Method for locating mobile terminals

Abstract

A method for locating mobile terminals is provided. First, information of a home Public Land Mobile Network (PLMN) of a target mobile terminal, the location of which is to be determined, is checked in response to a location service request from a client. Then, information of a visited PLMN, where the target mobile terminal is currently located, is checked based on the checked information of the home PLMN. The home PLMN calculates location assistance information of the visited PLMN using specific location information of the visited PLMN. The location assistance information is transferred to the target mobile terminal. This allows location information of a mobile terminal to be obtained irrespective of the area or communication network where the mobile terminal is located. It is thus possible to locate a mobile terminal in an area where no location assistance information is provided.

What is claimed is: 
     
       1. A home Public Land Mobile Network (PLMN) method for locating mobile terminals, comprising the steps of:
 a) receiving a request message of location service for a target terminal which is roaming; 
 b) checking information of a visited PLMN visited by the target terminal, in response to the request message of location service; 
 c) determining if the visited PLMN provides location assistance information using the checked information of the visited PLMN; 
 d) if the visited PLMN does not provide location assistance information, calculating by the home PLMN, using information corresponding to a cell ID of the target terminal in the visited PLMN, location assistance information for performing Network Assisted Global Positioning System (A-GPS) positioning of the target terminal; and 
 e) transferring the location assistance information to the target terminal. 
 
     
     
       2. The method according to  claim 1 , further comprising the step of:
 f) calculating, by the home PLMN, the location of the target terminal using a GPS pseudorange of the target terminal, wherein the GPS pseudorange is measured in the target terminal using the location assistance information. 
 
     
     
       3. The method according to  claim 1 , further comprising the step of:
 g) receiving, by the home PLMN, calculated location information from the target terminal, wherein the calculated location information is calculated using a GPS pseudorange measured by the target terminal and the GPS pseudorange is measured in the target terminal using the location assistance information. 
 
     
     
       4. The method according to  claim 1 , wherein step b) includes the step of receiving and checking an IP address of a Gateway GPRS Support Node (GGSN) of the visited PLMN of the target terminal from a server for storing registrant and roaming information of mobile terminals. 
     
     
       5. The method according to  claim 1 , wherein step d) includes the step of calculating GPS satellite orbit and geographical information of the visited PLMN visited by the target terminal, and then calculating valid location assistance information using the calculation result. 
     
     
       6. The method according to  claim 1 , wherein at step d), the home PLMN, including a database (DB) for allowing the home PLMN to obtain geographical information of each of a plurality of PLMNs using a cell ID of each of the PLMNs, detects geographical information of the visited PLMN from the database using the cell ID of the target terminal in the visited PLMN, and calculates location assistance information of the visited PLMN using the detected geographical information. 
     
     
       7. The method according to  claim 1 , wherein said step e) includes the step of transferring only location assistance information for acquiring an initial GPS signal, depending on available network resources or traffic states. 
     
     
       8. The method according to  claim 1 , wherein step e) includes the step of encapsulating and transmitting the location assistance information, IP information of the home PLMN and the target terminal, and a location information request instruction. 
     
     
       9. A home Public Land Mobile Network (PLMN) method for locating mobile terminals, comprising the steps of:
 a) receiving a request message of location service for a target terminal from a visited PLMN which the target terminal is roaming in, the request message including at least one a Cell ID; 
 b) checking information of the visited PLMN visited by the target terminal, which is roaming, in response to the request message of location service; 
 c) determining if the visited PLMN visited by the target terminal provides location assistance information; 
 d) if the visited PLMN doesn't provide location assistance information, receiving information corresponding to the cell ID of the target terminal from the visited PLMN at the home PLMN, and calculating by the home PLMN, using the information corresponding to the cell ID of the target terminal, the location assistance information for performing Network Assisted Global Positioning System (A-GPS) positioning of the target terminal; and 
 e) transferring the location assistance information to the target terminal. 
 
