Turku Centre for Computer Science

About: Turku Centre for Computer Science is a facility organization based out in Turku, Finland. It is known for research contribution in the topics: Decidability & Word (group theory). The organization has 382 authors who have published 1027 publications receiving 19560 citations.

Some Undecidable Dynamical Properties for One-Dimensional Reversible Cellular Automata

Abstract: Using the fact that the tiling problem of Wang tiles is undecidable even if the given tile set is deterministic by two opposite corners, it is shown that the question whether there exists a trajectory which belongs to the given open and closed set is undecidable for one-dimensional reversible cellular automata This result holds even if the cellular automaton is mixing Furthermore, it is shown that left expansivity of a reversible cellular automaton is an undecidable property Also, the tile set construction gives yet another proof for the universality of one-dimensional reversible cellular automata

Distributed Spectrum Sensing Using Low Cost Hardware

Abstract: A distributed spectrum sensing network is prototyped using off the shelf hardware consisting of Raspberry Pi mini-computers and DVB-T receivers with software defined radio capabilities. Using the prototype network, coordinated, distributed wideband spectrum sensing is performed in a geographical area. The spectrum sensing data from the nodes is collected in a database. Well established low-complexity algorithms for distributed spectrum sensing are applied, and the results are compared against a professional spectrum sensing system. We show that with this simple low-cost setup, the decisions made on the availability of spectrum using the distributed sensing data correspond well with the decisions made on the reference data.

The Equivalence Problem of Finite Substitutions on ab*c, with Applications

Abstract: We show that it is undecidable whether or not two finite substitutions are equivalent on the fixed regular language ab*c. This gives an unexpected answer to a question proposed in 1985 by Culik II and Karhumaki. At the same time it can be seen as the final result in a series of undecidability results for finite transducers initiated in 1968 by Griffiths. An application to systems of equations over finite languages is given.

Partitioning methods for unicast/multicast traffic in 3D NoC architecture

Abstract: As the scale of integration grows, the interconnection problem becomes one of the major design considerations of Multi Processor System on Chip (MPSoC). In recent years, many researchers have conducted studies on 3D IC designs stacking multiple layers on top of each other. In order to decrease the transmission delay of unicast/multicast messages in a network based multicore system, the network is divided into several partitions. In this paper, we first introduce a novel idea of balanced partitioning that allows the network to be partitioned effectively. Then, we propose a set of partitioning approaches each with a different level of efficiency. In addition, we present an advantageous method based on the idea of balanced partitioning to provide a high degree of parallelism with a considerable reduction of packet delay in unicast/multicast traffic. Simulations are provided to evaluate and compare the performance of proposed methods.

The Production Cell: an exercise in the formal verification of a UML model

Abstract: We show how to model the Production Cell, a standard example for evaluating design notations for embedded systems, using the Unified Modelling Language (UML). Then, we use the vUML tool, developed by the authors, to verify our model of the Production Cell. The input model and the results from the verification are expressed using the UML notation, thus hiding the model checking formalism from the user. We also show how to use the object oriented decomposition of the model, that is given by a UML class diagram, to reduce the complexity of the model checking problem. We conclude that the vUML tool helps the designer to verify the software of distributed object oriented embedded systems, without learning all the details of a model checker.