Dissertations / Theses: 'Optical wireless communication (OWC)'

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Yu, Zhenhua. "Optical wireless communications with optical power and dynamic range constraints." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51784.

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Along with the rapidly increasing demand for wireless data while more and more crowded radio frequency (RF) spectrum, optical wireless communications (OWC) become a promising candidate to complement conventional RF communications, especially for indoor short and medium range data transmissions. Orthogonal frequency division multiplexing (OFDM) is considered for OWC due to its ability to boost data rates. However, the average emitted optical power and dynamic range of driving signals of LEDs are two major constraints in OWC. OFDM waveforms exhibits high upper and lower peak-to-average power ratios (PAPRs), which make OFDM signals optical power inefficient and easy to violate the dynamic range of LEDs, resulting clipping and nonlinear distortions. In this dissertation, we analyze and design optical power and dynamic range constrained OWC systems, for which OFDM is our major subject. We first derive distributions of upper PAPR and lower PAPR of OWC-OFDM signals. Then we analyze the clipped OFDM signals in term of error vector magnitude (EVM), signal-to-distortion ratio (SDR), and achievable data rates under both optical power and dynamic range constraints. The next part of this dissertation is the OFDM system design for visible light communications (VLC) considering illumination requirement. We investigate the illumination-to-communication efficiency (ICE) in VLC-OFDM, and design the brightness control and flickering mitigation schemes for VLC-OFDM. In the end, to reduce the complexity of driving circuits of LEDs , we propose using delta-sigma modulators in VLC-OFDM systems to convert continuous magnitude OFDM symbols into two-level LED driver signals without loss of the communication theory advantages of OFDM.

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Sekkiou, Imene. "Design of communication systems based on broadband sources for fiber and free space optical links." Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/172542.

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[ES] Las comunicaciones ópticas inalámbricas (OWC) constituyen una tecnología muy prometedora para el desarrollo de futuras comunicaciones inalámbricas. De hecho, ha despertado un interés creciente entre los investigadores y varias empresas de todo el mundo trabajan actualmente en el desarrollo de redes inalámbricas de muy alta velocidad. Las comunidades científica e industrial consideran la OWC como una tecnología complementaria en sus diversas formas: comunicaciones ópticas en el espacio libre (FSO), comunicaciones de luz visible (VLC) o fidelidad de la luz (Li-Fi). El espectro óptico ha sido considerado durante muchos años como una gran oportunidad para las comunicaciones inalámbricas, especialmente debido a la saturación del espectro de radiofrecuencia (RF). Esta disertación trata del uso de fuentes de banda ancha en sistemas de transmisión de luz visible (VLC), así como en sistemas de transmisión en el espectro infrarrojo por fibra óptica. En el trabajo de investigación realizado se pueden distinguir tres partes: En la primera parte, se considera el estudio y la simulación de componentes de Diodos Emisores de Luz (LED) con el software WIEN2k centrándose en las propiedades ópticas y eléctricas de los elementos II-VI. La segunda parte trata del diseño, la implementación y las pruebas de diferentes prototipos de comunicación VLC para la transmisión analógica y digital en modo simplex y semidúplex. Hemos demostrado un sistema OWC empleando una fuente de banda ancha (LED) para la transmisión no sólo de datos, sino también para la transmisión inalámbrica de energía. Además, se aborda el problema de la sincronización y la detección del nivel "1" o "0" de un bit en los sistemas de comunicación inalámbrica óptica implementados que surge como consecuencia de la atenuación de la luz a lo largo de la distancia y al problema de la pérdida de línea de visión (NLOS) entre el emisor y el receptor. Para hacer frente a este problema, se ha proporcionado un protocolo de comunicación que garantiza la transmisión fiable de datos digitales con un algoritmo de detección de nivel de bits adaptativo y se ha demostrado su eficacia mediante la transmisión de textos e imágenes. Además, esta tesis aporta una solución para la implementación de transmisores multiplexados en redes con división de longitud de onda (WDM) para formatos de modulación con multiplexación por división de frecuencia ortogonal (OFDM) basados en el uso de fuentes de banda ancha en el espectro infrarrojo para redes de fibra bidireccionales centralizadas. A pesar de las limitaciones impuestas por la dispersión cromática en el uso de este tipo de fuentes ópticas, la inclusión de ciertas estructuras antes de la detección permite la transmisión de señales OFDM en enlaces ópticos. En este trabajo se ha demostrado experimentalmente la reutilización de portadoras, la asignación dinámica de ancho de banda y la transmisión de señales OFDM multibanda mediante el uso de fuentes ópticas de banda ancha en redes WDM. Los principales resultados obtenidos en cada parte de esta tesis doctoral muestran los procedimientos de estudio, la eficacia de las soluciones propuestas y las limitaciones encontradas.
[CA] Les comunicacions òptiques sense fils (OWC) constitueixen una tecnologia molt prometedora per al desenvolupament de futures comunicacions sense fils. De fet, ha despertat un interés creixent entre els investigadors i diverses empreses de tot el món treballen actualment en el desenvolupament de xarxes sense fils de molt alta velocitat. Les comunitats científica i industrial consideren la OWC com una tecnologia complementària en les seues diverses formes: comunicacions òptiques en l'espai lliure (FSO), comunicacions de llum visible (VLC) o fidelitat de la llum (Li-Fi). L'espectre òptic ha sigut considerat durant molts anys com una gran oportunitat per a les comunicacions sense fils, especialment a causa de la saturació de l'espectre de radiofreqüència (RF). Aquesta dissertació tracta de l'ús de fonts de banda ampla en sistemes de transmissió de llum visible (VLC), així com en sistemes de transmissió en l'espectre infraroig per fibra òptica. En el treball de recerca realitzat es poden distingir tres parts: ¿ En la primera part, es considera l'estudi i la simulació de components de Díodes Emissors de Llum (LED) amb el software WIEN2k centrant-se en les propietats òptiques i elèctriques dels elements II-VI. ¿ La segona part tracta del disseny, la implementació i les proves de diferents prototips de comunicació VLC per a la transmissió analògica i digital de manera simplex i semidúplex. Hem demostrat un sistema OWC emprant una font de banda ampla (LED) per a la transmissió no sols de dades, sinó també per a la transmissió sense fil d'energia. A més, s'aborda el problema de la sincronització i la detecció del nivell "1" o "0" d'un bit en els sistemes de comunicació sense fil òptica implementats, que sorgeix a conseqüència de l'atenuació de la llum al llarg de la distància i al problema de la pèrdua de línia de visió (NLOS) entre l'emissor i el receptor. Per a fer front a aquest problema, s'ha proporcionat un protocol de comunicació que garanteix la transmissió fiable de dades digitals amb un algorisme de detecció de nivell de bits adaptatiu i s'ha demostrat la seua eficàcia mitjançant la transmissió de textos i imatges. ¿ A més, aquesta tesi aporta una solució per a la implementació de transmissors multiplexats en xarxes amb divisió de longitud d'ona (WDM) per a formats de modulació amb multiplexació per divisió de freqüència ortogonal (OFDM) basats en l'ús de fonts de banda ampla en l'espectre infraroig per a xarxes de fibra bidireccionals centralitzades. Malgrat les limitacions imposades per la dispersió cromàtica en l'ús d'aquest tipus de fonts òptiques, la inclusió d'unes certes estructures abans de la detecció permet la transmissió de senyals OFDM en enllaços òptics. En aquest treball s'ha demostrat experimentalment la reutilització de portadores, l'assignació dinàmica d'amplada de banda i la transmissió de senyals OFDM multibanda mitjançant l'ús de fonts òptiques de banda ampla en xarxes WDM. Els principals resultats obtinguts en cada part d'aquesta tesi doctoral mostren els procediments d'estudi, l'eficàcia de les solucions proposades i les limitacions trobades.
[EN] Optical wireless communication (OWC) is a very promising technology for future wireless communications developments. It has attracted increasing interest from researchers and several companies around the world are currently working on the development of very high-speed wireless networks. The scientific and industrial communities believe that OWC will be a complementary technology in its various forms: Free Space Optical communications (FSO), Visible Light Communications (VLC), Light Fidelity (Li-Fi). In fact, the optical spectrum has been considered for many years as a great opportunity for wireless communications especially due to the saturation of the radio frequency (RF) spectrum. This dissertation deals with the use of broadband sources in visible light transmission systems (VLC) as well as fiber optic systems. To carry out the research, three parts can be distinguished: In the first part, we consider the study and simulation of Light Emitting Diode (LED) components with the WIEN2k software by focusing on the optical and electrical properties of elements II-VI. The second part deals with the design, implementation and testing of different VLC communication prototypes for analog and digital transmission in simplex and half-duplex mode. We have demonstrated that an OWC system using a broadband source (i.e. an LED) can be used not only for data transmission, but also for wireless power transmission. Moreover, the synchronization problem and the detection of level "1" or "0" of a bit often arise in the optical wireless communication systems. This is a result of the attenuation nature of the light over the distance and the problem of Non Line-Of-Sight (NLOS) between the emitter and the receiver. To deal with this problem, a communication protocol ensuring reliable digital data transmission with an adaptive bit level detection algorithm has been provided and its effectiveness has been demonstrated by the transmission of texts and images. In addition, this thesis provides a solution for the implementation of wavelength division multiplexed - orthogonal frequency division multiplexed (WDM-OFDM) transmitters based on the use of broadband sources in the infrared spectrum for centralized bidirectional fiber networks. Despite the chromatic dispersion that avoids the use of this type of optical sources, the inclusion of certain structures before detection allows the transmission of OFDM signals in optical links. Carrier reuse, dynamic bandwidth allocation and multiband OFDM signals transmission will be experimentally demonstrated by using optical broadband sources in WDM networks. The main results obtained during this thesis work demonstrate the study procedures, for each part, the effectiveness of the proposed solutions as well as the constraints encountered.
Sekkiou, I. (2021). Design of communication systems based on broadband sources for fiber and free space optical links [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172542
TESIS

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Jiang, Junyi. "Optical wireless communication systems." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/387239/.