     
     
       10. The method according to  claim 9 , further comprising the steps of:
 f) receiving, by the visited PLMN, calculated location information from a home PLMN, wherein the calculated location information is calculated in the home PLMN using a GPS pseudorange measured by the target terminal and the GPS pseudorange is measured in the target terminal using the location assistance information; and 
 g) transferring the calculated location information to a client terminal or the target terminal. 
 
     
     
       11. The method according to  claim 9 , further comprising the steps of
 g) receiving, by the visited PLMN, calculated location information from the target terminal, wherein the calculated location information is calculated in the target terminal; and 
 h) transferring the calculated location information to a client terminal. 
 
     
     
       12. The method according to  claim 9 , wherein at step b), a Serving GPRS (General Packet Radio Service) Support Node (SGSN) of the visited PLMN receives and checks an IP address of a Gateway Mobile Location Center (GMLC) of a home PLMN from a Visitor Location Register (VLR). 
     
     
       13. The method according to  claim 9 , wherein step d) includes the step of calculating GPS satellite orbit and geographical information of the visited PLMN visited by the target terminal, and then calculating valid location assistance information using the calculation result. 
     
     
       14. The method according to  claim 9 , wherein at step d), a home PLMN, including a database (DB) for allowing the home PLMN to obtain geographical information of each of a plurality of PLMNs using a cell ID of each of the PLMNs, detects geographical information of the visited PLMN from the database using the cell ID of the visited PLMN, and calculates location assistance information of the visited PLMN using the detected geographical information. 
     
     
       15. The method according to  claim 9 , wherein said step e) includes the step of transferring location assistance information for acquiring an initial GPS signal, depending on available network resources or traffic states. 
     
     
       16. The method according to  claim 9 , wherein step e) includes the step of encapsulating and transmitting the location assistance information, IP information of a home PLMN and the target terminal, and a location information request instruction. 
     
     
       17. The method according to  claim 1 , wherein the location assistance information is transmitted to the target terminal through the visited PLMN. 
     
     
       18. The method according to  claim 1 , wherein the information corresponding to the cell ID of the target terminal in the visited PLMN, the information is at least one of a GPS satellite orbit and a geographical information of a corresponding cell where the target terminal is located. 
     
     
       19. The method according to  claim 1 , wherein in the step of receiving a request message of location service for a target terminal which is roaming, the home PLMN receives the request message from the target terminal. 
     
     
       20. The method according to  claim 19 , wherein the request message includes at least a Cell ID of the target terminal. 
     
     
       21. The method according to  claim 1 , further comprising the steps of:
 receiving routing information of the target terminal; and 
 requesting information of the visited PLMN from the visited PLMN, the information including an IP address of a Gateway GPRS Support Node (GGSN) of the visited PLMN of the target terminal. 
 
     
     
       22. The method according to  claim 1 , further comprising the steps of:
 receiving, by the home PLMN, the information corresponding to a cell ID of the target terminal from the visited PLMN. 
 
     
     
       23. The method according to  claim 9 , wherein the information corresponding to the cell ID of the target terminal in the visited PLMN, includes at least one of a GPS satellite orbit and a geographical information of a corresponding cell where the target terminal is located. 
     
     
       24. The method according to  claim 9 , further comprising the steps of:
 receiving routing information of the target terminal; and 
 requesting information of the visited PLMN from the visited PLMN, the information including an IP address of a Gateway GPRS Support Node (GGSN) of the visited PLMN of the target terminal. 
 
     
     
       25. A method for locating mobile terminals, the method comprising the steps of:
 receiving, by a home Mobile Location Center (MLC), a request message of a location service for a target terminal that is roaming;   determining if a visited MLC provides location assistance information;   transferring, by the home MLC, the location assistance information to the target terminal, wherein the location assistance information is received from the visited MLC or calculated using information corresponding to a cell IDentifier (ID), based on the determining;   calculating, by the home MLC, location information of the target terminal, based on location related information received from the target terminal, or receiving, by the home MLC, the location information of the target terminal, which is calculated at the target terminal based on the location assistance information, from the target terminal; and   transferring, by the home MLC, the location information to a client.   
     
