AU745289B2

AU745289B2 - Service termination in a mobile telephone network

Info

Publication number: AU745289B2
Application number: AU23836/99A
Authority: AU
Inventors: Jean Charpentier; Edouard Issenmann
Original assignee: Alcatel CIT SA; Alcatel SA
Current assignee: Alcatel Lucent SAS
Priority date: 1998-05-14
Filing date: 1999-04-16
Publication date: 2002-03-21
Anticipated expiration: 2019-04-16
Also published as: JP2000059863A; AU2383699A; EP0957652A1; DE69900450T2; CN1236275A; FR2778813B1; DE69900450D1; EP0957652B1; FR2778813A1

Description

P/00/01i1 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Service termination in a mobile telephone network The following statement is a full description of this invention, including the best method of performing it known to us: F14P.SYr)cPANA TP")1201wqIwV)1.4 CE\99104X)2.2 1 Service termination in a mobile telephone network Field of the invention The present invention relates to a method of terminating service in a mobile telephone network.

Background of the invention The invention relates to digital mobile telecommunications networks. It applies particularly to the GSM network. One of the problems that arises in such mobile networks is that of terminating the activities of a subscriber.

Call termination systems have been proposed in the context of the GSM. The Immediate Service Termination (IST service is used, for a given subscriber, to discontinue calls in progress, in the Public Land Mobile Network (PLMN), e.g. when S. a subscription is cancelled or when the operator has good reason to think that there is a potential fraud. Terminating the subscription can concern various types of call that a "•subscriber can generate, and that are explained below with reference to Figure 1.

Figure 1 shows two PLMNs, namely the original public land mobile network 1 of the 0% subscriber or "Home Public Land Mobile Network (HPLMN), and a network 2 in *:.which the subscriber can be a visitor or "Visited Public Land Mobile Network

(VPLMN).

A call can exist in a Visited Mobile-services Switching Center (VMSC) 3 in which the subscriber 4 is located. Typically, the call is a call in progress; in the example shown in Figure 1, the VMSC 5 is shown both in the HPLMN and also in the VPLMN insofar as it can be in either of these networks.

A call can also exist in a VMSC 5 other than the VMSC in which the subscriber is located at a given time, the subscriber having been previously located in the other VMSC. For example, this can apply for a call-forwarding service, for a call 6 forwarded in the VMSC 5 and that is not finished when the subscriber leaves the VMSC 5; again, in the example shown in Figure 1, the VMSC 3 is shown both in the HPLMN and also in the VPLMN insofar as it can be in either of these networks.

CE\99104(X)2.2 It is also possible for a call to exist in a Gateway Mobile-services Switching Center (GMSC) 7 of the home network. This typically applies for a call forwarded in the GMSC for an unconditionally forwarded call 8.

A call can also exist at a given time in a GMSC 13 in some other network 2. This can apply if the "optimal routing" function of the GSM is activated. This function makes it possible, when a subscriber of the HPLMN is called by a mobile station located in a VPLMN, to set up call forwarding to a subscriber in the country of the VPLMN without the call being routed via the country of the HPLMN of the called subscriber.

Figure 1 shows a call to a subscriber of the HPLMN when the calling subscriber 4 is located in a VMSC 11 of the network 2. Arrow 12 shows the call being forwarded to a fixed telephone set of the VPLMN, via a GMSC 13.

Under all circumstances, it can be useful to terminate all of these calls for the purpose of service termination.

To provide such a termination service, the following solutions have been proposed: an 15 intelligent network service exists called "CAMEL" (Customized Application for Mobile network Enhanced Logic) for certain subscribers. For a CAMEL subscriber, the home PLMN of the subscriber or "HPLMN" can control all of the activities of the ••go subscriber throughout the world; it can therefore terminate them, in the MSCs in which a call in progress can exist, in the HPLMN, and in the VPLMNs. This option is offered to the HPLMN for the GMSCs and in the VMSCs.

That solution suffers from the following drawbacks: it does not operate for subscribers who are not CAMEL subscribers at the time of the decision to terminate the service.

It is difficult to envisage putting all of the subscribers on CAMEL as a precautionary measure, merely to make service termination possible: the CAMEL service consumes a large amount of resources, switches and interrogation node platforms, and it is not possible to know at a given time which subscriber is to be subjected to a decision to terminate service.

