USRE45545E1 - Method for locating mobile terminals - Google Patents

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.

Description

PRIORITY

This application claims priority to an application entitled “METHOD FOR LOCATING MOBILE TERMINALS”, filed in the Korean Intellectual Property Office on Jan. 31, 2004 and assigned Serial No. 2004-0006480, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for locating mobile terminals, and more particularly to a method for locating mobile terminals located in an area where GPS assistance information required for location determination is not provided.

2. Description of the Related Art

As mobile terminals have become smaller, lighter, and more simple to use and mobile communication devices and their networks have spread worldwide, users of mobile communication services carry their mobile terminals and receive mobile communication services in addition to other services through their mobile terminals even when they travel. In the environment of a global system for mobile communications, many users also desire to receive application services (e.g., information on traffic, daily life, news, weather, location, etc.) using location information of their mobile terminals. A system to allow users to obtain their location information using the mobile terminals has been commercialized in some countries, for example, Korean mobile communication areas provided by SK telecom, KTF and the like, or Japanese or Western mobile communication areas of NTT, DoCoMo, Sprint PCS, KDDI, Vodafone and the like.

FIG. 1 is a schematic diagram showing the configuration of a general mobile communication system (particularly, a Global System for Mobile communication (GSM) or a Universal Mobile Telecommunication System (UMTS)). As shown in this figure, the GSM or UMTS includes a Core Network (CN)110, a plurality of Radio Network Subsystems (RNSs)120 and130, and User Equipment (UE)150.

The CN110 manages information of UEs150, and performs mobility management, session management and call management functions.

TheRNS120 or130, serves to transfer data received from theCN110 to users via an air interface. To this end, theRNS120 or130, includes a Radio Network Controller (RNC), and a plurality of base stations (node B). For example, theRNS120 includes anRNC121 and base stations (node B)123 and125, and theRNS130 includes anRNC131 and base stations (node B)133 and135.

RNC121 or131 is classified into a serving RNC (SRNC), a drift RNC (DRNC) and a controlling RNC (CRNC) based on its operation. The SRNC is an RNC that manages information of UEs belonging to the RNC, and handles data transmission between the UEs and theCN110 via an Iu interface. The DRNC is an RNC that intermediates data transmission between a UE belonging to a different RNC and an RNC (for example, an SRNC) to which the UE belongs. The CRNC is an RNC that controls each of the base stations. For example, inFIG. 1, if theRNC121 manages the information of theUE150, theRNC121 is an SRNC of the UE150, and if the UE150 moves and communicates data with theRNC121 via theRNC131, theRNC131 is a DRNC of theUE150. In addition, theRNC121, which controls the base station (node B)125 in communication with the UE150, is a CRNC of thebase station125. In the example ofFIG. 1, information and data of the UE150 is transmitted and received to and from theCN110 via theRNC121 that is an SRNC of the UE150.

There are various methods which are typically used for locating UEs in the mobile communication network. These methods are generally divided into three types which will be described below.

The first is a cell-based location method in which the location of a UE is determined based on information of a cell located nearest to the UE or based on information of a cell that manages the UE. The second is a network-based location method in which a signal measured between the node B and a UE is used to calculate a Time of Arrival (TOA) or a Time Difference of Arrival (TDOA) based on the intensity of the signal or based on radio wave transfer time thereof and the location of the UE is determined by triangulation using the calculated TOA or TDOA. The third is a GPS-based location method in which the location of a UE is determined using a Global Positioning System (GPS) developed by the US Department of Defense. One particular GPS-based location method, which complements and applies the GPS technology to a mobile communication network, is called Network-Assisted GPS (AGPS).

In the prior art, if a Location Service (LCS) client located external to a network requests location determination of a UE, a preparatory process for locating the UE is first performed, and a signal required to locate the UE is measured, and then the location of the UE is calculated based on the measured signal. In the preparatory process, a privacy indicator for limiting access to personal information or the like of the UE is read, and network resources are allocated, and then a location technique is selected according to the performance of the UE and the network, and quality of Service (QoS) requested by the LCS client. The location measurement process is performed between the Universal Terrestrial Random Access Network (UTRAN) and the UE. In this process, a location measurement signal, including a signal required to measure the location of the UE, is obtained and then the location of the UE is calculated using the location technique selected in the preparatory process. Here, the UE must be an individual UE whose Mobile Subscriber ISDN Number (MSISDN) or International Mobile Subscriber Identity (IMSI) is already known.

