초록 ▼

In one of multiple mobile communication networks, a serving node responsible for locating mobile terminals is responsive to a registration request from a mobile terminal for storing the serving node identity in a home location database to which the mobile terminal is subscribed. In response to a loc

In one of multiple mobile communication networks, a serving node responsible for locating mobile terminals is responsive to a registration request from a mobile terminal for storing the serving node identity in a home location database to which the mobile terminal is subscribed. In response to a location request message from a client terminal requesting the location of a target mobile terminal, a serving node identity is retrieved from the home location database of the target mobile terminal. The serving node identity represents the current location of the target mobile terminal. If the current location area is within the coverage area of location-based service provided by the client terminal, the location request message is forwarded to a serving node identified by the retrieved serving node identity. Otherwise, an error message is transmitted to the client terminal to indicate that the target mobile terminal is roaming outside of the coverage area.

대표청구항 ▼

What is claimed is: 1. A location system for a client terminal which provides a location-based service over a coverage area, comprising: at least one mobile communication network for storing information indicating an area in which a mobile terminal is located and determining location of said mobile

What is claimed is: 1. A location system for a client terminal which provides a location-based service over a coverage area, comprising: at least one mobile communication network for storing information indicating an area in which a mobile terminal is located and determining location of said mobile terminal in response to a location request message; first means, responsive to a location request message from said client terminal requesting location information of a target mobile terminal, for retrieving area indicating information from said network corresponding to identity of said target mobile terminal to determine the area in which said target mobile terminal is located; and second means for forwarding the location request message to said network to determine the location of said target mobile terminal if said determined area is within said coverage area and transmitting an error message to said client terminal if said determined area is outside of said coverage area. 2. The location system of claim 1, wherein said second means further comprises means for making a first decision when said location request message is an immediate location request and said location area is within said coverage area, a second decision when said location request message is an immediate location request and said location area is outside of said coverage area, or a third decision when said location request is a deferred location request, and forwarding said location request message to said location network in response to either of said first and third decisions and transmitting said error message to said client terminal in response to said second decision. 3. The location system of claim 1, wherein said at least one mobile communication network comprises: a home location database to which said target mobile terminal is subscribed; and a serving node, responsive to a registration request message from said target mobile terminal, storing identity of the serving node in the home location database of said mobile terminal as said area indicating information, wherein said first means is arranged to retrieve a serving node identity from the home location database corresponding to the target mobile terminal in response to receipt of said location request message from said client terminal, and wherein said second means is arranged to forward said location request message to a serving node identified by the retrieved serving node identity if said determined area is within said coverage area and transmit said error message to said client terminal if said determined area is outside of said coverage area. 4. The location system of claim 3, wherein said second means further comprises means for making a first decision when said location request message is an immediate location request and said location area is within said coverage area, a second decision when said location request message is an immediate location request and said location area is outside of said coverage area, or a third decision when said location request is a deferred location request, and forwarding said location request message to said serving node in response to either of said first and third decisions and transmitting said error message to said client terminal in response to said second decision. 5. The location system of claim 3, wherein said second means further includes storage means for storing a plurality of coverage information representing coverage areas according to a plurality of service types and identities of client terminals, retrieving one of the stored coverage information corresponding to a service type and an identity of the client terminal contained in said message from the client terminal, and requesting said location information or transmitting said error message if said location area is, respectively, within or outside of the coverage area represented by the retrieved coverage information. 6. The location system of claim 3, wherein said first means is provided in a requesting gateway to which said client terminal is connected, and further includes storage means for storing a plurality of coverage information representing coverage areas according to a plurality of service types and identities of client terminals and retrieving one of said stored coverage information corresponding to a service type and an identity of the client terminal contained in said message from the client terminal, said first means being arranged to transmit the location request message to said visited gateway containing the retrieved coverage information and said serving node identity retrieved from said database, and wherein said second means is provided in a visited gateway to which said target mobile terminal is visiting, and is arranged to request said location information or transmit said error message if a location area represented by the transmitted serving node identity is within or outside, respectively, of a coverage area represented by the transmitted coverage information. 