Client-aiding with cellphones in a 150-KM radius area

• US 7,200,414 B2
• Filed: 08/07/2002
• Issued: 04/03/2007
• Est. Priority Date: 08/07/2002
• Status: Active Grant

• Current Assignee: Furuno Electric Co, Ltd, Seiko Epson Corporation (Seiko Group)
• Original Assignee: eRide, Inc. (Furuno Electric Co, Ltd), Seiko Epson Corporation (Seiko Group)
• Inventors: McBurney, Paul W., Morrison, William J.
• Primary Examiner(s): Eng; George
• Assistant Examiner(s): Cho; Un C.
• Application Number:
  US10/215,138
• Publication Number:
  US 20040192334A1
• Time in Patent Office: 1,700 Days
• Field of Search: 455/67.11, 455/67.16, 455/456.1, 455/456.5, 455/456.6, 455/457, 455/502, 455/265, 342/356, 342/357.05, 342/357.06, 342/357.1, 342/357.12
• US Class Current: 455/502
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 5/0072 Transmission between mobile stations, e.g. anti-collision systems

Abstract

A cellphone system comprises a GPS reference station located with a telephone cell site. Such GPS reference station tracks the GPS satellites visible to its local area and estimates the Doppler for each such GPS satellite. The system also includes mobile GPS receivers and cellphones that move around and through the operational area of the cell site. It is assumed that the satellite Dopplers seen by the GPS reference station will have insubstantial differences with the true Dopplers observed by other GPS receivers operating within the cell site'"'"'s service area. The Doppler estimates are thus routinely communicated over a wireless telephone channel to the mobile GPS receivers and cellphones that register locally. Such mobile GPS receivers then can confidently adopt the surrogate Doppler estimates as a center starting point for their initialization frequency searches. The time required for such mobile GPS receivers and cellphones to initialize and provide a first fix is thereby substantially reduced.

Claims

1. A mobile electronics device, comprising:

a cellular telephone for downloading initialization-aiding information related to a z-count and a Doppler estimate of an orbiting overhead GPS satellite being received by a reference GPS navigation receiver and a cellular telephone transceiver within 150-km; and

a mobile GPS navigation receiver connected to receive said aiding information and able to use it to avoid having to resolve integer ambiguities and to center its initial carrier frequency search windows during its initialization;

wherein, starting with a correct z-count and said Doppler estimate reduces the time for the mobile GPS navigation receiver to initialize itself.

2. A cellular telephone system, comprising:

a cell site that includes a reference GPS navigation receiver and a cellular transceiver that are able to provide z-count Doppler, ephemeris, and GPS time information for each visible satellite;

wherein, said reference GPS navigation receiver has a fixed location and packages information useful for initializing; and

wherein said cellular transceiver transmits said information useful for visiting mobile users within 150-km of said fixed location, half the codephase propagation distance.

3. The system of claim 2, further comprising:

a cellular telephone for downloading from the cell site initialization-aiding information related to a z-count of an orbiting overhead GPS satellite; and

a mobile GPS navigation receiver connected to receive said aiding information and able to combine it with a fractional range to construct a complete starting pseudorange during its initialization;

wherein, said aiding information reduces the time for the mobile GPS navigation receiver to initialize itself.

4. A method for assisting a GPS navigation receiver to initialize itself, the method comprising the steps of:

acquiring and tracking a visible constellation of overhead GPS satellites at a cell site with a reference GPS receiver;

obtaining z-count, Doppler, ephemeris, and GPS time information useful to another GPS receiver that is initializing;

checking for any mobile cellphones that have registered at said cell site, or a nearby cell site, and that are within 150-km so that said z-count information will be useful to initialize another GPS receiver associated with said mobile cellphone which is mobile and visiting; and

transmitting a Doppler-aiding information over a wireless-telephone communication channel to said any mobile cellphones.

5. The method of claim 4, further comprising the steps of:

bringing a cellphone up from a cold start such that it does not have a lock on any GPS satellite and therefore is uncertain about z-counts;

registering said cellphone in a local area of said cell site, and that are within 150-km so that said z-count information will be useful to initialize another GPS receiver associated with said mobile cellphone which is mobile and visiting;

checking to see if aiding information is available;

downloading if available said aiding information; and

using said aiding information to reduce uncertainty and improve time to a first position solution.

6. The method of claim 4, further comprising the preliminary step of:

assuming that any satellite z-counts seen by said reference GPS navigation receiver will be the same as those that will be observed by any other GPS receivers operating within a 150-km radius service area of said cell site.

7. A cellphone system, comprising:

a GPS reference station located with a telephone cell site, and that tracks any GPS satellites visible to its local area and estimates a Doppler for each such GPS satellite;

at least one mobile GPS receiver and cellphone combination that can move around and through an operational 150-km radius area of said telephone cell site;

a transceiver for communicating at least one z-count over a wireless telephone channel to said mobile GPS receiver and cellphone combinations that register locally;

wherein said mobile GPS receiver adopts a surrogate z-count for its initialization, and any time required for initialization is substantially reduced.

8. A method of initializing a satellite navigation receiver, comprising:

(a) using a first satellite navigation receiver to,

(1) acquire and track orbiting navigation satellites (202);

(2) determine a Doppler shift estimate (204) for each orbiting navigation satellite being tracked in the previous step (202);

(3) detect information requests from client users within a particular service area limited to a 150-km radius (206) such that the z-counts will be the same and not ambiguous; and

(4) supply a Doppler shift estimate for each orbiting navigation satellite being tracked to said client users (208);

(b) using a second satellite navigation receiver roaming within said 150-km radius to,

(1) begin its own initialization (210);

(2) contact said first satellite navigation receiver with a client user request for information (212);

(3) download Doppler shift estimates from said first satellite navigation receiver (214) and assume that the z-counts are the same to eliminate integer ambiguities;

(4) start at least one carrier-frequency search (216) for said orbiting navigation satellites with a corresponding one of said Doppler shift estimates downloaded in the previous step;

(5) acquire and track said orbiting navigation satellites (218);

(6) use the assumed z-counts to compute pseudoranges; and

(7) output position solutions (220).

9. The method of claim 8, further comprising:

using a wireless telephone channel (222) in said contact to communicate said client user request for information; and

responding with said wireless telephone channel (224) to download said Doppler shift estimates.