Dual Hop Research Articles

Outage Probability Analysis For Dual-Hop Asymmetric Fading WBAN

Wireless Body Area Networks (WBANs) involve wireless communication among resource constrained sensors located on the human body, which are used to capture physiological signals. A significant challenge faced by WBANs is their reliability. It is crucial to analyze the outage of the system to ensure improved reliability in the system design. This study focuses on analyzing the outage performance of dual hop WBANs under different fading scenarios, wherein the channel coefficients follow different distributions. Outage performance is evaluated using the CDF of the SNR of different fading scenarios. Furthermore, the outage performance of these fading distributions are compared to each other and a target outage probability of 10% was pre-set to evaluate the performance of the composite channels from worst to best. Results show that the minimum acceptable threshold SNRs at average SNR = 15 dB for Gamma-Weibull, Gamma-Log-Normal, Gamma-Rayleigh, Gamma–Gamma, Gamma-Rician and Gamma-Nakagami-m are - 4 dB, 2 dB, 4 dB, 6 dB, 8 dB and 10 dB respectively. The analytical outcomes for all the results for different cases are validated through Monte Carlo simulations. There is a lack of comprehensive frameworks in the literature that address all scenarios according to the authors’ knowledge.

Secrecy and performance analysis of dual hop FSO-RF system using differential chaos shift keying

Secrecy and performance analysis of dual hop FSO-RF system using differential chaos shift keying

UAV aided NOMA relaying with energy harvesting architecture: Performance analysis

In this work, we consider a dual hop Non Orthogonal Miltiple Access (NOMA) based communication network between Source S and two destination users UA , UB which is aided by an Unmanned Aerial Vehicle (UAV) relay R. The energy constrained UAV relay harvests energy from signal transmitted by the source through Power Splitting (PS) and further transmits the signal using Amplify and Forward (AF) protocol to the destination users through NOMA. For the proposed network, we derive analytical expressions for outage probability and ergodic capacity. The impact of parameters like PS ratio and UAV altitude is studied on the overall system performance. Further, the performance of the proposed system is also compared with Orthogonal Multiple Access (OMA) scheme. The results obtained show that the energy harvesting capacity of UAV is significantly affected under Linear and Non Linear EH models. The numerical analysis done is verified through Monte Carlo Simulations.

A Novel Hybrid FSO-mm Wave System for Enhanced Mobile Network Capacity and Reliability

The ever-growing demand for high-bandwidth communication in mobile networks necessitates innovative solutions that provide exceptional capacity and reliability. This paper introduces a novel dual hop hybrid system model that leverages the complementary strengths of free space optics (FSO) and millimeter-wave (mm W) communication, while incorporating a direct mm W link for added robustness. This paper analyzes the comprehensive performance of the proposed hybrid system using a single threshold selection combining. We consider a scenario where the channel state for the FSO link adheres to a Log-Normal distribution under conditions of weak turbulence. For the millimeter wave link, we assume it follows a Nakagami-m distribution, which encompasses a broad range of commonly encountered radio frequency (RF) fading distributions. The proposed system's performance is analyzed by deriving analytical expressions for average bit error rate (ABER) and outage probability (OP). The theoretical results of the proposed system, which are verified using Monte-Carlo simulations, unveil that under turbulence and adverse weather conditions, the performance of the proposed system over a standalone FSO system is improved significantly due to mm W backup link.

GAN Based Channel Estimation and Interference Cancellation for Mixed RF/FSO Cooperative Relaying Systems

