Client-aided doppler estimation

• US 20040192334A1
• Filed: 08/07/2002
• Published: 09/30/2004
• 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.
• Granted Patent: US 7,200,414 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• 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 Doppler estimate of an orbiting overhead GPS satellite; and

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

wherein, 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;

wherein, said reference GPS navigation receiver has a fixed location and collects Doppler, ephemeris, and GPS time information useful to another GPS receiver that is initializing and is uncertain about any satellite Dopplers; and

wherein said cellular transceiver transmits said information useful to said another GPS receiver over a wireless telephone communication channel.

3. The system of claim 2, further comprising:

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

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

wherein, said Doppler estimate 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 Doppler, ephemeris, and GPS time information useful to another GPS receiver that is initializing and is uncertain about any satellite Dopplers;

checking for any mobile cellphones that have registered at said cell site, or a nearby cell site; 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 Dopplers;

registering said cellphone in a local area of said cell site;

checking to see if said Doppler-aiding information is available;

downloading if available said Doppler-aiding information; and

using said Doppler-aiding information in a carrier frequency search to reduce uncertainty and improve time to a first position solution.

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

determining if said cellphones are within a 150-km radius of said reference GPS navigation receiver; and

providing said Doppler-aiding information if so to said cellphones.

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

assuming that any satellite Dopplers seen by said reference GPS navigation receiver will have insubstantial differences with a true Doppler observed by any other GPS receivers operating within a service area of said cell site.

8. 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 area of said telephone cell site;

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

wherein said mobile GPS receiver adopts a surrogate Doppler estimate as a center starting point for its initialization frequency searches, and any time required for initialization is substantially reduced.