MXPA00001431A - Method and apparatus of determining the position of a mobile station - Google Patents

Abstract

The present invention relates generally to the problem of positioning of a mobile station ("MS") in a Public Land Mobile Network ("PLMN"), and more particularly to the problem of establishing the most accurate estimate of the last known position of the mobile station when the mobile station has switched off or has left the coverage area of the network. An application first sends a request to a Mobile Positioning Centre, requesting position information for a particular subscriber. The MPC contacts the preferred Positioning Procedure, e.g. GPS, to obtain the positioning information. If this information is not available then the MPC contacts the HLR to get the last known positioning data. The HLR will try to retrieve the last known positioning data from the VLR and forward it to the MPC. If this is not available then the last known position stored in the HLR is forwarded to the MPC.

Description

METHOD AND DEVICE FOR DETERMINING THE LOCATION OF A MOBILE STATION FIELD OF THE INVENTION The present invention relates, in general, to the problem of the location of a mobile station ("MS") in a Public Mobile Land Network. { "PLMN"), and more specifically, to the problem of establishing the most accurate estimate of the last known position of the mobile station when the mobile station is off or has left the coverage area of the network.

RELATED TECHNIQUE Some commercial and regulatory needs are currently being developed to be able to use the Public Land Mobile Network ("PLMN") to geographically locate mobile stations ("MS"). An example of a PLMN is the GSM system ("Global System for Mobile Communications", Global System for Mobile Communications). A simplified scheme of a GSM system is shown in Figure la. There is a first mobile station 110 which is usually the only equipment that the subscriber sees of the entire system. The telephone of the subscribers, or terminal, is connected over a radio interface to the subsystem of the base station ("BSS") 120. Generally speaking, the subsystem of the base station 120 groups the infrastructure machines that are specific to each other. the cellular radio aspects of the GSM. The BSS 120 is in direct contact with the mobile stations through the radio interface. On the other hand, the BSS 120 is in contact with the switches of the Switching System ("SS", Switching System) 130. The function of the BSS 120 can be summarized to connect the mobile station 110 and the switching system 130, and by this means to the user of the mobile station with other telecommunications users. The BSS 120 has to be controlled and thus also be in contact with the Operation Sub-System ("OSS", Operating Subsystem) 140. The switching subsystem 130 includes the main switching functions of the GSM, as well as the databases necessary for subscriber data and mobility management. The main function of the switching subsystem is to handle communications between GSM users and other users of telecommunications networks. These other networks may include other PLMN 151, the PSTN (Public Switched Telephone Network) 152, CSPDN ("Circuit Switched Public Data Network", Public Network of Circuit Switched Data) 153, PSPDN (" Packet Switched Public Data Network ", Public Network of Data Switched in Packages) 154 and ISDN (" Integrated Services Digital Network ", Integrated Services Digital Network) 155. Within the SS, the basic switching function is performed by the Mobile Services Switching Center ("MSC", Mobile Services Switching Center) 131, whose main function is to coordinate the establishment of calls to and from GSM users. The MSC 131 has interfaces with the BSS 120 on the one hand, and with the external networks 150 on the other hand. However, direct connections between external networks 150 and a GSM system a [lacuna] routed through a Gateway-MSC ("GMSC", Compuertas Mobile Services Switching Center), which is not shown here. All incoming calls for a GSM / PLMN network will be routed to one or more of the GMSCs that function as an incoming transit exchange for the GSM / PLMN. In addition to the MSCs 131, the switching subsystem 130 includes databases. The relevant subscriber information for the provision of telecommunications services is maintained on the infrastructure side of the Home Location Register ("HLR"), regardless of the actual location of the subscriber. The HLR 132 also includes some information related to the current location of the subscriber. All telecommunications systems include a database that contains a variety of information related to each subscriber, such as the limitations of the subscription, subscribed services, cost information, etc. In a fixed network, each subscriber is connected to a local switch, for a long time. Each call that this subscriber implies goes through this switch. This is then the natural place to store the information related to the subscriber. In a system that handles mobile subscribers, there is no such natural place for storage. However, two kinds of data to be stored (location information and subscriber data) require a common storage solution. This is the choice that GSM makes, and the HLR 132 is the database for both series of information. If the location information is only necessary for the establishment of calls ending in mobile, the rest of the information is necessary at different times during any call. Basically, it is the Mobile Switching Center 131 visited the only one in charge of a mobile subscriber involved in a call, who needs these pieces of information. This would give rise to a substantial signaling load if the MSC 131 had to interrogate the HLR each time it needs any piece of information. To avoid this signaling load, a subscriber's data record is copied into a database close to MSC 131 while this subscriber is registered in a location-area ("LA") controlled by MSC 131. This base of data is the Visitor Location Register ("VLR", Visitor Location Register) 133. Information related to these subscribers that are registered under an MSC 131 connected to VLR 133 is stored in VLR 133 but only temporarily. This introduces new functions. The subscriber information has to be copied when the subscriber enters a new area of MSC / VLR. On the contrary, the corresponding record has to be deleted in the area of the previous MSC / VLR in which the subscriber was registered. This update of the databases is performed when certain events occur. These events include call set-up, transfers, full call, IMSI (International Mobile Subscriber Identity) attached (ie, when the mobile station is on) the separation of the IMSI (ie, when the mobile station) and update the location. As already mentioned, there is a growing demand for PLMN-based location development. It can be considered that the location based on PLMN consists of four parts: a Positioning Procedure (Location Procedure), a location gateway, applications and signaling mechanisms. The first of these four parts is a Positioning Procedure. This is a mechanism that is used in the network, for example, GSM, to search and report relative data, or in some absolute cases, about the location of the mobile station. There may be different positioning procedures in the network at the same time. These different positioning procedures can each have their own technical solutions and degrees of precision. The degrees of precision can be in the range from the entire service area of the PLMN down to 100 meters. However, in general, the greater the degree of accuracy, the higher the cost of the network in terms of signaling capacity and load. An example of this positioning procedure is the GPS, Global Positioning System (Global Positioning System). GPS is a satellite-based system where a mobile station must be equipped with a GPS terminal. The GPS terminal can determine its position by receiving signals from at least three satellites. The position of the mobile station can then be acquired by the application, for example, by polling the GPS terminal, after which the location information is sent over the network to the application.

