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Wireless sensor networks (WSNs) are emerging as an effective means for environment monitoring. This paper investigates a strategy for energy efficient monitoring in WSNs that partitions the sensors into covers, and then activates the covers iteratively in a round-robin fashion. This approach takes advantage of the overlap created when many sensors monitor a(More)
We introduce a concept of network decomposition, a partitioning of an arbitrary graph into small-diameter connected components, such that the graph created by contracting each component into a single node has low chromatic number and low arboricity. We present an eecient distributed algorithm for constructing such a decomposition, and demonstrate its use(More)
We present the COST-DISTANCE problem: finding a Steiner tree which optimizes the sum of edge costs along one metric and the sum of source-sink distances along an unrelated second metric. We give the first known £ ¥ ¤ § ¦ © ¨ randomized approximation scheme for COST-DISTANCE, where is the number of sources. We reduce several common network design problems to(More)
We consider a generalization of the maximum flow problem in which the amounts of flow entering and leaving an arc are linearly related. More precisely, if x(e) units of flow enter an arc e, x(e)γ(e) units arrive at the other end. For instance, nodes of the graph can correspond to different currencies, with the multipliers being the exchange rates. We(More)
All previously known algorithms for solving the multicommodity flow problem with capacities are based on linear programming. The best of these algorithms [14] uses a fast matrix multiplication algorithm and takes O(k25n2m5 log(nDU)) time to find an approximate solution, where k is the number of commodities, n and m denote the number of nodes and edges in(More)
We consider a class of network design problems in which one needs to nd a minimum-cost network satisfying certain connectivity requirements. For example, in the sur-vivable network design problem, the requirements specify that there should be at least r(v; w) edge-disjoint paths between each pair of vertices v and w. We present an approximation algorithm(More)
1 Introduction In this paper we introduce the notion of the limited-depth minor exclusion and show that graphs that exclude small limited-depth minors have relatively small separators. In particular, we prove that for any graph that excludes Kh as a depth 1 minor, we can find a separator of size 0(/h' logn + n/l). This, in turn, implies that any graph that(More)
In this paper we consider the steiner multicut problem. This is a generalization of the minimum multicut problem where instead of separating node pairs, the goal is to find a minimum weight set of edges that separates all given sets of nodes. A set is considered separated if it is not contained in a single connected component. We show an O(log 3 (kt))(More)
We describe efficient deterministic techniques for breaking symmetry in parallel. The techniques work well on rooted trees and graphs of constant degree or genus. Our primary technique allows us to 3-color a rooted tree in <italic>&Ogr;</italic>(lg<supscrpt>*</supscrpt><italic>n</italic>) time on an EREW PRAM using a linear number of processors. We apply(More)