CN101932119B - Service implementation method and system of IP multimedia subsystem network - Google Patents

Abstract

A service implementation method of an IP multimedia subsystem network. When a UE in a roaming state successfully registers with an E-MSC in a local IMS network, the UE sends a session invitation message to an S-CSCF through a P-CSCF; According to the calling event trigger standard, the session invitation message is sent to the E-MSC; the E-MSC sends the initial address message to the PSTN where the called user is located according to the called number in the session invitation message; after receiving the address completion message returned by the PSTN, The E-MSC sends a ringing message to the UE; and after receiving the circuit domain response message sent by the PSTN, connects the IP media bearer between the E-MSC and the UE to the CS media bearer between the E-MSC and the PSTN, And through the S-CSCF and P-CSCF to send the response message of the initial session protocol SIP to the UE, to complete the establishment of the IMS session service.

Description

Service implementation method and system of IP multimedia subsystem network

technical field

The invention relates to the communication field, in particular to a method and system for realizing the service of an IP (Internet Protocol, Internet Protocol) multimedia subsystem network.

Background technique

In order to maintain the competitiveness of the 3rd Generation Partnership Project (abbreviated as 3GPP) in the field of mobile communications, 3GPP is currently working on the research on packet switched core network (Packet Switched Core, abbreviated as PS Core) and global mobile communications The evolution of the Universal Mobile Telecommunication System Radio Access Network (UTRAN) aims to enable the evolved PS Core (EPC) to provide higher transmission rates, shorter transmission delays, and support E -UTRAN (Evolved UTRAN, evolved UTRAN), GERAN (GSM EDGE radio access network, Global System for Mobile Communications Enhanced Data Rate Global System for Mobile Communications Evolution Technology Wireless Access Network), UTRAN, WLAN (Wireless Local Area Network, Wireless Local Area Network ) and mobility management between other non-3GPP access networks. This evolved mobile communication system is called an evolved packet domain system (Evolved Packet System, EPS for short).

At this stage, voice service is an important source of income for mobile operators, so how to ensure high-quality voice service in EPS is very important. At present, everyone is more concerned about using the traditional voice-based IP Multimedia Subsystem (IMS) to implement voice services.

FIG. 1 is a schematic diagram of an IMS network architecture in the prior art, including the following network elements:

101: User Equipment (User Equipment, UE for short), configured to register with a P-CSCF in the IMS network through an access device, and establish a session connection with a remote end;

102: Proxy Call Session Control Function (Proxy Call Session Control Function, P-CSCF for short), used to route messages and establish a security association with the UE;

103: Query the call session control function (Interrogating Call Session Control Function, referred to as I-CSCF), which is used to interact with the HSS (Home Subscriber Server, home subscriber server), request the HSS to allocate the S-CSCF for the UE, or query the corresponding S-CSCF;

104: Serving Call Session Control Function (Serving Call Session Control Function, S-CSCF for short), used to provide users with functions such as registration and call control;

105: Home Subscriber Server (HSS), used to store subscription data of the user and provide support for calls or sessions.

Using the architecture shown in Figure 1, when the user/UE is in the roaming state, the UE registers with the home network by accessing the P-CSCF of the visited location; after successful registration, if the user initiates a session service, the UE sends the session to the home network For the invitation message, the S-CSCF of the home network forwards the session invitation message to the called user, and the session control is completed by the home network.

In the case of local deployment of the IMS network, if the user roams to the IMS network of the visited location, and the intermediate network between the IMS network of the home location and the IMS network of the visited location is not deployed with an IMS network, it may not be possible to send the message of the UE ( For example, a registration message, a session invitation message) is routed to the home network, resulting in failure of the IMS service; similarly, a message (for example, a session invitation message) sent by the home network to the UE may also fail to be routed to the visited IMS network.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method and system for implementing IMS network services, so as to realize the exchange of signaling and media for calls initiated by visiting users in the local IMS network.

In order to solve the above problems, the present invention provides a service realization method of IP Multimedia Subsystem network, when the user equipment UE in the roaming state passes the proxy call session control function P-CSCF and the service call session control function of the local IP Multimedia Subsystem IMS network After the functional S-CSCF has successfully registered with the enhanced mobile switching center E-MSC of the local IMS network, the method includes:

The UE sends a session invitation message to the S-CSCF through the P-CSCF; the S-CSCF sends the session invitation message to the E-MSC according to the calling event trigger standard of the initial filtering criterion iFC;

The E-MSC sends an initial address message to the public switched telephone network PSTN where the called user is located according to the called number in the session invitation message;

After receiving the address completion message returned by the PSTN, the E-MSC sends a ringing message to the UE through the S-CSCF and P-CSCF; and after receiving the circuit domain response message sent by the PSTN After that, connect the IP media bearer between the E-MSC and the UE with the circuit-switched CS media bearer between the E-MSC and the PSTN, and send The UE sends a response message of the initial session protocol SIP to complete the establishment of the IMS session service.