7. The location system of claim 6, wherein said first means in said requesting gateway comprises: means for detecting a country code in the serving node identity retrieved from said database and retrieving said one stored coverage information from said storage means corresponding to the detected country code and to said service type and said identity of the client terminal and forwarding the location request message to said visited gateway containing the retrieved coverage information and the serving node identifier retrieved from said database, wherein said second means in said visited gateway comprises: a mapping memory for mapping a plurality of information representing a plurality of location areas to a plurality of serving node identities and retrieving one of said location area information from the mapping memory corresponding to the serving node identity contained in the location request message from said requesting gateway; and means for requesting the location information of the target mobile terminal from said serving node if the location area represented by the information retrieved from said mapping memory is within said coverage area represented by said coverage information from said requesting gateway and transmitting an error message to said client terminal via the requesting gateway if said location area is outside of said coverage area. 8. The location system of claim 3, wherein said location request message from said client terminal contains coverage information indicating said coverage area and wherein said second means is arranged to request said location information or transmit said error message if the location area is within or outside, respectively, of the coverage area represented by said coverage information. 9. The location system of claim 3, wherein said first means further comprises a cache memory for mapping a plurality of serving node identities retrieved from said database to identities of mobile terminals and retrieving one of the serving node identities from the cache memory corresponding to identity of the target mobile terminal contained in the location request message from said client terminal. 10. The location system of claim 3, wherein said coverage area is represented by a list of assigned codes, and said serving node identity is represented by a code, and wherein said second means is arranged to request said location information if the code of the serving node identity is contained in said list of assigned codes and transmit said error message if said code of the serving node identity is not contained in said list. 11. The location system of claim 10, wherein said list of assigned codes is a list of country codes. 12. The location system of claim 5, wherein said first means further comprises update means, responsive to a request message from said client terminal, for updating said storage means when a change occurs in the coverage area of the location-based service provided by the client terminal. 13. The location system of claim 5, wherein said first means comprises a mapping memory for mapping a plurality of information representing a plurality of location areas to a plurality of serving node identities and retrieving one of the location area information from said mapping memory corresponding to the retrieved serving node identity, and wherein said second means comprises means for comparing the location area represented by the retrieved location area information and said coverage area to request said location information from said serving node or transmit said error message depending on a result of said comparison. 14. The location system of claim 13, wherein said first means is provided in a first gateway, further comprising a location area memory provided in a second gateway for storing location area information representing a plurality of location areas covered by said serving node and update means (44, 46) for updating said mapping memory of the first gateway according to a change in said location area information stored in said location area memory of the second gateway. 15. The location system of claim 13, wherein said mapping memory is provided in a home gateway and said location area memory and said updating means are provided in a visited gateway. 16. The location system of claim 3, wherein said first and second means are provided in a home gateway. 17. The location system of claim 16, wherein a coverage area memory is provided in a requesting gateway for storing a plurality of coverage area information representing coverage areas of location-based services according to service types and identities of client terminals, and means for forwarding the location request message from said client terminal to said home gateway, wherein said home gateway comprises: a cache memory; and means, responsive to said location request message, for making a search through said cache memory for coverage information corresponding to a service type and identity of the client terminal for retrieving said serving node identifier from said database if the corresponding coverage information is detected, and requesting said requesting gateway to transmit corresponding coverage information of coverage area memory if said corresponding coverage information is not detected in said cache memory and storing the transmitted coverage information in said cache memory. 18. The location system of claim 3, wherein said first and second means are provided in a requesting gateway. 19. The location system of claim 3, wherein said first means is provided in a requesting gateway and said second means is provided in a visited gateway. 20. The location system of claim 3, wherein said first and second means are provided in a dual-function gateway which operates a requesting gateway and a home gateway. 