Cooperative Spectrum Sensing Using DF Cooperative Diversity Protocol in Cognitive Radio

In cognitive radio networks, secondary users are allowed to access the under-utilized spectrum and opportunistically transmit whenever no primary signals are detected. So these unlicensed users need to monitor spectrum accurately to detect the presence of the licensed users. In this paper, we exploit a cooperative spectrum sensing between two secondary users to improve the detection performance when one of the users is standing on the decodability boundary of the primary user, which is difficult to detect the presence of this licensed user. We develop this cooperative spectrum sensing with decode-and-forward (DF) diversity protocol, and make a comparison with amplify-and-forward (AF) protocol in terms of detection probability. We illustrate that DF protocol has better performance than AF. Then, under DF diversity protocol, we extend to the cooperative spectrum sensing among a group of secondary users, which is illustrated to have a better detection performance.