We theoretically analyze the performance of free-space optical (FSO) systems using rectangular quadrature-amplitude modulation (QAM) and an avalanche photodiode (APD) receiver over atmospheric turbulence channels. Both log-normal gamma–gamma channel models are used in analysis for cases weak/moderate strong turbulence. The system bit error rate, when Gray code mapping is employed, derived taking into account various link conditions parameters, including APD shot noise, thermal...

This paper addresses the design of hybrid free-space optical/radio frequency (FSO/RF) systems for a high-altitude platform (HAP)-aided relaying satellite communication mobile networks supported by unmanned aerial vehicle (UAV). While prior work primarily focused on fixed-rate design, which frequently switches between FSO and RF lead reduced system performance, we propose rate adaptation that gradually adjusts data in each link when its channel state fluctuates, under target bit error (BER)...

This paper proposes a novel design and analyzes security performance of quantum key distribution (QKD) protocol over free-space optics (FSO). Unlike conventional QKD protocols based on physical characteristics mechanics, the proposed can be implemented standard FSO systems using subcarrier intensity modulation binary phase shift keying direct detection with dual-threshold receiver. Under constraints, criteria for transmitter receiver, in particular, depth selection detection, respectively,...

In this paper, a novel relaying technique is proposed to improve the bit-error rate (BER) performance and distance coverage of high-speed all-optical free-space optical (FSO) communication systems. Particularly, an amplify-and-forward (OAF) using erbium-doped fiber amplifier (EDFA) combined with hard-limiter (OHL) introduced. The use OHL enables EDFA-based OAF FSO systems prevent accumulation amplified background noise, which significantly degrades system performance, when deploying multiple...

Purpose The purpose of this study is to present an exploration green intrinsic motivation’s mediating role in the relationship between socially responsible human resource management (SRHRM) and employee workplace behaviour. Additionally, leadership behaviour’s moderating within investigated. Design/methodology/approach Data were collected via a survey using convenience sampling approach with sample 300 employees Vietnam. A path analysis bootstrapping technique SPSS Process macro used test...

This paper proposes a cost-effective, scalable network architecture, which combines millimeter-wave (MMW) and free space optics (FSO) technologies that can be employed as complementary solution for pre-deployed optical fiber based 5G cellular backhaul networks.

This article investigates the performance of free-space optical (FSO) systems using sub-carrier quadrature amplitude modulation (SC-QAM) signaling for broadband terrestrial applications. While previous studies ignored influence phase noise, we theoretically analyze and derive closed-form expressions system's average bit error rate (ABER) considering combined effect pointing misalignment, turbulence-induced fading, error. The log-normal distribution is used to model atmospheric turbulence in...

This paper studies the design and performance analysis of relay-assisted satellite free-space optics (FSO) quantum key distribution (QKD) systems for secure vehicular networks. High-altitude platforms (HAPs) equipped with optical amplify-and-forward nodes are used as relay stations. Secrecy performances in terms bit error rate ergodic secret-key analytically investigated under effects transceiver misalignment, receiver's velocity variation, receiver noises, atmospheric turbulence conditions....

Previous studies show that, compared to on-off keying (OOK) signaling, pulse-position modulation (PPM) is favorable in FSO/CDMA systems thanks its energy efficiency and simple detection. Nevertheless, when the system bit rate increases transmission distance far, using PPM signaling critically suffer from impact of pulse broadening caused by dispersion, especially level high. In this paper, we therefore propose use multi-wavelength (MWPPM) overcome limitation PPM. To further improve...

A novel method is presented to analyse the effects of atmospheric turbulence and misalignment fading (or pointing error) on performance serial‐relaying M ‐ary pulse‐position modulation (PPM) free‐space optical (FSO) systems. This study more comprehensive than previous ones, since effect beam size variation due by using partially coherent Gaussian model taken into account. In addition, a closed‐form expression formulated for bit error rate PPM FSO systems over Gamma–Gamma channel, taking...

