Unified Error-Rate Analysis of OFDM over Time-Varying Channels

Orthogonal frequency division multiplexing (OFDM) transmission over mobile communication channels is very sensitive to time variations due to Doppler spreading. Time variations within the transmission time of one OFDM block destroy the orthogonality among the subcarriers giving rise to interchannel interference (ICI) which degrades the performance of OFDM over fast fading channels. Error rate analysis of OFDM in the presence of ICI is not trivial due to the cross-correlation between the ICI and the useful signal components. Based on accurate statistical models of the ICI, this paper presents a new accurate non-direct analytical method which simplifies greatly performance evaluation of OFDM in the presence of ICI. This results in new unified expressions for bit and symbol error rates of multilevel quadrature amplitude modulation (MQAM) and M-ary phase shift keying (MPSK) based OFDM communication systems over fast Rayleigh multipath fading channels. These results are further extended to include error rate analysis of OFDM with transmit diversity techniques.