scholarly journals Time and Spatial Jitter Influence on the Performance of FSO Links with DF Relays and OC Diversity over Turbulence Channels

Photonics ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 318
Author(s):  
Panagiotis J. Gripeos ◽  
Hector E. Nistazakis ◽  
Andreas D. Tsigopoulos ◽  
Vasilis Christofilakis ◽  
Evgenia Roditi
Keyword(s):  
Critical Factor ◽  
Weather Conditions ◽  
Optical Wireless Communications ◽  
Time Jitter ◽  
Diversity Techniques ◽  
High Data ◽  
Mathematical Expressions ◽  
Data Rates ◽  
Turbulence Effect ◽  
The Many

FSO communication is a viral technology among optical wireless communications, gathering the interest of both researchers and manufacturers. This is because of the many advantages associated with FSO communication, including high data rates, reliability, safety, and economy. However, there are several unavoidable drawbacks that shadow the performance of FSO systems. For example, atmospheric turbulence is a well-known problem related to the weather conditions of the channel, which causes the scintillation effect. Also, spatial jitter due to pointing errors is a critical factor of the link’s performance, caused by occasional misalignments between the transmitter and the receiver. Moreover, time jitter is another limiting agent that deteriorates the total throughput, inducing bit stream misdetections, caused by the arrival of out-of-sync pulses. All three effects have been exhaustively studied and many statistical models and interesting solutions have been proposed in the literature to estimate their magnitude and compensate for their impact. In this work, the turbulence effect was treated by Málaga distribution, the spatial jitter effect was regulated by the non-zero boresight model, and the time jitter effect was modeled by the generalized Gaussian distribution. Various modulation schemes were studied, along with DF multi-hop and optimal combining diversity techniques at the receiver’s end. New, accurate mathematical expressions of average BER performance have been obtained, and valuable conclusions were drawn thanks to the presented numerical results.

scholarly journals Underwater Optical Wireless Communications with Chromatic Dispersion and Time Jitter

Computation ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 35 ◽  
Author(s):  
Roumelas ◽  
Nistazakis ◽  
Stassinakis ◽  
Volos ◽  
Tsigopoulos
Keyword(s):  
Wireless Communications ◽  
Communication Systems ◽  
Chromatic Dispersion ◽  
Mathematical Expression ◽  
Optical Wireless ◽  
Optical Wireless Communications ◽  
Time Jitter ◽  
High Data ◽  
Data Rates ◽  
Very High

The obsolete communication systems used in the underwater environment necessitates the development and use of modern telecommunications technologies. One such technology is the optical wireless communications, which can provide very high data rates, almost infinite bandwidth and very high transmission speed for real time fast and secure underwater links. However, the composition and the optical density of seawater hinder the communication between transmitter and receiver, while many significant effects strongly mitigate the underwater optical wireless communication (UOWC) systems’ performance. In this work, the influences of chromatic dispersion and time jitter are investigated. Chromatic dispersion causes the temporal broadening or narrowing of the pulse, while time jitter complicates the detection process at the receiver. Thus, the broadening of the optical pulse due to chromatic dispersion is studied and the influence of the initial chirp is examined. Moreover, the effect of the time jitter is also taken into consideration and for the first time, to the best of our knowledge, a mathematical expression for the probability of fade is extracted, taking into account the influence of both of the above-mentioned effects for a UOWC system. Finally, the appropriate numerical results are presented.

scholarly journals Performance Evaluation of G2T FSO Link Under Various Weather Conditions

2018 ◽  
Vol 7 (4.30) ◽  
pp. 562
Author(s):  
Wafi A. Mabrouk ◽  
M. F.L Abdullah ◽  
M. S.M Gismalla
Keyword(s):  
Performance Evaluation ◽  
Weather Conditions ◽  
Free Space Optical ◽  
Eye Diagram ◽  
High Data ◽  
Received Power ◽  
Data Rates ◽  
Last Mile ◽  
Wide Range ◽  
Effectiveness And Efficiency

