Maximum-likelihood receivers for synchronous fast frequency-hopped multiple-access M-ary frequency-shift-keying systems over frequency-selective Rician-fading channels

In this study, the performance of a synchronous fast frequency-hopped multiple-access (MA) M-ary frequency-shift-keying system employing maximum-likelihood (ML) method over either frequency-selective Rician- or Rayleigh-fading channels is investigated. The ML receiver structures are derived and analysed. It is assumed that all the signals arrive at a receiver with the same power strength and all the users operating in the system undergo independent frequency-selective fading. The performance of the ML receivers is compared with that of the linear-combining and the product-combining receivers. The bit-error rate results of the two conventional receivers are obtained via simulation. The proposed analysis, validated by simulation results, shows that the proposed ML receivers can suppress the MA interference more effectively than other existing receivers under different fading conditions. Moreover, the proposed ML receivers are shown to be robust against the inaccuracy in estimation of the required side information.