Performance Analysis of FFT Based OFDM System and DWT Based OFDM System to Reduce Inter-carrier Interference

Abstract

OFDM (Orthogonal Frequency Division Multiplexing) is a multicarrier technique to increase the data rate of wireless channel. In OFDM, bandwidth is divided into many narrow bands whose carriers are orthogonal to one another. Implementation of OFDM deals with application of Fast Fourier Transform (FFT) to modulation and demodulation processes to generate carriers orthogonal to each other. In conventional system, IFFT (Inverse Fast Fourier Transform) is used at transmitter side and FFT is used in receiver side. There is need to append cyclic prefix at transmitter side to reduce the Inter symbol Interference (ISI) and to increase spectral efficiency. Recently there is proposition of Wavelet transform to generate sub channels with added advantage of flexibility of transform and high suppression in side lobes. This paper provides overview of performance of DWT (Discrete Wavelet Transform) based OFDM system as compared to FFT based OFDM system to reduce Inter carrier Interference caused due to sampling frequency offset in AWGN (Additive White Gaussian Noise) channel.