Wireless Power Transfer in Distributed Antenna Systems

Abstract

This paper studies the performance of wireless power transfer in distributed antenna systems (DAS). In particular, the distributed remote radio heads (RRHs), which are conventionally distributed in the network to enhance the performance, are also used to increase the energy harvesting (EH) at the energy-constrained users. Based on this idea, the network area is divided into two zones, namely: 1) EH zone and 2) interference zone. The users in the EH zones are guaranteed to harvest sufficient energy from the closed RRH, while the users in the interference zones harvest energy from the surrounding RRHs. A harvest-then-transmit protocol is adopted, where in the power transfer phase the multiple antennas RRHs broadcast energy signals to the users. In the information transmission phase, the users utilize the harvested energy to transmit their signals to the RRHs. In addition, zero-forcing is applied at the RRHs receivers, to mitigate the interference. The system spectral efficiency is evaluated in two different scenarios based on the channel state information (CSI) namely: 1) CSI is unknown at the RRHs 2) CSI is perfectly known at the RRHs. In contrast to conventional EH-muliple-input multiple-output (MIMO) systems, performance analysis of EH DAS-MIMO is a challenging problem, because the channels are characterized by non-identical pathloss and EH effects which make the classical analytical methods non-tractable. In light of this, new analytical expressions of the ergodic spectral efficiency are derived and then Monte Carlo simulations are provided to verify the accuracy of our analysis. The effects of main system parameters on the EH-DAS performance are investigated. The results show that there is an optimal value of the EH time for each users locations that maximizes the system performance. In addition, size of the EH-zone area depends on the required harvested power at the users which is dependent essentially on the target spectral efficiency.Index Terms-DAS, wireless power transfer, zero forcing, spectral efficiency, CSI.

Secrecy Outage Probability of Energy-Harvesting Cooperative NOMA Transmissions With Relay Selection

“…The analytical results are illustrated by carrying out Monte-Carlo simulations, which were executed over 10 5 independent trials. Unless stated otherwise, the noise power at all nodes are set as σ 2 = 0 dBw, the path-loss exponent m = 2.7, η = 0.8 [35] For illustration purposes, we consider a 2D system topology where the source, the users and the eavesdropper are located at (x ds , y ds ) = (0, 0), (x du1 , y du1 ) = (0, 2), (x du2 , y du2 ) = (1.5, 0), (x dM , y dM ) = (1, 0), and (x de , y de ) = (0, 1), respectively, and the relays are located at (x dRe1 , y dRe1 ) = (1, 0.5), (x dRe2 , y dRe2 ) = (1.5, 0.5), (x dRe3 , y dRe3 ) = (1, 1.5) and (x dRe4 , y dRe4 ) = (1.5, 1.5). Due to the symmetry between the strongest user and the eavesdropper paths, this topology can explain the benefit of the relay selection schemes.…”

“…Proof: The proof is provided in Appendix D. Alternatively, to find simpler expressions for the probabilities in (35), these probabilities can be upper-bounded using the fact that [21, (40)…”

“…problem can be formulated as: min 0<βr n <1 P sop . One method to solve this problem and find the optimal value of β rn is using line search techniques such as the golden section method [35].…”

Energy Efficiency in RF Energy Harvesting-Powered Distributed Antenna Systems for the Internet of Things

“…In [ 11 ], the information transmission efficiency of simultaneous wireless information and power transfer (SWIPT)-enabled [ 12 , 13 , 14 , 15 ] DAS was maximized. In [ 16 ], the system spectral efficiency of DAS with wireless power transmission (WPT) was evaluated. In [ 17 ], the authors maximized the network-centric EE and user-centric EE in DAS with WPT.…”

“…This paper also studies the EE in DAS with RF EH. Some differences of our work compared with existing works are outlined as follows: Most existing works aimed to maximize the WIT or spectrum efficiency (SE), see, e.g., [ 11 , 16 , 24 , 25 ]. With the development of wireless networks, EE becomes more and more important.…”