Security analysis for Rayleigh fading channel by artificial noise

In classical three-node communication scenario, two legitimate users (Alice and Bob) communicate over a fading channel and a third one (Eve) observes their transmission as an eavesdropper. Alice can transmit the signal with artificial noise to ensure security communication. The artificial noise degrades the performance of Eve, and it can be cancelled by Bob because of pre-knowing. In this paper, a new concept - equivalent security SNR is denned for clarity and simplicity. And we make analysis for the existence probability of positive security capacity and the security outage probability. Then we derive the optimal factor of power allocation for artificial noise and give the theoretical results when the eavesdropper´s channel quality is very high. Theory analysis and simulation results show that by using artificial noise, the security capacity is increased greatly and the security of the physical layer communication is promised.