GB2413038A

GB2413038A - A method of controlling transmission of data during communication sessions

Info

Publication number: GB2413038A
Application number: GB0408069A
Authority: GB
Inventors: Qing Xuan; David Fox; Gavin Wong
Original assignee: Vodafone Ltd
Current assignee: Vodafone Ltd
Priority date: 2004-04-08
Filing date: 2004-04-08
Publication date: 2005-10-12
Anticipated expiration: 2024-04-08
Also published as: GB2413038B; GB0408069D0

Abstract

A method and system of controlling a Push-to-Talk over cellular (PoC) communication session between a first mobile device 1A and a second mobile device 1B, each of which is associated with a communications network 7A,7B is described. A communication link is initiated between the first device 1A and the second device 1B for transmitting speech data front the first device 1A to the second device 1B. It is possible for the user of first device 1A to enter data in the form of text (or other non-audio/inaudible form). This text data are transmitted to PoC server 13A. A text to speech converter 19A then converts this text data into speech or voice data. Transcoder 25A may convert the speech or voice data using a particular CODEC suitable for allowing the speech or voice data to be reproduced on the second device 1B. The speech or voice data is then transmitted from the PoC server 13A to the second device where it is reproduced as audible speech. The communication could also be between a group of devices. A method of controlling IP-based communication between a plurality of devices is also shown.

Description

24 1 3038

TRANSMISSION OF DATA DURING COMMUNICATION

SESSIONS

The present invention relates to a method of and system for controlling a communication session between at least a first device and a second device, each of which Is associated with a communications network.

The third generation partnership project (3GPP) has recently defined a new concept known as IMS (IP - based Multimedia Subsystem). The aim of IMS is to allow users such as mobile telephone network operators to provide services to their subscribers as efficiently and effectively as possible. For example, the IMS architecture is likely to support the following communication types: voice, video, instant messaging, "presence" (a user's availability for contact), location-based services, email and web. Further communication types are likely to be added in the future.

This diverse collection of communication devices requires efficient session management due to the number of different applications and services that will be developed to support these communication types. The 3GPP have chosen Session Initiation Protocol (SIP) for managing these sessions.

The SIP protocol is a session-based protocol designed to establish IP based communication sessions between two or more end points or users. Once a SIP session has been established, communication between these end points or users can be carried out using a variety of different protocols (for example those designed for streaming audio and video). These protocols are defined in the SIP session initiation messages.

With IMS, users are no longer restricted to a separate voice call or data session.

Sessions can be established between mobile devices that allow a variety of communication types to be used and media to be exchanged. The sessions are 0 dynamic in nature in that they can be adapted to meet the needs of the end users. For example, two users might start a session with an exchange of instant messages and then decide that they wish to change to a voice call, possibly with video. This is all possible within the IMS framework. If a user wishes to send a file to another user and the users already have a session established between each other (for example, a voice session) the session can be redefined to allow a data file exchange to take place. This session redefinition is transparent to the end user.

According to a first aspect of the present invention, a method of controlling a push-to-talk over cellular (PoC) communication session for a group of mobile telecommunication devices, each of which is associated with a mobile telecommunication network, the method including establishing data for transmission to one or more devices in said group, converting said data Into a format capable of bemg reproduced as speech or voice output by the or each device, transmitting the converted data to the or each device during the communication session for reproduction as an audible output by the or each device.

According to a second aspect of the present invention, a system for controlling a push-to-talk over cellular (PoC) communication session between at least first and second mobile telecommunication devices, each of which is associated with a mobile telecommunication network, the system including means for establishing data for transmission to the first device, and means for converting that data into a format capable of being reproduced on the first device as speech or voice output, and means for transmitting the converted data to the first device during the communication session for reproduction as an audible output by the or each device.

According to a third aspect of the present invention, a method of controlling an IP-based communication session between a plurality of devices each of which is associated with a mobile communications network, the method including establishing data for transmission to one or more devices In said group, converting said data into a format capable of being reproduced as speech or voice output by the or each device, transmitting the converted data to the or each device during the communication session for reproduction as an audible output by the or each device.