21. The location system of claim 3, wherein said first and second means are provided in a dual-function gateway which operates as a home gateway and a visited gateway. 22. The location system of claim 3, wherein said first and second means are provided in a triple-function gateway which operates as a requesting gateway, a home gateway and a visited gateway. 23. The location system of claim 1, further comprising, a plurality of databases associated respectively with said networks, each database being a home location of the mobile terminals of the associated network and storing identity of a gateway of the associated network, wherein said at least one mobile communication network comprises a plurality of serving nodes, each serving node registering identity of a mobile terminal in response to a registration request message therefrom and storing identity of the serving node in the home location database of said mobile terminal, said serving node being responsible for producing location information of the registered mobile terminal, said serving node identity representing a location area of said mobile terminal, wherein said first means and said second means are provided in a first gateway which comprises a cache memory, wherein the first means is responsive to a location request message from said client terminal requesting location information of a target mobile terminal for retrieving a serving node identity and identity of a second gateway from the home location database of the target mobile terminal if said identity of the second gateway is not stored in said cache memory, and storing the retrieved identity of the second gateway in said cache memory, requesting the location information of the target mobile terminal from a serving node identified by the retrieved serving node identity if a location area represented by the serving node identity is within said coverage area and transmitting an error message to said client terminal if the location area is outside of said coverage area, or forwarding the location request message to the second gateway if said identity of the second gateway is stored in said cache memory, said forwarded location request message containing coverage information representing said coverage area. 24. The location system of claim 23, wherein said second means is arranged to: if said identity of the second gateway is not stored in said cache memory, request said location information from said serving node if the location request message is a deferred location request, or if said message is an immediate location request and said location area is within said coverage area, and if said identity of the second gateway is stored in said cache memory, forward said location request message containing coverage information representing said coverage area to said second gateway if said location request message is a deferred location request, wherein said fourth means is arranged to: request said location information from said serving node if the location request message from the first gateway is a deferred location request, or if said message is an immediate location request and said location area is within said coverage area represented by the coverage information transmitted from said first gateway. 25. A gateway for serving a client terminal which provides a location-based service to mobile terminals over a coverage area through at least one mobile communication network which stores information indicating an area in which a mobile terminal is located and determines the location of said mobile terminal in response to a location request message, comprising: first means, responsive to a location request message from said client terminal requesting location information of a target mobile terminal, for retrieving area indicating information from said network corresponding to identity of said target mobile terminal to determine the area in which said target mobile terminal is located; and second means for forwarding the location request message to said at least one network to determine the location of said target mobile terminal if said determined area of the target mobile terminal is within said coverage area and transmitting an error message to said client terminal if said determined area of the target mobile terminal is outside of said coverage area. 26. The gateway of claim 25, wherein said second means comprises means for making a first decision when said location request message is an immediate location request and said location area is within said coverage area, a second decision when said location request message is an immediate location request and said location area is outside of said coverage area, or a third decision when said location request is a deferred location request, and forwarding said location request message to said at least one network in response to either of said first and third decisions and transmitting said error message to said client terminal in response to said second decision. 27. The gateway of claim 25, wherein said at least one mobile communication network comprises, a home location database to which said target mobile terminal is subscribed, and a serving node, responsive to a registration request message from said target mobile terminal, storing identity of the serving node in the home location database of said mobile terminal as said area indicating information, wherein said first means is arranged to retrieve a serving node identity from the home location database of said target mobile terminal in response to receipt of said location request message from said client terminal, and wherein said second means is arranged to forward said location request message to a serving node identified by the retrieved serving node identity if said area is within said coverage area and transmit said error message to said client terminal if said area is outside of said coverage area. 28. The gateway of claim 27, wherein said second means comprises means for making a first decision when said location request message is an immediate location request and said location area is within said coverage area, a second decision when said location request message is an immediate location request and said location area is outside of said coverage area, or a third decision when said location request is a deferred location request, and forwarding said location request message to said serving node in response to either of said first and third decisions and transmitting said error message to said client terminal in response to said second decision. 