Abstract
The average bit error rate (BER) performance of M-ary orthogonal noncoherent frequency-shift-keying (FSK) over frequency-selective Nakagami-m fading channels with an exponentially decaying power delay profile is studied. Exact analytical results when suboptimum square-law combining type of reception is used are first presented. Metrics and performance of maximum likelihood (ML) type of receivers are then discussed. The performance results of optimum ML receivers are obtained via extensive Monte-Carlo computer simulations, and are compared with the the analytical average BER results obtained for the suboptimum square-law combining receivers. Numerical and simulation results confirm that the optimum ML receivers outperform square law receivers for strictly positive values of the power decay factor and do not suffer from the well-known "noncoherent combining loss" which affects the performance of square law receivers at low signal-to-noise ratio values. In addition, these results show that suboptimum receivers perform actually quite well with respect to their optimum counterpart in general but the performance difference between them becomes more significant as the Nakagami (1960) fading parameter and/or the number of diversity paths increases.