Method of setting up an application initiated call to a mobile station within a CAMEL network, and a telecommunications system comprising a CAMEL network

1. A method of setting up a call connection to a mobile station operative to communicate with a Customised Application for Mobile Enhanced Logic CAMEL telecommunications network, the call being initiated by an Open Service Architecture, OSA application causing a message to be produced which indicates to the network that the mobile station is now available to make a ring back call connection, the network setting up the call connection in response to the message.

2. A method according to claim 1 , in which the message is a Completion of Calls to Busy Subscriber CCBS Remote User Free RUF message.

3. A method according to claim 1 or claim 2 , in which the network sets up the call connection using Completion of Calls to Busy Subscriber CCBS network-initiated mobile-originated NIMO procedures.

4. A method according to claim 3 , in the network comprising a home location register HLR of the mobile station and a visited mobile switching centre VMSC/visited location register VLR with which the mobile station is currently associated, the home location register HLR constructs the message, and instructs the visited mobile switching centre VMSC/visited location register VLR to make a Completion of Calls to Busy Subscriber CCBS Re-call so as to setup the call connection in response to the message.

5. A method according to claim 1 or claim 2 , in the network comprising a home location register HLR of the mobile station and a visited mobile switching centre VMSC/visited location register VLR with which the mobile station is currently associated, the home location register HLR constructs the message, and instructs the visited mobile switching centre VMSC/visited location register VLR to make a Completion of Calls to Busy Subscriber CCBS Re-call so as to setup the call connection in response to the message.

6. A method of controlling a call to a mobile station operative to communicate with a Customised Application for Mobile Enhanced Logic CAMEL telecommunications network comprising the method of setting up the call connection according to claim 1 , and the OSA application controlling the call connection after call connection setup.

7. A method according to claim 6 , in which the home location register HLR or visited mobile switching centre VMSC/visited location register VLR with which the mobile station is currently associated is provided with CAMEL subscription information CSI so as to enable said controlling the call connection after call connection setup.

8. A method according to claim 7 in which the home location register updates the visited mobile switching centre VMSC/visited location register VLR with CAMEL subscription information CSI, in the absence of which pseudo—CAMEL subscription information CSI is sent instead which is deleted upon the call connection being set up.

9. A method according to claim 7 or claim 8 , in which the visited mobile switching centre VMSC/visited location register VLR is operative to check the CAMEL subscription information CSI or pseudo—CAMEL subscription information CSI and if the information is found acceptable an initial detection point InitialDP is sent to a call control server including an identifier that the OSA application may have control over the call connection.

10. A method according to claim 9 , in which the visited mobile switching centre VMSC/visited location register VLR responds to the message by sending to the call control server an acknowledgement including an identifier field which matches that in the initial detection point, the server being operative to check whether the two identifiers match and if so notify the OSA application of its control of the call connection after call connection setup.

11. A wireless telecommunications system comprising a Customised Application for Mobile Enhanced Logic CAMEL telecommunications network, and a mobile station, the network being operative to set up a call connection to the mobile station, the call being initiated by an Open Service Architecture OSA application causing a message to be produced which indicates to the network that the mobile station is now available to make a ring back call connection, the network being operative to set up the call connection in response to the message.