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In recent years, Optical Wireless (OW) communication techniques have attracted substantial attention as a benefit of their abundant spectral resources in the optical domain, which is a potential solution for satisfying the ever-increasing demand for increased wireless capacity in the conventional Radio Frequency (RF) band. Motivated by the emerging techniques and applications of OW communication, the Institute of Electrical and Electronics Engineers (IEEE) had released the IEEE standard 802.15.7 for short-range optical wireless communications, which categorised the Physical layer (PHY) of the OW communication into three candidate-solutions according to their advantages in different applications and environments: 1) Physical-layer I (PHY I): Free Space Optical (FSO)communication employs high-intensity Light Emitting Diodes (LEDs) or Laser Diodes (LDs) as its transmitter. 2) Physical-layer II (PHY II) uses cost-effective, low-power directional white LEDs for the dual function of illumination and communication. 3) Physical III (PHY-III) relies on the so-called Colour-Shift Keying (CSK) modulation scheme for supporting high-rate communication. Our investigations can be classified into three major categories, namely Optical Orthogonal Frequency Division Multiplexing (OFDM) based Multiple-Input Multiple-Output (MIMO) techniques for FSO communications in the context of PHY I, video streaming in PHY-II and the analysis and design of CSK for PHY-III. To be more explicit, in Chapter 2 we first construct a novel ACO-OFDM based MIMO system and investigate its performance under various FSO turbulence channel conditions. However, MIMO systems require multiple optical chains, hence their power consumption and hardware costs become substantial. Hence, we introduced the concept of Aperture Selection (ApS) to mitigate these problems with the aid of a simple yet efficient ApS algorithm for assisting our ACO-OFDM based MIMO system. Since the channel conditions of indoor Visible Light Communication (VLC) environments are more benign than the FSO-channels of Chapter 2, directional white LEDs are used to create an “attocell” in Chapter 3. More specifically, we investigate video streaming in a multi-Mobile Terminals (MTs) indoor VLC system relying on Unity Frequency Reuse (UFR) as well as on Higher Frequency Reuse Factor based Transmission (HFRFT) and on Vectored Transmission (VT) schemes. We minimise the distortion of video streaming, while satisfying the rate constraints as well as optical constraints of all the MTs. In Chapter 4 we analyse the performance of CSK relying both on joint Maximum Likelihood (ML) Hard-Detection (HD), as well as on the the Maximum A posteriori (MAP) criterion-based Soft-Detection (SD) of CSK. Finally, we conceive both two- stage and three-stage concatenated iterative receivers capable of achieving a substantial iteration gain, leading to a vanishingly low BER.

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Du, Hao. "Optical wireless MIMO communication." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/70945/.

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This thesis provides an in-depth investigation and evaluation of infrared optical wireless MIMO communication systems to be applied in both indoor and outdoor environment. The principle objective of the research is to demonstrate both the advantages and disadvantages of the optical wireless MIMO systems using different modulation types. The first part provided analyses of important OW configurations using APD receivers using WMC model and SISO, MISO, SIMO and MIMO configuration. Thus, an analytical expression for 2-1 MISO, 1-2 SIMO and MIMO was successfully developed. This part also illustrates the coding gains possible using diversity schemes for APD OW systems. In the presence of strong fading, the SISO approach is rendered virtually useless, whereas diversity offers acceptable BER values. The results underpin the approach of this thesis, where indoor PIN diode based experimental measurements confirm the gains offered by diversity. In the second part of the work, several optical wireless MIMO systems applicable for the indoor environment are developed for three different modulation types, OOK modulation, PPM modulation and SIR-RZI modulation. These modulations are used in optical MIMO systems are studied for which, mathematical models that evaluate the BER performance of the MIMO system for different axis displacement and for different distances between transmitters and receivers. Based on the results, the PPM system has been shown to present the best BER performance, including high interference-resistance capability. A group of new mathematical models have been evaluated, which demonstrates a high level of correlation with the results derived from empirical models at 93%. Thus, the mathematical models developed and used for the specified evaluation appear to correspond reasonably well, and can be applied in future research on these aspects.

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Boussebt, Amina. "Etude et mise en oeuvre de la technologie Li-Fi pour un lit de bébé connecté sans fil et sans radio." Electronic Thesis or Diss., Limoges, 2023. http://www.theses.fr/2023LIMO0091.

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Le domaine de la télésurveillance a connu un grand essor ces dernières décennies et concerne divers contextes par exemple en milieu hospitalier, en maison de retraite, chez les particuliers. La majorité des systèmes de télésurveillance existants aujourd’hui reposent sur la technologie des radiofréquences (RF). Nous proposons dans cette thèse, des travaux portant sur la télésurveillance dans un contexte nouveau qui concerne une crèche. Les RF présentant certains inconvénients, comme l’impact des interférences électromagnétiques, mais aussi des failles de sécurité, une solution alternative est la technologie de communication par optique sans fil. Ainsi, nous avons étudié l'utilisation de la technologie infrarouge pour la transmission simultanée de données issues de capteurs placés sur les pieds des lits de bébé mais aussi sur les bébés couchés dans leur lit au sein de la crèche. Le système de réception est constitué de photodiodes situées aux coins d'un panneau d'éclairage central au plafond de l'environnement. La simulation du canal réalisée grâce à la technique de lancer de rayons associés à la méthode de Monte-Carlo a permis de déterminer le gain du canal pour chaque dispositif. Plusieurs scénarios de déploiement ont été définis en considérant le caractère amovible ou fixe des dispositifs et l’interchangeabilité des lits dans la pièce. Le partage du canal utilise la technique d’accès multiple par répartition de codes (OCDMA) associée aux codes optiques orthogonaux (OOC) dont la principale limitation est l’interférence d’accès multiple (IAM). Les performances de la modulation binaire par position d’impulsion (2-PPM) avec OCDMA et un décodage souple en réception ont été établies théoriquement et par simulation pour les différents scénarios définis considérant un réseau de 11 utilisateurs constitué de 8 lits et 3 dispositifs portés par des bébés. Les résultats ont été obtenus avec des récepteurs conventionnels par corrélation sans et avec limiteur puis un récepteur à annulation parallèle d’interférence plus efficace pour réduire l’impact de l’IAM. De plus, la faisabilité de l’utilisation de la technique OCDMA pour la transmission simultanée en optique sans fil a été mise en évidence par des expérimentations menées grâce à un banc de test développé en radio logicielle. Le banc a été mis en place, en utilisant des USRP (Universal Software Radio Peripheral) et des front-ends optique sans fil développés spécifiquement
The field of the remote monitoring has experienced significant advancements in recent decades, and now covers different contexts, such as hospitals, retirement homes, and private homes also. The majority of existing systems are based on radio frequency technology (RF).We propose in this thesis, research focused on remote monitoring in a new context involving a nursery. Given the limitations of RF technology, including the impact of electromagnetic interference, and security vulnerabilities, an alternative solution is optical wireless communication technology. Therefore, we investigated the use of infrared technology for simultaneous transmission of data collected from sensors placed on the foot of baby beds, and also on the babies themselves lying in their beds within the nursery. The reception system consists of photodiodes positioned at the corners of a central lighting panel on the celling. The channel simulation carried out using ray-tracing and Monte-Carlo methods was used to determine the channel gain for each device. Several deployment scenarios were defined, considering the nature of the devices (removable or fixed) and the interchangeability of beds in the room. The channel sharing employs the code division multiple access (OCDMA) associated with the optical orthogonal codes (OOC) with the primary constraint being the137 multiple access interference (MAI). The performance of binary pulse position modulation (2- PPM) with OCDMA and soft decoding in reception was studied theoretically and by simulation involving the different scenarios. These scenarios consider a network of 11 users, consisting of 8 beds and 3 devices carried by babies. Results were obtained using the conventional correlation receiver without and with hard limiters, as well as a parallel interference cancellation receiver to reduce the impact of MAI. Additionally, the feasibility of implementing OCDMA technology for simultaneous optical wireless communication transmission was demonstrated through experimental work using a test bench developed in software-defined radio. The test bench was established using universal software radio peripheral (USRP), and specially designed wireless optical front-ends

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Alhartomi, Mohammed. "Collaborative optical wireless communication systems." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/13153/.

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Zeng, Zhaoquan. "A survey of underwater wireless optical communication." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55675.

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Underwater wireless communication refers to transmitting data in unguided water environment through the use of wireless carriers, i.e., radio-frequency wave, acoustic wave, and optical wave. We focus, in this thesis, on the underwater wireless optical communication (UWOC) that employs optical wave as the transmission carriers. In comparison to RF and acoustic counterparts, UWOC has a much higher transmission bandwidth, thus providing much higher data rate. Due to this high-speed transmission advantage, UWOC has attracted considerable attention in recent years. Many potential applications of UWOC systems have been proposed for environmental monitoring, offshore exploration, disaster precaution, and military operations. However, UWOC systems also suffer from severe absorption and scattering introduced by underwater channel. In order to overcome these technical challenges, several new system design approaches, which are different from the conventional terrestrial free-space optical communication, have been explored in recent years. In this thesis, we provide a comprehensive survey of the state-of-the-art of UWOC research in three aspects: channel characterization, channel modulation and coding techniques, and practical implementations of UWOC. Based on the comprehensive understanding of UWOC, we also investigate the outage performance for vertical buoy-based UWOC with pointing errors. Closed-form outage probability with zero boresight pointing errors and outage probability bounds with nonzero boresight pointing errors have been derived.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

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Brundage, Heather. "Designing a wireless underwater optical communication system." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57699.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 61-63).
Though acoustic modems have long been the default wireless communication method for underwater applications due to their long range, the need for high speed communication has prompted the exploration of non-acoustic methods that have previously been overlooked due to their distance limitations. One scenario that drives this need is the monitoring of deep sea oil wells by AUVs that could be stationed at the well and communicate surveillance data wirelessly to a base station. In this thesis, optical communication using LEDs is presented as an improvement over acoustic modems for scenarios where high speed, but only moderate distances, is required and lower power, less complex communication systems are desired. A super bright blue LED based transmitter system and a blue enhanced photodiode based receiver system were developed and tested with the goal of transmitting data at rates of 1 Mbps over distances of at least 10 meters. Test results in a fresh water tow tank showed the successful transmission of large data files over a distance of 13 meters and at transmission rates of at least 3 Mbps. With an improved test environment, even better performance may be possible.
by Heather Brundage.
S.M.

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Parand, Farivar. "Cellular optical wireless communications systems." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270654.

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Azim, Ali Waqar. "Signal Processing Techniques for Optical Wireless Communication Systems." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAT059/document.

