Abstract:
The invention relates to methods and devices for supporting the sending of a message to a dual mode mobile station.

Description:
TECHNICAL FIELD  
       [0001]    The present invention relates to methods and devices for handling a call involving a mobile station adapted to co-operate with a first access network comprising a device operating according to a session initiation protocol and a second access network wherein the second access network is a cellular access network. 
       RELATED ART  
       [0002]    In recent years the percentage of household having a broadband connection at home was increasing. Today 11% of the households in Germany are equipped with a broadband connection (mainly ADSL). In Sweden the percentage is already 22% (50% ADSL, 50% other technologies). It is expected that these percentages will increase significantly over the next years. Many of these users will install private WLAN (Wireless Local Area Network)-access points to connect their PCs (Personal Computers), PDA (Personal Digital Assistants), mobile phones etc. to their fixed broadband connection. 
         [0003]    Furthermore, it is expected that the number of public WLAN-hot spots in Europe will increase from approx. 18.000 (2003) to 36.000 (2009). 
         [0004]    Parallel, to the increased number of broadband connections the users are starting to use IP (Internet Protocol) telephony over their WLAN-broadband connection via PCs and PDAs. In the next years mobile phone vendors will launch so-called GSM/WLAN dual mode phones (e.g. Nokia 2005). 
         [0005]    For these users of the GSM/WLAN dual mode phones it will be quite easy to originate calls via the SIP-client over the WLAN-radio interface towards other SIP-clients connected to the same network or even to the internet. 
         [0006]    Today several architectures are proposed how to integrate cellular networks with WLAN-access points. The main focus is the integration of the WLAN-access point towards the packet switching network. 
         [0007]    For example Mobile@home proposes an architecture where the WLAN-access point is connected via a broadband connection to the BSC. The disadvantage of this solution is that the same operator has to supply the cellular mobile network and the broadband connection. Furthermore, Mobile@home proposes a solution based on the ADSL (Asymmetric Digital Subscriber Line) technology. 
         [0008]    However none of the current solutions provides mechanisms and devices for handling a message service to a mobile station that is connected by a connection via a WLAN access network to a mobile station. 
         [0009]    Therefore it is object of the invention to provide methods and devices to overcome the shortcomings of the prior art. 
       SUMMARY 
       [0010]    This will be solved advantageously by the method of claim  1 , the database of claim  4 , and the system of claim  5 . Further advantageous embodiments can be derived from the dependent claims. 
         [0011]    The invention introduces a method for providing a mobile station with a message, wherein the mobile station is adapted to co-operate with a first access network comprising a device operating according to a session initiation protocol and a second access network wherein the second access network is a cellular access network. The method comprises the steps of receiving a request for sending the message to the mobile station, determining that the mobile station can be reached via the first access network, wherein the first access network does not support the message service, sending the message to a control node of a cellular telecommunications network, and the node sending the message towards the mobile station. 
         [0012]    In an embodiment of the invention, the step of sending comprises converting the message into at least one message that can be transmitted according to a Session Initiation Protocol, sending the message to the device operating according to a session initiation protocol, and the method comprises the additional steps of forwarding from the device the contents of the message to the mobile station. 
         [0013]    In an embodiment of the invention the step of sending is implemented by sending the message via the second application network. 
         [0014]    The invention further introduces a database for storing subscriber data for a telecommunications network comprising a first access network not supporting a message service and comprising a device operating according to a session initiation protocol and a second access network wherein the second access network is a cellular access network. The database is adapted to receive an indication that a mobile station can be reached via the first network, characterised by that the database is adapted to send an alert message to a message service support node for indicating that a message can be delivered. The database can be implemented for example by a home location register or a home subscriber server or a AAA server. 
         [0015]    The invention further introduces a system for telecommunications connected to a first access network reachable via a device operating according to a session initiation protocol and a second access network wherein the second access network is a cellular access network, a database for storing subscriber data, a service node for supporting a message service, a control node for performing call control functions and a function for converting signaling messages. The database is adapted to send an indication to the service node that a message can be sent towards the mobile station on reception of an indication that a mobile station is reachable via the first access network. 
