Performance Analysis and Power Optimization for Spectrum-Sharing Mixed RF/FSO Relay Networks With Energy Harvesting

Abstract

In this paper, the energy harvesting in mixed multiple-input-single-output radio frequency (RF)/free space optical (FSO) networks is studied. Assuming underlay mode, the secondary user (SU) source with limited battery communicates with its destination via a hybrid SU relay. The SU source harvests energy from both the hybrid relay and the primary network. The hybrid SU relay node is equipped with two antennas; one for energy transmission to the secondary user and the other for data reception. The SU source transmits its data over an RF link to the relay. Then, the relay decodes the SU data before retransmitting it to the SU destination over an optical link. The RF/FSO channels are assumed to follow Nakagami-m/Málaga-M fading models with pointing errors on the FSO link. Closed-form expressions for the exact outage probability, average bit error rate, and ergodic capacity are derived. For high signal-to-noise ratio values, closed-form expressions for the asymptotic outage probability and average bit error rate are derived. Based on the asymptotic results, a power allocation model is proposed to enhance the system outage performance. Some simulation and numerical results are employed to validate the derived expressions.

Secrecy Performance Analysis of Mixed Hyper-Gamma and Gamma-Gamma Cooperative Relaying System

“…Despite having huge benefits, FSO link is remarkably sensitive to pointing errors and atmospheric turbulence. To overcome these problems, the concept of mixed radio frequency (RF)-FSO system was introduced that inspired a lot of researchers around the world to investigate the behaviour of such mixed systems [13]- [33]. In a RF-FSO framework, the critical long-distanced part is generally covered by RF channel whereas the short-distanced line-of-sight (LoS) portion is covered with FSO link.…”

“…An underlay cognitive RF-FSO system with multiple relays adopting PRS strategy was designed by the authors in [32]. In [33], a multiple-input single-output (MISO) RF-FSO underlay cognitive system was shown to reduce the OP based on a proposed power allocation model.…”

Relay Selection in Energy Harvesting Aided Mixed Rf/Fso System With Transmit Antenna Selection Over Atmospheric Turbulence and Pointing Error

“…Since the FSO link is assumed to follow M-distribution, the CDF of the R-to-D FSO link can be expressed as [4]:…”

“…To alleviate these problems, FSO system has been proposed to be used in conjunction with the RF system because of its desirable features such as unlicensed spectrum, high security, and cheap cost of deployment [3]. Therefore, exploiting the complementary advantages of both links leads to a significant improvement in performance of wireless communication networks [4]. In this case, vast amount of research has been conducted on the performance of mixed RF/FSO systems.…”

“…They considered the direct link between the source and destination, and Rayleigh/Gamma-Gamma distributions are assumed for system channels. Moreover, the performance of a spectrum-sharing mixed multiple-input-single output (MISO) RF/FSO system with energy harvesting was studied in [4]. The channel model of the RF/FSO network is assumed to follow Nakagami-m/Malaga-M fading distributions.…”