29. The gateway of claim 27, wherein said second means further comprises storage means for storing a plurality of coverage information representing coverage areas according to a plurality of service types and identities of client terminals, retrieving one of the stored coverage information corresponding to a service type and identity of the client terminal contained in said message from the client terminal, and performing the requesting of said location information or the transmitting of said error message if said location area is within or outside, respectively, of the coverage area represented by the retrieved coverage information. 30. The gateway of claim 27, wherein said location request message from said client terminal contains coverage information indicating said coverage area and wherein said second means is arranged to request said location information or transmit said error message if the location area is within or outside, respectively, of the coverage area represented by said coverage information. 31. The gateway of claim 27, wherein said first means further comprises a cache memory system for mapping a plurality of serving node identities retrieved from said database to identities of mobile terminals and retrieving one of the serving node identities corresponding to identity of the target mobile terminal contained in the location request message from said client terminal. 32. The gateway of claim 28, wherein said coverage area is represented by a list of assigned codes, and said serving node identity is represented by a code, and wherein said second means is arranged to request said location information if the code of the serving node identity is contained in said list of assigned codes and transmit said error message if said code of the serving node identity is not contained in said list. 33. The gateway of claim 32, wherein said list of assigned codes is a list of country codes. 34. The gateway of claim 28, wherein said first means comprises a mapping memory for mapping a plurality of information representing a plurality of location areas to a plurality of serving node identities and for retrieving one of the location area information from said mapping memory corresponding to the retrieved serving node identity, and wherein said second means comprises means for comparing the location area represented by the retrieved location area information and said coverage area to request said location information from said serving node or transmit said error message depending on a result of said comparison. 35. The gateway of claim 30, wherein said first means further comprises update means, responsive to a request message from said client terminal, for updating said storage means when a change occurs in the coverage area of the location-based service provided by the client terminal. 36. A method of locating a mobile terminal when a location request message is received from a client terminal which provides location-based service to said mobile terminal when the mobile terminal is located within the coverage area of said service, comprising: a) responsive to a location request message from said client terminal requesting location information of a target mobile terminal, determining an area in which said target mobile terminal is located; and b) determining location of said target mobile terminal if said determined area is within said coverage area and transmitting an error message to said client terminal if said determined area is outside of said coverage area. 37. The method of claim 36, wherein said mobile terminal is connected to one of a plurality of mobile communication networks, each of the networks comprising a home location database to which said mobile terminal is subscribed and a serving node responsive to a registration request message from said target mobile terminal for storing identity of the serving node in the home location database of said mobile terminal as said area indicating information, wherein step (a) comprises the step of retrieving a serving node identity from said home location database corresponding to said target mobile terminal in response to receipt of said location request message from said client terminal, said serving node representing said area in which said target mobile terminal is located, and wherein step (b) comprises the step of forwarding said location request message to a serving node identified by the retrieved serving node identity if an area represented by the serving node identity is within said coverage area, and transmitting said error message to said client terminal if the area is outside of said coverage area. 38. The method of claim 37, wherein step (a) further comprises the steps of: a1) determining whether said location request message is an immediate location request or a deferred location request; a2) if said location request message is an immediate location request, performing step (b); and a3) if said location request message is a deferred location request, requesting the location information of the target mobile terminal from a serving node identified by the retrieved serving node identity. 39. The method of claim 37, wherein said location request message contains coverage information representing a coverage area of said location-based service, and wherein step (a) comprises: a1) storing a plurality of coverage information in a memory of a first gateway corresponding to a plurality of service types and identities of client terminals; a2) making a search through a cache memory of a second gateway for coverage information corresponding to a service type and identity of the client terminal contained in the received location request message; a3) if said corresponding coverage information is not detected in said cache memory, requesting the coverage information from the first gateway and storing the coverage information in said cache memory. 