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Le spectre radiofréquence (RF) diminue en raison d'une augmentation de la demande d'applications sans fil. Par conséquent, il existe une demande importante de régions de spectre alternatifs pour les communications afin d'incliner le spectre RF conventionnel. Dans ce contexte, les communications optiques sans fil (OWC) sont explorées comme un candidat potentiel pour compléter les communications RF. Le travail actuel se concentre sur les techniques d'atténuation des déficiences et les approches de modulation efficaces en énergie pour OWC. Dans un premier temps, on étudie le rapport de puissance crête à moyenne (PAPR) pour le multiplexage par répartition orthogonale de la fréquence optique (O-OFDM) et on présente deux techniques de réduction de PAPR orientées vers la décision. La complexité de ces méthodes est comparativement plus faible que celle des autres méthodes de réduction PAPR, tandis que leurs performances sont également analogues à celles des autres alternatives. Deuxièmement, une approche d'accès multiple par répartition en fréquence optique-porteuse unique (O-SCFDMA), appelée O-SCFDMA sans symétrie d'Hermitain (HSFO-SCFDMA) est proposée. Ce dernier évite la symétrie hermiatienne normalement attendue pour d'autres O-OFDM et Approches O-SCFDMA. Les résultats de la simulation affirment que HSFO-SCFDMA est plus efficace que toute autre approche O-SCFDMA pour OWC et manifeste le plus faible PAPR parmi les autres alternatives. Troisièmement, la performance du précodage est analysée pour l'O-OFDM (LACO-OFDM) asymétriquement en couches. Deux types de précodage sont utilisés, à savoir le précodage par transformée de Fourier et le précodage par transformée d'Hartley. Il est établi que le LACO-OFDM précodé a transformée Hartley présente le PAPR le plus faible et est moins vulnérable à la distorsion non linéaire introduite par les diodes électroluminescentes (LED), mais le rapport signale sur bruit (SNR) augmente ( électrique et optique à la fois) en raison de la structure en couches qui est plus élevée que le LACO-OFDM conventionnelle
The radio-frequency (RF) spectrum is dwindling due to an increase in the demand of wireless applications. Hence, there is substantial demand of alternative spectrum regions for communications to recline the conventional RF spectrum. In this context, optical wireless communications (OWC) is explored as a likely candidate to supplement the RF communications. The current work focuses on impairment mitigation techniques and energy-efficient modulation approaches for OWC. Firstly, the peak-to-average power ratio (PAPR) for optical-orthogonal frequency division multiplexing (O-OFDM) is studied and two decision-directed PAPR reduction techniques are presented. The complexity of these methods is comparatively lower than other PAPR reduction methods, whilst, their performance is likewise analogous with other alternatives. Secondly, an optical-single-carrier frequency division multiple access (O-SCFDMA) approach, referred to as Hermitain symmetry free O-SCFDMA (HSFO-SCFDMA) is proposed, that averts Hermiatian symmetry which is normally expected for other O-OFDM and O-SCFDMA approaches. The simulation results affirm that HSFO-SCFDMA is more efficient than any other O-SCFDMA approach for OWC and manifests the lowest PAPR among the other alternatives. Thirdly, the performance of precoding is analyzed for layered asymmetrically clipped O-OFDM (LACO-OFDM). Two types of precoding are employed, i.e., Fourier transform precoding and Hartley transform precoding. It is established that Hartley transform precoded LACO-OFDM exhibits the lowest PAPR and is less vulnerable to non-linear distortion introduced by the light emitting diodes (LEDs), howbeit, the signal-to-noise ratio (SNR) increase (both electrical and optical) owing to the layered structure is higher than conventional LACO-OFDM

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Zeng, Yu. "Adaptive modulation schemes for optical wireless communication systems." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/3837/.

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High-speed wireless optical communication links have become more popular for personal mobile applications. This is a consequence of the increasing demand from the personal information service boom. Compared to the radio frequency domain, optical wireless communication offers much higher speeds and bit rates per unit power consumption. As stated by the official infrared standard IrDA optical communication enjoys much lower power consumption than Bluetooth, with an inherent security feature while in Line of Sight (LOS) applications. There are also drawbacks such as the infrared radiation cannot penetrate walls as radio frequencies do and interference from the background contribute to the channel dispersions. Focus on the modulation aspects of the optical wireless communication, this thesis try to improve the channel immunity by utilising optimised modulation to the channel. Modulation schemes such as on off keying (OOK), pulse amplitude modulation (PAM) and pulse position modulation (PPM) and pulse position and amplitude modulation PAPM schemes have been validated. The combined power and bandwidth requirements suggest that the adaptive modulation schemes can provide reliability when deployed in a real time channel, resulting in improved system performance. As a result, an adaptive modulation technique is proposed. Extensive simulations of severe noise distraction have been carried out to validate the new scheme. The simulation results indicate that the new scheme can provide increased immunity against channel noise fluctuation at a relatively low complexity. The scheme obtained formed a basis to support reliable mobile optical wireless communication applications. The adaptive scheme also takes the real time channel conditions into account, which is different from existing schemes. Guaranteed system performance can be secured without compromising power and bandwidth efficiency. This is also a new approach to realise reliable optical wireless links. Fuzzy logic control module has been developed to match the adaptive pattern.

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Gatri, Aymen. "Performance optimisation mechanisms for optical wireless communication systems." Thesis, Northumbria University, 2017. http://nrl.northumbria.ac.uk/36263/.

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In this day and age, free space optical (FSO) enable the deployment of a new category of products that can transmit voice, data, and video at bandwidths up to 2.5 Gbps at distances up to 4 km, over any protocol. This optical connectivity doesn’t require expensive fibre-optic cable or spectrum licenses. FSO is reliable due to the capability of FSO systems to provide truly broadband and secure communications, as well as their immunity to interference from other sources of optical radiation. The principal challenge facing FSO technology is to achieve 100% link availability in all weather conditions. While rain, fog, haze, turbulence and aerosols all attenuate the optical signal to a certain level, fog is considered to be the main impairment in FSO systems. Thick fog resulting in over 300 dB/km of signal attenuation can reduce the transmission span from a few kilometres to just 100 m or so. Turbulence (i.e. scintillation) also results in reducing fade margins from 4 to 10 dB for FSO links of 1 km length or less, which is well below the margins for atmospheric attenuation. In the real-world environment, it is very challenging to measure the effect of atmospheric fog under diverse circumstances. This is due to several reasons: (i) the longer observation time required and the lower probability of reoccurrence of dense fog events for visibility V < 0.5 km, and (ii) the difficulty in controlling and characterising aerosols in the atmosphere, due to the inhomogeneous presence of aerosols along the FSO link path. This thesis examines and analyses the performance of a terrestrial FSO system by investigating the impact of a number of modulation techniques on mitigating the atmospheric impairments. A dedicated indoor atmospheric chamber is designed to carry out tests and measurements in a controlled manner and mimic the real outdoor atmosphere. The experimental results are compared with predicted data for the range of modulation techniques tested in the presence of atmospheric turbulence and fog, including binary phase shift keying subcarrier intensity modulation (BPSK-SIM), 2-pulse position modulation (2-PPM), 4-pulse position modulation (4-PPM) and hybrid pulse position modulation binary phase shift keying subcarrier intensity modulation (BPSK-SIM-PPM).The results show that BPSK-SIM-PPM offers a similar performance to 2-PPM, a superior performance to BPSK-SIM, while having the same bandwidth, and an inferior performance to 4-PPM under turbulent conditions. Furthermore, the experimental investigation indicates that 4-PPM is more resistant to turbulence compared to BPSK-SIM. The improvement of the link performance by optimising the beam spot size using combinations of mirrors is also investigated. In addition, the effects of low to high visibility on the FSO link BER performance in the presence of fog are measured and investigated. The obtained results indicate the dependency of the performance of the FSO link on the fog intensity variation. Moreover, the experimental results show that the impact of severe fog induced attenuation is greater on the receiver than the transmitter. Finally, the effect of fog on an FSO system employing quadrature phase-shift keying (QPSK) and operating at various carrier wavelengths is also studied.

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Marco, Rider Jaime. "Optical communication with underwater snake robots : Design and implementation of an underwater wireless optical communication system." Thesis, Mittuniversitetet, Institutionen för elektronikkonstruktion, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-37803.

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Eelume AS is a norwegian company that develops autonomous underwater vehicles. Their flagship model is an underwater snake robot that performs inspection, maintenance and repair operations. For the time being, Eelume has been using acoustic communications between their AUV's and the docking station, but it has a big drawback: bandwidth. Eelume is interested in streaming live high-quality video from their AUV's to the docking station, which requires several megabits per second. As underwater radio frequency communications are not possible, wireless optical communications seem to be the best available alternative. The focus of this Thesis is to design an underwater wireless optical communications system that could be implemented on the Eelume AUV, although it is designed as a standalone embedded system that could be integrated into any other platform. Two prototypes were designed and tested through-air: a low-cost system featuring a PIN photodiode that can stream a 1.5 Mbps video signal over 0.5 meters and a high-sensitivity system featuring an avalanche photodiode that can stream a 2.5 Mbps video signal over 10.5 meters. Even if further underwater testing is needed and some inherent limitations in the design like the precise calibration or the ambient light noise effects could be mitigated. The results achieved by this high-sensitivity system demonstrates that a high-bandwidth mid-range underwater wireless optical communication system featuring a blue/green LED array as the light source and an avalanche photodiode as the photodetector is a viable solution for streaming live high-quality video over several meters even in very turbid seawaters.

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Ogunkoya, Funmilayo Bimpe. "PAPR reduction for OFDM in optical wireless communication systems." Thesis, Glasgow Caledonian University, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.726783.

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Abaza, Mohamed. "Cooperative MIMO techniques for outdoor optical wireless communication systems." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0073/document.

