M-ary/SS system using divided sequence frequency diversity

In this paper, we first present the BER degradation of M-ary/SS systems over a Rayleigh fading channel and its improvement by frequency diversity. Next, to use the diversity bandwidth more effectively, we propose a novel M-ary/SS system using divided sequence frequency diversity, in which the spreading sequence is divided to L branches and these divided sequences are transmitted by each different frequency carrier. In the receiver, the maximum likelihood decision is achieved by using the addition of each partial correlation value. Compared with M-ary/SS using conventional frequency diversity and FH/MFSK system, considerable improvement of the BER can be obtained according to the increment of L in the proposed system. Finally, a noncoherent receiver for the proposed system and its performance are shown.