High-resolution ranging and location finding using multicarrier signals

A method for determining a receiver timing offset, comprising:

• a) receiving a coherent multicarrier (CM) signal by a receiver, the CM signal comprising a plurality of frequency multiplexed subcarriers characterized by subcarrier phases and subcarrier amplitudes and generated by a CM transmitter using a known subcarrier modulation pattern or a known absence of subcarrier modulation, wherein the receiver comprises circuitry for down-converting and sampling the CM signal and for performing frequency and time synchronization thereof to a local sampling clock;
• b) transforming the CM signal by the receiver into a sampled signal preserving relative subcarrier phase information, wherein the sampled signal has a sample rate R satisfying a Nyquist criterion R>2F, wherein F is a modulation bandwidth of the CM signal;
• and,
• using one or more digital processors to perform digital processing of the sampled signal to determine the receiver timing offset with a time resolution better than a sample period 1/R of the sampled signal, said digital processing comprising:
• c) computing a discrete complex channel impulse response (CCIR) from the sampled signal;
• d) processing the discrete CCIR to obtain a high-resolution channel function defined on a high-resolution time grid spaced by a time step dt that is at least 2 times smaller than the sample time period of the sampled signal;
• e) identifying a peak location in the high-resolution channel function;
• and,
• f) determining the receiver timing offset in the receiver from the peak location.