Abstract:
A method is provided to enable a participant of a communication event established using a first communication service to initiate a communication with at least one other participant of the communication event using a second communication service. The method includes receiving, from the participant of the communication event, a communication, the communication being received via the second communication service, determining at least one other current participant of the communication event, and initiating at least one other communication with at least the other current participant.

Description:
RELATED APPLICATIONS 
   This application for letters patent is related to and claims the benefit of an earlier filing date and right of priority of foreign filed patent application EP05300239.0, filed in the European Patent Office on Mar. 31, 2005, titled “Improvements in or Relating to Communications”, which is also hereby incorporated by reference. 
   BACKGROUND 
   As communication devices, such as mobile telephones, and communication networks become increasing sophisticated there are an increasing number of communication services being offered to consumers. Such communication services include short message system (SMS) messaging, multimedia messaging (MMS), instant messaging (IM), push-to-talk (PTT), and the like. 
   In order for a communication device, such as a mobile telephone, to be able to provide access to such communication services a mobile telephone typically needs to have a corresponding client application installed thereon. The client application provides a user interface to the service as well as a suitable interface for communicating with a network based server application providing the service. 
   Once a mobile telephone has been designed and manufactured, it is expensive for the network operators and the handset manufacturers to modify the software applications present thereon to accommodate improved services or improved functionality. Thus, from an economic point of view at least, it is somewhat undesirable to provide upgrades to existing mobile telephones, unless it is deemed that the improvements represent a significant revenue source or provide substantial benefits for the network operator or the handset manufacturer. 
   The communication services available to mobile telephone users may be divided broadly into two categories: session-based and session-less services. For example, SMS and MMS are considered as session-less communication services. In other words, a user may send an SMS message to one or more other users, or may receive an SMS from one or more other users. However, each message sent or received is treated independently, and there is no concept of a ‘session’ between separate SMS messages, for example. Other communication services, however, such as push-to-talk, are session-based. For example, a push-to-talk session exists between multiple users when a push-to-talk communication is established until the push-to-talk communication is terminated. 
   Generally, as communication services become more sophisticated users demand higher levels of functionality and interoperability between different communication services. For instance, it may be desirable that users of session-based communication services be able to ‘share’ details of the session with another session-based or session-less communication service. For example, a user in a push-to-talk session may wish to, whilst participating in the push-to-talk session, send an SMS message to each of the current participants to the session. However, there is currently no easy way to achieve this. The only current known way is for the user to manually determine the current participants of the PTT session using the PTT client application, and to manually address an SMS message to each of the determined participants using an SMS client application. This is particularly inconvenient to the user, especially where the number of users in a session is large, and where the users in a session may join and leave the session at different times, making it difficult for a user to precisely determine exactly who is participating in a session at any given time. 
   One of the reasons for this is that different client applications on the same mobile telephone are typically independent from one another and generally lack any means of communication between them. Thus typically an SMS client application has no way of communicating with the push-to-talk client application for determining the current users of the session. 
   One way of overcoming this problem would be to redesign the client applications to provide the necessary interoperability. However, as previously mentioned, upgrading existing handsets is somewhat undesirable. Even if such a redesign were to take place, such improved client applications would typically only be available on new mobile telephones, leaving the vast majority of legacy mobile telephones unable to take advantage of such improvements. 
   Consequently, there is a need to provide a way of enabling users of mobile telephones to ‘share’ sessions between different communication services, without requiring modification to existing client applications. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrams, in which: 
       FIG. 1  is a block diagram showing a communication system according to the prior art; 
       FIG. 2  is a block diagram showing a communication system according to an exemplary embodiment of the present invention; and 
       FIG. 3  is a block diagram showing a communication system according to another exemplary embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   Referring now to  FIG. 1 , there is shown a block diagram of a system according to the prior art.  FIG. 1  shows a mobile telephone  102   a  that comprises a number of client applications (not shown) enabling the user of the mobile telephone  102   a  to access a number of different communication services, such as push-to-talk services, SMS services, MMS services, and the like. Through a separate client application (not shown) the mobile telephone  102   a  is also able to provide conventional mobile telephony services, through a mobile telephony network  108  as is well understood in the art. 
   For example, in order for the user of the mobile telephone  102   a  to establish a push-to-talk communication session the user selects, through the user interface provided by the PTT client application, one or more participants to invite to the session from a list of available contacts or buddies. To initiate the session the user actuates an appropriate button on the mobile telephone  102   a  to initiate the call. This causes an appropriate message, such as a PTT Call Setup type message to be sent to the PTT server  104 . The PTT call setup message contains appropriate addressing or contact details of the invited participants. The PTT sever  104  then establishes, or attempts to establish, a PTT session with the invited participants and the inviter, as is well known in the art. 