The above location measurement process is performed frequently when the UE moves out of a Gateway Mobile Location Center (GMLC), which is registered as a home GMLC of the UE in the CN, and it is thus located in another GMLC or when a location service for locating the UE is requested by an external LCS client or the UE itself. Here, the GMLC manages location information of UEs located in a Public Land Mobile Network (PLMN). The PLMN is a geographically or logically distinguishable mobile communication network, and one PLMN may include one or more GMLCs.

FIG. 2 is a process flow diagram showing a conventional method for locating mobile terminals, particularly when an external LCS client (hereinafter referred to as a “client”)160 requests location determination of a UE_A155.

As shown inFIG. 2, theclient160 requests a location service (LCS) of a UE, the location of which theclient160 desires to know, from a requesting GMLC111 connected to the client160 (S11). That is, theclient160 requests location information of the UE_A155 from the requesting GMLC111. The “requesting” GMLC111 is a GMLC that “requests” location of the UE_A155.

Then, the requesting GMLC111 requests home PLMN information of the UE_A155 from a Home Location Register/Home Subscriber Server (HLR/HSS)115 (S13), and receives the home PLMN information from the HLR/HSS115 (S15). As a server storing roaming information and registrant information of UEs, the HLR/HSS115 responds to the request from the requestingGMLC111 using the stored registrant information of the UEs. That is, in response to the request from the requesting GMLC111, the HLR/HSS115 provides the home PLMN information of the UE_A155 to the requesting GMLC111 (S15).

Then, using the home PLMN information of the UE_A155 received from the HLR/HSS115 at step S15, the requesting GMLC111 requests information of a visited PLMN, where the UE_A155 is currently located, from a home GMLC113 of the UE_A155 (S17). In response to the request from the requesting GMLC111, the home GMLC113 requests and receives information of the visited PLMN from the HLR/HSS115 (S21, S23, respectively) after performing authentication for privacy protection (S19). Using the visited PLMN information, the home GMLC113 requests the location information of the UE_A155 from a GMLC117 in the visited PLMN20 (S25). Since it belongs to the visited PLMN where the UE_A155 is currently located, the GMLC117 is referred to as a “visited GMLC”.

The location of the UE_A155 is calculated in the visited GMLC117 in the PLMN being visited by the UE_A155, an MSC/SGSN (Mobile-services Switching Center/Serving GPRS (General Packet Radio Service) Support Node)119, a Radio Access Network (RAN)170 and the UE_A155 (S27).

As described above, the mobile communication network generally uses three location methods, i.e., a cell ID-based location method, a TDOA location method, and an A-GPS location method. The PLMN being visited by the UE_A155 can also use one of the three location methods to measure the location of the UE_A155. Depending on the burden on network resources or depending on where the location calculation is performed, the conventional location methods described above can be classified into the following two types. The first type is a UE-based location method in which the location of a UE is calculated by the UE itself based on pseudo range information and location assistance information. The second type is a UE-assisted location method in which a UE obtains pseudo range information using GPS assistance information (or A-GPS information) acquired from GPS satellite signals, and it then transfers the pseudo range information to an RNC managing an LCS service of the UE so that the location of the UE is calculated in the network.

In the example ofFIG. 2, the request for the location information of the UE_A155 transferred to the GMLC117 being visited by the UE_A155 is transferred to the RAN170 via the MSC/SGSN119. In the UE-based location method, a serving RNC of the UE_A155 transmits its A-GPS information to the UE_A155 so that the UE_A155 calculates its own location. In the UE-assisted location method, the UE_A155 transmits the acquired GPS pseudo range information to an RNC so that the location of the UE_A155 is calculated in the network.

If the location of the UE_A155 has been calculated based on one of the UE-based and UE-assisted methods at step S27, the visited GMLC117 transfers the calculated location information of the UE_A155 to the home GMLC113. The home GMLC113 transfers the location information received from the visited GMLC117 to theclient160 via the requesting GMLC111 (S33, S35) after again performing authentication (S31).

