U.S. patent application number 09/063028 was filed with the patent office on 2001-08-16 for system and method for provisioning assistance global positioning system information to a mobile station.
Invention is credited to KINGDON, CHRISTOPHER H., KRANSMO, JAN LENNART, ZADEH, BAGHER R..
Application Number | 20010014604 09/063028 |
Document ID | / |
Family ID | 22046434 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014604 |
Kind Code |
A1 |
KINGDON, CHRISTOPHER H. ; et
al. |
August 16, 2001 |
SYSTEM AND METHOD FOR PROVISIONING ASSISTANCE GLOBAL POSITIONING
SYSTEM INFORMATION TO A MOBILE STATION
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.
Inventors: |
KINGDON, CHRISTOPHER H.;
(GARLAND, TX) ; ZADEH, BAGHER R.; (DALLAS, TX)
; KRANSMO, JAN LENNART; (PLANO, TX) |
Correspondence
Address: |
THOMAS L CRISMAN
JENKENS & GILCHRIST
3200 FOUNTAIN PLACE
1445 ROSS AVENUE
DALLAS
TX
752022799
|
Family ID: |
22046434 |
Appl. No.: |
09/063028 |
Filed: |
April 20, 1998 |
Current U.S.
Class: |
455/427 ;
455/12.1; 455/429 |
Current CPC
Class: |
G01S 19/06 20130101;
H04W 84/042 20130101; G01S 19/07 20130101; H04W 84/06 20130101;
G01S 19/071 20190801; H04W 64/00 20130101; G01S 2205/008 20130101;
H04W 88/14 20130101 |
Class at
Publication: |
455/427 ;
455/429; 455/12.1 |
International
Class: |
H04Q 007/20 |
Claims
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.
Description
BACKGROUND OF THE PRESENT INVENTION
[0001] 1. Field of the Invention
[0002] 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.
[0003] 2. Background and Objects of the Present Invention
[0004] 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.
[0005] With reference now to FIG. 1 of the drawings, there is
illustrated a GSM Public Land Mobile Network (PLMN), such as
cellular network 10, which in turn is composed of a plurality of
areas 12, each with a Mobile Switching Center (MSC) 14 and an
integrated Visitor Location Register (VLR) 16 therein. The MSC/VLR
areas 12, in turn, include a plurality of Location Areas (LA) 18,
which are defined as that part of a given MSC/VLR area 12 in which
a mobile station (MS) (terminal) 20 may move freely without having
to send update location information to the MSC/VLR area 12 that
controls the LA 18. Each Location Area 18 is divided into a number
of cells 22. Mobile Station (MS) 20 is the physical equipment,
e.g., a car phone or other portable phone, used by mobile
subscribers to communicate with the cellular network 10, each
other, and users outside the subscribed network, both wireline and
wireless.
[0006] The MSC 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 the cell 22 for which it is
responsible. It should be understood that the BSC 23 may be
connected to several BTS's 24, and may be implemented as a
stand-alone node or integrated with the MSC 14. In either event,
the BSC 23 and BTS 24 components, as a whole, are generally
referred to as a Base Station System (BSS) 25.
[0007] With further reference to FIG. 1, the PLMN Service Area or
cellular network 10 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 that PLMN 10. The
HLR 26 may be co-located with a given MSC 14, integrated with the
MSC 14, or alternatively can service multiple MSCs 14, the latter
of which is illustrated in FIG. 1.
[0008] The VLR 16 is a database containing information about all of
the MS's 20 currently located within the MSC/VLR area 12. If an MS
20 roams into a new MSC/VLR area 12, the VLR 16 connected to that
MSC 14 requests data about that MS 20 from the HLR database 26
(simultaneously informing the HLR 26 about the current location of
the MS 20). Accordingly, if the user of the MS 20 then wants to
make a call, the local VLR 16 will have the requisite
identification information without having to reinterrogate the HLR
26. In the aforedescribed manner, the VLR and HLR databases 16 and
26, respectively, contain various subscriber information associated
with a given MS 20.
[0009] Determining the geographical position of a MS 20 within a
cellular network 10 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 the mobile terminal 20 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.
[0010] 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.
[0011] 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.
[0012] 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 mobile terminal 20, 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 the MS 20 location, to the GPS receiver within or attached to
the MS 20 quickly.
[0013] 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.
SUMMARY OF THE INVENTION
[0014] 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.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] 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:
[0016] FIG. 1 is a block diagram of a conventional
terrestrially-based wireless telecommunications system;
[0017] 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
[0018] FIG. 3 demonstrates steps in a sample positioning of a
mobile terminal using GPS in accordance with preferred embodiments
of the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY
EMBODIMENTS
[0019] 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.