         [0016]    In an embodiment of the invention, the first access network is one of a wireless local are network, a bluetooth network, a short range radio network, a fixed network, or an optical network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The following figures show: 
           [0018]      FIG. 1  depicts an architecture for enabling a mobile station to access a telecommunications network via a further access network, 
           [0019]      FIG. 1   a  depicts a registration of a dual mode mobile station with a SIP proxy, (state of the art) and the indicating of this to the telecommunications network, 
           [0020]      FIG. 2  depicts the provision of a message to a mobile station according to the invention, and 
           [0021]      FIG. 3  depicts the an alternative provision of a message to a mobile station according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    In the following the invention will be further described by means of examples and by means of figures. 
         [0023]    It should be noted that the WLAN access is just an exemplary embodiment and could be replaced by any other access technology as for example Bluetooth, optical connection, short range radio or fixed line connection. In particular access technology with lower costs on transmission resources like bandwidth than the GSM or WCDMA technology can be used advantageously for the further access. 
         [0024]    It should be further noted that for an implementation of the invented methods, the access point adapted to communicate over a radio, fixed or optical connection to mobile station, may be connected by any means to a domain operating according to a session initiation protocol and transmitting data according to an internet protocol. 
         [0025]    The short message service is just an example for messaging services like paging, multi media messages and alike. 
         [0026]      FIG. 1  depicts an architecture for enabling a mobile station to access a telecommunications network via a further access network, comprising an home location register  101 , a gateway mobile services switching centre, a combined mobile services switching centre/media gateway control function  103  which are connected to each other. In another embodiment of the invention the mobile services switching centre and the media gateway control function are not combined but just interconnected. The combined mobile services switching centre/media gateway control function  103  is further connected to an internet domain  104  comprising a first SIP (Session Initiation Protocol) proxy (proximity server)  105  and a second SIP proxy  106  that is connected to telephone  107  adapted to send signals according to SIP. The internet domain is connected via an ISP (Internet Service Provider)  108  and a DSLAM (Digital Subscriber Line Access Multiplexer)  109  to a local exchange  110  which is connected to a public switched telephony network  111 . The local exchange is further connected via a DSL (Digital Subscriber Line) modem  112  to a WLAN-access Point  113 . 
         [0027]    A mobile station  106  is connected via a WLAN radio connection to the WLAN Access Point and via a GSM or WCDMA radio connection to the mobile services switching centre/media gateway control function. 
         [0028]    According to the invention, the mobile station  116  can use the WLAN radio connection to register in the first SIP proxy  105 . The details of the registration will be explained in  FIG. 1   a.    FIG. 1   a  depicts a registration of the mode mobile station  116  with the first SIP proxy  105 . This is state of the art. To that end the mobile station  106  sends a SIP register message towards the SIP proxy  105  via the WLAN radio connection. After successful registration the SIP proxy returns a  200  OK message to the mobile station. After receiving this confirmation that the registration has been successful the mobile station sends an indication that it can be reached via the SIP proxy to the mobile services switching centre via the GSM or WCDMA connection by sending a location update message. The mobile services switching centre stores the indication in a visitor location register. It returns an accepted message to indicate the reception of the location update. 
         [0029]    In an embodiment of the invention the indication is stored in a home location register or a home subscriber server. 
         [0030]    The sending of the indication can be implemented in several ways. It can be sent for example in a USSD (Unstructured Supplementary Service Data) message or any other signaling means between mobile station and mobile services switching centre. In the preferred embodiment it is included in a location update message. Independent from the means used for transporting the information from mobile station to mobile services switching centre, the information can be sent as a simple indication, for example a flag, indicating that an alternative access technology is available. In that case one can always use the same predefined device for routing calls from the mobile services switching centre/media gateway control function to the mobile station. Such device can be for example an interrogating call session control function as defined in the 3GPP recommendation 29.163 version 6.2.0 of March 2004. If not always the same device is used a device must be identified. 
         [0031]    In a preferred embodiment of the invention the SIP proxy is identified by an identification of the mobile station. To that end, an identification of the mobile station, e.g. the MSISDN or the IMSI, is stored in a table or a database in association with an identification of the SIP proxy, conveniently this can be the address of the SIP proxy. In a further embodiment of the invention, the mobile station identification can be related to an operator and the operator identification can be stored in relation to the SIP proxy identification. 