However, when an external LCS client or a UE requests a location service of the UE located in a PLMN that includes no location calculation system such as a Location Measurement Unit (LMU) or a Serving Mobile Location Center (SMLC), the conventional methods for locating mobile terminals (i.e., UEs) cannot calculate the location of the UE. That is, if the visited PLMN, where the UE is located, provides no location assistance information, the PLMN returns a failure response to the location measurement request from the UE or the LCS client.

The conventional location methods cannot obtain improved location service results over standalone GPS location measurement in a mobile communication network that provides no basic location service. For example, in the conventional location methods, an LCS client cannot obtain location information of a UE that is traveling to an accident area or is moving to a troubled area, and a UE cannot independently utilize travel or geographical information using an LCS service provided by its home PLMN, and also cannot independently check its location information to use an LCS service database stored in the UE.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problem, and it is an object of the present invention to provide a method for locating mobile terminals, which can obtain location information of a mobile terminal irrespective of the area or communication network where the mobile terminal is located.

It is another object of the present invention to provide a method for locating mobile terminals, which can locate a mobile terminal in an area where no location assistance information is provided.

It is a further object of the present invention to provide a method for locating mobile terminals, in which location assistance information of a target terminal, the location of which is to be determined, is produced based on location information of a home communication network of the target terminal received through a packet network.

It is another object of the present invention to provide a method for locating mobile terminals, which obtains effective and accurate location information.

It is yet another object of the present invention to provide a method for locating mobile terminals, which can provide continuity and integrity of a location service even when the mobile terminal is roaming.

In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a method for locating mobile terminals, including the steps of checking information of a home Public Land Mobile Network (PLMN) of a target mobile terminal, the location of which is to be determined, in response to a location service request from a client for location determination of the target mobile terminal; checking information of a visited PLMN where the target mobile terminal is located, based on the information of the home PLMN; calculating location assistance information of the visited PLMN by the home PLMN using specific location information of the visited PLMN; and transferring the location assistance information to the visited PLMN of the target mobile terminal.

In accordance with another aspect of the present invention, the above and other objects can be accomplished by the provision of a method for locating mobile terminals, including the steps of in a visited PLMN where a target terminal is located, checking information of a home PLMN of the target terminal in response to a location service request of the target terminal; requesting location assistance information by the Serving GPRS (General Packet Radio Service) Support Node (SGSN), required for location calculation of the target terminal, from the home PLMN; calculating, by the home PLMN, the location assistance information of the target terminal located in the visited PLMN using specific location information of the visited PLMN in response to the request at step b); and transferring the location assistance information to the target terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram showing the configuration of a general mobile communication system;

FIG. 2 is a flow diagram illustrating a conventional method for locating mobile terminals;

FIG. 3 is a diagram illustrating the configuration of a network for locating mobile terminals according to an embodiment of the present invention;

FIGS. 4 and 5 are flow diagrams illustrating a method for locating mobile terminals according to a first embodiment of the present invention;

FIGS. 6A to 6C are diagrams illustrating the format of a message transmitted when the location of a mobile terminal is determined according to the first embodiment of the present invention;

FIGS. 7 and 8 are flow diagrams illustrating a method for locating mobile terminals according to a second embodiment of the present invention; and

FIGS. 9A to 9E are diagrams illustrating the format of a message transmitted when the location of a mobile terminal is determined according to the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, preferred embodiments of the present invention will be described in detail with reference to the annexed drawings. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention unclear.

FIG. 3 is a diagram illustrating the configuration of a network for locating mobile terminals according to an embodiment of the present invention. This embodiment is useful particularly when aPLMN220 visited by atarget UE155, the location of which is to be determined, supports no location service (LCS). Thetarget UE155 is connected to a Core Network (CN)210 via a Radio Access Network (RAN) such as a base station (node B)221 or an SRNC (Serving RNC)222. A plurality of data (for example, pseudo range data acquired from a GPS satellite signal, a satellite ID, and a reference time when a GPS signal is acquired) required for location determination of theUE155 is encapsulated with an IP address. Using routing information stored in a Visitor Location Register (VLR), the encapsulated data is transferred to ahome GMLC231 in ahome PLMN230, to which theUE155 belongs, after passing through anSGSN223 and a GGSN (Gateway GPRS Support Node)224 that support a packet data service.

