1,721,014 research outputs found
LiFi reference channel models: office, home, hospital
No full textPurpose To introduce reference channel models for the evaluation of different PHY proposals. Notice This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material.European Unio
Channel modelling for indoor visible light communications
No full textVisible light communication (VLC) allows the dual use of light-emitting diodes (LEDs) for wireless communication purposes in addition to their primary purpose of illumination. As in any other communication system, realistic channel modelling is a key for VLC system design, analysis and testing. In this paper, we present a comprehensive survey of indoor VLC channel models. In order to set the background, we start with an overview of infrared (IR) channel modelling, which has received much attention in the past, and highlight the differences between visible and IR optical bands. In the light of these, we present a comparative discussion of existing VLC channel modelling studies and point out the relevant advantages and disadvantages. Then, we provide a detailed description of a site-specific channel modelling approach based on non-sequential ray tracing that precisely captures the optical propagation characteristics of a given indoor environment. We further present channel models for representative deployment scenarios developed through this approach that were adopted by the Institute of Electrical and Electronics Engineering (IEEE) as reference channel models. Finally, we consider mobile VLC scenarios and investigate the effect of receiver location and rotation for a mobile indoor user.TÜBİTAKPublisher versio
Effect of LED wiring and cabling topologies on visible light communication channels
No full textVisible light communication (VLC) is an emerging short-range wireless access technology. It involves the dual use of illumination infrastructure for communication purposes and builds upon the principle of modulating light emitting diodes (LEDs) at very high speeds that are not noticeable to the human eye. Although there has been a growing literature on VLC channel modeling, the existing works mainly overlook the effects of wiring and cabling topologies. Wiring topology refers to how LED chips are connected within the luminaire while cabling topology refers to how the luminaires are connected to the communication access point. In this paper, we adopt ray-tracing based VLC channel modeling approach and consider various cabling/wiring topologies. For each topology, we obtain channel impulse responses (CIRs) and quantify the impact of wiring and cabling delays.TÜBİTA
Performance characterization of underwater visible light communication
No full textIn this paper, we investigate the performance limits of underwater visible light communication (UVLC) systems. We first develop a closed-form path loss expression as a function of transceiver parameters and water type. We then utilize this new expression to determine the maximum achievable link distance for UVLC systems in pure sea, clear ocean, coastal water, and harbor water. Our results demonstrate that the maximum achievable distance is limited to a few tens of meters. This necessitates the deployment of relay-assisted UVLC systems to extend the transmission range. We consider both detect-and-forward and amplify-and-forward relaying. For each relaying method, we first consider a dual-hop UVLC system and determine optimal relay placement to minimize the bit error rate (BER). Then, we consider a multi-hop system with equidistant relays and determine the maximum achievable distance for a given number of hops to satisfy a targeted end-to-end BER.TÜBİTA
Görünür ışık haberleşmesi için kanal modelleme ve nitelendirme: içmekan, araçsal ve sualtı kanallar
No full textDespite the increasing attention on visible light communications (VLC) systems, there is a lack of proper visible light (VL) channel models. This is a serious concern since channel modeling is the very first step for efficient, reliable, and robust VLC system design. This dissertation focuses on channel modeling and characterization study for indoor, vehicular and underwater VLC. Our study is based on Zemax®; a commercial optical and illumination design software. Although the main purpose of such software is optical system design, we take advantage of the ray tracing features of this software which allows an accurate description of the interaction of rays emitted from the lighting source within a specified confined space. The simulation environment is created in Zemax® and enables us to specify the geometry of the environment, the objects within as well as the specifications of the sources (i.e., LEDs) and receivers (i.e., photodiodes). For a given number of rays and the number of reflections, the non-sequential ray tracing tool calculates the detected power and path lengths from source to detector for each ray. These are then imported to Matlab® and processed to yield the channel impulse response (CIR). In contrary to existing works which are mainly limited to ideal Lambertian sources and purely diffuse reflections, our approach is capable to obtain CIRs for any non-ideal sources as well as specular and mixed specular-diffuse reflections. Furthermore, we can precisely reflect the presence of objects and wavelength-dependent reflection characteristics of surface materials in channel study.
