Abstract:
A broadcast network  1  is described in which to improve network efficiency and quality of service, a particular transmitter  11   a  within the network  1  is selected to transmit content to a particular, preferably mobile terminal  3.  The selection of the transmitter  11   a  is carried out by reference to information available in a second network  27,  the user of the terminal  3  having a further terminal  12  connected to the second network  27  and either integrated with or in close proximity to their mobile terminal  3.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to the delivery of content over a broadcast network, particularly although not exclusively a broadband digital broadcast network.  
           [0002]    Broadband digital broadcast networks are known in which video and audio data are transmitted to a users equipped with suitable receivers. One such well known network is the terrestrial Digital Video Broadcasting (DVB-T) system found in Europe and elsewhere where the video and audio data comprises a plurality of channels allowing the user to select from a range of content. It has also been proposed to utilise such networks not only for the transmission of video and audio data but also for the delivery of more general data types including TCP/IP data traffic.  
           [0003]    The delivery of more general data types such IP data as may differ from the typical delivery of video and audio data in that rather than the network operator providing the same content to all users (broadcast), a specific user (unicast) or group of users (multicast) may require specific content. In order to deal with such a range or transmission scenarios, the addressing of content using conditional access has been proposed. Conditional access adds a unique, usually encrypted, identifier to content such that only a receiving terminal with the relevant decryption capability can receive the content. Further details of Conditional Access in relation to DVB can be found in the following ETSI Publications DVB-CI Common Interface Specification for Conditional Access and other Digital Video Broadcasting Decoder Applications EN50221 (V1:02/97) and Guidelines for Implementation and Use of the Common Interface for DVB Decoder Applications R 206 001 (V1: 1998) A025 (5/97).  
           [0004]    However, although conditional access allow the addressing of an individual terminal or, indeed a group of terminals, it nevertheless remains necessary to transmit content using all the transmitters in the network irrespective of whether the content is included in a broadcast, multicast, or unicast.  
         SUMMARY OF THE INVENTION  
         [0005]    According to a first aspect of the invention, there is provided a method for locating a terminal for delivery of content in a broadcast network comprising: associating the terminal with a transmitter operable in another network; interrogating the another network to determine the location of the transmitter; and delivering the content to the terminal at the location of the transmitter.  
           [0006]    According to a second aspect of the invention, there is provided a system for delivering content to a terminal in a broadcast network, the system comprising at least one terminal in a broadcast network, the terminal being associated with a transmitter in another network, wherein the broadcast network includes a processor operable to interrogate the another network to determine the location of the transmitter and thereby deliver content to the terminal at the determined location.  
           [0007]    According to a third aspect of the invention, there is provided an apparatus for delivering content to a terminal in a broadcast network comprising a processor operable to interrogate another network to determine the location of a transmitter associated with the terminal and deliver content to the terminal at the determined location.  
           [0008]    The another network may be a public land mobile network. In which case, the transmitter associated with the terminal may be a mobile station. Thus, the terminal may be associated with a mobile station in the control of a single user. Consequently, the another network might make available, at the request of the user, location details relating to the mobile station to the broadcast network.  
           [0009]    According to another aspect of the invention, there is provided head end apparatus for use in a first multi-transmitter broadcast network, the apparatus comprising a terminal locator operable in response to a request to deliver content to a terminal in the first network to obtain terminal location information from a second, different network, a memory having stored therein transmitter location information and a controller operable in response to the request to transmit content to determine from the terminal and transmitter location information a suitable transmitter to deliver the content to the terminal.  
           [0010]    Advantageously, as a result of the more effective utilisation of the transmitter network there is an improvement in service quality and spectral efficiency of the network. Such an improvement arises in the first case because the network can select a transmitter which meets the particular reception requirements for the Terminal receiving that content. Thus, where it is known that in a particular area there exist terrain features, for example, which dictate against the use of one transmitter in favour of another this information could be used in selecting a transmitter to transmit to a terminal in that area. In the second case, the ability to select a particular transmitter means that the frequencies previously used by the other transmitters to deliver that content are freed for other purposes. The apparatus may further include a router to route content to the suitable transmitter. The router may be responsive to data stored with content to be transmitted identifying the suitable transmitter.  
           [0011]    According to another aspect of the invention, there is provided a terminal for use with a first multi-transmitter broadcast network, including a receiver operable to receive content transmitted by a selected one of a plurality of transmitters of the first network and a further transmitter connected to a second network from which the first network derives information relating to the location of the further transmitter to facilitate selection of the one transmitter.  
           [0012]    Conveniently, the further transmitter is integrated in the terminal. In this way, the user can be certain that the content will be delivered to the correct location. Alternatively, the terminal may include an interface to permit connection to an external transmitter such as a mobile station of a cellular network. In either case, the further transmitter may also be used to provide a back or return channel which could be used to acknowledge delivery of content to the terminal and might also be used to make requests for content. Where no such acknowledgement ability exists, the assumption is, of course, that the further transmitter is reasonably certain to be co-located with the terminal. Furthermore, a profile might be established for each terminal user which could be consulted by a service provider desirous of delivering content to terminals of users likely to be interested in the content.  
