Simulation, performance and interference analysis of multi-user visible light communication systems

The emergence of new physical media such as optical wireless, and the ability to aggregate these new media with legacy networks motivate the study of heterogeneous network performance, especially with respect to the design of protocols to best exploit the characteristics of each medium. This study considers Visible Light Communications (VLC), which is expected to coexist with legacy and future radio frequency (RF) media. While most of the research on VLC has been done on optimizing the physical medium, research on higher network layers is only beginning to gain attention, requiring new analyses and tools for performance analysis. The first part of the dissertation concerns with developing a new ns3-based VLC module that can be used to study VLC-RF heterogeneous networks via simulation. The proposed ns3 module is developed based on existing models for intensity modulated LED signals operating as lighting units transmitting to optical receivers at indoor scales (meters). These models and the corresponding simulation model are validated using a testbed implemented with a software-defined radio (SDR) system, photodetector, phosphor-converted “white” LEDs, and under PSK and QAM modulation. Two scenarios are used in the validation of the VLC module: (i) using a receiver placed right bellow the transmitter with varying range, and (ii) using a receiver with a fixed range and varying angle of acceptance. Results indicate good correspondence between the simulated and actual testbed performance. Subsequently, it demonstrates how the VLC module can be used to predict the performance of a hybrid WiFi/VLC network simulated using the ns3 environment with UDP, TCP, and combined network traffic. The second part of the dissertation focuses on modeling interference at VLC system level based on variable pulse position modulation (VPPM) and variable on-off keying (VOOK) which are used in VLC to simultaneously provide lighting with dimming control as well as communication. The bit error performance of these modulation schemes is evaluated at VLC systems consisting of multiple transmitters-receivers pairs, where co-channels interference exists. The BER is derived by providing an in depth analysis that captures the signal structure of the interference in terms of the number of transmitters. This work dispenses with the Gaussian interference model which is not suitable when the number of interferers are few and the central limit theorem (CLT) cannot be applied. The result shows that under realistic small-room scenario, the analytical results closely match with that of simulation

CamComSim: un simulateur de communication LED vers camera

In this paper, we present CamComSim, the first simulator for development and rapidprototyping of LED-to-Camera communication systems. Our event driven simulator relies on astandalone Java application that is easily extensible through a set of interfaces. A range of lowand high-level parameters, such as the camera characteristics, the physical layer data unit size, orthe redundancy mechanism can be chosen. CamComSim uses empirically validated models for theLED-to-Camera channel and the broadcast protocols, configurable with a finely grained precision.To validate CamComSim implementation and accuracy, we use a real life testbed based on a colorLED and a smartphone and compare the performance reached by the testbed with the resultsgiven by our simulator. We illustrate with a real use case the full usage of CamComSim, tuninga broadcast protocol that implements the transmission of 1 kbyte of information. The resultshighlight that our simulator is very precise and predicts the performance of a real LED-to-Camerasystem with less than 10% of error in most cases.Dans cet article, nous présentons CamComSim, le premier simulateur de systèmesde communication par lumière visible d’une LED vers une caméra. Notre simulateur repose surune application Java autonome qui est facilement extensible grâce un ensemble d’interfaces. Denombreux paramètres bas et haut niveau, tels que les caractéristiques de la caméra, la taille destrames PHY ou le mécanisme de redondance utilisé peuvent être choisis. CamComSim utilise desmodèles de canal et de protocole de broadcast validés empiriquement, et finement configurable.Pour valider l’implémentation et la précision de CamComSim, nous utilisons un banc de testbasé sur une LED couleur et un smartphone et comparons les performances obtenues par le bancde test avec les résultats fournis par notre simulateur. Nous illustrons avec un cas d’utilisationréel l’utilisation de CamComSim, en ajustant les paramètres d’un protocole de broadcast lors dela transmission de 1 Ko d’information. Les résultats mettent en évidence que notre simulateurest très précis et prédit les performances d’un vrai système LED vers caméra avec moins de 10

A critical analysis of research potential, challenges and future directives in industrial wireless sensor networks

