Abstract:
A method and apparatus for including media content in a session invite procedure for a push to talk type service in a radio communication network. Client A sends an invitation to Client B inviting Client B to establish a push to talk type session. The invitation includes a representation of the media content, smaller than the media content itself. The representation may be a compressed or reduced-size or reduced-resolution version of the media content or an extract thereof. The representation is displayed or played to the Client B user, who decides whether to accept the invitation. The invitation may be a Session Initiation Protocol (SIP) Invite message, and the service may be a push to talk over cellular (PoC) service.

Description:
[0001]    This application claims the benefit of European Patent Application No. 05110141.8, filed Oct. 28, 2005, the disclosure of which is fully incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to methods and apparatus for use in a push to talk type service, for example a so-called push to talk over cellular service. 
         [0004]    2. Description of the Related Art 
         [0005]    Walkie-talkie type services have long proved popular amongst users who wish to communicate brief messages quickly between one another. Conventionally, such services have been provided by two-way portable radios which utilise a dedicated part of the radio spectrum, but which only allow users to communicate with a small group of pre-selected users who utilise similar terminals and who are within range of the relatively short operating range of the radios. More recently, services have been introduced into the United States which piggy-back on the existing cellular telephone infrastructure. However, these services have been proprietary in nature and have not allowed users to communicate between different operator networks. 
         [0006]    In an attempt to broaden the use of walkie-talkie type services, an industry grouping known as the Open Mobile Alliance (www.openmobilealliance.org) has been established with the aim of standardising suitable protocols which will allow inter-network operability for Walkie-Talkie services offered over cellular networks. The service established by the various standards is known as Push to talk Over cellular (PoC). PoC proposes that associated speech data will be transported over a packet switched access network. In the case of GSM and UMTS, this will be the general packet radio service (GPRS) or 3G access network. In other network architectures, analogous packet switched access networks will be utilised for transporting talk data. Push to Talk services may also be offered over circuit switched access networks, although this is not the preferred option. 
         [0007]    The Push to talk over Cellular (PoC) system is typically implemented on GSM/GPRS/3G networks and which makes use of the IP Multimedia Subsystem (IMS) standardised by the 3 rd  Generation Partnership Project to facilitate the introduction of advanced data services into cellular networks, and in particular of real-time multimedia services. The IMS relies upon the Session Initiation Protocol (SIP) which has been defined by the Internet Engineering Task Force (IETF) for the setting up and control of multimedia IP-based sessions. A PoC Server is located within the IMS or is attached thereto, and implements the functionality for setting up and controlling PoC Sessions. 
         [0008]    Existing push-to-talk (PTT) and conferencing systems typically use a control mechanism to grant one of the users the right to speak while other users in the communication are denied such right and are in listening mode. Such control mechanism is typically referred to as floor control, talker arbitration, talk burst control, etc. For example, the Open Mobile Alliance is currently working on a specification of Push-To-Talk over Cellular (PoC) system, which includes Talk Burst Control Protocol (TBCP). 
         [0009]    To request the right to speak on behalf of the user, the terminal (PoC Client) typically sends a request message to the controller (PoC Server). The controller typically responds either granting or rejecting the request. The controller typically restricts the time the user is allowed to talk, typically by starting an allowed talk timer when it grants the request, and uses some mechanism to interrupt the user, typically by sending a revoke message to the user&#39;s terminal or by simply not forwarding the user&#39;s media. The user who is interrupted by the controller is typically penalised by the controller in some way, e.g. by not granting the user the right to speak for a certain period of time. 
