Abstract:
A positioning apparatus and method of a mobile terminal using a positioning server independently constructed on a network. The positioning apparatus includes a positioning server, independently constructed on a network, for collecting and storing/managing assistant data that includes orbit information and correction information of a satellite, and providing the assistant data or position information using the assistant data in response to an external request. The positioning server provides the position information of the terminal subject to positioning in response to the request for the position information of the terminal subject to positioning created from at least one network among a plurality of networks that share the positioning server. Accordingly, an accurate positioning result can be obtained with a cost for implementation of the positioning system reduced.

Description:
PRIORITY  
       [0001]     This application claims priority to an application entitled “Positioning Apparatus of Mobile Terminal Using Positioning Server Independently Constructed on Network and Method Thereof” filed in the Korean Industrial Property Office on Apr. 21, 2004 and assigned Serial No. 2004-27639, the contents of which are hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to a positioning apparatus of a mobile terminal using a positioning server independently constructed on a network and a method thereof, and more particularly to a positioning apparatus and method of a mobile terminal using a positioning server independently constructed on a network, such that the positioning of a roaming mobile terminal using an SUPL (Secure User Plane Location) using an IP (Internet Protocol)-based network is performed. Additionally, the present invention is applicable to a positioning service on a control plane in addition to a positioning service on a user plane.  
         [0004]     2. Description of the Related Art  
         [0005]     As mobile terminals become more lightweight and small-sized, users&#39; abilities to carry and use their mobile terminals have increased. Additionally, under the environment of a global mobile communication system, many users intend to receive application services (for example, traffic and living information) using position information of the mobile terminals. Accordingly, in some countries or mobile communication network territories (for example, territories of Korean mobile communication networks such as SK Telecom, KTF, or Japanese and European mobile communication networks such as NTT DoCoMo, Sprint PCS, KDDI, or Vodafone), mobile terminal position information acquisition systems using such mobile terminals have already been commercialized.  
         [0006]     In order to provide the application services using position information, as described above, a process of positioning a mobile terminal should precede. That is, the application services using position information should be provided based on geographical position information of the mobile terminal, which is obtained in the process of positioning the mobile terminal.  
         [0007]      FIG. 1  schematically illustrates a conventional mobile communication system. In particular,  FIG. 1  illustrates a GSM (Global System for Mobile communication) or UMTS (Universal Mobile Telecommunication System) mobile communication system.  
         [0008]     Referring to  FIG. 1 , the UMTS mobile communication system includes a CN (Core Network)  110 , a plurality of RNSs (Radio Network Subsystems)  120  and  130 , and a UE (User Equipment)  150 . The CN  110  manages information of the UE  150 , and performs mobility management, session management, and call management. As such, the RNS  120  or  130  includes an RNC (Radio Network Controller) and a plurality of base stations (i.e., node Bs). For example, the RNS  120  includes an RNC  121 , a node B  123 , and a node B  125 , and the RNS  130  includes an RNC  131 , a node B  133 , and a node B  135 .  
         [0009]     The RNCs  121  and  131  can be classified as a serving RNC (SRNC), a drift RNC (DRNC), or a controlling RNC (CRNC) according to their operation. That is, the RNC that manages information of UEs that belong to the corresponding RNC and controls data transmission between UEs and the CN  110  through an interface lu is called an SRNC. The RNC that relays data transmission between the UE belonging to another RNC and the RNC to which the UE belongs (for example, an SRNC) is called a DRNC. The RNC that controls the respective base stations (i.e., node Bs) is called a CRNC.  
         [0010]     In  FIG. 1 , if the RNC  121  manages the information of the UE  150 , it operates as the SRNC of the UE  150 . If the UE  150  moves and the UE  150  and the RNC  121  transmit and receive data through the RNC  131 , the RNC  131  operates as the DRNC of the UE  150 . The RNC  121  that controls the base station (i.e., node B)  125 , which is communicating with the UE  150 , becomes the CRNC of the base station  125 . The information and data of the UE  150  is transmitted to the CN  110  through the RNC  121  that is the SRNC of the UE  150 .  
         [0011]     In the mobile communication network as described above, diverse positioning techniques for positioning the UE have been used, and three representative techniques will be described herein below.  