     
       26. The method of claim 25, further comprising obtaining the location assistance information from approximate location information of the target terminal in the visited MLC visited by the target terminal.  
     
     
       27. The method of claim 25, wherein the location information is calculated using a Global Positioning System (GPS) pseudorange of the target terminal, and
 wherein the GPS pseudorange is measured in the target terminal using the location assistance information.    
     
     
       28. The method of claim 25, further comprising checking information of the visited MLC visited by the target terminal, in response to receiving the request message for the location service.  
     
     
       29. The method according to claim 28, wherein checking the information of the visited MLC comprises receiving and checking an Internet Protocol (IP) address of a Gateway General Packet Radio Service (GPRS) Support Node (GGSN) of the visited MLC of the target terminal from a server for storing registrant and roaming information of mobile terminals.  
     
     
       30. The method of claim 28, further comprising calculating, by the home MLC, the location assistance information for performing Network Assisted Global Positioning System (A-GPS) positioning of the target terminal using information corresponding to the cell ID of the target terminal in the visited MLC.  
     
     
       31. The method of claim 30, wherein the information corresponding to the cell ID of the target terminal in the visited MLC includes at least one of a GPS satellite orbit and a geographical information of a cell in which the target terminal is located.  
     
     
       32. The method of claim 30, wherein calculating the location assistance information comprises:
 calculating GPS satellite orbit and geographical information of the visited MLC; and   calculating valid location assistance information using the calculated GPS satellite orbit and geographical information.    
     
     
       33. The method of claim 25, further comprising:
 detecting geographical information of the visited MLC visited by the target terminal, from a database included in the home MLC, using the cell ID of the target terminal in the visited MLC; and   calculating the location assistance information of the visited MLC using the detected geographical information.    
     
     
       34. The method of claim 25, wherein transferrins the location assistance information to the target terminal comprises transferring only location assistance information for acquiring an initial GPS signal, depending on available network resources or traffic states.  
     
     
       35. The method of claim 25, wherein transferring the location assistance information to the target terminal comprises encapsulating and transmitting the location assistance information with Internet Protocol (IP) information of the home MLC and the target terminal, and a location information request instruction.  
     
     
       36. The method of claim 25, wherein the location assistance information is transmitted to the target terminal through the visited MLC.  
     
     
       37. The method of claim 25, wherein the request message includes the cell ID of the target terminal.  
     
     
       38. The method of claim 25, further comprising:
 receiving routing information of the target terminal; and   requesting information of the visited MLC visited by the target terminal, from the visited MLC,   wherein the information includes an Internet Protocol (IP) address of a Gateway General Packet Radio Service (GPRS) Support Node (GGSN) of the visited MLC of the target terminal.    
     
     
       39. The method of claim 38, further comprising receiving, by the home MLC, the information corresponding to the cell ID of the target terminal from the visited MLC.  
     
     
       40. A method for locating mobile terminals, comprising the steps of:
 receiving, by a home Mobile Location Center (MLC), a request message of a location service for a target terminal, from a visited MLC in which the target terminal is roaming, the request message including a cell IDentifier (ID);   determining if the visited MLC provides location assistance information;   transferring, by the home MLC, the location assistance information to the target terminal, wherein the location assistance information is received from the visited MLC or calculated using information corresponding to the cell ID, based on the determining;   calculating, by the home MLC, location information of the target terminal, based on location related information received from the target terminal, or receiving the location information of the target terminal, which is calculated at the target terminal based on the location assistance information, from the target terminal; and   transferring, by the home MLC, the location information to the target terminal or a client.   
     