         [0010]    The next version of OMA PoC (herein called “PoC 2”, with the previous version being called “PoC 1”) is evolving in OMA. In PoC 1 the invitations are plain session invitations, whereas in PoC 2 the invitation may contain some multimedia content, such as a picture. The following extract is from the OMA PoC 2 Requirement Document [OMA-RD-PoC-V2 — 0-20050902-D Push to Talk Over Cellular 2 Requirements, Draft Version 2.0-02. September 2005]: “When inviting PoC User(s) to a PoC Session or when sending Group Advertisement message the media components can be added to the requests”. Also from the OMA PoC 2 Requirement Document: “A PoC Client MAY add media component(s) to the PoC Session invitation(s) sent to PoC User(s)”; “A PoC Client SHALL support receiving of PoC Session invitation(s), which MAY include media component(s). Depending on the PoC Clients capability for the included media component(s) PoC Client SHOULD replay the received media component(s)”; “A PoC Client MAY add media component(s) to the Group Advertisement message(s) sent to PoC User(s)”; “A PoC Client MAY support the receiving Group Advertisement message(s), which MAY include media component(s) from PoC User(s). Depending on the PoC Clients capability for the included media component(s) PoC Client SHOULD replay the received media component(s)”; “The PoC Service infrastructure MAY add/remove/change media component(s) to the PoC Session invitation(s) according to the configuration set by inviting and invited PoC Client”; “Media component SHALL be either a reference to the media content or contain the content directly. Examples of content types can be found in [RFC 2046, Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types]”; “The PoC Service infrastructure MAY be able to add/remove/change media content according to the reference to the media content”; “It SHALL be possible to limit the size and content of the media component(s) based on the service policies of the PoC service providers of the inviting and invited PoC subscribers and/or setting of inviting PoC client and invited PoC client”; “The PoC Service infrastructure SHALL be able to filter out the included media component based on the service policies of the PoC service providers of the inviting and invited PoC subscribers and/or setting of inviting PoC client and invited PoC client”; and “Settings by the PoC Service infrastructure SHALL have precedence over settings by PoC clients”. 
         [0011]    An invitation to a PoC Session is made by a SIP Invite message. Including a media payload into the SIP message is possible, but if it is of any reasonable size then this will have severe consequences for the SIP infrastructure (such as the Call Session Control Function or CSCF). Sending this form of payload in a SIP message will flood all the SIP stacks and the overall performance will be compromised. 
         [0012]    It is desirable to address this problem. 
       SUMMARY OF THE INVENTION 
       [0013]    According to a first aspect of the present invention there is provided a method of including media content at least to some extent in a session invite procedure of a push to talk type service, comprising sending a representation of the media content in a message inviting a second terminal to establish a push to talk type session with a first terminal, and separately sending the media content itself, the representation being smaller than the media content itself. 
         [0014]    The method may comprise sending the representation in the session invite message only if it is determined that the media content is larger than a predetermined size, and otherwise sending the media content itself in the session invite message. 
         [0015]    The method may comprise sending the session invite message from the first terminal to a server designated to control the session, and forwarding the invite message from the server to the second terminal. 
         [0016]    The method may comprise producing the representation from the media content. 
         [0017]    The representation may be produced at the first terminal. 
         [0018]    The method may comprise sending the media content such that it is available for use at the second terminal after the session invite has been accepted at the second terminal. 
         [0019]    At least one of the session invite message and the media content may be sent from the first terminal to the second terminal. 
         [0020]    The method may comprise sending the media content after the session invite has been accepted at the second terminal. 
         [0021]    A floor may be granted to the first terminal following acceptance of the session invite, and the method may comprise sending the media content over the granted floor. 
         [0022]    The method may comprise sending the media content without an explicit request for it from the second terminal. 
         [0023]    The method may comprise sending the media content in response to a request for it from the second terminal. 
         [0024]    The method may comprise receiving the media content at the second terminal as a background process on the second terminal. 
         [0025]    The representation may comprise an extract from the media content. 
         [0026]    The representation may comprise at least part of the media content to which compression and/or resolution reduction has been applied. 
         [0027]    The media content may comprise one or more of image content, video content and audio content. 
         [0028]    The method may comprise presenting the media content at the second terminal following receipt. 