In recent years, Industrial Wireless Sensor Networks (IWSNs) have emerged as an important research theme with applications spanning a wide range of industries including automation, monitoring, process control, feedback systems and automotive. Wide scope of IWSNs applications ranging from small production units, large oil and gas industries to nuclear fission control, enables a fast-paced research in this field. Though IWSNs offer advantages of low cost, flexibility, scalability, self-healing, easy deployment and reformation, yet they pose certain limitations on available potential and introduce challenges on multiple fronts due to their susceptibility to highly complex and uncertain industrial environments. In this paper a detailed discussion on design objectives, challenges and solutions, for IWSNs, are presented. A careful evaluation of industrial systems, deadlines and possible hazards in industrial atmosphere are discussed. The paper also presents a thorough review of the existing standards and industrial protocols and gives a critical evaluation of potential of these standards and protocols along with a detailed discussion on available hardware platforms, specific industrial energy harvesting techniques and their capabilities. The paper lists main service providers for IWSNs solutions and gives insight of future trends and research gaps in the field of IWSNs

Suporte a gerenciamento do trânsito baseado em computação na névoa para os sistemas de transporte inteligentes

Orientadores: Leandro Aparecido Villas, Daniel Ludovico GuidoniTese (doutorado) ¿ Universidade Estadual de Campinas, Instituto de ComputaçãoResumo: O trânsito nos grandes centros urbanos contribui com problemas que vão desde diminuição da qualidade de vida e segurança da população até o aumento de custos financeiros às pessoas, cidades e empresas. Um dos motivos para um maior tráfego de veículos é o vertiginoso crescimento populacional dos centros urbanos. Além disso, o fluxo de veículos é prejudicado por situações adversas recorrentes nas vias, como o aumento súbito do tráfego durante os horários de pico, gargalos nas infraestruturas de transporte, e acidentes de trânsito. Com o avanço das tecnologias de comunicação, processamento e sensoriamento, os Sistemas de Transporte Inteligentes (ITS) surgem como uma alternativa para mitigar esses problemas. A interoperabilidade dos ITS com novas tecnologias tais como as redes veiculares (VANETs) e computação em névoa, os tornam mais promissores e eficazes. As VANETs preveem que veículos possuam poder computacional e capacidade de comunicação sem fio com outros veículos e com as infraestruturas fixa de comunicação, assim, uma nova gama de serviços de segurança e entretenimento aos motoristas e passageiros podem ser desenvolvidas. Entretanto, estes tipos de serviços, em especial o de gerenciamento de trânsito, demandam uma análise contínua das condições de fluxo de veículos nas vias e um vasto recurso de rede e processamento, tornando o desenvolvimento de soluções para ITS mais complexo e de difícil escalabilidade. A computação em névoa é uma infraestrutura de computação descentralizada na qual dados, processamento, armazenamento e aplicações são distribuídos na borda da rede, assim, aumentando a escalabilidade do sistema. Na literatura, os sistemas de gerenciamento de tráfego não tratam de maneira adequada o problema de escalabilidade, implicando em problemas relacionados ao balanceamento de carga e tempo de resposta. Esta tese de doutorado propõe um sistema de gerenciamento de tráfego baseado no paradigma de computação em névoa, para detectar, classificar e controlar o congestionamento de tráfego. O sistema proposto apresenta um framework distribuído e escalável que reduz os problemas supracitados em relação ao estado da arte. Para tanto, utilizando da natureza distribuída da computação em névoa, a solução implementa um algoritmo de roteamento probabilístico que faz o balanceamento do tráfego e evita o problema de deslocamento de congestionamentos para outras