An Improved ICI Self-Cancellation Scheme for Multi-Carrier Communication Systems

Abstract

For broadband wireless mobile communication systems the orthogonal frequency division multiplexing (OFDM) is a suitable modulation scheme. The frequency offset between transmitter and receiver local oscillator is main drawback of OFDM systems, which causes intercarrier interference (ICI) in the subcarriers of the OFDM system. This ICI degrades the bit error rate (BER) performance of the system. In this paper an improved self-ICI cancellation scheme is proposed to improve the system performance. The proposed scheme is based on discrete Fourier transform-inverse discrete Fourier transform (DFT-IDFT). The simulation results show that there is satisfactory improvement in the bit error rate (BER) performance of the present scheme. Keywords—OFDM, Intercarrier Interference, Interference Coefficients, DFT based Self-ICI Cancellation. I. INTRODUCTION FDM is an emerging modulation scheme in the current broadband wireless mobile communication system due to the high spectral efficiency and robustness to multi-path interference (1). A well-known disadvantage of the OFDM system is its sensitivity to frequency offset between transmitted and received signals, which may be caused by Doppler shift in the channel (2), or by the difference between the transmitter and receiver local oscillator frequencies. The carrier frequency offset causes loss of orthogonality and then the signals transmitted on each carrier are not independent of each other, thus leading to ICI (3). All the methods, available in the literature, that have been developed to reduce the effect of frequency offset can be divided into two groups. In first group, the frequency offset in OFDM systems is estimated and corrected at the receiver side and in the second group the frequency offset is reduced at the transmitter side. The first group is termed as the frequency offset estimation and correction, not considered in this paper. Here the second group, called frequency-offset reduction, is considered. In the frequency offset reduction approaches (2, 4-6), available in the literature, either a guard interval or redundant modulation is necessary in order to achieve a trade-