According to a fourth aspect ofthe present invention, a system for controlling an IP-based communication session between at least a first device and a second device, each of which is associated with a mobile communications network, the system including means for establishing data for transmission to the first device, and means for converting that data into a format capable of being reproduced on the first device as speech or voice output, and means for transmitting the converted data to the first device during the communication session for reproduction as an audible output by the or each device.

A method and system for controlling a communication session between a first device and a second device via a telecommunications network, embodying the invention, will now be described by way of example, with reference to the accompanying drawings in which: Figure l shows schematically the components of a telecommunications system in accordance with the embodiment of the invention; and Figure 2 shows the exchange of data between elements of the communications network to estabhsh a PoC communication link. s

One application of IMS is push-to-talk over cellular (PoC). PoC allows a communication session to be established between a group of devices such that the user of one of the devices can speak and the users of each of the other devices will hear that person speak. During such a communication session each device functions like a two-way radio or walkie-talkie in a one-to-one or one-to-many group mode. Full duplex speech communication between the users of the respective devices during the communications session is not possible - only one user can speak at a time.

One feature of PoC is that, when the communication is established, there is an "always on" communication link between the devices. When a user wishes to talk to the or each of the other devices associated with the communication session, the user issues an appropriate instruction to their device (typically using a soft key - that is, a key whose function is programmable), and the user's speech is captured by their terminal and instantly, or within a relatively short period of time, is transmitted to the or each of the other terminals and Is reproduced on those terminals. There is no requirement for the user inputting the speech data to dial the or each other device, and nor is there any requirement for the users of the devices receiving the speech to take any action to receive the speech data - it is automatically reproduced by their device when it is received (assuming, of course, the device is operating In an appropriate mode for allowing PoC communication).

PoC is described in the document "Push to talk over Cellular (PoC) Architecture, Draft Version 1.0 - 13 February 2004" available from Open Mobile Alliance Limited (OMA).

In the embodiment to be described a PoC communication session is established using IMS. However, it should be appreciated that a PoC communication session in accordance with the invention could be established over existing GSM/GPRS networks by exchange of data packets but without IMS.

One of the advantages of PoC is that less bandwidth may be required for a PoC call (which uses the packet switched domain) than a normal voice call (which uses the circuit switched domain). In a circuit switched call, network capacity is used for the full duration of the call from the initial connection attempt to the time that the call terminates. Network capacity is used even when no speech data are transmitted. In a PoC call only the actual blocks of data that contain speech will be transmitted. A PoC communication session between devices might last one hour. However, if speech is only transmitted for five minutes during that hour, only network capacity corresponding to that five minutes is used.

Referring initially to Figure 1, a GPRS enabled mobile device 1A communicates wirelessly with radio network controller (RNC) 3A (in fact via a "node B", which is not shown for the sake of simplicity). A fixed (wired) connection between RNC 3A and serving GPRS support node (SGSN) 5A associated with mobile telecommumcations network 7A allows packet data to be transmitted between the mobile device 1A and the mobile telecommunications network 7A in the packet switched domain. Gateway GPRS support node (GGSN) 9A provides an interface between the mobile telecommunications network 7A and IMS (SIP) core 11A. The IMS core 11A contains SIP proxys and SIP registers. PoC server 1 3A is coupled to the IMS core 11A for providing PoC functionality (to be described in more detail below).

Group and list management server 1 5A is responsible for the management of contact lists (containing the addresses of other users), group lists (containing the addresses of other groups), access lists and permissions management. A contact is an Identity of a user, or a group. A contact includes the SIP URI or a TEL URI of the entity, type of the entity (user or group) and optionally the display name. Each PoC user has two access lists: a user accept list and user reject list. Access lists are used for controlling whether the PoC server is allowed or nc t to send talk session requests to the user when requested by other user. Each PoC user can define permission management rules that describe who is allowed to contact him/her using the PoC service. The PoC Server implements the access control policy according to these defined rules.