It is also known that service termination can be applied in the VMSC in which the subscriber is located when the decision to terminate is taken. That is possible merely by means of an Operator Determined Barring (ODB) command issued by the PLMN CE\99104(X)2.2 3 in the VMSC in which the subscriber is located. At any time, the Home Location Register (HLR) of the home network knows which VMSC is the VMSC in which the subscriber is located.

That solution is insufficient insofar as it does not make it possible to terminate all of the calls in progress. As shown in Figure 1, an ODB command makes it possible to terminate a call of a subscriber 4 in the VMSC 3 in which the subscriber is located; it does not make it possible to terminate the calls in a VMSC 5 in which the subscriber was located previously. That can apply for a call forwarding service, for a call forwarded in the VMSC 5, and that is not finished when the subscriber leaves the 10 VMSC 5; or for calls in the GMSCs of the home network, or else for calls in a GMSC of a VPLMN when the optimal routing function is activated.

It has also been proposed to stop all activity in a VMSC other than the VMSC in

S

which the subscriber is located, after a duration T o starting from the time at which the subscriber data has been erased from the Visitor Location Register (VLR) of the SS 15 VMSC. In other words, all the activities, such as conditional forwarding, redirected or

S*

o transferred call, etc., are terminated a given duration after the subscriber leaves the

VMSC.

That solution is not satisfactory either. A duration T o that is too short might disturb the service offered to the subscribers for whom service termination is not Otte 20 implemented. A duration that is too long leads to high charges which, in the case of service termination, are borne by the operator. From that point of view, GSM operators have proposed that the duration T o be calibrated by the HPLMN, thereby making it possible to adapt the duration T o as a function of subscribers, but further complicating implementation of IST, by requiring additional messages.

The invention therefore proposes a practical solution to the problems of service termination. It offers service termination that is effective but that does not penalise legitimate subscribers. It provides a solution that consumes a smaller amount of resources than CAMEL.

CE\99104002,2 4 Summary of the invention The invention provides a method of terminating service in a mobile telephone network, the method comprising a step in which, in the presence of a call under abnormal conditions, a switching center of the network sends an alarm message to the home network of the subscriber to be charged for said call.

In an implementation, the method comprises a step in which the home network of the subscriber sends a service termination message if the subscriber is the subject of a service termination request.

Provision may be made for the home network of the subscriber to send a response 0o S, 10 message in response to the alarm message, regardless of whether or not the subscriber is the subject of a service termination request.

S.

S Advantageously, an alarm message is sent for any call longer than a predetermined io duration.

0 In an implementation, the sending of an alarm message is repeated, preferably 15 periodically, if the call continues.

In another implementation, the switching center in which a subscriber is located does 000* not send any alarm message.

Brief description of the drawings Other characteristics and advantages of the invention will appear on reading the following description of implementations of the invention, given by way of example and with reference to the accompanying drawing, in which: Figure 1 shows various calls in a mobile telephone network; and Figure 2 diagrammatically shows service termination of the invention.

Detailed description of the embodiments In the description below, the example of GSM is considered, it being understood that the present invention is not limited to this type of mobile telephone network, but rather it is equally applicable to other types of telecommunications network.

CE\99104002.2 In order to manage service terminations, the invention proposes to transmit an "alarm" to the home network of the subscriber under certain conditions so as to enable calls to be terminated if necessary.

This solution avoids penalising legitimate users (the number of whom normally exceeds the number of those to whom IST is applied) by the mechanisms implemented to perform IST. It further guarantees that IST is effective without consuming large amounts of resources. The invention is applicable to all of the activities of the subscriber, throughout the GSM world, without it being necessary for the service termination to be generally broadcast, nor for all subscribers to be tracked.

It is compatible with optimal routing.

S: The invention may be implemented in the VMSC in which the subscriber is located.

However, this is not essential insofar as the ODB command constitutes a solution making it possible to terminate calls in this VMSC.

In the other switching centers, regardless of whether they are VMSCs and GMSCs of the home network, or VMSCs or GMSCs of a visited network, the invention proposes, when the conditions of a call appear to be abnormal, to send an alarm message to the •home network of the subscriber to be charged. On receiving the alarm message, the home network can then respond by requesting call termination, if the subscriber is the subject of a service termination request.

To trigger sending of an alarm message, i.e. for determining under which conditions a call appears to be abnormal, it is possible to use as a criterion the duration of the call after the subscriber has left the corresponding VMSC, or the duration of the forwarded call.