Free space optical (FSO) communication systems have been considered as a valid option to be integrated with the existing hardware of radio frequency (RF) systems in cooperative relaying technique called the dual hop RF/FSO asymmetric relay. However, the advantages of cooperative relaying is strongly hampered due to the presence of interference in practical systems. Moreover, the modelling of FSO systems need proper attention due to complex nature of the atmospheric turbulence, pointing errors and beam wander which involves tedious mathematical computations. The present research work focuses on the capability of deep learning models for developing a framework for enhancing the performance of the mixed RF/FSO relaying systems using interference cancellation. Specifically, generative adversarial networks (GANs) have been trained to represent the channel conditions of the co-channel interferer (CCI) and FSO links. The GAN model consists of two competing deep learning models — the generator and the discriminator. Two separate deep learning GAN models namely: CCI-GAN and FSO-GAN have been trained for estimating the channel state information (CSI) for the interferer and FSO links, respectively. The CCI-GAN model has been trained offline and tested with mean square error (MSE) of −53.01 dB and root mean square error (RMSE) of −11.003 dB. On the other hand, the FSO-GAN model has been trained with error metrics of MSE of -80.14 dB and RMSE of −11.12 dB. The trained models have been utilized to summarize the performance of the decode-and-forward (DF) mixed RF/FSO relaying network by analysing the outage probability, bit error rate (BER) and the ergodic capacity of the system. The obtained results demonstrate that the FSO-GAN generates the samples from the probability density function (PDF) representing the FSO link. More importantly, the interference cancellation mechanism adopted using the CCI-GAN enhances the system performance.

On the performance of all-optical RORIS dual hop UAV based FSO systems

In this work, we investigate the performance of an all-optical dual hop free-space optical (FSO) communication system using an unmanned aerial vehicle (UAV) as a relay and utilizing a reconfigurable optical intelligent reflecting surface (ROIRS) to improve the coverage. We statistically characterize the combined effects of the three impairments: atmospheric turbulence (AT), angle of arrival (AoA) fluctuation of UAV, and the geometric and misalignment loss (GML) caused by the fluctuations of the transmitter, ROIRS, and the position and orientation of the UAV. Incorporating the aforementioned effects and the non-orthogonality of the received beam at the UAV and the receiver, closed-form expressions of the overall outage probability and the average bit error rate for the considered system are derived. Furthermore, the analytically derived expressions are verified by Monte-Carlo simulations.

Performance analysis of a dual-hop parallel relayed mixed FSO-UWOC system

Abstract In this paper, we propose a dual-hop parallel relayed mixed free space optical-underwater optical communication (FSO-UWOC) system model to setup a high-speed communication link connecting a distant sender located at the lighthouse tower and the receiver inside the deep ocean to transmit and receive the data for the applications such as deep sea exploration, marine life study etc. The proposed model is the setup of multiple parallel cooperative dual hop communication link for the betterment of the overall system performance under the worst case scenarios. The receiver examines the end-to-end signal to noise ratio and a relay is selected which has the maximum SNR. The selected relay then decodes the incoming optical signal through FSO link into its corresponding visible light signal and further transmits it to the underwater exploration devices such as underwater drone via VLC link. The FSO link is modelled by the Gamma-Gamma fading distribution and the VLC link is modelled by Exponential Generalized Gamma distribution. The end-to-end SNR of the system is utilized to derived the outage probability of the FSO-UWOC system and the impact of the individual link parameters is studied and presented for the proposed system model.

Outage and error performance analysis of dual hop hybrid RF-VLC system with wireless energy harvesting

The presented paper, investigates a dual hop hybrid radio frequency-visible light communication (RF-VLC) system with wireless energy harvesting at the relay. The information signal is transmitted via RF channel from the source (S) (located at some distant location) towards the destination (D). We assumed that there is no direct connectivity between S and D, thus a decode and forward relay (R) is used as an intermediate node between S and D. The source transmits the information signal towards the relay via RF channel. The received information signal at the relay is processed and converted into corresponding optical signal. The optical information signal is then forwarded to the destination. Parallelly, the relay employs the power splitting relaying (PSR) protocol with harvest-then cooperate (HTC) protocol for energy harvesting. The harvested energy is utilized to forward the optical information signal from relay to the user at the destination located inside a building’s room via VLC channel. We assumed that the RF and the VLC channels are modelled by generalized-K fading distribution and lambertian emission model respectively. The statistical characteristics are derived for the instantaneous signal to noise ratio of the individual channels using PSR protocol. Further, these statistics are used to derive the accurate closed form expressions for end to end outage probability and average bit error rate. Moreover, with the help of numerical results, end to end performance of the hybrid RF-VLC system under the influence of various system parameters such as shadowing parameters, power splitting factor, field of view angle of the detector and the distance between the source and the relay is analysed and verified.

