57 research outputs found
Energy-efficient region shift scheme to support mobile sink group in wireless sensor networks
© 2017 by the authors. Licensee MDPI, Basel, Switzerland. Mobile sink groups play crucial roles to perform their own missions in many wireless sensor network (WSN) applications. In order to support mobility of such sink groups, it is important to design a mechanism for effective discovery of the group in motion. However, earlier studies obtain group region information by periodic query. For that reason, the mechanism leads to significant signaling overhead due to frequent flooding for the query regardless of the group movement. Furthermore, the mechanism worsens the problem by the flooding in the whole expected area. To deal with this problem, we propose a novel mobile sink group support scheme with low communication cost, called Region-Shift-based Mobile Geocasting Protocol (RSMGP). In this study, we utilize the group mobility feature for which members of a group have joint motion patterns. Thus, we could trace group movement by shifting the region as much as partial members move out of the previous region. Furthermore, the region acquisition is only performed at the moment by just deviated members without collaboration of all members. Experimental results validate the improved signaling overhead of our study compared to the previous studies
Self-organizing Network Optimization via Placement of Additional Nodes
Das Hauptforschungsgebiet des Graduiertenkollegs "International Graduate
School on Mobile Communication" (GS Mobicom) der Technischen UniversitÀt
Ilmenau ist die Kommunikation in Katastrophenszenarien. Wegen eines
Desasters oder einer Katastrophe können die terrestrischen Elementen der
Infrastruktur eines Kommunikationsnetzwerks beschÀdigt oder komplett
zerstört werden. Dennoch spielen verfĂŒgbare Kommunikationsnetze eine sehr
wichtige Rolle wĂ€hrend der RettungsmaĂnahmen, besonders fĂŒr die
Koordinierung der Rettungstruppen und fĂŒr die Kommunikation zwischen ihren
Mitgliedern. Ein solcher Service kann durch ein mobiles Ad-Hoc-Netzwerk
(MANET) zur VerfĂŒgung gestellt werden. Ein typisches Problem der MANETs
ist Netzwerkpartitionierung, welche zur Isolation von verschiedenen
Knotengruppen fĂŒhrt. Eine mögliche Lösung dieses Problems ist die
Positionierung von zusÀtzlichen Knoten, welche die Verbindung zwischen den
isolierten Partitionen wiederherstellen können. Hauptziele dieser Arbeit
sind die Recherche und die Entwicklung von Algorithmen und Methoden zur
Positionierung der zusÀtzlichen Knoten. Der Fokus der Recherche liegt auf
Untersuchung der verteilten Algorithmen zur Bestimmung der Positionen fĂŒr
die zusÀtzlichen Knoten. Die verteilten Algorithmen benutzen nur die
Information, welche in einer lokalen Umgebung eines Knotens verfĂŒgbar ist,
und dadurch entsteht ein selbstorganisierendes System. Jedoch wird das
gesamte Netzwerk hier vor allem innerhalb eines ganz speziellen Szenarios -
Katastrophenszenario - betrachtet. In einer solchen Situation kann die
Information ĂŒber die Topologie des zu reparierenden Netzwerks im Voraus
erfasst werden und soll, natĂŒrlich, fĂŒr die Wiederherstellung mitbenutzt
werden. Dank der eventuell verfĂŒgbaren zusĂ€tzlichen Information können
die Positionen fĂŒr die zusĂ€tzlichen Knoten genauer ermittelt werden. Die
Arbeit umfasst eine Beschreibung, Implementierungsdetails und eine
Evaluierung eines selbstorganisierendes Systems, welche die
Netzwerkwiederherstellung in beiden Szenarien ermöglicht.The main research area of the International Graduate School on Mobile
Communication (GS Mobicom) at Ilmenau University of Technology is
communication in disaster scenarios. Due to a disaster or an accident, the
network infrastructure can be damaged or even completely destroyed.
However, available communication networks play a vital role during the
rescue activities especially for the coordination of the rescue teams and
for the communication between their members. Such a communication service
can be provided by a Mobile Ad-Hoc Network (MANET). One of the typical
problems of a MANET is network partitioning, when separate groups of nodes
become isolated from each other. One possible solution for this problem is
the placement of additional nodes in order to reconstruct the communication
links between isolated network partitions. The primary goal of this work is
the research and development of algorithms and methods for the placement of
additional nodes. The focus of this research lies on the investigation of
distributed algorithms for the placement of additional nodes, which use
only the information from the nodesâ local environment and thus form a
self-organizing system. However, during the usage specifics of the system
in a disaster scenario, global information about the topology of the
network to be recovered can be known or collected in advance. In this case,
it is of course reasonable to use this information in order to calculate
the placement positions more precisely. The work provides the description,
the implementation details and the evaluation of a self-organizing system
which is able to recover from network partitioning in both situations
Analysis and application of hop count in multi-hop wireless ad-hoc networks
Hop count, i.e., the number of wireless hops a packet has to go through to reach the destination, is a fundamental metric in multi-hop wireless ad-hoc networks. Network performance, such as throughput, end-to-end delay, energy consumption, and so on, depends critically on hop count. Previous work on modeling hop count is limited in making unrealistic simplifying assumptions either at the physical or network, or both layers of the communication protocol stack. A key contribution of this thesis is to present an analytical model to derive the probability distribution of hop count under realistic assumptions at both physical and network layers. Specifically, the model considers a log-normal shadowing radio propagation capable of accommodating the random signal fading observed in most wireless communication environments, and the widely used geographic routing at the network layer. Validation of the model is achieved by a comprehensive set of simulation experiments including a trace driven simulation of a real-word vehicular ad-hoc network. The model reveals that the presence of randomness in radio propagation reduces the required number of hops to reach a given destination significantly. To demonstrate the utility of the proposed hop count model, the thesis proposes three new applications which address some of the key challenges in multi-hop wireless networks. The first application derives the per-node packet forwarding load in multi-hop wireless sensor networks and reveals that the nodes in the vicinity of the base station has a significantly less forwarding load than previously thought under simplifying radio propagation and routing assumptions. The second application demonstrates that using hop count as a measure of distance traveled by a data packet, geocasting can be achieved in multi-hop wireless networks in situations when some of the network nodes do not have access to reliable location information. Finally, the proposed hop count model is used to evaluate the performance of the third application which demonstrates that the overhead of geographic routing can be reduced significantly by embracing a position update philosophy which adapts to the mobility and communication patterns of the underlying ad-hoc network