         [0012]     A first method performs the positioning of the UE in the unit of a cell using information of a cell that is the nearest cell to the UE or that manages the UE. A second method is a network-based positioning method for calculating the strength of a signal using a measurement signal between the node B and UE or a time of arrival (TOA) or a time difference of arrival (TDOA), which is obtained from the transfer time of radio waves, and positioning the UE by applying a triangular surveying method to the TOA or TDOA. A third method for positioning the UE uses a GPS (Global Positioning System) developed by the United States Department of Defense. By supplementing and applying the GPS-technology among the positioning method using the GPS to a mobile communication system, a network-assisted GPS (network-AGPS) has been proposed.  
         [0013]     Conventionally, if a location service client (LCS client) outside a network requests the position of a specified UE, a preparatory process for performing the positioning of the UE is performed, a signal required for the positioning is measured, and the position of the UE is calculated according to the measured signal. More specifically, in the preparatory process, a privacy indicator such as a privacy limit of the UE is examined, resources of the network are allocated, and a positioning technique is selected according to a QoS (Quality of Service) requested by an LCS client and the performance of the UE and the network.  
         [0014]     Additionally, the position measurement process is performed between a UTRAN (Universal Terrestrial Random Access Network) and the UE, such that the signal required for the position measurement is acquired according to the positioning technique selected in the preparatory process, and then the position of the UE is calculated. In this case, the UE should be an individual UE for which the MSISDN (Mobile Subscriber ISDN Number) or IMSI (International Mobile Subscriber Identity) is already known.  
         [0015]     The position measurement process described above is frequently performed if the UE deviates from a home gateway mobile location center (GMLC) at which the UE itself is registered in the CN and is located at another GMLC, or if the positioning service is requested by an external LCS client or the UE itself. In this case, the GMLC manages position information of UEs located in PLMN (Public Land Mobile Network). A PLMN is a geographically or logically separable mobile communication network, and at least one GMLC may exist in one PLMN.  
         [0016]      FIG. 2  is a flowchart illustrating a conventional method of positioning a mobile terminal. In particular,  FIG. 2  illustrates the positioning process if the external LCS client (hereinafter referred to as a ‘client’)  160  requests the position of the UE_A  155 .  
         [0017]     Referring to  FIG. 2 , the client  160  requests the location service (LCS) for the UE, of which the client  160  wants to know the position, to a connected GMLC  111  in step S 11 . That is, the client  160  requests the position information of the UE_A  155 . Because the GMLC  111  requests the position of the UE_A  155 , it is represented as a ‘requesting GMLC’ in  FIG. 2 .  
         [0018]     The requesting GMLC  111  requests the home PLMN information of the UE_A  155  from an HLR/HSS (Home Location Register/Home Subscriber Server)  115  in step S 13 , and receives the home PLMN information from the HLR/HSS  115  in step S 15 . The HLR/HSS  115  is a server that stores registrants information and roaming information of the stored UEs, and responds to the request of the requesting GMLC  111  using the stored registrants information of the UEs. That is, the HLR/HSS provides the home PLMN information of the UE_A  155  to the requesting GMLC  111  in step S 15 .  
         [0019]     The requesting GMLC  11  that has received the home PLMN information of the UE_A  155  at step S 15  requests the information about the PLMN in which the UE_A  155  is located from the home GMLC  113  of the UE_A  155  using the home PLMN information in step S 17 . The home GMLC  113  performs a privacy authentication process in step S 19 , receives visited PLMN information of the UE_A  155  from the HLR/HSS  115  in steps S 21  and S 23 , and requests the position information of the UE_A  155  from the GMLC  117  of the PLMN that the UE_A  155  is visiting, using the visited PLMN information in step S 25 . Because the GMLC  117  is the GMLC of the PLMN that the UE_A  155  is visiting, it is called a ‘visited GMLC’.  
         [0020]     The visited GMLC  117  in the PLMN that the UE_A  155  is visiting, an MSC/SGSN (Mobile-services Switching Center/serving GPRS (General Packet Radio Service) Support Node)  119 , a RAN (Radio Access Network), and the UE_A  155  calculate the position of the UE_A  155 .  
         [0021]     Typically, in the mobile communication network, a positioning method such as a cell identification technique, a TDOA technique, an A-GPS technique, etc., is used as described above. Accordingly, the PLMN that the UE_A  155  is visiting can measure the position of the UE_A  155  using any one of the three methods.  
