Analytical Performance Evaluation of Space Time Coded MIMO OFDM Systems Impaired by Fading and Timing Jitter

An analytical approach is presented to determine the impact of time selective fading, timing jitter and additive white Gaussian noise (AWGN) on the bit error rate (BER) performance of an orthogonal frequencydivision multiplexing (OFDM) system with differential quaternary phase-shift keying (DQPSK), differential phaseshift keying (DPSK) and quaternary phase-shift keying (QPSK) modulation. The expression for the conditional BER conditioned on a given timing error and fading, is derived and the average BER is evaluated. The BER performance results are evaluated for different values of fading and jitter. The performance of the OFDM system in Rayleigh and Rician fading channels is also compared. Analytical approach is also developed to evaluate the BER performance of a quasi-orthogonalspace-time block coded OFDM system having multiple transmitting and single receiving antennas. The analysis is extended for a multipleinput multiple-output (MIMO)-OFDM system using the “selection method” for combining multiple receiving antennas, which offers significant improvement in the system performance. The effects of increase in number of OFDM subcarriers and increase in Doppler frequency are also investigated. Index Terms — Convolutional coding, intersymbol interference, MIMO, OFDM, Rayleigh fading, STBC, timing jitter.