A presence server 17A is provided to provide the IMS core llA with information indicating whether or not devices associated with the mobile telecommunications network 7A are available for contact or not.

In accordance with a feature of the present invention a text to speech converter l 9A (also to be described in more detail below) is provided. The text to speech converter l 9A could in fact be part of the PoC server 1 3A.

In addition to the components described above, the network has a short message service centre (SMSC) 20A associated with it of generally conventional configuration and operation. The term "short message" refers to short messages as defined in the GSM and UMTS standards specifications.

Such messages are commonly in the form of text messages of limited maximum length. When device 1 A wishes to send a short message it will do this via RNC 3A and SMSC 20A. For example, if mobile device I A wishes to send a short message to another mobile device (device "X") associated with the network 7A, the sort message is automatically addressed by mobile device I A to the SMSC 20A, which then delivers the sort message to mobile device X (after registering the necessary details to enable a charge to be made to mobile 1A). Each short message therefore carries the address of the local SMSC (this address is automatically generated by the sending mobile device 1A), together with the address of the intended destination of the short message. When the local SMSC 20A receives the short message, it then reads the address (the MSISDN or the telephone number of the intended destination) and despatches the short message accordingly.

Figure 1 shows a second network including elements corresponding to the elements of the first network described above, which elements are designated for the same reference numeral but with the suffix "B" Data are exchanged between the IMS core 11A of the first network and the IMS core 1 IB of the second network using SIP signalling, which is transmitted, for example, via the Internet.

Of course, it should be appreciated that, although only one mobile device 1A and 1B, and one RNC 3A and 3B is shown associated with each mobile telecommunications network 7A and 7B, typically there will be a multiplicity of RNCs and mobile devices associated with each mobile telecommunications network 7A and 7B.

It Is also important to note that, although in the embodiment described the mobile terminal 1A is associated with a different network 7A from the mobile terminal 1B, the invention is equally applicable to a scenario where the users of two or more mobile terminals associated with the same mobile telecommunications network wish to establish a PoC session.

It will now be described what happens when the user of mobile device 1A wishes to establish a PoC communication session with the user of mobile terminal 1B.

To Establish a PoC communication session, the users of respective mobile devices will associate themselves in a group between which PoC messages may be sent by exchanging contact information and possibly other information (such as a password).

The user of mobile device 1A indicates that he/she wishes to establish a PoC commumcation session with the user of the mobile device 1B by sending a command from the mobile terminal 1A to the PoC server 13A, via RNC 3A, SGSN 5A, GGSN 9A and IMS core I 1A. The PoC server 13A will then consult the group and list management server 1 5A and the presence server 1 7A to determine the allowability and availability of the mobile terminal 1B to take part in a PoC communication session (or this information may be obtained from the group list and management server 1 5B and presence server 1 7B of the network 7B via the link between the IMS cores 1 1 A and 1 l B).

A PoC communication session is then established between mobile device 1A and mobile device 1B by the exchange of data between IMS cores 11A and 11B. The PoC servers 13A,13B make a record on each user's account with their network 7A,7B in order that an appropriate charge can be made (where necessary) for establishment of the PoC session.

In a PoC communication session there is only one PoC server performing a controlling PoC function. There could be more than one PoC server performing the participating PoC function in the PoC session. In the embodiment described, where there are only two devices in the PoC session, PoC server 13B will perform a controlling PoC function and a participating PoC function, and PoC server 1 3A will perform a participating PoC function.

The controlling PoC function: 15. Provides centralized PoC session handling Provides the centralized media distribution Provides the centralized floor control functionality including talker identification (for arbitrating requests from PoC clients - devices lA and 1B - for the right to speak) 20. Provides SIP session handling, such as SIP session organization, termination, etc. Provides policy enforcement for participation in group sessions Provides the participants information Collects and provides centralized media quality information Provides centralized charging reports The participating PoC function may:- Provide PoC session handling Provide the media relay function between PoC client (device IA,1B) and controlling PoC server Provide user media adaptation procedures 10. Provide the floor control message relay function between PoC client and controlling PoC server Provide SIP session handling, such as SIP session origination, termination, etc. on behalf of the represented PoC client Provide policy enforcement for incoming PoC session (e.g. access control, availability status, etc.) Collect and provide media quality information Provide the participant charging reports The IMS cores I IA and l 1B perform the following functions that are needed in support of the PoC service.

