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Computation
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Optical Wireless Communication Systems
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Optical Wireless Communication Systems

A special issue of Computation (ISSN 2079-3197). This special issue belongs to the section "Computational Engineering".

Deadline for manuscript submissions: closed (30 April 2019) | Viewed by 34511

Special Issue Editors

Prof. Dr. Hector E. Nistazakis

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Guest Editor
Section of Electronic Physics and Systems, Department of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece
Interests: wireless communication systems; free space optical communications (FSO); fiber optics communications; electronic physics; nonlinear optoelectronic circuits
Special Issues, Collections and Topics in MDPI journals
Dr. Goran T. Djordjevic

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Guest Editor
Department of Telecommunications, Faculty of Electronic Engineering, University of Nis, 18000 Niš, Serbia
Interests: wireless communications theory; free-space optical communications; cooperative networks; modulations; error-correction codes; diversity reception
Special Issues, Collections and Topics in MDPI journals
Dr. Wilfried Gappmair

E-Mail Website
Guest Editor
Institute of Communication Networks and Satellite Communications, Graz University of Technology, 8010 Graz, Austria
Interests: satellite communications; optical wireless communications; parameter estimation; channel coding
Special Issues, Collections and Topics in MDPI journals
Dr. Sinan Sinanovic

E-Mail Website
Guest Editor
Department of Engineering, Glasgow Caledonian University, Glasgow, UK
Interests: wireless communications; optical wireless; LED-based indoor positioning; anomaly detection; interference mitigation; spatial modulation; PAPR reduction

Special Issue Information

Dear Colleagues,

By means of an Optical Wireless Communication (OWC) concept, useful and important broadband solutions are possible, such as terrestrial free-space optical (FSO) systems, underwater applications, satellite and space communications, visible light links for indoor scenarios, mobile and multimedia networks etc. In the meantime, this kind of technology has been chosen as a backhaul approach for next generation systems, in particular for 5G services. Thus, OWC is a serious candidate to solve problems left by radio frequency (RF) systems, including the “last mile problem”, with high performance and reliability characteristics because of their low installation and operational costs, the huge data rates, the usage of license-free bandwidths and the very high security level. However, their performance depends strongly on the propagation conditions of the optical path, e.g. fluctuations of temperature, humidity and pressure. Therefore, due to their benefits over RF techniques and the challenging character of the optical channel as such, OWC systems have attracted significant commercial and research interest over recent years.

Topics of interest for this Special Issue include, but are not limited to:

  • Indoor optical wireless solutions
  • Optical wireless channel and network modeling
  • Visible light communications (VLC)
  • Line-of-sight and non-line-of-sight FSO links
  • Atmospheric turbulence modelling
  • Radio-on-FSO (RoFSO) links
  • OFDM communications
  • Satellite and space scenarios
  • Novel modulation and coding schemes
  • High-speed devices for photonics
  • OWC with energy harvesting
  • OWC for the Internet of Things (IoT)
  • OWC for underwater scenarios
  • MIMO for optical wireless concepts
  • Optical-based indoor positioning
  • Optical sensor networks and wearables

Dr. Goran T. Djordjevic
Dr. Hector E. Nistazakis
Prof. Dr. Wilfried Gappmair
Dr. Sinan Sinanovic
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Computation is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (9 papers)