In addition, after receiving the session invitation message, the E-MSC also performs call control according to the locally stored user data of the UE, and sends the initial address message after the call control is completed.

In addition, the iFC is generated by the E-MSC; the E-MSC sends the iFC to the S-CSCF in the following manner:

During the registration process of the UE, after receiving the registration request sent by the S-CSCF, the E-MSC sends a registration response message to the S-CSCF, and the message includes the iFC.

In addition, the E-MSC obtains and stores the user data of the UE in the following manner:

During the registration process of the UE, after the E-MSC receives the registration request sent by the S-CSCF, it sends a location update request to the Home Subscriber Server HSS or the Home Location Register HLR of the UE's home network, to obtain user data of the UE;

After receiving the location update request, the HLR or HSS returns the user data of the UE to the E-MSC;

The E-MSC stores user data of the UE.

In addition, after receiving the session invitation message, the E-MSC establishes the IP media bearer by sending a SIP response message to the UE;

The E-MSC and the PSTN establish the CS media bearer through the interaction of the initial address message and the address complete message.

The present invention also provides a service realization system of an IP multimedia subsystem network, which serves as a visited network to provide services for a UE in a roaming state; the system includes: P-CSCF, S-CSCF, and E-MSC; wherein:

The P-CSCF is configured to send the session invitation message to the S-CSCF after receiving the session invitation message sent by the UE;

The S-CSCF is configured to send the session invitation message to the E-MSC according to the calling event trigger standard of iFC;

The E-MSC is used to send an initial address message to the PSTN where the called user is located according to the called number in the session invitation message; after receiving the address completion message returned by the PSTN, through the S-CSCF and The P-CSCF sends a ringing message to the UE; and after receiving the circuit domain response message sent by the PSTN, sends the IP media bearer between the E-MSC and the UE to the E-MSC It is connected to the CS media bearer between the PSTNs, and sends a SIP response message to the UE through the S-CSCF and P-CSCF to complete the establishment of the IMS session service.

In addition, the E-MSC is further configured to perform call control according to the user data of the UE stored locally after receiving the session invitation message, and send the initial address message after the call control is completed.

In addition, the E-MSC is also used to generate the iFC, and send the iFC to the S-CSCF in the following manner:

During the registration process of the UE, after receiving the registration request sent by the S-CSCF, the E-MSC sends a registration response message to the S-CSCF, and the message includes the iFC.

In addition, the E-MSC is also configured to send a location update request to the HSS or HLR of the home network of the UE after receiving the registration request sent by the S-CSCF during the registration process of the UE, so as to obtain The user data of the UE, and store the user data of the UE returned by the HLR or HSS.

In addition, the E-MSC is further configured to establish the IP media bearer by sending a SIP response message to the UE after receiving the session invitation message;

The E-MSC and the PSTN establish the CS media bearer through the interaction of the initial address message and the address complete message.

In summary, the present invention sets enhanced mobile switching center (E-MSC) in the local IMS network, after the visiting user registers successfully in E-MSC, by E-MSC in the local IMS network, the call initiated by the visiting user is carried out. Call control, and switching of signaling and media.

Using the IMS network localization deployment architecture provided by the present invention, and the system and method for implementing CS services by using EPS network access, solve the roaming problem of the original IMS network local deployment, and at the same time use standard IMS access terminals to reduce the network evolution process of users make repeated investments.

Description of drawings

FIG. 1 is a schematic diagram of an IMS network architecture in the prior art;

FIG. 2 is a first architecture diagram of a service implementation system of an IMS network according to an embodiment of the present invention;

FIG. 3 is a second architecture diagram of a service realization system of an IMS network according to an embodiment of the present invention;

Fig. 4 is a flow chart of a method for registering using the system framework of the present invention;

Figure 4a is a flow chart of the first method for selecting a local IMS network for the UE/user when the UE accesses the local IMS network and initiates registration through the local IMS network;

FIG. 4b is a flowchart of a second method for selecting a local IMS network for a user of the UE when the UE accesses the local IMS network and initiates registration through the local IMS network;

FIG. 4c is a flowchart of a method for selecting a local IMS network by the UE when the UE accesses the local IMS network and initiates registration through the local IMS network;

Figure 4d is a flow chart of the method for obtaining the IMSI of the corresponding user after the E-MSC receives the registration request message;

FIG. 5 is a third architecture diagram of a service realization system of an IMS network according to an embodiment of the present invention;

FIG. 6 is a flowchart of a method for initiating a call using the system architecture of the present invention;

FIG. 7 is a flowchart of a method for terminating a call using the system architecture of the present invention.

