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In this paper we investigate the relations between spanners, weak spanners, and power spanners in for any dimension and apply our results to topology control in wireless networks. For , a c-spanner is a subgraph of the complete Euclidean graph satisfying the condition that between any two vertices there exists a path of length at most c-times their Euclidean distance. Based on this ability to approximate the complete Euclidean graph, sparse spanners have found many applications, e.g., in FPTAS, geometric searching, and radio networks. In a weak c-spanner, this path may be arbitrarily long, but must remain within a disk or sphere of radius c-times the Euclidean distance between the vertices. Finally in a c-power spanner, the total energy consumed on such a path, where the energy is given by the sum of the squares of the edge lengths on this path, must be at most c-times the square of the Euclidean distance of the direct edge or communication link.
While it is known that any c-spanner is also both a weak -spanner and a -power spanner for appropriate , depending only on c but not on the graph under consideration, we show that the converse is not true: there exists a family of -power spanners that are not weak C-spanners and also a family of weak -spanners that are not C-spanners for any fixed C. However a main result of this paper reveals that any weak c-spanner is also a C-power spanner for an appropriate constant C.
We further generalize the latter notion by considering -power spanners where the sum of the δth powers of the lengths has to be bounded; so ()-power spanners coincide with the usual power spanners and ()-power spanners are classical spanners. Interestingly, these ()-power spanners form a strict hierarchy where the above results still hold for any some even hold for while counter-examples exist for . We show that every self-similar curve of fractal dimension is not a -power spanner for any fixed C, in general.
Finally, we consider the sparsified Yao-graph (SparsY-graph or YY) that is a well-known sparse topology for wireless networks. We prove that all SparsY-graphs are weak c-spanners for a constant c and hence they allow us to approximate energy-optimal wireless networks by a constant factor.
The Hierarchical Layer Graph (HL graph) is a promising network topology for wireless networks with variable transmission ranges. It was introduced and analyzed by Meyer auf der Heide et al. 2004. In this paper we present a distributed, localized and resource-efficient algorithm for constructing this graph. The qualtiy of the HL graph depends on the domination radius and the publication radius, which affect the amount of interference in the network. These parameters also determine whether the HL graph is a c-spanner, which implies an energy-efficient topology. We investigate the performance on randomly distributed node sets and show that the restrictions on these parameters derived from a worst case analysis are not so tight using realistic settings. Here, we present the results of our extensive experimental evaluation, measuring congestion, dilation and energy. Congestion includes the load that is induced by interfering edges. We distinguish between congestion and realistic congestion where we also take the signal-to-interference ratio into account. Our experiments show that the HL graph contains energy-efficient paths as well as paths with a few number of hops while preserving a low congestion.
Multiple hop routing in mobile ad hoc networks can minimize energy consumption and increase data throughput. Yet, the problem of radio interferences remain. However if the routes are restricted to a basic network based on local neighborhoods, these interferences can be reduced such that standard routing algorithms can be applied.
We compare different network topologies for these basic networks, i.e. the Yao-graph (aka. Θ-graph) and some also known related models, which will be called the SymmYgraph (aka. YS-graph), the SparsY-graph (aka. YY-graph) and the BoundY-graph. Further, we present a promising network topology called the HL-graph (based on Hierarchical Layers).
We compare these topologies regarding degree, spanner-properties, and communication features. We investigate how these network topologies bound the number of (uni- and bidirectional) interferences and whether these basic networks provide energy-optimal or congestion-minimal routing. Then, we compare the ability of these topologies to handle
dynamic changes of the network when radio stations appear and disappear. For this we measure the number of involved radio stations and present distributed algorithms for repairing the network structure.
