Better Performance of Wireless Systems Using WPT Instead of FFT in Standard RA6 Fading Channels

Abstract

In modern digital communication, orthogonal frequency division multiplexing (OFDM) is considered as an effective scheme of Multicarrier Modulation (MCM) technique. The OFDM modulation divides the total frequency band into several narrow band sub-channels, so that the system gets more immune to extremely hostile multipath channels. The conventional OFDM uses Fast Fourier Transform (FFT) to provide orthogonality between sub-channels, but Wavelet Packet Transform (WPT) is also proposed by different authors as an alternative orthogonalization method in recent years. In this paper, after comparing structures and features of FFT-OFDM and WPT-OFDM, we present their BER performance simulated by MATLAB over 6 tap Rural Area (RA6) channel which is defined by the European Telecommunications Standards Institute (ETSI) for Long Term Evolution transmission systems in 3GPP standard. In order to achieve deeper insight into WPT-OFDM performance, Haar, Daubechies5, Symlet5 and Coiflet4 are used as wavelet families in the simulations. At the receiver side, we use frequency domain equalizer (FEQ) for FFT-OFDM and overlap FEQ equalizer for WPT-OFDM to mitigate the fading effects of multipath channel on the received signals. Simulation results show that the performance of OFDM will be improved by using WPT, and since it does not need to use (Cyclic Prefix) CP in WPT-OFDM scheme, this method is more efficient from power and bandwidth points of view with respect to the commonly used FFT-OFDM.