Comprehensive performance analysis of hybrid FSO/RF space–air–ground integrated network

Free space optics (FSO) communication due to its large optical carrier bandwidth offers better data rates close to gigabits per second (GBPS) compared to radio frequency (RF) communication and can support seamless ubiquitous high-speed broadband connectivity, which is a significant requirement for sixth-generation (6G) communication. It is also envisioned that the data transmission in 6G communication will be over space–air–ground integrated network (SAGIN) to provide broadband global mobile connectivity. Thus, our main aim in this paper is to investigate the performance of a dual-hop (DH) system model utilizing high-altitude platform station (HAPS) as a relay station with FSO communication for SAGIN scenario, which is expected to be featured in 6G communication. Despite various advantages, HAPS-based FSO satellite communication (SATCOM) is undermined by several factors such as atmospheric turbulence, pointing errors, and atmospheric attenuation. To improve the system performance in terms of capacity and reliability, hybrid FSO/RF communication with RF link as a backup is utilized between ground station (GS) and HAPS. Further, comprehensive end-to-end system performance is investigated by deriving unified closed-form expressions for outage probability and average symbol error rate (SER). We also obtain approximate upper bound expressions for ergodic capacity and outage capacity. The asymptotic expressions are also derived to obtain the diversity order. Here, FSO and RF links are modelled using generalized Malaga distribution with non-zero boresight pointing errors and shadowed κ−μ distribution, respectively. Further, the closed-form expressions for optimum switching threshold signal-to-noise ratio (SNR) are derived and the obtained optimal SNR values are verified using a numerical optimization technique. Finally, the results show that the proposed DH SAGIN-based hybrid FSO/RF SATCOM system is more reliable as well as achieves higher capacity compared to the FSO-based SATCOM systems.

Throughput analysis of dual hop hybrid RF-VLC system with wireless energy harvesting

Abstract In this paper, we study a dual hop hybrid radio frequency-visible light communication (RF-VLC) system with wireless energy harvesting technique. In the proposed model the RF channel and the VLC channel are modelled by generalized-K distribution and lambertian emission model, respectively. A decode and forward relay is used as an intermediate node where power splitting relaying (PSR) protocol is employed to harvest energy from the received RF information signal. The source transmits the information signal towards the relay via RF channel. The relay then decodes the received signal and convert it into corresponding light signal. Simultaneously the energy harvesting circuit at relay harvests the energy from the received RF signal. The relay utilizes the harvested energy to aid the transmission of the light signal towards the user situated inside the building’s room at the destination. Further, the statistics of the instantaneous SNR of the hybrid RF-VLC system at the destination are derived by employing the PSR protocol to obtain an accurate closed form analytical expression for the system’s end-to-end ergodic capacity and achievable throughput in terms of Meijer’s G function. Further, with the help of numerical simulations, we analysed the end-to-end ergodic throughput performance of the hybrid system under the influence of varying channel parameters such as signal to noise ratio, power splitting factor, shadowing parameters, distance between source & relay and source transmitted power.

Secure Transmission for Energy Efficient Parallel Mixed FSO/RF System in Presence of Independent Eavesdroppers

In this paper, the physical layer security (PLS) challenges for a decode and forward (DF) based dual hop mixed free space optical (FSO) / radio frequency (RF) communication system in the presence of multiple eavesdroppers has been investigated. In order to improve the PLS of the energy efficient co-operative communication system, diversity combining techniques have been introduced at the destination node. In addition to this, collusion and non collusion eavesdropper scenarios are considered to make the system more practical. The FSO and RF links are assumed to experience independent Málaga ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {M}$</tex-math></inline-formula> ) and Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> fading distributions, respectively. Additionally, the FSO link model considers the impact of boresigt and non-zero boresight pointing errors and type of optical demodulation scheme. To investigate the security performance, the lower bound for the secrecy outage probability (SOP) and effective secrecy throughput (EST) have been obtained in terms of Meijer’s G function. Thereafter, asymptotic expressions have been derived for the considered system and the numerical results have been verified by the Monte-Carlo simulation method. Finally, we have analyzed the secrecy energy efficiency (SEE) based on secrecy rate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_s$</tex-math></inline-formula> ) of the considered system to provide practical insights into the effect of major parameters on the energy efficient secure transmission design.