Forschungsbericht 2013
(2014)
In the engineering domain, representing real-world objects using a body of data, called a digital twin, which is frequently updated by “live” measurements, has shown various advantages over tradi- tional modelling and simulation techniques. Consequently, urban planners have a strong interest in digital twin technology, since it provides them with a laboratory for experimenting with data before making far-reaching decisions. Realizing these decisions involves the work of professionals in the architecture, engineering and construction (AEC) domain who nowadays collaborate via the methodology of building information modeling (BIM). At the same time, the citizen plays an integral role both in the data acquisition phase, while also being a beneficiary of the improved resource management strategies. In this paper, we present a prototype for a “digital energy twin” platform we designed in cooperation with the city of Regensburg. We show how our extensible platform de- sign can satisfy the various requirements of multiple user groups through a series of data processing solutions and visualizations, in- dicating valuable design and implementation guidelines for future projects. In particular, we focus on two example use cases concern- ing building electricity monitoring and BIM. By implementing a flexible data processing architecture we can involve citizens in the data acquisition process, meeting the demands of modern users regarding maximum transparency in the handling of their data.
There has been a lot of research been done in the domain of Wireless Sensor Networks in recent years. Nowadays, Wireless Sensor Networks are in operation in a wide range of different scenarios and applications, like energy management services, heat and water billing as well as smoke detectors. However, research and development will be continued in this domain. During the operation of such a network, software updates need to be done seldom. In contrast to this, software updates need to be done very frequently during development and testing for uploading a new firmware on umpteen nodes. In this paper, we examine such a software update for a particular, but popular and often used sensor network platform. There are already interesting research papers about the process of updating sensor nodes. Our specific focus relies on the technical part of such an update process. We will argue why these already existing update processes do not cover our defiances. The objective of our software update protocol is to enable the developer to update many nodes in a reliable and very fast fashion during the development and testing process. For this reason, energy consumption is considered only marginally. We do not need a multi-hop protocol, due to the fact that all devices are in range, e.g. in a laboratory. In this paper we survey well known update protocols and architectures for software updates in WSN, discuss the solutions and compare them to our approach. As a conclusion of our extensive simulation follows to sum up that the developed protocols do a fast and scalable as well as a reliable update.
Introduction: Improving energy efficiency and reducing energy wastage is an important topic of our time. But it is quite difficult to figure out how much of our total electricity bill can be mapped to which device or at what time the device used it. We believe energy efficiency of normal households can be improved, if this kind of transparency would be available. In this article, we present a system for energy measurement at mains sockets to gain a transparent view of energy consumption for each device in a household. It consists of several smart energy measuring devices (SEMDs) that use a low-power radio protocol to dynamically build and connect to a radio network to transfer power usage date to a server. At the server, the data is stored and can be accessed via web interface.
Results: Our primary goal was to build a back-end system for an energy metering platform with very low energy consumption. This platform can provide data for a variety of services that enables users (the consumers) to understand and improve their energy consumption behavior and increase overall energy efficiency of their households.
In this paper we present a practical example of the use of Cellular Communication standards like GPRS and UMTS in a Smart Grid Application. For a more detailed view we demonstrate a possible implementation of Cellular Communication Technologies in a data acquisition application for the collection of energy indicators in a medium-voltage grid. Furthermore, we show a technical overview of relevant and common mobile communication standards available in Germany. The included theoretical examples, Smart Grid scenarios, presented data and results are based on a research project for intelligent power regulation in medium-voltage grids performed in Regensburg (Germany). It is a joint project' of the University of Applied Sciences Regensburg together with a local energy provider and a manufacturer for distribution network systems.
Smart grid, smart metering, electromobility, and the regulation of the power network are keywords of the transition in energy politics. In the future, the power grid will be smart. Based on different works, this article presents a data collection, analyzing, and monitoring software for a reference smart grid. We discuss two possible architectures for collecting data from energy analyzers and analyze their performance with respect to real-time monitoring, load peak analysis, and automated regulation of the power grid. In the first architecture, we analyze the latency, needed bandwidth, and scalability for collecting data over the Modbus TCP/IP protocol and in the second one over a RESTful web service. The analysis results show that the solution with Modbus is more scalable as the one with RESTful web service. However, the performance and scalability of both architectures are sufficient for our reference smart grid and use cases.
