. The implementation method according to claim 11, characterized in that: The user equipment is an ICS user equipment; In step (a), the user equipment initiates an emergency call using a packet-switched domain session control path, and the user equipment does not recognize that it is an emergency call; In step (c), before initiating a new emergency call, the user equipment will release the CS domain call and the corresponding bearer established on the bearer control path.

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