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Research

13 pages, 2524 KiB  
Article
Underwater Optical Wireless Communications with Chromatic Dispersion and Time Jitter
by George D. Roumelas, Hector E. Nistazakis, Argyris N. Stassinakis, Christos K. Volos and Andreas D. Tsigopoulos
Computation 2019, 7(3), 35; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7030035 - 11 Jul 2019
Cited by 6 | Viewed by 3226
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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15 pages, 2403 KiB  
Article
Serial DF Relayed FSO Links over Mixture Gamma Turbulence Channels and Nonzero Boresight Spatial Jitter
by Nikolaos A. Androutsos, Hector E. Nistazakis, Hira Khalid, Sajid S. Muhammad and George S. Tombras
Computation 2019, 7(3), 34; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7030034 - 05 Jul 2019
Cited by 7 | Viewed by 3263
Abstract
Over the past few years, terrestrial free space optical (FSO) communication systems have demonstrated increasing research and commercial interest. However, due the signal’s propagation path, the operation of FSO links depends strongly on atmospheric conditions and related phenomena. One such significant phenomenon is [...] Read more.
Over the past few years, terrestrial free space optical (FSO) communication systems have demonstrated increasing research and commercial interest. However, due the signal’s propagation path, the operation of FSO links depends strongly on atmospheric conditions and related phenomena. One such significant phenomenon is the scintillation caused by atmospheric turbulence effects; in order to address the significant performance degradation that this causes, several statistical models have been proposed. Here, turbulence-induced fading of the received optical signal is investigated through the recently presented mixture Gamma distribution, which accurately describes the irradiance fluctuations at the receiver’s input of the FSO link. Additionally, at the same time, it significantly reduces the mathematical complexity of the expressions used for the description of composite channels with turbulence along with nonzero boresight pointing error-induced fading. In order to counterbalance the performance mitigation due to these effects, serial decode-and-forward relays are employed, and the performance of the system is estimated through derived mathematical expressions. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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18 pages, 1780 KiB  
Article
Transdermal Optical Wireless Links with Multiple Receivers in the Presence of Skin-Induced Attenuation and Pointing Errors
by George K. Varotsos, Hector E. Nistazakis, Konstantinos Aidinis, F. Jaber and K.K. Mujeeb Rahman
Computation 2019, 7(3), 33; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7030033 - 28 Jun 2019
Cited by 12 | Viewed by 3126
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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12 pages, 3257 KiB  
Article
Experimental Implementation and Theoretical Investigation of a Vanadium Dioxide Optical Filter for Bit Error Rate Enhancement of Enhanced Space Shift Keying Visible Light Communication Systems
by Dimitra K. Manousou, Argyris N. Stassinakis, Emmanuel Syskakis, Hector E. Nistazakis, Spiros Gardelis and George S. Tombras
Computation 2019, 7(2), 30; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7020030 - 13 Jun 2019
Cited by 4 | Viewed by 3255
Abstract
Visible Light Communication (VLC) systems use light-emitting diode (LED) technology to provide high-capacity optical links. The advantages they offer, such as the high data rate and the low installation and operational cost, have identified them as a significant solution for modern networks. However, [...] Read more.
Visible Light Communication (VLC) systems use light-emitting diode (LED) technology to provide high-capacity optical links. The advantages they offer, such as the high data rate and the low installation and operational cost, have identified them as a significant solution for modern networks. However, such systems are vulnerable to various exogenous factors, with the background sunlight noise having the greatest impact. In order to reduce the negative influence of the background noise effect, optical filters can be used. In this work, for the first time, a low-cost optical vanadium dioxide (VO2) optical filter has been designed and experimentally implemented based on the requirements of typical and realistic VLC systems in order to significantly increase their performance by reducing the transmittance of background noise. The functionality of the specific filter is investigated by means of its bit error rate (BER) performance estimation, taking into account its experimentally measured characteristics. Numerous results are provided in order to prove the significant performance enhancement of the VLC systems which, as it is shown, reaches almost six orders of magnitude in some cases, using the specific experimental optical filter. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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10 pages, 2187 KiB  
Article
Performance Analysis of Hard-Switching Based Hybrid FSO/RF System over Turbulence Channels
by Hira Khalid, Sajid Sheikh Muhammad, Hector E. Nistazakis and George S. Tombras
Computation 2019, 7(2), 28; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7020028 - 06 Jun 2019
Cited by 21 | Viewed by 4590
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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16 pages, 4499 KiB  
Article
Attack Detection for Healthcare Monitoring Systems Using Mechanical Learning in Virtual Private Networks over Optical Transport Layer Architecture
by Vasiliki Liagkou, Vasileios Kavvadas, Spyridon K. Chronopoulos, Dionysios Tafiadis, Vasilis Christofilakis and Kostas P. Peppas
Computation 2019, 7(2), 24; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7020024 - 05 May 2019
Cited by 17 | Viewed by 4430
Abstract
Data security plays a crucial role in healthcare monitoring systems, since critical patient information is transacted over the Internet, especially through wireless devices, wireless routes such as optical wireless channels, or optical transport networks related to optical fibers. Many hospitals are acquiring their [...] Read more.
Data security plays a crucial role in healthcare monitoring systems, since critical patient information is transacted over the Internet, especially through wireless devices, wireless routes such as optical wireless channels, or optical transport networks related to optical fibers. Many hospitals are acquiring their own metro dark fiber networks for collaborating with other institutes as a way to maximize their capacity to meet patient needs, as sharing scarce and expensive assets, such as scanners, allows them to optimize their efficiency. The primary goal of this article is to develop of an attack detection model suitable for healthcare monitoring systems that uses internet protocol (IP) virtual private networks (VPNs) over optical transport networks. To this end, this article presents the vulnerabilities in healthcare monitoring system networks, which employ VPNs over optical transport layer architecture. Furthermore, a multilayer network architecture for closer integration of the IP and optical layers is proposed, and an application for detecting DoS attacks is introduced. The proposed application is a lightweight implementation that could be applied and installed into various remote healthcare control devices with limited processing and memory resources. Finally, an analytical and focused approach correlated to attack detection is proposed, which can also serve as a tutorial oriented towards even nonprofessionals for practical and learning purposes. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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13 pages, 1270 KiB  
