IMDEA Networks Institute Digital Repository
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Brief Announcement: Node Sampling Using Centrifugal Random Walks
Get PDFWe propose distributed algorithms for sampling networks based on a new class of random walks that we call Centrifugal Random Walks (CRW). A CRW is a random walk that starts at a source and alwaysmoves away from it. We propose CRW algorithms for connected networks with arbitrary probability distributions, and for grids and networks with regular concentric connectivity with distance based distributions. All CRW sampling algorithms select a node with the exact probability distribution, do not need warm-up, and end in a number of hops bounded by the network diameter.TRUEpu
An architecture for collaborative driving systems
No full textE-ISBN: 978-1-4673-2446-5
Print ISBN:978-1-4673-2445-8
INSPEC Accession Number:13309796Vehicle automation has progressed from systems that monitor the operation of a vehicle and assist a driver, with functions such as antilock braking and cruise control, to systems that detect the operation of adjacent vehicles, to implement emergency braking and intelligent cruise control. The next generation of systems will share sensor readings and collaborate to control braking operations by looking several cars ahead or by creating safe gaps for merging vehicles. The rules that control the interaction between automobiles are protocols.TRUEpu
Opportunistic cellular communications with clusters of dual-radio mobiles
Get PDF“Premio Extraordinario de Máster Oficial Universidad Carlos III de Madrid – Curso 2011/2012. Programa de Máster Interuniversitario en Ingeniería Telemática.” Masters thesis defended on October 3rd, 2012, in Madrid, Spain. The prize was awarded on December 18th, 2012.Opportunistic scheduling was initially proposed to exploit user channel diversity for network capacity enhancement. However, the achievable gain of opportunistic schedulers is generally restrained due to fairness considerations which impose a tradeoff between fairness and throughput. In this dissertation, we show via analysis and simulation that opportunistic scheduling not only increases network throughput dramatically, but also can be fair to the users when they cooperate, in particular by forming clusters. We propose to leverage smartphone’s dual-radio interface capabilities to form clusters among mobile users, and we design simple and scalable cluster-based opportunistic scheduling strategies which would incentivize mobile users to form clusters. We use a coalitional game theory approach to analyze the cluster formation mechanism, and show that proportional fair-based intra-cluster payoff distribution would bring significant incentive to all mobile users regardless of their channel quality.Telematics EngineeringUniversidad Carlos III de Madrid, Spainpu
A Model of Self-Avoiding Random Walks for Searching Complex Networks
Get PDFRandom walks have been proven useful in several applications in networks. Some variants of the basic random walk have been devised pursuing a suitable trade-off between better performance and limited cost. A self-avoiding random walk (SAW) is one that tries not to revisit nodes, therefore covering the network faster than a random walk. Suggested as a network search mechanism, the performance of the SAW has been analyzed using essentially empirical studies.
A strict analytical approach is hard since, unlike the random walk, the SAW is not a Markovian stochastic process. We propose an analytical model to estimate the average search length of a SAW when used to locate a resource in a network. The model considers single or multiple in stances of the resource sought and the possible availability of one-hop replication in the network (nodes know about resources held by their neighbors). The model characterize networks by their size and degree distribution, without assuming a particular topology. It is, therefore, a mean-field model, whose applicability to real networks is validated by simulation. Experiments with sets of randomly built regular networks, Erd ̋s–R ́nyi networks, and scale-free networks of several of several sizes and degree averages, with and without one-hop replication, show that model predictions are very close to simulation results, and allow us to draw conclusions about the applicability of
SAWs to network search.TRUEpu
Deterministic recurrent communication in restricted Sensor Networks
Get PDFIn Sensor Networks, the lack of topology information and the availability of only one communication channel has led research work to the use of randomization to deal with collisions of transmissions. However, the scarcest resource in this setting is the energy supply, and radio communication dominates the sensor node energy consumption. Hence, redundant trials of transmission as used in randomized protocols may be counter-effective. Additionally, most of the research work in Sensor Networks is either heuristic or includes unrealistic assumptions. Hence, provable results for many basic problems still remain to be given. In this paper, we study upper and lower bounds for deterministic communication primitives under the harsh constraints of sensor nodes.TRUEpu
IPv6 address autoconfiguration in geonetworking-enabled VANETs: characterization and evaluation of the ETSI solution
Get PDFIn this article we make a thorough characterization and evaluation of the solution standardized by the European Telecommunications Standards Institute for IPv6 transmission of packets over geographical location aware vehicular networks. In particular, we focus on IPv6 address auto-configuration, one of the required pieces to enable Internet connectivity from vehicles. Communications in vehicular networks are strongly dependent on the availability of multi-hop connectivity to the fixed infrastructure, so also we analyze the probability of achieving this connectivity under different circumstances, and we use the results to identify interesting target scenarios for address auto-configuration mechanisms. Keeping those scenarios in mind, we perform a characterization and deep evaluation---analytically and by means of simulations---of the standardized IPv6 address autoconfiguration solution; proposing some configuration guidelines and highlighting the scenarios where complementary enhancements might be needed.TRUEpu
A History of an Internet eXchange Point
Get PDFIn spite of the tremendous amount of measurement efforts on understanding the Internet as a global system, little is known about the `local' Internet (among ISPs inside a region or a country) due to limitations of the existing measurement tools and scarce data. In this paper, empirical in nature, we characterize the evolution of one such ecosystem of local ISPs by studying the interactions between ISPs happening at the Slovak Internet eXchange (SIX). By crawling the web archive ww.waybackmachine.org we collect 158 snapshots (spanning 14 years) of the SIX website, with the relevant data that allows us to study the dynamics of the Slovak ISPs in terms of: the local ISP peering, the traffic distribution, the port capacity/utilization and the local AS-level traffic matrix. Examining our data revealed a number of invariant and dynamic properties of the studied ecosystem that we report in detail.TRUEpu
The NAT64/DNS64 tool suite for IPv6 transition
Get PDFIt is clear that there is not enough time to upgrade existing Internet hosts to dual stack before the IPv4 address pool depletes. This implies that the IPv6 transition and co-existence must support interaction between IPv4 nodes and IPv6 nodes. In this article we describe NAT64 and DNS64, a tool suite that provides a way forward in the IPv4-to-IPv6 transition by allowing communication among unmodified IPv6 and IPv4 nodes.TRUEpu