         [0029]    Presenting the media content may comprise, in the case of image content, displaying the image content on a screen of the second terminal, and, in the case of video content, playing the video content on a screen of the second terminal, and, in the case of audio content, playing the audio content on a speaker of the second terminal. 
         [0030]    The media content may be presented in response to a request from a user of the second terminal. 
         [0031]    The invite message may be an Invite message of the Session Initiation Protocol. 
         [0032]    The push to talk type service may be a push to talk over cellular service. 
         [0033]    The push to talk type service may be a conferencing service. 
         [0034]    The invite message may comprise at least an implicit floor request for the requested session. 
         [0035]    The method may comprise processing the media content before sending it. 
         [0036]    According to a second aspect of the present invention there is provided an apparatus operable to include media content at least to some extent in a session invite procedure of a push to talk type service, comprising means for sending a representation of the media content in a message inviting a second terminal to establish a push to talk type session with a first terminal, and separately sending the media content itself, the representation being smaller than the media content itself. The apparatus may comprise the first terminal. 
         [0037]    According to a third aspect of the present invention there is provided a method of including media content at least to some extent in a session invite procedure of a push to talk type service, comprising receiving a representation of the media content in a message inviting a second terminal to establish a push to talk type session with a first terminal, and separately receiving the media content itself, the representation being smaller than the media content itself. 
         [0038]    According to a fourth aspect of the present invention there is provided an apparatus operable to include media content at least to some extent in a session invite procedure of a push to talk type service, comprising means for receiving a representation of the media content in a message inviting a second terminal to establish a push to talk type session with a first terminal, and separately receiving the media content itself, the representation being smaller than the media content itself. The apparatus may comprise the second terminal. 
         [0039]    According to a fifth aspect of the present invention there is provided an operating program which, when loaded into an apparatus, causes the apparatus to become an apparatus according to the second or fourth aspect of the present invention. 
         [0040]    According to a sixth aspect of the present invention there is provided an operating program which, when run on an apparatus, causes the apparatus to carry out a method according to the first or third aspect of the present invention. 
         [0041]    The operating program may be carried on a carrier medium. The carrier medium may be a transmission medium. The carrier medium may be a storage medium. 
         [0042]    An embodiment of the present invention enables the load on the SIP infrastructure for multi media invitations to be limited, at the same time as making it possible effectively to convey large content by way of the invitations. 
         [0043]    An embodiment of the present invention provides a two-step approach that transfers a miniature of the multimedia content at the same time transferring the original content over the media plane. 
         [0044]    In an embodiment of the present invention, the sender of a multimedia invitation can make a resized copy of the multimedia content and send that in the invite over the control signal channel. The maximum size for the resized content may be set by the client or the service provider policy and then notified to the client. 
         [0045]    The terminating controlling server may have the option based on user configuration to remove the multimedia parts of the invite message and thereby render it a non-multimedia (“a normal”) invite towards the invited user. In the accept or deny reply for that invite, the server (or implicitly by the reply from the invited user) may inform the inviter to that the invited user does not use a multimedia invite but may accept the session invitation anyhow. In that case, the large content is not sent. 
         [0046]    The multimedia invite may be an implicit floor request for control of a floor appropriate to send the content over. The floor may either be content dependent, or a dedicated floor used only for multimedia invites. 
         [0047]    In an embodiment of the present invention, the large (not resized) content is distributed over the floor to the recipient as soon after the floor has been granted to the inviter. 