     
       41. The method of claim 40, further comprising obtaining the location assistance information from approximate location information of the target terminal in the visited MLC.  
     
     
       42. The method of claim 40, wherein the location information is calculated using a Global Positioning System (GPS) pseudorange of the target terminal, and
 wherein the GPS pseudorange is measured in the target terminal using the location assistance information.    
     
     
       43. The method of claim 40, further comprising checking information of the visited MLC, in response to receiving the request message for the location service.  
     
     
       44. The method of claim 43, further comprising:
 receiving information corresponding to the cell ID of the target terminal from the visited MLC; and   calculating, by the home MLC, the location assistance information for performing Network Assisted Global Positioning System (A-GPS) positioning of the target terminal using the information corresponding to the cell ID of the target terminal.    
     
     
       45. The method of claim 44, wherein the information corresponding to the cell ID of the target terminal includes at least one of a GPS satellite orbit and a geographical information of a cell in which the target terminal is located.  
     
     
       46. The method of claim 44, wherein calculating the location assistance information comprises:
 calculating GPS satellite orbit and geographical information of the visited MLC; and   calculating valid location assistance information using the calculated GPS satellite orbit and geographical information.    
     
     
       47. The method of claim 44, further comprising:
 detecting geographical information of a visited MLC visited by the target terminal, from a database included in the home MLC, using the cell ID of the target terminal in the visited MLC; and   calculating the location assistance information of the visited MLC using the detected geographical information.    
     
     
       48. The method of claim 40, wherein transferring the location assistance information to the target terminal comprises transferring only location assistance information for acquiring an initial GPS signal, depending on available network resources or traffic states. 
     
     
       49. The method of claim 40, wherein transferring the location assistance information to the target terminal comprises encapsulating and transmitting the location assistance information with Internet Protocol (IP) information of the home MLC and the target terminal, and a location information request instruction.  
     
     
       50. The method of claim 40, further comprising:
 receiving routing information of the target terminal; and   requesting information of the visited MLC from the visited MLC,   wherein the information includes an Internet Protocol (IP) address of a Gateway General Packet Radio Service (GPRS) Support Node (GGSN) of the visited MLC of the target terminal.    
     
     
       51. A location server for locating mobile terminals, comprising:
 a transceiver for receiving a request message of a location service for a target terminal that is roaming;   a memory for storing location assistance information, wherein the location assistance information is received from a visited location server or calculated using a cell IDentifier (ID); and   a controller for exchanging at least one positioning message with the target terminal,   wherein the transceiver receives, from the target terminal, location information of the target terminal, which is calculated at the target terminal based on the location assistance information.   
     
     
       52. A location server for locating mobile terminals, comprising:
 a transceiver for receiving a request message of a location service for a target terminal that is roaming;   a memory for storing location assistance information, wherein the location assistance information is received from a visited location server or calculated based on a cell IDentifier (ID); and   a controller for exchanging at least one positioning message with the target terminal, and calculating location information of the target terminal based at least in part on the at least one positioning message.   
     
     
       53. A location server for locating mobile terminals, comprising:
 a transceiver for receiving a request message of a location service for a target terminal from a visited location server in which the target terminal is roaming, the request message including a cell IDentifier (ID);   a memory for storing location assistance information, wherein the location assistance information is received from the visited location server or calculated using the cell ID; and   a controller for exchanging at least one positioning message with the target terminal,   wherein the transceiver receives, from the target terminal, location information of the target terminal, which is calculated at the target terminal based on the location assistance information.   
     
     
       54. A location server for locating mobile terminals, comprising:
 a transceiver for receiving a request message of a location service for a target terminal from a visited location server in which the target terminal is roaming, the request message including a cell IDentifier (ID);   a memory for storing location assistance information, wherein the location assistance information is received from the visited location server or calculated using the cell ID; and   a controller for exchanging at least one positioning message with the target terminal, and calculating location information of the target terminal based at least in part on the at least one positioning message.