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This paper investigates the impact of using directional antennas and beamforming schemes on the connectivity of cognitive radio ad hoc networks (CRAHNs). Specifically, considering that secondary users use two kinds of directional antennas, i.e., uniform linear array (ULA) and uniform circular array (UCA) antennas, and two different beamforming schemes, i.e., randomized beamforming and center-directed to communicate with each other, we study the connectivity of all combination pairs of directional antennas and beamforming schemes and compare their performances to those of omnidirectional antennas. The results obtained in this paper show that, compared with omnidirectional transmission, beamforming transmission only benefits the connectivity when the density of secondary user is moderate. Moreover, the combination of UCA and randomized beamforming scheme gives the highest path connectivity in all evaluating scenarios. Finally, the number of antenna elements and degree of path loss greatly affect path connectivity in CRAHNs.

In this paper, we investigate the usage of a nonlinear energy harvester at a full-duplex (FD) relay, which can harvest the energy from radio frequency (RF) signals transmitted from the source. We mathematically derive the exact closed-form expressions of outage probability (OP), throughput, and average symbol error rate (ASER) of the nonlinear energy harvester-wireless information and power transfer-FD relaying (N-WIPT-FDR) system over Rayleigh fading channels. Unlike linear energy harvester, nonlinear energy harvester results in more computational complexity. Furthermore, it makes the outage floor happen faster even when self-interference cancellation (SIC) techniques are effectively applied due to the saturation power threshold of the nonlinear energy harvester. The combination of nonlinear energy harvester characteristic and residual self-interference (RSI) has significant impacts on the OP, throughput, and ASER of the considered N-WIPT-FDR system. On the other hand, there is an optimal energy harvesting (EH) time duration, which minimizes the OP. This optimal value depends on the transmission power of the source and the saturation power threshold of the nonlinear energy harvester. Monte-Carlo simulations are conducted to validate the derived mathematical expressions.INDEX TERMS Nonlinear energy harvesting, full-duplex relay, self-interference cancellation, decode-andforward, outage probability, throughput, average symbol error rate.

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