US20010014604A1 - System and method for provisioning assistance global positioning system information to a mobile station - Google Patents

Abstract

A telecommunications system and method is disclosed for provisioning assistance Global Position System (GPS) data to a GPS receiver within a mobile terminal. This can be accomplished by having multiple reference GPS receivers located throughout a cellular network, each reference GPS receiver being capable of providing locally valid lists of visible satellites and the associated ephemeris and clock correction information. The location of the Base Transceiver Station (BTS) within the cell that the mobile terminal with a built-in or attached GPS receiver is currently located in can be used as the local position estimate for that mobile terminal. From this local position estimate, the nearest reference GPS receiver can be ascertained and the relevant assistance data can then be sent to the GPS receiver within the mobile terminal through the cellular network to enable the built-in GPS receiver to calculate its position relatively quickly.

Description

BACKGROUND OF THE PRESENT INVENTION
• 1. Field of the Invention[0001]
• The present invention relates generally to telecommunications systems and methods for implementing Global Positioning System (GPS) receivers within mobile terminals, and specifically to provisioning GPS assistance information to GPS receivers within or attached to mobile terminals.[0002]
• 2. Background and Objects of the Present Invention[0003]
• Cellular telecommunications is one of the fastest growing and most demanding telecommunications applications ever. Today it represents a large and continuously increasing percentage of all new telephone subscriptions around the world. A standardization group, European Telecommunications Standards Institute (ETSI), was established in 1982 to formulate the specifications for the Global System for Mobile Communication (GSM) digital mobile cellular radio system.[0004]
• With reference now to FIG. 1 of the drawings, there is illustrated a GSM Public Land Mobile Network (PLMN), such as[0005]cellular network10, which in turn is composed of a plurality ofareas12, each with a Mobile Switching Center (MSC)14 and an integrated Visitor Location Register (VLR)16 therein. The MSC/VLR areas12, in turn, include a plurality of Location Areas (LA)18, which are defined as that part of a given MSC/VLR area12 in which a mobile station (MS) (terminal)20 may move freely without having to send update location information to the MSC/VLR area12 that controls theLA18. EachLocation Area18 is divided into a number ofcells22. Mobile Station (MS)20 is the physical equipment, e.g., a car phone or other portable phone, used by mobile subscribers to communicate with thecellular network10, each other, and users outside the subscribed network, both wireline and wireless.
• The MSC[0006]14 is in communication with at least one Base Station Controller (BSC)23, which, in turn, is in contact with at least one Base Transceiver Station (BTS)24. The BTS is the physical equipment, illustrated for simplicity as a radio tower, that provides radio coverage to thecell22 for which it is responsible. It should be understood that theBSC23 may be connected to several BTS's24, and may be implemented as a stand-alone node or integrated with theMSC14. In either event, theBSC23 and BTS24 components, as a whole, are generally referred to as a Base Station System (BSS)25.
• With further reference to FIG. 1, the PLMN Service Area or[0007]cellular network10 includes a Home Location Register (HLR)26, which is a database maintaining all subscriber information, e.g., user profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information, for subscribers registered within thatPLMN10. The HLR26 may be co-located with a givenMSC14, integrated with theMSC14, or alternatively can servicemultiple MSCs14, the latter of which is illustrated in FIG. 1.
• The[0008]VLR16 is a database containing information about all of the MS's20 currently located within the MSC/VLR area12. If anMS20 roams into a new MSC/VLR area12, theVLR16 connected to thatMSC14 requests data about thatMS20 from the HLR database26 (simultaneously informing theHLR26 about the current location of the MS20). Accordingly, if the user of theMS20 then wants to make a call, thelocal VLR16 will have the requisite identification information without having to reinterrogate theHLR26. In the aforedescribed manner, the VLR andHLR databases16 and26, respectively, contain various subscriber information associated with a givenMS20.
• Determining the geographical position of a[0009]MS20 within acellular network10 has recently become important for a wide range of applications. For example, positioning services may be used by transport and taxi companies to determine the location of their vehicles. In addition, for emergency calls, e.g., 911 calls, the exact location of themobile terminal20 may be extremely important to the outcome of the emergency situation. Furthermore, positioning services can be used to determine the location of a stolen car, for the detection of home zone calls, which are charged at a lower rate, for the detection of hot spots for micro cells, or for the subscriber to determine, for example, the nearest gas station, restaurant, or hospital, e.g., Where am I service.
• One known solution of locating an object is the Global Positioning System (GPS). GPS is a well-known technology used by many military and civilian applications. It is based upon a constellation of satellites launched by the U.S. government beginning in 1978. The GPS satellites transmit the standard positioning service (SPS) signal, which is available for civilian applications, on a 1575.42 MegaHertz carrier. Each satellite uses a unique 1023-chip Gold code at a rate of 1.023 MegaHertz, such that all codes repeat at 1 millisecond intervals.[0010]
