WO2009100638A1

WO2009100638A1 - Emergency call service realizing method and p-cscf for ip multimedia subsystem

Info

Publication number: WO2009100638A1
Application number: PCT/CN2008/073602
Authority: WO
Inventors: Zhenwu Hao; Shilin You; Zhendong Li; Changle Zou
Original assignee: Zte Corporation
Priority date: 2008-02-13
Filing date: 2008-12-19
Publication date: 2009-08-20
Also published as: CN101227648A; CN101227648B

Abstract

An emergency call service realizing method for IP Multimedia Subsystem, the method comprises that Proxy Call Session Control Function (P-CSCF) detects the call attribute and determines the call type and the session type after receiving the call session invitation request started by a user equipment; if the P-CSCF determines that the call is an emergent call and is an IP Multimedia Subsystem Centralized Service (ICS) session, an alternative service response containing an emergency call indication is fed back to the user equipment, and the user equipment is notified that the call is an emergency call; a new emergency call is started from an IPMultimedia Subsystem (IMS) domain or circuit domain after the user equipment receives the alternative service response.

Description

Implementation method of IP multimedia subsystem emergency call service and P-CSCF

Technical field

The present invention relates to the field of communications, and in particular, to an implementation method of an emergency call service of an IP multimedia subsystem and a proxy call session control function module P-CSCF. Background technique

According to government regulations, telecommunications networks must be able to provide emergency voice call 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 identity to initiate an emergency call, the network connects the emergency call to the local emergency communication receiving center, such as police, fire, medical care, Rescue, etc.

The IP (Internet Protocol) Multimedia Subsystem (IMS) must also provide emergency call services.

Figure 1 is the system reference framework for IMS emergency calls. The entire architecture includes user equipment (User

Equipment, referred to as UE) 101, Proxy Call Session Control Function (P-CSCF) 102, Serving Call Session Control Function (S-CSCF) 103, Home Subscriber Server (Home) Subscriber Server (referred to as HSS) 104, Emergency Call Session Control Function (E-CSCF) 105, Location Retrieval Function (LRF) 106, and Public Safety Answering Point (Public Safety Answering Point, Referred to as PSAP 107, in addition, the Interconnection Border Control Function (IBCF), Interrogating Call Session Control Function (I-CSCF), and media gateway control function are also involved in the session. Functional entities such as Media Gateway Control Function (MGCF) and Media Gateway (MGW) (not shown in the figure).

The E-CSCF 105 is a new functional entity introduced in the IMS domain, which is located in the same network as the P-CSCF 102 (the visited network of the user when the user roams), and is responsible for receiving the emergency from the P-CSCF 102. Session establishment request, based on location information provided by the user or obtained from LRF 106 The location information and routing information are taken, and the emergency session establishment request is routed through the Mm interface to the IP network emergency communication receiving center 107, or via the Mi/Mg interface to the PSTN (Public Switched Telephone Network). Emergency communication reception center 107. At the same time, the emergency communication receiving center can directly obtain the user location information from the LRF 106 through the Le interface, and contact the home network through the Mm/Mw interface.

According to the different roaming status of the user and the location of the access P-CSCF in the network, the scene in which the call occurs is divided into:

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

Scenario 2: User roaming (on the visited network), the P-CSCF is located in the home network;

Scenario 3: User roaming (on the visited network), the P-CSCF is located on the visited network.

Figure 2 is an IMS emergency call processing procedure that describes the processing of emergency call services in different situations.

When the user initiates an emergency call, the UE determines 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 the session invitation request (INVITE), and sends the emergency call identifier to

P-CSCF.

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

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

If the UE is not registered with the IMS, or is already registered and is in the roaming state (Scenario 2 and Scenario 3), the IMS emergency call registration must also be performed before performing step 201, if the IMS has been registered and has not roamed (Scenario 1), then 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 the current part of the UE, when the user dials the international emergency call number 112 or 911, the UE considers the call to be an emergency call, and then initiates an emergency call procedure; When the number 110 is called, the UE considers the call to be a normal call and then initiates the call according to the normal call procedure. Under this request, there are two ways to deal with it:

method one:

This method works 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 emergency call identification is not included in the session invitation request.

