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DROiD: Adapting to Individual Mobility Pays Off in Mobile Data Offloading
"... IFIP, (2014). This is the author’s version of the work. It is posted here by permission of IFIP for your personal use. Not for redistribution. The definitive version was published in IFIP Networking 2014. Abstract—Cellular operators count on the potentials of offloading techniques to relieve their ..."
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IFIP, (2014). This is the author’s version of the work. It is posted here by permission of IFIP for your personal use. Not for redistribution. The definitive version was published in IFIP Networking 2014. Abstract—Cellular operators count on the potentials of offloading techniques to relieve their overloaded data channels. Beyond standard access pointbased offloading strategies, a promising alternative is to exploit opportunistic direct communication links between mobile devices. Nevertheless, achieving efficient devicetodevice offloading is challenging, as communication opportunities are, by nature, dependent on individual mobility patterns. We propose, design, and evaluate DROiD (Derivative Reinjection to Offload Data), an original method to finely control the distribution of popular contents throughout a mobile network. The idea is to use the infrastructure resources as seldom as possible. To this end, DROiD injects copies through the infrastructure only when needed: (i) at the beginning, in order to trigger the dissemination, (ii) if the evolution of the opportunistic dissemination is below some expected pace, and (iii) when the delivery delay is about to expire, in order to guarantee 100 % diffusion. Our strategy is particularly effective in highly dynamic scenarios, where sudden creation and dissolution of clusters of mobile nodes prevent contents to diffuse properly. We assess the performance of DROiD by simulating a traffic information service on a realistic largescale vehicular dataset composed of more than 10,000 nodes. DROiD substantially outperforms other offloading strategies, saving more than 50 % of the infrastructure traffic even in the case of tight delivery delay constraints. DROiD allows terminaltoterminal offloading of data with very short maximum reception delay, in the order of minutes, which is a realistic bound for cellular user acceptance. Index Terms—Mobile data offloading; hybrid networks; delaytolerant networks. I.
Algorithms for Channel Assignment in Mobile Wireless Networks using Temporal Coloring ∗
"... We model the problem of channel assignment in mobile networks as one of temporal coloring (Tcoloring), that is, coloring a timevarying graph. In order to capture the impact of channel reassignments due to mobility, we model the cost of coloring as C + αA, where C is the total number of colors used ..."
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We model the problem of channel assignment in mobile networks as one of temporal coloring (Tcoloring), that is, coloring a timevarying graph. In order to capture the impact of channel reassignments due to mobility, we model the cost of coloring as C + αA, where C is the total number of colors used and A is the total number of color changes, and α is a userselectable parameter reflecting the relative penalty of channel usage and reassignments. Using these models, we present several novel algorithms for temporal coloring. We begin by analyzing two simple algorithms called SNAP and SMASH that take diametrically opposite positions on colors vs reassignments, and provide theoretical results on the ranges of α in which one outperforms the other, both for arbitrary and random timevarying graphs. We then present six more algorithms that build upon each of SNAP and SMASH in different ways. Simulations on random geometric graphs with random waypoint mobility show that the relative cost of the algorithms depends upon the value of α and the transmission range, and we identify precise values at which the crossovers happen.
Monitoring UserSystem Interactions through GraphBased Intrinsic Dynamics Analysis
, 2013
"... Abstract—Monitoring the evolution of usersystem interactions is of high importance for complex systems and for information systems in particular, especially to raise alerts automatically when abnormal behaviors occur. However current methods fail at capturing the intrinsic dynamics of the system, a ..."
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Abstract—Monitoring the evolution of usersystem interactions is of high importance for complex systems and for information systems in particular, especially to raise alerts automatically when abnormal behaviors occur. However current methods fail at capturing the intrinsic dynamics of the system, and focus on evolution due to exogenous factors like daynight patterns. In order to capture the intrinsic dynamics of usersystem interactions, we propose an innovative graphbased approach relying on a novel concept of time. We apply our method on two large realworld systems (the Github.com social network and the eDonkey peertopeer system) to automatically detect statistically significant events in a realtime fashion. We finally validate our results with the successful interpretation of the detected events.
Topology Control for TimeVarying Contested Environments
"... Abstract—This work considers a problem of topology design and control when some of the links may become unavailable. When a network operates in a contested environment, the operator may wish to alter the network topology to enhance robustness. This may come at the expense of operational costs. We co ..."
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Abstract—This work considers a problem of topology design and control when some of the links may become unavailable. When a network operates in a contested environment, the operator may wish to alter the network topology to enhance robustness. This may come at the expense of operational costs. We consider a dynamic programming framework where the goal is to minimize time average costs, where costs are the sum of network properties (e.g. eccentricity), edit costs and maintenance costs. We consider practical lowcomplexity control algorithms which focus on instantaneous network states. We particularly introduce a modified myopic policy which attempts to reduce average cost by benefiting future costs. We also provide decision rules for different algorithms and characterize expected costs for random hostility models. Our numerical results demonstrate that our modified myopic scheduler outperform other schedulers in terms of average sum cost for various settings. I.
