Performance Comparison of FFT, DCT, DWT and DDDWT-OFDM in Rayleigh Channel

Cost effective, easily accessible and high speed wireless communication systems are of great demand. Hence implementation of efficient methods to improve spectral efficiency and Bit Error Rate (BER) performance in multicarrier systems has become an important issue. Conventional Orthogonal Frequency Division Multiplexing (OFDM) is a multicarrier technique to increase data rates of wireless communication channel. Implementation of conventional OFDM system involves Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT) at Transmitter and Receiver. Besides numerous advantages with these systems, Cyclic Prefix has to be appended to minimize Inter Symbol Interference (ISI) and increase Spectral efficiency. Wavelet based system on the other hand avoids cyclic prefix requirement, provides side lobes which are very narrow, improves spectral efficiency and better BER performance. The performance of conventional multicarrier FFT-OFDM can be improved by the application of Wavelet Transforms like Discrete Wavelet Transform (DWT), Double Density Discrete Wavelet Transforms (DDDWT). The performance is compared in terms of BER verses SNR using Discrete Cosine Transform (DCT), DWT and DDDWT. The complex wavelet transforms based OFDM performed better than conventional multicarrier FFT-OFDM.