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This paper improves energy efficiency and communications reliability for wireless transmission under κ - μ shadowed fading (i.e., integrating all channel impairments including path loss, shadowing, fading) and hardware impairment by employing a nonlinear energy harvester and multi-antenna power transmitter. To this end, this paper provides explicit formulas for outage probability. Numerous results corroborate these formulas and expose that energy-harvesting nonlinearity, hardware impairment, and channel conditions drastically deteriorate system performance. Notwithstanding, energy-harvesting nonlinearity influences system performance more severely than hardware impairment. In addition, desired system performance is accomplished flexibly and possibly by choosing a cluster of specifications. Remarkably, the proposed communications scheme obtains the optimal performance with the appropriate selection of the time-splitting factor. [ABSTRACT FROM AUTHOR]

In overlay networks, the cognitive sender ( CS ) assists the primary transmitter ( PT ) by broadcasting the superposed signal composed of both cognitive and primary information with a higher priority for the primary information to ameliorate spectral efficiency. Such different information priorities also facilitate efficient successive interference cancellation (SIC) at corresponding receivers for better system performance. To further benefit CS beside licensed spectrum accessing permission, we assume transmission of CS solely with energy scavenged from PT . Practically, energy scavenger has a nonlinear characteristic and circuit components almost suffer hardware imperfections. Further, path loss, shadowing, and fading are all present in practical wireless channels, which affect not only the scavenged energy but also the system performance. Consequently, this paper proposes a framework to analyze the performance metrics— outage probability and throughput—of overlay networks under realistic scenarios subject to hardware imperfections, energy scavenging nonlinearity, SIC-based signal detection, and versatile-and-general κ - μ shadowed fading. This framework facilitates the system performance evaluation-and-comparison in essential specifications and serves well as a design instruction. Obtained results reveal that hardware imperfections affect the system performance more direly than energy scavenging nonlinearity does and the primary transmission performs considerably better than the secondary transmission irrespective of channel severities. Furthermore, the system performance can be adjusted and optimized versatilely by a multi-parameter set. [ABSTRACT FROM AUTHOR]