Detailed ways

The core idea of the present invention is that an enhanced mobile switching center (E-MSC) is set in the local IMS network. The IMS network performs call control and exchange of signaling and media for calls initiated by visiting users.

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

Fig. 2 is the architecture diagram 1 of the service implementation system of the IMS network of the embodiment of the present invention, including:

201: User Equipment (User Equipment, referred to as UE); has IMS capabilities, supports the SIP protocol, and is used to register with the P-CSCF in the IMS network through the access device, and establish a session connection with the remote end;

202: Enhanced Mobile Switching Center (Enhanced Mobile Switch Center, referred to as E-MSC) server, which is a new network element of the present invention, E-MSC server (abbreviated as E-MSC) is a physical entity, with circuit switching (media switching ) capability and signaling protocol conversion capability, and can realize local registration of visiting users, and support standard ISC interface and Cx interface.

For the local IMS network, the E-MSC implements the functions of the HSS and AS (Application Server); from the perspective of the CS (Circuit Switching) network, the E-MSC implements the functions of the MSC.

Specifically, E-MSC has the following functions:

With protocol conversion function, it can convert SIP signaling and circuit domain related protocol signaling to each other, and can convert SIP signaling received from ISC interface and Cx interface into corresponding circuit domain signaling;

Possess mobile switching capabilities (that is, signaling and media switching capabilities), and be able to perform media switching between IP bearers and circuit domain bearers;

When the E-MSC receives an incoming call request (namely, a call termination request) initiated by a remote user, it can act as a user agent to initiate a session invitation request to a local IMS terminal roaming;

With local registration capability, when receiving the query message sent by the I-CSCF, it can assign the local S-CSCF to the visiting user; when receiving the registration request of the visiting user, it can obtain the corresponding IMS private user ID carried in the registration request. IMSI (International Mobile Subscriber Identifier, International Mobile Subscriber Identifier); if there is no local user data, the user data can be obtained from the HSS/HLR of the user's home network;

Can generate E-MSC trigger criteria (also known as initial filter criteria, namely Initial FilterCriteria, referred to as iFC) and trigger address (ie E-MSC address);

When receiving the roaming number request sent by HSS/HLR, E-MSC can assign a local roaming number;

When receiving a call establishment request (for example, a session invitation message, an initial address message), it has the ability to establish a bearer for the call and perform media and signaling exchange.

203: Call Session Control Function (Call Session Control Function, referred to as CSCF), which can be further divided into: Interrogating Call Session Control Function (Interrogating CSCF, referred to as I-CSCF), Proxy Call Session Control Function (Proxy Call Session Control Function, P-CSCF for short) and Serving Call Session Control Function (Serving CSCF, S-CSCF for short). in:

The P-CSCF is used to route the message and establish a security association with the terminal; in addition, after receiving the registration request of the visiting user, the P-CSCF can route the request to the I-CSCF of the local IMS network;

The I-CSCF is used to interact with the E-MSC, requesting the E-MSC to allocate an S-CSCF for the user, or query the S-CSCF where the user is located;

The S-CSCF is used to provide users with functions such as registration and call control.

204: Home Location Register (Home Location Register, HLR for short) or Home Subscriber Server (Home Subscriber Server, HSS for short);

HSS/HLR is used to store user subscription data, provide support for calls or sessions, and return user data to E-MSC when receiving a location update request sent by E-MSC.

HLR can be considered as a subset of HSS, serving the traditional CS (Circuit Switched, Circuit Switched) domain and PS (Packet Switched, Packet Switched) domain, HLR and HSS can be integrated, located in the same physical entity, or located in different On the physical entity, there is an interface between the HLR and the HSS at this time to realize information exchange.