This paper proposes a high-altitude platform (HAP)-aided relaying satellite free-space optics (FSO) quantumkey distribution (QKD) system for the secure vehicular networks supporting unmanned vehicles (UAV) and regular vehicles. The subcarrier intensity modulation (SIM) binary phase shift keying (BPSK) dual-threshold/direct detection (DT/DD) receiver are employed. HAP is equipped with optical amplifyand-forward (OAF) node. We analytically derive ergodic secret-key rate of proposed under...

In this paper, we comprehensively analyze the impact of four wave mixing (FWM) on performance incoherent multi-wavelength optical code-division multiple-access (MW-OCDMA) systems. We also consider many other interferences and noises, including multiple access interference, beating receiver noise, in analysis. From numerical results, can find power ranges different MW-OCDMA systems, which FWM is dominant consequently results an increase bit-error rate that becomes more severe when frequency...

Multihop free space optical (FSO) system using amplify-and-forward (OAF) relaying technique combined with wavelength division multiplexing (WDM) is proposed for all-optical access networks. The can provide a low cost, flexible, and high-bandwidth network multiple users. To investigate the performance, we consider special case of dual-hop WDM-FSO taking into account effects all noises, interchannel crosstalk, as well path loss geometric spreading beam over atmospheric turbulence channels. In...

Free-space optical communication (FSO) is a line-of-sight (LOS) technology that enables data transmission based on the propagation of light in free space. Compared to radio frequency (RF) systems, FSO ones provide high rates, unregulated bandwidth, security, and low power. Therefore, systems are rapidly gaining interest as an effective means transferring at rates over short distances. However, still faces many challenges, including weather-dependent atmospheric attenuation, turbulence,...

Supported by IEEE 802.15.7 standardization activities, visible local area network (VLAN) has been gaining popularity in recent years. Specified the standard are physical (PHY) and uplink medium access control (MAC) layers of VLAN. However, there is a lack studies on MAC performance analysis improvement under effects PHY transmission errors literature. We thoroughly analyze for various metrics taking into account due to different VLC factors. also consider enabling frame retransmissions as...

This paper focuses on the free-space optics (FSO) links between high-altitude platforms (HAPs) and unmanned aerial vehicles (UAVs) which have not been addressed in literature. In considered system model, a HAP UAV play roles as transmitter receiver, respectively. The is operation when it within beam coverage of HAP. work aims to model HAP-UAV FSO channel taking into account effects both atmospheric turbulence pointing error caused by UAV's hovering. A Gaussian assumed for laser transmitted...

In this paper, we study the performance of unmanned aerial vehicle (UAV)-based free-space optical (FSO) systems over atmospheric turbulence channels considering pointing misalignment and UAV hovering. The Gamma-Gamma distribution is used for modeling turbulence-induced fading Gaussian beam assumed laser between two UAVs at low high altitudes. A closed-form expression symbol error probability derived validated by Monte-Carlo simulations. selected results show impact some key factors such as...

In this paper, a novel model of Gaussian pulse propagation in optical fiber is proposed to comprehensively analyze the impact Group Velocity Dispersion (GVD) on performance two-dimensional wavelength hopping/time spreading code division multiple access (2-D WH/TS OCDMA) systems. addition, many noise and interferences, including interference (MAI), beating (OBI), receiver's are included analysis. Besides, we propose use heterodyne detection receiver so that sensitivity can be improved....

Free-space optical (FSO) communication requires light of sight (LoS) between the transmitter and receiver. For long-distance communication, many research projects have been conducted towards using a network composed high-altitude platforms (HAPs) flying at an elevation 20 km to carry intermediate FSO transceivers that forward data ground stations. The clear environment high elevations prevents terrestrial obstacles from cutting LoS transceivers. An transceiver on HAP can communicate with...

We propose Turbo-coded two-dimensional (2-D) free-space optical (FSO) CDMA systems for broadband access networks. The performance bound the proposed system over atmospheric turbulence channels is obtained considering multiple-access interference (MAI) and receiver noise. results show that offers a better than of previously ones. Also, it has tolerance to increase in number users.