212. After receiving the session invitation request, the P-CSCF checks the called number according to the local number analysis policy. If it is found to be an emergency call, step 213 is performed. Otherwise, the normal process is performed, and the call is forwarded to the S-CSCF.

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

214. After receiving the replacement service response including 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:

The method is applicable to scenario 1 (the user is not roaming and the P-CSCF is located in the home network) and scenario 3 (user roaming, 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.

222. After receiving the session invitation request, the P-CSCF checks the called number according to the local number analysis policy. If it is found to be an emergency call, step 223 is performed. Otherwise, the normal process is performed, and the call is forwarded to the S-CSCF.

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

If located in the PSAP in the PSTN network, the E-CSCF transmits to the PSAP ₀ through MGCF / MGW Compared with mode 1, mode 2 has the characteristics of high execution efficiency, but it is not applicable to scenario 2 (user roaming, P-CSCF is located in the home network).

The IMS is independent of the access technology, except that it can provide services for packet switching (PS) access networks such as GPRS (General Packet Radio Service) and WLAN (Wireless Local Area Network). It can also provide basic voice services for mobile cellular networks such as GSM (Global System for Mobile communications), UMTS (Universal Mobile Telecommunications System) and other circuit switched (CS) technologies. , 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 (ICS).

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 convergence;

(2) Supporting the evolution of the CS network to the 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 user equipments (User Equipment): ICS-capable UEs (ICS UEs) and ICS-capable UEs (non-ICS UEs). The user equipment UE in the present invention is an ICS UE.

Figure 3 is a structural diagram of the IMS centralized service system, which includes the following functional entities:

IMS Centralized Service User Equipment ( ICS UE ) 301 ;

The IMS CS Control Function (ICCF) module 302; the Call Session Control Function (CSCF) 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 IMS session control. It ICCC (IMS CS Control Channel), also known as the session control path. The channel can be carried on the CS domain. In this case, it is a CS session control path, and can also be carried on the PS domain. In this case, it is a PS session control path. 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 uses a PS session to control the path.

When the PS session control path is used, the ICCF 302 includes a Remote User Agent (RUA) function, which is a SIP (Session Initiation Protocol) user agent, representing the user equipment and the CSCF 303. Connected to the IMS. If CS is used to control the path, ICCF 302 also contains other functions, which are not described in this article.

The ICS UE 301 performs functions such as IMS registration, session control, and service control through the RUA in the ICCF 302, and controls the call process in the CS domain, and establishes a voice 7-channel between the UE and the IMS by using the existing CS domain call mechanism. .

Figure 4 is a schematic diagram of a session path of an IMS centralized service application scenario, including the following network elements: User Equipment (UE) 401

Visiting Mobile Switch Center (VMSC) 402 Proxy Call Session Control Function (P-CSCF) 403

Media Gateway Control Function (MGCF) 404 Media Gateway (MGW) 405

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

IMS CS Domain Control Function (IMSCF Control Function, ICCF for short) 407

The UE 401 to the ICCF 406 of the IMS domain establishes three paths: a PS session control path, a bearer control path, and a 7-carrier path. For clarity, the network entities E-CSCF 408 and PSAP 409 of the emergency call network are also listed.

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

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

The bearer path is connected to the IMS through the UE 401, 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 branch, and ICCF 407 acts as an IMS user agent, instead of the user equipment accessing the IMS, forming a remote call branch.

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

FIG. 5 is a flow chart of a call origination (calling) process of an ICS UE in the prior art solution. The specific process is as follows:

501. The UE-A calling terminal initiates a bearer setup request to the VMSC, and carries a Public Service Identity (PSI) number of the remote user agent (RUA) that needs to call. 502. The VMSC sends an initial address message to the MGCF. (Initial Address Message, referred to as

I AM), including the RUA PSI number;

503. After receiving the request, the MGCF allocates the MGW media resource, and creates an Invite session invitation request to be sent by the CSCF to the RUA in the ICCF;

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

This step can be performed simultaneously with steps 501 to 503.

