Stavros Athanassopoulos

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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)
We present new combinatorial approximation algorithms for the k-set cover problem. Previous approaches are based on extending the greedy algorithm by efficiently handling small sets. The new algorithms further extend these approaches by utilizing the natural idea of computing large packings of elements into sets of large size. Our results improve the(More)
We use cellular automata for simulating a series of topology control algorithms in Wireless Sensor Networks (WSNs) using various programming environments. A cellular automaton is a decentralized computing model providing an excellent platform for performing complex computations using only local information. WSNs are composed of a large number of distributed(More)
We use cellular automata for simulating topology control algorithms in Wireless Sensor Networks (WSNs). A cellular automaton is a decentralized computing model providing an excellent platform for performing complex computations using only local information. WSNs are composed of a large number of distributed sensor nodes operating on batteries; the objective(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)
We use cellular automata for simulating topology control algorithms in wireless sensor networks (WSNs) using the Matlab programming environment. Our objective has been to provide experimental evidence in order to (i) investigate whether potential researchers who lack sound programming skills but would like to promptly implement their ideas with confidence(More)
The “small world” phenomenon, i.e., the fact that the global social network is strongly connected in the sense that every two persons are inter-related through a small chain of friends, has attracted research attention and has been strongly related to the results of the social psychologist's Stanley Milgram experiments; properties of social(More)
This paper presents a series of implementations of cellular automata rules using the Matlab programming environment. A cellular automaton is a decentralized computing model providing an excellent platform for performing complex computations with the help of only local information. Matlab is a numerical interactive computing environment and a high-level(More)
Interference is an issue of outstanding importance for efficient communication in ad-hoc wireless networks. Interference arises due to overlapping transmission power levels of nodes and causes message collisions that require energy-consuming retransmissions. In this work we study algorithms for interference control in ad-hoc wireless networks in the(More)