114 research outputs found
On Mobility Management in Multi-Sink Sensor Networks for Geocasting of Queries
In order to efficiently deal with location dependent messages in multi-sink wireless sensor networks (WSNs), it is key that the network informs sinks what geographical area is covered by which sink. The sinks are then able to efficiently route messages which are only valid in particular regions of the deployment. In our previous work (see the 5th and 6th cited documents), we proposed a combined coverage area reporting and geographical routing protocol for location dependent messages, for example, queries that are injected by sinks. In this paper, we study the case where we have static sinks and mobile sensor nodes in the network. To provide up-to-date coverage areas to sinks, we focus on handling node mobility in the network. We discuss what is a better method for updating the routing structure (i.e., routing trees and coverage areas) to handle mobility efficiently: periodic global updates initiated from sinks or local updates triggered by mobile sensors. Simulation results show that local updating perform very well in terms of query delivery ratio. Local updating has a better scalability to increasing network size. It is also more energy efficient than ourpreviously proposed approach, where global updating in networks have medium mobility rate and speed
Design and evaluation of two geocast protocols for vehicular ad-hoc networks
Vehicular ad-hoc networks (VANETs) offer a large number of new potential applications. One of the envisioned applications is of course Internet access, which can be provided with the help of some roadside basestations. Many of the applications benefit from multi-hop relaying of information, thus requiring a routing protocol. Characteristics unique to VANETs (such as high mobility and the need for geographical addressing) make many conventional ad hoc routing protocols unsuitable. In this paper we design and evaluate two different, so called, geocast protocols for VANETs. One protocol is designed for fast communication across a large area. The purpose of the other protocol is to provide a routing service for a future reliable transport protocol (enabling Internet applications). We evaluate the performance of the protocols using realistic network and traffic models
A Distributed Routing Algorithm for Internet-wide Geocast
Geocast is the concept of sending data packets to nodes in a specified
geographical area instead of nodes with a specific address. To route geocast
messages to their destination we need a geographic routing algorithm that can
route packets efficiently to the devices inside the destination area. Our goal
is to design an algorithm that can deliver shortest path tree like forwarding
while relying purely on distributed data without central knowledge. In this
paper, we present two algorithms for geographic routing. One based purely on
distance vector data, and one more complicated algorithm based on path data. In
our evaluation, we show that our purely distance vector based algorithm can
come close to shortest path tree performance when a small number of routers are
present in the destination area. We also show that our path based algorithm can
come close to the performance of a shortest path tree in almost all geocast
situations
On Mobility Management in Multi-Sink Sensor Networks for Geocasting of Queries
In order to efficiently deal with location dependent messages in multi-sink wireless sensor networks (WSNs), it is key that the network informs sinks what geographical area is covered by which sink. The sinks are then able to efficiently route messages which are only valid in particular regions of the deployment. In our previous work (see the 5th and 6th cited documents), we proposed a combined coverage area reporting and geographical routing protocol for location dependent messages, for example, queries that are injected by sinks. In this paper, we study the case where we have static sinks and mobile sensor nodes in the network. To provide up-to-date coverage areas to sinks, we focus on handling node mobility in the network. We discuss what is a better method for updating the routing structure (i.e., routing trees and coverage areas) to handle mobility efficiently: periodic global updates initiated from sinks or local updates triggered by mobile sensors. Simulation results show that local updating perform very well in terms of query delivery ratio. Local updating has a better scalability to increasing network size. It is also more energy efficient than ourpreviously proposed approach, where global updating in networks have medium mobility rate and speed
Improving Geo-casting by Combining Any-cast and Hovering Information
Geocasting is a variation on the notion of multicasting in which messages are deliver to the nodes residing in a specific area. This paper proposed a novel geocast protocol based on any-cast and hovering information in order to improve the performance by balancing load between server and local nodes. Thus proposed technique has two phases for geocasting, 1) any-cast from source to geocast region and 2) distribution of messages using hovering information. Our results has shown that using hovering information and creating replicas for geocasting messages we can reduce the overhead of broadcasting messages several time that helps in reducing the bandwidth
Scalable wide area ad-hoc networking
The scalability problem of routing algorithms in Mobile Ad-hoc networks (MANET) has conventionally been addressed by introducing hierarchical architectures, clusters, and neighborhood zones. In all of these approaches, some nodes are assigned different routing related roles than others. Examples include cluster heads, virtual backbones and border nodes. The selection of these nodes on a fixed or dynamic basis adds complexity to the routing algorithm, in addition to placing significant demands on mobility and power consumption of these nodes. Furthermore, the scalability achieved with hierarchical architectures or partitions is limited.