Routes the SIP signaling between the PoC client (devices 1 A and 1B) and the PoC server Provides discovery and address resolution services Supports SIP compression Performs authentication and authorization of PoC client based on user's service profile 5. Maintains the registration state Provides charging information While the PoC communication session is established, the user of mobile terminal IA can talk (that is, send speech data for reproduction on the device IB) by pressing soft key 21A, above which, during the PoC communication session, the sign "press-totalk" or "PTT" is displayed on the display 23A of the mobile terminal 1A. Of course, if more than one other device also joins the communication session, a plurality of soft keys may be provided, or a suitable graphical user interface provided, to allow entry of a command for speech data to be sent to any one of or all of the group of devices.

As shown In Figure 2, the mobile terminal 1A then issues a SIP INVITE message (message "1.") addressed to mobile device 1B (and, if intended for a group of devices, addressed to the group address if there is more than one terminating device) to IMS core 11A (via the intermediate elements shown in Figure 1). Message "1." may include the following information elements: a. contact identity information b. PoC address of the user initiating this PoC Session c. PoC service indication d. Media parameters of PoC client A (device 1A) e. Group address The IMS core 11A passes the SIP INVITE message (message "2.") to the PoC server 1 3A, which checks the availability and allowability of the transmission of speech dare to the device 1B by consulting group and list management server 15A/1SB and presence server 17A/17B, and makes an appropriate record for charging for the transmission of speech data (if required). Message "2." may include: a. contact identity Information b. PoC address of the user initiating this PoC Session c. PoC service indication d. Media parameters of PoC client A (device 1A) If the availability and allowability criteria are met, the PoC server 1 3A then identifies that device 1B is not hosted by PoC server l 3A, and it sends the SIP INVITE message (message "3.") to the IMS core 1 IA. Message "3." may include: a. contact identity information b. PoC address of the user initiating the PoC session c. PoC service indication d. PoC server l 3A (participating) selected media parameters The IMS core I lA transmits the SIP INVITE message (message "4.") to the IMS core l l B associated with the second mobile telecommunications network 7B. Message "4." may include: a. contact identity information b. PoC address of the user initiating the PoC session c. PoC service indication d. PoC server 1 3A (participating) selected media parameters The IMS core I IB then transmits the SIP INVITE message (message "5.") to the PoC server 13B. Message "5." may include: a. contact identity information a. contact identity information b. PoC address of the user initiating the PoC session c. PoC service indication d. PoC server 13A (participating) selected media parameters The PoC server 13B then generates an initiation message for the device 1B, which is sent to the IMS core 11B and transmitted to the mobile device 1B via GGSN 9B, SGSN 5A and RNC 3B. (Device 1B is not shown in Figure 2 for the sake of simplicity.) A response message "auto answer Indication" is received from the mobile device 1 B (assuming it is in an area of coverage by the mobile telecommunications network 7B) and this is passed to the PoC server 1 3B via the intermediate elements shown in Figure 1. A message "unconfirmed ok", advising of successful receipt of the SIP INVITE message by the device 1B, (message "6.") is transmitted from the PoC server 13B to the IMS core I 1B, and from there to the IMS core llA associated with the first mobile telecommunications network 7A (message "7."). The lMS core 1 1 A of the first mobile telecommunications network transmits this message (message "8.") to the PoC server 13A. The message (message "9.") is returned to the IMS core 11A, from where it is forwarded to the mobile device I A (message "10.").

Messages "6." to "8." may include PoC server 1 3B selected media parameters.