           [0013]    According to still further aspect of the invention, there is provided a system for delivering content to a mobile terminal comprising a first broadcast network having a plurality of transmitters, and at least one terminal, the terminal having a receiver for receiving content from the first network, and in proximity thereto a further transmitter connected to a second network from which the first network derives information relating to the location of the further transmitter, wherein the selection of a transmitter to deliver content to the terminal is made in accordance with the location information.  
           [0014]    Whilst according to another aspect of the invention there is provided a method of delivering content using a suitable transmitter of a first broadcast network to a first terminal in proximity to a second terminal of a second network comprising deriving location information relating to the second terminal from the second network and utilising that information in the selection of a suitable transmitter.  
           [0015]    The selection of a suitable transmitter is preferably made based on the coverage pattern or footprint of the transmitter. Advantageously, where the position of the second terminal is insufficiently well defined to enable the selection of a particular transmitter from a plurality of potential suitable transmitters, delivery of the content is attempted via each of the potential transmitters in turn. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    In order to aid in understanding the present invention, a particular embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:  
         [0017]    [0017]FIG. 1 is a diagrammatic view of a digital broadcast network according to an embodiment of the present invention;  
         [0018]    [0018]FIG. 2 is a more detailed diagrammatic view of the network of FIG. 1;  
         [0019]    [0019]FIG. 3 is schematic view illustrative of part of the method according to the invention; and  
         [0020]    [0020]FIG. 4 is a diagrammatic plan view of a transmitter coverage pattern generated by the network of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    Referring to FIG. 1, this shows a terrestrial digital video broadcast (DVB-T) network  1  having a plurality of transmitters  11   a ,  11   b ,  11   c . A user equipped with a suitable Digital Receiver (DR) hereinafter referred to as a terminal  3  incorporating a receiver  5 , display  7  and user interface  9 , can receive data broadcast by the network  1  from a transmitter  11  forming part of the network  1 . The data broadcast by the transmitter  11  is derived from a variety of sources  13 , 15  via gateways  17 , 19  and may respectively include TCP/IP, datagrams (UDP/IP) and Television content. Furthermore, as is becoming increasingly common, the user is also in possession of a mobile station (MS) forming part of a Public Land Mobile Network (PLMN). The MS is interfaced with the terminal  3  over an infrared link  14 .  
         [0022]    Before transmission, the data received from a source  13 , 15  is processed in head-end equipment. As is well known in the art, the head end equipment places the data into MPEG-based data containers. To cater for the delivery of data to a particular terminal or group of terminals, the containers may also hold address information which can be identified and read by a conditional access component in the terminal do determine whether the data is intended for that terminal. The network  1  also provides the facility for suitably equipped terminals  3  to interact with the network  1 . Thus, a user may request the delivery of a computer file via the network  1  to her terminal  3 . Such functionality requires a return channel  23  from the terminal  3  to the DVB-T network  1  and a conditional access component in the terminal  3 . The return channel  23  can be provided in the form of a dial-up connection using a modem function of the MS  12 . The MS  12  which is connected to the terminal  3 , establishes a connection over a telecommunications network  27  such as a PLMN and/or PSTN  27  to a subscriber management system (SMS)  29  (shown externally of network  1  for clarity only) of the DVB-T network  1 . The subscriber management system  29  has connections to both the gateways  17 , 19  and the transmitter head-end equipment. It is thus possible for the user to issue a request for specific content via the user interface  9  of the terminal  3 . The request is received by the SMS  29  which obtains the content from the relevant gateway  17 , 19  and passes it to the transmitter head-end for placing into data containers for onward transmission. It should be noted that the request from the user might include a request for content which is not presently being transmitted by the network  1 . To ensure that the user only receives the requested content, the data is broadcast with an identifier which the conditional access component in the terminal  3  recognises as being intended for delivery to the user. In the event that the content is received by another terminal, the conditional access component of that terminal will prevent delivery of the content.  
         [0023]    In the situation illustrated in the FIG. 2, a user has requested via her return channel  23  a specific item of content R C . The return channel  23  in this instance is provided by the MS  12  connected, in use, to the PLMN  27 . In this instance, the user has requested using her terminal  3 , a webpage made up of textual and graphical material, although the request could have been for a particular channel of television content. The request R C  from the user is passed via the IR link  14  to the MS  12  which connects via the PLMN  27  to the SMS  29  of the broadcast network  1 , where it is identified as being a request for Internet content. The SMS  29  passes the request to the appropriate gateway, in this case the Internet gateway  17 . This gateway  17  processes the request R C  and retrieves the requested content C, from the Internet. The content C, which, as has already been explained, is made up of textual and graphical elements, is returned to the SMS  29 . In the meantime, the SMS  29  attempts to identify firstly whether the terminal  3  for which the content is intended is mobile or fixed. Thus, the SMS  29  queries a database  30  to obtain a user profile for the user identified in the request R C . If the terminal  3  is found to be fixed then the content will be broadcast in the known manner. Otherwise, the SMS  29  seeks to determine from the request R C  whether it originated in the terminal  3  itself or from another external source such as a push from an advertiser or the like. Should the SMS  29  determine that the request R C  has come from the terminal  3  then the SMS  29  will attempt to determine the calling line identity (CLI) of the MS  12  sending the request R C . If the CLI is not available or alternatively the request originated externally as a push, the SMS  29  retrieves a mobile telephone number of a MS, which number has previously been supplied by the user for storage in the user profile.  