Thehome PLMN230 needs to perform location service authentication, approval, and location calculation of theUE155 using its internal resources. To accomplish this, thehome PLMN230 needs to include therein network components such as anSGSN232, an HLR/HSS233, a Privacy Profile Register (PPR)234 and Mobile Location Centers (MLCs) such as a servingMLC235 anddedicated MLC236.

If anexternal LCS client240 desires to measure the location of theUE155, theexternal LCS client240 requests an LCS service from thehome GMLC231 after connecting to a requestingGMLC241 using routing information such as an IMSI, an MSISDN or an IP address.

FIG. 4 is a flow diagram illustrating a method for locating mobile terminals according to a first embodiment of the present invention. In particular, this figure illustrates an example of the location method where the location of aUE_A155 is calculated in a UE-assisted method at the request of an external LCS client (hereinafter, referred to as a “client”)240 for location of theUE_A155.

As shown inFIG. 4, theclient240 requests a location service (LCS) of a UE, the location of which theclient240 desires to know, from a requestingGMLC241 connected with the client240 (S101). That is, theclient240 requests location information of theUE_A155 from the requestingGMLC240. In this process, theclient240 transmits identification of the UE, the location of which it desires to know, to the requestingGMLC241. The “requesting”GMLC241 is a GMLC that “requests” location of theUE_A155.

Then, using the UE identification information (for example, an IMSI or an IP address) received from theclient240, the requestingGMLC241 requests home PLMN information (for example, routing information of a home GMLC231) of theUE_A155 from an HLR/HSS233 (S103), and receives the home PLMN information from the HLR/HSS233 (S105). As a server storing roaming information and registrant information of UEs, the HLR/HSS233 responds to the request from the requestingGMLC241 using the stored registrant information of the UEs. That is, in response to the request from the requestingGMLC241, the HLR/HSS233 provides the home PLMN information of theUE_A155 to the requestingGMLC241.

Then, using the routing information of thehome GMLC231 of theUE_A155 received from the HLR/HSS233 at step S105, the requestingGMLC241 requests location information of theUE_A155 from thehome GMLC231 of the UE_A155 (S107). In response to the request from the requestingGMLC241, the home GMLC213 requests and receives information of a PLMN visited by theUE_A155 from the HLR/HSS233 (S111, S113) after performing authentication for privacy protection (S109).

In another embodiment, the steps of acquiring the routing information of the home GMLC231 (S103 and S105), and the steps of acquiring the routing information of theUE_A155 existing in the roaming zone (S111, S113) may be implemented in two steps; one step for simultaneously requesting routing information ofhome GMLC231 and routing information ofUE_A155 existing in a roaming zone and the other step for simultaneously receiving the routing information of both thehome GMLC231 and theUE_A155 existing in the roaming zone by the requestingGMLC241. For example, the requestingGMLC241 simultaneously requests both the information of thehome GMLC231 of the target UE_A155 and the information (for example, the IP address of a visited GGNS) for routing to the visited PLMN where theUE_A155 is located at the requested time.

After the routing information acquisition, thehome GMLC231 checks, based on the visited PLMN information, whether the visited PLMN is a remote area (S115). That is, thehome GMLC231 checks whether the visited PLMN is an area not supporting the A-GPS function. If the visited PLMN is an area not supporting the A-GPS function, thehome GMLC231 calculates location assistance information of theUE_A155 located in the visited PLMN (S117), and transmits a message requesting location information of theUE_A155, together with the location assistance information, to the visitedGGSN224 in the visited PLMN (S119).

At step S117, based on a cell ID received from the visited PLMN of theUE_A155, thehome GMLC231 calculates GPS satellite orbit and geographical information of a corresponding cell where theUE_A155 is present. Then, based on the calculation result, thehome GMLC231 calculates effective location assistance information (for example, GPS navigation parameters) to allow theUE_A155 to effectively acquire GPS signals (UE-assisted LCS) and also to perform improved location calculation using acquired raw GPS data (UE-based LCS).