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Au cours de la dernière décennie, les communications optiques en espace libre (FSO) ont pris de l’ampleur dans les deux domaines académiques et industriels. L’importance de FSO s’appuie sur la possibilité de faire un système de transmission économique et écologique avec un débit élevé et sans licence à l’opposition des systèmes de transmission radiofréquences (RF). Dans la plupart des travaux antécédents sur les systèmes multi-émetteurs, seulement les canaux décorrélés ont été considérés. Un canal décorrélé nécessite un espace suffisant entre les émetteurs. Cette condition devient difficile et non-réalisable dans certaines applications. Pour cette raison, nos études se focalisent sur les performances des codes à répétition RC (Repitition Codes) et les codes OSTBC (Orthogonal Space-Time Block Codes) dans des canaux log-normaux corrélés en utilisant une modulation d’intensité et une détection directe (IM/DD). En addition, les effets des différentes conditions météorologiques sur le taux d’erreur moyen (ABER) sont étudiés. Les systèmes FSO à multi-entrées/ multi-sorties MIMO (Multiple-Input Multiple-Output) avec une modulation SSK (Space Shift Keying) ont été abordés. Les résultats obtenus montrent que la SSK est supérieure aux RC avec une modulation d’impulsion (Multiple Pulse Amplitude Modulation) pour toute efficacité spectrale égale ou supérieure à 4 bit/s/Hz. Nous avons aussi analysé les performances d’un système à sauts multiples (Multi-Hop) et des relais à transmission directe (forward relays). Nos simulations montrent que le système ainsi considéré est efficace pour atténuer les effets météorologiques et les pertes géométriques dans les systèmes de communication FSO. Nous avons montré qu’un tel système avec plusieurs entrées et une sortie (MISO, i.e. multiple-input single-output) à sauts multiples est supérieur à un système MISO avec un lien direct (direct link) avec une forte atténuation. Pour satisfaire la demande croissante des réseaux de communication à débits élevés, la communauté scientifique s'intéresse de plus en plus aux systèmes FSO avec des relais full-duplex (FD). Pour ces derniers systèmes, nous avons étudié la probabilité d'erreur moyenne (ABER) et nous avons analysé leurs performances. En considérant des différentes conditions de transmission, les performances de relais FD ont été comparées à celles d'un système avec un lien direct ou des relais half-duplex. Les résultats obtenus montrent que les relais FD ont le minimum ABER. En conséquence, les résultats obtenus dans cette thèse sont très prometteurs pour la prochaine génération de FSO
Free-space optical (FSO) communication has been the subject of ongoing research activities and commercial attention in the past few years. Such attention is driven by the promise of high data rate, license-free operation, and cheap and ecological friendly means of communications alternative to congested radio frequency communications. In most previous work considering multiple transmitters, uncorrelated channel conditions have been considered. An uncorrelated channel requires sufficient spacing between transmitters. However, this can be difficult and may not be always feasible in some applications. Thereby, this thesis studies repetition codes (RCs) and orthogonal space-time block codes performance in correlated log-normal FSO channels using intensity modulation and direct detection (IM/DD). Furthermore, the effect of different weather conditions on the average bit error rate (ABER) performance of the FSO links is studied. Multiple-input multiple-output (MIMO) FSO communication systems using space shift keying (SSK) modulation have been also analyzed. Obtained results show that SSK is a potential technique for spectral efficiencies equal or greater than 4 bits/s/Hz as compared to RCs with multiple pulse amplitude modulations. The performance analysis of a multi-hop decode and forward relays for FSO communication system using IM/DD is also considered in this thesis. It is shown that multi-hop is an efficient technique to mitigate atmospheric turbulence and different weather attenuation effects and geometric losses in FSO communication systems. Our simulation results show that multiple-input single-output (MISO) multi-hop FSO systems are superior to direct link and MISO systems over links exhibiting high attenuation. Meeting the growing demand for higher data rates communication networks, a system with full-duplex (FD) relays is considered. For such a system, the outage probability and the ABER performance are analyzed under different turbulence conditions, misalignment error and path loss effects. FD relays are compared with the direct link and half-duplex relays. Obtained results show that FD relays have the lowest ABER and the outage probability as compared to the two other systems. Finally, the obtained results in this thesis are very promising towards the next generation of FSO systems

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Mahdy, Ahmed M. "A broadband infrastructure for ad hoc networks with optical wireless." [Lincoln, Neb. : University of Nebraska-Lincoln], 2005. http://0-www.unl.edu.library.unl.edu/libr/Dissertations/2005/MahdyDis.pdf.

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Zhu, Ming. "High-capacity communication systems using advanced optical and wireless technologies." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53525.

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The increasing traffic demand from the use of 3G/4G, streaming, and other broadband wireless services exposes existing bottlenecks in the communications infrastructure and the coordination between the wireless network and its wired counterpart. While wireless systems are constantly evolving to newer generations and higher capacities, their supporting wired networks urgently require advancements in both architecture design and enabling technologies. New optical access systems specifically tailored for the unique natures of various wireless standards are investigated. This dissertation presents the design and experimental verification of high-capacity optical-wireless communication systems using advanced electrical and optical technologies. Technologies such as high level modulation and multiple-input and multiple-output (MIMO) to increase the spectral efficiency is approaching the Shannon limit. New frequency bands with larger bandwidth are to be explored; for example, millimetre wave (mm-wave) spectrum range (30-300 GHz), especially the license-free spectrum located in 60 GHz. Although fiber-optic systems excel in the high-bandwidth core network, as bandwidth demand increases, more and more progress has been made towards the usage of fiber in the last mile. Radio-over-Fiber (RoF) technology has been proposed as a cost-effective optical access solution to support high-speed wireless communications, especially at the mm-wave band. Signal processing and coordination are centralized at the central office (CO), making the system economical and simple to build, operate, and maintain. Moreover, RoF systems are capable of delivering radio signals with different frequencies and protocols simultaneously. Therefore, the advantage of integrated fiber wireless systems leads to the first research topic of this dissertation: multi-band multi-service RoF systems. With an emphasis on the uniformity of the RoF platform that accommodates both legacy wireless services and advanced mm-wave services, the first part of the dissertation presents two schemes - analog all-band RoF and band-mapped 60-GHz RoF - to cover distinct application scenarios. In the all-band RoF access architecture, lower RF signals, such as Wi-Fi and cellular signals, and 60-GHz signal are transmitted at their original carrier frequencies for both indoor and outdoor coverages. On the other hand, the band-mapped mm-wave RoF scheme, fully utilizing the wide 7-GHz bandwidth at 60 GHz, delivers multiple converged high-speed services only through 60-GHz wireless link, which is especially suited for in-building broadband wireless access. The experimental verification of an all-band RoF system featuring relaxed component requirement is introduced, followed by a real-time multi-service demonstration in the proposed band-mapped 60-GHz RoF system. This dissertation also presents the design, analysis, and experimental demonstration of next-generation high-capacity cellular networks to keep up with the ever-growing bandwidth demand and performance requirements. New mobile backhaul (MBH) architectures based on orthogonal frequency division multiple access (OFDMA) are proposed along with a simple and low-latency clock distribution and recovery scheme. The transmission of OFDMA signals in the dense wavelength division multiplexing (DWDM) network with flexible clock rates and DSP-free clock recovery is implemented. Also, a spectrally-efficient, low-complexity clock distribution and recovery scheme for OFDMA-based MBH in coherent ultra-dense WDM (UDWDM) system is demonstrated. Finally, mobile fronthaul (MFH) architectures based on subcarrier multiplexing (SCM) technology, which significantly reduces the requirements on both the number of wavelengths per cell site and the optical bandwidth of the optical transceivers, are systematically investigated. Additionally, two upstream schemes, tailored for the uplink (UL), are introduced to maintain low complexity, and more importantly, to achieve high spectral efficiency by wavelength sharing. Therefore, Internet-access-oriented optical-wireless systems using Wi-Fi and other emerging mm-wave technologies are developed along with the optical fronthaul and backhaul for cellular networks in this dissertation. Moreover, with the proposed techniques, heterogeneous networks can be seamlessly provided even with different services, radio nodes, and performance requirements.

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Hayes, Andrew Robert. "Digital pulse interval modulation for indoor optical wireless communication systems." Thesis, Sheffield Hallam University, 2002. http://shura.shu.ac.uk/7263/.

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Over the past decade, infrared has attracted a considerable amount of interest as an alternative medium to radio for short-range indoor wireless local area networks. Infrared offers a number of significant advantages over its radio frequency counterpart, such as the abundance of bandwidth that is currently unregulated worldwide, the availability of low cost emitters and detectors, inherent security and resistance to multi path fading. The work presented in this thesis focuses on modulation techniques, the fundamental aim being to assess the suitability of digital pulse interval modulation (DPIM) for use in indoor optical wireless communication systems. Infrared transceivers are subject to eye safety regulations, and consequently power efficiency is an important criterion when evaluating modulation techniques. From the error probability analysis carried out on the non-distorting additive white Gaussian noise channel, it is shown that DPIM is able to trade off power efficiency against bandwidth efficiency by increasing the number of bits per symbol. Furthermore, by encoding an additional bit per symbol, DPIM can outperform pulse position modulation (PPM) both in terms of power efficiency and bandwidth efficiency when simple threshold detection is employed. Indoor optical wireless systems generally operate in the presence of intense ambient light, emanating from both natural and artificial sources. Along with contributing to the generation of shot noise, artificial ambient light sources also introduce a periodic interference signal which can have a detrimental effect on link performance. Original analysis is presented which examines the error performance of DPIM in the presence of interference from a fluorescent lamp driven by a high-frequency electronic ballast, which is potentially the most degrading source of ambient light. It is found that such interference results in an average optical power requirement that is almost independent of the bit rate. The analysis then goes on to consider the effectiveness of electrical high-pass filtering as a simple means of mitigating the effect of the interference, taking into account the baseline wander introduced by the high-pass filter. DPIM was found to be more susceptible to the effects of baseline wander compared with PPM, a finding which is supported by the original analysis carried out on the power spectral density of the scheme. Consequently, whilst electrical high-pass filtering was found to be very effective at high bit rates, significant power penalties are still incurred at low to medium bit rates. In non-directed line of sight and diffuse link configurations, multipath propagation gives rise to intersymbol interference (ISI), which must be taken into account for data rates above 10 Mbit/s. Original analysis is presented which examines the unequalized performance of DPIM in the presence of ISI. From this analysis, it is found that on any given channel, the improved bandwidth efficiency of DPIM results in lower average optical power penalties, compared with PPM. One novel technique which can be used to make DPIM more resistant to the effects of ISI is to add a guard band to each symbol, immediately following the pulse. Original contributions are presented which evaluate the effectiveness of this technique. To quantify the results obtained, analysis is also carried out on DPIM using a zero-forcing decision feedback equalizer (ZF-DFE), which represents a more traditional approach to mitigating the effects of ISI. It is shown that the guard band technique offers a similar level of performance to the ZF-DFE on all but the most severe channels, and has the advantage of reduced cost and complexity compared with implementing a ZF-DFE. To support the theoretical and simulated performance of DPIM carried out in this thesis, details are given of a prototype 2.5 Mbit/s diffuse infrared link employing 16-DPIM which has been designed and constructed. The error performance of the link is measured under a variety of ambient light conditions, and the effectiveness of electrical high-pass filtering in mitigating the resulting interference is assessed. It is shown that whilst a fluorescent lamp driven by a high frequency electronic ballast has the potential to significantly degrade link performance, the power penalty introduced by this source can be made manageable by careful selection of the high-pass filter cut-on frequency.

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Abu, Almaalie Zina. "Free space optical wireless communication with physical layer network coding." Thesis, Northumbria University, 2016. http://nrl.northumbria.ac.uk/32546/.

