Image transmission over Gilbert-Elliot and ITU fading channels using DVB-T2 channel coding and QPSK-OFDM

Abstract

In this work, a concatenated forward error correction (FEC) scheme together with Orthogonal Frequency Division Multiplexing (OFDM) have been used for effective transmission of data/images over additive and fading channels. With a Bose Chaudhuri Hocquenghem (BCH) code as the outer code and a Low Density Parity Check (LDPC) code as the inner code, the transmission has been simulated over both the Gilbert-Elliot and ITU Rayleigh fading channels. The FEC parameters assumed throughout the simulations were obtained from the DVB-T2 standard and the Base Band (BB) frames were created by making use of shortening and zero-padding concepts. The results which have been presented in terms of BER and psycho-visual performances show the resilience of the FEC schemes and OFDM to channel impairments. The BER performances attained over the Gilbert-Elliot Channel (a channel that introduces burst errors when in the bad state) using LDPC only and BCH-LDPC concatenated coding indicated that the outer BCH coding will start to achieve a much lower BER after an SNR of 5 dB. Over the ITU-A Rayleigh fading channel it was observed that the performance increment due to the outer BCH encoder only become apparent after 6 dB when compared to the rate ¼ LDPC only coded system BER performance. Over the Gilbert-Elliot channel a BCH-LDPC coded QPSK-OFDM system would provide a BER of 3×10−4 at 6 dB while the same BER for the ITU Vehicular-A channel was possible at 6.6 dB.