Cooperative Spectrum Sensing for Three Secondary Users with Sequential Relaying for Cognitive Radio

Cooperative spectrum sensing for Cognitive Radio (CR) networks involves more opportunistic Secondary Users (SUs) that help each other to detect the presence of the signal transmitted by a licensed Primary User (PU). Among cooperative spectrum sensing methods, the Amplify and Forward (AF) technique assumes that SUs relay the received signals without additional processing. In the present paper, inspired by previous works, we introduce a novel cooperative AF scheme with three SUs, where two SUs (denoted as S
2
and S
3
) perform a sequential relaying for the signal transmitted by the third SU (S
1
) using a Time Division Multiple Access (TDMA) transmission protocol. This sequential relaying requires three consecutive time slots. In the first slot, S
1
transmits a test signal; in the second slot, S
2
relays the signal received during the first slot; in the third slot, S
3
relays the signal received during the second slot. Considering the conventional Energy Detection (ED), the detection probability is estimated analytically and by simulation. Even the novel scheme requires an additional time slot, we demonstrate that the sequential relaying AF scheme outperforms the non-cooperative scheme for almost any topological position of the relaying SUs.