Location based multicast routing algorithms for wireless sensor networks
Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2007.Thesis (Master's) -- Bilkent University, 2007.Includes bibliographical references leaves 54-56Multicast routing protocols in wireless sensor networks are required for sending
the same message to multiple different destination nodes. Since most of the
time it is not convenient to identify the sensors in a network by a unique id,
using the location information to identify the nodes and sending messages to the
target locations seems to be a better approach. In this thesis we propose two
different distributed algorithms for multicast routing in wireless sensor networks
which make use of location information of sensor nodes. Our first algorithm
groups the destination nodes according to their angular positions and sends a
message toward each group in order to reduce the number of total branches
in multicast tree which also reduces the number of messages transmitted. Our
second algorithm calculates an Euclidean minimum spanning tree at the source
node by using the positions of the target nodes. According to the calculated
MST, multicast message is forwarded to destination nodes. This helps reducing
the total energy consumed for delivering the message to all target nodes since it
tries to minimize the number of transmissions. We compare these two algorithms
with each other and also against another location based multicast routing protocol
called PBM according to success ratio in delivery, number of total transmissions,
traffic overhead and average end to end delay metrics. The results show that
algorithms we propose are more scalable and energy efficient, so they are good
candidates to be used for multicasting in wireless sensor networks.BaÄcı, HakkıM.S
Dynamic Time-Stable Geocast Routing in Vehicular Ad Hoc Networks
Vehicular ad hoc networks (VANETs) have emerged as an area of interest for both industry and research scholars because they have become an essential part of intelligent transportation systems (ITSs). Many applications in VANET require sending a message to certain or all vehicles within a region, called geocast. Sometimes geocast requires that the message be kept alive within the region for a period of time. This time-stable geocast has a vital role in some ITS applications, particularly commercial applications. This study presents a novel time-stable geocast protocol that works well even in too sparse networks. Moreover, since commercial applications sometimes make it necessary to change the duration of the stable message within the region, the dynamic nature of a geocast protocol should allow this time to be extended, reduced, or canceled without any additional cost. Therefore, we call it a dynamic time-stable geocast, DTSG, protocol. It works in two phases (the pre-stable period and the stable period), and the simulation results show that it works well in its performance metrics (delivery ratio and network cost). In addition, these results validate the protocol prediction of its performance metrics. Moreover, with the informed time of zero, all the intended vehicles will be informed as soon as they enter the region. The fact that the protocol is independent of the networksâ density, the vehiclesâ speed, and the vehiclesâ broadcasting range, makes it more robust than others that fail in sparse networks or in high-speed nodes
Transport mechanism for wireless micro sensor network
Wireless sensor network (WSN) is a wireless ad hoc network that consists of very large number of tiny sensor nodes communicating with each other with limited power and memory constrain. WSN demands real-time routing which requires messages to be delivered within their end-to-end deadlines (packet lifetime). This report proposes a novel real-time with load distribution (RTLD) routing protocol that provides real time data transfer and efficient distributed energy usage in WSN. The RTLD routing protocol ensures high packet throughput with minimized packet overhead and prolongs the lifetime of WSN. The routing depends on optimal forwarding (OF) decision that takes into account of the link quality, packet delay time and the remaining power of next hop sensor nodes. RTLD routing protocol possesses built-in security measure. The random selection of next hop node using location aided routing and multi-path forwarding contributes to built-in security measure. RTLD routing protocol in WSN has been successfully studied and verified through simulation and real test bed implementation. The performance of RTLD routing in WSN has been compared with the baseline real-time routing protocol. The simulation results show that RTLD experiences less than 150 ms packet delay to forward a packet through 10 hops. It increases the delivery ratio up to 7 % and decreases power consumption down to 15% in unicast forwarding when compared to the baseline routing protocol. However, multi-path forwarding in RTLD increases the delivery ratio up to 20%. In addition, RTLD routing spreads out and balances the forwarding load among sensor nodes towards the destination and thus prolongs the lifetime of WSN by 16% compared to the baseline protocol. The real test bed experiences only slight differences of about 7.5% lower delivery ratio compared to the simulation. The test bed confirms that RTLD routing protocol can be used in many WSN applications including disasters fighting, forest fire detection and volcanic eruption detection
Routing Protocols in Wireless Sensor Networks
The applications of wireless sensor networks comprise a wide variety of scenarios. In most of them, the network is composed of a significant number of nodes deployed in an extensive area in which not all nodes are directly connected. Then, the data exchange is supported by multihop communications. Routing protocols are in charge of discovering and maintaining the routes in the network. However, the appropriateness of a particular routing protocol mainly depends on the capabilities of the nodes and on the application requirements. This paper presents a review of the main routing protocols proposed for wireless sensor networks. Additionally, the paper includes the efforts carried out by Spanish universities on developing optimization techniques in the area of routing protocols for wireless sensor networks
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