Stavros Athanassopoulos

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We present new combinatorial approximation algorithms for k-set cover. Previous approaches are based on extending the greedy algorithm by efficiently handling small sets. The new algorithms further extend them by utilizing the natural idea of computing large packings of elements into sets of large size. Our results improve the previously best approximation(More)
We present a simple algorithm for the maximum spanning star forest problem. We take advantage of the fact that the problem is a special case of complementary set cover and we adapt an algorithm of Duh and Fürer in order to solve it. We prove that this algorithm computes 193/240 ≈ 0.804-approximate spanning star forests; this result improves a previous lower(More)
Energy is a scarce resource in ad hoc wireless networks and it is of paramount importance to use it efficiently when establishing communication patterns. In this work we study algorithms for computing energy-efficient multicast trees in ad hoc wireless networks. Such algorithms either start with an empty solution which is gradually augmented to a multicast(More)
We study communication problems in wireless networks supporting multiple interfaces. In such networks, two nodes can communicate if they are close enough and share a common interface. The activation of each interface has a cost reflecting the energy consumed when a node uses this interface. We distinguish between the homogeneous and heterogeneous case,(More)
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