Fig. 3 is the second architecture diagram of the service implementation system of the IMS network according to the embodiment of the present invention. This architecture diagram includes the network elements involved in the registration using the service system of the IMS network of the present invention, which shows the network elements omitted in Fig. 2 Each network element in the access network part: Mobility Management Entity (MME for short), Serving Gateway (S-GW for short), Packet DataNetwork Gateway (PDN GW or PDN for short). -GW), Dynamic Host Configuration Protocol Server (Dynamic Host Configuration Protocol Server, referred to as DHCP Server); and shows the Domain Name System (DomainName System, referred to as DNS) omitted in Figure 2; in addition, CSCF is further subdivided into P - CSCF, I-CSCF and S-CSCF; where:

Mobility Management Entity (MME) is a control plane entity, used to temporarily store user information, and is responsible for managing and storing UE context (such as UE/user identity, mobility management status, user security parameters, etc.), assigning temporary identities to users, When the UE is camped in the tracking area or the network, it is responsible for authenticating the user;

Serving Gateway (S-GW), which is a user plane entity, is responsible for routing and processing user plane data;

A packet data network gateway (P-GW) is a gateway for a UE to access a PDN (Packet Data Network, packet data network). When the P-GW receives the message of obtaining the full name of the P-CSCF sent by the UE, it returns the full name of the P-CSCF obtained from the DHCP server to the UE.

The P-GW and the S-GW can be co-located in one physical entity.

Domain Name System (DNS), used to translate domain names into corresponding IP addresses.

A dynamic host configuration protocol server (DHCP Server), configured to dynamically provide the full name or address of the P-CSCF, and provide a DNS address.

The specific functions of each network element shown in FIG. 3 will be described in detail below.

Fig. 4 is the flow chart of the method for registering using the system architecture of the present invention; in this process, after the E-MSC receives the registration request message forwarded by the S-CSCF, if there is no corresponding user data in the E-MSC, the HSS /HLR initiates a location update request to obtain user data; after the user data is successfully obtained, it returns a registration response to the S-CSCF, and the response message contains the trigger criteria generated by the E-MSC (also called the initial filter criteria, namely Initial Filter Criteria , referred to as iFC) and trigger address; As shown in Figure 4, the method includes the following steps:

401. The UE sends a registration request message to the P-CSCF of the local IMS network (ie, the P-CSCF of the visited network, referred to as the local P-CSCF for short) in the roaming state, and the message carries the user identity;

402. After receiving the registration request message, the local P-CSCF forwards the message to the I-CSCF of the local IMS network (that is, the I-CSCF of the visited network, referred to as the local I-CSCF);

In the present invention, various methods can be adopted to forward the registration request message to the local I-CSCF. For details, please refer to the description of FIGS. 4a-4c below.

403. After receiving the registration request message, the local I-CSCF sends a query message to the E-MSC of the local IMS network to query the address of the S-CSCF;

404. The E-MSC assigns an address of an S-CSCF (local S-CSCF for short) of the local IMS network, and returns it to the local I-CSCF;

405. The local I-CSCF sends a registration request message to the local S-CSCF;

406. After receiving the registration request message, the local S-CSCF sends the registration request message to the E-MSC;

407. After receiving the registration request message, if there is no corresponding user data in the E-MSC, send a location update request to the HSS/HLR of the UE's home network to obtain user data;

If there is corresponding user data in the E-MSC, the E-MSC identifies the UE (user) as registered, and returns a registration response message to the local S-CSCF, which carries the trigger standard generated by the E-MSC (also called For the initial filter criteria, i.e. Initial Filter Criteria, referred to as iFC) and the trigger address (ie the address of the E-MSC), and jump to step 412;

The triggering criteria above include: triggering criteria for registration events, calling events, called events, and other events. Wherein, the trigger standard of the registration event may trigger the local S-CSCF to perform third-party registration.

User data includes: user location information, subscription information, business data and other information.

In this step, E-MSC needs to use the user's IMSI (International Mobile SubscriberIdentifier, International Mobile Subscriber Identifier) to obtain user data, if the user identification in the registration request message is not IMSI, then E-MSC can use multiple methods to obtain user data For the specific method, please refer to the description of Figure 4d below.

408. The HSS/HLR sends a request for inserting user data to the E-MSC. The message carries the user data of the corresponding user, and the user data includes the service data signed by the user in the CS domain (referred to as the CS domain service data of the user for short);

409. The E-MSC saves the received user data, and returns a user data insertion response message to the HSS/HLR;

410. After receiving the user data insertion response message sent by the E-MSC, the HSS/HLR returns a location update response message to the E-MSC;

411. After receiving the location update response message, the E-MSC identifies that the user has registered, and returns a registration response message to the local S-CSCF, which carries the trigger criteria (i.e. iFC) and trigger address (i.e. E-MSC) generated by the E-MSC. - the address of the MSC);

The triggering criteria above include: triggering criteria for registration events, calling events, called events, and other events. Wherein, the trigger standard of the registration event will trigger the S-CSCF to perform third-party registration.

