Quasi Orthogonal Space Time Block Code Over Nakagami-m Frequency Selective Fading Channels with Simple Decoding Complexity

Abstract

In this paper, a Quasi Orthogonal Space Time Coding (QOSTBC) system over Nakagami-m frequency selective fading channels is introduced. The proposed scheme is carried out for the M-QAM modulation schemes assuming imperfect channel state information at the receiver. Inter symbol interference effect introduced due to the assumption of the frequency selective fading channels is eliminated by using the Orthogonal Frequency Division Multiplexing (OFDM) technology. Through the Bit Error Rate (BER) versus Signal to Noise Ratio (SNR) simulation results under different values of both Nakagami-m parameter and channel estimation error, the validity of the proposed technique is demonstrated. The results confirm that the BER in the case of frequency selective fading is overlapped with that of flat fading. This implies that the use of OFDM technology mitigates the effect of Inter-Symbol Interference (ISI) caused by frequency selectivity in the channel. Also, the results show that as the imperfect channel estimation error increases the performance degrades.