505. The session control signaling and the bearer control signaling are merged in the RUA of the ICCF. 506. The RUA acts as a back-to-back user agent (B2BUA) to initiate a session request to the UE-B, and the session request passes through the S-CSCF.

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

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

If the IKE UE initiates an emergency call and the ICS UE cannot confirm the emergency call, the ICS UE initiates a call origination (calling) process using the ICS mode. According to the existing IMS emergency call mechanism and the ICS session processing mechanism, the call process is as shown in the figure. 6 is shown.

601 603. The UE-A sends a CS bearer setup request through the bearer control path, and sends the CS bearer setup request to the ICCF through the VMSC, the MGCF, the I-CSCF/S-CSCF, and the ICCF waits for the control information in the control path to Carry out the next steps.

Since the emergency call request is provided by the visited network, and the CS bearer is routed to the home network, it does not meet the requirements of the emergency call.

The process of controlling the control path is further analyzed below, and a more serious problem can be seen, resulting in a call failure.

At the same time as steps 601-603, UE-A performs step 604.

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

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

606a. According to the IMS emergency call processing mode 1, the P-CSCF returns an alternate service response (Alternative Service Response) to the UE, and includes an emergency call indication, and notifies the UE that the call is an emergency call.

After receiving the replacement service response including the emergency call indication, the UE will no longer use the ICS session call mode to initiate a new emergency call. The emergency call may be an IMS emergency call or may be CS emergency call.

该This method can ensure the normal operation of emergency calls.

606b, according to the IMS emergency call processing mode 2, the P-CSCF adds an emergency call identifier to the session invitation request, and forwards the request to the E-CSCF, and the E-CSCF forwards to the PSAP. If the PSAP is located in the PSTN network, the E-CSCF is sent 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 a normal emergency call.

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 roaming and the P-CSCF is located in the visited network) may use mode 2, there may be The problem, and for scenario 2 (user roaming and P-CSCF is located in the home network) can only use mode one, there will be no problem.

It can be seen from the above analysis that when the user initiates an emergency call, the ICS UE may not be able to determine the emergency call, and the ICS call procedure is used, if the P-CSCF located on the session control path is used to add the emergency call identifier in the session request. The network will forward the CS call initiated by the user back to the IMS domain to which the user belongs, and send the session invitation request of the session path to the PSAP. As a result, the session control path and the bearer control path cannot be merged, and normal calls cannot be made. deal with. Summary of the invention

The technical problem to be solved by the present invention is to provide an implementation method of an emergency call service of an IP multimedia subsystem, which overcomes the defect that the ICS UE cannot determine an emergency call, thereby failing to implement an emergency call service, and achieves the purpose of implementing an emergency call service.

From the analysis of Fig. 6, if the P-CSCF located in the control path can find that the user-initiated call is an emergency call and is an ICS session, then the first method in the IMS emergency call can be avoided.

It is further considered that the P-CSCF accessed by the user may be located in the home network or may be located in the visited network. The method described above has certain requirements for the P-CSCF, and the P-CSCF is required to be discovered. An ICS session is identified during an emergency call. When the operator introduces the ICS service in the home network and requires the P-CSCF of the home network to use the method described above, this requirement is reasonable, but the P-CSCF of the visited network may not belong to the same operator. You may not be able to use this method. Therefore, the present invention proposes another method, which focuses on solving problems in a user roaming scenario. If the visited P-CSCF located in the control path can find that the user-initiated call is an emergency call, and the user is a roaming user, or a roaming user from a designated operator, then only the mode one in the IMS emergency call is used. This will avoid the problem.