• Each satellite also transmits a unique 50 bit/second navigation message containing parameters that allow GPS receivers on earth to compute a precise position solution. The navigation message includes a precise time reference as well as parameters that precisely describe the orbital positions and clock corrections for the satellites. In general, GPS receivers compute a position solution by searching for all visible satellites, which can be accomplished by correlating the received signal with replicas of the respective Gold codes, demodulating the navigation message of each visible satellite to obtain a time reference and orbital position, computing a range estimate for each visible satellite that includes the GPS receiver clock uncertainty, and, if at least four satellites are visible, computing the GPS receiver position and clock correction using the range estimate.[0011]
• The duration of the GPS positioning process is directly dependent upon how much information the GPS receiver has. Most GPS receivers are programmed with almanac data, which coarsely describes the satellite positions for one year. However, if the GPS receiver does not have some knowledge of its own approximate location, then the GPS receiver cannot correlate signals from the visible satellites quickly, and therefore, cannot calculate its position quickly. Thus, in order to implement a GPS receiver effectively within a[0012]mobile terminal20, in order to meet demands for expedited and accurate positioning, e.g., FCC phase II E-911 service, there must be some way to provide this type of accurate assistance data, e.g., local time and position estimates and satellite ephemeris and clock information, which varies according to theMS20 location, to the GPS receiver within or attached to the MS20 quickly.
• It is, therefore, an object of the present invention to send the necessary assistance GPS information over the existing wireless network to the GPS receiver within the mobile terminal.[0013]
SUMMARY OF THE INVENTION
• The present invention is directed to telecommunications systems and methods for provisioning assistance Global Position System (GPS) data to a GPS receiver within a mobile terminal. This can be accomplished by having multiple reference GPS receivers located throughout the cellular network, each reference GPS receiver being capable of providing locally valid lists of visible satellites and the associated ephemeris and clock correction information. This data from each reference GPS receiver is valid for a radius of up to 300 kilometers around the reference GPS receiver site. However, if a differential GPS solution is utilized, the data for the GPS receiver is only valid for a radius of up to 50 kilometers. The location of the Base Transceiver Station within the cell that the mobile terminal with a built-in GPS receiver is currently located in can be used as the local position estimate for that mobile terminal. From this local position estimate, the nearest reference GPS receiver can be ascertained and the relevant assistance data can then be sent to the GPS receiver within the mobile terminal through the cellular network to enable the built-in GPS receiver to calculate its position relatively quickly. Advantageously, compared with previous solutions, the accuracy of the position of the mobile terminal using a GPS receiver can be reduced to a 5 meter radius (using differential correction information), instead of a cell radius (500 meters to 35 kilometers) or a location area radius, as in previous solutions.[0014]
BRIEF DESCRIPTION OF THE DRAWINGS
• The disclosed inventions will be described with reference to the accompanying drawings, which show sample embodiments of the invention and which are incorporated in the specification hereof by reference, wherein:[0015]
• FIG. 1 is a block diagram of a conventional terrestrially-based wireless telecommunications system;[0016]
• FIG. 2 illustrates positioning of a mobile terminal within a cellular network using the Global Positioning System (GPS) in accordance with preferred embodiments of the present invention; and[0017]
• FIG. 3 demonstrates steps in a sample positioning of a mobile terminal using GPS in accordance with preferred embodiments of the present invention.[0018]
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS
• The numerous innovative teachings of the present application will be described with particular reference to the presently preferred exemplary embodiments. However, it should be understood that this class of embodiments provides only a few examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily delimit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others.[0019]
• With reference now to FIG. 2 of the drawings, which will be described in connection with FIG. 3 of the drawings, when a requesting Location Application (LA)[0020]250 requests positioning of a Mobile Station (MS)200 within a Public Land Mobile Network (PLMN)290 (step300), the positioning request is forwarded to aMobile Location Center240 serving the PLMN290 (step310). It should be noted that theLA250 can be an external node, within thecellular PLMN network290, or within theMS200 itself. Thereafter, theMLC240 requests, from a Mobile Switching Center/Visitor Location Register (MSC/VLR)230 serving the area that the MS200 is in, the cell ID corresponding to acell295 that the MS200 is currently located in (step320). If the MS200 is in idle mode, e.g., not in use, theMLC240 can then instruct the MSC/VLR230 to page the MS200 via a Base Station Controller (BSC)220 and a serving Base Transceiver Station (BTS)210 to determine the cell ID for thecell295 that the MS200 is located in (step320). This cell ID is then sent back to theMLC240 from the MSC/VLR230 (step330). If, however, the MS200 is in busy mode, e.g., in use, the cell ID information is already known by the MSC/VLR230 (step320) and is sent by the MSC/VLR230 to the MLC240 (step330), upon request.
