US6313787B1
Expired / Lapsed
US
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Method and apparatus for assisted GPS protocol
Assignee: Google Technology Holdings LLC
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Filing: 1999-11-12
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Granted: 2001-11-06
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Expires: 2019-11-12
Abstract
Abstract A cellular network protocol which minimizes the required data flow between the cellular infrastructure and each mobile handset supporting a GPS based positioning capability is taught. Four specific innovations are introduced which together minimize the number of bits required to be transferred to each handset: a method for reducing or removing the requirement for GPS ephemeris updates to each mobile; a method for compression of the differential correction broadcast message; a method for controlling the rate at which the network updates each handset's ephemeris based on an ephemeris age limit; and, finally, a method which each mobile can use to determine when an ephemeris update is needed, based on an accuracy prediction and a threshold which is unique to each mobile.
Inventors
- 👤 Thomas M. King
- 👤 George J. Geier
- 👤 Yilin Zhao
- 👤 Roger C. Hart
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 14:20
CPC Classifications
G; G01; G01S; G01S19/00; G01S19/01; G01S19/13; G01S19/23; G01S19/235; G01S19/03; G01S19/05; G01S19/07; G01S19/071; G01S19/24; G01S19/25; G01S19/258
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
227 words
A method in a mobile radio communication device for determining a location of the mobile radio handset, the method comprising the steps of: receiving an ephemeris message, wherein said ephemeris message comprises Global Positioning System (GPS) ephemeris data for a plurality of GPS satellites and clock correction data; thereafter receiving a differential correction message comprising differential correction data; determining whether the GPS ephemeris data for one or more of the plurality of GPS satellites requires update; requesting an update message comprising updated GPS ephemeris data; receiving the update message; and determining the location of the mobile radio handset in response to the GPS ephemeris data, the clock correction data, the differential correction data, and the updated GPS ephemeris data, wherein the step of receiving an ephemeris message comprises the step of receiving a point-to-point ephemeris message particularly addressing the mobile radio handset, the step of receiving a differential correction message comprises the step of receiving a point-to-point differential correction message particularly addressing the mobile radio handset, and wherein the step of determining whether the GPS ephemeris data for one or more of the plurality of GPS satellites requires update comprises the steps of: calculating a computed location of the mobile radio handset; and determining a prediction of an accuracy of the computed location in response to the computed location, the GPS ephemeris data and a timing parameter.
Claim 2
Independent Claim
227 words
A method in a mobile radio communication device for determining a location of the mobile radio handset, the method comprising the steps of: receiving an ephemeris message, wherein said ephemeris message comprises Global Positioning System (GPS) ephemeris data for a plurality of GPS satellites and clock correction data; thereafter receiving a differential correction message comprising differential correction data; determining whether the GPS ephemeris data for one or more of the plurality of GPS satellites requires update; requesting an update message comprising updated GPS ephemeris data; receiving the update message; and determining the location of the mobile radio handset in response to the GPS ephemeris data, the clock correction data, the differential correction data, and the updated GPS ephemeris data, wherein the step of receiving an ephemeris message comprises the step of receiving a point-to-point ephemeris message particularly addressing the mobile radio handset, the step of receiving a differential correction message comprises the step of receiving a point-to-point differential correction message particularly addressing the mobile radio handset, and wherein the step of determining whether the GPS ephemeris data for one or more of the plurality of GPS satellites requires update comprises the steps of: calculating a computed location of the mobile radio handset; and determining a prediction of an accuracy of the computed location in response to the computed location, the GPS ephemeris data and a timing parameter.
Claim 3
Dependent Claim
55 words
The method of claim 1 wherein the step of determining a prediction of the accuracy of the computed location comprises the step of determining a prediction of the accuracy of the computed location in response to an age of the GPS ephemeris data and a statistical relationship of the age to accuracy of computed locations.
Claim 4
Dependent Claim
46 words
The method of claim 1 wherein the step of determining a prediction of the accuracy of the computed location comprises the step of determining a prediction of the accuracy of the computed location based on covariance information derived by a Weighted Least Square (WLS) fixing method.
Claim 5
Dependent Claim
47 words
The method of claim 3 wherein the step of determining a prediction of the accuracy of the computed location based on covariance information comprises the step of computing the covariance information by scaling the covariance information with information computed from the residuals of an overdetermined WLS solution.
Claim 6
Dependent Claim
21 words
The method of claim 4 wherein said information computed from the residuals is an a posteriori statistic of the unit variance.
Claim 7
Dependent Claim
45 words
The method of claim 1 wherein the step of determining a prediction of the accuracy of the computed location comprises the step of determining a prediction of the accuracy of the computed location based on covariance information computed for a Least Square (LS) fixing method.
