Abstract:
A mobile communications network comprises a network manager for managing a plurality of mobile stations in the network, a first database holding subscriber information for mobile station subscribers in the network and in communication with the network manager via a signalling interface over which information is conveyed using one of a plurality of signalling protocols, at least one second database for communication with a packet data network via a packet data interface over which information is conveyed using one of a plurality of packet transmission protocols, said second database holding subscriber information for subscribers connected via said packet data network, and a protocol converter in communication with the at least one second database via a packet data interface and with the network manager via a signalling interface, and operable to convert between a signalling protocol used on the signalling interface and a packet transmission protocol used on the packet data interface.

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to a mobile communications network which has access to an external packet DATA network such as the internet. 
     (2) Description of Related Art 
     There are currently a significant number of internet protocol (IP) service providers using fixed telephone networks. It would be desirable to extend these to using mobile networks. It is in principle possible to connect messages conveyed through a mobile communications network to the internet or other switched packet data network (PDN) using general packet radio services (GPRS), a standard which is a packet data transfer standard compatible with GSM. It is supported in some GSM networks through the use of GPRS support nodes (GSN). However, access to the internet or other packet data network in this way currently requires that a service provider provide a suitable gateway GPRS service node (GGSN) and a home location register (HLR) and subscriber database which communicates with it in a manner compatible with existing GSM signalling standards. Thus, a service provider would need to set up a home location register and subscriber database and gateway GPRS service node capable of utilising at least one of the appropriate signalling protocols used in the SS7 stack specified by GSM. This requires a significant investment on the part of the service provider and as such constitutes a deterrent for providing more open access to the internet using the mobile communication network. 
     U.S. Pat. No. 5,793,762 describes a system and method for providing Internet and data voice services to mobile subscribers. The system includes a Home Location Register (HLR), which is operative to store and provide subscription data and keep track of where at least one mobile terminal is registered in order to deliver calls thereto. 
     WO 98/27698 describes an arrangement for establishing a packet switched and a circuit switched connection between a first telecommunications system (NSS) and a second telecommunications system (WAN) comprising: a packet switched converter (PSDC), a circuit switched converter (CSDC) and a common data communications controller (CDCC) for establishing a connection between the converters (PSDC, CSDC). 
     EP 0 766 490 relates to an integrated data transfer system, the extensive basis of which is constituted by a general cellular radio system, and in which a radio local area network is used for communicating between data terminals in small areas with dense communications. In addition, the Internet is used for fast data transfer. The connection between networks is handled by a gateway computer, which in view of the cellular radio system operates like a Base Station Controller (BSC). 
     BRIEF SUMMARY OF THE INVENTION 
     According to the present invention there is provided a mobile communications network comprising: a network manager (MSC) for managing a plurality of mobile stations in the network; a first database (HLR) holding subscriber information for mobile station subscribers in the network and in communication with the network manager via a signalling interface over which information is conveyed using one of a plurality of signalling protocols; at least one second database (LHLR) for communication with a packet data network via a packet data interface over which information is conveyed using one of a plurality of packet transmission protocols, said second database holding subscriber information for subscribers connected via said packet data network; and a protocol converter in communication with the at least one second database via a packet data interface and with the network manager via a signalling interface, and operable to convert between a signalling protocol used on the signalling interface and a packet transmission protocol used on the packet data interface. 
     The first database can be a home location register as used in the GSM standard to hold subscriber information. The at least one second database can constitute a supplementary home location register for holding subscriber information relating to users connected via the packet data network. It is referred to herein as a “little HLR”. More than one of these “little HLRs” may be provided in a network. It can be implemented using software operating on commercial UNIX or NT servers for example, which is a much cheaper investment for new service providers than the investment in the more complex signalling protocols currently used in GSM. The provision of a separate, second database also provides a service provider with more control for managing his subscribers and services. 