         [0024]    Referring particularly to FIGS. 3 and 4, these illustrate the coverage patterns and overlap of individual transmitters of a digital broadcast network (chain lines) and base stations of a Public Land Mobile Network (solid lines). Once the SMS has determined a number, a direct connection is then established to a Home Location Register (HLR)  31  of a Public Land Mobile Network (PLMN)  27  identified as being the home network of the number found by the SMS  29 . In response to a request  100  from the SMS  29 , the PLMN  27  provides  110  an indication, if available, of the latest cell (LC) (shown hatched in FIG. 3) in which the MS  12  corresponding to that identified from the CLI or failing that the number stored in the user profile is located. The SMS  29  passes the latest cell indication returned by the HLR  31  together with the retrieved content C to a transmitter mapper  35 . The transmitter mapper  35  identifies a transmitter  11   a  from those in the network  1  whose footprint (FP) includes most, if not all, of the latest cell (LC) identified by the HLR  31 . The mapper  35  may carry out the identification of the most suitable transmitter using a look-up table in which cells of the PLMN  27  are cross-referenced with a suitable transmitter, for example. This information is then attached to the content C, the latter having been encrypted as an MPEG-2 data stream before both the transmitter and content information are passed to a router  37 . The router  37  retrieves the information identifying the transmitter assigned to the content C by the transmitter mapper and passes the content C it to the appropriate transmitter  11   a  for transmission  120 . The user&#39;s terminal  3 , which hopefully has remained within the footprint FP a  of the transmitter, is then able to receive the content C.  
         [0025]    Optionally, where the terminal  3  is provided with a return channel  23  via the MS  12 , this can be utilised in the generation of a delivery status report  130 . Such an acknowledgement is not, however, a requirement, it being assumed with a reasonable probability that a user will be carrying her MS  12  along with her terminal  3 . However, where acknowledgement is possible and desirable the status report  130  is passed  140  over the return channel  23  via the PLMN  27  to the SMS  29  and contains confirmation of whether the content C has reached the terminal  3  successfully. Where the request R C  was originated in the terminal  3  and In the event that the content C does not reach the terminal  3  within a pre-determined period, the terminal  3  will generate a report indicating that no delivery has taken place. Otherwise, where the request was originated in the terminal  3  and their followed successful reception of the content C, a corresponding report will be made. In the event that the SMS  29  receives a report of unsuccessful delivery then the SMS  29  will first attempt to re-send the content C. Thus, the SMS  29  will first update the MS  12  location from the HLR  31 . Should this update reveal that the MS  12  remains in the same cell, it may be that the MS  12  is within a region of the cell covered by a different transmitter footprint FP. Thus, whilst the update continues to indicate the same location cell, the SMS  29  will instruct the mapper  35  to provide details of each transmitter covering at least part of that cell so that content C may be sent by that transmitter. Otherwise, if the terminal has moved to a cell covered by a different transmitter footprint FP, that transmitter  11  will be used to deliver the content. However, in the event that the above described re-sends fail after a pre-determined number attempts, the content will be transmitted over all the transmitters in the network.  
         [0026]    In another embodiment of the invention, particularly suitable to a situation where the overlap of the transmitter footprints FP do not correspond closely to the underlying cell structure of the PLMN  27 , a different method of obtaining the location of the MS  12  is employed. In this case, instead of the SMS  29  obtaining the latest cell information from the HLR  31 , the SMS  29  requests the PLMN  27  to carry out a location update using a more precise positioning method such as base station triangulation or GPS. Particularly in the case where a MS  12  is located in a cell LC which is covered by separate transmitter footprints FP, the more accurate positioning information obtained in this way should allow the transmitter mapper  35  to direct the content C to the transmitter most likely to deliver the content to the terminal  3 .  
         [0027]    It will be further appreciated that the terminal  3  may incorporate a mobile station  12  rather than rely on the presence of an MS  12  in close proximity to the terminal  3  to provide the location information. By having the MS  12  incorporated in the same housing as the terminal  3  the user would both have less items of equipment to carry and also could be assured that the terminal  3  was always co-located with the mobile station  12  or, indeed another communications device which provides the positioning information for use by the network. In addition, the integrated MS  12  could be employed to provide a return channel  23  in the same manner that an independently carried MS  12  could be interfaced to the terminal  3  to facilitate the option of a return channel  23 .  
         [0028]    Furthermore, it will be clear that although in the above embodiment the Return Channel  23  is provided over the same network, namely the PLMN  27 , as is used to derive the location information, a separate return channel using a different bearer could be employed. Indeed, as has already been stated, the request for content need not originate with the terminal  3 . For example, an advertiser or service provider may wish to push particular content to a certain user or group of users perhaps located in a certain area relevant to the content being pushed.