580,535 research outputs found
Channels with Cooperation Links that May Be Absent
It is well known that cooperation between users in a communication network
can lead to significant performance gains. A common assumption in past works is
that all the users are aware of the resources available for cooperation, and
know exactly to what extent these resources can be used. Unfortunately, in many
modern communication networks the availability of cooperation links cannot be
guaranteed a priori, due to the dynamic nature of the network. In this work a
family of models is suggested where the cooperation links may or may not be
present. Coding schemes are devised that exploit the cooperation links if they
are present, and can still operate (although at reduced rates) if cooperation
is not possible.Comment: Accepted for publication in the IEEE transaction on Information
Theory, June 201
Dynamic resiliency analysis of key predistribution in wireless sensor networks
Wireless sensor networks have been analyzed for more than a decade from operational and security points of view. Several key predistribution schemes have been proposed in the literature. Although valuable and state-of-the-art proposals have been made, their corresponding security analyses have not been performed by considering the dynamic nature of networking behavior and the time dimension. The sole metric used for resiliency analysis of key predistribution schemes is "fraction of links compromised" which is roughly defined as the ratio of secure communication links that the adversary can compromise over all secure links. However, this metric does not consider the dynamic nature of the network; it just analyzes a snapshot of the network without considering the time dimension. For example, possible dead nodes may cause change of routes and some captured links become useless for the attacker as time goes by. Moreover, an attacker cannot perform sensor node capturing at once, but performs over time. That is why a methodology for dynamic security analysis is needed in order to analyze the change of resiliency in time a more realistic way. In this paper, we propose such a dynamic approach to measure the resiliency of key predistribution schemes in sensor networks. We take the time dimension into account with a new performance metric, "captured message fraction". This metric is defined as the percentage of the messages generated within the network to be forwarded to the base station (sink) that are captured and read by the attacker. Our results show that for the cases where the static fraction of links compromised metric indicates approximately 40% of the links are compromised, our proposed captured message fraction metric shows 80% of the messages are captured by the attacker. This clearly proves the limitations of the static resiliency analysis in the literature
Renormalization group theory for percolation in time-varying networks
Motivated by multi-hop communication in unreliable wireless networks, we
present a percolation theory for time-varying networks. We develop a
renormalization group theory for a prototypical network on a regular grid,
where individual links switch stochastically between active and inactive
states. The question whether a given source node can communicate with a
destination node along paths of active links is equivalent to a percolation
problem. Our theory maps the temporal existence of multi-hop paths on an
effective two-state Markov process. We show analytically how this Markov
process converges towards a memory-less Bernoulli process as the hop distance
between source and destination node increases. Our work extends classical
percolation theory to the dynamic case and elucidates temporal correlations of
message losses. Quantification of temporal correlations has implications for
the design of wireless communication and control protocols, e.g. in
cyber-physical systems such as self-organized swarms of drones or smart traffic
networks.Comment: 8 pages, 3 figure
Distributed Queuing in Dynamic Networks
We consider the problem of forming a distributed queue in the adversarial
dynamic network model of Kuhn, Lynch, and Oshman (STOC 2010) in which the
network topology changes from round to round but the network stays connected.
This is a synchronous model in which network nodes are assumed to be fixed, the
communication links for each round are chosen by an adversary, and nodes do not
know who their neighbors are for the current round before they broadcast their
messages. Queue requests may arrive over rounds at arbitrary nodes and the goal
is to eventually enqueue them in a distributed queue. We present two algorithms
that give a total distributed ordering of queue requests in this model. We
measure the performance of our algorithms through round complexity, which is
the total number of rounds needed to solve the distributed queuing problem. We
show that in 1-interval connected graphs, where the communication links change
arbitrarily between every round, it is possible to solve the distributed
queueing problem in O(nk) rounds using O(log n) size messages, where n is the
number of nodes in the network and k <= n is the number of queue requests.
Further, we show that for more stable graphs, e.g. T-interval connected graphs
where the communication links change in every T rounds, the distributed queuing
problem can be solved in O(n+ (nk/min(alpha,T))) rounds using the same O(log n)
size messages, where alpha > 0 is the concurrency level parameter that captures
the minimum number of active queue requests in the system in any round. These
results hold in any arbitrary (sequential, one-shot concurrent, or dynamic)
arrival of k queue requests in the system. Moreover, our algorithms ensure
correctness in the sense that each queue request is eventually enqueued in the
distributed queue after it is issued and each queue request is enqueued exactly
once. We also provide an impossibility result for this distributed queuing
problem in this model. To the best of our knowledge, these are the first
solutions to the distributed queuing problem in adversarial dynamic networks.Comment: In Proceedings FOMC 2013, arXiv:1310.459
Stochastic Stability in Network with Decay
This paper considers a simple communication network characterized by an endogenous architecture and an imperfect transmission of information. We analyze the process of network formation in a dynamic framework where self – interested individuals can form or delete links and, occasionally, are doing mistakes. Then, using stochastic stability, we identify which network structures the formation process will converge to.Network, Decay, Strategical interaction
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