Design and comparison of new DWT – OFDM with conventional based system

Abstract

Orthogonal Frequency Division Multiplexing (OFDM) is normally implemented using a Fourier Transform (FT) to create and detect the different subcarriers. This can be efficiently implemented using an Inverse Fast FT / Fast FT (IFFT/FFT). This transform however has the drawback that it uses a rectangular window, which creates rather high side lobes. Moreover, the pulse shaping function used to modulate each subcarrier extends to infinity in the frequency domain this leads to high interference and lower performance levels. A wavelet transform is an operation that filters a signal using wavelet and scaling basis functions. Therefore, we compared the bit error rate (BER), spectral efficiency, and peak to average power ratio (PAPR) performance with the conventional OFDM system through the design of OFDM system based on wavelet transform. In this paper a new wavelet based OFDM system is proposed which uses discrete wavelet transform (DWT) instead of FT. Simulation shows that the use of DTCWT outperforms the use of wavelet packet transform (WPT) and outperforms the use of FT in conventional OFDM system in term of reduction of PAPR. The complementary cumulative distribution function (CCDF) of the PAPR for the OFDM based on DTCWT show about 2 dB improvements over WPM and conventional OFDM.