         [0048]    In an embodiment of the present invention, the invited user first receives an invitation to a PoC Session in their display, and if they accept this then they will have the option of viewing the large content. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0049]      FIG. 1  is a message exchange diagram schematically illustrating the exchange of messages between two PoC Clients and a PoC Server in an embodiment of the present invention; and 
           [0050]      FIG. 2  is a block diagram schematically illustrating parts of the PoC Clients of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0051]    In one embodiment of the present invention, large media content intended for inclusion in a multimedia invite is sent in two stages. In one example, where the media content comprises a picture, a copy of the picture is resized to a size suitable to transfer over SIP, for example to a size associated with an icon or thumbnail, and sent in the session invite. This is displayed on the terminating side as a thumbnail when the invitation is received, and can be used by the user as a basis for deciding whether or not to accept the invite. If the invite is accepted and the floor granted, the large unmodified picture is transported over the floor responsible for picture media. This is done in the background, and if the recipient decides after a time to view the full picture then it will be available immediately for display by clicking on the thumbnail. 
         [0052]    It is likely that there will be a limitation as to how large a picture (or other type of media content) the SIP signalling network will be able to handle. SIP, as such, does not prevent the inclusion of a large payload in a SIP message such as a SIP Invite. However the SIP/IMS infrastructure, and in particular for the PoC domain the CSCFs of the SIP/IMS infrastructure, will nevertheless be put under strain if asked to handle a large amount of data. The SIP/IMS infrastructure is optimised for fast processing of the session signalling with only small messages without payload. If a large payload is included in the SIP messages then the SIP stacks in the SIP/IMS infrastructure will be flooded, leading to a poor overall system performance. 
         [0053]    The upper limit on the payload part of a SIP message sent over the SIP/IMS infrastructure could, for example, be set at 1 kB, although the actual limit will of course depend on many factors. This magnitude of size would not be able to convey a large picture, but more like an icon or thumbnail, or a picture with low resolution. 
         [0054]    With the evolution of today&#39;s handsets, with more and more advanced camera functions, it is likely that a user would wish to take a picture and use that as the “hook” to start a conversation with a third party. One possibility is to send only a suitably downsized version of the picture to the third party in the SIP Invite message. However, the picture might then be too limited to show all the details to the third party. 
         [0055]    In an embodiment of the present invention, the image transfer is divided into two stages in order to provide acceptable functionality for the user, and at the same time operate within the limitations of the payload restrictions of the SIP/IMS infrastructure. 
         [0056]    The idea is to send a small (resized) picture over the SIP infrastructure. This will be able to be displayed directly to the end user as part of the invitation information to the end user. Subsequently, the larger version of the picture is transferred in the background. 
         [0057]    A basic concept that can be used in an embodiment of the present invention is the implicit floor request from PoC 1. With this concept, when a users sends a SIP Invite message to other users in order to start a PoC Session, it also makes an implicit floor request. This is in order to speed up the user getting the right to speak. The same concept can be used in an embodiment of the present invention, so that when the user sends a multimedia invitation for a PoC session, it will at the same time request the floor for the media contained in the invitation. Therefore the client can start to send the larger version of the media (preferably in the background) as soon as it is granted the floor. 
         [0058]    An embodiment of the present invention will now be described in more detail with reference to  FIGS. 1 and 2 .  FIG. 1  is a message exchange diagram illustrating the exchange of messages between PoC Clients A and B and a PoC Server S in this embodiment, while  FIG. 2  is a block diagram schematically illustrating parts of the PoC Clients A and B (the PoC Server S is not shown in  FIG. 2 ). PoC Client A comprises a storage portion A 1 , a processing portion A 3 , and a communications portion A 5 ; these parts operate under overall control of a management portion A 7 . PoC Client B comprises a storage portion B 1 , a presenting portion B 3 , and a communications portion B 5 ; these parts operate under overall control of a management portion B 7 . 
         [0059]    Referring to  FIG. 1 , in step  1  the picture to be sent is retrieved from the storage portion A 1  of PoC Client A and is processed by the processing portion A 3  of PoC Client A to produce a reduced-size representation for inclusion in the SIP Invite of step  2 . In this example, the user of PoC Client A wishes to start a PoC Session with the user of PoC Client B to discuss or exchange information about fishing, and so the image selected by the user of PoC Client A is chosen appropriately. 