   As mentioned above, one of the problems with current mobile telephones is that the client applications which provide access to the different communication services available are typically independent from one another. 
   Thus, if a user of the mobile telephone  102   a  is involved in a PTT session with the users of mobile telephones  102   b  and  102   c , there is currently no way for the user to invoke a different communication service with the participants of the PTT session in a simple manner, as is explained in more detail below. For example, if a participant of a PTT session wishes to send an MMS message to the current participants of the PTT session this is problematic for a number of reasons. 
   For example, to send an MMS message to each of the current participants of a PTT session the user has to invoke the MMS message client application on his mobile telephone, to create the message to send and to address the message to each of the current participants of the PTT session. Thus, for each participant of the PTT session the user has to manually retrieve, for example from an electronic address book, the telephone subscriber number of each of the participants in the PTT session, and to add each telephone subscriber number to the distribution list of the MMS message. 
   Such a procedure is particularly inconvenient for the user, especially in the case where there are a large number of participants in the PTT session and where participants join and leave the session during the life of the session. 
   Thus, since the PTT and MMS client applications are typically substantially independent, there is no easy way for the user to perform the above-described operation in a simple and convenient manner. 
   From a user perspective, the situation is, therefore, currently somewhat frustrating. 
   Referring now to  FIG. 2  there is shown a block diagram of a system  200  according to an embodiment of the present invention. 
   The user of the mobile telephone  102   a  creates a PTT session with mobile telephones  102   b  and  102   c , for example as described above With reference to  FIG. 1 . The mobile telephone  102   a  may be configured such that PTT messages, such as a PTT call setup request, sent from the mobile telephone  102   a  are sent to a PTT proxy server  204 . 
   The PTT proxy server  204  receives the PTT call setup request and adds an additional ‘dummy’ or pseudo participant to the request. The dummy participant preferably has a substantially unique displayed name (e.g. “This Session”) such that the ‘dummy’ participant is easily recognizable for a user of a communication device. The ‘dummy’ participant also preferably has a globally unique identity, such as globally unique SIP address. The PTT proxy  204  forwards the PTT call setup request, including details of the additional dummy participant, to the PTT server  206 . The PTT server  206  then attempts to establish a PTT session with the invited participants and the dummy participant, in the normal manner. 
   The created dummy participant is controlled and managed by a PTT session manager  210 , and the SIP address of the dummy participant is assigned to the PTT session manager  210 . The PTT session manager  210  includes a PTT client application suitable for enabling the dummy participant to be invited to and connected as a participant of a PTT session. However, any PTT voice messages sent to the PTT client application in the PTT session manager  210  may not be processed. Since the dummy participant behaves essentially like any other session participant, the PTT session manager  210  thus has access to the details of the current participants in the same way as any other participant to the call. 
   Once the PTT session is established, the dummy participant is visible, along with each of the other participants of the session, on the buddy list viewable on the mobile telephone of each participant, as shown, for example, at  103   a ,  103   b  and  103   c.    
   From the user point of view far the dummy participant behaves exactly like any other participant to the session. The dummy participant can be used to represent the current PTT session, and may be arranged to appear on the buddy list using the assigned text identifier, such as “This Session”, or something appropriate. 
   If one of the participants  102   a ,  102   b  or  102   c  wishes to send, for example, an MMS message to all of the other participants, the user opens his MMS client application, and copies the address details of the buddy “This Session” from his PTT interface and ‘pastes’ them to the interface of the MMS application. However, since the MMS client application requires a telephone subscriber number for addressing an MMS message the copy and paste operation must ensure that a valid telephone subscriber number is provided to the MMS application. 
   Depending on the particular user-interface provided, this may be achieved in a number of ways. 
   For example, where a simple user-interface is provided by the mobile telephone the text “This Session” used to identify the dummy participant could additionally include the SIP URI of the dummy participant which is arranged in the form of a telephone subscriber number. For example, the full text of the dummy participant could be: 
   “This Session +33123456@hp.com” 
   In this case, the user just has to select the telephone subscriber number portion of the buddy identifier, and to paste this into the MMS application. 
   A more sophisticated user-interface may enable a user to automatically copy just the telephone subscriber number part of a buddy identifier or SIP address. Those skilled in the art will appreciate that other techniques could also be used. The user then sends a single MMS message to the telephone subscriber number +33123456 in the normal manner. 
   The telephone subscriber number +33123456 corresponds to the PTT session manager  210  which has a suitable MMS interface to enable it to receive and transmit MMS messages. The PTT session manager  210  thus receives the MMS message and extracts therefrom the telephone subscriber number of the originator of the message. The PTT session manager  210  performs a suitable address translation of the extracted telephone subscriber number to retrieve the corresponding SIP URI of the originator of the message. Such an address translation service could be provided in a variety of different ways, such as using a suitable DNS-type server, as will be appreciated by those skilled in the art. 