     Thus, the service provider need provide only the second database, and, optionally a gateway for access to other supplementary services outside the mobile communications network connected to the second database via a packet data interface. The service provider can then be connected to the mobile networks through a roaming broker which provides the protocol converter in the form of an interworking unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention and to show how the same may be carried into effect reference will now be made by way of example to the accompanying drawings in which: 
         FIG. 1  is a schematic diagram of relevant components of the logical architecture of a mobile network; 
         FIG. 2  is a diagram of a signalling protocol stack; 
         FIG. 2   a  is a diagram illustrating use of a protocol stack; 
         FIG. 3  is a diagram of a data transmission protocol stack; 
         FIG. 4  illustrates modified components of a logical architecture for the network according to one embodiment of the invention; 
         FIG. 5  is a diagram illustrating operation of an interworking unit; and 
         FIG. 6  is a diagram illustrating one application of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates relevant components of a logical architecture for supporting a mobile communications network, in this case the standard set down for a global system for mobile communications, referred to herein as GSM. In addition to providing services for mobile phones, the GSM network is extended to provide other services, referred to herein as general packet radio services (GPRS). The logical architecture comprises a base station system  2  which incorporates base transceiver stations (BTS) and base station controllers (BSC) for controlling the base transceiver stations. The base transceiver stations themselves receive RF signals  4  from mobile stations  6 . The base station system  2  is connected to a network manager in the form of a mobile switching centre (MSC)  8  which controls the operations of the mobile communication network. The mobile switching centre  8  is associated with a visitor location register (VLR) which is a database containing information about mobile subscribers that visit the area governed by the mobile switching centre  8 . The mobile switching centre  8  communicates with the base station system  2  via an A interface  10 . The mobile switching centre  8  and its visitor location register are also in communication with a home location register (HLR)  12  via a D interface  14 . The home location register is a database that contains all the subscriber specific information of subscribers in the home public land mobile network (PLMN). The network provides support for GPRS services by incorporating a gateway GPRS support node  16  and a serving GPRS support node  18 . The gateway GPRS support node  16  communicates with the home location register  12  via a G c  interface  20 . The serving GPRS support node  18  communicates with the home location register  12  via a G r  interface  22 . The gateway GPRS support node  16  communicates with the serving GPRS support node  18  via a G n  interface  24 . The logical architecture components  2 ,  8 ,  12 ,  16  and  18  which have just been discussed can be considered to form part of a first public land mobile network PLMN 1 . The serving GPRS support node allows connection via a G p  interface  26  to a second public land mobile network PLMN 2 . The gateway GPRS support node  16  additionally allows access to a packet data network (PDN)  28  via a G i  interface  30 . 
     It will readily be appreciated that the physical implementation of the logical architecture components and the interfaces between them significantly affect how information can be transferred between the components. Data transfer protocols which are suited to one medium may not transfer easily to other mediums. In order to transfer information through the network as sufficiently and reliably as possible, a number of protocols are used across each interface according to a so-called protocol stack. Such a protocol stack is used for example to convey information between the mobile switching centre  8  and home location register  12  via the D interface  14 . This stack is illustrated in  FIG. 2  and is referred to as the SS7 stack according to the GSM standard. The protocol stack of  FIG. 2  includes a number of protocol layers as follows. 
     A mobile application part (MAP) layer is an application which generates a protocol to update location registers such as the visitor location register (VLR) and the home location register (HLR)  12 . 
     A transaction capabilities application part (TCAP) is a simple protocol that provides features for establishing a signalling dialogue between nodes when no speech path is required. 
     A signalling connection control part (SCCP) provides enhanced addressing and translation features that allow the transfer of signalling messages between two indirectly connected nodes when no speech connection is required. 
     The message transfer parts (MTP 2 , MTP 3 ) provide reliable message transfer between nodes in the network. 
     A first protocol layer L 1 , provides the basic signalling protocol for RF messages. 
     The use of a protocol stack is known in the art but is briefly described herein with reference to  FIG. 2   a . In  FIG. 2   a , each block PL denotes a protocol layer of the stack of  FIG. 2 . For the sake of simplification, the message transfer parts MTP 1 , MTP 2  have been combined in a single block and denoted only MTP. A first protocol stack has layers denoted with the suffix  1 , and a second protocol stack has layers denoted with the suffix  2 . Consider the example of a message issued by the mobile switching centre MSC  8  according to the MAP protocol, for example for updating a register in the home location register  12 . Consider that the first protocol stack belongs to the visitor location register VLR and the second protocol stack belongs to the home location register HLR. Depending on the nature of the D interface  14 , the message can be conveyed using one or more of the protocol layers of a protocol stack. Consider that all of the protocol layers of the stack are needed. The message will be conveyed from the MAP 1  layer to the TCAP 1  layer via protocol conversion and checking units  40 . These units  40  add the necessary information to the message to change the protocol, and checks for any errors. A similar unit (of course adapted to each protocol), lies between each of the protocol layer blocks. If all of the layers of the protocol stack are used, the message will finally be rendered according to the L 1  protocol and will be transferred using that protocol to the L 12  protocol layer of the home location register. The protocol will then be altered, in reverse, through the protocol layers up to the MAP 2  layer. It is not necessary to use all the protocol layers in a stack. It is quite feasible to consider, for example, a message conveyed between the MAP 1  and MAP 2  protocol layers, or indeed between any pair of protocol layers in the stacks. 
