Patent ID: 7224982
Filing Date: 2007-05-29
Classification: G01S,H04W

Abstract:
1. A location system for use in a cellular communication network comprising: a first set of base stations transmittiug and receiving signals in a first communication format having a first time base; a second set of base stations transmitting and receiving signals in a second communication format having a second time base, wherein all base stations transmit known signals at predetermined times for use in deriving location data; a transmitting and receiving unit at a known location; a transmitting and receiving unit at an unknown location; means for determining times of arrival of the known signals from at least one base station in each of said first set of base stations and said second set of base stations at the known location; means for determining the times of arrival of signals from at least one base station from each of said first set of base stations and said second set of base stations at the unit at the unknown location; means for converting between said first time base and said second time base by measuring a time of a start of a transmission frame in said first time base, a frame number of said transmission frame in said first time base, a time of a start of transmission frame in said second time base, and a frame number of said transmission frame in said second time base; means for comparing timing differences between signals received at the unknown location and signals received at the known location from each base station from each of said first set of base stations and said second set of base stations; and means for determining the unknown location based upon said comparing.