Design of Non-linearity about Quadratic Amplitude Modulation in an Impulsive Noise Environment

Abstract

From many electronics, an unexpected noise is generated. An impulsive noise or non-Gaussian noise has been announced as appropriate model for abrupt strong interference, now that the noise is observed as impulsive property. Founded on these models, many researchers have tried to find a solution to prevent a performance degradation, because the impulsive noise severely interferes with detecting a transmitted signal. Non-linearities are used so that the overall system guarantees low complexity and little performance degradation. Designs of non-linearity are considerably proceeded about binary phase shift keying (BPSK) system. However, a non-linearity for quadratic amplitude modulation (QAM) system has been researched. Since a constellation of QAM is different to that of BPSK, non-linearity to be designed for BPSK has been not inefficient to reduce performance degradation. Therefore, this paper proposes non-linearity for QAM system in impulsive noise. The proposed non-linearities include non-linearities of hard-limiter and blanker that offer simple calculation of thresholds of non-linearities. Besides, due to the fact that non-linearity of optimal receiver is transformed as a certain signal power, simple calculation of switching threshold to choose non-linearities is proposed. Simulation results show that there is little performance degradation of the proposed scheme when comparing with performance of optimal receiver.