WO2000069208A1

WO2000069208A1 - Method and apparatus for voice call re-entry through external access

Info

Publication number: WO2000069208A1
Application number: PCT/SE2000/000774
Authority: WO
Inventors: Peter Ramle
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 1999-05-06
Filing date: 2000-04-20
Publication date: 2000-11-16
Also published as: AU4788500A

Abstract

A method and apparatus is provided allowing a mobile subscriber (30) disconnected from a group call to re-enter the group call. Typically a mobile subscriber (30) is disconnected from the group call due to lack of radio coverage. The method and apparatus works particularly in a telecommunications network which doesn't supply a subscriber's A-number. The mobile subscriber (30) re-enters the group call by supplying to the network an A-number (55) along with a re-entry character (56).

Description

METHOD AND APPARATUS FOR VOICE CALL RE-ENTRY THROUGH EXTERNAL ACCESS

FIELD OF THE INVENTION

The present invention relates generally to a mobile telecommunications networ and, more particularly, to a service provided to the telecommunications network for re-entering a group call .

BACKGROUND OF THE INVENTION The method and apparatus of the invention is designed particularly for use in a public land mobile network (PLMN) .

One important service typically provided by a group server connected to a PLMN is that of group calling. A group call is a conference call, in which all participants can in turn talk and listen to each other. In group calls the whole group is typically identified by one identity code.

In an ongoing group call involving one or more mobile subscribers, there is a problem in that one of the mobile subscribers may suddenly drop out of the call due to, for example, a lack of radio coverage. This single party will be disconnected, but the call will continue among the remaining parties of the group. The disconnected party will attempt to re-enter the group call in an external access procedure. In this procedure, the disconnected party will be asked to give a password to authenticate himself or herself. However, there is a problem in that the server may have no way to correlate the disconnected party with the ongoing call so that the disconnected party can thereby rejoin the call. For example, the network may not always provide the mobile subscriber' s identity number (A-number) . There may be no way to identify the disconnected party as having been a member of the group call without the subscriber's A-number. It would be desirable to provide a technique allowing the dropped party to rejoin the group call in an efficient and cost effective manner, particularly for networks which do not provide a subscriber's A-number.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method and apparatus is provided for re-entering a group call in a telecommunications network. A group call has a plurality of subscribers participating in the ongoing group call. One of the subscribers is a mobile subscriber who has been disconnected from the group call due typically to lack of radio coverage.

In one aspect of the present invention, a first signal is transmitted by the mobile subscriber containing a group identifier. The group call is located using the group identifier. The mobile subscriber is prompted for a password. A second signal is then transmitted by the mobile subscriber. The second signal comprises a subscriber identification number along with a re-entry character indicating a request to re-entry the group call. The subscriber's identification number may be an A-number, extracted from_, the A-number, or otherwise based on the A-number. The mobile subscriber identified by the subscriber identification number is reconnected to the group call identified by the group identifier so that the mobile subscriber may then rejoin the group call.

The participating subscribers of the group call may be one or more mobile subscribers, or also one or more non-mobile subscribers from a public switched telephone network connected to the mobile network.

Typically, the second signal is keyed in manually by the mobile subscriber on a mobile station using dual tone multi-frequency dialing. However, in another embodiment the second signal may also be transmitted by the mobile subscriber pushing a button provided on a mobile station which automatically transmits the mobile subscriber's identity number.

In a further embodiment of the invention, in order to assure additional security, the mobile subscriber may be prompted for a password and the mobile subscriber reconnected to the group call only if the password in verified.

BRIEF DESCRIPTION OF THE DRAWINGS In order to facilitate a fuller understanding of the present invention, reference is now made to the appended drawings. These drawings should not be construed as limiting the present invention, but are intended to be exemplary only.

Figure 1 is a block diagram illustrating the network connection of multiple Public Land Mobile Networks (PLMN) to a Public Switched Telephone Network (PSTN) . Figure 2 is a block diagram illustrating a mobile station being reconnecting to a group call by a group controller.

Figure 3 is a flow diagram depicting the procedure for re-entering a group call.

Figure 4 depicts an example format of a subscriber's identification number.

Figure 5 depicts an embodiment of a database used by the group controller to identify group calls and participants of the group calls.

