Abstract
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].