157 research outputs found

    Distributed Time Division Multiple Access (DTDMA) Medium Access Control Protocol For Wireless Sensor Networks [TK7872.D48 W872 2008 f rb].

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    Rangkaian sensor tanpa wayar menerima perhatian yang memberangsangkan sejak beberapa tahun yang lalu disebabkan oleh peningkatan permintaan terhadap perisian kadar rendah, murah dan menjimatkan tenaga seperti operasi perkilangan, ketenteraan, kesihatan, pengawasan alam sekitar, sekuriti, operasi penyelamatan dan komunikasi tanpa wayar. Wireless Sensor Networks (WSNs) received tremendous attention over the last few years due to increasing demand for low data rate, low-cost and low power applications in industries like factory automation, military, health and hospitality,environment monitoring, security, search and rescue, and wireless communications

    Supporting Large Scale Communication Systems on Infrastructureless Networks Composed of Commodity Mobile Devices: Practicality, Scalability, and Security.

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    Infrastructureless Delay Tolerant Networks (DTNs) composed of commodity mobile devices have the potential to support communication applications resistant to blocking and censorship, as well as certain types of surveillance. In this thesis we study the utility, practicality, robustness, and security of these networks. We collected two sets of wireless connectivity traces of commodity mobile devices with different granularity and scales. The first dataset is collected through active installation of measurement software on volunteer users' own smartphones, involving 111 users of a DTN microblogging application that we developed. The second dataset is collected through passive observation of WiFi association events on a university campus, involving 119,055 mobile devices. Simulation results show consistent message delivery performances of the two datasets. Using an epidemic flooding protocol, the large network achieves an average delivery rate of 0.71 in 24 hours and a median delivery delay of 10.9 hours. We show that this performance is appropriate for sharing information that is not time sensitive, e.g., blogs and photos. We also show that using an energy efficient variant of the epidemic flooding protocol, even the large network can support text messages while only consuming 13.7% of a typical smartphone battery in 14 hours. We found that the network delivery rate and delay are robust to denial-of-service and censorship attacks. Attacks that randomly remove 90% of the network participants only reduce delivery rates by less than 10%. Even when subjected to targeted attacks, the network suffered a less than 10% decrease in delivery rate when 40% of its participants were removed. Although structurally robust, the openness of the proposed network introduces numerous security concerns. The Sybil attack, in which a malicious node poses as many identities in order to gain disproportionate influence, is especially dangerous as it breaks the assumption underlying majority voting. Many defenses based on spatial variability of wireless channels exist, and we extend them to be practical for ad hoc networks of commodity 802.11 devices without mutual trust. We present the Mason test, which uses two efficient methods for separating valid channel measurement results of behaving nodes from those falsified by malicious participants.PhDElectrical Engineering: SystemsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120779/1/liuyue_1.pd

    Tracking the path of a mobile radioactive source using a wireless sensor network

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    This report describes several experiments used to characterize and test a network of radiation sensors. The purpose of these tests is to assess the feasibility of using these sensors to detect and track radioactive sources in a large field, as in a battlefield or on a military campus. Simulated radiation measurements are used to compare the result of radiation detection accuracy in tracking the moving target and to find its path as early as possible. This is done via changing the number of sensing nodes deployed (deployment density), as well as the models of the detectors. This thesis describes algorithms for both detecting the presence and tracking the position of radioactive sources. It formulates the detection problem as a nonparametric hypothesis-testing problem that is solved by comparing a statistic computed over some window of observation of the data to a threshold value. If this threshold is exceeded then it is decided that a source is present. The tracking results thus found are compared with the actual chosen path within the implemented experiment. Detection delay has been measured while trading off battery consumption and accuracy

    Smart Street Lights and Mobile Citizen Apps for Resilient Communication in a Digital City

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    Currently, nearly four billion people live in urban areas. Since this trend is increasing, natural disasters or terrorist attacks in such areas affect an increasing number of people. While information and communication technology is crucial for the operation of urban infrastructures and the well-being of its inhabitants, current technology is quite vulnerable to disruptions of various kinds. In future smart cities, a more resilient urban infrastructure is imperative to handle the increasing number of hazardous situations. We present a novel resilient communication approach based on smart street lights as part of the public infrastructure. It supports people in their everyday life and adapts its functionality to the challenges of emergency situations. Our approach relies on various environmental sensors and in-situ processing for automatic situation assessment, and a range of communication mechanisms (e.g., public WiFi hotspot functionality and mesh networking) for maintaining a communication network. Furthermore, resilience is not only achieved based on infrastructure deployed by a digital city's municipality, but also based on integrating citizens through software that runs on their mobile devices (e.g., smartphones and tablets). Web-based zero-installation and platform-agnostic apps can switch to device-to-device communication to continue benefiting people even during a disaster situation. Our approach, featuring a covert channel for professional responders and the zero-installation app, is evaluated through a prototype implementation based on a commercially available street light.Comment: 2019 IEEE Global Humanitarian Technology Conference (GHTC

    Distributed Time Division Multiple Access (Dtdma) Medium Access Control Protocol For Wireless Sensor Networks

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    Rangkaian sensor tanpa wayar menerima perhatian yang memberangsangkan sejak beberapa tahun yang lalu Wireless Sensor Networks (WSNs) received tremendous attention over the last few years due to increasing demand for low data rat