Temporal Connectivity of Vehicular Networks: The Power of StoreCarryandForward
"... Abstract—Storecarryandforward is extensively used in vehicular environments for many and varied purposes, including routing, disseminating, downloading, uploading, or offloading delaytolerant content. The performance gain of storecarryandforward over traditional connected forwarding is prima ..."
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Abstract—Storecarryandforward is extensively used in vehicular environments for many and varied purposes, including routing, disseminating, downloading, uploading, or offloading delaytolerant content. The performance gain of storecarryandforward over traditional connected forwarding is primarily determined by the fact that it grants a much improved network connectivity. Indeed, by letting vehicles physically carry data, storecarryandforward adds a temporal dimension to the (typically fragmented) instantaneous network topology that is employed by connected forwarding. Temporal connectivity has thus a important role in the operation of a wide range of vehicular network protocols. Still, our understanding of the dynamics of the temporal connectivity of vehicular networks is extremely limited. In this paper, we shed light on this underrated aspect of vehicular networking, by exploring a vast space of scenarios through an evolving graphtheoretical approach. Our results show that using storecarryandforward greatly increases connectivity, especially in very sparse networks. Moreover, using storecarryandforward mechanisms to share content within a geographicallybounded area can be very efficient, i.e., new entering vehicles can be reached rapidly. I.
Analysis of Hop Limit in Opportunistic Networks by Static and TimeAggregated Graphs
"... Abstract—Hop count limitation helps controlling the spread of messages as well as the protocol complexity and overhead in a distributed network. For a mobile opportunistic network, we examine how the paths between any two nodes change with increasing number of hops a message can follow. Using the al ..."
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Abstract—Hop count limitation helps controlling the spread of messages as well as the protocol complexity and overhead in a distributed network. For a mobile opportunistic network, we examine how the paths between any two nodes change with increasing number of hops a message can follow. Using the all hops optimal path (AHOP) problem, we represent the total delay of a route from a source node to a destination node as additive weight and use the number of encounters as a representation of bottleneck weight. First, we construct a static (contact) graph from the meetings recorded in a human contact trace and then analyze the change in these two weights with increasing hop count. Alternatively, we aggregate all the contact events in a time interval and construct several timeaggregated graphs over which we calculate the capacity metrics. Although, we observe differences in the properties of the static and the timeaggregated graphs (e.g., higher connectivity and average degree in static graph), our analysis shows that second hop brings most of the benefits of multihop routing for the studied networks. However, the optimal paths —path that provides the most desirable bottleneck/additive weight — are achieved at further hops, e.g, hop count ≈ 4. Our finding, which is also verified by simulations, is paramount as it puts an upper bound on the hop count for the hoplimited routing schemes by discovering the optimal hop count for both additive and bottleneck weights. I.
Change Awareness in Opportunistic Networks
"... Abstract—Information latency and information reachability are widely used metrics for measuring information flow in Opportunistic Networks. We present an alternative measure that looks at the amount of information updates or changes from a given sender, which is an important and yet relatively unexp ..."
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Abstract—Information latency and information reachability are widely used metrics for measuring information flow in Opportunistic Networks. We present an alternative measure that looks at the amount of information updates or changes from a given sender, which is an important and yet relatively unexplored metric for characterizing opportunistic networks. In this paper, we propose a novel concept to measure information freshness — how much the latest information received differs from the most uptodate information on the sender. Based on information freshness, awareness on how information propagated may have changed, or change awareness, can be computed. Change awareness can be exploited to design efficient algorithms, in particular, data aggregation algorithms. Evaluation on real world traces shows that change awareness based solutions can achieve similar results as data aggregation algorithm with a connection oracle. Index Terms—Opportunistic Network; message freshness; data aggregation. I.
Towards A Redefinition of Time in Information Networks?
, 2013
"... How should we characterize the dynamics of the Web? Whereas network maps have contributed to a redefinition of distances and space in information networks, current studies still use a traditional time unitthe second to understand the temporality of the Web. This unit leads to the observation of ex ..."
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How should we characterize the dynamics of the Web? Whereas network maps have contributed to a redefinition of distances and space in information networks, current studies still use a traditional time unitthe second to understand the temporality of the Web. This unit leads to the observation of exogenous phenomena like daynight patterns. In order to capture the intrinsic dynamics of the network, we introduce an innovativeyet simple concept of time which relies on the measure of changes in the network space. We demonstrate its practical interest on the evolution of the Github social network. Author Keywords Time; dynamics; measurement; complex networks; social network; sliding window. ACM Classification Keywords