WO2008020404A2

WO2008020404A2 - Method for reducing system signalling interchanging processes for multimedia subsystem

Info

Publication number: WO2008020404A2
Application number: PCT/IB2007/053241
Authority: WO
Inventors: Yi Zhou
Original assignee: Utstarcom Telecom Co., Ltd
Priority date: 2006-08-16
Filing date: 2007-08-14
Publication date: 2008-02-21
Also published as: CN1937597A; CN1937597B; WO2008020404A3

Abstract

The invention provides a method of signalling interchange in IMS, able to reduce the number of the signalling interchange and improve system stability. In the signalling interchange among a network element, SLF and HSS, the method comprises sequentially the following steps: the network element receiving a message containing a user ID; according to the user ID, the network element querying in its buffer storage HSS information corresponding to the user ID; and the network element building signalling interchange with a home HSS determined by the HSS information. Thus, by adding the buffer storage to network element, the method reduces the interchanging process that I-CSCF queries SLF about the subscriber's home HSS. Therefore, the method reduces performance loss due to the number of IMS signalling interchange and improves system stability without changing the existing IMS network infrastructure and influencing the IMS session and service processing mechanism.

Description

Method for Reducing System Signalling Interchanging Processes for

Multimedia Subsystem

FIELD OF THE INVENTION

The present invention relates to an IMS (IP Multimedia Subsystem), and more particularly, to a method for simplifying a multimedia subsystem and reducing system signalling interchanging processes.

BACKGROUND OF THE INVENTION

IMS is an IP-supporting multimedia subsystem defined by the 3GPP (3rd Generation Partnership Project) standardization organization. As compared with other communication core networks such as PSTN, GSM, CDMA and 3 G CS domain, IMS is remarkably characterized by adopting techniques such as extensible open protocol, independency of communication with access modes, separation of control function from bearing function, separation of call from session, separation of calling party session control from called party session control, separation of traffic network from basic network. Thanks to the above technical advantages, IMS can support both fixed and mobile terminals, bear simultaneously traditional speech services, data and video services as well as any other kinds of multimedia services, and make the service control logic clear and concise.

Nevertheless, the above advantages owned by IMS are obtained at a cost of performance loss to a certain extent, and such performance loss mainly comprises:

1) protocol efficiency of SIP (Session Initiation Protocol): SIP adopts text coding mode, which has merits such as close to natural language and convenient to debug and expansion, but as for the same information amount, the decoding efficiency of a text message generally is lower than that of the binary format by 10 times or more; in addition, flexibility of the SIP increases the number of message interchange, for example, for a speech call, the number of message interchange of SIP may be more than 3 times over that of ISUP;

2) a loose-coupling network infrastructure: this infrastructure has a main object of reducing logical dependency among network elements. Taking a two-party call for example, the call process sequentially passes the following network elements: a calling party roaming network P-CSCF (Proxy Call Session Control Function), a calling party home network I-CSCF (Interrogating Call Session Control Function) and S-CSCF (Serving Call Session Control Function), a called party home network I-CSCF and S-CSCF, a called party roaming network P-CSCF, at the same time, process of a calling party service is triggered by a calling party home S-CSCF processing service to AS (Application server) for service control, and process of a called party service is triggered by a called party home S-CSCF processing service to AS for service control; as compared with GSM, CDMA and 3 G CS networks, the number of network elements and network element interchanging processes involved in the flow are increased.

Fig.1 is a schematic diagram showing a signalling interchanging process at a subscriber's home network in IMS according to the prior art. Fig.1 shows a standard flow for I-CSCF to process REGISTER message, defined by the 3GPP specification (see 3GPP TS 23.288), which is an interchanging process of querying a subscriber's home HSS (Home Subscriber Server) by accessing SLF (Subscription Locator Function), wherein SLF is a database in which mapping relationship between "user ID (user identity)" and "HSS name" is stored. The detailed process is as follows:

I-CSCF receiving a registration message SIP REGISTER containing the "user ID";

I-CSCF sending the SLF a query request DX SLF QUERY, in which the "user ID" derived from the registration message SIP REGISTER is contained.

SLF making a query according to the "user ID" derived from the query request DX SLF QUERY to obtain the "home HSS name";

SLF sending a response message DX_SLF_RESP to I-CSCF, the message containing the "home HSS name";

5)~6) I-CSCF obtaining the "home HSS name" and performing a subsequent process CX_QUERY/CX_RESPONSE between I-CSCF and the home HSS.