In the first part of this thesis, we propose a realistic indoor channel modeling approach and carry out a detailed channel characterization study. We also investigate the effect of user mobility and receiver orientation on CIRs. In the second part of this thesis, we present VLC channel models for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) taking into account the asymmetrical pattern of headlamp and street lights, reflections from road surfaces and weather conditions. We further develop a closed-form path loss expression for V2V VLC channel for different weather conditions. In the last part of this thesis, we carry out a detailed underwater optical channel modeling and characterization study taking into account the reflection characteristics of the sea surface and sea bottom as well as the water characteristics, i.e., extinction coefficient, and scattering phase function of particles. We develop a closed-form path loss expression as an explicit function of water type, beam divergence angle and receiver aperture diameter and validate the accuracy of the proposed expression through Monte Carlo simulation results.Görünür ışık haberleşmesi (visible light communication-VLC) sistemlerine olan artan ilgiye ragmen, uygun görününür ışık (visible light-VL) kanal modelleri eksikliği
mevcuttur. Verimli, güvenilir ve dirençli VLC sistem tasarımı için ilk adım kanal modelleme olduğundan, bu eksiklik ciddi bir sorundur. Bu tezin odağı, içmekan,
taşıtlara ilişkin, ve sualtı VLC için kanal modelleme ve nitelendirme çalışmalarıdır. Çalışmamız, ticari bir optik ve aydınlatma tasarımı yazılımı olan Zemax® tabanlıdır. Bu yazılımın ana amacı optik sistem tasarımı olmasına ragmen, biz bu yazılımın, belirli bir kapalı alanda, bir aydınlatma kaynağından yayılmış olan ışınların etkileşimlerini hassas bir şekilde tarif eden, ışın takibi özelliklerinden faydalanıyoruz. Zemax®’te oluşturulan
simülasyon ortamı, ortamın geometrisini, ortamda bulunan nesneleri, ve ayrıca kaynakların (yani LEDler) ve alıcıların (yani fotodiyotlar) teknik özelliklerini
nitelendirmemize imkan tanımaktadır. Belirli bir sayıda ışın ve yansıma sayısı için, ardışık olmayan ışın takibi aracı, her ışın için saptanan gücü ve kaynaktan detektöre olan yol uzunluğunu hesaplar. Bu veriler daha sonra Matlab®’e aktarılır ve kanal dürtü yanıtlarını (channel impulse response-CIR) elde etmek üzere işlenir. Genel olarak ideal Lambertian kaynaklar ve sadece dağınık yansımalar ile sınırlı olan mevcut çalışmaların aksine, bizim yaklaşımımız, herhangi bir ideal olmayan kaynak, ve ayrıca dik açılı ve
dik açılı-dağınık karışık yansımalar için de kanal dürtü yanıtlarını elde edebilmektedir. Dahası, ortamda nesnelerin mevcudiyetini ve dalgaboyuna bağımlı yansıma karakteristiklerini de kanal çalışmasına yansıtabilmekteyiz. Bu tezin ilk kısmında, gerçekçi bir içmekan kanal modelleme yaklaşımı sunuyor
ve detaylı bir kanal niteleme çalışması yürütüyoruz. Aynı zamanda kullanıcı hareketliliği ve alıcının baktığı yönün CIRlar üzerindeki etkisini de araştırıyoruz. Tezin
ikinci kısımda, farların ve sokak lambalarının asimetrik modellerini, yol yüzeyinden yansımaları ve hava koşullarını da dikkate alarak araçtan araca (vehicle-to-vehicle–V2V) ve araçtan altyapıya (vehicle-to-infrastructure–V2I) VLC kanal modellerini sunuyoruz. Ayrıca, farklı hava koşullarında V2V VLC kanalı için kapalı yapıda bir yol kaybı ifadesi ortaya koyuyoruz. Bu tezin son kısmında, deniz yüzeyinin ve tabanının yansıtma karakteristiklerini, ve ayrıca suyun karakteristiklerini (yani, sönüm katsayısı, ve parçacıkların saçılım faz fonksiyonu) de hesaba katarak, detaylı bir sualtı optik kanal modelleme ve nitelendirme çalışması yürütüyoruz. Yol kaybının, su tipine, ışın demeti sapma açısına, ve alıcı açıklığı çapına bağlı bir fonksiyon olan kapalı yapıda bir ifadesini geliştiriyor ve ortaya konan bu ifadenin doğrulunu Monte Carlo simülasyon sonuçları ile onaylıyoruz
Mixture-kernel based post-distortion in RKHS for time-varying VLC channels
