ЕКСПЕРИМЕНТАЛЬНЕ ВИЗНАЧЕННЯ ОПТИМАЛЬНИХ ПАРАМЕТРІВ РОБОТИ ТЕЛЕКОНФЕРЕНЦІЇ НА МОБІЛЬНИХ ПРИСТРОЯХ

The article considers the problem of ensuring the availability and integrity of wireless subscribers in cellular and other wireless corporate networks. The article aims to determine the threshold values for the moment of failure of video transmission, quantitative parameters, artifacts, and the number of errors for the image. Show the dependence of the integrity of data transmitted in real-time on the characteristics of the environment. Two approaches were used to assess the quality of video information: qualitative (image recognition assessment) and quantitative (error measurement). Because the research program was written in the Kotlin programming language, a library written in Java or Kotlin was required. After searching the library, it turned out that only three libraries meet such parameters as reliability, relevance, and availability of documentation: Jaffree, Xuggler, and VLCJ. After gathering information, it was found that the most common screen extensions for desktops are 1366 × 768 and for phones—360 × 640. An error occurred that RTP did not support more than one connection. Also, the RTSP protocol could not pass the experiment on codecs other than MP4V. The experiment stopped earlier than necessary without error. Judging by the indicators, this was a very high CPU load. All other protocols were successfully tested, and results were obtained. During the experiments, we encountered various video anomalies. The worst was the video playback problem with the MJPG codec. Other anomalies were also identified: frame delay, incorrect frame rendering, white noise, and white noise mixed with frames. It is clear how up to 128 kbps experiments are successful and then begin to stop the video stream without error information. According to the results of experiments, the H.264 codec performs best.В статті розглянута проблема забезпечення доступності та цілісності безпроводових абонентів у стільникових та інших безпроводових корпоративних мережах. Метою статті є визначення порогових значень для моменту зриву передавання відеосигналу, кількісні параметри, артефакти і кількість помилок для зображення. Показати залежність цілісність даних, переданих в режимі реального часу, від характеристик середовища. Для оцінки якості відеоінформації були застосовані два підходи: якісний (оцінка розпізнавання зображення) і кількісний (вимірювання кількості помилок). Оскільки програма для проведення дослідження була написана на мові програмування Kotlin, то була потрібна бібліотека написана на Java або Kotlin. Після проведення пошуку бібліотеки виявилося, що бібліотек які задовольняють таким параметрам як: надійність, актуальність та наявність документації, лише три: Jaffree, Xuggler і VLCJ. Після збору інформації було встановлено, що найпоширенішими розширеннями екрану для настільних комп’ютерів є 1366×768 і для телефонів — 360×640. Виявилася помилка, що протокол RTP не підтримував більше одного підключення. Також протокол RTSP не зміг пройти дослід на інших кодеках крім MP4V, дослід припинявся раніше ніж потрібно без помилки, судячи по показникам причиною цьому була дуже велика загрузка процесора. Всі інші протоколи успішно пройшли дослід і були отримані результати. Під час проведення дослідів, ми зіткалися з різними аномаліями відео. сама найгірша була, проблема з відтворення відео у кодека MJPG. Також були виявлені інші аномалії: затримка кадрів, некоректне відмальовування кадрів, білий шум і білий шум в перемішку з кадрами. Добре видно як до 128 кбіт/с досліди проходять успішно, а потім починаються припинення відеопотоку без інформації про помилку. За результатами дослідів найкраще себе проявляє кодек H.26

DROiD: Adapting to Individual Mobility Pays Off in Mobile Data Offloading

International audienceCellular operators count on the potentials of offloading techniques to relieve their overloaded data channels. Beyond standard access point-based offloading strategies, a promising alternative is to exploit opportunistic direct communication links between mobile devices. Nevertheless, achieving efficient device- to-device offloading is challenging, as communication opportunities are, by nature, dependent on individual mobility patterns. We propose, design, and evaluate DROiD (Derivative Reinjection to Offload Data), an original method to finely control the distribution of popular contents throughout a mobile network. The idea is to use the infrastructure resources as seldom as possible. To this end, DROiD injects copies through the infrastructure only when needed: (i) at the beginning, in order to trigger the dissemination, (ii) if the evolution of the opportunistic dissemination is below some expected pace, and (iii) when the delivery delay is about to expire, in order to guarantee 100% diffusion. Our strategy is particularly effective in highly dynamic scenarios, where sudden creation and dissolution of clusters of mobile nodes prevent contents to diffuse properly.We assess the performance of DROiD by simulating a traffic information service on a realistic large-scale vehicular dataset composed of more than 10,000 nodes. DROiD substantially outperforms other offloading strategies, saving more than 50% of the infrastructure traffic even in the case of tight delivery delay constraints. DROiD allows terminal- to-terminal offloading of data with very short maximum reception delay, in the order of minutes, which is a realistic bound for cellular user acceptance

