Performance of QPSK/OFDM on frequency-selective Rayleigh fading channels

In this paper, we derive expressions for the bit error probability of QPSK/OFDM on frequency-selective Rayleigh fading channels. In the OFDM system, ICI (interchannel interference) caused by Doppler spread of the channel degrades the error performance of the system and introduces the error floor even for coherent detection. Analysis results show that the error performance of QPSK/OFDM can be degraded as the normalized maximum Doppler frequency f(D)/B-sub is increased where f(D) is the maximum Doppler frequency and B-sub is the subchannel bandwidth. Computer simulations confirm the theoretical analysis results for BPSK and QPSK signals.