         [0032]    Alternatively, a device can be identified for example by determining location information of the mobile station like a location area or geographical coordinates and using a mapping table that maps said location information to an address. A further way to address the mobile station is the use of an ENUM (tElephone NUmber Mapping) database as defined in IETF (Internet Engineering Task Force) RFC 3761. The ENUM database maps the telephone number, for example the IMSI (International Mobile Subscriber Identity) of the mobile station, to an IP address. A further way is the transmission of a location area identifier in the location update message. The location area identifier carries an identification of the SIP proxy or of an access point, for example an ESSID (Extended Services Set IDentification), a domain name or a WLAN location area identification. 
         [0033]      FIG. 2  depicts the architecture of  FIG. 1  from the WLAN access point  113  to the SIP proxy  105  as well as the further SIP proxy  106  and the SIP telephone  107 . Furthermore the cellular telecommunications network is depicted by means of a combined media gateway control function/mobile services switching centre  208 , a SMS (Short Message Service) service centre  207  and a home location register  206 . The mobile station  116  is currently registered with the SIP proxy  105 . The SIP server  105  sends an indication that the mobile station  116  can be reached via the first access network, a WLAN access network, to the home location register in a step  201 . The home location register  206  determines that the combined media gateway control function/mobile services switching centre  208  is serving the mobile station in a step  202 . The home location register stores the indicator and sends a message to the SMS service centre in a step  203  indicating that the mobile station can be reached via the combined media gateway control function/mobile services switching centre  208 . The combination of the media gateway control function and the mobile services switching centre is an implementation and not necessary for the invention. Both nodes could be implemented separated as well. The SMS service centre sends the short message to the combined media gateway control function/mobile services switching centre in a step  204 . The mobile services switching centre forwards the short message to the media gateway control function which converts it into at least one message that can be transmitted according to a SIP protocol and forwards this at least one message to the SIP proxy  105 . The SIP proxy  105  delivers the at least one message to the mobile station via the first access network in a step  206 . 
         [0034]    In an embodiment of the invention the protocol conversion is performed in the SIP server. 
         [0035]      FIG. 3  depicts an alternative provision of a message to a mobile station.  FIG. 3  shows the architecture of  FIG. 1  from the WLAN access point  113  to the SIP proxy  105  as well as the further SIP proxy  106  and the SIP telephone  107 . Furthermore the cellular telecommunications network is depicted by means of a combined media gateway control function/mobile services switching centre  308 , the SMS (Short Message Service) service centre  207  and the home location register  206 . The mobile station  116  is currently registered with the SIP proxy  105 . The SIP server  105  sends an indication that the mobile station  116  can be reached via the first access network, a WLAN access network, to the home location register in a step  201 . The home location register  206  determines that the combined media gateway control function/mobile services switching centre  208  is serving the mobile station in a step  202 . The home location register stores the indicator and sends a message to the SMS service centre in a step  203  indicating that the mobile station can be reached via the combined media gateway control function/mobile services switching centre  308 . The combination of the media gateway control function and the mobile services switching centre is an implementation and not necessary for the invention. Both nodes could be implemented separated as well, whereas for the depicted implementation the media gateway control function is redundant. The SMS service centre sends the short message to the combined media gateway control function/mobile services switching centre in a step  204 . The mobile services switching centre forwards the short message via the cellular telecommunications access network  115  to the mobile station. 
         [0036]    In a preferred embodiment of the invention, the mobile station comprises a first part operating according to at least one protocol used via the first access network, for example WLAN protocols and SIP, and a second part operating according at least one protocol used via the cellular access network. The mobile station can send a message originating in the first part via the first access network as a message that can be transmitted according to a SIP protocol. If the message is addressed to a terminal that does not operate according to a SIP protocol, the message is converted either in the SIP proxy or a media gateway control function. 
         [0037]    Accordingly, a message originating in the SIP telephone  107  can be transmitted as a message that can be transmitted according to a SIP to the first part of the mobile station.