     It is not practical however to include in one protocol stack all of the possible protocols that may be required in a mobile communication network and to support a large number of ancillary services such as GPRS, PDN etc. Therefore, different interfaces provide different protocols.  FIG. 3  illustrates the protocol stack used to convey information between the gateway GPRS support node  16  and the serving GPRS support node  18  via the G n  interface  24 . This stack includes first and second message transfer layer protocols L 1 , L 2 , an internet protocol layer IP, a user datagram protocol UDP and a GPRS tunnelling protocol GTP. These protocols are used however in the same way as described above with reference to  FIG. 2   a.    
     It will be appreciated that if it is necessary, for example, to convey a message between the HLR  12  and the PDN  28  a number of steps are required. The message is sent across the G c  interface  20  from the home location register  12  using the SS7 signalling stack of  FIG. 2  to the gateway GPRS support node  16 . From there, it is transmitted via the G i  interface  30  using the data transmission protocol stack according to  FIG. 3 . Thus, some conversion is necessary. This is carried out by an interworking unit  32  which receives a message conveyed by the G c  interface  20  according to a first protocol of the SS7 stack and converts that protocol into one of the protocols of the stack of  FIG. 3 . 
     After that, the protocol layers of the data transmission stack of  FIG. 3  can be used as normal on the G i  interface  30 , and also the G n  interface  24 . 
     Information about subscribers to services accessible by the GGSN  16  and GSSN  18  is held in the home location register  12 . Thus, with the architecture of  FIG. 1 , a service provider wishing to use the facilities of a mobile communication network needs to provide not only a suitable gateway node with a data transmission protocol, but also, a home location register for managing those services. For these purposes, he is required to implement the SS7 stack of  FIG. 2 . This is expensive and can deter potential new service providers. 
     The logical architecture of  FIG. 4  overcomes this problem. In  FIG. 4 , like numerals denote like parts as in  FIG. 1  and parts which have not been modified are omitted from  FIG. 4  entirely for the sake of clarity. Thus, in respects other than those illustrated in  FIG. 4 , the logical architecture is the same as  FIG. 1 . 
     In addition to the architectural components illustrated in  FIG. 1 , there is a so-called little home location register (LHLR)  42 . This is provided to manage subscriber services which are accessed through the packet data network PDN  28  via gateway GPRS support node  16 , or directly via the interface  51 . The little home location register  42  communicates with the gateway GPRS support node  16  via a G c ′ interface  44 . It communicates with the serving GPRS support node  18  via a G r ′ interface  46 . These interfaces use the data transmission stack of  FIG. 3  instead of the SS7 stack used on the equivalent interfaces G c , G r  in  FIG. 1 . An interworking unit  48  is provided which communicates with the little home location register  42  via a D′ interface  50 . The D′ interface also uses the protocol stack of  FIG. 3 . The interworking unit  48  provides a facility to convert between any of the protocols in the protocol stack of  FIG. 3  to any of the protocols in the SS7 stack of  FIG. 2  to allow communication if necessary with the mobile switching centre  8  and its visitor location register. This is illustrated in  FIG. 5 . 
     The provision of a little home location register  42  which can communicate using protocols more suited to data packet transmission allows a number of different facilities to be provided as illustrated for example in  FIG. 6 . 
       FIG. 6  illustrates a service provider SP which provides a little home location register  42  and a gateway GPRS support node  16  connected to one another via an intranet connection  44 . The protocol stack of  FIG. 3  can be used to transmit data between the little home location register  42  and the GGSN  16  via the intranet  44 . In fact, the intranet provides the G c ′ interface. The little home location register  42  is connected to the public internet  54  via the interface  60  on which transmission is executed using the internet protocol IP. It also has another interface  60 ′ which likewise uses the internet protocol IP to an internet forming part of the GPRS services. This is also connected to the GGSN  16  via an interface  56  which uses the GPRS tunnelling protocol GTP. 
     A roaming broker  58  connects the GTP/internet services to the PLMN and provides the interworking unit (IWU)  48  for the necessary protocol conversions for messages from the PLMN to the little home location register  42 . 
     Thus, a subscriber can be connected to the PLMN through the public internet  54  and little home location register  42 . The connection can be entirely on the internet using the IP interfaces  60 ,  60 ′ or through the intranet  44  and GTP interface  56 . 
     More than one little home location register may be provided in a network having one home location register HLR and one interworking unit IWU.