412-414. The local S-CSCF sends a registration completion message to the UE, notifying the UE that the registration is successful;

415. The S-CSCF sends a third-party registration request to the E-MSC according to the registration event trigger standard in the iFC, and the request carries the user identifier of the UE and the current access address of the UE;

416. After receiving the third-party registration request, the E-MSC saves the third-party registration information such as the user ID of the UE and the current access address of the UE, and returns a registration completion message to the local S-CSCF.

It should be noted that steps 415-416 are optional steps; the E-MSC saves the current access address of the UE so as to realize service continuity in the future; the specific method for realizing service continuity is beyond the scope of the present invention.

Figure 4a is a first method for selecting a local IMS network for the UE/user when the UE accesses the local IMS network and initiates registration through the local IMS network (that is, in step 402, the received registration request message is forwarded to the local IMS network). - method of CSCF) flowchart. In this process, the access network element P-CSCF of the local IMS network selects the local IMS network for the user.

In the prior art, after receiving the registration request message, the P-CSCF will forward the registration request message to the I-CSCF of the home network according to the home domain name carried in the message; and in this embodiment, the P-CSCF will After receiving the registration request message, according to the operator's policy, the registration request message is directly routed to the local I-CSCF, and the local I-CSCF selects the E-MSC of the local IMS network for registration.

As shown in Figure 4a, the method specifically includes the following steps:

4a01 (that is, step 401), the UE sends a registration request message to the local P-CSCF, and the message carries a home domain name and a user identity;

4a02. After receiving the registration request message, the P-CSCF judges whether to select the local IMS network according to the user identity and the operator's policy (that is, judges whether to forward the received registration request message to the local I-CSCF for processing), specifically Judgment and selection strategies can be:

For all users, the local I-CSCF is selected to forward the registration request message (that is, the local I-CSCF is configured to unconditionally select the local IMS network); or

Determine whether the corresponding user has signed an IMS interconnection agreement according to the IMS interconnection agreement signed by the operator and the user identity. For users who have not signed an IMS interconnection agreement, select the local I-CSCF to forward the registration request message; for those who have signed an IMS interconnection agreement The user may choose the I-CSCF of the user's home network to forward the registration request message.

4a03. When it is determined that the local I-CSCF needs to be selected (that is, the local IMS network is selected for local registration), the P-CSCF forwards the registration request message to the local I-CSCF.

Figure 4b is a second method for selecting a local IMS network for the user of the UE when the UE accesses the local IMS network and initiates registration through the local IMS network (that is, in step 402, the received registration request message is forwarded to the local IMS network). - method of CSCF) flowchart. In this process, the DNS selects the local IMS network for the user.

In the prior art, after receiving the registration request message, the P-CSCF needs to query the DNS for the I-CSCF address of the user's home location according to the home domain name carried in the message, and the DNS will translate the home domain name into an I-CSCF address of the home network. - the address of the CSCF; and in this embodiment, the DNS will translate the home domain name into the I-CSCF address of the local IMS network according to the operator's policy.

As shown in Figure 4b, the method specifically includes the following steps:

4b01 (that is, step 401), the UE sends a registration request message to the local P-CSCF, and the message carries a home domain name and a user identity;

4b02. After receiving the registration request message, the P-CSCF sends an I-CSCF address query message to the local DNS to query the address of the I-CSCF of the home network, and the query message carries the home domain name carried in the registration request message;

4b03. After receiving the above query message, the DNS performs the following processing according to the operator's policy:

Translate all attributed domain names to local I-CSCF addresses; or

Judging whether the operator of the network corresponding to the domain name has signed an IMS interconnection agreement according to the IMS interconnection agreement signed by the operator, translates the domain name of the network that has not signed an IMS interconnection agreement into a local I-CSCF address; The home domain name of the network of the interconnection agreement is translated into the address of the I-CSCF of the corresponding home network;

4b04. The DNS returns the address of the I-CSCF to the P-CSCF.

