Performance degradation due to the synchronization error in OFDM

Abstract

Synchronization is an important task in orthogonal frequency division multiplexing (OFDM). Typical synchronization error includes carrier frequency offset (CFO), carrier phase offset, sampling clock offset (SCO) and symbol timing offset have been addressed. They will cause performance (symbol error ratio SER) degradation. In this project, we study the effect of synchronization error for BPSK, QPSK, 16QAM, 64QAM and 256QAM systems under an Additive White Gaussian Channel (AWGN). Various parameters like the number of carriers and sampling rate (i.e. the oversampling factor) have been addressed. Theoretical analysis has been performed and verified with computer simulations using MATLAB. Exact theoretical evaluation of SER is performed for symbol timing offset and Monte Carlo method is used for that of CFO and SCO because it appears impossible to evaluate the exact SER when the number of modulation level and number of carrier is above 16. Finally, two phase estimator techniques are proposed to restore the phase rotation and improve the overall SER performance.