Method and arrangement for handling a mobile telephone subscriber administered in different mobile telephone networks with a common call number

• US 5,610,974 A
• Filed: 04/05/1995
• Issued: 03/11/1997
• Est. Priority Date: 04/05/1994
• Status: Expired

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lantto, Jorgen
• Primary Examiner(s): CUMMING, WILLIAM D
• Application Number:
  US08/417,023
• Time in Patent Office: 706 Days
• Field of Search: 340/825.44, 340/825.06, 340/825.31, 340/825.34, 379/59, 379/56, 379/57, 379/60, 379/62, 379/63, 370/18, 370/54, 370/95.1, 370/95.3, 380/43, 380/46, 380/49, 455/12.1, 455/13.1, 455/33.1, 455/54.1
• US Class Current: 455/433
• CPC Class Codes: H04W 8/12 between location registers or mobility servers

Abstract

A roaming arrangement enables roaming between different types of networks in a telecommunication system that includes a first standardized type of mobile network, a so-called home network, and a second standardized type of mobile network, a so-called guest network. A subscriber has an identity that is common for both the home network and the guest network. The roaming arrangement includes a signal handling arrangement, at least one home interface towards the home network, and at least one guest interface towards the guest net. A first signalling format between the arrangement and the home network is of the same type as a corresponding format in the home network. Also, a second signalling format between the arrangement and the guest network is of the same type as a corresponding format in the guest network.

Claims

1. A roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, the roaming arrangement comprising:

means for handling signals;

at least one home interface towards the home network, wherein the home interface is arranged to receive signals from the home network and to transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network;

at least one guest interface towards the guest network, wherein the guest interface is arranged to receive signals from the guest network and to transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guess network,

wherein the home network and the guest network each include a home register and a local switching center;

the signal handling means includes a roaming register which is connected to the home network via a first signalling interface in the home interface;

the first signalling interface is located between the home register in the home network and the roaming register, is also connected to the guest network via a second signalling interface in the guest interface, and is of a same type as a standardized interface between the home register and the local switching center in the home network; and

the second signalling interface is located between the local switching center in the guest network and the roaming register and is of a same type as a standardized interface between the local switching center and the home register in the guest network.

2. The roaming arrangement of claim 1, wherein the home network includes at least one first call switching center for receiving a call from a calling subscriber to the mobile telephone subscriber;

the signal handling means includes a roaming switching center which is connected to the home network via a third signalling interface in the home interface between the roaming switching center and the call switching center in the home network;

the roaming switching center is also connected to the guest network via a fourth signalling interface in the guest interface between the roaming switching center and the local switching center in the guest network;

the third signalling interface is of the same type as a standardized interface between a first call switching center and the local switching center in the home network; and

the fourth signalling interface is of the same type as a standardized interface between the local switching center and a second call switching center in the guest network.

30. The roaming arrangement of claim 1, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

31. The roaming arrangement of claim 2, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

3. A roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, the roaming arrangement comprising:

means for handling signals;

at least one home interface towards the home network, wherein the home interface is arranged to receive signals from the home network and to transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network;

at least one guest interface towards the guest network, wherein the guest interface is arranged to receive signals from the guest network and to transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network,

wherein the home network and the guest network each include a home register and a local switching center;

the home network also includes a guest register in which subscribers visiting the local switching center are registered;

the signal handling means includes a roaming register which is connected to the home network via a first signalling interface in the home interface and which is connected to the guest network via a second signalling interface in the guest interface;

the first signalling interface is located between the home register in the home network and the roaming register and is of a same type as a standardized interface between the home register and the guest register; and

the second signalling interface is located between the local switching center in the guest network and the roaming register and is of a same type as a standardized interface between the local switching center and the home register in the guest network.

4. The roaming arrangement of claim 3, wherein the home network includes at least one first call switching center for receiving a call from a calling subscriber to the mobile telephone subscriber;

the signal handling means includes a roaming switching center which is connected to the home network via a third signalling interface in the home interface between the roaming switching center and the call switching center in the home network;

the roaming switching center is also connected to the guest network via a fourth signalling interface in the guest interface between the roaming switching center and the local switching center in the guest network;

the third signalling interface is of a same type as a standardized interface between a first call switching center and the local switching center in the home network; and

the fourth signalling interface is of the same type as a standardized interface between the local switching center and a second call switching center in the guest network.