To solve the above technical problem, the present invention provides a method for implementing an emergency call service of an IP multimedia subsystem, including the following steps:

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

(b) the P-CSCF, if it is determined that the call is an emergency call, and is an IP multimedia subsystem centralized service ICS session, returns an alternate service response to the user equipment, and includes an emergency call indication, the notification in the response The user equipment is the emergency call;

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

further,

In step (a), the emergency call identifier is not added to the session invitation request, and the P-CSCF determines the call type according to the coding scheme of the emergency call number in the local policy, if the called number of the session invitation request and the local call If the coding 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,

In step (a), the P-CSCF determines the session type according to the ICS session identification tag or the ICS session media type in the session invitation request, and if the session invitation request is found to carry the ICS session identification tag or ICS The session media type is considered to be an ICS session, otherwise it is a normal SIP session.

further,

If the P-CSCF determines that the call type of the call is an ordinary call, the session invites Please request to go to the service call session control function S-CSCF of the home network,

If the P-CSCF determines that the call is an emergency call but is not an ICS session, the P-CSCF returns an alternate service response including an emergency call indication to the user equipment, to notify the user equipment that the call is an emergency call; Alternatively, the P-CSCF adds an emergency call identifier to the session invitation request, and forwards the request to the emergency call session control function E-CSCF.

further,

The user equipment is an ICS user equipment;

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

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

To solve the above technical problem, the present invention also provides a proxy call session control function module P-CSCF of an IP multimedia subsystem, the P-CSCF is configured to receive a session invitation request of a user equipment, and check the session invitation request. a call attribute carried in the call, the call attribute includes a call type and a session type; if the call is determined to be an emergency call, and the IP multimedia subsystem is a centralized service ICS session, and is used to return an alternate service response to the user equipment, An emergency call indication is included in the response.

further,

If it is determined that the call is a normal call, it is also used to forward the session invitation request to the serving call session control function S-CSCF of the home network;

If it is determined that the call is an emergency call but not an ICS session, it is also used to return an alternate service response to the UE, and includes an emergency call indication, or, in the session invitation request, an emergency call identifier is added, and the request is forwarded to the emergency call session control. Function E-CSCF.

further,

The P-CSCF checks the call type according to an encoding scheme of the emergency call number in the local policy, and if the called number of the session invitation request matches the coding scheme of the emergency call number in the local policy, the The call initiated by the user is an emergency call, otherwise it is an ordinary call; The P-CSCF checks the session type according to the ICS session identification tag or the ICS session media type in the session invitation request, and if the session invitation request is found to carry the ICS session identification tag or the ICS session media type, It is considered an ICS session, otherwise it is a normal SIP session.

To solve the technical problem, the present invention also provides an implementation method of an emergency call service of an IP multimedia subsystem, including the following steps:

(a) Proxy call session control function After receiving the session invitation request of the call initiated by the user equipment, the P-CSCF checks the call attribute, where the call attribute includes the call type and the roaming status of the user; (b) the P-CSCF Determining that the call is an emergency call, and when the user is in a roaming state, returning a replacement service response to the user equipment, and including an emergency call indication, notifying the user equipment that the call is an emergency call;

further,

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

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

If the home network information of the user is the same as the network information of the P-CSCF and the user currently accesses the network at the home location, the P-CSCF determines that the user is in a non-roaming state.

Further, in step (b):

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 an alternate service response including an emergency call indication to the user equipment, and notifies the user equipment of the call. Is an emergency call; or, the P-CSCF is in a session invitation request The emergency call identity is added and the request is forwarded to the emergency call session control function E-CSCF.

In order to solve the above technical problem, the present invention further provides a proxy call session control function module P-CSCF of an IP multimedia subsystem, where the P-CSCF is configured to receive a session invitation request sent by a user equipment, and check a session invitation request. Carrying a call attribute, the call attribute includes a call type and a roaming state; if the call is determined to be an emergency call, and the user terminal is in a roaming state, it is further configured to return a replacement service response to the user terminal, and include an emergency call indication;

further,

If the call is a normal call, the P-CSCF is further used to forward the session invitation request to the S-CSCF of the home network; if the call is determined to be an emergency call but the user terminal is in a non-roaming state, the P The -CSCF is further configured to return an alternate service response to the user terminal UE and include an emergency call indication, or to add an emergency call identity to the session invitation request and forward the request to the E-CSCF.

