Cooperative Spectrum Sensing with Distributed/Centralized Relay Selection

In this paper, we suggest a new Cooperative Spectrum Sensing (CSS) algorithm using Distributed Relay Selection. Spectrum sensing is performed at Fusion Node (FN) using only the signal from Primary User (PU) when its Signal to Noise Ration (SNR) is larger than threshold $$\gamma _{th}$$ γ th . If SNR of the link between PU and FN is lower than $$\gamma _{th}$$ γ th , a relay is activated using distributed relay selection. All relays compare their SNRs to threshold $$\alpha$$ α and transmit only if the SNR exceeds $$\alpha$$ α . If the SNR of all relays are less than $$\alpha$$ α , there is an outage event, no relay is selected and only the signal from PU will be used for spectrum sensing. If SNRs of more relays than two relays are larger than $$\alpha$$ α , a collision occurs and spectrum sensing uses only the signal from PU. Threshold $$\alpha$$ α is optimized using the Gradient algorithm to yield the largest detection probability. We also compare our results to spectrum sensing with centralized relay selection using opportunistic Amplify and Forward (OAF) or Partial Relay Selection (PRS). In OAF, the end-to-end SNR between PU, relays and FN are sent to the FN to be compared and the relay with largest SNR is activated. In PRS, the SNR at the relays are sent to the FN in order to be compared. Then, the relay with largest SNR of first hop, between PU and relays, is activated. CSS with distributed relay selection is novel and no yet studied.