         [0022]     Meanwhile, the measurement of the position performed by the above-described methods may be classified into two methods according to the burden of network resources or the subject of position calculation. That is, the position measurement method may be classified into a UE-based method for calculating the position of the UE itself, using pseudo-range information and positioning-assisted information, and a UE-assisted method for obtaining pseudo-range information using a GPS satellite signal acquisition assistant data (for example, A-GPS assistant data) and then transferring the pseudo-range information to the corresponding RNC that manages the LCS service of the UE for the network&#39;s calculation of the position of the UE.  
         [0023]     In the process illustrated  FIG. 2 , the UE_A position information request transferred to a visited GMLC  17  of the UE_A  155  is transmitted to the RAN  170  through the MSC/SGSN  119 . If the corresponding RNC sends the A-GPS assistant data of the UE_A  155  to the UE_A  155  and the UE_A  155  calculates the position of the UE_A  155  itself, the position measurement method is UE-based. However, if the UE_A  155  sends the GPS pseudo-range information obtained by the UE_A  155  to the RNC and the network calculates the position of the UE_A  155 , the position measurement method is UE-assisted.  
         [0024]     If the position of the UE_A  155  is calculated by one of the UE-based and UE-assisted methods in step S 27 , the visited GMLC  117  transfers its result (i.e., the position information of the UE_A) to the home GMLC  113 . The home GMLC  113  performs the authentication process again at step S 31 , and then transfers the position information of the UE_A  155  transferred from the visited GMLC  117  to the client  160  through the requesting GMLC  111  in steps S 33  and S 35 .  
         [0025]      FIG. 3  is a block diagram schematically illustrating a conventional network for performing the positioning of a mobile terminal. Referring to  FIG. 3 , in order to provide the mobile terminal positioning service, the network should include a positioning service permission module and a position calculation service module. For example, in order to perform the positioning of a terminal A (not illustrated) in a state in which the terminal A deviates from a home network  210  and is roaming to a visited network  220 , the home network  210  and the visited network  220  should include a positioning service permission modules  211  and  221 , and position calculation service modules  213  and  223 , respectively. The positioning service permission modules  211  and  221  (for example, LMUs) perform the authentication of the mobile terminal subject to positioning and a privacy protection function, and support data transmitted between HLR and VLR in order to perform the authentication and privacy protection function. Further, the position calculation service modules  213  and  223  (for example, PDE (Position Determination Entity) perform an assistant data generation related to the position calculation and a calculation process.  
         [0026]     Accordingly, the home network  210  that has received the request for the position information of the terminal A authenticates the position information request and the privacy protection function of the terminal A. If it is possible to respond to the position information request, the home network  210  requests the position information of the terminal A from the position calculation service module  223  of the visited network  220  using the position calculation service module  213 , and then calculates the position of the terminal A after receiving the response to the position information request.  
         [0027]     However, the conventional method of positioning the mobile terminal as described above, has the drawbacks in that if there is no position calculation system (for example, LMU (Location Measurement Unit), or PDE) that is additionally provided according to mobile communication service providers in the network, it cannot provide the positioning service according to the request of the external LCS client or mobile terminal.  
         [0028]     Consequently, if the network that is not provided with the position calculation system receives the positioning service request from the mobile terminal, it must respond with a failure to the request or use the position calculation system provided another network by accessing the network that can prove the positioning service.  
         [0029]     However, in using the position calculation system provided in another network that can provide the positioning service, the network that can provide the positioning service may reject the use permission of the position calculation system or may exclusively use the positioning system.  
         [0030]     Additionally, when a home network performs the positioning of a mobile terminal that deviates from the home network and is located in another network, the accuracy of assistant data to be transferred to the terminal may deteriorate. This causes the accuracy of the positioning to deteriorate if the positioning is performed using the PDE.  
       SUMMARY OF THE INVENTION  
       [0031]     Accordingly, the present invention has been designed to solve the above and other problems occurring in the prior art, and an object of the present invention is to provide a positioning apparatus of a mobile terminal and a method thereof, which obtain an accurate positioning result with a reduced cost for implementation of a positioning system.  
         [0032]     Another object of the present invention is to provide a positioning apparatus and method of a mobile terminal for positioning the mobile terminal by sharing a positioning server independently implemented on a network with other networks.  
         [0033]     Another object of the present invention is to provide a positioning apparatus and method of a mobile terminal that can separate a positioning service permission module and a position calculation service module that are required for the positioning of the mobile terminal from each other and perform the positioning of the mobile terminal using the separated modules.  