Another possible positioning procedure is for the PLMN to measure the propagation time of the wave for the signal from the mobile station to a base station. The propagation time then corresponds to the position of the mobile station. The position of the MS can then be determined with certainty by repeating these measurements from two or more base stations. It is also known to determine the position of the mobile stations with the mobile station by making measurements on the signals from three base stations. The second part of the positioning based on PLMN is a positioning gate. In the present patent application this will be mentioned as a Mobile Positioning Center (MPC, Mobile Positioning Center) 170. The mobile positioning center uses the Positioning Procedure data, for example, GPS, to calculate the absolute position of the mobile phone. the mobile station and distribute the position information to the applications, as described below. The MPC 170 is connected to the PLMN by the Gateway Mobile Services Switching Center (GMSC, Gateway Mobile Services Switching Center). An example of a possible system using the mobile positioning center 170 is shown in Figure lb. The third part of the positioning based on the PLMN consists of the applications that are the users of the positioning information retrieved from the network. The applications send the positioning information request to the Mobile Positioning Center 170, which retrieves the network information in a method according to the present invention and then sends this positioning information about the application. Examples of applications may include: fleet management, emergency services such as ambulance, and location-dependent services such as the nearest fuel dispensing or perhaps the recovery of stolen vehicles, et cetera. The fourth part, and final, of a positioning system based on PLMN are the signaling mechanisms of the network. These are used to transfer the positioning data between the different elements used to determine the position of a mobile station. The positioning systems based on the infrastructure and the radio interface in a Public Land Mobile Network are not yet in the market. The only location information available in the current system when the mobile station is in "idle mode" is not very accurate. The inactive mode is the mode of the mobile station when it is simply listening to the transmission channels without having a channel of its own. In contrast to the "dedicated mode" where a bidirectional channel is assigned to the mobile station for its communication needs, allowing it to exchange point-to-point information with the infrastructure in both directions. The best known area in the current GSM when the MS is in idle mode is the location area (LA), which could be more than 100 kilometers wide. In future positioning systems there will be some ways to discover the location of a mobile station using different positioning procedures. The positioning procedure can be based on the terminal or based on the network. In a solution based on the terminal, it is the mobile stations that search and report relative positioning data to the Mobile Positioning Center for the calculation of the absolute position. In a network-based solution it is the Base Station System 110 that reports the data relative to the positioning center of the mobile 170. A positioning procedure can also be a combination of the terminal-based procedure and a procedure based on the network. Other positioning methods may consist of external equipment for positioning connected to the mobile station, for example GPS.