Messages "9." and "10." may include PoC server 13A selected media parameters.

Messages " I " to " 10" do not carry any speech. Transfer of speech does not use the SIP INVITE; it occurs after floor control 12 in Figure 2 as floor control determines whether the speaker is allowed to speak.

Audio data received by the microphone of the mobile terminal 1A is then captured by that mobile terminal and Is transmitted as packet data to the network 7A, and to the IMS core 11A, allowing the communication of this data to the IMS core l l B of the second network. This data are received by the mobile terminal 1 B where it is automatically reproduced by the loudspeaker of that mobile terminal as an audio signal, allowing the user of mobile terminal l B to receive and understand the speech of the user of mobile terminal 1A.

The speech data are reproduced by the mobile terminal 1B without requiring any user operation by the user of mobile terminal 1B. Typically the speech data will be reproduced by the terminal 1B at virtually the same time as it Is input to the mobile terminal 1A.

In accordance with an important feature of the embodiment, and as an enhancement to the PoC arrangement described above in relation to Figure 2, the user of device A may cause speech to be reproduced during the PoC communication session on selected other terminals to which the communication session relates without the user A having to have their speech captured and recorded. That is, the user of device A can cause audible speech to be reproduced on the other terminals without providing an audible speech source. For example, the source of data might be text.

Arrangements for converting text data into audible speech data ("text-tospeech" systems) are known in the prior art. Such systems are particularly useful to the visually impaired, but there are wider applications, such as sharing of information when it is not safe or appropriate to read textsuch as when driving. Known text-to-speech systems transmit speech data using circuit switched bearers in the manner of a conventional voice call. Further, known text-to-speech systems are capable only of distributing speech data on a point-to-point basis. That is, a separate communication link (telephone call) must be established to each destination device to separately transmit the speech data to each device. Therefore, in known systems, when it is desired to transmit the same speech data to a multiplicity of mobile terminals, the same amount of signalling and network capacity is used as would be used if different speech data were transmitted to each terminal. There is currently no means to address and deliver to a group of devices speech data derived from text (or another inaudible source) to a group of devices in an efficient manner that minimses the amount of signalling.

In the embodiment the known PoC architecture described above is used but with the addition of text to speech converter l9A.

A PoC session is activated in the manner described above in relation to Figure 2 in the known manner. The known PoC architecture is optimised only for having voice/speech (audible) data as both the input and output.

As indicated above, device A may generate data for communication to other devices in any non-audible form. Typically, this data will be generated in the form of text. This text may be entered by any suitable means, such as by operating the keys on the keypad 25A of device 1 A. The keypad 25A may be a numeric keypad or an alphanumeric (qwerty) keypad. Text data may be captured and stored by the mobile terminal I A before and/or during a PoC 1 5 session.

The text data may be transmitted from the device 1A as a conventional short message (SMS), in which case the text will be sent to SMSC 20A, and from there to the IMS core 1 1 A. The text may alternatively be transmitted by any other suitable means, such as email or as an instant message. Conveniently, the text data may be sent by activating a suitably programmed softkey 23A. As discussed above, once an IMS session Is established between devices, data of various formats can be transmitted between those devices in a seamless manner in the packet switched domain.

In this embodiment the text data are converted into speech data at the recipient's mobile device 1B. The requirement to reproduce the text data as speech data on device 1B may arise because the user of device 1B is visually impaired. However, reproducing the text data as speech data on the receiving device or devices has a further advantage: all conventional mobile telephone devices can reproduce speech data, and therefore the speech data derived from the text data from the originating device 1A or the network can be reproduced l O on any receiving device without the originating device 1A needing to know the capabilities of the receiving device (for example, whether it supports particular type of messaging, such as instant messaging or MMS). This is advantageous even if all the devices that are to communicate with one another do in fact have the same advanced communication capabilities because the signalling overhead to establish what these capabilities are Is avoided.