Bio-Inspired Tools for a Distributed Wireless Sensor Network Operating System

The problem which I address in this thesis is to find a way to organise and manage a network of wireless sensor nodes using a minimal amount of communication. To find a solution I explore the use of Bio-inspired protocols to enable WSN management while maintaining a low communication overhead. Wireless Sensor Networks (WSNs) are loosely coupled distributed systems comprised of low-resource, battery powered sensor nodes. The largest problem with WSN management is that communication is the largest consumer of a sensor node’s energy. WSN management systems need to use as little communication as possible to prolong their operational lifetimes. This is the Wireless Sensor Network Management Problem. This problem is compounded because current WSN management systems glue together unrelated protocols to provide system services causing inter-protocol interference. Bio-inspired protocols provide a good solution because they enable the nodes to self-organise, use local area communication, and can combine their communication in an intelligent way with minimal increase in communication. I present a combined protocol and MAC scheduler to enable multiple service protocols to function in a WSN at the same time without causing inter-protocol interference. The scheduler is throughput optimal as long as the communication requirements of all of the protocols remain within the communication capacity of the network. I show that the scheduler improves a dissemination protocol’s performance by 35%. A bio-inspired synchronisation service is presented which enables wireless sensor nodes to self organise and provide a time service. Evaluation of the protocol shows an 80% saving in communication over similar bio-inspired synchronisation approaches. I then add an information dissemination protocol, without significantly increasing communication. This is achieved through the ability of our bio-inspired algorithms to combine their communication in an intelligent way so that they are able to offer multiple services without requiring a great deal of inter-node communication.Open Acces

Assessing Learning Achievements when Reducing Mobile Video Quality

When using mobile phones for learning purpose, video content is considered to be the preferred type of multimedia content. However, the video file has a big size in comparison to text or audio and might lead to a high delivery cost when transmitted over a mobile network, a cost that not all users are willing to pay. Concerns regarding the monetary cost for accessing data content through mobile networks have been raised by various researchers. A solution that considers the user preference for trading off between video quality and price in order to reduce the content delivery cost is presented. This paper also evaluates the proposed solution and presents the results of an experimental study that assesses the video content adaptation impact on information assimilation. The results show that although the video quality is reduced information assimilation is not negatively affected by the adaptation. This holds true regardless of the mobile device used in the study

What can people risk attitude tell us about people preference for multimedia quality?

Purpose – Multimedia content that is accessible through mobile devices has a larger size than other types of content (e.g. text, images). This may lead to higher prices for accessing the content via mobile devices, as mobile operators are capping mobile data billing plans in an effort to increase their revenues and prevent congestion. This poses problems for the users that are not willing/do not afford to pay the required price but still want to use multimedia content through the mobile networks. A price reduction for the user, as well as minimising bandwidth consumption can be obtained as a trade-off in multimedia quality. However, as previous research shows, not all people are willing to trade-off quality for a lower price; therefore, there is no straightforward approach to this problem. In this context, the purpose of this paper is to present a model of user willingness to pay for multimedia content quality as a function of the user risk attitude with the aim to provide personalised content depending on the user willingness to trade-off price for multimedia content quality. Design/methodology/approach – A user model was proposed based on a literature review and an existing data set. A stereotypical approach was used where users are divided in two groups: risk averse and risk seekers. An experimental study involving six scenarios was used to validate the findings. Findings – The results of the evaluation show that for the proposed user risk model, risk seekers preferred to pay for multimedia quality, whereas risk adverse users preferred to switch to a lower multimedia quality when monetary cost is involved. However, when the mobile data billing plan had the bandwidth limited, rather than a higher price to be paid when the bundle quantity was exceeded, the risk averse people’s preference for a lower quality still holds, but it does not show that most of the risk seekers prefer to pay for the multimedia quality. Research limitations/implications – This paper adds to the state of the art by providing a novel way to model the user preferences for multimedia quality based on their attitude towards risk, age, and gender. Practical implications – Mobile data users, content providers (application service providers, over-the-top providers), mobile network operators (MNOs) and internet service providers (ISPs) could benefit from the results of this research. For mobile data users, the outcome of this research could be beneficial, as they can obtain personalised content based on their needs. From the content providers’ point of view, providing personalised content can lead to more satisfied users. It could also reduce the bandwidth consumption and the traffic to the server and/or proxy. Reducing the bandwidth consumption could lead to the possibility to acquire more customers and hence increase the revenues. Originality/value – This is among the first studies to assess how the user preference towards multimedia quality if affected by the user attitude towards risk

Taming the waters that taketh from the devil’s playground: A history of flood control in Clark County, Nevada, 1955-2010