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Terrestrial free-space optical (FSO) communications is an emerging low-cost, licensefree and high-bandwidth access solution for a number of applications including the “last mile” access network. However, for a transmission range from a few meter to longer than 1 km, a number of atmospheric phenomena, such as rain, haze, fog, snow, scintillation and pointing errors become a major performance limiting factors in FSO systems resulting in link deterioration and ultimately complete link failure. Relay-assisted technique is capable of mitigating the signal fading and maintain acceptable performance levels. In this thesis, a two-way relay (TWR) channel technique is adopted to increase system spectral efficiency, which in turn boosts the network throughput. This is achieved by using a physical layer network coding (PNC) technique, where network coding (NC) is applied at the physical layer. It takes advantage of the superimposition of the electromagnetic waves, and embraces the interference, which was typically deemed as harmful, by performing the exclusive-OR mapping of both users’ information at the relay. Therefore, the main contribution of this thesis is to study the design of the TWR-FSO communication system that embraces PNC technique for the full utilization of network resources based on the binary phase shift keying (BPSK) modulation. Moreover, error control coding (ECC) in conjunction with interleaving can be employed in FSO communications to combat turbulence-induced fading, which can enhance the performance of the proposed TWR-FSO PNC system. A comparative study between convolutional code (CC) and bit-interleave coded modulation with iterative decoding (BICM-ID) code are carried out. The result shows that the BICM-ID code outperforms the CC for TWR-FSO based PNC over strong turbulence regime by ~10dB of SNR to achieve a BER of 10-4 . However, the number of users that can be simultaneously transmitted to the relay is considered the main constraint in PNC system. Therefore, to overcome this challenge, a new scheme that integrates the iterative multiuser detection (I-MUD) technique with the PNC system over RF and FSO links are introduced as another achievement. The results show that the I-MUD offers improved performance about 8, and 22dB of SNR to get a BER of 10-4 over RF and FSO channels, respectively, for number of simultaneously users equal to 14 with respect to TWR-PNC system.

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Alsaadi, Fuad Eid S. "MIMO MC-CDMA systems over indoor optical wireless communication channels." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/1902/.

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Optical wireless communication systems offer a number of advantages over their radio frequency counterparts. The advantages include freedom from fading, freedom from spectrum regulations and abundant bandwidth. The main limitations of optical wireless systems include background noise attributed to natural and artificial light sources and multipath propagation. The former degrades the signal to noise ratio while the latter limits the maximum achievable data rate. This thesis investigates the use of transmit power adaptation in the design of optical wireless spot-diffusing systems to increase the power associated with the main impulse response components, resulting in a compact impulse response and a system that is able to achieve higher data rates. The work also investigates the use of imaging diversity receivers that can reject the background noise components received in directions not associated with the signal. The two techniques help improve the optical wireless system performance. The multibeam transmitter and the multi-detector angle diversity receiver or imaging receiver form a multiple input multiple output (MIMO) system. The work also investigates additional methods that can improve the performance such as transmitter beam angle adaptation, and improved modulation and coding in the form of multi-carrier code division multiple access (MC-CDMA). Furthermore, the work investigates the robustness of a link design that adopts the combination of these methods in a realistic environment with full mobility.

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Boldrini, Leonardo. "Camera Based Localization for Indoor Optical Wireless Networks." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20240/.

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The main focus of this work is to implement device localization in an indoor communication network which employs short range Optical Wireless Communication (OWC) using pencil beams. OWC is becoming increasingly important as a solution to the shortage of available radio spectrum. In order to counter this problem, a radical new approach is proposed by performing wireless communication using optical rather than radio techniques, by deploying optical pencil beam technologies to provide users with access to an indoor optical fiber infrastructure. An architecture based on free-space optics has been adopted. The narrow infrared beam is considered a good solution because of its ability to optimally carry all the information which the optical fiber can transport, in an energy-efficient way. Beam Steered - Infrared Light Communication (BS-ILC) brings the light only where is needed. Multiple beams may independently serve user devices within a room, hence each device can get a non-shared capacity without conflicts with other devices. Infrared light beams, additionally, are allowed to be operated at a higher power than visible light beams, due to a higher eye safety threshold for infrared light. Together with the directivity of a beam, this implies that the received signal-to-noise ratio with BS-ILC can be substantially higher than with Visible Light Communication (VLC), enabling a higher data rate and longer reach at better power efficiency. Current BS-ILC prototypes allow multiple beams with over 100 Gbit/s per beam. This high performance can only be achieved with small footprints, hence the system needs to know the exact location of user devices. In this thesis, an accurate and fast localization/tracking technique using a low-cost camera and simple image processing is presented.

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Liu, Yi. "The performance of future wireless communication systems." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:a2f0b75e-3b0d-406e-af1b-6c5038c18fae.

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Multimedia services provided through wireless networks, such as mobile television and video calls, have recently attracted great attention. These systems require higher data rates, better communication quality, and wider channel bandwidth compared with traditional wireless network services, such as voice calling and text messaging. In response to these demands, multiple-input multiple-output (MIMO) employing multiple antennas at both transmitter and receiver, has been investigated in recent years. Nevertheless, the major impediment in MIMO based wireless systems is the cost of the hardware due to the requirement of the complete radio frequency (RF) chain for each transmit and receive path. One technique named antenna subset selection has been proposed which can reduce the hardware complexity, for example, provide and smaller number of RF chains which are reconfigurable to serve multiple antennas, but retain good communication performance, such as increasing data rates and improving communication quality. On the other hand, network service providers have in recent years established wideband communication systems in order to provide more services and higher bandwidth to customers. However, this development lowers the communication link quality, since signals transmitted in wideband communication systems suffer frequency-selective fading. In order to reduce the fading, orthogonal frequency division multiplexing (OFDM) as a potential infrastructure in the fourth generation mobile communication networks is developed. Referring to the cost-performance ratio, an attractive future wireless system named antenna selection based MIMO-OFDM is considered to be widely utilized in civil wireless communications in near future. The working theory of antenna selection based MIMO-OFDM systems can be simply represented as that a data stream at each selected transmit/receiver antenna is sent/receive over a number of narrow band orthogonal subcarriers. This thesis addresses analysis of wireless channel and performance investigation of future wireless communication systems, such as MIMO and OFDM structures. Moreover, a novel significantly low computational complexity algorithm is introduced in this thesis, which is proposed for antenna selection MIMO-OFDM systems on the basis of multiple selection criteria. It is shown that the proposed selection algorithm clearly reduces the computational complexity load of the selection process and efficiently selects the optimum antenna subset of antenna selection MIMO-OFDM systems. The thesis concludes by outlining the advantage of the proposed antenna selection technique and points out its potential role in future wireless communications.

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Gatri, Aymen [Verfasser]. "Next Generation Optical Wireless Communication Systems : A Systems Approach / Aymen Gatri." Hamburg : disserta Verlag, 2019. http://d-nb.info/1199410845/34.

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Jasman, Faezah. "Modelling and characterisation of short range underwater optical wireless communication channels." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/82113/.

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This thesis studies the modelling and characterisation of underwater optical wireless communication links, particularly short-range diffuse links, by using numerical Monte Carlo (MC) simulation. MC simulation provides a flexible, intuitive and accurate modelling of the underwater channel, which is severely affected by absorption and scattering processes. In diffuse Underwater Optical Wireless Communication (UOWC) links, scattering is expected to have a larger impact on communication link performance due to the wider beam divergence compared to collimated beams. Thus, this thesis will investigate the characterisation of path loss, spatial, temporal and angular dispersions of diffuse links in various types of water. Firstly, a detailed investigation on the path loss performance of diffuse beam in three types of water is presented. This includes the study on the contribution of unscattered and scattered components of light to the total received power and how they are attenuated. From the percentage of unscattered light that contributed to the total power reception, the distance at which the unscattered component drops to zero can be estimated. This distance is used to predict the transition point from minimal scattering to multiple scattering regime for diffuse beams in coastal and turbid water. In addition to this, the spatial dispersion effect is also studied at off-axis locations. To further understand the behaviour of scattering in diffuse links, the scattering order probability is evaluated for various beam sizes in various types of water. Currently, this kind of information cannot be obtained either analytically or experimentally. The information on the scattering order is used as the parameter to classify the links into three scattering regimes, namely minimal, intermediate and multiple scattering regimes. Further investigations into the transition regimes are conducted by investigating the impulse response and frequency response performance for temporal dispersion effects. From the impulse response and frequency response analysis, the bandwidth that can be supported by the channel can be predicted, which provides some insight into the potential and limits of the links. In addition to temporal dispersion, the angular dispersion performance is also evaluated. It is shown through the angle of arrival (AOA) distribution that diffuse beams exhibit significant angular dispersions, implying that a large receiver field of view (FOV) is needed for optimum power performance. The information on the AOA distribution is then used to study the impact of receiver FOV on the bandwidth. Finally, the effect of aperture on the power received and scattering order histogram is evaluated. As a conclusion, the numerical results presented in this thesis will provide an improved understanding of the effect of scattering on path loss, spatial, temporal and angular dispersions along with their relationships with each other.

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Hoang, Thai Bang. "Infrared and visible wireless optical technology for body sensor connectivity." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0027/document.

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Cette thèse est axée sur le domaine de la communication optique sans fil en intérieur pour la surveillance de la santé basée sur des capteurs corporels. L’état de l'art des communications optique sans fil dans les domaines infrarouge, visible et UV ainsi que l'analyse des systèmes liés à la santé utilisant cette technologie ont été fournis. Cela a permis de définir les objectifs et l'orientation de cette thèse. Nous avons étudié l'utilisation de la technologie infrarouge pour la transmission de données entre un capteur porté par un patient et des récepteurs situés aux coins d'un panneau d'éclairage central au plafond de l'environnement. Un lien en visible a été utilisé pour la transmission de données du luminaire vers le patient portant un smartphone équipé d'un décodeur. Les principaux défis étaient la robustesse des liens infrarouge et visible en ce qui concerne la mobilité du patient et l'impact du corps de l'utilisateur en raison de l'emplacement du capteur. Les simulations de canaux réalisées grâce à la technique de Ray-Tracing associée à la méthode de Monte-Carlo ont permis de déterminer le gain de canal qui est le paramètre principal représentant la performance. En raison de la mobilité du patient, l'analyse a été réalisée de manière statistique et en tenant compte de différents emplacements du capteur sur le corps, de la cheville à l'épaule. Les paramètres physiques et géométriques optimaux relatifs aux émetteurs et aux récepteurs afin de garantir les meilleures performances ont été déduites. Il a été démontré qu’il est essentiel de modéliser la présence du corps pour les deux liaisons montante et descendante. Les performances globales du système ont mis en évidence le potentiel des transmissions sans fil entièrement optiques pour la surveillance médicale basée sur des capteurs corporels. Cela a été en partie confirmé par des expérimentations menées à partir de prototypes de capteur communicant en infrarouge et de produits commerciaux pour la liaison en visible
This thesis is focused on the field of indoor optical wireless communication for health monitoring based on body sensors. The state of the art of optical wireless in the infrared, visible and UV domains as well as the analysis of health related systems using this technology have been provided. This helped to define the objectives and orientations of this thesis. We have studied the use of infrared technology for data transmission between a sensor worn by a patient and receivers located at the corners of a central lighting panel at the ceiling of the environment. A link in visible was used for the transmission of data from the luminaire to the patient carrying a smartphone equipped with a decoder. The main challenges were the robustness of the infrared and visible links with regard to patient mobility and the impact of the user's body due to the location of the sensor. The channel simulations performed using the Ray-Tracing technique associated with the Monte-Carlo method allowed determining the channel gain, which is the main parameter representing the performance. Due to the patient mobility, the analysis was performed statistically and taking into account different locations of the sensor on the body, from the ankle to the shoulder. The optimal physical and geometrical parameters for transmitters and receivers to ensure the best performance have been deduced. It has been shown that it is essential to model the presence of the body for both uplink and downlink. The overall performance of the system has highlighted the potential of fully optical wireless transmissions for medical surveillance based on body sensors. This has been partly confirmed by experiments carried out from infrared communicating sensor prototypes and commercial products for the visible link

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Ketprom, Urachada. "Line-of-sight propagation of optical wave through multiple-scatter channel in optical wireless communication system /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6057.