A problem that exists with these positioning procedures is based on the need to be able to locate the MS with a fairly good precision for the applications. This need requires that the network can establish contact with the mobile station. This means that the mobile station must be on and within the network coverage area. However, a problem occurs when the mobile station is off or has left the coverage area of the network. It is then impossible to have accurate information about where and when the last known position of the mobile station was. However, in these cases the best information available in the GSM, for example, is the location area. This precision is not very good for most applications and there is no mechanism to guarantee that the information is available in the system when the application requires it.

COMPENDIUM OF THE INVENTION The solution to the problem described above is to update the subscriber databases available in the system in a regular manner with accurate positioning data. The data can then be used to obtain the last known location of the mobile station when it can not be reached. The positioning data that is going to be stored is a matter of implementation. These can be, for example, cell identification or longitude and latitude as used in GPS. However, since the data will be stored for all mobile stations moving in the network, it is important to use a friendly implementation for the system that does not cause too much additional load that steals capacity from the network, but still offers a accuracy that is good enough for applications. In the preferred embodiment of the present invention as it is done in the GSM, there are two subscriber databases that will be updated. These are the Visitor Location Register (Registration of Visitor Location) 133 and the Home Location Register (Residence Location Register) 132. The visitor location record 133 is used for temporary storage while the residence location register 132 is used for permanent storage. The visitor location register 133 is updated when certain events occur that make position information available to the system. Since the VLR 133 is only used for temporary storage of the subscriber data, the positioning information must be transferred to the HLR 132 for permanent storage when the subscriber registration in the VLR 133 is going to be erased for some reason. A first application sends a request to the mobile Positioning Center requesting position information for a particular subscriber. The MPC contacts the preferred positioning procedure to obtain the positioning information. If this information is not available, then the MPC contacts the HLR to obtain the last known positioning data. The HLR will try to retrieve the last known positioning data from VLR and send it to the MPC. If this is not available, then the last known position stored in the HLR is sent to the MPC. The result of the present invention is that it becomes possible to obtain the last known location of a mobile station with good accuracy without stealing air interface or then the mobile station can not be reached by normal positioning procedures. This increases the positioning value for many applications. It is also possible for the PLMN operator to offer "previous" positioning data at a lower price given that the cost of obtaining the position is lower when compared to other "real-time" positioning procedures, since it is not necessary to establish contact with the mobile station.

Another benefit of the present invention is that the stored data can improve the location of mobile stations since the network can initiate paging or location in a specific cell instead of a whole area of complete location. Of course, this will decrease the signaling on the network in most cases.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will now be described in greater detail with reference to the preferred embodiments of the present invention, provided only by way of example, and illustrated in the accompanying drawings, in which: FIGURE la is a drawing of a mobile, cellular, GSM communications network. FIGURE Ib is a drawing of a mobile communications network, GSM cellular having a mobile positioning center. FIGURE 2 is a diagram illustrating the time of updating the VLR and the HLR. FIGURE 3 is a flowchart illustrating the method according to the present invention.