Figure 4c is a method for selecting a local IMS network by the UE when the UE accesses the local IMS network and initiates registration through the local IMS network (that is, the local P-CSCF in step 402 forwards the received registration request message to the local I-CSCF method) flowchart. In this process, after the UE obtains the full name of the P-CSCF, the home domain name is set according to the full name of the P-CSCF. The process shown in Figure 4c occurs before step 401, and specifically includes the following steps:

4c01. The UE sends a message to obtain the full name of the P-CSCF to the P-GW;

4c02. The P-GW requests the full name of the P-CSCF from the DHCP server;

4c03. The DHCP server returns the full name of the P-CSCF to the P-GW;

4c04. The P-GW returns the full name of the P-CSCF to the UE;

4c05. After receiving the full name of the P-CSCF, if the UE wants to use the local IMS service, set the home domain name according to the full name of the P-CSCF (that is, set the string after the "" character in the full name of the P-CSCF as the home domain name); Thereafter, the UE includes the home domain name in the registration request message in step 401 for registration. In step 402, the local P-CSCF forwards the message to the local I-CSCF according to the home domain name in the registration request message. CSCF.

Figure 4d is a flow chart of the method for obtaining the IMSI of the corresponding user after the E-MSC receives the registration request message; this flow describes the method for obtaining the IMSI of the corresponding user after the E-MSC receives the registration request message in step 407 of Figure 4 , as shown in Figure 4d, the method includes the following steps:

4d01. After receiving the registration request message, the E-MSC extracts the user ID in the message, and judges whether the user ID is an IMSI, if not, executes step 4d02, otherwise the process ends;

4d02. If the user identifier is not an IMSI, the E-MSC can obtain the corresponding IMSI in one of the following ways:

Method 1: including the following sub-steps:

a1: If the user identity is a temporary private user identity derived from the IMSI, the E-MSC reversely deduces the temporary private user identity to obtain the corresponding IMSI; or

Method 2: including the following sub-steps:

b1: If the user ID is an IMS private user ID, the E-MSC can send a registration rejection message to the UE, rejecting this registration, and include in the message an instruction to the user to register using the IMSI or a temporary private user ID derived from the IMSI Information;

b2: After receiving the registration rejection message, the UE re-initiates registration using the IMSI or the temporary private user identity derived from the IMSI according to the above information contained in the message;

b3: After receiving the registration request resent by the UE, the E-MSC obtains the IMSI from the request, or obtains the temporary private user identity from the request and reversely deduces it to obtain the corresponding IMSI; or

Method 3: including the following sub-steps:

c1: The E-MSC sends a SIP (Session Initial Protocol, initial session protocol) subscription or SIP query message to the UE to obtain the IMSI of the UE;

c2: After receiving the SIP SUBSCRIBE or SIP Query message, the UE returns the user IMSI to the E-MSC; or

Method 4: including the following sub-steps:

d1: The E-MSC uses the IMS private user identity carried in the registration request to obtain the corresponding IMSI from the HSS of the UE's home network;

d2: The HSS returns the IMSI bound to the IMS private user identity to the E-MSC.

FIG. 5 is the third architecture diagram of the service implementation system of the IMS network according to the embodiment of the present invention. This architecture diagram includes the network elements involved when the service implementation system of the IMS network of the present invention is used to make a call, which shows the network elements in FIG. 2 Each network element in the omitted access network part: Mobility Management Entity (MME), Serving Gateway (S-GW), Packet Data Network Gateway (P-GW); and CSCF is further subdivided into P-CSCF and S -CSCF; In addition, this architecture diagram also shows the network elements included in the CS network in Figure 2: media gateway (Media Gateway, MGW for short), gateway mobile switching center (Gateway Mobile Switching Center, GMSC for short) , Public Switched Telephone Network (Public Switched Telephone Network, referred to as PSTN); where:

A media gateway (MGW), configured to provide media bearer;

Gateway Mobile Switching Center (GMSC), for signaling routing upon receipt of an initial address message;

Public Switched Telephone Network (PSTN), here refers to the fixed telephone network.

The specific functions of each network element shown in FIG. 5 will be described in detail below.

Fig. 6 is the flow chart of the method for calling out using the system architecture of the present invention; in the calling out process, the local S-CSCF triggers the calling event trigger standard in the iFC to route the session invitation message to the E-MSC, and the E-MSC Perform signaling protocol conversion, convert IMS signaling into CS signaling, and establish a call connection with the remote end; the process shown in Figure 6 specifically includes the following steps:

601. The UE that has successfully performed local registration sends a session invitation message to the local P-CSCF, and the message carries the calling number and the called number;

602. The local P-CSCF forwards the session invitation message to the local S-CSCF according to the routing information recorded in the UE registration process;

603. After receiving the session invitation message, the local S-CSCF triggers third-party call control according to the calling event trigger standard in the iFC (that is, the local S-CSCF does not perform call control, but the E-MSC performs call control), and sends The session invite message is routed to the E-MSC;

604. The E-MSC performs call control on the call according to the user data acquired and stored during the UE registration process (for example, judging whether the UE is allowed to initiate a call). After the call control is completed, the local S-CSCF and the local P-CSCF report to the UE Send a SIP response message (that is, a 200OK message, not shown in the figure) to set up a media bearer (IP bearer) between the UE and the E-MSC; then send an initial address message to the PSTN where the called user is located according to the called number ( IAM), the message carries the calling number and called number.