32. The roaming arrangement of claim 3, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

33. The roaming arrangement of claim 4, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

5. A roaming arrangement in a telecommunication system for handling a mobile telephone subscriber wherein the system include a home network that is a first standardized type of mobile telephone network and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, the roaming arrangement comprising:

means for handling signals,

at least one home interface towards the home network, wherein the home interface is arranged to receive signals from the home network and to transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network;

at least one guest interface towards the guest network, wherein the guest interface is arranged to receive signals from the guest network and to transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network,

wherein the home network and the guest network each include a home register and a local switching center;

the guest network also includes a guest register in which subscribers visiting the local switching center are registered;

the signal handling means includes a roaming register which is connected to the home network via a first signalling interface in the home interface and which is connected to the guest network via a second signalling interface in the guest interface;

the first signalling interface is located between the home register in the home network and the roaming register and is of a same type as a standardized interface between the home register and the local switching center in the home network; and

the second signalling interface is located between the guest register in the guest network and the roaming register and is of a same type as a standardized interface between the guest register and the home register in the guest network.

6. The roaming arrangement of claim 5, wherein the home network includes at least one first call switching center for receiving a call from a calling subscriber to the mobile telephone subscriber;

the signal handling means includes a roaming switching center which is connected to the home network via a third signalling interface in the home interface between the roaming switching center and the call switching center in the home network;

the roaming switching center is also connected to the guest network via a fourth signalling interface in the guest interface between the roaming switching center and the local switching center in the guest network;

the third signalling interface is of a same type as a standardized interface between a first call switching center and the local switching center in the home network; and

the fourth signalling interface is of a same type as a standardized interface between the local switching center and a second call switching center in the guest network.

34. The roaming arrangement of claim 5, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

35. The roaming arrangement of claim 6, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

7. A roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, the roaming arrangement comprising:

means for handling signals;

at least one home interface towards the home network, wherein the home interface is arranged to receive signals from the home network and to transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network;

at least one guest interface towards the guest network, wherein the guest interface is arranged to receive signals from the guest network and to transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network,

wherein the home network and the guest network each include a home register, a local switching center, and a guest register in which subscribers visiting the local switching center are registered;

the signal handling means includes a roaming register which is connected to the home network via a first signalling interface in the home interface and which is connected to the guest network via a second signalling interface in the guest interface;

the first signalling interface is located between the home register in the home network and the roaming register and is of a same type as a standardized interface between the home register and the guest register; and

the second signalling interface is located between the local switching center in the guest network and the roaming register and is of a same type as a standardized interface between the guest register and the home register in the guest network.

8. The roaming arrangement of claim 7, wherein the home network includes at least one first call switching center for receiving a call from a calling subscriber to the mobile telephone subscriber;

the signal handling means includes a roaming switching center which is connected to the home network via a third signalling interface in the home interface between the roaming switching center and the call switching center in the home network;

the roaming switching center is also connected to the guest network via a fourth signalling interface in the guest interface between the roaming switching center and the local switching center in the guest network;

the third signalling interface is of a same type as a standardized interface between a first call switching center and the local switching center in the home network; and

the fourth signalling interface is of a same type as a standardized interface between the local switching center and a second call switching center in the guest network.

36. The roaming arrangement of claim 7, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

37. The roaming arrangement of claim 8, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

9. A roaming arrangement relating to a telecommunications system for handling a mobile telephone subscriber, wherein the telecommunications system includes a home network that is a first standardized type of mobile telephone network and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, the roaming arrangement comprising:

a first means for handling signals;

a second means for handling signals;

at least one home interface towards the home network, wherein the home interface is adapted to receive signals from the home network and to transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network; and

at least one guest interface towards the guest network, wherein the guest interface is adapted to receive signals from the guest network and to transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network,

wherein the home network and the guest network each include a home register and a local switching center;

the first signal handling means includes a first roaming register which is connected to the home network via a first signalling interface in the home interface;

the first signalling interface is located between the home register in the home network and the first roaming register, is also connected to the guest network via a second roaming register includes in the second signal handling means and via a second signalling interface in the guest interface, and is of a same type as a standardized interface between the home register and the local switching center in the home network; and

the second signalling interface is located between the local switching center in the guest network and the second roaming register and is of a same type as a standardized interface between the local switching center and the home register in the guest network.

