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

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