• Once the[0021]MLC240 receives the cell ID from the MSC/VLR230 (step330), theMLC240 can determine the coordinates of the serving BTS210 (step340), which preferably serves as the local position estimate for theMS200, and from this information, using, for example, a look-up table245, theMLC240 can determine a reference GPS receiver260 (step350), which is valid for thecell295 that theMS200 is located in. Alternatively, theMLC240 can determine the correct reference GPS receiver260 (step350) just from the cell ID, using another look-up table245. In addition, alternative ways of determining the correct reference GPS receiver260 (step350) can be used instead of the look-up table245 described herein. Alternatively, certain countries may have regulations against transmitting cell-site location information. In this case, the local position estimate can be quantized to approximately 1 kilometer granularity, which can then be used to determine the correct reference GPS receiver260 (step350).
• Multiple[0022]reference GPS receivers260 and270 are spaced throughout thePLMN290 in order to provide accurate assistance GPS data toGPS receivers205 within or attached to MS's200. This data is used by the built-inGPS receiver205 to determine the location of theMS200 within thePLMN290. The data in eachreference GPS receiver260 and270 is valid in a radius of up to 300 kilometers around thereference GPS receiver260 and270 site (except for differential correction information, which is only valid for a radius of up to 50 kilometers), and therefore, the correctreference GPS receiver260 for thecell295 that theMS200 is in must be determined to ensure the accuracy of the assistance GPS data. In addition, eachreference GPS receiver260 and270 must be placed such that the antenna has an unobstructed view of the full sky.
• After the[0023]MLC240 has determined the correct reference GPS receiver260 (step350), theMLC240 then obtains, from thereference GPS receiver260, the relevant assistance GPS data (step360), such as the identity of thevisible satellites280, the orbital parameters of thesatellites280, clock corrections and differential corrections. A current requirement is that this assistance data to be updated by thereference GPS receivers260 and270 about every thirty minutes (except for differential corrections, which are updated about every five seconds).
• In alternative embodiments, the differential corrections can be sent from the correct[0024]reference GPS receiver260 to theMLC240 and then be forwarded to the servingBTS210 for thatcell295 to be broadcast on, for example, a Broadcast Control Channel (BCCH), to MS's200 within thecell295 about every five seconds. Therefore, this information does not need to be collected by theMLC240 when a positioning request comes in and then subsequently sent to theMS200 to be positioned, which could take more than five seconds. Advantageously, by continuously broadcasting the differential corrections every five seconds, theMS200 will always have updated differential correction information.
• The[0025]MLC240 can collect the assistance GPS data (step360) by querying the correctreference GPS receiver260 for the latest assistance GPS data when a positioning request comes in. Alternatively, eachreference GPS receiver260 and270 within thePLMN290 can update theMLC240, e.g., every thirty minutes, and store, within adatabase248 within theMLC240, the current assistance GPS data for thatreference GPS receiver260 and270. Thus, when a positioning request comes in, theMLC240 need only access that stored information associated with the correctreference GPS receiver260 when the correctreference GPS receiver260 is ascertained (step350). In either case, once the current assistance GPS data is obtained by the MLC240 (step360), this information is forwarded to the built-in or attachedGPS receiver205 within the MS200 (step370) via the MSC/VLR230,BSC220 andBTS210. For example, the current assistance data can be sent to the MS200 (step370) within a Short Message Service (SMS) message.
• Using this assistance GPS data, the built-in[0026]GPS receiver205 within theMS200 can calculate its position (step380), e.g., latitude and longitude, and send this location information back to the MLC240 (step390), in, for example, an SMS message. Thereafter, theMLC240 can forward the location of theMS200 to the requesting Location Application (LA)250 (step395).
• Advantageously, by providing the[0027]MS200 with anintegrated GPS receiver205 and the necessary assistance GPS data, theintegrated GPS receiver205 can calculate its position (step380) relatively quickly. Without this information, aGPS receiver270 typically requires approximately 15 seconds to 30 minutes. However, with the provisioning of the assistance GPS data to theGPS receiver205 within theMS200 through the cellular network290 (step370), positioning (step380) can potentially be performed within about 5 seconds. In addition, the accuracy of theMS200 location can be improved to a radius of about 5 meters with the differential correction information, instead of the radius of a cell (500 m to 35 km radius) or a location area, as in previous solutions.
• As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a wide range of applications. Accordingly, the scope of patented subject matter should not be limited to any of the specific exemplary teachings discussed.[0028]
• For example, it should be noted that the location services can be used by applications located-in or connected-to the subscriber's MS, by network applications or by external applications.[0029]
• Furthermore, it should be understood that the positioning systems and methods disclosed herein can be utilized by any cellular network, including, but not limited to the Global System for Mobile Communications (GSM) network, the Personal Communications Systems (PCS) network, the AMPS network and the D-AMPS network.[0030]

