Asymmetric Satellite-Underwater Visible Light Communication System for Oceanic Monitoring

In this paper, we investigate the performance of the proposed oceanic monitoring system that connects the oceanic life with the terrestrial life. For continuous real-time monitoring and ubiquitous coverage, the communication system is aided with a satellite link. Multiple sensor nodes (SN) are deployed at different water levels that collect sensor data and transmit it to underwater vehicles (UV) using underwater visible light communication (UVLC). The UVLC system provides higher data rates at lower latency as compared to existing radio frequency (RF) and acoustic wave alternative for underwater communication (UWC). The UWC system comprises of horizontal haul (HH) and vertical haul (VH) UVLC links modelled using turbulence induced fading. The vertical haul links are modelled as the concatenation of successive non-mixing turbulent links to take into account the change of turbulence with the change of water level. The UVs and submarines communicate with the floating vessels (FVs) using vertical haul UVLC link. The UVs collect the data from the low power sensor nodes and offloads it to the FVs, which further beams it to the satellite on the RF carriers. The novel expressions of performance metrics such as outage probability and average bit error rate are derived. Further, the performance of the system is analysed for various system and channel parameters to prove the feasibility of the proposed communication system

Experimental Investigation of All-Optical Relay-Assisted 10 Gb/s FSO Link Over the Atmospheric Turbulence Channel

This paper presents novel experimental results for a 10 Gb/s triple-hop relay-based all-optical free space optical (FSO) system by employing the amplify-and-forward relaying scheme. We provide a mathematical framework for the end-end signal-to-noise ratio (SNR) and the bit-error rate (BER) performance and confirm that the derived analytical results reasonably match experimental results especially at relatively high SNR. The evaluated BER performances under different atmospheric turbulence regimes (modeled by the Gamma-Gamma distribution) show that the considered relay-assisted FSO system offers a significant performance improvement for weak-to-strong turbulence regimes, even without knowledge of the channel state information. More precisely, at a target BER of 10-5, the proposed scheme offers ~5 and ~4 dB of SNR gains compared to the direct transmission for turbulence strengths Cn2 of 3.8 × 10-10 m-2/3 and 5.4 × 10-12 m-2/3, respectively

Error rate and ergodic capacity of RF-FSO system with partial relay selection in the presence of pointing errors

This paper presents an analysis of a multiple dual-hop relaying system, which is composed of km-class radio frequency (RF)-free-space optical (FSO) links. Partial relay selection based on outdated channel state information (CSI) is employed in order to select active relay for further transmission. Amplify-and-forward relaying protocol is utilized. The RF links are assumed to be subject to Rayleigh fading, and the FSO links are influenced by both Gamma–Gamma atmospheric turbulence and pointing errors. On the basis of our previously derived expression for cumulative distribution function of the equivalent signal-to-noise ratio of the whole system, we derive novel analytical expressions for the average bit-error rate (BER) and ergodic capacity that are presented in terms of the Meijer’s G-function and extended generalized bivariate Meijer’s G-function, respectively. The numerical results are confirmed by Monte Carlo simulations. Considering the effect of time-correlation between outdated CSI and actual CSI related to the RF channel at the time of transmission, the average BER and the ergodic capacity dependence on various system and channel parameters are observed and discussed. The results illustrate that the temporal correlation between outdated and actual CSI has strong effect on system performance, particularly on BER values, when FSO hop is influenced by favorable conditions

Performance of Integrated IoT Network with Hybrid mmWave/FSO/THz Backhaul Link

Establishing end-to-end connectivity of Internet of Things (IoT) network with the core for collecting sensing data from remote and hard-to-reach terrains is a challenging task. In this article, we analyze the performance of an IoT network integrated with wireless backhaul link for data collection. We propose a solution that involves a self-configuring protocol for aggregate node (AN) selection in an IoT network, which sends the data packet to an unmanned aerial vehicle (UAV) over radio frequency (RF) channels. We adopt a novel hybrid transmission technique for wireless backhaul employing opportunistic selections combining (OSC) and maximal ratio combining (MRC) that simultaneously transmits the data packet on mmWave (mW), free space optical (FSO), and terahertz (THz) technologies to take advantage of their complementary characteristics. We employ the decode-and-forward (DF) protocol to integrate the IoT and backhaul links and provide physical layer performance assessment using outage probability and average bit-error-rate (BER) under diverse channel conditions. We also develop simplified expressions to gain a better understanding of the system's performance at high signal-to-noise ratio (SNR). We provide computer simulations to compare different wireless backhaul technologies under various channel and SNR scenarios and demonstrate the performance of the data collection using the integrated link.Comment: This work has been submitted to IEEE for possible publicatio

Exact Outage Probability Analysis of the Mixed RF/FSO System With Variable-Gain Relays

