Narrowband interference suppression based on optimal threshold selection in OFDM systems

To solve the narrowband interference problem in orthogonal frequency division multiplexing (OFDM) systems, a new threshold method is proposed, based on the probability distribution of the received signals. During the channel estimation stage, the noise variance and the desired signal amplitude was estimated by the zero sub-carriers and the non-zero sub-carriers respectively, and the two estimations were put into the fitting function to get the threshold, if the envelope values of certain sub-carriers were higher than the threshold, we confirmed that those sub-carriers were interfered; during the channel equalization stage, the data in sub-carriers which was confirmed to be interfered was set to be zero, so that the high decoding bit error rate (BER) caused by the narrowband interference would be reduced, on account of the channel codes. Theoretical analysis and simulation results show that the method can find and suppress the interference, improve the system performance and can be implemented by hardware easily.