         [0034]     In order to accomplish the above and other objects, there is provided a positioning apparatus of a mobile terminal. The apparatus includes a positioning server, independently constructed on a network, for collecting, storing, and managing assistant data that includes orbit information and correction information of a satellite, and providing the assistant data or position information using the assistant data in response to an external request. The positioning server provides the position information of the terminal subject to positioning in response to the request for the position information of the terminal subject to positioning created from at least one network among a plurality of networks that share the positioning server.  
         [0035]     Additionally, there is provided a positioning method of a mobile terminal using a positioning server independently constructed on a network. The method includes the steps of receiving a request for position information of a specified mobile terminal, calculating physical position information corresponding to logical position information about a visited network of the mobile terminal in response to the position information request, transferring the physical position information to the positioning server, receiving assistant data of the mobile terminal from the positioning server, calculating the position of the mobile terminal using the assistant data, and transferring a result of calculation for the position of the mobile terminal.  
         [0036]     Additionally, there is provided a positioning method of a mobile terminal that is roaming to a visited network provided with a position calculation service module constructed independently of a positioning service permission module. The method includes the steps of receiving, in a home network, a request to provide position information of the mobile terminal, providing, by the home network, access information for a position calculation service module of the visited network to the mobile terminal, directly accessing the position calculation service module of the visited network using the access information by the mobile terminal, and calculating and determining the position of the mobile terminal by the position calculation service module. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]     The above and other objects, features, and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0038]      FIG. 1  illustrates a conventional mobile communication system;  
         [0039]      FIG. 2  is a flowchart illustrating a conventional positioning method of a mobile terminal;  
         [0040]      FIG. 3  is a block diagram schematically illustrating a conventional network for performing a positioning of a mobile terminal;  
         [0041]      FIG. 4  is a block diagram schematically illustrating a network for performing the positioning of a mobile terminal according to an embodiment of the present invention;  
         [0042]      FIG. 5  is a flowchart illustrating a positioning method of a mobile terminal according to an embodiment of the present invention;  
         [0043]      FIG. 6  is a flowchart illustrating a positioning method of a mobile terminal according to another embodiment of the present invention; and  
         [0044]      FIGS. 7A  to  7 K are views illustrating messages being transmitted during the positioning of the mobile terminal according to an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     Preferred embodiments of the present invention will be described in detail hereinafter with reference to the accompanying drawings. In the following description of the present invention, the same drawing reference numerals are used for the same elements even in different drawings. Additionally, a detailed description of known functions and configurations incorporated herein will be omitted when it may obscure the subject matter of the present invention.  
         [0046]      FIG. 4  is a block diagram schematically illustrating a network for performing the positioning of a mobile terminal according to an embodiment of the present invention. Referring to  FIG. 4 , a network  310  or  320  for performing the positioning of the mobile terminal according to an embodiment of the present invention includes only a positioning service permission module  311  or  321  (for example, an SUPL location center (SLC). A position calculation service module  330  (for example, an SUPL positioning center (SPC) is implemented independently of the network.  
         [0047]     If a terminal B, which is registered in the home network  310 , is roaming to the visited network  320 , the positioning of the terminal B is performed in a manner that an authentication procedure and so on is performed with respect to a request for a positioning service of the terminal B using the SLC  311  provided in the home network  310 . Thereafter, functions related to the position calculation (for example, creation of assistant data, position calculation, etc.) are performed using the SPC  330  implemented independently of the home network  310 .  
         [0048]     The SPC  330  is a function module repeatedly owned by the respective network. In the embodiment of the present invention, this function module is implemented independently of the networks, and is shared by the respective networks. Functions performed by the SPC  330  may be a position calculation, assistant data delivery, retrieval function, etc. That is, if the position information request is permitted, the SPC  330  processes only work for the requested position calculation of the corresponding terminal.  
         [0049]     A plurality of SPCs may be provided for the respective networks. However, it is also possible to implement an SPC in a certain network, and other networks share the SPC. If plurality of SPCs  330  exist, it is preferable to perform the positioning by selecting the SPC that is located nearest to the terminal subject to positioning.  
         [0050]     Before performing the position calculation of the roaming mobile terminal, the SLC  311  or  321  performs a search for data between HLR and VLR in order to support necessary procedures of the mobile terminal, for example, authentication (or authorization), privacy checking, charging, roaming support, etc. That is, the SLC  311  or  321  determines whether to permit or return the position information request from the external client or the terminal itself.  
