Efficient coded DCT-OFDM system utilizing Walsh-Hadamard Transform

In this paper, an improved orthogonal frequency division multiplexing (OFDM) system based on discrete cosine transform (DCT) is presented. Discrete Walsh-Hadamard transform (WHT) is utilized in the DCT-OFDM system as a channel-independent precoder to produce the proposed WHT-DCT-OFDM system. The bit-error-rate (BER) performance of the proposed scheme, incorporating a zero-padding guard interval scheme, is compared with a zero-padded DCT-OFDM and DFT-OFDM systems. Simulation results over multipath fading channels show that the BER performance is significantly improved when using the proposed WHT-DCT-OFDM system. Furthermore, a convolutional encoder/Viterbi decoder is utilized in the proposed OFDM system to mitigate the nonlinear distortion of high power amplifier (HPA) and reduce the sensitivity to the carrier frequency offset (CFO).