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Reliable Broadcast in Wireless Networks with Probabilistic Failures
 In Proceedings of the International Conference on Computer Communications (INFOCOM
, 2007
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Randomly Dutycycled Wireless Sensor Networks: Dynamics of Coverage
 IEEE Transactions on Wireless Communications
, 2006
"... Abstract — This paper studies wireless sensor networks that operate in low duty cycles, measured by the percentage of time a sensor is on or active. The dynamic change in topology as a result of such dutycycling has potentially disruptive effect on the performance of the network. We limit our atten ..."
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Abstract — This paper studies wireless sensor networks that operate in low duty cycles, measured by the percentage of time a sensor is on or active. The dynamic change in topology as a result of such dutycycling has potentially disruptive effect on the performance of the network. We limit our attention to a class of surveillance and monitoring applications and random dutycycling schemes, and analyze certain coverage property. Specifically, we consider coverage intensity defined as the probability distribution of durations within which a target or an event is uncovered/unmonitored. We derive this distribution using a semiMarkov model, constructed using the superposition of alternating renewal processes. We also present the asymptotic (as the number of sensors approaches infinity) distribution of the target uncovered duration when at least one sensor is required to cover the target, and provide an asymptotic lower bound when multiple sensors are required to cover the target. The analysis using the semiMarkov model serves as a tool with which we can find suitable random dutycycling schemes satisfying a given performance requirement. Our numerical observations show that the stochastic variation of dutycycling durations affects performance only when the number of sensors is small, whereas the stochastic mean of dutycycling durations impacts performance in all cases studied. We also show that there is a close relationship between coverage intensity and the measure of path availability, defined as the probability distribution of durations within which a path (of a fixed number of nodes) remains available. Thus the results presented here are readily applicable to the study of path availability in a low dutycycled sensor network. Index Terms — Energy conservation, microsensors, wireless sensor networks, coverage, connectivity, dutycycling, alternating
PERFORMANCE OF WIRELESS NETWORKS SUBJECT TO CONSTRAINTS AND FAILURES
, 2008
"... Recent years have seen a proliferation in the use of wireless multihop networks in diverse scenarios ranging from community mesh networks to wireless sensor networks. As wireless networks find application in such wideranging arenas and are deployed at large scale, they will increasingly need to op ..."
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Recent years have seen a proliferation in the use of wireless multihop networks in diverse scenarios ranging from community mesh networks to wireless sensor networks. As wireless networks find application in such wideranging arenas and are deployed at large scale, they will increasingly need to operate in the presence of heterogeneous, and often constrained, hardware capabilities. Furthermore, faulttolerant communication algorithms will be required to provide the building blocks for reliable operation in the face of failure and/or disruption. In this dissertation, we have investigated performance and faulttolerance issues in networks of such wireless devices. We have studied two specific problem domains, viz., throughput performance in multichannel wireless networks where devices have heterogeneous and constrained channel switching capabilities, and feasibility of faulttolerant broadcast in single channel wireless networks where devices can exhibit Byzantine or crashstop failure.
ASYMPTOTIC CONNECTIVITY OF LOW DUTYCYCLED WIRELESS SENSOR NETWORKS
"... In this paper we study the asymptotic connectivity of a low dutycycled wireless sensor network, where all sensors are randomly dutycycled such that they are on/active at any time with a fixed probability. A wireless network is often said to be asymptotically connected if there exists a path from e ..."
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In this paper we study the asymptotic connectivity of a low dutycycled wireless sensor network, where all sensors are randomly dutycycled such that they are on/active at any time with a fixed probability. A wireless network is often said to be asymptotically connected if there exists a path from every node to every other node in the network with high probability as the network density approaches infinity. Within the context of a low dutycycled wireless sensor network, the network is said to be asymptotically connected if for all realizations of the random dutycycling (i.e., the combination of on and off nodes) there exists a path of active nodes from every node to every other node in the network with high probability as the network density approaches infinity. With this definition, we derive conditions under which a low dutycycled sensor network is asymptotically connected. These conditions essentially specify how the nodes ’ communication range and the dutycycling probability should scale as the network grows in order to maintain connectivity. I.
Reliable Broadcast in Wireless . . .
, 2007
"... We consider the problem of reliable broadcast in a wireless network in which nodes are prone to failure. In the failure mode considered in this paper, each node can fail independently with probability p. Failures are permanent. The primary focus is on Byzantine failures, but we also handle crashsto ..."
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We consider the problem of reliable broadcast in a wireless network in which nodes are prone to failure. In the failure mode considered in this paper, each node can fail independently with probability p. Failures are permanent. The primary focus is on Byzantine failures, but we also handle crashstop failures. We consider two network models: a regular grid, and a random network. For the grid network model, we establish necessary and sufficient conditions for the degree of each node as a function of the total number of nodes n in the network, and the failure probability p, so as to ensure that reliable broadcast succeeds with probability 1, as n → ∞. Our necessary and sufficient conditions for reliable broadcast with Byzantine failures indicate that failure probability should be less than 1 � 2, and the critical node degree is Θ dmin + lnn ln 1 2p +ln � 1 (where dmin is the minimum node degree associated with a nonempty