Joint Power Allocation Scheme for Distributed Secure Spatial Modulation in High-Speed Railway

Abstract

In this article, a distributed secure spatial modulation (DSSM) is proposed to improve the secrecy performance of transmission system in high-speed railway (HSR) scenario. N-remote antenna units are connected with central processing unit to build a cooperative DSSM system. Considering the influences of correlated shadow fading, spatial-temporal correlated fading and Doppler shift, the expressions of secrecy capacity (SC) and bit error rate (BER) are derived. Based on the design of artificial noise, two power allocation algorithms are jointly proposed as security schemes in HSR scenario. At first, a joint optimal secrecy capacity algorithm (JOSCA) is proposed to maximize SC. Another Lagrange constraint extreme algorithm (LCEA) is proposed to maximize inhibition of eavesdropper's BER performance. The numerical results show that compared to conventional spatial modulation, the proposed DSSM with JOSCA brings higher SC and keeps a high value of cooperative SC as the advance of train. Moreover, the proposed LCEA brings better BER performance of legitimate receiver while greatly limiting that of eavesdropper. In terms of the tradeoff between SC and BER, the DSSM gets better balance at the viaduct of high-speed railway scenario.