40. The method of claim 37, wherein step (a) is performed in a first gateway and step (b) is performed in a second gateway (2C), and wherein step (a) further comprises the steps of: a1) storing a plurality of coverage information in a storage means of a first gateway corresponding to a plurality of service types and identities of client terminals; a2) detecting a country code in the serving node identity retrieved from said home location database and retrieving one of coverage information from said storage means corresponding to the detected country code and to said service type and said identity of the client terminal; and a3) forwarding the location request message from said first gateway to said second gateway containing the retrieved coverage information and the serving node identifier retrieved from said database, wherein step (b) comprises: b1) mapping a plurality of location area information representing a plurality of location areas in a mapping memory to a plurality of serving node identities; b2) retrieving one of said location area information from the mapping memory corresponding to the serving node identity contained in the location request message forwarded from said first gateway as said location area to determine whether the location area is within or outside of the coverage information contained in said message forwarded from said first gateway; and b3) requesting said location information terminal from said serving node or transmitting said error message to said client terminal, depending on whether said location area is within or outside of said coverage area. 41. The method of claim 40, wherein step (a) further comprises the step of updating said storage means in response to a request message from said client terminal when a change occurs in the coverage area of the location-based service provided by the client terminal. 42. The method of claim 37, wherein step (a) comprises the step of: a1) making a search through a cache memory for a serving node identity corresponding to identity of said target mobile terminal; and a2) if said corresponding serving node identity is not detected; retrieving the serving node identifier from said home location database and storing the retrieved serving node identifier in said cache memory corresponding to the identity of said target mobile terminal. 43. The method of claim 37, wherein said coverage area is represented by a list of assigned codes, and said serving node identity is represented by a code, and wherein step (b) comprises the steps of requesting said location information from said serving node if the code of the serving node identity is contained in said list of assigned codes and transmitting said error message if said code of the serving node identity is not contained in said list. 44. The method of claim 43, wherein said list of assigned codes is a list of country codes. 45. The method of claim 37, wherein step (b) comprises the steps of: b1) mapping a plurality of information representing a plurality of location areas to a plurality of serving node identities in a mapping memory; b2) retrieving one of the location area information from said mapping memory as said location area corresponding to the serving node identity retrieved from said home location database; and b3) requesting said location information terminal from said serving node or transmitting said error message to said client terminal, depending on whether said location area is within or outside of said coverage area. 46. The method of claim 45, wherein step (b) is performed in a first gateway, further comprising the steps of: in a second gateway, storing location area information representing a plurality of location areas covered by said serving node in a location area memory; and requesting said first gateway to update said mapping memory according to a change in said location area information stored in said location area memory. 47. The method of claim 37, wherein said home location database stores identity of a gateway of the associated network and wherein steps (a) and (b) are performed in a first gateway, and wherein step (a) comprises: a1) in said first gateway, making a search through a first cache memory for identity of a second gateway; and a2) if said identity of the second gateway is not stored in said first cache memory, retrieving said serving node identity and identity of the second gateway from the home location database corresponding to the target mobile terminal and storing the retrieved identity of the second gateway in said first cache memory, further comprising the steps of: c) if said identity of the second gateway is stored in said first cache memory, forwarding the location request message from said first gateway to the second gateway, said forwarded message containing coverage information representing said coverage area; d) in said second gateway, responsive to said location request message from said first gateway, making a search through a second cache memory for a serving node identity corresponding to identity of said target mobile terminal; e) if said serving node identity is stored in said second cache memory, retrieving the same from said second cache memory and if said serving node identity is not stored in said second cache memory, retrieving said serving node identity from said home location database corresponding to the target mobile terminal and storing the retrieved serving node identity in said second cache memory; and f) requesting the location information of the target mobile terminal from a serving node identified by the retrieved serving node identity if a location area represented by the serving node identity retrieved by step (e) is within a coverage area represented by the coverage information contained in said location request message from the first gateway and transmitting an error message to said client terminal via said first gateway if the location area is outside of said coverage area. 48. The method of claim 47, wherein step (a) further comprises