605. When the called user terminal rings, the PSTN returns an address completion message (ACM) to the E-MSC;

Through the interaction of steps 604 and 605, the media bearer (CS bearer) between the E-MSC and the PSTN where the called user is located is established.

606-608. The E-MSC converts the address completion message (ACM) of the circuit domain into a ringing message of SIP, and forwards the ringing message to the calling user terminal (UE) through the local S-CSCF and the local P-CSCF;

609. After the called user in the PSTN connects to the call, send a circuit domain response message (ANM) to the E-MSC;

610-612. After receiving the response message (ANM) in the circuit domain, the E-MSC connects the media bearer between itself and the calling user terminal (UE) and the remote PSTN, and sends a message to the local S-CSCF and the local P-CSCF The calling user terminal (UE) sends a SIP response message (200OK message) to notify the calling user to answer and complete the establishment of the IMS session service.

Fig. 7 is a flow chart of a method for terminating a call using the system framework of the present invention; in the process of terminating a call, after receiving a request for setting up a terminating call (initial address message) in the circuit domain, the E-MSC, as a user agent, sends a message to the called user (UE) initiates a SIP session setup request (session invite message), completes the setup of the call; the method shown in Figure 7 comprises the steps:

701. When the PSTN call has roamed to the UE (called user) of the local IMS system, the PSTN sends an initial address message (IAM) to the GMSC of the home network of the called user, and the message carries the calling number and the called number (i.e. UE's number);

702. After receiving the initial address message, the GMSC of the home network of the called user sends a routing request to the HSS/HLR of the home network of the called user to obtain the routing information of the called user;

703. HSS/HLR learns that the called user is currently roaming in the local IMS network under the jurisdiction of the E-MSC according to the location update request (step 407) sent by the E-MSC during the registration process of the called user (UE), and therefore reports to the E-MSC Send a request to provide a roaming number, which includes the called number;

704-705. After receiving the request for providing a roaming number, the E-MSC allocates a local roaming number, saves the corresponding relationship between the roaming number and the called number; and returns the roaming number to the HSS of the called user's home network through a response message /HLR, the HSS/HLR of the home network of the called user returns the roaming number to the GMSC;

706. The GMSC sends an initial address message (IAM) to the E-MSC according to the roaming number, so as to route the call to the E-MSC, and the message carries the roaming number (as the called number) and calling number information;

707. After receiving the initial address message (IAM), the E-MSC judges that the called number in the message is a roaming number assigned by the network element, so it finds the previously saved called number according to the roaming number; the E-MSC finds the called number according to the called number The called number and the user data obtained during the UE registration process are used to control the call. After the call control is completed, the called number (ie, the number of the UE) is used to replace the roaming number in the initial address message; and the S-CSCF sends the call to the called The user (UE) sends a session invitation message to establish a call, and establishes a media bearer (IP bearer) between the E-MSC and the called user terminal (UE); the above-mentioned session invitation message carries the called number (that is, the number of the UE) and calling number;

708. The S-CSCF forwards the session invitation message to the called user terminal (UE) through the P-CSCF according to the IP address and routing path registered by the user;

709-710. After the called user terminal (UE) rings, the UE sends a SIP ringing message to the E-MSC through the P-CSCF and the S-CSCF;

711-712. After receiving the ringing message, the E-MSC converts it into an Address Completion Message (ACM) in the circuit domain, and sends it to the PSTN where the calling user is located through the GMSC;

So far, the E-MSC has established a media bearer (CS bearer) between itself and the PSTN where the calling user is located.

713-714. After the called user connects the call, the UE sends a SIP connection message to the E-MSC through the P-CSCF and the S-CSCF;

715-716. After receiving the SIP connection message, the E-MSC connects the media bearer between the E-MSC and the called user terminal (UE) and PSTN, and converts the SIP connection message into a response message of the circuit domain ( ANM), sent to the PSTN where the calling user is located through the GMSC.