   Using the obtained SIP URI of the originator of the MMS message the PTT session manager is able to determine which of the ‘dummy’ participants the PTT session manager is managing is currently participating in a session with the originator of the MMS message. In other embodiments, the PTT session manager  210  may use a separate telephone subscriber number for each session managed thereby, thereby removing the need for the PTT session manager to store and maintain internal tables mapping message originators to sessions. 
   Once this is established, and as mentioned previously, the PTT server is able to determine the list of current participants to that session since this information is directly available to the PTT session manager. For example, in SIP-based system, each SIP message may contain the SIP URIs of each participant of the session. 
   Once the details of all the participants are obtained, the PTT session manager performs a suitable address resolution of the obtained SIP URIs, as described above, to obtain the corresponding telephone subscriber numbers of each of the current participants. The PTT session manager  210  then sends the original MMS message through the MMS system  208  to the obtained telephone subscriber numbers in the normal manner. 
   In this way, a participant of a PTT session may initiate a new communication service with the current participants of the PTT session in a simple and effective manner, thereby allowing, for example, a PTT session to be ‘shared’ with a different communication service. 
   A further exemplary embodiment will now be described with reference to  FIG. 3 . 
   The user of mobile telephone  202   a  creates a PTT session with mobile telephones  202   b  and  202   c  by sending an invite message to the PTT server  306 . This message is forwarded, via a PTT proxy  304 , to the PTT server  306  which establishes the PTT session with mobile telephones  202   b  and  202   c  in the normal manner. For each PTT session created the PTT server  306  allocates a substantially unique session identifier. 
   PTT proxy  304  obtains, from the information contained in each SIP message handled by the proxy  304 , the session ID of the session created by mobile telephone  202   a  and the SIP URIs of the other participants of the session. With this information the PTT proxy  304  creates tables  310  and  312 . 
   Table  310  contains details of addressing information, such as a SIP URI, relating to each mobile telephone currently involved in a PTT session along with the corresponding session ID of the session. Table  312  contains details of, for each PTT session ID, addressing information, such as a SIP URI, for each of the participants to the session. 
   Tables  310  and  312  are kept up-to-date as the PTT server  306  is arranged to notify the PTT proxy, for example through use of a suitable subscribe mechanism, of any additions or removals from each session. 
   Each of the mobile telephones  202   a ,  202   b  and  202   c  are configured to contain, store or otherwise make available, an entry in the electronic address book called, for example “Current Session”. The entry “Current Session” has a predetermined telephone subscriber number, for example +33123456, which is used to address a suitable MMS client application on the PTT proxy  304 . Each mobile telephone may be configured in this way either manually by the user of the mobile telephone, or alternatively may be configured by the manufacturer or network provider, for example through a group and list management server (GLMS). The telephone subscriber number allocated for the entry “Current Session” can be the same for all subscribers, although it is equally possible that different telephone subscriber numbers be allocated for different subscribers, or different groups of subscribers. 
   Whilst participating in a PTT session, if the user of mobile telephone  202   a  wishes to send an MMS message to all the current participants of the session, the user opens the MMS message client application, creates the message, and sends an MMS message to the telephone subscriber number of the aforementioned contact “Current Session”. Since MMS client applications are generally designed to interrogate the electronic address book, this operation is simple for the user to perform. 
   The MMS system  308  sends the MMS message to the telephone subscriber +33123456. The PTT proxy  304  receives the MMS message and extracts the telephone subscriber number of the originator of the message, in this case mobile telephone  202   a . The PTT proxy performs an appropriate address resolution on the originator telephone subscriber number, as described above, and obtains the SIP URI of the originator of the message, in this case the SIP URI of the mobile telephone  202   a.    
   The PTT proxy  304  determines, through table  310 , to which session the mobile telephone  202   a  is participating in, in this case session  1 . From table  312 , the PTT proxy  304  retrieves details of the SIP URIs of each of the participants of session  1 . 
   The PTT proxy  304  performs an address resolution on the retrieved SIP URIs to obtain the telephone subscriber numbers for the participants in session  1 , and uses this information to request the MMS system  308  to resend the originally sent MMS message to each of the participants of the current session, i.e. mobile telephones  202   b  and  202   c . The MMS message can be sent to all of the determined participants, although it will be appreciated that, for example due to network problems or constraints, it may not be possible for all of the participants to receive the MMS. 
   Although the above embodiments have been described above with reference to a initiating an MMS communication whilst participating in a PTT session, those skilled in the art will appreciate that the inventive concepts described herein are in no way limited thereto. For example, the same or similar concepts may be applied to other session-based and session-less communication services such as instant messaging, conferencing, SMS, and any other suitable communication services. Use of the term mobile telephone is not limited thereto, and use of any suitable communication devices, such as personal digital assistants, personal computers, and the like, may be used.