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In this paper, we propose a Two-Way Cognitive Relay Network (TWCRN) where the secondary users operate on an underlay mode to access the licensed bands. In the proposed protocols, two secondary sources transmit their data to a relay in the first time slot, and then the relay would forward the received information to both sources in the remaining time. Moreover, the relay is self-powered by harvesting energy from ambient Radio Frequency (RF) signals, using the Time Switching (TS) and the Power Switching (PS) method. This paper concentrates on evaluating the performance of the secondary networks under the impact of hardware impairments and co-channel interference from the primary networks. In particular, based on the secondary transmitters’ constraint power, we derive the closed-form expressions of the outage probability and the throughput over Rayleigh fading channels in two cases: TS and PS. We also investigate the energy efficiency issue and the locally optimal position of the relay to maximize the system throughput, which provides much information to install the relay location. Finally, our derivations are verified by Monte Carlo simulation.

In this study, the influence of cutting parameters and machining time on the tool wear and surface roughness was investigated in high-speed milling process of Al6061 using face carbide inserts. Taguchi experimental matrix (L9) was chosen to design and conduct the experimental research with three input parameters (feed rate, cutting speed, and axial depth of cut). Tool wear (VB) and surface roughness (Ra) after different machining strokes (after 10, 30, and 50 machining strokes) were selected as the output parameters. In almost cases of high-speed face milling process, the most significant factor that influenced on the tool wear was cutting speed (84.94 % after 10 machining strokes, 52.13 % after 30 machining strokes, and 68.58 % after 50 machining strokes), and the most significant factors that influenced on the surface roughness were depth of cut and feed rate (70.54 % after 10 machining strokes, 43.28 % after 30 machining strokes, and 30.97 % after 50 machining strokes for depth of cut. And 22.01 % after 10 machining strokes, 44.39 % after 30 machining strokes, and 66.58 % after 50 machining strokes for feed rate). Linear regression was the most suitable regression of VB and Ra with the determination coefficients (R2) from 88.00 % to 91.99 % for VB, and from 90.24 % to 96.84 % for Ra. These regression models were successfully verified by comparison between predicted and measured results of VB and Ra. Besides, the relationship of VB, Ra, and different machining strokes was also investigated and evaluated. Tool wear, surface roughness models, and their relationship that were found in this study can be used to improve the surface quality and reduce the tool wear in the high-speed face milling of aluminum alloy Al6061

We consider spectrum-sharing scenario where coexist two communication networks including primary network and secondary network using the same spectrum. While the primary network includes directional multi-transceivers, the secondary network consists of relaying-based transceiver forwarding signals by energy harvesting assisted relay node. In cognitive radio, signals transmitted from secondary network are sufficiently small so that all of primary network receivers have signal to noise ratio (SNR) greater than a given threshold. In contrast, the transmitted signals from primary network cause increasing noise which is difficult to demodulate at secondary network nodes and hence it leads to the peak power constraint. In this paper, we focus on the influence of random location of transceivers at primary network using decode-and-forward protocol. Specifically, we derive closed-form outage probability expression of the secondary network under random location of transceivers and peak power constraint of primary network. This investigation shows the relationship between the fraction of energy harvesting time $$\alpha $$ of time switching-based relaying protocol on outage probability of secondary network and throughput. In addition, we analyse the influence of the number of primary network transceivers as well as primary network’s SNR threshold on secondary network. Furthermore, the trade-off between increasing energy harvesting and rate was investigated under the effect of energy conversion efficiency. The accuracy of the expressions is validated via Monte-Carlo simulations. Numerical results highlight the trade-offs associated with the various energy harvesting time allocations as a function of outage performance.

Non-orthogonal multiple access (NOMA) along with cooperative communications have been recognized as promising candidates for the fifth generation (5G) wireless networks and have attracted many researchers. Every networked device however has its own limited power supply. To this extent, this paper investigates a power-splitting relaying (PSR) protocol for wireless energy harvesting and information processing in the NOMA systems to prolong the lifetime of the energy-constrained relay nodes in wireless networks so as to avail the ambient radio-frequency (RF) signal as well as to simultaneously harvest the energy and process the information. Decode-and-forward relaying is employed at the relay node where the energy from the received RF signal is harvested and exploited to forward the information to the destination. Specifically, the outage probability and ergodic rate of the PSR protocol are derived to realize the impacts of energy harvesting time, energy harvesting efficiency, power splitting ratio, source data rate, and the distance between nodes. It is also shown that an increased energy harvesting efficiency results in an enhanced performance and an outperformance in terms of the energy efficiency is achieved with the employment of the NOMA when compared to the conventional orthogonal multiple access. Numerical results are provided to verify the findings.