To solve the above technical problem, the present invention also provides an implementation method of an emergency call service of an IP multimedia subsystem, including the following steps:

(a) Proxy call session control function After receiving the session invitation request of the call initiated by the user equipment, the P-CSCF checks the call attribute, determines the call type of the call, the roaming status of the user, and the associated operator;

(b) if the P-CSCF determines that the call is an emergency call, and the user is a roaming user of a designated operator set in advance, returning a replacement service response to the user equipment, and including an emergency call indication, notifying the office Said user equipment, the call is an emergency call;

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

further,

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

further,

If the P-CSCF determines that the call is an emergency call and the user is in a non-roaming state, or the call is an emergency call, and the user is in a roaming state but is not a roaming user of the designated operator, The P-CSCF returns an alternate service response including the emergency call indication to the user equipment, and notifies 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 the request is Forward to the emergency call session control function E-CSCF.

The invention uses the P-CSCF in the IMS to determine whether the call is an emergency call and the ICS session or the user is in a roaming state, rejects the call by returning a replacement service response, and indicates that the call is an emergency call, and the UE re-emerges according to the indication. The calling process, therefore, achieves the goal of ensuring that the emergency call is normally performed when the ICS UE cannot determine the emergency call. BRIEF abstract

Figure 1 is a system framework diagram of an IMS emergency call.

2 is a flow chart of a prior art IMS emergency call processing procedure.

Figure 3 is a system architecture diagram of IMS centralized services.

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

Figure 5 is a flow diagram of a call origination (calling) process for an ICS UE in the prior art.

6 is a flow chart showing a call-off (calling) process when an ICS UE does not recognize an emergency call in the prior art.

7 is a flow chart showing a call origination (calling) process when an ICS UE does not recognize an emergency call in the first embodiment of the present invention. FIG. 8 is a flowchart of a process of processing a roaming user by a P-CSCF according to a second embodiment of the present invention. Preferred embodiment of the invention

The core idea of the present invention is: When the P-CSCF determines in the IMS that the call is an emergency call and is an ICS session, or 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 the indication is The call is an emergency call, and the UE restarts the emergency call process according to the indication. Therefore, when the ICS UE cannot determine the emergency call, the emergency call is still guaranteed to be performed normally.

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

First embodiment

FIG. 7 is a flowchart of processing an emergency call by an IMS centralized service when a PS session control path is used in the IMS centralized service according to the embodiment, and describes a call processing when the user initiates an emergency call but the ICS UE does not recognize an emergency call. process. Includes the following steps:

701 703. The UE-A sends a CS bearer setup request through the bearer control path, and sends the CS bearer setup request to the ICCF through the VMSC, the MGCF, the I-CSCF/S-CSCF, and the ICCF waits for the control information in the control path to Carry out the next steps.

At the same time as steps 701 to 703, UE-A performs step 704.

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

The message further carries an ICS session identification tag or an ICS session media type, and the above parameter indicates that the session invitation request is an ICS session to distinguish 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 policy to determine whether it is an emergency call or an ordinary call;

2) Session type: According to the ICS session identification tag or ICS session media type carried in the session invitation request, it is judged whether it is an ICS session or a normal SIP session. 706. If the P-CSCF determines that the call is an emergency call and is an IMS centralized service session, returning an alternate service response (Alternative Service Response) to the UE, and including an emergency call indication, notifying the UE that the call is an emergency call;

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

If the P-CSCF determines that the call type is a normal call, the session invitation request is forwarded to the S-CSCF of the home network regardless of whether the session type is an ICS session or a normal SIP session. If the session type is an ICS session, the S-CSCF forwards the session to the ICCF and merges with the bearer control path, otherwise it is processed according to the normal SIP session.

If the P-CSCF determines that the call is an emergency call but not an ICS session, it may return an alternate service response (Alternative Service Response) to the UE and include an emergency call indication, notifying the UE that the call is an emergency call, or in a session invitation request. Join the emergency call identity and forward the request to the E-CSCF.