10. The roaming arrangement of claims 9, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

29. The roaming arrangement of claim 9, wherein

the home network includes at least one first call switching center for receiving a call from a calling subscriber to the mobile telephone subscriber;

the first signal handling means includes a first roaming switching center which is connected to the home network via a third siggnalling interface in the home interface between the roaming switching center and the call switching center in the home network;

the first roaming switching center is also connected to the guest network via a second roaming switching center included in the second signal handling means and via a fourth signalling interface in the guest interface between the second roaming switching center and the local switching center in the guest network;

the third signalling interface is of a same type as a standardized interface between a first call switching center and the local switching center in the home network; and

the fourth signalling interface is of a same type as a standardized interface between the local switching center and a second call switching center in the guest network.

38. The roam arrangement of claim 29, wherein at least one of the home network and the guest network includes at least one satellite-based air interface.

11. A method, relating to a telecommunications system, of handling a mobile telephone subscriber having a call number which is common to both a home network that is a first standardized type of mobile telephone network and a guest network that is a second standardized type of mobile telephone network;

wherein the home network includes a home register in which the mobile telephone subscriber is registered permanently as being domestic in the home network, the guest network includes a local switching center for handling signalling to and from mobile units that are located in a cell area handled by the local switching center, the telecommunications system includes a roaming arrangement which includes a roaming register in which the mobile telephone subscriber is permanently registered as a conceivable guest in the guest network, and the roaming register is connected to the local switching center in the guest network and also to the home register in the home network;

the method comprising the steps of;

activating, by the mobile telephone subscriber, a mobile unit located in the guest network in the cell area of the local switching center;

sending, from the mobile unit to the local switching center, an updating request which includes an identity of the mobile telephone subscriber;

establishing, in the local switching center in the guest network, that the mobile telephone subscriber is permanently registered in the roaming register based on the identity of the mobile telephone subscriber;

checking an authorization of the mobile telephone subscriber as a guest in the guest network;

accepting the authorization of the mobile telephone subscriber as a guest in the guest network;

sending, from the local switching center to the roaming register, an initiation message which includes information indicating that the mobile telephone subscriber is found in the local switching center;

updating the roaming register with a new position of the mobile telephone subscriber, the new position being the local switching center in the guest network;

sending, from the roaming register to the home register in the home network, an updating message which includes information indicating that the mobile telephone subscriber is found in the roaming register; and

updating the home register in the home network with subscriber-relevant information.

12. The method of claim 11, the method further comprising the steps of:

sending, from the local switching center to the roaming register, a request for information that is required to check subscriber authorization; and

sending, from the roaming register to the local switching center, an information response which contains the information that is required to check subscriber authorization.

13. The method of claim 11, further comprising the step of collecting, from the roaming arrangement, a roaming number to the home register in the home network.

14. The method of claim 11, further comprising the step of collecting, from the local switching center in the guest network, a roaming number to the roaming arrangement.

15. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the telecommunications system includes a home network that is a first standardized type of mobile telephone network and that includes a call switching center which is connected to a home register and to the roaming arrangement, and at least one guest network that is a second standardized type of mobile telephone network, wherein the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes a roaming switching center which is connected to a roaming register, a first means for handling signals, a second means for handling signals, at least one home interface that is arranged to receive and transmit signals having a format that is the same as a signal format that occurs in the home network from and to the home network, and at least one guest interface that is arranged to receive and transmit signals having a format that is the same as a signal format that occurs in the guest network from and to the guest network, the method comprising the steps of:

calling, by a calling subscriber from a public switched telephone network unit in the telecommunications system, the mobile telephone subscriber, wherein the calling step includes the step of sending a call signal from the public switched telephone network unit to the call switching center in the home network;

sending, from the call switching center to the home register, a first query seeking a location of the mobile telephone subscriber;

sending, from the home register to the call switching center, a first response which includes a first address to the roaming switching center;

forwarding the call from the call switching center to the roaming switching center based on a first routing message which includes the first address;

sending, from the roaming switching center to the roaming register, a second query seeking the location of the mobile telephone subscriber;

sending, from the roaming register to the roaming switching center, a second response which includes a second address to a local switching center in the guest network;

forwarding the call from the roaming switching center to the local switching center based on a second routing message which includes the second address; and

finalizing the call from the public switched telephone network unit to the mobile telephone subscriber by establishing a connection between the local switching center and the mobile unit.

16. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the telecommunications system includes a home network that is a first standardized type of mobile telephone network, wherein a home register in the home network includes information relating to supplementary services that are available to the mobile telephone subscriber, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes roaming register, a first means for handling signals, a second means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receives signal from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, from the mobile unit to the roaming register via a local switching center in the guest network, a first handling request which includes information indicating how the mobile telephone subscriber wishes to handle a supplementary service;

transforming the first handling request to a second handling request and sending the second handling request from the roaming register to the home register in the home network; and

handling the supplementary service in the home register in the home network in accordance with the information.

17. The method of claim 16, further comprising the steps of:

sending, from the home register in the home network to the roaming register, a first handling acknowledgement which acknowledges handling of the supplementary service in accordance with the information; and

transforming the first handling acknowledgement to a second handling acknowledgement and sending the second acknowledgement from the roaming register to the mobile unit via the local switching center.

18. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the telecommunications system includes a home network that is a first standardized type of mobile telephone network, wherein a home register in the home network and a local switching center include information relating to supplementary services that are available to the mobile telephone subscriber, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes roaming register, a first means for handling signals, a second means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, from the home register in the home network to the roaming register, a first change message indicating that a change of supplementary service has taken place;

transforming the first change message to a second change message and sending the second change message from the roaming register to the local switching center in the guest network;

noting the supplementary service change in the local switching center in the guest network;

sending, to the roaming register from the local switching center in the guest network, a first change acknowledgement which acknowledges that the change has been implemented; and

transforming the first change acknowledgement message to a second change acknowledgement message and sending the second change acknowledgement message from the roaming register to the home register in the home network.

19. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the telecommunications system includes a home network that is a first standardized type of mobile telephone network, wherein a home register in the home network and a local switching center include information concerning supplementary services that are available to the mobile telephone subscriber, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes roaming register, a first means for handling signals, a second means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, to the roaming register from the home register in the home network, a first error message indicating that an error has occurred in the home register in the home network and that the home register lacks information relating to a position of the mobile telephone subscriber;

transforming the first error message to a second error message and sending the second error message from the roaming register to the local switching center in the guest network; and

noting, in the local switching center, a need for information concerning the position of the mobile telephone subscriber.

20. The method of claim 19, further comprising the steps of:

sending, to the roaming register from the local switching center in the guest network, a first error acknowledgement which confirms that the error message has been received; and

transforming the first error acknowledgement to a second error acknowledgement and sending the second error acknowledgement from the roaming register to the home register in the home network.

21. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the telecommunications system includes a home network that is a first standardized type of mobile telephone network, wherein the home network includes a local switching center which handles signalling to and from mobile units that are located in a cell area handled by the local switching center, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes roaming register, a first means for handling signals, a second means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, from the home register in the home network to the roaming register, a first deactivation message indicating that the mobile telephone subscriber is no longer present in the guest network;

updating the roaming register to indicate that the mobile telephone subscriber is no longer present in the guest network;

transforming the first deactivation message to a second deactivation message and sending the second deactivation message from the roaming register to the local switching center in the guest network;

deactivating data relating to the mobile telephone subscriber in the local switching center;

sending a first deactivation acknowledgement from the local switching center to the roaming register; and

transforming the first deactivation acknowledgement to a second deactivation acknowledgement and sending the second deactivation acknowledgement from the roaming register to the home register in the home network.

22. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network and that includes a call switching center which is connected to a home register in the home network and to the roaming arrangement, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes a roaming switching center which is connected to the roaming register, means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

calling, by a calling subscriber from a public switched telephone network unit in the telecommunications system, the mobile telephone subscriber, wherein the calling step includes the step of sending a call signal from the public switched telephone network unit to the call switching center in the home network;

sending, from the call switching center to the home register, a first query seeking a location of the mobile telephone subscriber;

sending, from the home register to the call switching center, a first response which includes a first address to the roaming switching center;

forwarding the call from the call switching center to the roaming switching center based on a first routing message which includes the first address;

sending, from the roaming switching center to the roaming register, a second query seeking the location of the mobile telephone subscriber;

sending, from the roaming register to the roaming switching center, a second response which includes a second address to a local switching center in the guest network;

forwarding the call from the roaming switching center to the local switching center based on a second routing message which includes the second address; and

finalizing the call from the public switched telephone network unit to the mobile telephone subscriber by establishing a connection between the local switching center and the mobile unit.

23. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network, wherein a home register in the home network includes information relating to supplementary services that are available to the mobile telephone subscriber, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes a roaming switching center which is connected to the roaming register, means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, from the mobile unit to the roaming register via a local switching center in the guest network, a first handling request which includes information indicating how the mobile telephone subscriber wishes to handle a supplementary service;

transforming the first handling request to a second handling request and sending the second handling request from the roaming register to the home register in the home network; and

handling the supplementary service in the home register in the home network in accordance with the information.

24. The method of claim 23, further comprising the steps of:

sending, from the home register in the home network to the roaming register, a first handling acknowledgement which acknowledges handling of the supplementary service in accordance with the information; and

transforming the first handling acknowledgement to a second handling acknowledgement and sending the second acknowledgement from the roaming register to the mobile unit via the local switching center.

25. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network, wherein a home register in the home network and a local switching center include information relating to supplementary services that are available to the mobile telephone subscriber, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes a roaming switching center which is connected to the roaming register, means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, from the home register in the home network to the roaming register, a first change message indicating that a change of supplementary service has taken place;

transforming the first change message to a second change message and sending the second change message from the roaming register to the local switching center in the guest network;

noting the supplementary service change in the local switching center in the guest network;

sending, to the roaming register from the local switching center in the guest network, a first change acknowledgement which acknowledges that the change has been implemented; and

transforming the first change acknowledgement message to a second change acknowledgement message and sending the second change acknowledgement message from the roaming register to the home register in the home network.

26. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network, wherein a home register in the home network and a local switching center include information concerning supplementary services that are available to the mobile telephone subscriber, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes a roaming switching center which is connected to the roaming register, means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, to the roaming register from the home register in the home network, a first error message indicating that an error has occurred in the home register in the home network and that the home register lacks information relating to a position of the mobile telephone subscriber;

transforming the first error message to a second error message and sending the second error message from the roaming register to the local switching center in the guest network; and

noting, in the local switching center, a need for information concerning the position of the mobile telephone subscriber.

27. The method of claim 26, further comprising the steps of:

sending, to the roaming register from the local switching center in the guest network, a first error acknowledgement which confirms that the error message has been received; and

transforming the first error acknowledgement to a second error acknowledgement and sending the second error acknowledgement from the roaming register to the home register in the home network.

28. A method relating to a roaming arrangement in a telecommunications system for handling a mobile telephone subscriber, wherein the system includes a home network that is a first standardized type of mobile telephone network and that includes a local switching center which handles signalling to and from mobile units that are located in a cell area handled by the local switching center, and at least one guest network that is a second standardized type of mobile telephone network, and the mobile telephone subscriber has a call number which is common to both the home network and the guest network, and wherein the roaming arrangement includes a roaming switching center which is connected to the roaming register, means for handling signals, at least one home interface that is arranged to receive signals from and transmit signals to the home network, the signals having a format that is the same as a signal format that occurs in the home network, and at least one guest interface that is arranged to receive signals from and transmit signals to the guest network, the signals having a format that is the same as a signal format that occurs in the guest network, the method comprising the steps of:

sending, from the home register in the home network to the roaming register, a first deactivation message indicating that the mobile telephone subscriber is no longer present in the guest network;

updating the roaming register to indicate that the mobile telephone subscriber is no longer present in the guest network;

transforming the first deactivation message to a second deactivation message and sending the second deactivation message from the roaming register to the local switching center in the guest network;

deactivating data relating to the mobile telephone subscriber in the local switching center;

sending a first deactivation acknowledgement from the local switching center to the roaming register; and

transforming the first deactivation acknowledgement to a second deactivation acknowledgement and sending the second deactivation acknowledgement from the roaming register to the home register in the home network.