         [0060]    In step  2 , an invitation to a PoC Session is sent from the communications portion A 5  of PoC Client A to the PoC Server S. The invitation is a SIP Invite message containing the reduced-size representation of the picture. 
         [0061]    In step  3 , the PoC Server S forwards the SIP Invite message to the intended recipient, the PoC Client B. This is received at the communications portion B 5  of PoC Client B, and the reduced-size representation of the picture is extracted from the Invite message and displayed on the presenting portion (display portion) B 3 . Having viewed the reduced-size representation, the user of PoC Client B chooses to accept the session invitation (with acceptance signalling not shown). 
         [0062]    In this embodiment, the invitation from steps  2  and  3  is also an implicit floor request (for example as defined in PoC 1), and in step  4  the floor is granted to PoC Client A with a message from the PoC Server to PoC Client A. 
         [0063]    In step  5 , the large picture is retrieved from the storage portion A 1  and is transmitted from PoC Client A over the floor using the communications portion A 5 . The large image is received at the communications portion B 5  of PoC Client B, and is stored in the storage portion B 1  of PoC Client B. This happens in the background from the point of view of PoC Client B. 
         [0064]    Should the user of PoC Client B now wish to view the larger image, they would (for example) be able to click on the reduced-size representation on the screen, and the larger image that has been transferred in the background can be retrieved from the storage portion B 1  and viewed. 
         [0065]    It may be that PoC Client B has a user configuration or a service provider policy that does not allow multimedia invites. In that case, the PoC server S might have the option to remove the multimedia part of the SIP Invite message before forwarding it to the client. The invitation reply from the invited user will indicate that the multimedia part of the invitation will not be accepted, so that the transfer of the larger payload will not be carried out. 
         [0066]    Although the above illustration has focussed on the transfer of pictures, it will be appreciated that an embodiment of the present invention can be applied in a corresponding manner to other media types. For example, for video the reduced-size representation might comprise only the first frame of the clip, or another frame chosen by the user, or an extract from the video, or part of the video with a compression or size reduction algorithm applied, or a combination of these. The application to other media types such as audio will be readily apparent to the skilled person. 
         [0067]    Although an embodiment of the present invention is described above in relation to PoC, it will be appreciated that the invention is not limited to PoC. The term “push to talk” service is used here to identify services of a walkie-talkie nature. These are services that allow two or more users to be connected together quickly for the exchange of talk bursts. Push to Talk services differ from conventional voice calls in that these services allow only one person to talk at a given time. In order to talk, users must have control of the “floor”. Control is typically achieved by one user releasing a talk button to release floor control, and another user pressing a talk button to assume floor control. It is to be understood that the term “push to talk” used in the appended claims is not intended to imply the use of any particular protocol. 
         [0068]    It is also to be understood that the scope of the present invention is not limited to the transfer of talk or speech data in a talk session, and the appended claims are to be read as covering the transfer of any type of data in a data transfer session, including but not limited to speech data. As such, terminology such as “Talk Burst Request” and “Talk Burst” is not to be interpreted as being limited to talk, i.e. speech, data only, but is used for consistency with PoC 1 terminology; such phrases can include within their meaning the transfer of any type of data. In PoC 2, different terminology may be used for concepts that correspond directly with those in PoC 1; for example the phrases “Media Burst Request” and “Media Burst” may be used instead. 
         [0069]    It is also to be understood that the scope of the present invention is intended to include conferencing systems in which a participant is granted floor control and hence the right to speak or transfer data to other participants in the conference. 
         [0070]    It will be appreciated that operation of one or more of the above-described components can be controlled by a program operating on the device or apparatus. Such an operating program can be stored on a computer-readable medium, or could, for example, be embodied in a signal such as a downloadable data signal provided from an Internet website. The appended claims are to be interpreted as covering an operating program by itself, or as a record on a carrier, or as a signal, or in any other form.