On the optimum number of OFDM subcarriers in fast Rayleigh fading channels

In this paper, we consider the problem of selecting the number of subcarrie rs for an OFDM-MDPSK system when the delay spread of a multipath fading cha nnel varies with the existing mobile environment. In our recent analysis [1 ], we have shown that there are two distinct BER performance behaviors depe ndent on whether the guard interval is larger or smaller than the delay spr ead. In this paper, by associating a probability that relates randomly vary ing channel delay spread to the designed guard period in the average BER co mputation, we present a step by step procedure to select the most suitable number of subcarriers, and other important parameters for the OFDM-MDPSK sy stem.