Optimal harvesting and sensing durations for multi-antenna cognitive radio networks using intelligent reflecting surfaces

In this paper, we suggest to optimize harvesting and sensing duration for cognitive radio networks (CRN) using intelligent reflecting surfaces (IRS). The secondary source $$S_S$$ harvests energy using the signal of node A. Then, $$S_S$$ performs spectrum sensing to detect primary source $$P_S$$ activity. When $$P_S$$ activity is not detected, $$S_S$$ transmits a packet to secondary destination $$S_D$$ . IRS reflects the signals from the secondary source so that all reflections are in phase at secondary destination. We show that the use of N=8,16,32,64,128, 256,512 reflectors offers 19, 25, 31, 37, 43, 49, 56 dB gain when compared to the absence of IRS [20]. We also propose to add a second IRS between node A and $$S_S$$ to increase the harvested energy since $$S_S$$ harvests energy using the reflected signals on the first IRS. The use of two IRS with $$N_1=8$$ reflectors in the first IRS and $$N_2=8$$ reflectors in the second IRS offers 12 dB and 30 dB gain when compared to a single IRS $$N=8$$ and the absence of IRS [20]. The use of two IRS with $$N_1=16$$ and $$N_2=8$$ offers 21 dB and 39 dB gain when compared to a single IRS $$N=8$$ and the absence of IRS [20].