It follows that, during the home subscriber network process, if a session/call in the IMS system requires accessing the subscriber's home HSS, I-CSCF/S-CSCF/AS is required to access the concentrated SLF database to query and obtain the home HSS name. In this case, two problems arise: 1) the SLF query process increases the number of signalling interchange in the whole system and thus increases the system overhead; 2) the SLF, as an important single point in the home network, will possibly render the whole system unstable due to single point fault.

SUMMARY OF THE INVENTION

In view of the above problems, the present invention aims to provide a method of signalling interchange in IMS, able to reduce the number of the signalling interchange and improve system stability.

In the method of signalling interchange in IMS according to the invention, the signalling interchange is made among a network element, SLF and HSS, the network element having a buffer storage, the method comprising sequentially the following steps:

(I) the network element receiving a message containing a user ID;

(II) according to the user ID, the network element querying in its buffer storage about whether there is HSS information corresponding to the user ID;

(III) if the HSS information corresponding to the user ID is found out in the buffer storage, proceeding to step (V); if no HSS information corresponding to the user ID is found out in the buffer storage, sending the SLF a request containing the user ID for querying the HSS information,;

(IV) the SLF returning the HSS information queried according to the user ID to the network element; and

(V) the network element building signalling interchange with a home HSS determined by the HSS information.

Preferably, a table of mapping relationship between the user ID and the HSS information is stored in the buffer storage of the network element.

Preferably, the network element is any one of I-CSCF, S-CSCF and AS.

Preferably, if no HSS information corresponding to the user ID is found out in the buffer storage of the network element in the step (III), the buffer storage of the network element is further updated after the step (IV).

Preferably, a table of mapping relationship between the user ID and the HSS information is stored in the buffer storage of the network element, and updating the buffer storage of the network element means adding the mapping relationship between the user ID and the HSS to the buffer storage of the network element.

Preferably, the HSS information comprises address information of the HSS name.

In the method of signalling interchange in another IMS according to the invention, the signalling interchange is made among a network element, SLF and HSS, the network element having a buffer storage, the method comprising sequentially the following steps:

(I) the network element receiving a message containing a user ID;

(III) if the HSS information corresponding to the user ID is found out in the buffer storage, sending a query request to the subscriber's home HSS;

(IV) the home HSS querying its database, sending a correct response to the network element if the result of the query indicates that the user is within its manipulation, and sending an error response to the network element if the result of the query indicates that the user is not within its manipulation;

(V) the network element receiving the response and making a decision, i.e. proceeding to the step (VII) if it is a correct response showing that the HSS information stored in the buffer storage is not expired, or sending the SLF a request containing the user ID for querying the HSS information if it is an error response showing that the HSS information stored in the buffer storage is expired;

(VI) SLF returning the HSS information queried according to the user ID to the network element; and

(VII) the network element building signalling interchange with a new home HSS determined by the HSS information.

Preferably, the network element is any one of I-CSCF, S-CSCF and AS.

Preferably, if the query in the buffer storage of the network element in the step (V) shows that the HSS information corresponding to the user ID is expired, the buffer storage of the network element is further updated after the step (IV).

Preferably, a table of mapping relationship between the user ID and the HSS information is stored in the buffer storage of the network element, and updating the buffer storage of the network element means modifying the mapping relationship between the user ID and the original home HSS stored in the buffer storage of the network element to the mapping relationship between the user ID and the new home HSS.

Preferably, the HSS information comprises address information of the HSS name.

Each message or response thereof includes a timer for timeout protection, and if the timer times out, the method proceeds to an error processing flow and returns an error information to the network element.

As described above, by adding the buffer storage to network element I-CSCF (or S-CSCF or AS), the invention reduces the interchanging process that I-CSCF queries SLF about the subscriber's home HSS. Therefore, the method reduces performance loss due to the number of IMS signalling interchange and improves system stability without changing the existing IMS network infrastructure and influencing the IMS session and service processing mechanism.

The embodiments of the invention will be described below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1 is a schematic diagram showing signalling interchanging processes in IMS according to the prior art; Fig.2 is a schematic diagram showing signalling interchanging processes in IMS according to a first embodiment;

Fig.3 is a schematic diagram showing signalling interchanging processes in IMS according to a second embodiment; and

Fig.4 is a schematic diagram showing signalling interchanging processes in IMS according to a third embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The exemplary embodiments of the invention will be described below. However, it shall be appreciated that, the description of the exemplary embodiments does not limit the scope of the invention. For example, in the following embodiments, I-CSCF processes the REGISTER message according an embodiment of the invention, but any one of I-CSCF, S-CSCF and AS can process other signallings or uses other variations of the invention, all of which can achieve the invention.

