A physical layer secure wireless communication scheme with partial CSI for high speed railway

The high speed railway wireless communication system is quite different from public wireless communication system, because the service is train control message, which are closely related to the safety of train transportation. Thus it has much higher requirements for the safety and reliability. In this paper, secrecy capacity and outage probability at the high speed railway scenario with traditional MIMO and beamforming schemes are analyzed. The analytic results show that MIMO scheme can not meet the safety requirements and the beamforming scheme is also helpless while the eavesdropper is close to eNodeB. In order to guarantee the transmission safety of train control messages, a physical layer secure scheme with artificial noise (AN) is proposed for high speed railway communication system. In this proposed scheme, beamforming and AN transmitting directions are adjusted accordingly with the onboard legitimate receiver's channel state information (CSI) and eavesdropper's partial CSI to degrade the eavesdropper while maximize the system secrecy capacity. Simulation results demonstrate the proposed scheme decreases the outage probability under the secrecy capacity constraint, and can meet the safety communication requirements.