To carry out the above step S117, thehome GMLC231 preferably includes a database (DB) for allowing it to obtain geographical information of each of a plurality of PLMNs using the cell ID of each of the PLMNs. For example, using approximate location information of the visited PLMN (for example, geographical information such as “Suwon” and “Daegu” (the names of some Korean cities) managed in theHLR233, thehome PLMN231 detects the geographical information (for example, latitude and longitude) of the visited PLMN from the database (DB) and then calculates location assistance information of the visited PLMN using the detected geographical information.

Some examples of the location assistance information calculated at step S117 can include the number of satellites, satellite IDs, GPS satellite reference time, ionospheric delay correction information, ephemeris and clock correction information, UTC (Universal Time Coordinated) offset, satellite almanac, an invisible satellite list, Doppler model coefficients, Doppler search window size, approximate geographical information of a cell of interest, and code phase-related information. These information items, together with the IP address, are encapsulated in a packet, which is then transferred to the visitedGGSN224. The visitedGGSN224 is a GGSN that belongs to the PLMN being visited by theUE_A155.

FIG. 6A illustrates an example of the format of amessage510 transmitted from thehome GMLC231 to theGGSN224 at the above step S119. As shown inFIG. 6a, themessage510 includes an LCS sessionrequest flag field511, a sourceIP address field512, a destinationIP address field513, aclient ID field514, a locationcalculation type field515 and a locationassistance information field516.

The LCS sessionrequest flag field511 stores a flag informing theUE_A155 that themessage510 is a location information request message. The sourceIP address field512 stores the IP address of thehome GMLC231, and the destinationIP address field513 stores the IP address of theUE_A155. Theclient ID field514 stores the ID of a client requesting the location of theUE_A155, which is used for authentication of the request for location information of theUE_A155. The locationcalculation type field515 stores the type of location calculation. Specifically, the locationcalculation type field515 stores information indicating whether the location calculation type is “UE-based”, in which theUE_A155 itself carries out the location calculation of theUE_A155, or “UE-assisted type”, in which thehome GMLC231 calculates the location of theUE_A155 based on a GPS pseudorange measured by theUE_A155. In the example ofFIG. 4, since the location calculation type is UE-assisted, the locationcalculation type field515 of the message transmitted at step S119 stores information indicating that the location calculation type is UE-assisted.

The locationassistance information field516 stores location assistance information of theUE_A155 measured by thehome GMLC231. This field may also store location assistance information selected based on characteristics of theUE_A155 that are previously determined by thehome GMLC231. When receiving themessage510 configured as shown inFIG. 6A from thehome GMLC231 at step S119, theGGSN224 transfers the message to theUE_A155 via the MSC/SGSN223 and the Radio Access Network (RAN)270 (S121, S123 and S124). Here, depending on available network resources or traffic states among location assistance information stored in thehome GMLC231, thehome GMLC231 may transfer only location assistance information for acquiring an initial GPS signal to theUE_A155, and may use the remaining available location assistance information in location calculation when a pseudorange measurement is received from theUE_A155.

The message transfer from thehome GMLC231 to theRAN270 is performed in the same manner as packet transmission in the general GPRS support network. Specifically, themessage510 is converted into packet data (e.g., a PDP Packet Data Protocol PDU Protocol Data Unit), and the packet data is then encapsulated according to a GPRS Tunneling Protocol (GTP). The encapsulated packet data is transferred to theRAN270 along a transmission path tunneled to theRAN270, which is then transferred from theRAN270 to an upper application layer of theUE_A155 through the Packet Data Convergence Protocol (PDCP).

Then, theUE_A155 checks location calculation-type included in themessage510, and performs processing according to the location calculation type. In the example ofFIG. 4, since the location calculation type is UE-assisted, theUE_A155 measures a GPS pseudorange of theUE_A155 using the location assistance information included in the message510 (S125). Then, theUE_A155 transfers the calculation result to thehome GMLC231 via theRAN270, the MSC/SGGN223 and the visited GGSN224 (S126, S127, S129 and S131). Here, the GPS pseudorange is routed and transferred to thehome GMLC231 after being encapsulated with the IP address of thehome GMLC231.FIG. 6B illustrates the format of a message carrying the location information of theUE_A155.