707. After receiving the replacement service response, the UE releases the circuit domain call established on the bearer control path and the corresponding 7-load;

708. 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 order to implement the above method, the present invention further provides an IP multimedia subsystem proxy call session control function module P-CSCF, where the P-CSCF is configured to receive a session invitation request of the user equipment, and check the content of the session invitation request. The call attribute, the call attribute includes a call type and a session type; if it is determined that the call is an emergency call, and is an IP multimedia subsystem centralized service ICS session, it is also used to return a replacement service response to the user equipment, and The emergency call indication is included in the response.

If it is determined that the call is a normal call, it is also used to forward the session invitation request to the S-CSCF of the home network; if it is determined that the call is an emergency call but not an ICS session, it is also used to return a replacement service response to the UE, and Contains an emergency call indication, or adds an emergency call identity to the session invitation request and forwards the request to the E-CSCF.

The P-CSCF checks the call class according to the coding scheme of the emergency call number in the local policy. If the called number of the session invitation request matches the coding scheme of the emergency call number in the local policy, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call; the P-CSCF is If the ICS session identification tag or the ICS session media type is found in the session invitation request, the ICS session identification tag or the ICS session media type check session type is considered to be an ICS session. Otherwise it is a normal SIP session

Second embodiment

FIG. 8 is a flow chart of the processing procedure of the P-CSCF to the roaming user in the embodiment, and describes a call processing procedure when the user initiates an emergency call but the UE (including the ICS UE) does not recognize the emergency call. Includes the following steps:

If the UE is an ICS UE, step 801 to 803 are performed. If the UE is a normal IMS UE, step 801 803 is not required to be performed.

801-803, in the same manner as step 501 503, the UE-A sends a CS bearer setup request through the bearer control path, and sends the call to the RUF in the ICCF through the VMSC, the MGCF, the I-CSCF/S-CSCF, and the ICCF waits for the control information in the control path. For the next steps;

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

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

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

2) Roaming status: According to the home network information carried in the user identifier and the current access network information of the user, whether the user is a roaming user: If the user's home network information is the same as the P-CSCF network information and the user's current access network is not at home If the home network information of the user or the user is different from the network information of the P-CSCF, the P-CSCF determines that the user is in a roaming state; if the home network information of the user is the same as the network information of the P-CSCF and the user currently accesses the network at the home location Then, the P-CSCF determines that the user is in a non-roaming state. 806. If the P-CSCF determines that the call is an emergency call, and the user is in a roaming state, returning an alternate service response (Alternative Service Response) to the UE, and including an emergency call indication, notifying the UE that the call is an emergency call;

If the P-CSCF determines that the call type is a normal call, the session invite request is forwarded to the S-CSCF of the home network regardless of whether the user is in the roaming state. If it is a session initiated by the ICS UE, the S-CSCF forwards the session to the ICCF and merges with the bearer control path, otherwise it is processed according to the normal SIP session.

If the P-CSCF determines that the call is an emergency call but the user is in a non-roaming state, then

The UE returns an alternate service response (Alternative Service Response) and includes an emergency call indication, notifying the UE that the call is an emergency call, or adding an emergency call identifier to the session invitation request, and forwarding the request to the E-CSCF.

In order to implement the above method, the present invention further provides another proxy call session control function module P-CSCF, where the P-CSCF is configured to receive a session invitation request sent by the user equipment, and check the call attribute carried in the session invitation request. The call attribute includes a call type and a roaming status. If the call is determined to be an emergency call, and the user terminal is in a roaming state, the call is also used to return an alternate service response to the user terminal, and includes an emergency call indication.

If the call is a normal call, the P-CSCF is further used to forward the session invitation request to the S-CSCF of the home network; if the call is determined to be an emergency call but the user terminal is in a non-roaming state, the P The -CSCF is also used to return an alternate service response to the user terminal UE, and includes an emergency call indication, or an emergency call identity is added to the session invitation 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 certain operator, that is, in this step, when the call is an emergency call and the user is a roaming user from the designated operator, the UE must be presented to the UE. Returns a replacement business response. If the call is an emergency call and the user is not a roaming user from the designated operator, the replacement service response may be returned to the UE, the UE is notified that the call is an emergency call, and the emergency call identifier may be added to the session invitation request, and the Request to go 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, the circuit domain call and the corresponding bearer established on the bearer control path need to be released.