FSO technology has attracted a lot of popularity for a variety of applied telecommunication fields. It presents a wide range of advantages that place it in the frontier of high data rates applications, last mile problem and bottleneck issues. It has been preferred for its ease of deployment without fiber cables, no extra tariff fees, cost-effectiveness, and efficiency. FSO excels in performance when compared to contemporary RF technology. On the other hand, there is an increased demand for alternative rail communications solutions. In order to deliver a safer, reliable and fast internet access. In this paper, performance evaluation of a ground-to-train Free Space Optical link communication (G2T FSO) was performed. The system was simulated at 2.5 Gb/s link under several weather conditions. Receiver and geometrical loss were included as well. Furthermore, performance was evaluated in terms of received power, Q factor, BER and eye diagram. Substantial vulnerability to severe fog attenuation was found. Although the system was able to operate with acceptable eye height with min BER of 10-38.  

scholarly journals Performance Analysis of Hard-Switching Based Hybrid FSO/RF System over Turbulence Channels

Computation ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 28 ◽  
Author(s):  
Hira Khalid ◽  
Sajid Sheikh Muhammad ◽  
Hector E. Nistazakis ◽  
George S. Tombras
Keyword(s):  
Communication Networks ◽  
Signal To Noise Ratio ◽  
Ergodic Capacity ◽  
Numerical Comparison ◽  
Wireless Communication Networks ◽  
High Data ◽  
Data Rates ◽  
Turbulence Effect ◽  
Increasing Demand ◽  
Alternative Good

The hybrid system of free space optic (FSO) and radio frequency (RF) has come forth as alternative good solution for increasing demand for high data rates in wireless communication networks. In this paper, wireless networks with hard-switching between FSO and RF link are analyzed, assuming that at a certain time point either one of the two links are active, with FSO link having higher priority. As the signal-to-noise ratio (SNR) of FSO link falls below a certain selected threshold, the RF link is activated. In this work, it is assumed that the FSO link follows Gamma-Gamma fading due to the atmospheric turbulence effect whereas RF link experiences Rayleigh fading. To analyze the proposed hybrid model, analytical expressions are derived for the outage probability, bit error rate and ergodic capacity. A numerical comparison is also done between the performances of the proposed hybrid FSO/RF model and the single FSO model.

Machine learning aided switching scheme for hybrid FSO/RF transmission

2020 ◽  
pp. 1-8
Author(s):  
Kappala Vinod Kiran ◽  
Subhanesh Perinbaraj ◽  
Jayashree Pradhan ◽  
Pradeep Kumar Mallick ◽  
Ashok Kumar Turuk ◽  
...  
Keyword(s):  
Machine Learning ◽  
Data Transfer ◽  
Meteorological Data ◽  
Weather Conditions ◽  
Quality Parameters ◽  
High Data ◽  
Space Optics ◽  
Data Rates ◽  
Rf Communication ◽  
Important Quality

Free Space Optics (FSO) is one of the technologies which supports immense data transfer requirements. Though it offers high data rate, but experiences atmospheric attenuation due to dynamic weather conditions. On the other hand, RF communication has lower data rates but are comparatively insensitive to weather conditions. This paper focuses on a hybrid FSO/RF system with the application of Machine Learning (ML) on the prediction of Link Margin (LM) and a ML based switching mechanism between FSO/RF based on the current weather conditions. LM is considered as an important quality parameters in the design and analysis of the FSO link. Mainly rain and fog meteorological data are considered for the estimation and classification of link.

scholarly journals Transdermal Optical Wireless Links with Multiple Receivers in the Presence of Skin-Induced Attenuation and Pointing Errors

Computation ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 33 ◽  
Author(s):  
Varotsos ◽  
Nistazakis ◽  
Aidinis ◽  
Jaber ◽  
Rahman
Keyword(s):  
High Speed ◽  
Optical Signal ◽  
Optical Wireless ◽  
Implantable Medical Devices ◽  
Optical Wireless Communications ◽  
Pointing Error ◽  
High Data ◽  
Modulation Format ◽  
Pointing Errors ◽  
Mathematical Expressions

