Performance Analysis of Superposition Modulation in Physical Layer Security

Abstract

Superposition modulation(SM) separates the transmitters and the bits to be sent into two parts, respectively, and aims that the low-order symbols modulated by different bit sequences reach the legitimate receiver (Bob) synchronously. Then the receiver receives a high-order superposition symbol superimposed by the low-order symbols. Its diversity makes a great fluctuation of communicating channels, which is a great feature for the physical-layer security. So the potential security of SM is deserved to be discussed. This paper investigates the security performance of SM scheme in a wiretap system, and its symbol error rete (SER) at the eavesdropper (Eve) is much higher compared with the traditional QAM scheme. Furthermore, we discuss the effect of channel estimation errors. It shows that SM scheme is as sensitive to estimation error as traditional QAM scheme for Eve, such that SM is still have a better secrecy performance. The results show agreement with computer simulations.