regiões. Utilizando às características da computação em névoa, foi desenvolvida uma metodologia distribuída baseada em regiões que faz a coleta de dados e classificação das vias em relação às condições do trânsito compartilhadas pelos veículos. Finalmente, foi desenvolvido um conjunto de algoritmos/protocolos de comunicação que comparado com outras soluções da literatura, reduz a perda de pacotes e o número de mensagens transmitidas. O serviço proposto foi comparado extensivamente com outras soluções da literatura em relação às métricas de trânsito, onde o sistema proposto foi capaz de reduzir em até 70% o tempo parado e em até 49% o planning time index. Considerando as métricas de comunicação, o serviço proposto é capaz de reduzir em até 12% a colisão de pacotes alcançando uma cobertura de 98% do cenário. Os resultados mostram que o framework baseado em computação em névoa desenvolvido, melhora o fluxo de veículos de forma eficiente e escalávelAbstract: Traffic in large urban centers contributes to problems that range from decreasing the population¿s quality of life and security to increasing financial costs for people, cities, and companies. One of the reasons for increased vehicle traffic is the population growth in urban centers. Moreover, vehicle flow is hampered by recurring adverse situations on roads, such as the sudden increase in vehicle traffic during peak hours, bottlenecks in transportation infrastructure, and traffic accidents. Considering the advance of communication, processing, and sensing technologies, Intelligent Transport Systems (ITS) have emerged as an alternative to mitigate these problems. The interoperability of ITS with new technologies, such as vehicular networks (VANETs) and Fog computing, make them more promising and effective. VANETs ensure that vehicles have the computing power and wireless communication capabilities with other vehicles and with fixed communication infrastructures; therefore, a new range of security and entertainment services for drivers and passengers can be developed. However, these types of services, especially traffic management, demand a continuous analysis of vehicle flow conditions on roads and a huge network and processing resource, making the development of ITS solutions more complex and difficult to scale. Fog computing is a decentralized computing infrastructure in which data, processing, storage, and applications are distributed at the network edge, thereby increasing the system¿s scalability. In the literature, traffic management systems do not adequately address the scalability problem, resulting in load balancing and response time problems. This doctoral thesis proposes a traffic management system based on the Fog computing paradigm to detect, classify, and control traffic congestion. The proposed system presents a distributed and scalable framework that reduces the aforementioned problems in relation to state of the art. Therefore, using Fog computing¿s distributed nature, the solution implements a probabilistic routing algorithm that balances traffic and avoids the problem of congestion displacement to other regions. Using the characteristics of Fog computing, a distributed methodology was developed based on regions that collect data and classify the roads concerning the traffic conditions shared by the vehicles. Finally, a set of communication algorithms/protocols was developed which, compared with other literature solutions, reduces packet loss and the number of messages transmitted. The proposed service was compared extensively with other solutions in the literature regarding traffic metrics, where the proposed system was able to reduce downtime by up to 70% and up to 49% of the planning time index. Considering communication metrics, the proposed service can reduce packet collision by up to 12% reaching 98% coverage of the scenario. The results show that the framework based on Fog computing developed improves the vehicles¿ flow efficiently and in a scalable wayDoutoradoCiência da ComputaçãoDoutor em Ciência da Computaçã