No full textVisible light communication (VLC) based systems are a viable green supplement to existing radio frequency based communication systems. However, it has been found that the performance of VLC based systems is impaired in conditions when the users are mobile with respect to the transmit luminaire. The relative motion of the mobile users with respect to the luminaire renders the overall VLC channel to be time-varying. Recently, the impact of user mobility on the overall channel impulse response has been modeled by a generalized time-varying VLC channelmodel, which necessitates for an efficient mechanism at the receiver to tackle this phenomenon. In addition to user mobility, the inter-symbol interference, and the nonlinear characteristics of the light emitting diode are major factors that limit throughput of a VLC-based communication system. To mitigate these impairments, existing techniques such as Volterra/Hammerstein based receivers suffer from modeling error due to truncation of the polynomial kernel till second order terms. Recently, sparse reproducing kernel Hilbert space (RKHS) based methods have been suggested that guarantee universal approximation with the reasonable computational simplicity. However, the choice of a single hyper-parameter restricts its ability to model time-varying channels/systems. Therefore, this paper proposes a novel RKHS based post-distorter that adaptively learns a sparse dictionary based on the incoming observations, and monitors validity of the dictionary based on a proposed metric in RKHS. In order to mitigate the time-varying VLC channel based on this metric, a criterion for clearing the contents of the existing dictionary is proposed, and the requirement to learn a new dictionary is detected. Furthermore, the concept of mixture-adaptive kernel learning is introduced in this work for the minimum symbol error rate (MSER) criterion. From the convergence analysis presented in this paper, faster mean squared error (MSE) convergence is proved for the mixture-kernel based post-distorter. Additionally, it is also proven that for a given step-size, the proposed mixture-kernel MSER post-distorter always converges to a lower MSE as compared to the classical single-kernel MSER.TÜBİTA
15-15-0747-00-007a-tg7r1-cirs-channel-model-document-for-high-rate-pd-communications
Full text linkThe LiFi channels developed by Prof. Murat Uysal and Mr. Miramirkhani were selected as the "LiFi Reference Channel Models" by the IEEE 802.15.7r Task Group during the IEEE's latest meeting held in Bangkok, Thailand, in September. Accordingly, all companies, universities and research institutions are required to use these channel models as reference for their performance assessments and comparative analysis in the standardization proposals they will submit over the coming months. The channel models developed by them are the most realistic models available in the literature and pointed out the significance of recognition and adoption of these models by industry
IEEE 802.11bb reference channel models for indoor environments
Full text linkThis contribution proposes 802.11bb reference channel models for indoor environments
LiFi channel models: office, home, manufacturing cell
No full textPurpose Providing channel models which allow a fair comparison of different physical layer (PHY) High Rate PD Communications proposals submitted to TG7r1 in response to the Call for Proposals (CFP). ... Notice This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material
Channel modeling and characterization for visible light communications
No full textDue to copyright restrictions, the access to the full text of this article is only available via subscription.In this paper, we present a comprehensive channel modeling and characterization study for visible light communications. Our study is based on ray tracing, which allows for an accurate description of the interaction of rays emitted from the lighting source within a specified confined space. Contrary to existing works, which are mainly limited to ideal Lambertian sources and purely diffuse reflections, our approach is capable of obtaining channel impulse responses (CIRs) for any nonideal sources, as well as specular and mixed specular-diffuse reflections. Furthermore, we can precisely reflect the presence of objects (e.g., furniture) and wavelength-dependent reflection characteristics of surface materials (e.g., ceilings, floor, walls, and furniture) in a channel study. As case studies, we consider a number of indoor environments with various dimensions and different surface materials, i.e., plaster, gloss paint, wood, aluminum metal, and glass. We further consider various scenarios with different transmitter specifications (i.e., single versus multiple transmitters and array type) and receiver specifications (i.e., location and rotation). For each environment, we obtain CIRs and present a channel characterization study where channel parameters, such as channel DC gain, root mean square (RMS) delay spread, coherence bandwidth, and mean excess delay, are obtained. We also make one-to-one comparisons between infrared and visible-light CIRs for the same environments to emphasize the differences between two optical bands.Qatar Foundatio
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