Fig.2 is a schematic diagram showing signalling interchanging processes in IMS according to a first embodiment. As shown in Fig.2, the detailed flow is as follows:

I-CSCF receiving a SIP REGISTER registration message;

I-CSCF querying a local buffer storage of I-CSCF according to the user ID information derived from the received registration message SIP REGISTER, and querying information on home HSS corresponding to the user ID;

3)~4) I-CSCF performing a subsequent process CX_QUERY/CX_RESPONSE defined by the 3GPP standard according to the HSS determined by the information on the home HSS, wherein the mapping relationship between user ID (user identity) and HSS name is stored in the local buffer storage of the I-CSCF.

As compared with the prior art shown in Fig.1, the step of querying the SLF is omitted in the first embodiment.

It can be seen that, in the first embodiment, by adding a buffering mechanism in the network element I-CSCF (or S-CSCF or AS), the interchanging processes of I-CSCF querying the SLF about the subscriber's home HSS are reduced. Therefore, this embodiment reduces performance loss due to the number of IMS signalling interchange without changing the existing IMS network infrastructure and influencing the IMS session and service processing mechanism.

It is to be noted that, the buffering technique involved in this embodiment is not associated with user calls and session processes specific to I-CSCF or S-CSCF or AS, does not limit a buffer storage searching mechanism, does not limit the size of the buffer storage, and does not limit a buffer storage medium, for example, the buffer storage medium may be external memory and internal memory, wherein the internal memory is generally preferable in consideration of performance.

Fig.3 is a schematic diagram showing signalling interchanging processes in IMS according to a second embodiment. As shown in Fig.3, a detailed flow is as follows:

I-CSCF receiving a registration message SIP REGISTER;

I-CSCF querying a local buffer storage of I-CSCF according to the "user ID" contained in the received registration message SIP REGISTER, but failing to obtain information on valid subscriber's home HSS;

I-CSCF sending the SLF a query request DX SLF QUERY, in which the "user ID" derived from the registration message SIP REGISTER is contained;

SLF querying its database according to the "user ID" information obtained from the query request DX SLF QUERY to obtain the name of the subscriber's home HSS;

SLF sending a response message DX_SLF_RESP to the I-CSCF, in which the name of the subscriber's home HSS is contained;

6)~7) I-CSCF performing a subsequent process CX_QUERY/CX_RESPONSE on the subscriber's home HSS;

8) updating the buffer storage if CX_RESPONSE is a correct response, i.e. newly adding the mapping relationship between the user ID and the home HSS to the buffer storage.

As compared with the standard flow in the prior art shown in Fig.1, although the second embodiment adds steps 2) and 8), considering these two steps are performed locally in I-CSCF, only slight performance loss is added to the standard flow in the prior art.

Fig.4 is a schematic diagram showing signalling interchanging processes in IMS according to a third embodiment. As shown in Fig.4, a detailed flow is as follows:

I-CSCF receiving a registration message SIP REGISTER;

I-CSCF querying a local buffer storage of I-CSCF according to the "user ID" contained in the received registration message SIP REGISTER, but only the obtained information on the subscriber's original home HSS has been expired;

I-CSCF performing a query CX QUERY according to the information on subscriber's original home HSS (HSS#1);

The original home HSS (HSS#1) querying its database and finding that the user is not under its manipulation (i.e. the HSS database does not contain data information of the user), returning an I-CSCF error response CX_RESPONSE, and setting in the CX_RESPONSE a parameter Result-Code AVP (Attribute-Value Pair) as DIAMETER_ERROR_USER_UNKNOWN, to show that the an object user queried by the CX QUERY is not on the HSS;

I-CSCF deciding whether the CX_RESPONSE is a success response; if it is a success response, it is the same case as in the first embodiment of the invention; if it is a error response, then deciding the value of the parameter Result-Code; if the value is not DIAMETER_ERROR_USER_UNKNOWN, performing a standardized error process; if the value is DIAMETER_ERROR_USER_UNKNOWN, sending the SLF a query request DX-SLF QUERY, in which the "user ID" information derived from the registration message SIP REGISTER is contained.

