Exact Probability of Error of ST-Coded OFDM Systems with Frequency Offset in Flat Rayleigh Fading Channels

Abstract

In this paper, we analyze the error performance of single-input-single-output (SISO) and space-time coded (ST-coded) orthogonal frequency division multiplexing (OFDM) systems with carrier frequency offset (CFO) in frequency-flat Rayleigh fading channels. Exact analytical expressions are derived for the symbol error probability (SEP) for BPSK and QPSK modulation schemes. The analysis presented has the following key features - it explicitly accounts for (i) the non-Gaussian nature of the intercarrier-interference (ICI) noise when the total number of subcarriers is small, and (ii) the dependency of the post-FFT signal and the ICI noise terms due to subcarrier correlations. Thus, the proposed method provides accurate SEP formulae, overcoming the inaccuracies involved in Gaussian approximation based methods reported in literature. The numerical results demonstrate the sensitivity of the receiver error performance to CFO in SISO-OFDM and ST-coded OFDM systems in flat Rayleigh fading channels. Also, the SEP results presented can be interpreted as the lower-bound of error performance in a general frequency-selective Rayleigh fading channel