Performance Analysis of Wireless Power Transfer Enabled Dual Hop Relay System Under Generalised Fading Scenarios

Dual-hop relay communication systems have received extensive research attention due to their property of improving system reliability, spectral and power efficiency. RF wireless power transfer has also become a popular green technology for remote supply of energy to communication devices. In this paper a RF wireless power transfer enabled dual hop relay system is analysed over generalised fading scenarios. A closed form expression is derived for the outage probability of the decode and forward as well as amplify and forward systems valid for all fading scenarios. Based on this analysis, the optimum design parameter settings for the system are also presented which serve as reference point for measuring the outage performance of other variant of the generalised system. The numerical results obtained from derived expressions are compared with Monte-Carlo simulations and are found to be in excellent agreement with each other.

Thiol S-Conjugate Profiles: A Comparative Investigation on Dual Hop and Grape Must with Focus on Sulfanylalkyl Aldehydes and Acetates Adducts

Cysteinylated and glutathionylated precursors of sulfanylalkyl alcohols have been extensively studied in hop and grape matrices, in contrast to those of sulfanylalkyl aldehydes and sulfanylalkyl acetates. Here, cysteinylated and glutathionylated adducts of 3-sulfanylpentanal (Cys-3SPal and G-3SPal), 3-sulfanylhexanal (Cys-3SHal and G-3SHal), 3-sulfanylpentyl acetate (only Cys-3SPA), and 3-sulfanylhexyl acetate (Cys-3SHA and G-3SHA) were first synthesized. Next, the occurrence of these compounds was studied by RP-HPLC-ESI(+)-MRM and apotryptophanase-GC-PFPD in a few dual hops and Belgian grape must samples. None of the Cys-adducts of 3-sulfanylalkyl aldehydes were detected in hop or grape extracts, while G-3SPal was identified for the first time in a natural matrix. Concentrations ranging from 3 to 15 mg/kg were found in several hop varieties, including Citra, Mandarina Bavaria, Mosaic, Nelson Sauvin, Polaris, and Saaz, whereas G-3SHal was detected (below the quantitation limit) only in the four latters. As for esters, Cys-3SPA was found in hop (4 mg/kg in Mosaic), while G-3SHA was detected only in grape extracts (Belgian Chardonnay and Johanniter). Besides the ubiquitous G-3SHol, G-3SPol was identified here for the first time in grape must (up to 7 mg/kg in Johanniter).

LCR and AFD of the Products of Nakagami-m and Nakagami-m Squared Random Variables: Application to Wireless Communications Through Relays

The paper considers level crossing rate (LCR) and average fade duration (AFD) of the product of independent and identically distributed (i.i.d) Nakagami-m (NM) and double NM squared (also known as gamma-gamma) random variables (RVs). The derived statistics are then directly applied to the radio-frequency (RF) - free space optical (FSO), dual-hop (DH), amplify-and-forward (AF) relaying system over non turbulent-induced-fading channels (nTIFCs) and turbulent-induced-fading channels (TIFCs). The obtained results for LCR and AFD of DH-AF, RF-FSO system over TIFCs and nTIFCs are numerically evaluated and graphically presented for various system model parameters.

Performance analysis of RF-FSO communication systems over the Málaga distribution channel with pointing error

Free Space Optical (FSO) communication systems are used for high speed, secure and cheaper optical connectivity between users. It can transport the data from a suitable relay which is multiplexing many RF users to the receiver. These kind of networks are known as dual hop and asymmetric RF-FSO links. In this work, such an RF-FSO cooperative system is studied which is based on the Decode-Forward (DF) relaying method. For the analysis, the generalized channel models are considered such that the existing results can be expressed under more generic performance expressions. The outage probability is initially derived for this system and subsequently the average bit error rate (ABER) is derived using it. The cooperative diversity performance is also investigated by deriving the asymptotic expressions for these metrics at high received signal-to-noise ratio (SNR).

