EP0874248A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Rapid and precise geolocation of cellular telephones through the use of the GPS satellite system
Assignee: Lockheed Martin Corp
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Filing: 1998-04-24
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Granted: —
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Expires: 2018-04-24
Abstract
Abstract A system to reduce the acquisition time necessary to access a GPS signal used to deterrffine the positional coordinates of a user associated with a wireless communications system. A wireless communications system can provide telephony and data service to mobile users throughout a large area. The wireless communications system provides transmissions and reception in a plurality of spotbeams or cells (17, 18, 19) comprising the large area. Each spotbeam or cell may be very large, up to 1500 km. in diameter for some satellite based systems, which precludes determining the subscribers precise location from his spotbeam ID or cell ID alone. With this invention, the wireless network broadcasts to user terminals within each spotbeam or cell, the GPS ID of all satellites that are visible within the zone along with Doppler and signal strength estimates for the visible GPS satellites. The user terminal (20) has a GPS receiver which is capable of receiving the C/A codes from the GPS satellites. The user terminal uses the broadcast GPS aiding data to quickly acquire the GPS C/A signals for all visible GPS satellites (14, 15, 16). The user terminal then returns the GPS C/A code measurements to the wireless network (24, 25, 11) which processes the measurements in conjunction with separate GPS data which it also receives to determine the users location. This precludes the user terminal from having to perform all the functions necessary to compute the geolocation. In this manner, the location of the user can be rapidly determined while reducing the cost of the user terminal.
Inventors
- 👤 James Llewellyn Myers, Jr.
- 👤 Stuart Chattan Shaw
- 👤 Stephen Ralph Mcreynolds
- 👤 Laurence D. Pike
- 👤 David Ii Lawrence
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 11:43
CPC Classifications
G; G01; G01S; G01S19/00; G01S19/01; G01S19/03; G01S19/08; G01S19/07; G01S19/071; G01S19/13; G01S19/24; G01S19/25; G01S19/254; H; H04; H04B; H04B7/00; H04B7/14; H04B7/15; H04B7/185; H04B7/1853; H04B7/18545; H04B7/18547; H04B7/1855; H04B7/18552
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
183 words
A method for obtaining geolocation data of a user terminal within a designated
spatial area, the user terminal being part of a cellular network controlled by a central site for
transmitting to and receiving from user terminals in that area, and a satellite positioning
system for transmitting geolocation data, comprising the steps of obtaining and processing information from the satellite positioning system at the
central site to generate aiding data for said user terminal; obtaining for processing at the usual terminal aiding data transmitted from the central
site; calculating precise timing and differential data at the user terminal using both (a)
locally-obtained C/A code spread signal data from the satellite positioning system and (b) the
aiding data from the central site; obtaining for processing at the central site, the coarse location data and the timing and
differential data from the user terminal; and combining and processing data from the satellite positioning system, along with the
coarse location data and timing and differential data from the user terminal, to provide an
accurate indication of the location of the user terminal within the spatial area.
Claim 2
Dependent Claim
17 words
The method according to claim 1, wherein the satellite positioning system is
the Global Positioning System (GPS).
Claim 3
Dependent Claim
13 words
The method according to claim 1, wherein the said cellular network is
wireless.
Claim 4
Dependent Claim
43 words
The method according to claim 3, wherein the cellular network is at least
one of: a Mobile Satellite System (MSS); a Base Transceiver Station(BTS) used with a
terrestrial cellular network; and an Aeronautical Transceiver Station (ATS) used with a
balloon based cellular network.
Claim 5
Dependent Claim
31 words
The method according to claim 1, wherein the user terminal is a Multi-mode
Wireless Terminal (MWT), wherein one mode is the satellite positioning system and
another mode is the cellular network.
Claim 6
Dependent Claim
61 words
The method according to claim 1, wherein aiding data is at least one of:
identification of GPS satellites which should be within the field of view of the user terminal;
Doppler frequency offset for each identified satellite; tolerance of the Doppler data for each
identified satellite; estimated signal strength for each identified satellite; and GPS epoch
relative to cellular network time.
Claim 7
Dependent Claim
77 words
The method according to claim 1, wherein the timing and differential
data includes at least one of: a local timestamp for the all differential data received; a delta
for each satellite acquired between the local timestamp and a first chip in the GPS Coarse
Acquistion (C/A) code for the acquired GPS satellite, measured in whole and fractional chips;
and a local time stamp corresponding to a point in the transmissions process after which all
latency is predictable.
Claim 8
Dependent Claim
38 words
The method according to claim 7 wherein the timing and differential
data further includes a delta for each satellite acquired between the local time stamp and the
beginning of a data bit in the satellite positioning system message.
Claim 9
Dependent Claim
26 words
The method according to claim 1, further including the step of storing
data indicative of a catalog of the latest GPS ephemeris at the central site.
Claim 10
Dependent Claim
34 words
The method according to claim 9 wherein the network has a plurality
of spatial areas and further including the step of maintaining the catalog of the aiding data on
a per spatial area basis.
Claim 11
Dependent Claim
40 words
The method according to claim 5 further including the steps of:
calculating all possible three-dimensional geolocation solutions given the time and
differential data provided by the MWT; and using the elevation of the resulting calculated
geolocations to eliminate invalid solutions.
Claim 12
Dependent Claim
32 words
The method according to claim 11, further including the step of
reducing the set of valid solutions to a single solution by determining which solution
conforms to an identified bit synchronization differential.
Claim 13
Dependent Claim
173 words
Apparatus useable in a wireless cellular system for obtaining
geolocation information from a geolocation satellite system to determine the location of a
user within said cellular system, as monitored by an associated central site for receiving data
from and transmitting data to a user terminal, comprising; receiving means associated with said user terminal for receiving information
both from a plurality of said GPS satellites, and from said cellular network; means associated with each user terminal for processing said received
information and for transmitting the processed information to said central site; receiving means located at said central site for receiving said processed
user terminal information and for receiving, processing and storing GPS data; and
processing means located at said central site for generating aiding data, and including means
for further processing received GPS data to provide accurate positional data indicative of the
location of said GPS satellites in relation to said user terminal, and for transmitting said
information to said user terminal to enable said user terminal to access said GPS system more
rapidly.
Claim 14
Dependent Claim
21 words
The apparatus according to claim 13, wherein said GPS data received
by the user terminal is correlated and synchronization is identified.
Claim 15
Dependent Claim
15 words
The apparatus according to claim 14, wherein an exact relationship
between synchronization data is captured.
Claim 16
Dependent Claim
37 words
The apparatus according to claim 15, wherein said synchronization data is
processed to include C/A code and bit synchronization information together with the time of
measurement, prior to transmission from said user terminal to said central site.
Claim 17
Dependent Claim
34 words
The apparatus according to claim 13, wherein said information
transmitted to said user terminal from said central site includes the GPS ID of all GPS
satellites that should be visible by said user terminal.
Claim 18
Dependent Claim
25 words
The apparatus according to claim 13, wherein said information
transmitted to said user terminal includes the GPS epoch relative to the central site's network
time.
Claim 19
Dependent Claim
15 words
The apparatus according to claim 13, wherein said cellular system is a
mobile satellite system.
Claim 20
Dependent Claim
32 words
The apparatus according to claim 13, further including storage means
located at said central site for storing catalog information of the latest GPS ephemeris to be
used in processing said GPS data.
References Cited (Backward Citations)
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