Figure 2 shows, for the GMSC 7, the alarm message sent to the HLR 14 of the HPLMN 1. For example, the message is sent when the forwarded call 8 has a duration T o much longer than the normal duration; a choice of fifteen minutes or half an hour is appropriate. The home network may respond to the alarm message by requesting termination of the call, e.g. if, in the meantime, the subscriber has become the subject of a service termination request. This is represented by arrow 16. The GMSC may then terminate the call 8. If the subscriber is not the subject of a service CE\99104(X)2.2 termination request, it is possible for the home network not to respond; this solution offers the advantage of reducing the amount of traffic. It is also possible to make provision for the home network to respond in any event, or to respond only if the call can be continued.

The same solution may be implemented for the GMSC 9 of a visited network; this is not shown in Figure 2. The solution is independent of implementation of optimal routing, and it also applies if such routing is in place. Like the GMSC 7, a GMSC of the visited network 2 sends an alarm message to the home network as soon as the call exceeds a predetermined duration.

10 It can be understood that, if the subscriber is not the subject of an IST request, the call 8 or 12 is continued, and the quality of service is thus maintained.

For the VMSC 3 in which the subscriber is located, an ODB command (known per se) makes it possible to terminate the calls of the subscriber.

In the VMSC 5 in which the subscriber was previously located, the invention also proposes to send an alarm message 20 to the home network; for example, this alarm message may be sent after a duration T 1 which may be equal to the duration T o has elapsed from the time at which the subscriber data was erased from the VLR of the VMSC 5. As in the case of the GMSC 7, this message may optionally cause a response 21, if the subscriber is not the subject of an IST request. As in the case of the GMSC 7, the service is maintained if the subscriber is not the subject of an IST request, and the existence of the IST service is transparent for the subscriber.

The choice of the durations T o and T 1 depends on the constraints on the IST service, and on the extra traffic load generated by the alarm messages that is acceptable. As mentioned above, a duration of fifteen minutes or half an hour is an acceptable compromise between the sums that cannot be charged and the traffic generated by the alarm messages. Such a duration is considerably longer than the mean call duration.

The invention further makes it possible for the home network to monitor calls of duration greater than T o or T 1 The network can thus monitor the calls that exceed a mean duration; in addition to being used for statistics purposes, such monitoring can i- CE\99104(X)2.2 7 make it possible to detect fraudulent use, e.g. by comparison with the mean duration of the calls made a subscriber.

In a particularly advantageous implementation, the sending of the alarm message is repeated periodically, if the call continues. This makes it possible, not only to monitor long calls, but also to continue monitoring them if they continue. The period T 2 at which the alarm message is repeated may be different from the durations TO and T 1 or else it may equal thereto. It should be noted that the period T 2 may easily be less than the duration T o or T 1 insofar as the extra traffic load generated decreases over time, the number of calls generally decreasing with increasing duration.

10 Naturally, the present invention is not limited to the implementations described and shown, but rather numerous variants of it are accessible to the person skilled in the art.

a* It is thus possible to use durations To, T 1 or T 2 different from those given by way of example, depending on requirements.

Once again, the invention is described with reference to GSM but it also applies to 15 other mobile telephony networks, e.g. to the UMTS network and to other networks.

*oo

Claims

1. A method of terminating service in a mobile telephone network, the method comprising a step in which, in the presence of a call under abnormal conditions, a switching center of the network sends an alarm message to the home network of the subscriber to be charged for said call.

2. A method according to claim 1, comprising a step in which the home network of the subscriber sends a service termination message if the subscriber is the subject of a service termination request.

3. A method according to claim 1 or 2, comprising a step in which the home network 10 of the subscriber sends a response message in response to the alarm message, regardless of whether or not the subscriber is the subject of a service termination request.

4. A method according to claim 1, 2, or 3, wherein an alarm message is sent for any call longer than a predetermined duration. 15

5. A method according to any one of claims 1 to 4, wherein the sending of an alarm message is repeated, preferably periodically, if the call continues.

6. A method according to any one of claims 1 to 5, wherein the switching center in which a subscriber is located does not send any alarm message.

7. A method substantially as hereinbefore described with reference to the accompanying drawings. Dated this 16th day of April 1999 Alcatel by its attorneys Freehills Patent Attorneys i, .I -i i:1c-i