Figure 6 depicts a mobile station.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to Figure 1, there is shown a block diagram illustrating a telecommunications network 1 having multiple Public Land Mobile Networks (PLMN) 10 interconnected to a Public Switched Telephone Network (PSTN) 20. A mobile station 30 is associated with one of the PLMNs 10 as the home PLMN 10a. Within each PLMN 10, there are a number of different mobile switching centers (MSC) 40 servicing the geographical area covered by the network. A home location register (HLR, not shown) and a visitor's location register (VLR, not shown) is associated with each MSC. The servicing MSC 40a establishes a call connection over radio link 50 with the mobile station (MS) 30 located within the MSC serving area. Within each PLMN 10, there exists a Gateway Mobile Switching Center (GMSC) 80 for routing incoming calls intended for mobile stati-on 30 to the appropriate MSC 40. The PLMNs 10 establish call connections with the PSTN 20 via the GMSCs 80. Figure 1 additionally shows a group controller 45 coupled to one of the MSCs 40. A group controller 45 is typically associated with a particular MSC 40. The group controller 45 may be an independent server, or alternately, a group of distributed servers, or a computer system. The group controller 45 is responsible for establishing and monitoring group calls for the network 1.

In Figure 2, a more detailed diagram of the group controller 45 is shown comprising a set-up unit 60, a re-entry unit 62, and a group call database 64. The group controller 45 sets up and manages groups calls. While monitoring a group call, group controller 45 may transmit group call data or call information messages to the subscriber stations involved in the group call. Set-up unit 60 establishes the initial connections for the group call by connecting one or more subscribers forming a group of participants for the group call. A set-up of a group call may be established by any of a variety of techniques known in the telecommunications arts. For example, a group call may be initiated by a calling mobile radio subscriber or by a calling telephone subscriber dialing of a subscriber call number authorized by the group controller 45.

The group call database 64 stores information on the group calls currently in progress and includes a call number identifying the group call 200, and for each ongoing group call a dynamic list of subscribers 201a-201d participating in the group call (See Figure 5) . Referring to Figure 3, a method is shown according to the present invention for re-entering a group call in a telecommunications network. The group call has a plurality of subscribers engaged in the group call. At least one of the subscribers is a mobile subscriber who was disconnected from the group call, typically, due to lack of coverage in the mobile subscriber's area.

In step 80, the mobile subscriber, wishing to re- enter the network 1, transmits a first signal containing a group identifier identifying the group call. The MSC centers of the network forward the mobile subscriber's call to the group server 45 associated with MSC 40. In step 82, group server 45 prompts the mobile subscriber for a password. However, the group server 45 provides the mobile subscriber with the opportunity to enter a second signal 54 giving a mobile subscriber' s identification number 55, preferably the subscriber's A-number (the number of the calling subscriber) , instead of the password and terminating with a re-entry character 56 indicating a request to re-entry the group call (See Figure 2) . Any of a variety of formats may be used for the mobile subscriber's identification number 55. In Figure 4 is shown one example of one such format, the Mobile Station ISDN Number (MSISDN) 90 comprising a country code (CC) 91, a National Destination Code (NDC) 92, and a Subscriber Number (SN) 93. The MSISDN is a number which uniquely identifies a mobile telephone subscription in a telephone network numbering plan. Other numbering plans may be used, such as the International Mobile Subscriber Identity (IMSI), the Mobile Station Roaming Number (MSRN) , or the International Mobile Station Equipment Identity (IMEI) . In step 84, the mobile subscriber using mobile station 30 provides the group server 45 with the subscriber's A-number 55 terminated by the special re^¬ entry character 56. This number may be keyed in manually on the mobile station 30 by means of dual tone multi-frequency (DTMF) dialing keypad 31 (See Figure 6) . In an alternate embodiment, the number could be keyed in from a different station, such as a home station (telephone) , for example, in the case where the mobile station 30 is broken or otherwise unavailable. In another alternate embodiment, the mobile station 30 is provided with a button 32 and associated circuitry to enable the mobile subscriber to automatically transfers the pre-stored A-number by pressing the button 32 rather than by entering the numbers manually (See Figure 6) .

