Medium Disturbance Sensing Techniques for FSK Modulation

This paper describes measurement techniques for rapidly characterizing frequency selective fading channels. The approach used involves estimating each of the parameters describing the transmitted signal and channel disturbances. This includes signal level, noise level, and multipath spread. While specifically applied to FSK modulation and HF channels, the techniques are applicable to other fading media such as troposcatter. The advantages of the proposed techniques are several: the measurement is performed by operating on the transmitted information bits and special test signals or redundancy are not required. Instrumentation is relatively simple and the techniques are applicable to practical communication media. Calculations are provided to determine the measurement time for stated accuracies and confidence levels. Results are obtained for several multipath distributions and as a function of the multipath-to-noise energy ratio.