Thus far, the user of device 1A has entered text data into their mobile device 1A and this text data has been transmitted by any suitable mechanism to IMS core I lA. The text data are transmitted from the IMS core 11A to the PoC server 13A. Typically, the text data will be Intended for a multiplicity of recipient devices in a group of devices between which the PoC session has been established, of which recipient device 1B is one. The text data are routed to the PoC server l 3A usmg an identifier for the group (this identifier does not necessarily have to be a SIP URI as required for pure speech PoC implementations). When the PoC server 1 3A receives the message containing text data, this data are passed to text- to-speech converter 1 9A, in which the text data are converted into speech data using a suitable algorithm (examples of which will be known to those skilled in the art), where the speech is encoded using a common CODEC or a negotiated during setup of the PoC session - for example AMR- NB. AMR-NB (Adaptive Multi Rate-Narrow Band) is a speech CODEC standard introduced by the 3GPP.

The encoded speech is then passed to the PoC server 13A. The encoded speech may be passed by the PoC server 1 3A to a transcoder 25A in order to allow the encoded speech to be transcoded to other CODEC sets where some of the devices participating in the PoC session do not all use the same CODEC.

Therefore, the encoded speech representing the same text string may be created having different formats.

The CODECs supported by each device to which the PoC session relates may be determined during the setting up phase of the PoC session (as part of the negotiation procedure). The CODEC supported by each device will therefore be known to PoC server 13A, so that PoC server 13A may determine which CODEC should be used by the text-to-speech converter 1 9A and/or whether further transcoding is required by the transcoder 25A.

The speech data, encoded according to the different CODECs, is stored in the PoC server 13A, from where it is transmitted to all relevant participants in the group to which the PoC session relates. The encoded speech is reproduced on the recipient devices (of which device 1B is one) in the conventional manner.

Some of the recipient devices may be registered with the same network 7A as device 1 A, and some of the recipients may be registered in the network 7B of device l B. The speech data are transmitted between IMS core I l A of network 7A and IMS core I 1B of network 7B by a link between the IMS cores (and typically via the Internet). The IMS cores llA and llB will control the l0 distribution of data to relevant devices.

Encoding of the text using an appropriate CODEC means that the encoded/transcoded data transmitted by the IMS core to each device has the same basic format as conventional speech data transmitted to the device during a normal circuit switched voice telephone call. The recipient device does not need to process the received data in a manner different from conventionally received speech data in order to reproduce audible speech.

Increased efficiency is achieved due to the re-use of the existing PoC session established between the devices, which could be used for other purposes such as voice commumcation as described above.

Preferably, the encoded speech data (encoded/transcoded into the or eachdifferent CODEC) is transmitted only once from IMS core 1 IA to IMS core I 1B. When received, this transcoded speech data can be transmitted by IMS core llB to a multiplicity of mobile devices that are registered with the network 7B with which IMS core 11B is associated. This is advantageous because it avoids the requirement for transmitting the same transcoded speech data between IMS cores a multiplicity of times.

As an alternative to PoC, the encoded/transcoded speech data may be transmitted by another IP or IMS based mechanism.