         [0051]      FIGS. 5 and 6  are flowcharts illustrating a positioning method of a mobile terminal according to first and second embodiments of the present invention. That is,  FIG. 5  illustrates the positioning method in the event that a network that has received a request for the position of a specified mobile terminal (hereinafter referred to as a ‘terminal’) from a third party (for example, an external client) requests the position measurement of the corresponding terminal (i.e., a ‘network-initiated request), and  FIG. 6  illustrates the positioning method in the even that the terminal requests its own position information (i.e., a ‘terminal-initiated’ request).  
         [0052]     Referring to  FIG. 5 , the positioning method of a roaming terminal that is performed in the event that a request is ‘network-initiated’, terminal-assisted, and corresponds to an immediate service according to an embodiment of the present invention will be explained.  
         [0053]     An SUPL agent  410  that has received a request for position information of a terminal  450  from an outside (for example, an external client) creates and transfers a position information request message MLP_SLIR using an MLP (Mobile Location Protocol) to a home SLC  420  in step S 401 . In this case, the SUPL agent  410  is a module that is included in all SUPL-serviceable network devices, and creates an MLP message for the SUPL service.  
         [0054]     Referring to  FIG. 7A , the position information request message MLP_SLIR created at step S 401  includes identification (ID) information ‘ms_ID’ of the terminal  450  subject to positioning, ID information ‘LCS-Client_ID’ of the external client that has requested the position information of the terminal, and positioning quality information ‘PQoS’ (for example, accuracy of positioning, degree of a response speed, etc.).  
         [0055]     The home SLC  420  performs the authentication of the position-requesting client and the user in step S 403 .  
         [0056]     The home SLC  420  authenticates the external client that has requested the position information of the terminal by checking ‘LCS-Client_ID’ included in the received ‘MLP_SLIR’. For example, the home SLC confirms if the external client is a company registered to use the position information.  
         [0057]     The home SLC confirms if the user of the terminal  450  the position of which is requested permits the third party to receive the position information. Accordingly, the home SLC  420  checks a pre-stored privacy profile of the terminal  450 .  
         [0058]     If it is possible to provide the corresponding service to the client that has requested the position information in step S 403 , the home SLC  420  informs the corresponding terminal  450  that the position information is requested, and creates and transfers a message SUPL_INIT for initializing the positioning process to the terminal  450  in step S 405 .  
         [0059]     The structure of the message SUPL_INIT transferred to the terminal  450  is exemplarily illustrated in  FIG. 7B . Referring to  FIG. 7B , the message SUPL_INIT includes a session ID ‘session_ID’ to be used between the home SLC  420  and the terminal  450  in the corresponding positioning process, an IP address of the home SLC ‘Home SLC IP addr.’, a positioning quality information ‘PQoS’, a privacy profile checking result ‘notification’, and information ‘posmethod’ about the kind of at least one positioning technique that can be processed.  
         [0060]     The terminal that has received the message SUPL_INIT determines whether to permit or return the positioning request by confirming ‘notification’ included in the message SUPL_INIT. If it is determined to permit the positioning request, the terminal  450  transfers a positioning process start message SUPL_START to the home SLC  420  as a response to the message SUPL_INIT in step S 407 .  
         [0061]     The structure of the message SUPL_START transferred to the home SLC  420  is exemplarily illustrated in  FIG. 7C . Referring to  FIG. 7C , the message SUPL_START includes a session ID ‘session_ID’ that is the same as that included in the message SUPL_INIT, information ‘ms-capability’ about a positioning method of the terminal  450 , and position information ‘Location_area_ID’ of a visited network to which the terminal  450  is roaming.  
         [0062]     Optionally, if it is possible for the terminal to additionally transfer information that is helpful when the network calculates the position of the cell in which the terminal itself presently exists, this information can also be included in the message SUPL_START to be transmitted. For example, if the terminal is in a GSM network, an NMR (Network to Mobile Radio signal) is a parameter that indicates a TA (Time of Arrival) of a radio signal transferred from the network to the terminal, a RXLEV (Receiver of power level) of a radio signal transferred to the terminal, etc.  
         [0063]     In this case, ‘ms-capability’ includes a kind of A-GPS (i.e., UE-assisted A-GPS or UE-based A-GPS) used in the terminal  450  and positioning protocol information (such as RRLP, RRC, IS-801, etc.) to be used by the terminal  450 .  
