Impulsive noise suppression in DFT-SOFDM system

Abstract

The basic idea underlying OFDM systems is the division of the available frequency spectrum into several sub-carriers. To obtain a high spectral efficiency, the frequency responses of the sub-carriers are overlapping but orthogonal [4][5].Consider block diagram of the DFT-SOFDM transmission system shown in Fig.l. noise. The longer symbol duration provides an advantage, since the impulsive noise energy is spread among simultaneously transmitted sub-carriers. However, it was recently recognized that this advantage turns into disadvantage, if impulse noise energy exceed a certain threshold [3].A simple but effective method of reducing the adverse effect of impulsive noise is to precede conventional OFDM demodulator with nonlinearity methods. In this paper, blanking nonlinearity and clipping nonlinearity are applied in underwater acoustic DFT-SOFDM system. This method is widely used in practice since it is very simple to implement and provides an improvement in impulsive noise channels. The study was based on the experimental results in real underwater acoustic channel.The rest of this paper is organized as follows. In Section II , the signal processing operations in DFT-SOFDM system was described. Impulsive noise cancellation was described in Section III.The experiment results in shallow water near the seaside of Xiamen were given in Section N. Figure 1_ the block diagram of the DFT-spread OFDM system AddCP