The last few years, the scientific field of optical wireless communications (OWC) has witnessed tremendous progress, as reflected in the continuous emergence of new successful high data rate services and variable sophisticated applications. One such development of vital research importance and interest is the employment of high speed, robust, and energy-effective transdermal optical wireless (TOW) links for telemetry with implantable medical devices (IMDs) that also have made considerable progress lately for a variety of medical applications, mainly including neural recording and prostheses. However, the outage performance of such TOW links is significantly degraded due to the strong attenuation that affects the propagating information-bearing optical signal through the skin, along with random misalignments between transmitter and receiver terminals, commonly known as pointing error effect. In order to anticipate this, in this work we introduce a SIMO TOW reception diversity system that employs either OOK or more power-effective L-PPM schemes. Taking into account the joint impact of skin-induced attenuation and non-zero boresight pointing errors, modeled through the suitable Beckmann distribution, novel closed-form mathematical expressions for the average BER of the total TOW system are derived. Thus, the possibility of enhancing the TOW availability by using reception diversity configurations along with the appropriate modulation format is investigated. Finally, the corresponding numerical results are presented using the new derived theoretical outcomes.

scholarly journals Relay-assisted WDM-FSO System: A Better Solution for Communication under Rain and Haze Weather Conditions

2017 ◽  
Vol 4 ◽  
pp. 54-59
Author(s):  
Navneet Dayal ◽  
Preeti Singh ◽  
Pardeep Kaur
Keyword(s):  
Wavelength Division Multiplexing ◽  
Electromagnetic Interference ◽  
Communication Systems ◽  
Weather Conditions ◽  
Wireless Communication Systems ◽  
Wavelength Division ◽  
High Data ◽  
Space Optics ◽  
System A ◽  
Data Rates

Among various conventional wireless communication systems, Free Space Optics (FSO) may be distinguished as well, which provides a good level security, high data rates, an enormous bandwidth and negligible susceptibility to electromagnetic interference. The main problem arises with unfavorable weather conditions, which affect the system’s parameters and require an aversion to other paths. The weather conditions discussed are rain and haze. Elimination of their adverse effects is essential for establishing a better communication system. The routing path is a major issue, as its decreased parameters lead to the diversion of the transmitted signal or to its total loss. In this article, increased system path length and proficiency levels are demonstrated by using relays, which are assisted by Wavelength Division Multiplexing (WDM).

Device-to-Device Communication and NOMA

2018 ◽  
Author(s):  
Indrasen Singh
Keyword(s):  
State Of The Art ◽  
Base Station ◽  
D2d Communication ◽  
Control Mechanisms ◽  
High Data ◽  
Link Distance ◽  
Data Rates ◽  
Device To Device ◽  
Simple Language ◽  
The Many

Device-to-Device (D2D) Communication and Non Orthogonal Multiple Access (NOMA) have become topics of interest for researchers. They are widely recognized as techniques of the next generation cellular wireless networks. D2D technique offers uninterrupted communication among proximate mobile users without transferring data to the base station. This can provide high data rates and power control mechanisms. If D2D direct link distance is more, or the quality of channel is poor then the direct D2D communication gives larger propagation losses. This type of scenarios use relay assisted D2D communication, for improving the transmission capacity and coverage. Where as NOMA ) is one of the many technologies that promise greater capacity gain and spectral efficiency than the present state of the art, and is a candidate technology for 5G cellular networks In this book, fundamentals, state of the art, applications and research challenges of D2D and NOMA have been discussed in simple language

scholarly journals On the Outage Capacity of Transdermal Optical Wireless Links with Stochastic Spatial Jitter and Skin-Induced Attenuation