Claims (10)

1. the service implementation method of an IP Multimedia System network, it is characterized in that, when the Proxy Call Session Control Function P-CSCF of the user equipment (UE) in roaming state by local IP Multimedia System IMS network and service call conversation control function S-CSCF are after the E-MSC of enhancing mobile switching centre of local IMS network successfully registers, the method comprises:

UE sends to described S-CSCF by described P-CSCF by session invitation message; Described S-CSCF sends to described E-MSC according to the caller event trigger standard of initial filter standard or norm iFC by described session invitation message;

Described E-MSC is the public switch telephone network PSTN transmission initial address message to called subscriber place according to the called number in described session invitation message;

Receive the address that described PSTN returns and complete after message, described E-MSC sends ALERTING message by described S-CSCF and P-CSCF to described UE; And after the response message of circuit domain that receives described PSTN transmission, described E-MSC is connected with the circuit switching (CS) media bearer between described PSTN with IP media bearer and described E-MSC between described UE, and the response message that sends initial session protocol SIP to described UE by described S-CSCF and P-CSCF, complete the foundation of IMS session service.

2. the method for claim 1, is characterized in that,

Described E-MSC receives after described session invitation message, also according to the user data of the described UE of this locality storage, calls out control, calls out and has controlled the described initial address message of rear transmission.

3. the method for claim 1, is characterized in that,

Described iFC is generated by described E-MSC; Described E-MSC sends to described S-CSCF by described iFC in the following way:

In the registration process of described UE, receive after the registration request of described S-CSCF transmission, described E-MSC sends registration reply message to described S-CSCF, comprises described iFC in this message.

4. method as claimed in claim 2, is characterized in that,

Described E-MSC obtains and stores the user data of described UE in the following way:

In the registration process of described UE, when described E-MSC receives after the registration request of described S-CSCF transmission, home subscriber server HSS or attaching position register HLR to the home network of described UE send position updating request, to obtain the user data of described UE;

Receive after described position updating request, described HLR or HSS return to described E-MSC by the user data of described UE;

Described E-MSC stores the user data of described UE.

5. the method for claim 1, is characterized in that,

Receive after described session invitation message, described E-MSC sets up described IP media bearer by send the response message of SIP to described UE;

Described E-MSC and described PSTN complete the described CS media bearer of setting up alternately of message by described initial address message and address.

6. a business realizing system for IP Multimedia System network, this system provides business as visited network for the UE in roaming state; This system comprises: Proxy Call Session Control Function P-CSCF, service call conversation control function S-CSCF, the enhancing E-MSC of mobile switching centre; Wherein:

Described P-CSCF, for after receiving the session invitation message of described UE transmission, sends to described S-CSCF by described session invitation message;

Described S-CSCF is for sending to described E-MSC according to the caller event trigger standard of initial filter standard or norm iFC by described session invitation message;

Described E-MSC is for the public switch telephone network PSTN transmission initial address message to called subscriber place according to the called number of described session invitation message; Complete after message receiving the address that described PSTN returns, by described S-CSCF and P-CSCF, to described UE, send ALERTING message; And after the response message of circuit domain that receives described PSTN transmission, described E-MSC is connected with the circuit switching (CS) media bearer between described PSTN with IP media bearer and described E-MSC between described UE, and the response message that sends initial session protocol SIP to described UE by described S-CSCF and P-CSCF, complete the foundation of multimedia subsystem, IMS session service.

7. system as claimed in claim 6, is characterized in that,

Described E-MSC, also for after receiving described session invitation message, calls out control according to the user data of the described UE of this locality storage, calls out and has controlled the described initial address message of rear transmission.

8. system as claimed in claim 6, is characterized in that,

Described E-MSC is also for generating described iFC, and in the following way described iFC sent to described S-CSCF:

In the registration process of described UE, receive after the registration request of described S-CSCF transmission, described E-MSC sends registration reply message to described S-CSCF, comprises described iFC in this message.

9. system as claimed in claim 6, is characterized in that,

Described E-MSC is also for the registration process at described UE, receive after the registration request of described S-CSCF transmission, HSS or HLR to the home network of described UE send position updating request, to obtain the user data of described UE, and store the user data of the described UE that described HLR or HSS return.

10. system as claimed in claim 6, is characterized in that,

Described E-MSC, also for after receiving described session invitation message, sets up described IP media bearer by send the response message of SIP to described UE;

Described E-MSC and described PSTN complete the mutual of message by described initial address message and address, set up described CS media bearer.