As shown inFIG. 6B, amessage520 transmitted from theUE_A155 to theGMLC231 includes an LCSresponse flag field521, a source IP address (i.e., the IP address of the UE_A155)field522, a destination IP address (i.e., the IP address of the home GMLC231)field523, aclient ID field524, a locationcalculation type field525 and a GPS pseudorange (of the UE_A155)field526. A detailed description of data stored in these fields is omitted herein since it is similar to the description ofFIG. 6A.

When receiving the GPS pseudorange of theUE_A155, thehome GMLC231 calculates the location of theUE_A155 using the GPS pseudorange (S133), and transfers the calculation result to theclient240 via the requestingGMLC241.

FIG. 5 is a process flow diagram showing a method for locating mobile terminals according to a first embodiment of the present invention. In particular, this figure shows an example of the location method where the location of theUE_A155 is calculated in a UE-based method at the request of an external LCS client (hereinafter, referred to as a “client”)240 for location of theUE_A155.

Steps S201 to S224 ofFIG. 5 are similar to steps S101 to S124 ofFIG. 4, and thus a detailed description of steps S201 to S224 will be omitted. However, since the location calculation type is UE-based in the example ofFIG. 5, part of themessage510 transferred from theGMLC231 to theUE_A155 at steps S219 to S224 is different from that ofFIG. 4. That is, the locationcalculation type field515 of themessage510 ofFIG. 5 stores information indicating that the location calculation type is UE-based. The method for transferring the message from thehome GMLC231 to theRAN270 at steps S219 to S224 is similar to that ofFIG. 4 described above, and thus a detailed description thereof will be omitted.

Then, theUE_A155 checks location calculation type included in themessage510, and performs processing according to the location calculation type. In the example ofFIG. 5, since the location calculation type is UE-based, the UE-A155 measures a GPS pseudorange of theUE_A155 using the location assistance information included in themessage510, and calculates the location of theUE_A155 based on the measured GPS pseudorange (S225). Then, theUE_A155 transfers the calculation result to theclient240 via theRAN270, the MSC/SGGN223 and the visitedGGSN224, thehome GMLC231 and the requesting GMLC241 (S226, S227, S229, S231, S235 and S237). Here, the location information of theUE_A155 is routed and transferred to thehome GMLC231 after being encapsulated with the IP address of thehome GMLC231.FIG. 6C illustrates the format of a message carrying the location information of theUE_A155.

As shown inFIG. 6C, amessage530 transmitted from theUE_A155 to theGMLC231 includes an LCSresponse flag field531, a source IP address (i.e., the LP address of the UE_A155)field532, a destination IP address (i.e., the IP address of the home GMLC231)field533, aclient ID field534, a locationcalculation type field535 and a GPS location information (of the UE_A155)field536. A detailed description of data stored in these fields is omitted herein since it is similar to the description ofFIG. 6A.

FIG. 7 is a flow diagram showing a method for locating mobile terminals according to a second embodiment of the present invention. In particular, this figure illustrates an example of the location method where the location of aUE_A155 is calculated in a UE-assisted method at the request of theUE_A155 for location of theUE_A155 located in an area (called a “remote area”) not supporting the A-GPS function. Here, theUE_A155 is a target UE, the location of which is to be determined. TheUE_A155 needs to request the location thereof in a remote area as in this example in the case where, in an area not supporting the A-GPS function, theUE_A155 desires to independently know its location information to use an LCS service database stored in theUE_A155 or to utilize travel or geographic information using an LCS service provided from the PLMN.

As shown inFIG. 7, theUE_A155 first needs to connect to a network to request its location. To connect to the network, theUE_A155 requests network connection from an MSC/SGSN223 via a Radio Access Network (RAN)270 (S301, S303), and receives, as a response to the request, network connection approval from the MSC/SGSN223 (S305), and then connects to the network via an authentication process with the MSC/SGSN223 (S307). If theUE_A155 has already been connected to the network, steps S301 to A307 can be omitted.

