<p>In orthogonal frequency division multiplexing (OFDM) based power line communications (PLC), nonlinear preprocessors including clipping, blanking and joint clipping/blanking have been employed in the receiver front-end to mitigate the effect of impulsive noise (IN). These nonlinear preprocessors are approximated by Bussgang theorem, which can be considered as biased estimation. This is because there always exists an approximation error called Bussgang noise. In this paper, the statistical analysis without approximation error has been proposed to analyze the nonlinear preprocessing performance, so it can be considered as an unbiased estimation. For that reason, the proposed method is more accurate than the one using Bussgang theorem in approximation modeling for nonlinear preprocessors. Also, we compare the bit error rate (BER) of OFDM receivers with the nonlinear preprocessors by considering all possible cases, even when <i>IN</i> does not occur. From the mathematical expression for the BER as a function of the threshold, we derive the optimal threshold with minimum BER of three nonlinear preprocessors and propose the algorithm to find the optimal threshold. Simulation results clearly show that there always exists optimal threshold for OFDM-based PLC receiver under various impulsive scenarios, and joint clipping/blanking achieves better BER performance than clipping and blanking schemes.</p>