GPS and cellular system interworking

• US 6,249,245 B1
• Filed: 05/14/1998
• Issued: 06/19/2001
• Est. Priority Date: 05/14/1998
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Watters, J. Michael, Strawczynski, Leo, Steer, David G.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/078,325
• Time in Patent Office: 1,132 Days
• Field of Search: 455/440, 455/456, 342/357, 342/457, 342/357.03, 342/357.09, 342/357.1
• US Class Current: 342/357.4
• CPC Class Codes: G01S 19/41 Differential correction, e.g. DGPS [differential GPS]
• CPC Class Codes: G01S 2205/008 using a mobile telephone network
• CPC Class Codes: G01S 5/0027 of actual mobile position, i.e. position determined on mobile
• CPC Class Codes: G01S 5/009 Transmission of differential positioning data to mobile

Abstract

Aspects of global positioning system (GPS) technology and cellular technology are combined in order to provide an effective and efficient position location system. In a first aspect of the invention, a cellular network is utilized to collect differential GPS error correction data, which is forwarded to a mobile terminal over the cellular network. The mobile terminal receives this data, along with GPS pseudoranges using a GPS receiver, and calculates its position using this information. According to a second aspect, when the requisite number of GPS satellites are not in view of the mobile terminal, then a GPS pseudosatellite signal, broadcast from a base station of the cellular network, is received by the mobile terminal and processed as a substitute for the missing GPS satellite signal. A third aspect involves calculating position using GPS when the requisite number of GPS satellites are in view of a GPS receiver, but when the requisite number of GPS satellites are not in view of the GPS receiver, then position is calculated using the cellular network infrastructure. When the requisite number of GPS satellites come back into view of the GPS receiver, then position is again calculated using GPS. A fourth aspect involves using cellular signals already being transmitted from base stations to terminals in a cellular network to calculate a round trip delay, from which a distance calculation between the base station and the terminal can be made. This distance calculation substitutes for a missing GPS satellite signal.

Claims

1. A method for determining a geographic position of a mobile terminal comprising the steps of:

receiving global positioning system satellite signals having frequencies in a satellite frequency band at the mobile terminal from a plurality of global positioning system satellites that are in view of the mobile terminal;

performing, by the mobile terminal, distance calculations using said global positioning system satellite signals to obtain distance measurements representing a pseudorange between the mobile terminal and each of the plurality of global positioning system satellites;

transmitting a first signal from the mobile terminal to a cellular network base station, the first signal containing the distance measurements;

receiving the first signal by the cellular network base station and forwarding the first signal to a mobile communications switching office;

receiving, by the mobile communications switching office, the first signal from the cellular network base station and a second signal that contains differential global positioning satellite error correction data, the second signal being provided by a source;

performing, by the mobile communications switching office, corrections on the distance measurements provided in the first signal based on the differential global positioning satellite error correction data, to create corrected pseudorange data;

outputting, from the mobile communications switching office to the cellular network base station, a combined cellular signal that corresponds to the corrected pseudorange data combined with data that corresponds to at least one of voice data and data traffic for modems;

receiving the combined cellular signal by the cellular network base station and outputting the combined cellular signal to the mobile terminal;

receiving the combined cellular signal at the mobile terminal, wherein the combined cellular signal contains the corrected pseudorange data and the at least one of voice data and data traffic for modems;

demodulating the combined cellular signal to extract the corrected pseudorange data therefrom, the demodulating being performed by the mobile terminal;

determining, by the mobile terminal, a present position of the mobile terminal by using the corrected pseudorange data; and

extracting, by the mobile terminal, the at least one of voice data and data traffic for modems from the combined cellular signal, for supplying to a corresponding one of a speaker and a modem coupled to the mobile terminal,

wherein the mobile terminal is not capable of calculating the corrected pseudorange data but is capable of calculating the present position of the mobile terminal from the corrected pseudorange data provided to the mobile terminal.

2. The method of claim 1, wherein said step of receiving said global positioning system satellite signals and said step of receiving said cellular signal is carried out by a single antenna capable of receiving global positioning system satellite signals and cellular signals.