This thesis demonstrates that location awareness can greatly aid in MANET routing and proposes an enhancement to location management algorithm used by the Terminodes System. This thesis makes use of geographic packet forwarding, geocasting and virtual home area concepts. It draws from the analogy between ad hoc networks and social networks. The Scalable Wide Area ad hoc network (SWAN), nodes update their location information with a geocast group whose area is given by a well-known function. A source node queries the geocast group of the destination and obtains up to date location information. Then, packets are geographically routed to the destination. The SWAN algorithm also optimizes the control overhead and obtains location information with minimal delay. This thesis also presents the results of our comparative performance study
Self-organizing Network Optimization via Placement of Additional Nodes
Das Hauptforschungsgebiet des Graduiertenkollegs "International Graduate
School on Mobile Communication" (GS Mobicom) der Technischen Universität
Ilmenau ist die Kommunikation in Katastrophenszenarien. Wegen eines
Desasters oder einer Katastrophe kĂśnnen die terrestrischen Elementen der
Infrastruktur eines Kommunikationsnetzwerks beschädigt oder komplett
zerstĂśrt werden. Dennoch spielen verfĂźgbare Kommunikationsnetze eine sehr
wichtige Rolle während der RettungsmaĂnahmen, besonders fĂźr die
Koordinierung der Rettungstruppen und fĂźr die Kommunikation zwischen ihren
Mitgliedern. Ein solcher Service kann durch ein mobiles Ad-Hoc-Netzwerk
(MANET) zur VerfĂźgung gestellt werden. Ein typisches Problem der MANETs
ist Netzwerkpartitionierung, welche zur Isolation von verschiedenen
Knotengruppen fĂźhrt. Eine mĂśgliche LĂśsung dieses Problems ist die
Positionierung von zusätzlichen Knoten, welche die Verbindung zwischen den
isolierten Partitionen wiederherstellen kĂśnnen. Hauptziele dieser Arbeit
sind die Recherche und die Entwicklung von Algorithmen und Methoden zur
Positionierung der zusätzlichen Knoten. Der Fokus der Recherche liegt auf
Untersuchung der verteilten Algorithmen zur Bestimmung der Positionen fĂźr
die zusätzlichen Knoten. Die verteilten Algorithmen benutzen nur die
Information, welche in einer lokalen Umgebung eines Knotens verfĂźgbar 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 Ăźber die Topologie des zu reparierenden Netzwerks im Voraus
erfasst werden und soll, natĂźrlich, fĂźr die Wiederherstellung mitbenutzt
werden. Dank der eventuell verfßgbaren zusätzlichen Information kÜnnen
die Positionen fßr die zusätzlichen Knoten genauer ermittelt werden. Die
Arbeit umfasst eine Beschreibung, Implementierungsdetails und eine
Evaluierung eines selbstorganisierendes Systems, welche die
Netzwerkwiederherstellung in beiden Szenarien ermĂśglicht.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
Supporting Protocols for Structuring and Intelligent Information Dissemination in Vehicular Ad Hoc Networks
The goal of this dissertation is the presentation of supporting protocols for structuring and intelligent data dissemination in vehicular ad hoc networks (VANETs). The protocols are intended to first introduce a structure in VANETs, and thus promote the spatial reuse of network resources. Segmenting a flat VANET in multiple cluster structures allows for more efficient use of the available bandwidth, which can effectively increase the capacity of the network. The cluster structures can also improve the scalability of the underlying communication protocols. The structuring and maintenance of the network introduces additional overhead. The aim is to provide a mechanism for creating stable cluster structures in VANETs, and to minimize this associated overhead. Further a hybrid overlay-based geocast protocol for VANETs is presented. The protocol utilizes a backbone overlay virtual infrastructure on top of the physical network to provide geocast support, which is crucial for intervehicle communications since many applications provide group-oriented and location-oriented services. The final contribution is a structureless information dissemination scheme which creates a layered view of road conditions with a diminishing resolution as the viewing distance increases. Namely, the scheme first provides a high-detail local view of a given vehicle\u27s neighbors and its immediate neighbors, which is further extended when information dissemination is employed. Each vehicle gets aggregated information for road conditions beyond this extended local view. The scheme allows for the preservation of unique reports within aggregated frames, such that safety critical notifications are kept in high detail, all for the benefit of the driver\u27s improved decision making during emergency scenarios
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