Energy-efficient cooperative spectrum sensing with relay switching based on decision variables for cognitive radio

Two schemes of energy-efficient cooperative spectrum sensing with relay switching over Rayleigh fading channels are proposed and analyzed for cognitive radio (CR). With relay switching, to save the power and transmission resource of the relays, not all available relays are activated all the time. In the first scheme, when relaying is activated, a switch-and-test (SWT) policy based on the energy received from the relaying path is used. To enhance the detection performance of SWT, in the second scheme, a switch-and-selection-test (SST) policy is considered. In both schemes, energy detection is employed for spectrum sensing. Both SWT and SST schemes integrate the relay switching and spectrum sensing into one step, which further saves the power and time of relay processing. The corresponding probabilities of false alarm and correct detection are derived. Numerical results are presented for performance illustration and comparisons.