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Performance of Iterative Ldpc-based Space-time Trellis Coded Mimo-ofdm System over Awgn and Fading Channels

This paper presents the bit error rate (BER) performance of the low density parity check (LDPC) based space-time trellis coded 2×2 multiple-input multiple-output orthogonal frequency-division multiplexing (STTC-MIMO-OFDM) system on text message transmission. The system under investigation incorporates 1/2-rated LDPC encoding scheme under various digital modulations (BPSK, QPSK and QAM) over an additative white gaussian noise (AWGN) and other fading (Raleigh and Rician) channels for two transmit and two receive antennas. At the receiving section of the simulated system, Minimum Mean-Square-Error (MMSE) channel equalization technique has been implemented to extract transmitted symbols without enhancing noise power level. The effectiveness of the proposed system is analyzed in terms of BER with signal-to-noise ratio (SNR). It is observable from the Matlab based simulation study that the proposed system outperforms with BPSK as compared to other digital modulation schemes at relatively low SNRs under AWGN, Rayleigh and Rician fading channels. The transmitted text message is found to have retrieved effectively at the receiver under implementation of iterative sum-product LDPC decoding algorithm. It has also been anticipated that the performance of the LDPC-based STTC-MIMO-OFDM system degrades with the increase of noise power.