The Las Vegas valley is the driest metropolis in the United States, with an annual rainfall of less than five inches. A large majority of the annual precipitation occurs between May and September in the form of high intensity thunderstorms. Since the founding of Las Vegas in 1905 until the formation of the Clark County Regional Flood Control District in 1986, the five jurisdictions that make up the Las Vegas valley: Las Vegas, North Las Vegas, Henderson, Boulder City, and Clark County, struggled to manage stormwater. The principal defect was that they reflected the particular whims of each government entity, largely ignoring the nagging geologic characteristics that made the valley so susceptible to flooding. Often, dikes and flood channels built in one city were not integrated with those in the adjoining city. After devastating floods in 1983 and 1984 exploited the gaps in the patch-work flood control system, a group of progressive minded politicians, engineers, and citizens aggressively campaigned for the formation of a regional flood control district. In 1986 Clark County residents approved a one-quarter of one-percent sales tax increase for the funding for the flood control district. Over the past quarter-century, the Clark County Regional Flood Control District funded a network of detention basins and flood channels throughout Clark County, which helped manage the massive physical expansion of the Las Vegas valley in the 1990s and early 2000

7. GI/ITG KuVS Fachgespräch Drahtlose Sensornetze

In dem vorliegenden Tagungsband sind die Beiträge des Fachgesprächs Drahtlose Sensornetze 2008 zusammengefasst. Ziel dieses Fachgesprächs ist es, Wissenschaftlerinnen und Wissenschaftler aus diesem Gebiet die Möglichkeit zu einem informellen Austausch zu geben – wobei immer auch Teilnehmer aus der Industrieforschung willkommen sind, die auch in diesem Jahr wieder teilnehmen.Das Fachgespräch ist eine betont informelle Veranstaltung der GI/ITG-Fachgruppe „Kommunikation und Verteilte Systeme“ (www.kuvs.de). Es ist ausdrücklich keine weitere Konferenz mit ihrem großen Overhead und der Anforderung, fertige und möglichst „wasserdichte“ Ergebnisse zu präsentieren, sondern es dient auch ganz explizit dazu, mit Neueinsteigern auf der Suche nach ihrem Thema zu diskutieren und herauszufinden, wo die Herausforderungen an die zukünftige Forschung überhaupt liegen.Das Fachgespräch Drahtlose Sensornetze 2008 findet in Berlin statt, in den Räumen der Freien Universität Berlin, aber in Kooperation mit der ScatterWeb GmbH. Auch dies ein Novum, es zeigt, dass das Fachgespräch doch deutlich mehr als nur ein nettes Beisammensein unter einem Motto ist.Für die Organisation des Rahmens und der Abendveranstaltung gebührt Dank den beiden Mitgliedern im Organisationskomitee, Kirsten Terfloth und Georg Wittenburg, aber auch Stefanie Bahe, welche die redaktionelle Betreuung des Tagungsbands übernommen hat, vielen anderen Mitgliedern der AG Technische Informatik der FU Berlin und natürlich auch ihrem Leiter, Prof. Jochen Schiller

A New Competitive Ratio for Network Applications with Hard Performance Guarantee

Online algorithms are used to solve the problems which need to make decisions without future knowledge. Competitive ratio is used to evaluate the performance of an online algorithm. This ratio is the worst-case ratio between the performance of the online algorithm and the offline optimal algorithm. However, the competitive ratios in many current studies are relatively low and thus cannot satisfy the need of the customers in practical applications. To provide a better service, a practice for service provider is to add more redundancy to the system. Thus we have a new problem which is to quantify the relation between the amount of increased redundancy and the system performance. In this dissertation, to address the problem that the competitive ratio is not satisfactory, we ask the question: How much redundancy should be increased to fulfill certain performance guarantee? Based on this question, we will define a new competitive ratio showing the relation between the system redundancy and performance of online algorithm compared to offline algorithm. We will study three applications in network applications. We propose online algorithms to solve the problems and study the competitive ratio. To evaluate the performances, we further study the optimal online algorithms and some other commonly used algorithms as comparison. We first study the application of online scheduling for delay-constrained mobile offloading. WiFi offloading, where mobile users opportunistically obtain data through WiFi rather than through cellular networks, is a promising technique to greatly improve spectrum efficiency and reduce cellular network congestion. We consider a system where the service provider deploys multiple WiFi hotspots to offload mobile traffic with unpredictable mobile users’ movements. Then we study online job allocation with hard allocation ratio requirement. We consider that jobs of various types arrive in some unpredictable pattern and the system is required to allocate a certain ratio of jobs. We then aim to find the minimum capacity needed to meet a given allocation ratio requirement. Third, we study online routing in multi-hop network with end-to-end deadline. We propose reliable online algorithms to schedule packets with unpredictable arriving information and stringent end-to-end deadline in the network

Data Fusion at Scale in Astronomy

We have arrived in an era where we face a deluge of data streaming in from countless sources and across virtually all disciplines; This holds especially true for data intensive sciences such as astronomy where upcoming surveys such as the LSST are expected to collect tens of terabytes per night, upwards of 100 Petabytes in 10 years. The challenge is keeping up with these data rates and extracting meaningful information from them. We present a number of methods for combining and distilling vast astronomy datasets using GPUs. In particular we focus on cross-matching catalogs containing close to 0.5 Billion sources, optimally combining multi-epoch imagery and computationally extracting color from monochrome telescope images