Efficient SLM based impulsive noise reduction in powerline OFDM communication systems

A very efficient method to mitigate impulsive noise (IN) over powerline channels is to precede the OFDM demodulator with a blanker to zero the incoming signal when it exceeds a certain threshold. Blanking the signal samples unaffected by IN exceeding this threshold, i.e. blanking errors, can cause severe performance degradation. For best performance, the optimal blanking threshold must be determined and this requires some prior and accurate knowledge about the characteristics of IN; this method is referred to as the unmodified method. In this paper, we propose an algorithm to enhance the capability of such methods by processing the OFDM signal at the transmitter to make the IN more easily identifiable at the receiver. This is done by simply deploying a peak to average power ratio (PAPR) reduction technique such as the selective mapping (SLM) scheme. A closed-form analytical expression for the probability of blanking error is derived and the problem of blanking threshold optimization is addressed under various IN environments. The results reveal that the proposed technique is able to minimize the probability of blanking error dramatically and can provide significant SNR improvement relative to the unmodified scheme. It will also be shown that when SLM is implemented with a large number of phase sequences, not only a considerable SNR enhancement is achieved but also, unlike the unmodified method, it becomes feasible to completely alleviate the need for any previous knowledge about the IN characteristics for optimal blanking.