         [0064]     Additionally, ‘Location_area_ID’ is a logical ID that indicates a presently roaming area, and instructs the home SLC  420  to search for a visited SLC or visited network  430  in which the terminal  450  is located.  
         [0065]     The home SLC  420  searches for the visited network information (for example, the visited SLC)  430  in which the terminal  450  is located by checking ‘Location_area_ID’ included in ‘SUPL_START’, and transmits ‘Location_area_ID’ to the visited SLC  430  using the RLP (Roaming Location Protocol) in step S 409 . This obtains physical position information rough_position corresponding to ‘Location_area_ID’.  
         [0066]     In this case, a message RLP_REQ transmitted from the home SLC  420  to the visited SLC  430  may include ‘session_ID’ and ‘Location_area_ID, and may further include ‘NMR’ as exemplarily illustrated in  FIG. 7D .  
         [0067]     The visited SLC  430  that has received ‘RLP_REQ’ from the home SLC  420  calculates physical position information corresponding to ‘Location_area_ID’ in step S 411 , includes the result in ‘RLP_RSP’, and transfers ‘RLP_RSP’ to the home SLC  420  in step S 413 . It is preferable that the physical position information rough_position calculated at step S 411  is expressed using longitude and latitude values.  
         [0068]     The ‘RLP_RSP’ includes ‘session_ID’ and ‘rough_Position’ as illustrated in  FIG. 7E .  
         [0069]     If ‘PQoS’ is set to ‘low accuracy’ in step S 401 , ‘rough_position’ information may be the final position information to be sent to the SUPL agent  410 . That is, the home SLC  420  transfers ‘rough_position’ received in step S 413  to the SUPL agent  410 , and then terminates the corresponding session.  
         [0070]     However, if ‘PQoS’ is set to ‘high accuracy’, steps following step S 413  proceed as illustrated in  FIG. 5 . More specifically, the home SLC  420  requests the assistant data for calculating more accurate position information to SPC  440  by transferring the ‘rough_position’ information to SPC  440  existing outside the network or SPC existing in the visited network in step S 415 . Because the home SLC  420  and SPC  440  use the LLP (Location Protocol) protocol, SLC  420  requests the assistant data to SPC  440  using ‘LLP_REQ’.  
         [0071]     Referring to  FIG. 7F , ‘LLP_REQ’ includes an IP address of the home SLC  420  ‘Home SLC IP addr.’ for enabling SPC  440  to respond, a ‘pseudo_session ID’ newly prepared for security during data transmission between the home SLC  420  and SPC  440 , and a ‘rough_Position’. ‘pseudo_session_ID’ is optionally created by the home SLC  420 , and is used only in the SPC&#39;s positioning process. The ‘rough_position’ is information required for SPC to create more accurate assistant data in consideration of the position of SET.  
         [0072]     The home SLC  420  and SPC  440  exchange data with each other through the networks. In the case of data exchange between the home SLC  420  and SPC  440 , the security should be strengthened in order to reduce the privacy infringement problem. Accordingly, all messages transmitted between the home SLC  420  and SPC  440  may be encrypted in addition to the user of a separate ‘pseudo_session_ID’.  
         [0073]     A plurality of SPCs may be distributed in different areas. An SPC may operate independently, and may be included in the home SLC or visited SLC. The home SLC  420  selects SPC  440  existing in the nearest place to the terminal  450 , and requests the assistant data for the position calculation of the terminal  450  to the SPC  440 .  
         [0074]     The SPC  440  that has received the request for the assistant data creates the assistant data on the basis of ‘rough_Position’ included in ‘LLP_RSP’ in step S 417 . The SPC  440  sends ‘LLP_RSP’ that includes ‘pseudo_session_ID’ and ‘assistant data’ as illustrated in  FIG. 7G  to the home SLC  420  in response to the request for the position assistance information in step S 419 .  
         [0075]     The home SLC  420  that has received the assistant data of the terminal  450  from the SPC  440  creates and transfers a SUPL response message SUPL_RSP for informing the terminal  450  of the reception of the assistant data to the terminal  450  in step S 421 .  
         [0076]     Referring to  FIG. 7H , ‘SUPL_RSP’ includes ‘session_ID’, ‘pseudo_session_ID’, ‘SPC_IP_addr.’, and assistant data. The ‘SUPL_RSP’ includes ‘pseudo_session_ID’ and ‘SPC_IP_addr’ for the terminal  450  to directly connect to SPC  440  and to send and receive messages required in the positioning process.  