Claim 8
Dependent Claim
47 words
The method of claim 6 wherein the step of determining a prediction of the accuracy of the computed location based on covariance information comprises the step of computing the covariance information by scaling the covariance information with information computed from the residuals of an overdetermined LS solution.
Claim 9
Dependent Claim
21 words
The method of claim 7 wherein said information computed from the residuals is an a posteriori statistic of the unit variance.
Claim 10
Dependent Claim
53 words
The method of claim 1 wherein the step of determining whether the GPS ephemeris data for one or more of the plurality of GPS satellites requires update further comprises the step of determining whether the prediction of the accuracy of the computed location exceeds a predetermined accuracy threshold for said mobile radio handset.
Claim 11
Dependent Claim
79 words
The method of claim 9 wherein the step of determining whether the GPS ephemeris data for one or more of the plurality of CPS satellites requires update further comprises the steps of: determining whether the GPS ephemeris data for one or more of the plurality of GPS satellites is old; and determining additional accuracy predictions of the computed location based on hypothesized updated GPS ephemeris data for the one or more satellites for which the ephemeris data is old.
Claim 12
Dependent Claim
45 words
The method of claim 1 wherein said step of determining whether the GPS ephemeris data for one or more of the plurality of GPS satellites requires update comprises the step of determining an ephemeris age limit previously communicated to said cellular infrastructure has been exceeded.
Claim 13
Dependent Claim
29 words
The method of claim 1 wherein the differential correction data has been derived from satellite positions computed using the GPS ephemeris data previously received by the mobile radio handset.
Claim 14
Dependent Claim
28 words
The method of claim 1 wherein the differential correction data has been derived by adjusting the clock correction values for an ephemeris age of the GPS ephemeris data.
Claim 15
Dependent Claim
37 words
The method of claim 1 wherein the step of receiving a differential correction message comprises the step of receiving a broadcast differential correction message addressing more than one mobile radio handset broadcast at a first transmission rate.
Claim 16
Dependent Claim
32 words
The method of claim 14 wherein the step of receiving a broadcast differential correction message comprises the step of receiving a broadcast differential correction message including correctional data for multiple ephemeris sets.
Claim 17
Dependent Claim
18 words
The method of claim 15 wherein the correctional data is calculated as a set of delta correction values.
Claim 18
Dependent Claim
34 words
The method of claim 16 wherein the set of delta correction values are each computed successively, wherein each of the set of delta correction values represents a correction difference with a prior ephemeris value.
Claim 19
Dependent Claim
31 words
The method of claim 16 wherein the set of delta correction values are received at a second transmission rate, wherein the second transmission rate is less than the first transmission rate.
Claim 20
Dependent Claim
18 words
The method of claim 16 wherein the set of delta correction values are compressed based upon RTCM standard.
Claim 21
Dependent Claim
30 words
The method of claim 16 wherein the set of delta correction values are alternated in successive broadcast differential correction messages to reduce a length of the broadcast differential correction messages.
Claim 22
Dependent Claim
30 words
The method of claim 1 , wherein the step of receiving an ephemeris message comprises the step of receiving a broadcast ephemeris message addressing more than one mobile radio handset.
Claim 23
Dependent Claim
35 words
The method of claim 21 wherein the differential correction data of the differential correction message has been derived from positions of the plurality of GPS satellites using the ephemeris data of the broadcast ephemeris message.
Claim 24
Dependent Claim
32 words
The method of claim 21 wherein the differential correction data of the differential correction message has been derived by adjusting previously received differential correction data in response to the clock correction data.
Claim 25
Dependent Claim
50 words
The method of claim 21 wherein the GPS ephemeris data of the broadcast ephemeris message comprises a position of one of the plurality of GPS satellites and a velocity of the one of the plurality of GPS satellites during an interval equivalent to a length of the broadcast ephemeris message.
Claim 26
Dependent Claim
55 words
The method of claim 21 wherein the GPS ephemeris data of the broadcast ephemeris message comprises two or more sets of a position of one of the plurality of GPS satellites and a velocity of the one of the plurality of GPS satellites during an interval equivalent to a length of the broadcast ephemeris message.
Claim 27
Dependent Claim
57 words
The method of claim 1 , wherein the step of receiving an ephemeris message comprises the step of receiving a broadcast ephemeris message addressing more than one mobile radio handset, and wherein the step of receiving a differential correction message comprises the step of receiving a broadcast differential correction message addressing more than one mobile radio handset.
References Cited (Backward Citations)
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| 3.5 Years (Year 4) | 2004-11-05 | 2005-05-07 | 2005-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-11-05 | 2009-05-07 | 2009-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-11-05 | 2013-05-07 | 2013-11-06 | $7700.00 | Window Closed / Lapsed |