Greedy Algorithm Applied Secrecy Rate Analysis in the Cooperative Communication

Cooperative communication is the future tendency because of low cost. Three fundamental schemes including Amplify-and-Forward (AF) mode, Decode-and-Forward (DF) mode and Compress and Forward (CF) mode could be employed. In the system, relays play the role to transmit the delivered signal to the destination. However, there might be the eavesdroppers pretend the relay to snip the message. Currently, privacy and security are highly requested in the communication. Hence, the secrecy protection becomes important. Traditionally, the complex encryption scheme would be applied but it is not practical to apply to the equipment with low computing resources. According to Shannon Theory, positive secrecy rate could support secure communications. Maximum secrecy rate is the initial step to analyze the possible secure communication in the cooperative system. The exhaustive method to find the extreme secrecy rate in the system could be realized. However, time efficiency is not considerable. In order to reduce the computational complexity, a greedy algorithm might provide an acceptable solution to approach the purpose of analysis. In this work, the DF mode cooperative mode is adopted for analysis with a greedy algorithm. The result shows the effects of eavesdropper are not significant if the destination station select the strong signal from legitimate stations.