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Agarwal, Rahul. "Low temperature hermetically sealed 3-D MEMS device for wireless optical communication." [Tampa, Fla] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002181.

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Zhang, Qian. "Block error rate of optical wireless communication systems over atmospheric turbulence channels." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44187.

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Optical wireless communication (OWC) is an innovative and promising technology introduced in recent decades, and it can be used for both indoor and outdoor applications. Outdoor OWC is also an attractive solution to the access network bottle-neck. However, challenges can arise for OWC links with increased atmospheric turbulence levels due to time-varing temperatures and pressures, resulting fading or scintillation. This thesis studies and analyzes the block error rate performance of subcarrier intensity modulation based OWC systems employing both noncoherent and coherent binary modulations over various atmospheric turbulence channels. The block error rate is a meaningful performance metric in the slow fading turbulence channels because the fading coefficients are constant over the duration of a block of bits. For the Gamma-Gamma turbulence channels, we obtain highly accurate block error rate expressions in terms of an infinite series for noncoherent binary modulations. With coherent binary phase shift keying, we first propose a new sum of exponentials approximation of the Gaussian Q-function, and then develop the corresponding block error rate expression. For the lognormal turbulence channels, we use the Gauss-Laguerre quadrature method to obtain an accurate estimation of the block error rate.

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Aldibbiat, Nawras Mohamed. "Optical wireless communication systems employing dual header pulse interval modulation (DH-PIM)." Thesis, Sheffield Hallam University, 2001. http://shura.shu.ac.uk/7117/.

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Indoor optical wireless communication systems have been shown to be viable alternatives to radio systems for indoor networks because optical wireless systems offer a huge unlicensed bandwidth, high data rates, secure connectivity, immunity to electromagnetic interference and prevention from multipath fading. However, optical wireless systems are subject to multipath distortion and are governed by eye safety standards. Therefore, a modulation scheme is required that is capable of providing high speed and good immunity to multipath dispersion on indoor optical channels. In this thesis, a critical review of optical wireless systems and suitable modulation schemes has been presented. A new modulation scheme called dual header pulse interval modulation (DH-PTh1) is presented. A comprehensive theoretical analysis supported by computer simulations has been carried out to study characteristics of DH-PTh1. Novel expressions for the DH-PTh1 pulse train, symbol length, bandwidth requirement, packet transmission rate, transmission capacity, Fourier transform, power spectral density, slot and packet error rates and power requirement and penalty due to multipath propagation have been presented. Results from the analyses have been compared with OaK, PPM and DPTh1 modulation schemes. It has been shown that DH-PTh1 is a viable alternative scheme for indoor optical wireless communications, due to its built-in symbol synchronisation and relatively easy slot synchronisation. Compared with PPM and DPIM, DH-PIM offers shorter symbol lengths, improved transmission rates, increased transmission capacity, improved bandwidth requirement and better immunity to multipath dispersion when the dispersion is high. However these features are at the expense of a slightly higher optical power requirement and increased probability of error. The proposed scheme is suitable for applications where there is a need for high throughput.

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Doniec, Marek Wojciech. "Autonomous underwater data muling using wireless optical communication and agile AUV control." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79211.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 187-197).
Underwater exploration and surveillance currently relies on subsea cables and tethers to relay data back to the user. The cause for this is that water heavily absorbs most electromagnetic signals, preventing effective radio communication over large distances, and that underwater communication with acoustic signals affords only bit rates on the the order of Kilobits per second. In this thesis we present a novel design and implementation for an underwater data muling system. This system allows for automatic collection of underwater datasets without the need to physically connect to or move the sensors by using mobile robots to travel to the sensors and download the data using wireless optical communication to bring it back to the base station. The system consists of two parts. The first part is a modular and adaptive robot for underwater locomotion in six degrees of freedom. We present a hardware design as well as control algorithms to allow for in-situ deployment without the need for manual configuration of the parameter space. To achieve this we designed a highly parameterizable controller and methods and algorithms for automatically estimating all parameters of this controller. The second part of the data mulling system is a novel high-bandwidth optical underwater communication device. This device allows for transfer of high-fidelity data, such as high-definition video and audio, images, and sensor logs. Finally we present algorithms to control the robots path in order to maximize data rates as it communicates with a sensor while using only the signal strength as a measurement. All components and algorithms of the system have been implemented and tested in the real world to demonstrate the validity of our claims.
by Marek Wojciech Doniec.
Ph.D.

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He, Jingyi. "Routing and channel assignment in optical and wireless networks /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20HE.

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Jia, Zhensheng. "Optical millimeter-wave signal generation, transmission and processing for symmetric super-broadband optical-wireless access networks." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24640.

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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Gee-Kung Chang; Committee Co-Chair: Jianjun Yu; Committee Member: John A. Buck; Committee Member: Joy Laskar; Committee Member: Umakishore Ramachandran; Committee Member: Ye Li

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Liu, Cheng. "Advanced system design and signal processing techniques for converged high-speed optical and wireless applications." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49058.

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The ever-increasing data traffic demand drives the evolution of telecommunication networks, including the last-mile access networks as well as the long-haul backbone networks. This Ph.D. dissertation focuses on system design and signal processing techniques for next-generation converged optical-wireless access systems and the high-speed long-haul coherent optical communication systems. The convergence of high-speed millimeter-wave wireless communications and high-capacity fiber-optic backhaul networks provides tremendous potential to meet the capacity requirements of future access networks. In this work, a cloud-radio-over-fiber access architecture is proposed. The proposed architecture enables a large-scale small-cell system to be deployed in a cost-effective, power-efficient, and flexible way. Based on the proposed architecture, a multi-service reconfigurable small-cell backhaul network is developed and demonstrated experimentally. Additionally, the combination of high-speed millimeter-wave radio and fiber-optic backhaul is investigated. Several novel methods that enable high-spectral-efficient vector signal transmission in millimeter-wave radio-over-fiber systems are proposed and demonstrated through both theoretical analysis and experimental verification. For long-haul core networks, ultra-high-speed optical communication systems which can support 1Terabit/s per channel transmission will soon be required to meet the increasing capacity demand in the core networks. Grouping a number of tightly spaced optical subcarriers to form a terabit superchannel has been considered as a promising solution to increases channel capacity while minimizing the need for high-level modulation formats and high baud rate. Conventionally, precise spectral control at transmitter side is required to avoid strong inter-channel interference (ICI) at tight channel spacing. In this work, a novel receiver-side approach based on “super receiver” architecture is proposed and demonstrated. By jointly detecting and demodulating multiple channels simultaneously, the penalties associated with the limitations of generating ideal spectra can be mitigated. Several joint DSP algorithms are developed for linear ICI cancellation and joint carrier-phase recovery. Performance analysis under different system configurations is conducted to demonstrate the feasibility and robustness of the proposed joint DSP algorithms, and improved system performance is observed with both experimental and simulation data.

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Rajbhandari, Sujan. "Application of wavelets and artificial neural network for indoor optical wireless communication systems." Thesis, Northumbria University, 2010. http://nrl.northumbria.ac.uk/1933/.

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This study investigates the use of error control code, discrete wavelet transform (DWT) and artificial neural network (ANN) to improve the link performance of an indoor optical wireless communication in a physical channel. The key constraints that barricade the realization of unlimited bandwidth in optical wavelengths are the eye-safety issue, the ambient light interference and the multipath induced intersymbol interference (ISI). Eye-safety limits the maximum average transmitted optical power. The rational solution is to use power efficient modulation techniques. Further reduction in transmitted power can be achieved using error control coding. A mathematical analysis of retransmission scheme is investigated for variable length modulation techniques and verified using computer simulations. Though the retransmission scheme is simple to implement, the shortfall in terms of reduced throughput will limit higher code gain. Due to practical limitation, the block code cannot be applied to the variable length modulation techniques and hence the convolutional code is the only possible option. The upper bound for slot error probability of the convolutional coded dual header pulse interval modulation (DH-PIM) and digital pulse interval modulation (DPIM) schemes are calculated and verified using simulations. The power penalty due to fluorescent light interference (FL I) is very high in indoor optical channel making the optical link practically infeasible. A denoising method based on a DWT to remove the FLI from the received signal is devised. The received signal is first decomposed into different DWT levels; the FLI is then removed from the signal before reconstructing the signal. A significant reduction in the power penalty is observed using DWT. Comparative study of DWT based denoising scheme with that of the high pass filter (HPF) show that DWT not only can match the best performance obtain using a HPF, but also offers a reduced complexity and design simplicity. The high power penalty due to multipath induced ISI makes a diffuse optical link practically infeasible at higher data rates. An ANN based linear and DF architectures are investigated to compensation the ISI. Unlike the unequalized cases, the equalized schemes don‘t show infinite power penalty and a significant performance improvement is observed for all modulation schemes. The comparative studies substantiate that ANN based equalizers match the performance of the traditional equalizers for all channel conditions with a reduced training data sequence. The study of the combined effect of the FLI and ISI shows that DWT-ANN based receiver perform equally well in the present of both interference. Adaptive decoding of error control code can offer flexibility of selecting the best possible encoder in a given environment. A suboptimal 'soft' sliding block convolutional decoder based on the ANN and a 1/2 rate convolutional code with a constraint length is investigated. Results show that the ANN decoder can match the performance of optimal Viterbi decoder for hard decision decoding but with slightly inferior performance compared to soft decision decoding. This provides a foundation for further investigation of the ANN decoder for convolutional code with higher constraint length values. Finally, the proposed DWT-ANN receiver is practically realized in digital signal processing (DSP) board. The output from the DSP board is compared with the computer simulations and found that the difference is marginal. However, the difference in results doesn‘t affect the overall error probability and identical error probability is obtained for DSP output and computer simulations.

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Dey, Sanjoy Namuduri Kameswara. "Performance analysis of CCR based distributed sensor network based on optical wireless communication." A link to full text of this thesis in SOAR, 2008. http://hdl.handle.net/10057/2007.

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Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical and Computer Engineering.
Copyright 2008 by Sanjoy Dey. All Rights Reserved. Includes bibliographical references (leaves 16-18).