Claims (20)

What is claimed is:

1. A telecommunications system for determining the location of a mobile terminal within a cellular network by provisioning a correct one of a plurality of assistance data to a Global Positioning System receiver connected to said mobile terminal, said telecommunications system comprising:

a plurality of reference Global Positioning System receivers within said telecommunications system, each said reference Global Positioning System receiver having a respective one of said assistance data therein; and

a mobile location center connected to said reference Global Positioning System receivers and in wireless communication with said mobile terminal, said mobile location center determining a correct one of said reference Global Positioning System receivers, said correct Global Positioning System receiver sending said correct assistance data to said mobile location center, said mobile location center sending said correct assistance data to said Global Positioning System receiver connected to said mobile terminal for calculation of the location of said mobile terminal.

2. The telecommunications system of

claim 1

, wherein said mobile terminal is located within a cell in said cellular network, said cell having a cell ID associated therewith, said mobile location center determining said correct reference Global Positioning System receiver using said cell ID.

3. The telecommunications system of

claim 2

, wherein said mobile location center has a list of coordinates stored therein, each of said coordinates having an associated one of said reference Global Positioning System receivers, said mobile location center finding a correct one of said coordinates within said list of coordinates, using said cell ID, said correct reference Global Positioning System receiver being said reference Global Positioning System receiver associated with said correct coordinates.

4. The telecommunications system of

claim 3

, further comprising a base station in wireless communication with said mobile terminal and in communication with said mobile location center, said correct coordinates being associated with the location of said base station.

5. The telecommunications system of

claim 1

, wherein said mobile location center determines said correct reference Global Positioning System receiver when said mobile location center receives a positioning request from a location node.