When connected to the network, theUE_A155 requests location information of theUE_A155 from the MSC/SGSN223 via the RAN270 (S309). Then, after determining that a PLMN being visited by theUE_A155 itself cannot provide location information (for example, it cannot support the A-GPS function), theSGSN223 receives routing information (for example, the IP address of a home GMLC231) of a home PLMN of theUE_A155 from the Visitor Location Register (VLR)225 (S311, S313), and then transmits a message requesting location information of theUE_A155 to aGGSN224 of the visited PLMN (S315). Here, theSGSN223 transmits the location information request message, together with the IP address of thehome GMLC231, to theGGSN224.

FIG. 9A illustrates the format of a locationinformation request message610 to be transferred to theGGSN224. As shown inFIG. 9A, the locationinformation request message610 includes an LCS sessionrequest flag field611, a UE_A ID (for example, an IMSI and an IP address of the UE_A155)field612, acell ID field613, and a locationcalculation type field614. The locationinformation request message610 may further include an expirationtime information field616 indicating an expiration time of the request information and alocation QoS field615 to guarantee the quality of service.

After receiving the UE_A locationinformation request message610 as shown inFIG. 9a, together with the IP address of thehome GMLC231, from the MSC/SGSN223 at step S315, theGGSN224 requests the location of theUE_A155 from thehome GMLC231 using the IP address of the home GMLC231 (S317). That is, theGGSN224 transfers the locationinformation request message610 to thehome GMLC231. Here, as shown inFIG. 9A, the locationinformation request message610 includes cell information (for example, a cell ID) of a cell being visited by theUE_A155, which is necessary to support the remote A-GPS function.

After receiving the locationinformation request message610, thehome GMLC231 requests authentication of the service from the HLR/HSS233 (S319), and in response to this request, the HLR/HSS233 performs authentication of the service and processing for privacy protection (S321), and then transfers the authentication (e.g., an approval) result to the home GMLC231 (S323).

If thehome GMLC231 receives approval of the service at steps S319 to S323, thehome GMLC231 calculates location assistance information of the UE_A115 (S325), and then transmits the calculated location assistance information to the visitedGGSN224 of the visited PLMN (S327).

At step S325, based on a cell ID received from the visited PLMN of theUE_A155, thehome GMLC231 calculates GPS satellite orbit and geographical information of a corresponding cell where theUE_A155 is present. Then, based on the calculation result, thehome GMLC231 calculates effective location assistance information (for example, GPS navigation parameters) to allow theUE_A155 to effectively acquire GPS signals (UE-assisted LCS) and also to perform improved location calculation using acquired raw GPS data (UE-based LCS).

To carry out the above step S325, thehome GMLC231 preferably includes a database (DB) for allowing it to obtain geographical information of each of a plurality of PLMNs using the cell ID of each of the PLMNs. For example, using the cell ID of the visited PLMN, thehome PLMN231 detects the geographical information of the visited PLMN from the database (DB) and then calculates location assistance information of theUE_A155 located in the visited PLMN using the detected geographical information.

Some examples of the location assistance information calculated at step S325 are the number of satellites, satellite IDs, GPS satellite reference time, ionospheric delay correction information, ephemeris and clock correction information, UTC (Universal Time Coordinated) offset, satellite almanac, an invisible satellite list, Doppler model coefficients, Doppler search window size, approximate geographical information of a cell of interest, and code phase-related information. After receiving the location assistance information at step S327, theGGSN224 transfers the location assistance information to theUE_A155 via the MSC/SGSN223 and the RAN270 (S329, S331 and S333). Here, only location assistance information for acquiring an initial GPS signal may be transferred to theUE_A155, and the remaining available location assistance information may be used in location calculation when a pseudorange measurement is received from theUE_A155. The location assistance information transferred from thehome GMLC231 to theUE_A155 is in the form of amessage620 as shown inFIG. 9B. As shown inFIG. 9B, the location assistanceinformation transfer message620 includes a source (home GMLC)IP address field621, a destination (UE_A)IP address field622, a locationcalculation type field623 and a locationassistance information field624. In the example ofFIG. 7, since the location calculation type is UE-assisted, the locationcalculation type field623 stores information indicating that the location calculation type is UE-assisted.

