Harri Haanpää

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A family of satisfiable benchmark instances in conjunctive normal form is introduced. The instances are constructed by transforming a random regular graph into a system of linear equations followed by clausification. Schemes for introducing nonlinearity to the instances are developed, making the instances suitable for benchmarking solvers with equivalence(More)
A subset S of a finite Abelian group G is said to be a sum cover of G if every element of G can be expressed as the sum of two not necessarily distinct elements in S, a strict sum cover of G if every element of G can be expressed as the sum of two distinct elements in S, and a difference cover of G if every element of G can be expressed as the difference of(More)
We approach the problem of load balancing for wireless multi-hop networks by distributed optimisation. We implement an approximation algorithm for minimising the maximum network congestion as a modification to the DSR routing protocol. The algorithm is based on shortest-path computations that are integrated into the DSR route discovery and maintenance(More)
A subset S = {s1; : : : ; s k } of an abelian group G is called an St-set of size k if all sums of t diierent elements in S are distinct. A function with applications in coding theory, v(k) denotes the order of the smallest cyclic group in which an S2-set of size k exists. A lower bound for v(k) is given in this study, and exact values of v(k) are obtained(More)
We consider the problem of balancing the traffic load ideally over a wireless multihop network. In previous work, a systematic approach to this task was undertaken, starting with an approximate op-timisation method that guarantees a provable congestion performance bound, and then designing a distributed implementation by modifying the DSR protocol. In this(More)
A v-player whist tournament is a schedule of games, where in each round the v players are partitioned into games of four players each with at most one player left over. In each game two of the players play as partners against the other two. All pairs of players must play in the same game exactly three times during the tournament; of those three times, they(More)
A v-player whist tournament Wh(v) is a schedule of games, each involving two players opposing two others. Every round, the players are partitioned into games, with at most one player left over. Each player partners every other player exactly once and opposes every other player exactly twice during the tournament. Directed whist tournaments DWh(v), and(More)
We present a simple and efficient distributed method for determining the transmission power assignment that maximises the lifetime of a data-gathering wireless sensor network with stationary nodes and static power assignments. Our algorithm determines the transmission power level inducing the maximum-lifetime spanning subgraph of a network by means of a(More)
We consider the problem of static transmission-power assignment for lifetime maximization of a wireless sensor network with stationary nodes operating in a data-gathering scenario. Using a graph-theoretic approach, we propose two distributed algorithms, MLS and BSPAN, that construct spanning trees with minimum maximum (min-max) edge cost. MLS is based on(More)