6. The telecommunications system of

claim 5

, wherein the location of said mobile terminal is sent from said mobile terminal to said location node.

7. The telecommunications system of

claim 1

, wherein said correct assistance data is sent from said mobile location center to said Global Positioning System receiver connected to said mobile terminal via a mobile switching center connected to said mobile location center, and a base station connected to said mobile switching center and in wireless communication with said mobile terminal, said Global Positioning System receiver being located within said mobile terminal.

8. The telecommunications system of

claim 1

, wherein said mobile location center has a database therein, said correct reference Global Positioning System receiver sending said correct assistance data to said mobile location center periodically, said correct assistance data being stored in said database.

9. The telecommunications system of

claim 1

, wherein said correct assistance data is sent to said Global Positioning System receiver connected to said mobile terminal in a Short Message Service message, the location of said mobile terminal being sent from said moible terminal to said mobile location center in an additional Short Message Service message.

10. The telecommunications system of

claim 1

, wherein said assistance data comprises the number of visible satellites, the orbital parameters associated with each said visible satellite, clock correction information and differential correction information.

11. A method for determining the location of a mobile terminal within a cellular network by provisioning a correct one of a plurality of assistance data to a Global Positioning System receiver connected to said mobile terminal, said method comprising the steps of:

determining, by a mobile location center connected to a plurality of reference Global Positioning System receivers, a correct one of said reference Global Positioning System receivers within said cellular network, each said reference Global Positioning System receiver having a respective one of said assistance data therein;

sending, by said correct reference Global Positioning System receiver, said correct assistance data to said mobile location center;

sending, by said mobile location center, said correct assistance data to said Global Positioning System receiver connected to said mobile terminal; and

calculating, by said Global Positioning System receiver connected to said mobile terminal, the location of said mobile terminal.

12. The method of

claim 11

, wherein said mobile terminal is located within a cell in said cellular network, said cell having a cell ID associated therewith, said step of determining said correct reference Global Positioning System receiver being performed using said cell ID.

13. The method of

claim 12

, wherein said mobile location center has a list of coordinates stored therein, each of said coordinates having an associated one of said reference Global Positioning System receivers, said step of determining said correct reference Global Positioning System receiver being performed by said mobile location center finding a correct one of said coordinates within said list of coordinates, using said cell ID, said correct reference Global Positioning System receiver being said reference Global Positioning System receiver associated with said correct coordinates.

14. The method of

claim 13

, wherein said correct coordinates are associated with the location of a base station in wireless communication with said mobile terminal and in communication with said mobile location center.

15. The method of

claim 11

, further comprising, before said step of determining said correct reference Global Positioning System receiver, the step of:

receiving, by said mobile location center, a positioning request from a location node.

16. The method of

claim 15

, further comprising, after said step of calculating, the steps of:

sending, by said mobile terminal, the location of said mobile terminal to said mobile location center; and

sending, by said mobile location center, the location of said mobile terminal to said location node.

17. The method of

claim 11

, wherein said step of sending said correct assistance data from said mobile location center to said Global Positioning System receiver connected to said mobile terminal is performed by sending said correct assistance data via a mobile switching center connected to said mobile location center, and a base station connected to said mobile switching center and in wireless communication with said mobile terminal, said Global Positioning System receiver being located within said mobile terminal.

18. The method of

claim 11

, wherein said mobile location center has a database therein, said step of sending said correct assistance data from said correct reference Global Positioning System receiver to said mobile location center being performed by sending said correct assistance data periodically and storing said correct assistance data in said database.

19. The method of

claim 11

, wherein said step of sending said correct assistance data to said Global Positioning System receiver connected to said mobile terminal is performed by sending said correct assistance data in a Short Message Service message, and further comprising, after said step of calculating, the step of:

sending, by said mobile terminal, the location of said mobile terminal to said mobile location center in an additional Short Message Service message.

20. The method of

claim 11

, wherein said assistance data comprises the number of visible satellites, the orbital parameters associated with each said visible satellite, clock correction information and differential correction information.

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