Performance comparison of DWT OFDM and FFT OFDM in presence of CFO and Doppler effect

Abstract

The 4G wireless system of present day demands very high data rate. One of the very promising techniques to meet out the requirement is Orthogonal Frequency Division Multiplexing (OFDM). The OFDM systems so far deployed _ which we can call it as a conventional OFDM _ incorporates Fast Fourier Transform (FFT) blocks in their receivers and Inverse FFT (IFFT) blocks in their transmitters. Recent research shows that the usage of Discrete Wavelet Transform (DWT) in place of FFT and Inverse DWT (IDWT) in place of IFFT renders the increased system performance. In this background the DWT OFDM need to be tested against the Carrier frequency offset (CFO) and Doppler-effect which are the major reasons for the performance degradation in the conventional FFT OFDM. This paper discusses about the BER (Bit Error Rate) performance of the DWT OFDM in presence of CFO and Doppler effect individually and the results are compared with that of the conventional OFDM. For this, estimation of CFO is carried over in both DWT OFDM and FFT OFDM using same procedure and their BER performance are simulated using Matlab. Similar kind of treatment is given to the Doppler-effect also. In both the cases for the given number of symbols, for the given number of blocks, for the given channel condition the DWT OFDM fairly outperforms the FFT OFDM.