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Hagem, Rabee Mouffage. "Real Time Evaluation of Swimmers Performance Based on an Optical Wireless Communication System." Thesis, Griffith University, 2014. http://hdl.handle.net/10072/365345.

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Athlete monitoring using movement sensors can provide important information for coaches and trainers. The main aim of this thesis is to design, implement and test an optical wireless communication link for swimming applications to give real time feedback to the swimmer so that adjustments can be made during swimming. As swimmers are located relatively close to the surface of the water, arm and leg movement can generate a significant number of air bubbles. Total internal reflection from the surface and attenuation due to bubbles is a major problem for communications both below and above the water. For the system the design challenges included: communication type, optical transmitter, bubbles effect, optical receiver, link budget and electronics requirements and optical wavelength. The solution was optical wireless communications in the green spectrum using frequency shift keying (FSK) and on-off keying (OOK). The effect of strong background light was solved using an optical filter on the receiver. This thesis describes a new system to provide a swimmer with real time feedback to adjust stroke rate during swimming. A wrist-mounted accelerometer with a communications link to a receiver located on the goggles allows visual signals to be given to the athlete. As the maximum distance between a swimmer’s wrist and goggles is approximately 1m the communications system must achieve this distance or more. The range varies because of the movement of the swimmer’s arms and head.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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37

Li, Yichen. "Enhancing communication link performance in visible light communication." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/25666.

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With data throughput increasing exponentially in wireless communication networks, the limited radio frequency (RF) spectrum is unable to meet the future data rate demand. As a promising complementary approach, optical wireless communication (OWC) has gained significant attention since its licence-free light spectrum provides a considerable amount of communication bandwidth. In conventional OWC systems, the information-carried signal has to be real-valued and non-negative due to the incoherent light output of the conventional optical transmitter, light emitting diode (LED). Therefore, an intensity modulation and direct detection (IM/DD) system is used for establishing the OWC link. Some modified orthogonal frequency division multiplexing (OFDM) schemes have been proposed to achieve suitable optical signals. In previous research, three OFDM-based schemes have been presented, including DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM), asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) and unipolar orthogonal frequency division multiplexing (U-OFDM). Basic concepts of SPAD receivers are studied and a novel application in OWC is proposed for a permanent downhole monitoring (PDM) system in the gas and oil industry. In this thesis, a complete model of the SPAD-based OWC system is presented, including some related SPAD metrics, the photon counting process in SPAD and a specific nonlinear distortion caused by passive quenching (PQ) and active quenching (AQ) recharged circuits. Moreover, a practical SPAD-based visible light communication (VLC) system and its theoretical analysis are presented in a long-distance gas pipe with a battery-powered LED and a basic on-off keying (OOK) modulation scheme. In this thesis, two novel optical orthogonal frequency division multiplexing (O-OFDM) technologies are proposed: non-DC-biased orthogonal frequency division multiplexing (NDCOFDM) and OFDM with single-photon avalanche diode (SPAD). The former is designed for optical multiple-input multiple-output (O-MIMO) systems based on the optical spatial modulation (OSM) technique. In NDC-OFDM, signs of modulated O-OFDM symbols and absolute values of the symbols are separately transmitted by different information carrying units. This scheme can eliminate clipping distortion in DCO-OFDM and achieve high power efficiency. Furthermore, as the indices of transmitters carry extra information bits, NDC-OFDM gives a significant improvement in spectral efficiency over ACO-OFDM and U-OFDM. In this thesis, SPAD-based OFDM systems with DCO-OFDM and ACO-OFDM are presented and analysed by considering the nonlinear distortion effect of PQ SPAD and AQ SPAD. A comprehensive digital signal processing of SPAD-based OFDM is shown and theoretical functions of the photon counting distribution in PQ SPAD and AQ SPAD are given. Moreover, based on Bussgang theorem, a conventional method for analysing memoryless distortion, close-formed bit-error rate (BER) expressions of SPAD-based OFDM are derived. Furthermore, SPAD-based OFDM is compared with conventional photo-diode (PD) based OFDM systems, and a gain of 40 dB in power efficiency is observed.

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Dimitrov, Svilen Dimitrov. "Analysis of OFDM-based intensity modulation techniques for optical wireless communications." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7833.

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Optical wireless communication (OWC) is a promising alternative to radio frequency (RF) communication with a significantly larger and unregulated spectrum. Impairments in the physical layer, such as the non-linear transfer characteristic of the transmitter, the dispersive optical wireless channel and the additive white Gaussian noise (AWGN) at the receiver, reduce the capacity of the OWC system. Single-carrier multi-level pulse position modulation (M-PPM) and multilevel pulse amplitude modulation (M-PAM) suffer from inter-symbol interference (ISI) in the dispersive channel which reduces their capacity even after channel equalization. Multi-carrier modulation such as optical orthogonal frequency division multiplexing (O-OFDM) with multilevel quadrature amplitude modulation (M-QAM) is known to maximize the channel capacity through bit and power loading. There are two general signal structures: bipolar Gaussian signal with a direct current (DC) bias, i.e. DC-biased O-OFDM (DCO-OFDM), or unipolar half- Gaussian signal, employing only the odd subcarriers, i.e. asymmetrically clipped O-OFDM (ACO-OFDM). In this thesis, the signal distortion from the transmitter nonlinearity is minimized through pre-distortion, optimum signal scaling and DC-biasing. The optical front-ends impose minimum, average and maximum optical power constraints, as well as an average electrical power constraint, on the information-carrying signals. In this thesis, the optical signals are conditioned within these constraints through optimum signal scaling and DC-biasing. The presented analysis of the optical-to-electrical (O/E) conversion enables the derivation of the electrical signal-to-noise ratio (SNR) at the receiver, including or excluding the additional DC bias power, which is translated into bit-error rate (BER) performance. In addition, a generalized piecewise polynomial model for the non-linear transfer characteristic of the transmitter is proposed. The non-linear distortion in O-OFDM is translated by means of the Bussgang theorem and the central limit theorem (CLT) into attenuation of the data-carrying subcarriers at the receiver plus zero-mean complex-valued Gaussian noise. The attenuation factor and the variance of the non-linear distortion noise are derived in closed form, and they are accounted towards the received electrical SNR. Through pre-distortion with the inverse of the proposed piecewise polynomial function, the linear dynamic range of the transmitter is maximized, reducing the non-linear distortion to double-sided signal clipping. Finally, the OWC schemes are compared in terms of spectral efficiency and electrical SNR requirement as the signal bandwidth exceeds the coherence bandwidth of the optical wireless channel for a practical 10 dB linear dynamic range. Through optimum signal scaling and DCbiasing, DCO-OFDM is found to achieve the highest spectral efficiency for a target SNR, neglecting the additional DC bias power. When the DC bias power is counted towards the signal power, DCO-OFDM outperforms PAM with linear equalization, approaching the performance of the more computationally intensive PAM with non-linear equalization. In addition, the average optical power in O-OFDM is varied over dynamic ranges of 10 dB, 20 dB and 30 dB. When the additional DC bias power is neglected, DCO-OFDM is shown to achieve the Shannon capacity, while ACO-OFDM exhibits a 3 dB gap which grows with higher SNR targets. When the DC bias power is included, DCO-OFDM outperforms ACO-OFDM for the majority of average optical power levels with the increase of the SNR target or the dynamic range.

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39

Isautier, Pierre Paul Roger. "Autonomous receivers for next-generation of high-speed optical communication networks." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54418.

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Advances in fiber optic communications and the convergence of the optical-wireless network will dramatically increase the network heterogeneity and complexity. The goal of our research is to create smart receivers that can autonomously identify and demodulate, without prior knowledge, nearly any signal emerging from the next-generation of high-speed optical communication networks.

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40

Malekizandi, Mohammadreza [Verfasser], Franko [Akademischer Betreuer] Küppers, and Manfred [Akademischer Betreuer] Berroth. "Generation and Transmission of Optical Ultra-wideband Signals for Optical Fiber and Wireless Communication Links / Mohammadreza Malekizandi ; Franko Küppers, Manfred Berroth." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2018. http://d-nb.info/116301351X/34.

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41

Chen, Cheng. "Simultaneous transmission of baseband signal and in band RF signal." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708805.

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42

Ahmed, Maha Shihab. "Improving energy efficiency and quality of service in an integrated wireless-optical broadband access network." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2015. https://ro.ecu.edu.au/theses/1737.

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Exponential growth in the volume of wireless data, boosted by the growing popularity of mobile devices such as smart phones and tablets, is forcing telecommunication industries to rethink network design, and focus on developing high capacity mobile broadband networks. Accordingly, researchers have undertaken developmental work for an integrated wireless-optical broadband access network (WOBAN). Passive optical networks (PONs) and fourth generation (4G) wireless networks are two major candidate technologies for the WOBAN. PON is a wired access technology, well-known for its high capacity, whereas 4G is a wireless broadband access technology, popular for its ease of deployment and ability to offer mobility. Integration of PON and 4G technologies, as a wireless-optical broadband access network, offers advantages such as extension of networks in rural areas, support for mobile broadband services, and rapid deployment of broadband networks. However, these two technologies have different design architectures for handling broadband services which require Quality of Service (QoS), for example, 4G networks use traffic classification for supporting different QoS demands whereas PON does not differentiate between traffic types. This integrated network must also be energy efficient, as a green broadband access network, without hindering QoS. While these technologies both use sleep mode, they differ in their power saving mechanisms. This thesis first addresses a QoS solution for the incompatibility between these technologies. Service class mapping is proposed in Chapter 3 for the integrated WOBAN, based on the M/G/1 queuing model supported by an innovative priority scheduler. Once class mapping is deployed, a power saving mechanism can be devised by exploiting traffic differentiation. Specifically, a class-based strategy is proposed which helps optimise the sleep period for the terminal units of the optical network, without compromising QoS. Since the optical network involves control and terminal nodes, both of which consume power, this thesis proposes an energy efficient mechanism that involves both components. In contrast, other published strategies (Chapter 2) have only considered the terminal units. Chapter 4 presents the mechanism for enabling global sleep (control and terminal nodes) and local sleep (terminal nodes), based on the available traffic's class structure. This mechanism enables sleep for different components within the bandwidth allocation by adapting the switching between predefined polling cycle lengths. As the WOBAN is comprised of both wireless and optical parts, a dynamic resource management mechanism is needed which responds to changing daily traffic patterns across a green integrated network. Consequently, Chapter 5 proposes a mechanism which dynamically adapts the polling cycles, of the optical and wireless parts of the network, to the changing traffic volume and class composition. Tailored sleep durations for the components of the WOBAN are facilitated within the resource management regime, as these components differ in their ability to function efficiently if management of the sleep periods is not responsive to the changing traffic volumes and class composition. This dissertation creates new knowledge by seamlessly integrating the two parts of WOBAN and introducing differentiated, class-based sleep for the components of the hybrid network to help realise a green WOBAN.

