Superimposed radio signals in wireless sensor networks

Drahtlose Sensornetzwerke sind Netzwerke, die aus einer Vielzahl von Kleinstrechnern aufgebaut werden. Diese Kleinstrechner sind typischerweise sehr ressourcenarm und leistungsschwach. Sie tragen eine Funkkommunikationseinheit mit der sie zu anderen Kleinstrechnern (sog. Funkknoten) Nachrichten austauschen können. Diese Nachrichten können auch stückweise von Knoten zu Knoten über weite Distanzen weitergeleitet werden. In einem solchen Fall spricht man von Multi-hop Kommunikation. Funkknoten können durch bestimmte Mechanismen Nachrichten automatisch weiterleiten und Nachrichtenwege selbständig im Netzwerk etablieren. Ein Systemaufbau von vielen leistungsschwachen Knoten legt es nahe, auf möglichst vielen Ebenen der Systemarchitektur kooperative Mechanismen zu nutzen. Überlagerte Funksignale sind ein solcher Kooperationsmechanismus. Sie treten immer dann auf, wenn mehrere Quellen zugleich auf der gleichen Frequenz Signale aussenden. Die vorliegende Arbeit stellt das Konzept der überlagerten Funksignale dar und zeigt eine Reihe von Nutzungsmöglichkeiten in drahtlosen Sensornetzen. Die Randbedingungen sind hier stets eine sehr leistungsschwache Hardware. Unter diesen Voraussetzungen werden mit Hilfe der neuen Modelle grundsätzliche Probleme in drahtlosen Sensornetzwerken wie Zeitsynchronisation, Zuverlässigkeit, Kanalnutzung und Datenfusion, gelöst. Die Basis bildet das neue Modulationsverfahren (ESK, energy shift keying), welches überlagerte Funksignale für Gruppen von Funkknoten ermöglicht. Dieses Übertragungsverfahren ist speziell für sehr einfach aufgebaute Hardware geeignet und basiert auf reiner Energiedetektion. In vielen Implementierungen und Studien wird der praktische Nutzen von überlagerten Funksignalen gezeigt. Die Anwendungen reichen von Ultraschall-Lokationssystemen über Warenerkennung im Supermarkt bis hin zu Echtzeit-Zugriffsmechansimen für verteilte Funksysteme.Wireless sensor networks consist of a number of embedded computers. These embedded computers are typically very weak in energy and computing power but carry a wireless communication unit to exchange packet messages with other embedded computer (called nodes). The messages can be transported from one to another node building multi-hop communication. Nodes are capable of automatically forwarding messages and establishing routes for messages through the network. Such systems of a number of weak nodes can greatly benefit of cooperative mechanisms. Superimposed radio signals are such a cooperative mechanisms. They occur whenever two or more nodes emit radio signals at the same time and in the same frequency band. This work presents a new concept for superimposed radio signals and shows various use-cases in wireless sensor network. The constraints are the weak hardware with limited computing and energy resources. New models are derived and presented that can solve principal problem in wireless sensor networks such as time synchronization, channel usage, reliability and data fusion. Basis for all contributions is the new modulation scheme for superimposed radio signals call ESK (energy shift keying). ESK is a multi-stage modulation based on energy detection in the receiver, enabling superimposed radio signals for a group of sensor nodes. Various Implementations and studies are presented that illustrate the practical use of superimposed radio signals. The applications range from ultrasound location systems over item handing in a retail store to real-time access protocols in wireless distributed systems

Smart-Its - communication and sensing technology for UbiComp environments

More and more Ubiquitous computing scenarios arise where computers are embedded into everyday objects as secondary ariefacts. The need for a generic platform to enhance such artifacts is addressed by the Smart-Its project. TecOs Smart- Its are small-scale embedded computer devices that can be easily attached to everyday objects and simply programmed for a special task. Just like paper Post-Its are able to add some information to an object a Smart-Its could add some computing, perception and communication capability to an object. All this capability was integrated into the tiny Smart-Its board itself that is able to operate without any additional infrastructure. This paper introduces the architecture of the Smart-Its hardware, the design decisions for the hardware itself and presents experiences we made while constructing and operating these devices; some of these experience are also based on the deployment and use of the first 160 Smart-Its devices

ConCom - a language and protocol for communication of context

With ConCom, we address the area of communication in wireless networks. We focus on heterogeneous settings with highly mobile devices carrying limited resources. ConCom present a way to express and communicate information, especially context, in a way that is similar to a naturally spoken language. ConCom uses sentences with a subject and attributes in its structure to represent and organize the transport of context and data. ConCom works connectionless and without addressing and forms an efficient way to exchange information in ubiquitous computing environments. We implemented ConCom and show applications taking advantage of it

Applications of graph theory to landscape genetics

We investigated the relationships among landscape quality, gene flow, and population genetic structure of fishers (Martes pennanti) in ON, Canada. We used graph theory as an analytical framework considering each landscape as a network node. The 34 nodes were connected by 93 edges. Network structure was characterized by a higher level of clustering than expected by chance, a short mean path length connecting all pairs of nodes, and a resiliency to the loss of highly connected nodes. This suggests that alleles can be efficiently spread through the system and that extirpations and conservative harvest are not likely to affect their spread. Two measures of node centrality were negatively related to both the proportion of immigrants in a node and node snow depth. This suggests that central nodes are producers of emigrants, contain high-quality habitat (i.e., deep snow can make locomotion energetically costly) and that fishers were migrating from high to low quality habitat. A method of community detection on networks delineated five genetic clusters of nodes suggesting cryptic population structure. Our analyses showed that network models can provide system-level insight into the process of gene flow with implications for understanding how landscape alterations might affect population fitness and evolutionary potential

Test beam performance measurements for the Phase I upgrade of the CMS pixel detector

A new pixel detector for the CMS experiment was built in order to cope with the instantaneous luminosities anticipated for the Phase I Upgrade of the LHC. The new CMS pixel detector provides four-hit tracking with a reduced material budget as well as new cooling and powering schemes. A new front-end readout chip mitigates buffering and bandwidth limitations, and allows operation at low comparator thresholds. In this paper, comprehensive test beam studies are presented, which have been conducted to verify the design and to quantify the performance of the new detector assemblies in terms of tracking efficiency and spatial resolution. Under optimal conditions, the tracking efficiency is (99.95 ± 0.05) %, while the intrinsic spatial resolutions are (4.80 ± 0.25) μm and (7.99 ± 0.21) μm along the 100 μm and 150 μm pixel pitch, respectively. The findings are compared to a detailed Monte Carlo simulation of the pixel detector and good agreement is found.Peer reviewe

Trapping in irradiated p-on-n silicon sensors at fluences anticipated at the HL-LHC outer tracker

The degradation of signal in silicon sensors is studied under conditions expected at the CERN High-Luminosity LHC. 200 $\mu$m thick n-type silicon sensors are irradiated with protons of different energies to fluences of up to $3 \cdot 10^{15}$ neq/cm$^2$. Pulsed red laser light with a wavelength of 672 nm is used to generate electron-hole pairs in the sensors. The induced signals are used to determine the charge collection efficiencies separately for electrons and holes drifting through the sensor. The effective trapping rates are extracted by comparing the results to simulation. The electric field is simulated using Synopsys device simulation assuming two effective defects. The generation and drift of charge carriers are simulated in an independent simulation based on PixelAV. The effective trapping rates are determined from the measured charge collection efficiencies and the simulated and measured time-resolved current pulses are compared. The effective trapping rates determined for both electrons and holes are about 50% smaller than those obtained using standard extrapolations of studies at low fluences and suggests an improved tracker performance over initial expectations

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis