Design and EXIT Chart Analysis of a Doubly Iterative Receiver for Mitigating Impulsive Interference in OFDM Systems

Abstract

In this paper, a doubly iterative receiver for orthogonal frequency-division multiplexing (OFDM) systems is designed to mitigate impulsive interference based on pulse blanking. Although being a very efficient countermeasure, pulse blanking introduces intercarrier interference in OFDM systems leading to system performance degradation. The doubly iterative receiver is designed to overcome this drawback. The inner loop combines iterative demodulation and decoding to cancel intercarrier interference. To make soft information available to the outer loop, the equivalent noise power is derived to employ soft demodulation. The outer loop improves the performance of pulse blanking by performing a hypothesis test, which is used to decide if peaks in the received signal are due to impulsive interference or the large peak-to-average-power ratio common to OFDM signals. This allows to optimize the blanking threshold through maximizing the signal-to-interference-and-noise ratio. To evaluate performance and complexity of the proposed receiver, extrinsic information transfer (EXIT) chart analysis is carried out, where EXIT functions for pulse blanker, demodulator, and decoder are derived. An EXIT chart-based trellis search approach is introduced to calculate the loop schedule achieving target bit-error-rate performance with minimized complexity. Numerical results show a considerable bit-error-rate performance improvement as well as a remarkable complexity reduction.