Photonics ◽  
2021 ◽  
Vol 8 (12) ◽  
pp. 553
Author(s):  
George K. Varotsos ◽  
Konstantinos Aidinis ◽  
Hector E. Nistazakis
Keyword(s):  
New Technology ◽  
Outage Capacity ◽  
Optical Wireless ◽  
Technical Literature ◽  
Implantable Medical Devices ◽  
Optical Wireless Communications ◽  
Pointing Error ◽  
Living Body ◽  
High Data ◽  
Data Rates

The tremendous development of both optical wireless communications (OWC) and implantable medical devices (IMDs) has recently enabled the establishment of transdermal optical wireless (TOW) links that utilize light waves to transfer information inside the living body to the outside world and conversely. Indeed, numerous emerging medical applications such as cortical recording and telemetry with cochlear implants require extremely high data rates along with low power consumption that only this new technology could accommodate. Thus, in this paper, a typical TOW link is investigated in terms of outage capacity which is a critical performance metric that has so far not been evaluated for such wireless systems in the open technical literature. More precisely, an outage capacity analysis is performed considering both skin-induced attenuation and stochastic spatial jitter, i.e., pointing error effects. Analytical expressions and results for the outage capacity are derived for a variety of skin channel conditions along with varying stochastic pointing errors which demonstrate the feasibility of this cross-field cooperation. Lastly, the corresponding simulation outcomes further validate our suggestions.

scholarly journals Efficient OFDM transceiver design for VLC sys-tems in fading channel

2018 ◽  
Vol 7 (1.8) ◽  
pp. 245
Author(s):  
Jayakumari J ◽  
Rakhi K J
Keyword(s):  
Fading Channels ◽  
Bit Error Rate ◽  
Fading Channel ◽  
Visible Light Communication ◽  
Communication Security ◽  
Rf Systems ◽  
High Data ◽  
Data Rates ◽  
Simulation Results ◽  
Rich Spectrum

With the widespread effective usage of LEDs the visible light communication (VLC) system has brought out an increasing interest in the field of wireless communication recently. VLC is envisioned to be an appealing substitute to RF systems because of the advantages of LEDs such as high communication security, rich spectrum, etc. For achieving bearable inter symbol interference (ISI) and high data rates, OFDM can be employed in VLC. In this paper, the performance of VLC system with popular unipolar versions of OFDM viz. Flip-OFDM and ACO-OFDM is analyzed in fading channels. From the simulation results it is seen that the Flip-OFDM-VLC system outperforms the ACO-OFDM-VLC system in terms of bit error rate and is well suited for future 5G applications.

Mobility aware of WDM-based CMO OFDM communication system

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Saad M. Hardan ◽  
Ayad A. Abdulkafi ◽  
Saadi Hamad Thalij ◽  
Sherine S. Jumaah
Keyword(s):  
Wavelength Division Multiplexing ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Light Emitting Diode ◽  
Access Point ◽  
Mobile Users ◽  
Visible Light Communications ◽  
Optical Wireless Communications ◽  
High Data ◽  
The Impact

Abstract The continued increase in several mobile applications forces to replace existing limited spectrum indoor radio frequency wireless connections with high-speed ones. Visible light communications (VLC) technology has gained prominence in the development of high data rate transmission for fifth-generation networks. In optical wireless communications, light-emitting diode (LED) transmitters are used in applications that desire mobility as LED divergence enables larger coverage. Since each VLC access point covers a small area, handovers of mobile users are inevitable. Wavelength division multiplexing (WDM) can be used in VLC systems to tackle the above issue and to meet the increasing demand for indoor connectivity with high bit rates. In this paper, a new system architecture for WDM with coded modulated optical in orthogonal frequency division multiplexing (OFDM) VLC system in conjunction with red, green, blue, and yellow (RGBY) LEDs is proposed to reduce the impact of random receiver orientation of indoor mobile users over VLC downlink channels and improves the system’s bit-error-rate (BER) performance. Simulation results show that the proposed method is not affected by the user’s mobility and hence it performs better than other approaches, in terms of BER for all scenarios and at all positions. This study reveals that using WDM-OFDM-VLC with RGBY LEDs to construct a VLC system is very promising.

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