Article
On Parameter Estimation for Bandlimited Optical Intensity Channels
by Wilfried Gappmair
Computation 2019, 7(1), 11; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7010011 - 18 Feb 2019
Cited by 9 | Viewed by 2653
Abstract
Parameter estimation is of paramount importance in every digital receiver. This is not only true for radio, but also for optical links; otherwise, subsequent processing stages, like detector units or error correction schemes, could not be operated reliably. However, for a bandlimited optical [...] Read more.
Parameter estimation is of paramount importance in every digital receiver. This is not only true for radio, but also for optical links; otherwise, subsequent processing stages, like detector units or error correction schemes, could not be operated reliably. However, for a bandlimited optical intensity channel, the problem of parameter estimation is strongly related to non-negative pulse shapes satisfying also the Nyquist criterion to keep the detection process as simple as possible. To the best of the author’s knowledge, it is the first time that both topics—parameter estimation on the one hand and bandlimited intensity modulation on the other—are jointly investigated. Since symbol timing and signal amplitude are the parameters of interest in this case, the corresponding Cramer–Rao lower bounds are derived as the theoretical limit of the jitter variance generated by the related estimator algorithms. In this context, a maximum likelihood solution is developed for the recovery of both timing and amplitude. Since this approach requires a receiver matched filter destroying the Nyquist criterion of the non-negative pulse shape, we compare it to a flat receiver filter preserving the required orthogonality property. It turned out that the jitter performance of the matched filter method is close to the Cramer–Rao lower bound in the medium-to-low SNR range, but due to inter-symbol interference effects an error floor emerges at higher SNR values. The flat filter solution avoids this drawback, although the price to be paid is a larger noise level at the filter output, so that a somewhat increased jitter variance is observed. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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25 pages, 2795 KiB  
Article
Optical Boundaries for LED-Based Indoor Positioning System
by Olaoluwa Rotimi Popoola, Sinan Sinanović, Wasiu O. Popoola and Roberto Ramirez-Iniguez
Computation 2019, 7(1), 7; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7010007 - 14 Jan 2019
Cited by 5 | Viewed by 4333
Abstract
Overlap of footprints of light emitting diodes (LEDs) increases the positioning accuracy of wearable LED indoor positioning systems (IPS) but such an approach assumes that the footprint boundaries are defined. In this work, we develop a mathematical model for defining the footprint boundaries [...] Read more.
Overlap of footprints of light emitting diodes (LEDs) increases the positioning accuracy of wearable LED indoor positioning systems (IPS) but such an approach assumes that the footprint boundaries are defined. In this work, we develop a mathematical model for defining the footprint boundaries of an LED in terms of a threshold angle instead of the conventional half or full angle. To show the effect of the threshold angle, we compare how overlaps and receiver tilts affect the performance of an LED-based IPS when the optical boundary is defined at the threshold angle and at the full angle. Using experimental measurements, simulations, and theoretical analysis, the effect of the defined threshold angle is estimated. The results show that the positional time when using the newly defined threshold angle is 12 times shorter than the time when the full angle is used. When the effect of tilt is considered, the threshold angle time is 22 times shorter than the full angle positioning time. Regarding accuracy, it is shown in this work that a positioning error as low as 230 mm can be obtained. Consequently, while the IPS gives a very low positioning error, a defined threshold angle reduces delays in an overlap-based LED IPS. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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28 pages, 1077 KiB  
Article
Optical Wireless Communication Based Indoor Positioning Algorithms: Performance Optimisation and Mathematical Modelling
by Manisha Ajmani, Sinan Sinanović and Tuleen Boutaleb
Computation 2019, 7(1), 1; https://0-doi-org.brum.beds.ac.uk/10.3390/computation7010001 - 20 Dec 2018
Cited by 3 | Viewed by 4793
Abstract
In this paper, the performance of the optimal beam radius indoor positioning (OBRIP) and two-receiver indoor positioning (TRIP) algorithms are analysed by varying system parameters in the presence of an indoor optical wireless channel modelled in line of sight configuration. From all the [...] Read more.
In this paper, the performance of the optimal beam radius indoor positioning (OBRIP) and two-receiver indoor positioning (TRIP) algorithms are analysed by varying system parameters in the presence of an indoor optical wireless channel modelled in line of sight configuration. From all the conducted simulations, the minimum average error value obtained for TRIP is 0.61 m against 0.81 m obtained for OBRIP for room dimensions of 10 m × 10 m × 3 m. In addition, for each simulated condition, TRIP, which uses two receivers, outperforms OBRIP and reduces position estimation error up to 30%. To get a better understanding of error in position estimation for different combinations of beam radius and separation between light emitting diodes, the 90th percentile error is determined using a cumulative distribution frequency (CDF) plot, which gives an error value of 0.94 m for TRIP as compared to 1.20 m obtained for OBRIP. Both algorithms also prove to be robust towards change in receiver tilting angle, thus providing flexibility in the selection of the parameters to adapt to any indoor environment. In addition, in this paper, a mathematical model based on the concept of raw moments is used to confirm the findings of the simulation results for the proposed algorithms. Using this mathematical model, closed-form expressions are derived for standard deviation of uniformly distributed points in an optical wireless communication based indoor positioning system with circular and rectangular beam shapes. Full article
(This article belongs to the Special Issue Optical Wireless Communication Systems)
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