         [0077]     The terminal  450  that has received ‘SUPL_RSP’ creates and transfers a PDINIT (Position Determination Initiation) message that includes ‘paseudo_session_ID’ included in ‘SUPL_RSP’ and cell information in which the terminal  450  is located (See  FIG. 7I ) to SPC  440  in step S 423 . The PDINIT message is used for the terminal  450  to start a direct connection to SPC  440 . Because SPC  440  knows ‘pseudo_session_ID’ of the terminal  450 , it enables the SPC  440  to recognize its existence by including ‘psedo_session_ID’ in the PDINIT message and transferring the PDINIT message to SPC  440 .  
         [0078]     Additionally, if the terminal  450  can optionally transfer information that is helpful when the network calculates the position of the cell in which the terminal  450  is presently located (such as cell information), such information can also be included in the PDINIT message. For example, if the terminal is in a GSM network, an NMR (Network to Mobile Radio signal) is a parameter that indicates a TA (Time of Arrival) of a radio signal transferred from the network to the terminal, a RXLEV (Receiver of power level) of a radio signal transferred to the terminal, etc. Because the cell information is information that the terminal  450  may have once transferred at step S 407 , it may repeatedly be transferred at step S 423 . However, because the cell information transferred at step S 407  may be different from the cell information transferred at step S 423  due to the change of the radio environment where the terminal  450  exists with the lapse of time, it is preferable that the terminal adds the cell information to the PDINIT message.  
         [0079]     The SPC  440  sends and receives PDMESS (Position Determination Message) messages (such as RRLP, IS-801, RRC, etc.) to and from the terminal  450 , and exchanges signals required for the positioning and data with the terminal  450  in step S 425 .  
         [0080]     Thereafter, SPC  440  calculates the final position of the terminal  450 , and creates and transmits a PDRPT message including a result of calculation ‘Accurate_Position’ to the home SLC  420  in step S 427 . The PDRPT message includes ‘pseudo_session_ID’ and ‘Accurate_Position’ as illustrated in  FIG. 7J .  
         [0081]     The home SLC  420  identifies the terminal that corresponds to the result of positioning by checking ‘pseudo_session_ID included in the received PDRPT message, and then reports the final position of the terminal to the SUPL agent that requested the positioning of the corresponding terminal in step S 429 . In this case, the home SLC  420  uses ‘MLP_SLIA’ as illustrated in  FIG. 7K .  
         [0082]     Finally, the home SLC  420  transmits an SUPL end message including ‘session_ID’ to the terminal  450  to terminate the corresponding session in step S 431 .  
         [0083]     Referring to  FIG. 6 , the positioning method of a roaming terminal that is performed in the event that a request is ‘terminal-initiated’, network-assisted, and corresponds to an immediate service according to an embodiment of the present invention will be explained.  
         [0084]     First, if the terminal  450  that includes the SUPL agent requests the positioning of the terminal itself by transmitting the SUPL start message SUPL_START (See  FIG. 7C ) to the home SLC  420  in step S 501 , the home SLC  420  searches for the visited network information (for example, the visited SLC  430 ) in which the terminal  450  is located by checking ‘Location_area_ID’ included in ‘SUPL_START’, and transmits ‘Location_area_ID’ to the visited SLC  430  using an RLP (Roaming Location Protocol) in step S 503 . This is for obtaining physical position information ‘rough_position’ corresponding to ‘Location_area_ID’.  
         [0085]     An example of the message RLP_REQ transmitted from the home SLC  420  to the visited SLC  430  is illustrated in  FIG. 7D . Because the structure of the message has been explained with reference to  FIG. 5 , the detailed explanation thereof will be omitted here.  
         [0086]     The visited SLC  430  that has received ‘RLP_REQ’ from the home SLC  420  calculates physical position information corresponding to ‘Location_area_ID’ in step S 505 , includes the result of calculation in ‘RLP_RSP’ (See  FIG. 7E ) and then transfers ‘RLP_RSP’ to the home SLC  420  in step S 507 . It is preferable that the physical position information rough_position calculated in step S 505  is expressed using longitude and latitude values.  
         [0087]     If ‘PQoS’ is set to ‘low accuracy’ in step S 501 , ‘rough_position’ information may be the final position information to be sent to the SUPL agent  410 . That is, the home SLC  420  transfers ‘rough_position’ received at step S 507  to the terminal  450 , and then terminates the corresponding session. Otherwise, the steps following step S 507  proceed as illustrated in  FIG. 6 .  
