Method for estimating a location of a mobile unit based on at least two fixed transceivers

摘要

Signals comprising time of transmission indications relative to a common time base (302) are transmitted by at least two fixed transceivers (110-116). When the signals are received by a mobile unit (160), a time of reception indication relative to the common time base is calculated for each signal. Pseudo-ranges are calculated based on the time of transmission and time of reception indications, and a WLS solution location estimate is calculated based on the pseudo-ranges. Essentially the same procedure may be performed on signals transmitted by the mobile unit. Given the common time base between the fixed transceivers and the mobile unit, only two or more signals are required to determine the location estimate. Where GPS receivers are used to supply the common time base, location determinations can still be made when a GPS solution is unavailable.