Smart Grid, Smart Metering, Electromobility and the regulation of the power network are keywords of the transition in energy policies. In the future, the power grid will be smart. Due to this the OTH Regensburg does research in this area based on different projects. This paper presents a data collection, analyzing and monitoring software for a reference Smart Grid. We discuss two possible architectures for collecting data from energy analyzers. The performance is analyzed with respect to real-time monitoring, analyzing load peaks and automated regulation of the power grid.
Fast and Reliable Update Protocols in WSNs During Software Development, Testing and Deployment
(2018)
A lot of research has been done in the area of Wireless Sensor Networks during the past years. Today, Wireless Sensor Networks are in field in many different ways and applications (e.g. energy management services, heat and water billing, smoke detectors). Nevertheless, research and development is continued in this area. After the network is deployed, software updates are performed very rarely, but during development and testing one typical, high frequented task is to deploy a new firmware to thousands of nodes. In this paper, we consider such a software update for a special, but well-known and frequently used sensor network platform. There exist some interesting research papers about updating sensor nodes, but we have a special focus on the technical update process. In this context, we show the reasons why these existing update processes do not cover our challenges. Our goal is to allow a developer to update thousands of nodes reliably and very fast during development and testing. Fo r this purpose, it is not so important to perform the best update with regard to energy consumption. We do not need a multi hop protocol, because all devices are in range, e.g., in a laboratory. In our work, we present a model of the update process and give very fast protocols to solve it. The results of our extensive simulations show that the developed protocols do a fast, scalable and reliable update.
We investigate the problem of path selection in radio networks for a given static set of n sites in two- and three-dimensional space. For static point-to-point communication we define measures for congestion, dilation, and energy consumption that take interferences among communication links into account. We show that energy-optimal path selection for radio networks can be computed in polynomial time. Then we introduce the diversity g(V) of a set V ⫅ ℝd for any constant d. It can be used to upper bound the number of interfering edges. For real-world applications it can be regarded as Θ(log n). A main result is that a c-spanner construction as a communication network allows one to approximate the congestion-optimal path system by a factor of O(g(V)2). Furthermore, we show that there are vertex sets where only one of the performance parameters congestion, dilation, and energy can be optimized at a time. We show trade-offs lower bounding congestion × dilation and dilation × energy. The trade-off between congestion and dilation increases with switching from two-dimensional to three-dimensional space. For congestion and energy the situation is even worse. It is only possible to find a reasonable approximation for either congestion or energy minimization, while the other parameter is at least a polynomial factor worse than in the optimal network.
In the context of a "Smart Grid" research project, together with industrial partners, the OTH-Regensburg realized an intelligent medium-voltage grid in the local area. Goal was to improve the current voltage regulation and to counter the problems with inconsistent energy feed-in of decentralized renewable energy producers. In this paper we discuss the possibilities of using 3rd generation (3G) cellular networks (UMTS) as basic technology to communicate the voltage-levels within a medium-voltage grid. We build an experimental
hardware setup to generate data-traffic as specified for the smart
grid. By analyzing the performance of 3G cellular networks in
terms of transmission latency and rate of failure, we tried to
evaluate the usability of this technology for such critical data
exchange. Though mobile communication in its structure is not
specified for the use of transmitting such infrastructure critical
data, the results show a promising high reliability with low
transmission latency. The experiments served just to test a
fragment of the conditions of use in a real scenario. An expanded
test scope is needed to further analyze the performance of mobile
radio for automatic control in smart grids. In the end the results
discussed in this paper led to a successful prototype of an
intelligent medium-voltage grid with mobile radio as communication technology
Considering the ongoing growth of Wireless Sensor Networks (WSNs) and the challenges they pose due to their hardware limitations as well as the intrinsic complexity of their interactions, specialized algorithms
have the potential to help solving these challenges. We present a survey on recent developments regarding algorithmic problems which have applications in wireless systems and WSNs in particular. Focusing on the intersection between WSNs and algorithms, we give an overview of recent results inside this intersection, concerning topics such as routing, interference minimization, latency reduction, localization among others. Progress on solving these problems could be potentially beneficial for the industry as a whole by increasing network throughput, reducing latency or making systems more energy-efficient. We summarize and structure these recent developments and list interesting open problems to be investigated in future works.