Exploiting RMS time-frequency structure for data compression in emitter location systems

Abstract

An effective way to locate RF transmitters is to measure the time-difference-of-arrival (TDOA) and the frequency-difference-of-arrival (FDOA) between pairs of signals received at geographically separated sites, but this requires that samples of one of the signals be sent over a data link. Often the available data link rate is insufficient to accomplish the transfer in a timely manner unless some form of lossy data compression is employed. A common approach in data compression is to pursue a rate-distortion criterion, where distortion is the mean-square error (MSE) due to compression. This paper shows that this MSE-only approach is inappropriate for TDOA/FDOA estimation and defines a more appropriate, non-MSE distortion measure. This measure is based on the fact that in addition to the inverse dependence on SNR, the TDOA accuracy also depends inversely on the signal's RMS (or Gabor) bandwidth and the FDOA accuracy also depends inversely on the signal's RMS (or Gabor) duration. The paper discusses how the wavelet transform can be used to exploit this measure.