This paper presents a unified analysis of the mixed radio-frequency (RF)/free-space optics (FSO) relaying system, with multiple variable-gain amplify-and-forward relays. The partial relay selection (PRS) is employed to select the active relay for further re-transmission. Due to fast fading statistics of the first RF hop, it is assumed that the channel state information of the RF link is outdated, which is used for both the relay gain adjustment and the PRS procedure. The RF hops are subject to the Rayleigh fading, while the FSO hop is affected by the atmospheric turbulence and the pointing errors. The intensity fluctuations of the optical signal caused by atmospheric turbulence are modeled by the general Malaga (M) distribution, which takes into account the effect of multiple scattered components. An exact expression for the outage probability is derived. In addition, high-signal-to-noise-ratio approximations are provided, which can be used to efficiently determine the outage probability floor. Numerical results are validated by Monte Carlo simulations, which are used to examine the effects of the system and channel parameters on the RF/FSO system performance.Comment: Published in: IEEE Photonics Journa

On the Performance of Optical Wireless Cooperative Systems over the DGG Fading Channel

There is a growing research interests in hybrid optical and microwave wireless communications, which could be adpted in the next generation wireless networks. In this paper, based on the decode-and-forwardrelaying protocol and statistical behavior of the overall link's signal-to-noise-ratio, we consider five different practical scenarios by dering closed-form expressions for the outage and the bit error probabilities. Using Monte Carlo simulation we verify the predicted results. It is demonstrated that, decreasing the semi-angle of LED or increasing the filed of view of VLC receiver enhance the performance

The improvement of fiber-detection method to enhance the output of amplify-received relaying on FSO communications

The performance of free-space optical (FSO) communications that using an optical amplifier (OA) in the scheme of an amplify-received (AR)-relaying has a major drawback in the detection of input signal quality under the effects of turbulence. As an OA is based on a fiber-detection (FD) method to receive and delivers a signal at the amplification process stage, there is an opportunity to implement an optical filter to improve the quality of the input signal. In this paper, as the continuation of previous work on improvement of direct-detection, the optical filter is applied on the AR-relaying of optical signal detection, implementing an OA in the receiver. The novelty proposed in this work is the improvement of FD method where the OF is designed as the integration of cone reflector, pinhole and multi-mode fiber with an OA. The optical filter produces an optical signal, the input of the OA, which minimizes the effects of turbulence, background noise and the fluctuation of the signal spectral. Thus, OA in AR-relaying produces signal output with high power and rise up below threshold level. Additionally, an OF with a lower pinhole diameter produces the best quality of the signal spectral to be delivered into an EDFA. Through this implementation, the performance of optical relaying network on FSO can be significantly improved

Distributed remote antenna unit with selection-based of (RoF-IoT) paradigm: Performance improvement

Data availability statement: All data are available within manuscript.Copyright © 2022 The Authors. Mixing the wireless medium with fiber optics can form a new communication system called a radio-over-fiber (RoF) network; it is a promising solution that can provide high bandwidth and a reliable connection between numerous sensors in wireless sensor networks (WSN) and the central office (base station) within a particular area. This paper first design and discusses new paradigms of fire detection in the IoT environment using RoF technology. Second, this paper covers the distribution of remote antenna unit (DRAU) architecture within RoF-IoT. Finally, best remote antennas unit selection (BRAUS) of distributed RAUs architecture protocols utilizing new selection metrics is proposed. Two important metrics have been analysed and mathematically modelled, outage probability and bandwidth efficiency, respectively. Both metrics have been analysed as a function of the distance, number of RAUs, fiber optic attenuation, and path loss factor. Based on the simulation and numerical analysis, the outage probability of proposed protocols is reduced by 65% compared to recent work; in addition, the bandwidth efficiency of the proposed protocol is increased by 34% compared to recent work.Brunel University London. Grant Number: J066

Applications of Meijer's factorization theorems in performance analyses of all-optical multi-hop FSO systems

The use of bivariate Fox H-functions (BFHFs) in performance analyses of wireless communication systems has gained considerable attention in past few decades. However, the non-existence of robust built-in routines for evaluating such functions in standard computing systems poses numerous challenges in numerical experiments and simulations. Motivated by the apparent need to circumvent these difficulties in performance analyses of cooperative wireless communications, this work presents an alternative method for obtaining the exact, approximate and asymptotic BFHF-free cumulative distribution function (CDF) of the end-to-end (e2e) signal-to-noise ratio (SNR) of multi-hop amplify-and-forward (AF) relaying wireless communication systems. As an illustration, the e2e performance analysis of an all-optical dual-hop free-space optical (FSO) transmission system over Gamma-Gamma turbulence in the presence of pointing errors is revisited. Specifically, new mathematical formulae for the statistical characteristics of the e2e SNR for systems with AF fixed-gain relaying as well as channel-state-information(CSI)-assisted using heterodyne detection (HD) or intensity modulation with direct detection (IM/DD) are derived in terms of mathematically malleable and uniformly convergent infinite series of weighted Meijer G-functions. The usefulness of the derived CDFs is illustrated through derivation of traditional system performance metrics. The accuracy of the derived analytical formulae is verified via Monte Carlo simulations in MATLAB®. Finally, based on results observed in this paper, useful expansions of common BFHFs in terms of easily computable univariate hypergeometric functions are proposed