DETAILED DESCRIPTION The method of the present invention will be described in relation to the way it can be performed in a GSM system. It can be appreciated, however, that the present invention is also applicable to other mobile systems such as NMT, AMPS, etc. All mobile systems contain some kind of database where the subscriber information is stored, including the information related to the location of each subscriber. As already described, in the GSM this function of the database is divided between the visitor location record, where position information is only temporarily stored, and the residence location record, where information is stored for a long time. weather. This has been done to conserve signaling resources. However, in some mobile systems a single database could perform functions similar to those of the VLR and the HLR, depending on the implementation of the particular system. The present invention uses precise positioning data to regularly update the subscriber databases in the system. For GSM, the best, the instrumentation would be to use the Cell Global Identity ("CGl", Global Identity of the Cell), since this information is usually updated and used by the system for other purposes besides positioning, for example, the routing, etc. In this way they do not start or perform additional positioning to solve the problem. Thus, there is no substantial additional load on the system due to positioning. The CGl can be moved to an area corresponding to the coverage area of a specific cell. This offers a precision range from 100 meters to 35 kilometers RMS (that is, the sizes of the cell in GSM). This accuracy can be but, for example, if base stations with extended range are used. On the other hand the CGl can also be implemented with the Timing Advance ("TA", Advance of the Synchronization), when it is available, which increases the precision, since the TA can be translated in a distance to the base station. Because delays in propagation times for signals from different mobile stations increases as they move away from a base station, the risk of overlapping of their signals increases. The only solution is that the mobile station advances its signal emission in relation to its reception time, compensating by this means the delay of the propagation to and from. This value is called the advance of time. Although the main aspect of the present invention includes offering position information to different applications, it is necessary that the particular database or databases storing position information be updated. In GSM, of course, these are the visitor location register (VLR), which is used for temporary storage, and the residence location register (HLR), which is used for permanent storage. First, the positioning information, for example, the CGl, is stored in the VLR when certain events occur that make the information available in the system. If, for example, TA is used, it will also be sent for storage with the CGl. In addition to these, a date and time will also be sent to the VLR that will be stored to show the date and time when the information was retrieved. This information, for example, CGl, TA and the date and time, will be stored in the VLR when these events occur. These events include call set-up, transfers, complete calls, the joining of the IMSI (International Mobile Subscriber Identity) (that is, when the mobile station is on), the separation of the IMSI (ie, when the mobile station is turned off) and location updates. See Figure 2. Since the VLR is used only for temporary storage of subscriber data, it is necessary that the positioning information be transferred to the HLR for permanent storage when the subscriber registration in the VLR is to be erased for some reason. See Figure 2.

It will be necessary to make certain changes in the GSM system to implement the present invention. It will be necessary to create a new data field in the VLR and the HLR to store the position information (for example, CGl) and the date and time. In addition, it is possible to create other fields to store, for example, the advance of time. In addition, the system must be changed so that the positioning data is stored in important events. See Figure 2. It will also be necessary to change the signaling protocols to support the transfer of positioning data between different elements of the network. It will also be necessary to change the system so that the HLR is updated when the VLR is deleted for some reason. See Figure 2. In addition to the aforementioned changes, the mobile positioning center will have to be implemented. Probably this will be an external node dedicated to positioning management. However, it will be necessary to develop HLR interrogation methods through the MPC, in addition to the methods of communication between the MPC and the different external applications. The procedure in the previous paragraphs ensures that unnecessary signaling is not done in the network due to positioning. The invention can also be used as a Positioning Procedure when the application is satisfied with the poor precision given. It is probably cheaper to present "previous" positioning data instead of measuring the position in real time. When an application, for example, an emergency ambulance service, requests positioning information for an MS that can not be reached by the ordinary positioning procedure, for example GPS, the HLR checks whether it is possible to obtain information from the current VLR, if it exists, about the last known position. If this is not successful, the HLR sends back its last stored information to the application through the positioning gate. The application can then act and use this information in the best way in relation to the available date and time. Figure 3 illustrates this procedure in greater detail. The procedure begins when the application program requests the positioning information for a specific MS 300 from the Mobile Positioning Center ("MPC"). The MPC then makes contact with the preferred positioning procedure to obtain positioning information 310. The MPC then verifies whether it was possible to obtain some positioning information using the preferred positioning procedure 320. If the answer is yes, then the positioning data retrieved they are sent to the MPC for calculation 380. If the answer is no, then the MPC contacts the HLR to obtain the last known positioning data 330. First, the HLR checks if it has a valid VLR address 340. If the answer is no, then the last known positioning data is collected from the HLR 370 and this positioning data is sent to the MPC for the calculation 380. If the answer is yes, then the VLR is contacted to obtain the last known positioning data 350. Then check if any positioning data can be retrieved from the VLR 360. If so, then is the positioning data is sent to the MPC for the calculation 380. If it is not, then the last known positioning data is collected from the HLR 370, which is then sent to the MPC for the calculation 380. The modalities described above serve simply as illustration and not as a limitation. It will be apparent to those skilled in the art that it is possible to make deviations from the above-described embodiments without departing from the spirit and scope of the invention. The invention should not be considered as limited to the examples described, but should instead be considered as equal in scope to the following clauses.