    A novel real-time traffic information system based on wireless mesh networks

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    A Low-Cost Search-and-Rescue Drone Platform

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    In this work, an unmanned aerial system is implemented to search an outdoor area for an injured or missing person (subject) without requiring a connection to a ground operator or control station. The system detects subjects using exclusively on-board hardware as it traverses a predefined search path, with each implementation envisioned as a single element of a larger swarm of identical search drones. To increase the affordability of such a swarm, the system cost per drone serves as a primary constraint. Imagery is streamed from a camera to an Odroid single-board computer, which prepares the data for inference by a Neural Compute Stick vision accelerator. A single-class TinyYolo network, trained on the Okutama-Action dataset and an original Albatross dataset, is utilized to detect subjects in the prepared frames. The final network achieves 7.6 FPS in the field (8.64 FPS on the bench) with an 800x480 input resolution. The detection apparatus is mounted on a drone and field tests validate the system feasibility and efficacy

    Secure Communication in Disaster Scenarios

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    Während Naturkatastrophen oder terroristischer Anschläge ist die bestehende Kommunikationsinfrastruktur häufig überlastet oder fällt komplett aus. In diesen Situationen können mobile Geräte mithilfe von drahtloser ad-hoc- und unterbrechungstoleranter Vernetzung miteinander verbunden werden, um ein Notfall-Kommunikationssystem für Zivilisten und Rettungsdienste einzurichten. Falls verfügbar, kann eine Verbindung zu Cloud-Diensten im Internet eine wertvolle Hilfe im Krisen- und Katastrophenmanagement sein. Solche Kommunikationssysteme bergen jedoch ernsthafte Sicherheitsrisiken, da Angreifer versuchen könnten, vertrauliche Daten zu stehlen, gefälschte Benachrichtigungen von Notfalldiensten einzuspeisen oder Denial-of-Service (DoS) Angriffe durchzuführen. Diese Dissertation schlägt neue Ansätze zur Kommunikation in Notfallnetzen von mobilen Geräten vor, die von der Kommunikation zwischen Mobilfunkgeräten bis zu Cloud-Diensten auf Servern im Internet reichen. Durch die Nutzung dieser Ansätze werden die Sicherheit der Geräte-zu-Geräte-Kommunikation, die Sicherheit von Notfall-Apps auf mobilen Geräten und die Sicherheit von Server-Systemen für Cloud-Dienste verbessert

    Crowd-based cognitive perception of the physical world: Towards the internet of senses

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    This paper introduces a possible architecture and discusses the research directions for the realization of the Cognitive Perceptual Internet (CPI), which is enabled by the convergence of wired and wireless communications, traditional sensor networks, mobile crowd-sensing, and machine learning techniques. The CPI concept stems from the fact that mobile devices, such as smartphones and wearables, are becoming an outstanding mean for zero-effort world-sensing and digitalization thanks to their pervasive diffusion and the increasing number of embedded sensors. Data collected by such devices provide unprecedented insights into the physical world that can be inferred through cognitive processes, thus originating a digital sixth sense. In this paper, we describe how the Internet can behave like a sensing brain, thus evolving into the Internet of Senses, with network-based cognitive perception and action capabilities built upon mobile crowd-sensing mechanisms. The new concept of hyper-map is envisioned as an efficient geo-referenced repository of knowledge about the physical world. Such knowledge is acquired and augmented through heterogeneous sensors, multi-user cooperation and distributed learning mechanisms. Furthermore, we indicate the possibility to accommodate proactive sensors, in addition to common reactive sensors such as cameras, antennas, thermometers and inertial measurement units, by exploiting massive antenna arrays at millimeter-waves to enhance mobile terminals perception capabilities as well as the range of new applications. Finally, we distillate some insights about the challenges arising in the realization of the CPI, corroborated by preliminary results, and we depict a futuristic scenario where the proposed Internet of Senses becomes true

    Feasibility of Using Passive Monitoring Techniques in Mesh Networks for the Support of Routing

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    In recent years, Wireless Mesh Networks (WMNs) have emerged as a promising solution to provide low cost access networks that extend Internet access and other networking services. Mesh routers form the backbone connectivity through cooperative routing in an often unstable wireless medium. Therefore, the techniques used to monitor and manage the performance of the wireless network are expected to play a significant role in providing the necessary performance metrics to help optimize the link performance in WMNs. This thesis initially presents an assessment of the correlation between passive monitoring and active probing techniques used for link performance measurement in single radio WMNs. The study reveals that by combining multiple performance metrics obtained by using passive monitoring, a high correlation with active probing can be achieved. The thesis then addresses the problem of the system performance degradation associated with simultaneous activation of multiple radios within a mesh node in a multi-radio environment. The experiments results suggest that the finite computing resource seems to be the limiting factor in the performance of a multi-radio mesh network. Having studied this characteristic of multi-radio networks, a similar approach as used in single radio mesh network analysis was taken to investigate the feasibility of passive monitoring in a multi-radio environment. The accuracy of the passive monitoring technique was compared with that of the active probing technique and the conclusion reached is that passive monitoring is a viable alternative to active probing technique in multi-radio mesh networks
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