SLF querying its database according to the "user ID" obtained from the query request DX SLF QUERY to obtain the name of the subscriber's home HSS;

SLF sending a response message DX_SLF_RESP to the I-CSCF, in which the name of the subscriber's new home HSS (HSS#2) is contained;

8)~9) I-CSCF performing a subsequent process CX_QUERY/CX_RESPONSE on the subscriber's new home HSS;

10) if the CX_RESPONSE is a successful response, updating the buffer storage of the I-CSCF, i.e. newly modifying the home HSS of the user ID to the result obtained from the SLF via Dx query, i.e. the result queried via the steps 6) and 7).

As compared with the flow in the prior art shown in Fig.1, the user data is transferred from the original home HSS, thus this embodiment adds steps 2)-4) and 10). However, considering that such data transfer does not take place in the actual operation for a long time, the added performance loss may be omitted.

In the above embodiments, if a timer times out, the process proceeds to an error processing flow in which an error information is returned to an upstream call requesting terminal of I-CSCF (or S-CSCF or AS).

It is to be noted that, one important premise of implementing the invention is that, the home HSS of a certain user generally is not changed during an actual operation. That is to say, the mapping from the "user ID" to "HSS name" is a quasi-static data. This mapping relationship needs to be rebuilt only upon occasional operations of the operator such as upgrading, expansion or maintenance of network result in the transfer of user. Such operating experience can guarantee that the buffering data in the invention are valid data in most cases and thus need not to be updated frequently, that is to say, the occurrence probability of performance loss caused by the third embodiment of the invention is extremely small. Therefore, with a reasonable size of the buffer storage and a good buffering update mechanism, the invention can ensure a good hit (i.e. the first embodiment of the invention), thereby greatly reducing the number of signalling interchange and improving the performance of the whole system.

Various amendments to the embodiments occur to those skilled in the art, without departing from the spirit of the invention and the scope defined by the appending claims. Therefore, the description of the embodiments of the invention with reference to the accompanying drawings is not construed as limiting the invention.

Claims

1. A method of signalling interchange in IMS, wherein the signalling interchange is made among a network element, SLF and HSS, the network element having a buffer storage, the method comprising sequentially the following steps:

(I) the network element receiving a message containing a user ID;

2. The method of signalling interchange according to Claim 1, wherein a table of mapping relationship between the user ID and the HSS information is stored in the buffer storage of the network element.

3. The method of signalling interchange according to Claim 1, wherein the network element is any one of I-CSCF, S-CSCF and AS.

4. The method of signalling interchange according to Claim 1, wherein, if no HSS information corresponding to the user ID is found out in the buffer storage of the network element in the step (III), the buffer storage of the network element is further updated after the step (IV).

5. The method of signalling interchange according to Claim 4, wherein, a table of mapping relationship between the user ID and the HSS information is stored in the buffer storage of the network element, and updating the buffer storage of the network element means adding the mapping relationship between the user ID and the HSS to the buffer storage of the network element.

6. The method of signalling interchange according to Claim 1, wherein the HSS information comprises address information of the HSS name.

7. A method of signalling interchange in IMS, wherein the signalling interchange is made among a network element, SLF and HSS, the network element having a buffer storage, the method comprising sequentially the following steps:

(I) the network element receiving a message containing a user ID;

8. The method of signalling interchange according to Claim 7, wherein a table of mapping relationship between the user ID and the HSS information is stored in the buffer storage of the network element.

9. The method of signalling interchange according to Claim 7, wherein the network element is any one of I-CSCF, S-CSCF and AS.

10. The method of signalling interchange according to Claim 7, wherein, if the query in the buffer storage of the network element in the step (V) shows that the HSS information corresponding to the user ID is expired, the buffer storage of the network element is further updated after the step (IV).

11. The method of signalling interchange according to Claim 10, wherein, a table of mapping relationship between the user ID and the HSS information is stored in the buffer storage of the network element, and updating the buffer storage of the network element means modifying the mapping relationship between the user ID and the original home HSS stored in the buffer storage of the network element to the mapping relationship between the user ID and the new home HSS.

12. The method of signalling interchange according to Claim 7, wherein the HSS information comprises address information of the HSS name.

13. The method of signalling interchange according to Claim 1 or 7, wherein, each message or response thereof includes a timer for timeout protection, and if the timer times out, the method proceeds to an error processing flow and returns an error information to the network element.