In step 86, the group server 45 looks up the A- number in database 64. Database 64 shown in Figure 5 contains sufficient information so that the group controller 45 can identify a group call and participants. In one embodiment of the database 64, there is a list for each group call. Figure 5 shows Group 1 through Group N, where N is the number of calls. The list for group 1 contains an identifier 200 for the group call and a list of two or more A-numbers of the participants (e.g., 201a, 201b, 201c are shown) for the ongoing group call. Similarly, Group 2 is shown having an identifier 202 for the group call and multiple A-numbers (e.g., 202a, 202b, and 202c are shown) . Group N is depicted having an identifier 203 for the group call and multiple A-numbers (e.g., 203a, 203b, and 203c) . The server associates the A-number provided by the disconnected subscriber with one of the A-numbers of one of the groups. If the subscriber is in the list, the group controller 45 permits re-entry of the subscriber into the group call. In an alternate embodiment, as an extra security measure, the group controller 45 at step 84 can require additionally that the subscriber supply a password. The group controller 45 will then permit re-entry of the subscriber only upon validation of the password. Thus, the above-described invention provides a technique allowing a dropped party of a group call to rejoin the group call in an efficient and cost effective manner for networks which do not provide a subscriber's A-number. The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the present invention, in addition to those described herein, will be apparent to those of skill in the art from the foregoing description and accompanying drawings. Thus, such modifications are intended to fall within the scope of the appended claims .

Claims

CLAIMSWhat is claimed is:

1. A method for re-entering a group call in a telecommunications network, the group call having a plurality of subscribers participating in the group call, at least one of the subscribers being a mobile subscriber disconnected from the group call, the method comprising the steps of: transmitting a first signal by the mobile subscriber containing a group identifier; locating the group call using the group identifier; transmitting a second signal by the mobile subscriber comprising a mobile subscriber' s identification number along with a re-entry character indicating a request to re-entry the group call; and reconnecting the mobile subscriber identified by the mobile subscriber's identification number to the group call identified by the group identifier so that the mobile subscriber rejoins the group call.

2. The method of claim 1, wherein: the mobile subscriber's identification number is formed from the subscriber's A-number.

3. The method of claim 1, wherein: the participating subscribers are one or more mobile subscribers.

4. The method of claim 1, wherein: the participating subscribers are one or more non- mobile subscribers.

5. The method of claim 1, wherein: the second signal is keyed in manually by the mobile subscriber on a mobile station using dual tone multi-frequency dialing.

6. The method of claim 1, wherein: the second signal is transmitted by the mobile subscriber pushing a button on a mobile station which automatically transmits the mobile subscriber's identity number.

7. The method of claim 1, further comprising the steps of: prompting the mobile subscriber for a password; and reconnecting the mobile subscriber to the group call only if the password in verified.

8. An apparatus within a telecommunications system for controlling a group call having a plurality of participants, one of the participants of the group call being a mobile subscriber disconnected from the group call due to lack of radio coverage, the apparatus comprising: a set-up unit for setting up the group call by establishing connections among the participants; and a re-entry unit for reconnecting the disconnected mobile subscriber to the group call, wherein the re- entry unit accepts a signal generated by the mobile subscriber comprising a mobile subscriber's identification number along with a re-entry character indicating a request to re-entry the group call.

9. The apparatus of claim 8, wherein: the mobile subscriber's identification number is the A-number of the mobile subscriber.

10. The apparatus of claim 8, wherein: the re-entry unit reconnects the mobile subscriber identified by the mobile subscriber's identification number to the group call identified by a group identifier so that the mobile subscriber rejoins the group call.

11. The apparatus of claim 8, further comprising: a database including a list of group calls indexed by their group identifies wherein the re-entry unit identifies the group call from the list of group calls by matching the group identifier to the group identifies of the list.

12. The apparatus of claim 8, wherein: the signal is transmitted by a dual tone multi- frequency mobile station.

13. A telecommunications system for establishing a re-entry call connection between a mobile subscriber and an ongoing group call, comprising: a plurality of subscribers in the telecommunications system; one or more mobile switching centers connected together forming a network for servicing the plurality of subscribers; and a group call controller coupled to the network for establishing a connection among one or more participants selected from the plurality of subscribers to form a group call, the group controller comprising: a set-up unit for setting up the group call by establishing connections in the network among the participants; and a re-entry unit for reconnecting the mobile subscriber to the group call, wherein the re-entry unit accepts a signal generated by the mobile subscriber comprising the mobile subscriber's identification number along with a re-entry character indicating a request to re-entry the group call.

14. The telecommunications system of claim 13, wherein: the mobile subscriber's identification number is the A-number of the mobile subscriber.