Claims (19)

1. A method for determining the position of a mobile station in a mobile radio system for use in an application, the method includes the following steps: - signaling within the mobile radio system with the mobile station; - registering a first class of location information with a first time and date in a database, the first class of location information based on where they are receiving signals from the mobile radio system from the base station; - consult whether a preferred positioning procedure can be obtained; - retrieve the first class of location information from the database, if the preferred positioning procedure can not be obtained; and - send the first kind of location information to the application. The method of claim 1, wherein: the registration is made in a Visitor Location Register serving the mobile station. The method of claim 2, wherein: the first location information in the visitor location register is transferred to the residence location record for storage when a subscriber record containing information about the location is to be deleted. mobile station in the Location Registry of Visitor. The method of claim 3, wherein the step of recovering the first class of location information also includes the steps of: a Mobile Positioning Center by first contacting a residence location record with a visitor location registration address for the mobile station; if the address is valid then retrieve the last known position data in the visitor location record; and if the address is invalid then retrieve the last known position data in the residence location record. The method of claim 2, wherein: the first class of location data is recorded in the visitor location register when certain events occur that make the data available in the system. 6. The method of claim 5, wherein: the event is a Location Update. The method of claim 5, wherein: the event in a Cali Set-Up (Call Set-up). 8. The method of claim 5, wherein: the event is a Handover (Transfer). 9. The method of claim 5, wherein: the event is a Cali Complete (Complete Call). The method of claim 5, wherein: the event is an IMSI junction. The method of claim 5, wherein: the event is a separation from the IMSI. 1

2. The method of the preceding claims, wherein: the positioning information is the Global Cell Identity (Global Cell Identity). The method of the preceding claims, wherein: the positioning information is the location of the mobile station obtained by triangulating radio signals from the mobile station to the radio base stations in the mobile radio system. The method of the preceding claims, wherein: the positioning information includes a second time and date recording the time and date on which the information was retrieved. 15. An apparatus for determining the position of a mobile station in a mobile radio system for use in an application, is characterized by: a database for recording a first class of location information based on where the signals of the mobile station they are received in the mobile radio network; a means to recover the first kind of location information; and a means to send the first kind of location information to the application. 16. The apparatus of claim 15, further characterized in that: the database is a visitor location record. 17. The apparatus of claim 16, further characterized in that: the mobile radio system is a GSM system also having a residence location record.; and means for transferring the first class of location information to the residence location register serving the mobile station, when a subscriber record containing the first class of information can be deleted in the visitor location register. 18. The apparatus of claim 17, further characterized by: means for recovering the last known position data in the residence location register; and the means to retrieve the last known position data in the visitor location record. 19. The apparatus of claim 18, further characterized by: means for storing the first location class in the visitor location record when certain events occur that make the data available in the system.