Patent ID: 7515103

Claim:
A method of estimating the distance between a first wireless communication terminal and a second wireless communication terminal including: (i) receiving at the first terminal a received signal comprising a composite multipath derivative of a RF transmission signal transmitted by a second terminal which transmission signal comprises an OFDM signal; and (ii) processing the received signal including performing a demodulation operation to produce a demodulated signal; (iii) resolving the demodulated signal into a plurality of components corresponding to different path length components included in the received signal by producing a composite vector C of phasors from the demodulated signal, constructing a special set {Ck} of vectors, wherein each component of the set {Ck} corresponds to a different particular path length travelled by the received signal, and carrying out a mathematical functional operation to find the absolute value of the inner product |<C,Ck>|of the composite vector C with each of the components of the constructed set {Ck}; (iv) identifying which of the resolved components corresponds to a shortest path length; and (v) for the identified component, computing a time of travel from the second terminal to the first terminal.