Unified Performance Analysis of MIMO Mixed RF/FSO Relaying System

This paper investigates the asymmetric dual–hop multiple input multiple output (MIMO) mixed radio frequency (RF)/free space optical (FSO) decode–and–forward (DF) relaying system. This kind of system can utilize two different fading characteristic channels to reduce the possibility of the system falling into deep fading. In addition, each link of the system adopts MIMO technology to mitigate the disadvantages of fading. In this paper, the closed form expressions of the outage probability, bit error rate (BER) and average ergodic capacity are derived. The approximate expression of the system outage probability considering the pointing error is also derived. Additionally, asymptotic performance for diversity order and diversity–multiplexing tradeoff (DMT) of the system is analyzed and discussed, which provides direct theoretical basis for practical engineering design.

Spatially Correlated Dual Hop RIS Aided Next Generation Wireless Systems: An Outage Perspective

Design and analysis of Reconfigurable Intelligent Surfaces (RIS) assisted new wireless communication systems have attracted much attention among the 6G technology researchers. Recently, studies were made to compare the use of RIS and Decode and Forward (DF) relaying when a weak direct path exists between the transmitter and receiver. Amalgamating the merits of both RIS and DF relay technologies, an RIS assisted DF relay-based cooperative wireless system with energy harvesting is proposed in this paper. A Lambertian model of reflectance is employed in the analysis of the reflecting nature of RIS. Further, the impact of spatial correlation which arises due to the tightly-packed planar RIS array geometry is also considered for performance analysis. By varying inter-element distances and transmit power, the performance of the proposed system is analyzed in terms of outage probability and energy harvesting capability. Numerical expressions are derived for the outage probability of the proposed system and verified using Monte-Carlo simulations. Based on the high performance, the concept of joint use of RIS and DF Relay is extended to the Index Modulation (IM) based wireless system.

Dual hop relaying using CDMA and reconfigurable intelligent surfaces (RIS)

In this paper, we suggest the use of reconfigurable intelligent surfaces (RIS) in dual hop relaying. There are two hops, the first one uses code division multiple access (CDMA) and the second one uses RIS as transmitter or reflector. We show that the incorporation of RIS allows to increase the throughput of conventional CDMA systems. The throughput of dual hop relaying using a combination of CDMA and RIS is larger than that of dual hop relaying based entirely on CDMA.

Impact of RF I/Q Imbalance on Interference-Limited Mixed RF/FSO TWR Systems With Non-Zero Boresight Error

In this letter, we investigate a generic model assessing the effect of in-phase/quadrature-phase imbalance (IQI) on an asymmetric dual hop radio frequency/free space optical (RF/FSO) two-way relay (TWR) system in the presence of multiple co-channel interferers (CCIs) at the relay. The fading on the RF and FSO links have been modeled using K-distribution and double generalized Gamma (D-GG) turbulence model, respectively. The impact of non-zero boresight pointing error and type of optical demodulation schemes have been considered on the FSO link. To this end, a closed-form probability density function (PDF) has been derived for the FSO link undergoing D-GG irradiance with non-zero boresight pointing error. Furthermore, the exact and high signal-to-noise (SNR) asymptotic expression for outage probability have been presented. To gain insights into the throughput of the system, approximate and asymptotic expressions for the achievable sum rate (ASR) have been derived. The results show dependency of reliability and throughput offered on IQI at the RF front-end and strength of interference for the considered TWR system.

SPEECH‐MAC: Special purpose energy‐efficient contention‐based hybrid MAC protocol for WSN and Zigbee network

SummaryEnergy‐efficient Zigbee‐based wireless sensor network (WSN) occupies a major role in emergency‐based applications. The foremost drawback of such applications is maintaining the battery power because frequent changing is not possible in those conditions. In the earlier days, several researches created new model MAC protocols in terms of increase the lifetime of the WSN. But still, there is a research gap particularly in emergency applications. In order to improve the lifetime of such applications, we introduced a novel hybrid MAC protocol, namely, special purpose energy‐efficient contention‐based hybrid MAC (SPEECH‐MAC) protocol. This protocol includes dual hop concept considerably to save the energy. Both the single hop network and the dual hop networks are developed, and the results are analyzed. Prioritization mechanism for SPEECH‐MAC protocol is introduced to analyze the emergency conditions in detail. In summary, according to the simulation, the calculated parameters are total residual energy, end‐to‐end delay, packet drop, packet delivery ratio, and network throughput.