[0020] 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) 250 requests positioning of a
Mobile Station (MS) 200 within a Public Land Mobile Network (PLMN)
290 (step 300), the positioning request is forwarded to a Mobile
Location Center 240 serving the PLMN 290 (step 310). It should be
noted that the LA 250 can be an external node, within the cellular
PLMN network 290, or within the MS 200 itself. Thereafter, the MLC
240 requests, from a Mobile Switching Center/Visitor Location
Register (MSC/VLR) 230 serving the area that the MS 200 is in, the
cell ID corresponding to a cell 295 that the MS 200 is currently
located in (step 320). If the MS 200 is in idle mode, e.g., not in
use, the MLC 240 can then instruct the MSC/VLR 230 to page the MS
200 via a Base Station Controller (BSC) 220 and a serving Base
Transceiver Station (BTS) 210 to determine the cell ID for the cell
295 that the MS 200 is located in (step 320). This cell ID is then
sent back to the MLC 240 from the MSC/VLR 230 (step 330). If,
however, the MS 200 is in busy mode, e.g., in use, the cell ID
information is already known by the MSC/VLR 230 (step 320) and is
sent by the MSC/VLR 230 to the MLC 240 (step 330), upon
request.
[0021] Once the MLC 240 receives the cell ID from the MSC/VLR 230
(step 330), the MLC 240 can determine the coordinates of the
serving BTS 210 (step 340), which preferably serves as the local
position estimate for the MS 200, and from this information, using,
for example, a look-up table 245, the MLC 240 can determine a
reference GPS receiver 260 (step 350), which is valid for the cell
295 that the MS 200 is located in. Alternatively, the MLC 240 can
determine the correct reference GPS receiver 260 (step 350) just
from the cell ID, using another look-up table 245. In addition,
alternative ways of determining the correct reference GPS receiver
260 (step 350) can be used instead of the look-up table 245
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 receiver 260 (step 350).
[0022] Multiple reference GPS receivers 260 and 270 are spaced
throughout the PLMN 290 in order to provide accurate assistance GPS
data to GPS receivers 205 within or attached to MS's 200. This data
is used by the built-in GPS receiver 205 to determine the location
of the MS 200 within the PLMN 290. The data in each reference GPS
receiver 260 and 270 is valid in a radius of up to 300 kilometers
around the reference GPS receiver 260 and 270 site (except for
differential correction information, which is only valid for a
radius of up to 50 kilometers), and therefore, the correct
reference GPS receiver 260 for the cell 295 that the MS 200 is in
must be determined to ensure the accuracy of the assistance GPS
data. In addition, each reference GPS receiver 260 and 270 must be
placed such that the antenna has an unobstructed view of the full
sky.
[0023] After the MLC 240 has determined the correct reference GPS
receiver 260 (step 350), the MLC 240 then obtains, from the
reference GPS receiver 260, the relevant assistance GPS data (step
360), such as the identity of the visible satellites 280, the
orbital parameters of the satellites 280, clock corrections and
differential corrections. A current requirement is that this
assistance data to be updated by the reference GPS receivers 260
and 270 about every thirty minutes (except for differential
corrections, which are updated about every five seconds).
[0024] In alternative embodiments, the differential corrections can
be sent from the correct reference GPS receiver 260 to the MLC 240
and then be forwarded to the serving BTS 210 for that cell 295 to
be broadcast on, for example, a Broadcast Control Channel (BCCH),
to MS's 200 within the cell 295 about every five seconds.
Therefore, this information does not need to be collected by the
MLC 240 when a positioning request comes in and then subsequently
sent to the MS 200 to be positioned, which could take more than
five seconds. Advantageously, by continuously broadcasting the
differential corrections every five seconds, the MS 200 will always
have updated differential correction information.
[0025] The MLC 240 can collect the assistance GPS data (step 360)
by querying the correct reference GPS receiver 260 for the latest
assistance GPS data when a positioning request comes in.
Alternatively, each reference GPS receiver 260 and 270 within the
PLMN 290 can update the MLC 240, e.g., every thirty minutes, and
store, within a database 248 within the MLC 240, the current
assistance GPS data for that reference GPS receiver 260 and 270.
Thus, when a positioning request comes in, the MLC 240 need only
access that stored information associated with the correct
reference GPS receiver 260 when the correct reference GPS receiver
260 is ascertained (step 350). In either case, once the current
assistance GPS data is obtained by the MLC 240 (step 360), this
information is forwarded to the built-in or attached GPS receiver
205 within the MS 200 (step 370) via the MSC/VLR 230, BSC 220 and
BTS 210. For example, the current assistance data can be sent to
the MS 200 (step 370) within a Short Message Service (SMS)
message.
[0026] Using this assistance GPS data, the built-in GPS receiver
205 within the MS 200 can calculate its position (step 380), e.g.,
latitude and longitude, and send this location information back to
the MLC 240 (step 390), in, for example, an SMS message.
Thereafter, the MLC 240 can forward the location of the MS 200 to
the requesting Location Application (LA) 250 (step 395).
[0027] Advantageously, by providing the MS 200 with an integrated
GPS receiver 205 and the necessary assistance GPS data, the
integrated GPS receiver 205 can calculate its position (step 380)
relatively quickly. Without this information, a GPS receiver 270
typically requires approximately 15 seconds to 30 minutes. However,
with the provisioning of the assistance GPS data to the GPS
receiver 205 within the MS 200 through the cellular network 290
(step 370), positioning (step 380) can potentially be performed
within about 5 seconds. In addition, the accuracy of the MS 200
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.
[0028] 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.
[0029] 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.
[0030] 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.
* * * * *