the steps of: a3) determining whether said location request message is an immediate location request or a deferred location request; a4) if said location request message is an immediate location request, performing step (b); and a5) if said location request message is a deferred location request, requesting the location information of the target mobile terminal from said serving node, wherein step (c) further comprises: c1) if said identity of the second gateway is stored in said first cache memory, determining, in said first gateway, whether said location request message is an immediate location request or a deferred location request; c2) forwarding the location request message from said first gateway to the second gateway containing coverage information representing said coverage area if said location request message is an immediate location request, and not containing said coverage information if said location request message is a deferred location request, wherein step (e) further comprises the steps of: e1) determining, in said second gateway, whether said location request message from the first gateway is an immediate location request or a deferred location request; e2) if said location request message is an immediate location request, performing step (f); and e3) said location request message is a deferred location request, requesting the location information of the target mobile terminal from said serving node. 49. A computer-readable medium encoded with a computer program for locating a mobile terminal when a location request message is received from a client terminal which provides location-based service to said mobile terminal when the mobile terminal is located within the coverage area of said service, said program comprising code means adapted to perform, when said program is run on a data processing system, the steps of: a) responsive to a location request message from said client terminal requesting location information of a target mobile terminal, determining an area in which said target mobile terminal is located; and b) determining location of said target mobile terminal if said determined area is within said coverage area and transmitting an error message to said client terminal if said determined area is outside of said coverage area. 50. The computer-readable medium of claim 49, wherein said mobile terminal is connected to one of a plurality of mobile communication networks, each of the networks comprising a home location database to which said mobile terminal is subscribed and a serving node responsive to a registration request message from said target mobile terminal for storing identity of the serving node in the home location database of said mobile terminal as said area indicating information, wherein step (a) comprises the step of retrieving a serving node identity from said home location database corresponding to said target mobile terminal in response to receipt of said location request message from said client terminal, said serving node representing said area in which said target mobile terminal is located, and wherein step (b) comprises the step of forwarding said location request message to a serving node identified by the retrieved serving node identity if an area represented by the serving node identity is within said coverage area, and transmitting said error message to said client terminal if the area is outside of said coverage area. 51. The computer-readable medium of claim 50, wherein step (a) further comprises the steps of: a1) determining whether said location request message is an immediate location request or a deferred location request; a2) if said location request message is an immediate location request, performing step (b); and a3) if said location request message is a deferred location request, requesting the location information of the target mobile terminal from a serving node identified by the retrieved serving node identity. 52. The computer-readable medium of claim 50, wherein said location request message contains coverage information representing a coverage area of said location-based service, and wherein step (a) comprises: a1) storing a plurality of coverage information in a memory of a first gateway corresponding to a plurality of service types and identities of client terminals; a2) making a search through a cache memory of a second gateway for coverage information corresponding to a service type and identity of the client terminal contained in the received location request message; a3) if said corresponding coverage information is not detected in said cache memory, requesting the coverage information from the first gateway (2A) and storing the coverage information in said cache memory. 53. The computer-readable medium of claim 50, wherein step (a) is performed in a first gateway and step (b) is performed in a second gateway, and wherein step (a) further comprises the steps of: a1) storing a plurality of coverage information in a storage means of a first gateway corresponding to a plurality of service types and identities of client terminals; a2) detecting a country code in the serving node identity retrieved from said home location database and retrieving one of coverage information from said storage means (23) corresponding to the detected country code and to said service type and said identity of the client terminal; and a3) forwarding the location request message from said first gateway to said second gateway containing the retrieved coverage information and the serving node identifier retrieved from said database, wherein step (b) comprises: b1) mapping a plurality of location area information representing a plurality of location areas in a mapping memory to a plurality of serving node identities; b2) retrieving one of said location area information from the mapping memory corresponding to the serving node identity contained in the location request message forwarded from said first gateway as said location area to determine whether the location area is within or outside of the coverage information contained in said message forwarded from said first gateway; and b3) requesting said location information terminal from said serving node or transmitting said error message to said client terminal, depending on whether said location area is within or outside of said coverage area. 54. The computer-readable medium of claim 53, wherein step (a) further comprises the step of updating said storage means in response to a request message from said client terminal when a change occurs in the coverage area of the location-based service provided by the client terminal. 