After receiving the location assistance information at step S333, theUE_A155 measures a GPS pseudorange of theUE_A155 using the location assistance information (S335). TheUE_A155 then transfers the measured GPS pseudorange to thehome GMLC231 via theRAN270, the MSC/SGGN223 and the visited GGSN224 (S337, S339, S341 and S343). The GPS pseudorange is routed and transferred to thehome GMLC231 after being encapsulated with the IP address of thehome GMLC231.

FIG. 9C shows an example of amessage630 for transferring the GPS pseudorange to thehome GMLC231. As shown inFIG. 9C, the GPSpseudorange transfer message630 includes a source (UE_A)IP address field631, a destination (home GMLC)IP address632, a locationcalculation type field633 and a UE_AGPS pseudorange field634.

The message transfer at steps S337 to S343 is preferably performed in a packet data tunneling mode based on the GTP protocol as in the message transfer from thehome GMLC231 to theRAN270 inFIG. 4. After receiving the GPS pseudorange of theUE_A155 at steps S337 to S343, thehome GMLC231 calculates the location of theUE_A155 using the received GPS pseudorange (S345), and transfers the calculation result to theUE_A155 via the visitedGGSN224 and the MSC/SGSN223 (S347, S349 and S351). Thehome GMLC231 may also transfer the calculation result (for example, location information of the UE_A) to the client240 (S353).

FIG. 9D shows an example of amessage640 for transferring the location information of theUE_A155. As shown inFIG. 9D, the UE_A locationinformation transfer message640 includes a source (home GMLC)IP address field641, a destination (UE_A)IP address642, a locationcalculation type field643 and a UE_Alocation information field644.

FIG. 8 is a flow diagram showing a method for locating mobile terminals according to a second embodiment of the present invention. In particular, this figure illustrates an example of the location method where the location of aUE_A155 is calculated in a UE-based method at the request of theUE_A155 for location of theUE_A155 located in an area (called a “remote area”) not supporting the A-GPS function. As in this example, theUE_A155 needs to request the location thereof in a remote area in such a case as described above at the beginning of the description ofFIG. 7.

Steps S401 to S433 ofFIG. 8 are similar to steps S301 to S333 ofFIG. 7, and thus a detailed description of steps S401 to S433 will be omitted. However, since the location calculation type is UE-based in the example ofFIG. 8, part of themessage610 transferred at steps S409, S415 and S417 is different from that ofFIG. 7. That is, the locationcalculation type field623 of themessage610 ofFIG. 8 stores information indicating that the location calculation type is UE-based. The method for transferring themessage610 is similar to that ofFIG. 7 described above, and thus a detailed description thereof will be omitted.

After receiving the location assistance information at step S433, theUE_A155 measures the GPS pseudorange of theUE_A155 using the location assistance information and then calculates the location of theUE_A155 using the measured GPS pseudorange (S435). Then, theUE_A155 transfers the calculation result to theclient240 via theRAN270, the MSC/SGGN223, the visitedGGSN224 and the home GMLC231 (S437, S439, S441, S443 and S445). The location information of theUE_A155 is routed and transferred to thehome GMLC231 after being encapsulated with the IP address of the home GMLC.FIG. 9E shows an example of amessage650 for transferring the location information of theUE_A155. As shown inFIG. 9E, the UE_A locationinformation transfer message650 includes a source (UE_A)IP address field651, a destination (home GMLC)IP address652, a locationcalculation type field653 and a UE_Alocation information field654.

In the first and second embodiments of the present invention, theUE_A155 is an IP support terminal that can perform both encapsulation and decapsulation.

As apparent from the above description, the present invention provides a method for locating mobile terminals that has the following features and advantages. First, location information of a mobile terminal can 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. In addition, location assistance information of a mobile terminal, the location of which is to be determined, is produced based on location information of a home communication network of the mobile terminal received through a packet network, thereby obtaining effective and accurate location information. Further, continuity and integrity of a location service can be provided even when the mobile terminal is roaming.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, the scope of the present invention should not be limited to the above embodiments, but defined by the accompanying claims as well as equivalents thereof.

Claims (54)

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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 1, wherein the location assistance information is transmitted to the target terminal through the visited PLMN.

18. The method according toclaim 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 toclaim 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 toclaim 19, wherein the request message includes at least a Cell ID of the target terminal.

21. The method according toclaim 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 toclaim 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 toclaim 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 toclaim 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.

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