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.

It is a matter of course that the invention may be embodied in various other forms and modifications without departing from the spirit and scope of the invention.

Industrial applicability

In summary, the method of the present invention and the P-CSCF are applied to the IMS originating process, and the call attribute is checked by the P-CSCF. If it is an emergency call and the ICS session or the user is in a roaming state, the replacement service response is rejected. The call includes an emergency call indication in the response, indicating that the user equipment re-initiates the emergency call, and achieves the purpose of ensuring that the emergency call is normally performed when the ICS UE cannot recognize the emergency call.

Claims

Claim

A method for implementing an emergency call service of an IP multimedia subsystem, characterized in that the method comprises the following steps:

2. The method of implementing of claim 1 wherein:

3. The method of implementing according to claim 1 or 2, characterized in that:

4. The method according to claim 1, wherein in step (b):

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 service call session control function S-CSCF of the home network,

If the P-CSCF determines that the call is an emergency call but is not an ICS session, the P-CSCF returns an alternate service response including an emergency call indication to the user equipment, to notify the user equipment that the call is an emergency call; Or the P-CSCF adds an emergency to the session invitation request. Call the identity and forward the request to the emergency call session control function E-CSCF.

5. The method of implementing of claim 1, wherein:

The user equipment is an ICS user equipment;

6. A proxy call session control function module P-CSCF of an IP multimedia subsystem, characterized in that:

The P-CSCF is configured to receive a session invitation request of the user equipment, and check a call attribute carried in the session invitation request, where the call attribute includes a call type and a session type; if the call is determined to be an emergency call, and The IP Multimedia Subsystem centralizes the ICS session, and is further configured to return an alternate service response to the user equipment, and include an emergency call indication in the response.

7. The proxy call session control function module according to claim 6, wherein: if it is determined that the call is a normal call, it is further used to forward the session invitation request to a serving call session control function of the home network. -CSCF;

8. The proxy call session control function module according to claim 6, wherein: the P-CSCF checks a call type according to an encoding scheme of an emergency call number in a local policy, if the session invitation request is If the calling number matches the coding scheme of the emergency call number in the local policy, the call initiated by the user is considered to be an emergency call, otherwise it is an ordinary call; and the P-CSCF is based on the ICS session identifier in the session invitation request. The tag or the ICS session media type check session type is considered to be an ICS session if it is found to carry the ICS session identification tag or the ICS session media type in the session invitation request, otherwise it is a normal SIP session.

10. The method of implementing of claim 9, wherein:

11. The method according to claim 9, wherein in step (b):

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 an alternate service response including 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 to the session invitation request, and forwards the request to the emergency call session control function E-CSCF.

12. A proxy call session control function module P-CSCF of an IP multimedia subsystem, characterized in that: The P-CSCF is configured to receive a session invitation request sent by the user equipment, and check a call attribute carried in the session invitation request, where the call attribute includes a call type and a roaming state; if the call is determined to be an emergency call, and the user terminal When in the roaming state, it is also used to return an alternate service response to the user terminal, and includes an emergency call indication;

The proxy call session control function module according to claim 12, wherein: if it is determined that the call is a normal call, the P-CSCF is further configured to forward the session invitation request to the S-CSCF of the home network. If it is determined that the call is an emergency call but the user terminal is in a non-roaming state, the P-CSCF is further configured to return an alternate service response to the user terminal UE, and include an emergency call indication, or add an emergency call in the session invitation request. Identify and forward the request to the E-CSCF.

14. An implementation method for an emergency call service of an IP multimedia subsystem, characterized in that the method comprises the following steps:

15. The method of implementing as claimed in claim 14, wherein:

If the home network information of the user is the same as the network information of the P-CSCF and the current access network of the user is not at the home location, or the home network information of the user is different from the network information of the P-CSCF, the P-CSCF determines The user is roaming;

The implementation method of claim 14, wherein, in step (b): the P-CSCF forwards the session invitation request to the home network, if it is determined that the call type of the call is an ordinary call. Service call session control function S-CSCF.