Pseudolite-augmented GPS for locating wireless telephones

A method for locating a wireless telephone by augmenting the Global Positioning System with a network of pseudolites, comprising the steps of:

• transmitting binary code signals from at least three binary code signal sources, at least one binary code signal being transmitted from a pseudolite on a radio frequency not used by the Global Positioning System, the pseudolite binary code signal transmitted according to a time division multiplexing system;
• interleaving the binary code signals of said binary code signal sources according to said time division multiplexing system, wherein said time division multiplexing system assigns a different binary code signal broadcast time slot for each of said binary code signal sources;
• receiving the binary code signals with a mobile receiver;
• determining the times the binary code signal sources transmitted the binary code signals;
• determining the times the mobile receiver received the binary code signals;
• and
• determining the location of the mobile receiver from each binary code signal time of transmission and time of arrival, and from binary code signal source location information.

A geolocation system, comprising:

• means for transmitting binary code signals from sources having known locations, including at least one ground-based means for transmitting binary code signals on a radio frequency not used by the Global Positioning System, the ground-based means transmitting binary code signals according to a time division multiplexing system;
• means for receiving the binary code signals;
• means for determining the arrival times of binary code signals at each means for receiving binary code signals;
• means for interleaving the binary code signals of the binary code signal sources according to said time division multiplexing system, wherein said time division multiplexing system assigns a different binary code signal broadcast time slot for each of the binary code signal sources;
• and
• means for determining a location of a mobile receiver from the arrival times of the binary code signals and the known locations of the binary code signal sources.