Medium access control protocol for visible light communication in vehicular communication networks

Recent achievements in the automotive industry related to lighting apparatuses include the use of LED or laser technology to illuminate the vehicle environment. This advancement resulted in greater energy efficiency and increased safety with selective illumination segments. A secondary effect was creating a new field for researchers in which they can utilize LED fast modulation using the Pulse Width Modulation (PWM) signal. Using LED to encode and transmit data is a relatively new and innovative concept. On the other field, there have been advancements in vehicular communication using radio frequency at 2.4 or 5GHz. This research focuses mainly on a field in which visible light augments or replaces radio frequency communication between vehicles. This research also investigates the effect of asymmetry on network performance using Visible Light Communication (VLC) in vehicular networks. Different types of asymmetry were defined and tested in real-world simulation experiments. Research results showed that asymmetry has a negative influence on network performance, though that effect is not significant. The main focus of the research is to develop a lightweight and new Media Access Control (MAC) protocol for VLC in vehicular networks. To develop a MAC protocol for VLC, special software was developed on top of the existing Network Simulation Environment (NSE). A new VLC MAC protocol for Vehicle to Vehicle (V2V) was benchmarked using a defined set of metrics. The benchmark was conducted as a set of designed simulation experiments against the referent IEEE 802.11b MAC protocol. Both protocols used a newly defined VLC-equipped vehicle model. Each simulation experiment depicted a specific network and traffic situation. The total number of scenarios was eleven. The last set of simulations was conducted in realworld scenarios on the virtual streets of Suffolk, VA, USA. Using defined metrics, the test showed that the new VLC MAC protocol for V2V is better than the referent protocol.Nedavna dostignuća u automobilskoj industriji koja se tiču opreme za osvjetljivanje uključuju korištenje LED ili laserskih rasvjetnih tijela za osvjetljivanje okoline. Ovime se postižu uštede u potrošnji energije kao i povećana sigurnost u prometu. LED rasvjeta je uniformnija od običnih žarulja tako da osvjetljenje bude ravnomjernije i preciznije. Obzirom da su LED selektivne moguće je odabrati segment ceste koji se želi osvijetliti. Upravo ta fleksibilnost LED otvara novi prostor za istraživače gdje mogu koristiti PWM signal za modulaciju podataka. PWM je poseban signal koji ima varijabilnu širinu pulsa na izlazu. Istraživači i znanstvenici mogu koristiti LED za kodiranje i prijenos podataka između automobila. Prednosti korištenja komunikacije u vidljivom dijelu elektro-magnetskog spektra (eng.VLC) je u činjenici da taj segment nije zaštićen licencama te je otvoren za slobodno korištenje. Osim toga, vidljivo, neintenzivno svjetlo nema biološki negativnih posljedica. Kod korištenja PWM signala za modulaciju, postojeći izlaz svjetla i njegova funkcija (osvjetljivanja ceste) nisu narušeni. Ljudsko oko ne može detektirati oscilacije tako visoke frekvencije (oko 5 kHz) S druge strane, komponente koje mogu primiti poslani signal su foto diode ili kamere. Kamere su već prisutne na modernom vozilu u obliku prednje kamere ili stražnje kamere za pomoć pri parkiranju. U svakom slučaju, tehnologija je već prisutna na modernom vozilu. Na drugom području, znanstvenici rade na komunikaciji između vozila koristeći radio valove niže frekvencije 2.4 ili 5 GHz. Komunikacija između automobila je predmet standardizacije i mnoge zemlje već propisuju pravila za obaveznu ugradnju opreme za takav oblik komunikacije. Prednost takvog koncepta je razmjena podatka; od onih za zabavu pa do kritičnih i sigurnosnih podataka npr. informacija o nadolazećem mjestu gdje se dogodila prometna nesreća. Ovo istraživanje se fokusira na proširenje ili zamjenu radio komunikacije sa komunikacijom koristeći vidljivi dio spektra (npr. LED i kamere). Jedan od glavnih nedostataka takvog koncepta je ne postojanje adekvatnog i specijaliziranog protokola za kontrolu pristupa mediju (eng. MAC). Drugi problem je nepoznati efekt asimetrije u VLC komunikaciji na performanse mrežne komunikacija. Ovo istraživanje je prepoznalo i klasificiralo različite tipove asimetrije. Svaki tip je testiran u sklopu simulacijskog eksperimenta u stvarnim scenarijima. Pokazalo se je da asimetrija negativno utječe na mrežne performanse, međutim taj efekt nije značajan jer uzrokuje manje od 0.5 % neuspješno poslanih poruka. Glavni fokus istraživanja je razvoj novog i pojednostavljenog MAC protokola za VLC komunikaciju između automobila. Kako bi se razvio novi MAC protokol nad VLC tehnologijom u prometnim mrežama, bilo je nužno napraviti i novu razvojnu okolinu koja se bazira na postojećim mrežnim simulatorima. Novi VLCMAC protokol za komunikaciju između automobila je testiran koristeći definirani set metrika. Testovi su napravljeni u obliku simulacijskih eksperimenata u kojima su uspored¯ivane performanse novog i referentnog protokola. Referentni protokol, u ovom istraživanju je IEEE 802.11b MAC protokol. U sklopu ovog rada definiran je i model vozila opremljen VLC tehnologijom. U simulacijskim eksperimentima je korišten isti model vozila za oba protokola. Za potrebe istraživanja je definirano jedanaest simulacijskih eksperimenata, svaki od njih opisuje specifične situacije u mrežnim komunikacijama kao i u prometu. Završni simulacijski scenariji uključuju okolinu iz stvarnosti, mreža ulica grada Suffolka, SAD. Osim stvarnih ulica, vozila su se kretala i razmjenjivala podatke koristeći mrežnu komunikaciju na kompletnom ISO/OSI mrežnom stogu sa zamijenjenim MAC podslojem. Razvojna okolina uključuje preciznu provjeru fizičkih karakteristika na razini putanje zrake svjetlosti. Ova preciznost je bila nužna kako bi simulacije bile što vjerodostojnije stvarnim sustavima. Obzirom da se radi o mnogo kalkulacija, obično računalo nije dostatno za izvođenje simulacijskih eksperimenata; zbog toga su se eksperimenti izvodili na klasteru računala Sveučilišta u Zagrebu. Koristeći definirane metrike, istraživanje je pokazalo kako je novi VLC MAC protokol za komunikaciju između automobila bolji od referentnog protokola.