Cognitive Wireless Power Transfer in the Presence of Reactive Primary Communication User

Abstract

This paper studies a cognitive or secondary multiantenna wireless power transfer (WPT) system over a multicarrier channel, which shares the same spectrum with a primary wireless information transfer (WIT) system that employs adaptive water-filling power allocation. By controlling the transmit energy beamforming over sub-carriers (SCs), the secondary energy transmitter (S-ET) can directly charge the secondary energy receiver (S-ER), even purposely interfere with the primary WIT system, such that the primary information transmitter (P-IT) can reactively adjust its power allocation (based on waterfilling) to facilitate the S-ER's energy harvesting. We investigate how the secondary WPT system can exploit the primary WIT system's reactive power allocation, for improving the wireless energy harvesting performance. In particular, our objective is to maximize the total energy received at the S-ER from both the S-ET and the P-IT, by optimizing the S-ET's energy beamforming over SCs, subject to its maximum transmit power constraint, and the maximum interference power constraint imposed at the primary information receiver (P-IR) to protect the primary WIT. Although the formulated problem is non-convex and difficult to be optimally solved in general, we propose an efficient algorithm to obtain a high-quality solution by employing the Lagrange dual method together with a one-dimensional search. We also present two benchmark energy beamforming designs based on the zeroforcing (ZF) and maximum-ratio-transmission (MRT) principles, respectively, as well as the conventional design without considering the primary WIT system's reaction. Numerical results show that our proposed design leads to significantly improved energy harvesting performance at the S-ER, as compared to these benchmark schemes.

Security Analysis for Underlay Cognitive Network with Energy-Scavenging Capable Relay over Nakagami-m Fading Channels

“…Nevertheless, as a volunteer, the relay is probably unenthusiastic to consume its individual power to forward the message of the unlicensed sender. Propitiously, currently advanced technologies make possible for wireless devices to be selfpowered by scavenging energy in radio frequency (RF) signals [4]. Accordingly, the energy which the relay scavenges is used for relaying to lengthen the radio coverage of the sender, enhancing the communication possibility between the unlicensed sender-recipient pair.…”

MMSE‐based transmission method for wireless powered communication networks

“…Moreover, antenna technology is crucial for RF to increase energy collection efficiency and expand the bandwidth [5,6]. More importantly, wireless power transfer can be easily combined with wireless communication systems [7][8][9][10][11]. Moreover, many research studies have done a lot of research on this balance in multiuser multi-input multi-output (MU-MIMO) systems [9,10].…”