Physical Layer Security For A Decode-and-Forward Relay With Different Behavior

Wireless Information-Theoretic Security(WITS) has become a hot issue in the area of wireless communication and physical layer security has been widely concerned recently. Probability of non-zero secrecy capacity is a key parameter to measure wireless communication physical layer security. In this paper, a Relay-Wiretap-Channel model is analyzed which contains a source, a destination, a Decode-and-Forward(DF) relay and an eavesdropper based on cooperative communication model and wiretap channel model. Three types of relay behavior are defined: Cooperative, where the relay fully forward the signal; Selfish, where the relay has a certain probability of non-cooperation; Malicious, where the relay fully dose not cooperate and forwards noise. It`s assumed that in the above three types of behavior, relay could change its power or location.A Matlab model is built, three types of relay behavior and both cases of relay change power and relay change location as well as two different channel conditions are concerned. The impact of relay's power and location on the probability of non-zero secrecy capacity and the difference of two channel conditions are analyzed. And the method to acquire the max probability of non-zero secrecy capacity of the system is proposed.In this paper, an experimental test-bed based upon GNU Radio and Universal Software Radio Peripheral(USRP) is set up and a series experiments in the real-world environment is conducted to prove the theoretical analysis above. Different software programs are written to realize the four nodes of the experiment. The experiment is repeated many times and average value of experiment result is acquired to guarantee the correctness of the experiment data. After the experiment, Matlab and a windowing method are used to process the huge experiment data efficiently. The experiment results perfectly prove the correctness of the theoretical analysis.