439 research outputs found
A taxonomic Approach to Topology Control in Ad-hoc and Wireless Networks
Topology Control (TC) aims at tuning the topology of highly dynamic networks
to provide better control over network resources and to increase the efficiency
of communication. Recently, many TC protocols have been proposed. The protocols
are designed for preserving connectivity, minimizing energy consumption,
maximizing the overall network coverage or network capacity. Each TC protocol
makes different assumptions about the network topology, environment detection
resources, and control capacities. This circumstance makes it extremely
difficult to comprehend the role and purpose of each protocol. To tackle this
situation, a taxonomy for TC protocols is presented throughout this paper.
Additionally, some TC protocols are classified based upon this taxonomy.Comment: The Sixth International Conference on Networking, ICN 200
Using OLSR Multipoint Relays (MPRs) to estimate node positions in a Wireless Mesh Network
In this paper we address in this paper the problem of nodes localization in wireless heterogeneous networks, focussing particularly on selection methods to estimate position. The OLSR routing protocol uses special nodes called Multipoint Relay (MPR) nodes to broadcast control messages within the network. We propose a novel approach based on using these Multipoint Relay (MPR) nodes as anchor nodes to estimate nodes positions. We evaluate its performance by simulation and compare it to other selection techniques such as convex hull selection and greedy selection
Asynchronous Local Construction of Bounded-Degree Network Topologies Using Only Neighborhood Information
We consider ad-hoc networks consisting of wireless nodes that are located
on the plane. Any two given nodes are called neighbors if they are located
within a certain distance (communication range) from one another. A given node
can be directly connected to any one of its neighbors and picks its connections
according to a unique topology control algorithm that is available at every
node. Given that each node knows only the indices (unique identification
numbers) of its one- and two-hop neighbors, we identify an algorithm that
preserves connectivity and can operate without the need of any synchronization
among nodes. Moreover, the algorithm results in a sparse graph with at most
edges and a maximum node degree of . Existing algorithms with the same
promises further require neighbor distance and/or direction information at each
node. We also evaluate the performance of our algorithm for random networks. In
this case, our algorithm provides an asymptotically connected network with
edges with a degree less than or equal to for fraction
of the nodes. We also introduce another asynchronous connectivity-preserving
algorithm that can provide an upper bound as well as a lower bound on node
degrees.Comment: To appear in IEEE Transactions on Communication
Localized and Configurable Topology Control in Lossy Wireless Sensor Networks
Recent empirical studies revealed that multi-hop wireless networks like wireless sensor networks and 802.11 mesh networks are inherently lossy. This finding introduces important new challenges for topology control. Existing topology control schemes often aim at maintaining network connectivity that cannot guarantee satisfactory path quality and communication performance when underlying links are lossy. In this paper, we present a localized algorithm, called Configurable Topology Control (CTC), that can configure a network topology to different provable quality levels (quantified by worst-case dilation bounds in terms of expected total number of transmisssions) required by applications. Each node running CTC computes its transmission power solely based on the link quality information collected within its local neighborhood and does not assume that the neighbor locations or communication ranges are known. Our simulations based on a realistic radio model of Mica2 motes show that CTC yields configurable communication performance and outperforms existing topology control algorithms that do not account for lossy links
Design and performance evaluation of smart dissemination of emergence messages in vehicular ad-hoc networks
The growing demand to improve road safety and optimize road traffic has generated great interest in vehicular ad-hoc network (VANETs). Serious traffic accidents can cause financial losses, physical disability, and even death.
However, if drivers were informed about the danger in advance through a warning message, this would give drivers enough time to react appropriately to the situation. There are many approaches that can prevent car accidents, and VANETs have been conceived as an excellent solution to improve road safety, through the use of a variety of applications enabled by vehicle communications. The key objective of this research is to achieve information dissemination from a vehicle to other vehicles around that migth be interested in receiving the content. We focus on the network layer and application layer protocols, which are discussed and developed as a protocol over the respective access technologies. We primarily present the research results of our proposals, and also provide a comprehensive review of existing challenges and solutions in data dissemination in VANETs. Our proposals include the design of three dissemination protocols compatible with the IEEE 802.11p standards for road safety applications. These dissemination protocols can be differentiated by their application trigger condition and the broadcast scheme. All three dissemination protocols have been implemented in the simulator
VEINS to perform several large-scale experiments. The results of the experiments have shown that all three dissemination protocols are able to cope with an increasing number of vehicles in large scale scenarios without sufering a noticeable loss in performance. Finally, we have investigated solutions to increase the driver's privacy because VANETs can also introduce
some location privacy risk by periodically broadcast beacon messages that include the vehicle's position. We evaluate the performance of the privacy schemes, described the experiments and discussed the results.La creixent demanda per millorar la seguretat vià ria i optimitzar el trà nsit viari ha generat gran interès en les xarxes vehiculars ad-hoc (VANETs). Els accidents de trà nsit greus poden causar pèrdues financeres, discapacitat fÃsica i fins i tot la mort. No obstant això, si els conductors van ser informats per endavant sobre el perill a través d’un missatge d’advertència, això donaria als conductors el temps suficient per reaccionar de manera apropiada a la situació. Hi ha molts enfocaments que poden prevenir accidents automobilÃstics, i les VANETs s’han concebut com una excel·lent solució per millorar la seguretat vià ria, a través de l’ús d’una varietat d’aplicacions habilitades per les comunicacions vehiculars. L’objectiu principal d’aquesta investigació és aconseguir la disseminació de la informació des d’un vehicle a altres vehicles que estiguin interessats en rebre el contingut. Ens enfoquem en la capa de xarxa i els protocols de capa d’aplicació, que es discuteixen i desenvolupen com un protocol sobre les respectives tecnologies d'accés. Principalment vam presentar els resultats d’investigació de les nostres propostes, i també provem una revisió exhaustiva dels desafiaments i solucions existents en la disseminació de dades en les VANETs. Les nostres propostes inclouen el disseny de tres protocols de disseminació compatibles amb els està ndards IEEE 802.11p per a aplicacions de seguretat vià ria. Aquests protocols de disseminació es poden diferenciar per la condició d’activació de l’aplicació i l’esquema de difusió. Els tres protocols de disseminació s’han implementat en el simulador VEINS per a realitzar diversos experiments a gran escala. Els resultats dels experiments han demostrat que els tres protocols de disseminació són capaços de fer front a un nombre creixent de vehicles en escenaris de gran escala sense patir una pèrdua notable en el rendiment. Finalment, hem investigat solucions per augmentar la privacitat del conductor perquè les VANETs també poden introduir algun risc de privacitat de la ubicació mitjanant missatges beacon emesos periòdicament que inclouen la posició dels vehicles. Avaluem l’acompliment dels esquemes de privacitat, descrivim els experiments i discutim els resultats.Postprint (published version
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