Claims

A method of controlling a push-to-talk over cellular (PoC) communication session for a group of mobile telecommunication devices, each of which is associated with a mobile telecommunication network, the method including establishing data for transmission to one or more devices in said group, converting said data into a format capable of bemg reproduced as speech or voice output by the or each device, transmitting the converted data to the or each device during the communication session for reproduction as an audible output by the or each device.
2. The method of claim 1, wherein said data represents alphanumeric characters or text.
3. The method of claim I or 2, wherein said data are established at one of said devices.
4. The method of claim 3 when dependent on claim 2, wherein said data are estabhshed by the user of said one of said devices operating the keypad thereof to enter the alphanumeric characters or text.
5. The method of any one of claims 1 to 4, wherem the converting step includes translating the data, using a CODEC, into a format suitable for transmission to the or each device.
6. The method of claim 5, including determining a suitable CODEC for transmitting data to the or each device.
7. The method of claim any one of claims 3 to 6, wherein the data are transmitted from said one of the devices as a short message (SMS).
8. The method of any one of claims 3 to 6, wherein the data are transmitted from said one of the devices as an instant message.
9. The method of any one of claims 3 to 6, wherein the data are transmitted from said one of the devices on an email.
10. The method of any one of claims 3 to 9, wherein, the data are transmitted from said one of the devices in the packet switched domain.
1 1. The method of any one of claims 1 to 10, wherein the converted data is transmitted to the or each device in the packet switched domain.
12. The method of any one of claims 1 to 1 1, wherein the communications network comprises a GSM communications network.
13. The method of any one of claims 1 to 1 1, wherein the communications network comprises a UMTS (3G) communications network.
14. The method of any one of claims l to 13, wherein the communications network comprises a GPRS communications network.
15. The method of any one of claims 1 to 14, wherein the communication session comprises a session imtiation protocol (SIP) session.
l 6. A system for controlling a push-to-talk over cellular (PoC) communication session between at least first and second mobile telecommunication devices, each of which is associated with a mobile telecommumcation network, the system including means for establishing data for transmission to the first device, and means for converting that data into a l 5 format capable of being reproduced on the first device as speech or voice output, and means for transmitting the converted data to the first device during the communication session for reproduction as an audible output by the or each device.
17. The system of claim 16, wherein said data represents alphanumeric characters or text.
l 8. The system of claim 16 or 17, wherein said data are established at the second device.
19. The system of claim 18 when dependent upon claim 17, wherein said data are established by the user of the second device by operating the keypad thereof to enter the alphanumeric characters or text.
20. The system of any one of claims 16 to 19, wherein the converting means includes means for translating the data, using a CODEC, into a format suitable for transmission to the first device.
21. The system of any one of claims 16 to 20, wherein the transmitting means is operable to transmit the converted data to the first device and to a plurality of other devices between which the communication session is established.
22. The system of claim 20 or 21, including means for determining a suitable CODEC for transmitting data to the first device.
23. The system of claim 22, wherein said determining means determines a respective suitable CODEC for transmitting data to the first device and to each of said other devices.
24. The system of any one of claims 16 to 23, including means for receiving said data in the form of at least one of a short message (SMS), instant message and email.
25. The system of any one of claims 16 to 24, including means for receiving the data in the packet switched domain.
26. The system of any one of claims 16 to 25, including means for transmitting the converted data to the or each device in the packet switched domain.
27. The system of any one of claims 16 to 26, wherein the communications network comprises a GSM communications network.
28. The system of any one of claims 16 to 26, wherein the communications network comprises a UMTS (3G) communications network.
29. The system of any one of claims 11 to 25, wherein the communications network comprises a GPRS communications network.
30. The system of any one of claims 16 to 29, wherein the communications session comprises a session initiation protocol (SIP) session.
31. A method of controlling an IP-based communication session between a plurality of devices, each of which is associated with a mobile communications network, the method including establishing data for transmission to one or more devices in said group, converting said data into a format capable of being reproduced as speech or voice output by the or each device, transmitting the converted data to the or each device during the communication session for reproduction as an audible output by the or each device.
32. The method of claim 31, wherein the communication session is a pushto-talk over cellular (PoC) communication session.
33. The method of any one of claims 31 or 32, wherein the communication session comprises a session initiation protocol (SIP) session.
34. A system for controlling an IP-based communication session between at least a first device and a second device, each of which is associated with a mobile communications network, the system Including means for establishing data for transmission to the first device, and means for converting that data into a format capable of being reproduced on the first device as speech or voice output, and means for transmitting the converted data to the first device during the communication session for reproduction as an audible output by the or each device.
35. The system of claim 34, wherein the commumcation session is a push totalk over cellular (PoC) communication session.
36. The system of claims 34 to 35, wherein the communication session comprises a session initiation protocol (SIP) session.
37. A method of controlling a communication session substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.
38. A system for controlling a communication session substantially as hereinbefore described with reference to and/or substantially as illustrated in any one of or any combination of the accompanying drawings.