Cooperative Spectrum Sensing with Multi Antenna based Decode-and-Forward Relay

Performance of a cooperative spectrum sensing with the help of a multi antenna based cognitive relay (CR) is analyzed in this paper. A cognitive coordinator (CC) equipped with an energy detector makes a final decision regarding primary user (PU) with the help of a cognitive relay. The cognitive relay employs maximal ratio combining (MRC) on the signals received from PU via multiple receiving antenna and forwards the sensing information PU to CC using decode and forward (DF) protocol. The CC also uses MRC to combine the two signals: one received directly from PU and the other relayed by CR. Closed form expressions for probability of detection and probability of false alarm are derived for the proposed multi antenna based decode and forward cooperative spectrum sensing scheme (i.e. DF-CSS) using energy detector at CC where all the channels i.e. sensing channel, channel between PU and CR, and channel between CR and CC are assumed to be Rayleigh faded. Further closed form expression for the total error probability of the proposed scheme is developed. Performance of the relay based cooperation is compared with that of non cooperative scheme. The impact of the number of antenna, SNR of sensing channel, on detection performance is also indicated. The analytical results are validated by simulation.