PERFORMANCE EVALUATION OF SPACE-TIME TRELLIS CODES WITH SINGLE-CARRIER FREQUENCY DOMAIN EQUALIZATION (SC-FDE) IN RAYLEIGH FADING CHANNEL

Abstract

Multipath fading and intersymbol interference are inherent characteristics of wireless communication. Multipath fading occurs when transmitted signals arrive at the receiver at marginally different times, while Intersymbol Interference (ISI) occurs when the time spread of the channel is longer than one symbol period. Orthogonal Frequency Division Multiplexing (OFDM) is readily employed in wireless communication to combat the ISI effect, yet it suffers from large peak to average power ratio. Single-carrier Frequency Domain Equalization- a variance of OFDM has found usage in recent times to combat the ISI effect. To address the combined effect of fading and interference, a combined model of the Space-Time Trellis Codes (STTC) and Single-Carrier Frequency Domain Equalization (SC-FDE) was developed. In this research, equalization techniques employed were Minimum Mean Square error and Orthogonal Triangular (QR) decomposition. The performance of using both techniques for wireless transmission was evaluated using Bit Error Rate, Frame Error Rate and the Pairwise Error Probability for 4-PSK modulation scheme. The result obtained showed an improved bit error rate of 10-6 at 28 dB when STTC is combined with SC-FDE. Since the channel condition at any time cannot be predicted, the research demonstrated that by combining diversity and equalization techniques with pseudo-inverse channel offers a good method of reducing the effects of fading channels on signals and reduction in bit error rate.