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43

Li, Jia, and 李佳. "Photonic microwave processor based on fiber optical parametric amplifier." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43085374.

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Li, Jia. "Photonic microwave processor based on fiber optical parametric amplifier." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43085374.

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45

Gonzalez, Diaz Glenda Zafir. "Energy saving solutions for integrated optical-wireless access networks." Thesis, Evry, Institut national des télécommunications, 2015. http://www.theses.fr/2015TELE0017/document.

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L'explosion de demande de bande passante est une conséquence de l'augmentation du volume de trafic. Il est important de proposer des mécanismes pour transférer le trafic entre les réseaux interconnectés de manière efficace. D'autre part, il est prévu que les réseaux d'accès (optiques et mobiles) constituent les plus grands consommateurs d'énergie dans les réseaux optiques pour les dix prochaines années. Cette situation et l'impact croissant des réseaux sur l'environnement ont fait devenir l'efficacité énergétique dans les réseaux de télécommunications un thème important de recherche. Cette thèse se concentre donc sur la proposition de nouvelles solutions aux problèmes liées à l'augmentation du volume de trafic dans différentes segments des réseaux. Tout d'abord, nous avons étudié différents schèmes de transfert du trafic entre les réseaux interconnectes en utilisant la synchronisation. Puis, nous avons exploré la possibilité d'offrir différents services dans les réseaux intégrés optiques-mobiles. Nous avons présenté une nouvelle architecture pour la conception de l'unité de réseau optique (ONU). Ensuite, nous nous sommes focalisés sur l'économie de l'énergie et des solutions efficaces pour l'allocation de bande passante ont été proposées. Nous avons également proposé un algorithme qui fournit l'efficacité énergétique pour les récepteurs sans fil dans les ONUs hybride. Une analyse des performances en utilisant modèles de files d'attente a été présentée. Finalement, nous avons analysé le trafic hétérogène dans l'ONU hybride, et nous avons proposé un cadre pour un algorithme d'ordonnancement qui puisse mettre à jour les règles de service de façon dynamique
A big growth in the number of subscribers is increasing the traffic volume passing through each sector in a telecommunication network. Mechanisms are required to solve the traffic shift problem between two sectors of the network in an efficient way. Additionally, it is expected that the access networks (optical and wireless) will constitute the largest energy consumers among the networks for the next ten years. This situation and the increasing impact of networks on the environment have made become the energy efficiency in telecommunication networks an important theme for researches. This dissertation hence focuses on the proposition of novel solutions for deal with the problems due to the growing of traffic in different segments of the network. Firstly, we have studied the traffic shift between interconnected networks by using the synchronization as technique to solve this problem. Secondly, we have explored the possibility of provisioning different services over the integration of optical-wireless technologies, which has been considered as a promising candidate for the deployment of high-speed access networks. Architecture of design for the Optical Network Unit (ONU) is presented. Then, energy efficiency has been focused and effective bandwidth management solutions have been proposed. We have also proposed an energy efficiency algorithm for wireless receiver at hybrid ONUS. A performance analysis by queuing models was presented for the implementation of proposed solutions. Finally, we have analyzed the heterogeneous traffic at hybrid ONU, and we have proposed a framework for a scheduling algorithm considering the characteristics of different traffic sources

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Umrani, Fahim Aziz. "Applications of perfect difference codes in fiber-optics and wireless optical code-division multiplexing/multiple-access systems." Thesis, University of South Wales, 2009. https://pure.southwales.ac.uk/en/studentthesis/applications-of-perfect-difference-codes-in-fiberoptics-and-wireless-optical-codedivision-multiplexingmultipleaccess-systems(4025609f-d2a6-4c46-9578-784403202887).html.

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After establishing itself in the radio domain, Spread spectrum code-division multiplexing/multiple-access (CDMA) has seen a recent upsurge in optical domain as well. Due to its fairness, flexibility, service differentiation and increased inherent security, CDMA is proved to be more suitable for the bursty nature of local area networks than synchronous multiplexing techniques like Frequency/Wavelength Division Multiplexing (F/WDM) and Time Division Multiplexing (TDM). In optical domain, CDMA techniques are commonly known as Optical-CDMA (O-CDMA). All optical CDMA systems are plagued with the problem of multiple-access interference (MAI). Spectral amplitude coding (SAC) is one of the techniques used in the literature to deal with the problem of MAI. The choice of spreading code in any CDMA system is another way to ensure the successful recovery of data at the receiving end by minimizing the effect of MAI and it also dictates the hardware design of the encoder and decoder. This thesis focuses on the efficient design of encoding and decoding hardware. Perfect difference codes (PDC) are chosen as spreading sequences due to their good correlation properties. In most of the literature, evaluation of error probability is based on the assumptions of ideal conditions. Such assumptions ignore major physical impairments such as power splitting losses at the multiplexers of transmitters and receivers, and gain losses at the receivers, which may in practice be an overestimate or underestimate of the actual probability of error. This thesis aims to investigate thoroughly with the consideration of practical impairments the applications of PDCs and other spreading sequences in optical communications systems based on spectral-amplitude coding and utilizing codedivision as multiplexing/multiple-access technique. This work begins with a xix general review of optical CDMA systems. An open-ended practical approach has been used to evaluate the actual error probabilities of OCDM/A systems under study. It has been concluded from results that mismatches in the gains of photodetectors, namely avalanche photodiode (APDs), used at the receiver side and uniformity loss in the optical splitters results in the inaccurate calculation of threshold level used to detect the data and can seriously degrade the system bit error rate (BER) performance. This variation in the threshold level can be compensated by employing techniques which maintain a constant interference level so that the decoding architecture does not have to estimate MAI every time to make a data bit decision or by the use of balanced sequences. In this thesis, as a solution to the above problem, a novel encoding and decoding architecture is presented for perfect difference codes based on common zero code technique which maintains a constant interference level at all instants in CDM system and thus relieves the need of estimating interference. The proposed architecture only uses single multiplexer at the transmitters for all users in the system and a simple correlation based receiver for each user. The proposed configuration not only preserves the ability of MAI in Spectral-Amplitude Coding SAC-OCDM system, but also results in a low cost system with reduced complexity. The results show that by using PDCs in such system, the influence of MAI caused by other users can be reduced, and the number of active users can be increased significantly. Also a family of novel spreading sequences are constructed called Manchestercoded Modified Legendre codes (MCMLCs) suitable for SAC based OCDM systems. MCMLCs are designed to be used for both single-rate and Multirate systems. First the construction of MCMLCs is presented and then the bit error rate performance is analyzed. Finally the proposed encoding/decoding architecture utilizing perfect difference codes is applied in wireless infrared environment and the performance is found to be superior to other codes.

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Neo, Soo Sim Daniel. "Free space optics communication for mobile military platforms." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Dec%5FNeo.pdf.

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Ozer, Yucel Cengiz. "Determination Of The Most Suitable Wavelength Intervals For Optical Data Transmission Through The Atmosphere." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607683/index.pdf.

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Optical Wireless Communication systems use lasers offering larger bandwidth, which facilitates higher data rates, comparing with radio communication systems. However, its performance is limited by atmospheric conditions, and is a function of wavelength. The objective of this study is the determination of the wavelength interval(s) at which the atmospheric transmittance is relatively high and has relatively low dependence on variations in temperature, relative humidity, wind speed and atmospheric pressure under the conditions such as path altitude of 10 meters, path geometry of horizontal to the Earth&rsquo
s surface and clean (includes no fog, rain or snow etc.) over sea surface atmosphere. The path length is taken to be 15 km. Alanya was assignated as geographical region and the required information about the atmospheric constituents and meteorological parameters was collected. Then, the variations in atmospheric transmittance due to the periodically measured meteorological parameters were calculated (for summer and winter seasons). Finally, individually calculated effects of these parameters on atmospheric transmittance are assembled in order to determine the desired wavelength interval(s). As a result, the most suitable wavelength interval was determined to be about between 3.99 µ
m and 4.02 µ
m. In addition, dependencies of atmospheric pressure, temperature, relative humidity, and wind speed on atmospheric transmittance have been established for both winter and summer seasons. Atmospheric transmittance is found to be inversely proportional to temperature, relative humidity and wind speed. The effect of pressure is relatively small comparing with other parameters.

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49

Chaudhry, Saqib Rasool. "Application priority framework for fixed mobile converged communication networks." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/7468.

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Abstract:

The current prospects in wired and wireless access networks, it is becoming increasingly important to address potential convergence in order to offer integrated broadband services. These systems will need to offer higher data transmission capacities and long battery life, which is the catalyst for an everincreasing variety of air interface technologies targeting local area to wide area connectivity. Current integrated industrial networks do not offer application aware context delivery and enhanced services for optimised networks. Application aware services provide value-added functionality to business applications by capturing, integrating, and consolidating intelligence about users and their endpoint devices from various points in the network. This thesis mainly intends to resolve the issues related to ubiquitous application aware service, fair allocation of radio access, reduced energy consumption and improved capacity. A technique that measures and evaluates the data rate demand to reduce application response time and queuing delay for multi radio interfaces is proposed. The technique overcomes the challenges of network integration, requiring no user intervention, saving battery life and selecting the radio access connection for the application requested by the end user. This study is split in two parts. The first contribution identifies some constraints of the services towards the application layer in terms of e.g. data rate and signal strength. The objectives are achieved by application controlled handover (ACH) mechanism in order to maintain acceptable data rate for real-time application services. It also looks into the impact of the radio link on the application and identifies elements and parameters like wireless link quality and handover that will influence the application type. It also identifies some enhanced traditional mechanisms such as distance controlled multihop and mesh topology required in order to support energy efficient multimedia applications. The second contribution unfolds an intelligent application priority assignment mechanism (IAPAM) for medical applications using wireless sensor networks. IAPAM proposes and evaluates a technique based on prioritising multiple virtual queues for the critical nature of medical data to improve instant transmission. Various mobility patterns (directed, controlled and random waypoint) has been investigated and compared by simulating IAPAM enabled mobile BWSN. The following topics have been studied, modelled, simulated and discussed in this thesis: 1. Application Controlled Handover (ACH) for multi radios over fibre 2. Power Controlled Scheme for mesh multi radios over fibre using ACH 3. IAPAM for Biomedical Wireless Sensor Networks (BWSN) and impact of mobility over IAPAM enabled BWSN. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in multi radios over fibre performance in terms of application response delay and power consumption by upto 75% and 15 % respectively, reduction in traffic loss by upto 53% and reduction in delay for real time application by more than 25% in some cases.

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50

Lee, Peng Joo. "Alternative high speed network access for the last mile /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Dec%5FLee%5FPeng.pdf.

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Dissertations / Theses on the topic 'Optical wireless communication (OWC)'

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