Patent ID: 7574221

Claim:
A method for jointly and iteratively estimating the location of a mobile unit based on ultra-wide band signals received at a plurality of fixed terminals and a range or time-of-arrival between the mobile unit and each of the fixed terminals, comprising: (a) at each fixed terminal, determining a time-of-arrival for the signal received at the fixed terminal using a time-of-arrival estimation algorithm with a variable parameter; (b) based on the times-of-arrival determined at the fixed terminals, providing an estimate of the location of the mobile unit; and (c) determining if the estimate of the location of the mobile unit is accurate within a predetermined threshold using residuals each representing an error relating the estimate of the location of the mobile unit with the known positions of the fixed terminals, such that: when the estimate of the location of the mobile unit is accurate within the predetermined threshold, adopting the estimate of the location of the mobile unit; and when the estimate of the location of the mobile unit is not accurate within the predetermined threshold, repeating determining the time-of-arrival at each fixed terminal according to (a) after modifying the parameter of the times-of-arrival estimation algorithm, thus obtaining updated time-of-arrival estimates and repeating (b) and (c) using the updated time-of-arrival estimates.