55. The computer-readable medium of claim 50, wherein step (a) comprises the step of: a1) making a search through a cache memory for a serving node identity corresponding to identity of said target mobile terminal; and a2) if said corresponding serving node identity is not detected, retrieving the serving node identifier from said home location database and storing the retrieved serving node identifier in said cache memory corresponding to the identity of said target mobile terminal. 56. The computer-readable medium of claim 50, wherein said coverage area is represented by a list of assigned codes, and said serving node identity is represented by a code, and wherein step (b) comprises the steps of requesting said location information from said serving node if the code of the serving node identity is contained in said list of assigned codes and transmitting said error message if said code of the serving node identity is not contained in said list. 57. The computer-readable medium of claim 56, wherein said list of assigned codes is a list of country codes. 58. The computer-readable medium of claim 50, wherein step (b) comprises the steps of: b1) mapping a plurality of information representing a plurality of location areas to a plurality of serving node identities in a mapping memory; b2) retrieving one of the location area information from said mapping memory as said location area corresponding to the serving node identity retrieved from said home location database; and b3) requesting said location information terminal from said serving node or transmitting said error message to said client terminal, depending on whether said location area is within or outside of said coverage area. 59. The computer-readable medium of claim 58, wherein step (b) is performed in a first gateway, further comprising the steps of: in a second gateway, storing location area information representing a plurality of location areas covered by said serving node in a location area memory; and requesting said first gateway to update said mapping memory according to a change in said location area information stored in said location area memory. 60. The computer-readable medium of claim 50, wherein said home location database stores identity of a gateway of the associated network and wherein steps (a) and (b) are performed in a first gateway, and wherein step (a) comprises: a1) in said first gateway, making a search through a first cache memory for identity of a second gateway; and a2) if said identity of the second gateway is not stored in said first cache memory, retrieving said serving node identity and identity of the second gateway from the home location database corresponding to the target mobile terminal and storing the retrieved identity of the second gateway in said first cache memory, further comprising the steps of: c) if said identity of the second gateway is stored in said first cache memory, forwarding the location request message from said first gateway to the second gateway, said forwarded message containing coverage information representing said coverage area; d) in said second gateway, responsive to said location request message from said first gateway, making a search through a second cache memory for a serving node identity corresponding to identity of said target mobile terminal; e) if said serving node identity is stored in said second cache memory, retrieving the same from said second cache memory and if said serving node identity is not stored in said second cache memory, retrieving said serving node identity from said home location database corresponding to the target mobile terminal and storing the retrieved serving node identity in said second cache memory; and f) requesting the location information of the target mobile terminal from a serving node identified by the retrieved serving node identity if a location area represented by the serving node identity retrieved by step (e) is within a coverage area represented by the coverage information contained in said location request message from the first gateway and transmitting an error message to said client terminal via said first gateway if the location area is outside of said coverage area. 61. The computer-readable medium of claim 60, wherein step (a) further comprises the steps of: a3) determining whether said location request message is an immediate location request or a deferred location request; a4) if said location request message is an immediate location request, performing step (b); and a5) if said location request message is a deferred location request, requesting the location information of the target mobile terminal from said serving node, wherein step (c) further comprises: c1) if said identity of the second gateway is stored in said first cache memory, determining, in said first gateway, whether said location request message is an immediate location request or a deferred location request; c2) forwarding the location request message from said first gateway to the second gateway containing coverage information representing said coverage area if said location request message is an immediate location request, and not containing said coverage information if said location request message is a deferred location request, wherein step (e) further comprises the steps of: e1) determining, in said second gateway, whether said location request message from the first gateway is an immediate location request or a deferred location request; e2) if said location request message is an immediate location request, performing step (f); and e3) said location request message is a deferred location request, requesting the location information of the target mobile terminal from said serving node.