Mitigation of Performance Degradation by Impulsive Noise in LDPC Coded OFDM System

In the paper, LDPC (Low-Density Parity-Check) coded OFDM system applicable for impulsive noise channel, such as powerline channel (PLC) will be presented. Performance degradation in the proposed system over impulsive noise channel is mitigated using a simple estimator based on the Gaussian approximation with estimated channel information (ECI) and a signal level limiter. At first, it will be shown that the performance of a conventional LDPC coded OFDM system is seriously degraded due to the imperfection of estimating the initial LLRs (Log Likelihood Ratios) of sum-product decoder over impulsive noise channels and hard evaluation of the initial LLRs from the decentralized noise samples by OFDM demodulator. Thereafter, to overcome the problems, the system using the simple estimator and the received signal level limiter is proposed. Simulation results show that the proposed system has much better performance than that of conventional systems. For the verification, Monte Carlo simulation is applied.