         [0088]     The home SLC  420  requests the assistant data for calculating more accurate position information to SPC  440  by transferring the ‘rough_position’ information to SPC  440  existing outside the network or SPC existing in the visited network in step S 509 . Because the home SLC  420  and SPC  440  use the LLP (Location Protocol) protocol, the SLC  420  requests the assistant data to SPC  440  using ‘LLP_REQ’ (See  FIG. 7F ).  
         [0089]     The structure of ‘LLP_REQ’ has been explained with reference to  FIG. 5 , thus the detailed explanation thereof will be omitted here.  
         [0090]     A plurality of SPCs may be distributed in plural areas. An SPC may operate independently, and may be included in the home SLC or visited SLC. The home SLC  420  selects SPC  440  existing in the nearest place to the terminal  450 , and requests the assistant data for the position calculation of the terminal  450  to the SPC  440 .  
         [0091]     The SPC  440  that has received the request for the assistant data creates the assistant data on the basis of ‘rough_Position’ included in ‘LLP_RSP’ in step S 511 . Thereafter, the SPC  440  sends ‘LLP_RSP’ that includes ‘pseudo_session_ID’ and ‘assistant data’ as illustrated in  FIG. 7G  to the home SLC  420  in response to the request for the position assistance information in step S 513 .  
         [0092]     The home SLC  420  that has received the assistant data of the terminal  450  from the SPC  440  creates and transfers a SUPL response message SUPL_RSP (See  FIG. 7H ) for informing the terminal  450  of the reception of the assistant data to the terminal  450  in step S 515 .  
         [0093]     The terminal  450  that has received ‘SUPL_RSP’ creates and transfers a PDINIT message (See  FIG. 7I ) to SPC  440  in step S 517 . The PDINIT message is used for the terminal  450  to start a direct connection to SPC  440 . In this case, because SPC  440  knows ‘pseudo_session_ID’ of the terminal  450 , it enables SPC  440  to recognize its existence by including ‘psedo_session_ID’ in the PDINIT message and transferring the PDINIT message to SPC  440 .  
         [0094]     Additionally, if the terminal  450  can optionally transfer information that is helpful when the network calculates the position of the cell in which the terminal  450  is presently located (such as cell information), such information can also be included in the PDINIT message. For example, if the terminal is in a GSM network, an NMR (Network to Mobile Radio signal) is a parameter that indicates a TA (Time of Arrival) of a radio signal transferred from the network to the terminal, a RXLEV (Receiver of power level) of a radio signal transferred to the terminal, etc.  
         [0095]     Because the cell information is information that the terminal  450  may have once transferred in step S 501 , it may repeatedly be transferred in step S 517 . However, because the cell information transferred in step S 501  may be different from the cell information transferred in step S 517  due to the change of the radio environment where the terminal exists with the lapse of time, it is preferable that the terminal  450  adds the cell information to the PDINIT message.  
         [0096]     The SPC  440  sends/receives PDMESS (Position Determination Report) messages (such as RRLP, IS-801, RRC, etc.) to and from the terminal  450 , and exchanges signals required for the positioning and data with the terminal  450  in step S 519 .  
         [0097]     Thereafter, SPC  440  calculates the final position of the terminal  450 , and creates and transmits a PDRPT message (See  FIG. 7J ) including a result of calculation ‘Accurate_Position’ to the terminal  450  in step S 521 . Then, SPC  440  informs the home SLC  420  of the termination of the positioning process using the LLP protocol in step S 523 .  
         [0098]     The home SLC  420  transmits an SUPL end message including ‘session_ID’ to the terminal  450  to terminate the corresponding session in step S 525 .  
         [0099]     As described above, according to the present invention, the positioning service permission module that includes the positioning service authentication and the privacy protection function and the position calculation service module that performs the creation of assistant data of the terminal and the position calculation using the assistant data are separated from each other, but a plurality of networks can share the independently implemented position calculation service module. Accordingly, an accurate positioning result can be obtained with a cost for the implementation of the positioning system being reduced.  
         [0100]     Additionally, the present invention can prevent a network capable of providing the positioning service from exclusively using the position calculation system, even if the mobile terminal subject to positioning deviates from the home network and is located in another network, the accuracy of assistant data to be transferred to the terminal can be improved.  
         [0101]     While the present invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.