August 2007 - tr-announce - lists.rwth-aachen.de

2007-10: Bisimulation and Logical Preservation for Continuous-Time Markov Decision Processes
by Peter Schneider-Kamp 28 Aug '07

28 Aug '07

Bisimulation and Logical Preservation for Continuous-Time Markov Decision Processes Martin Neuhäußer, Joost-Pieter Katoen AIB 2007-10 This paper introduces strong bisimulation for continuous-time Markov decision processes (CTMDPs), a stochastic model which allows for a nondeterministic choice between exponential distributions, and shows that bisimulation preserves the validity of CSL. To that end, we interpret the semantics of CSL - a stochastic variant of CTL for continuous-time Markov chains - on CTMDPs and show its measure-theoretic soundness. The main challenge faced in this paper is the proof of logical preservation that is substantially based on measure theory.

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2007-15: Temporal assertions for sequential and current programs
by Peter Schneider-Kamp 15 Aug '07

15 Aug '07

The following technical report is available from http://aib.informatik.rwth-aachen.de: Temporal assertions for sequential and current programs Volker Stolz AIB 2007-15 In this thesis, we present an extension to the well-known concept of assertions: temporal assertions allow the specification and validation of modal safety properties of an application at runtime. We see this as a necessary step in enforcing the growing number of implicit requirements of software specifications, which are often only informally defined in the documentation of application program interfaces (API) and are beyond the reach of type checkers, compilers, or model checkers. Also, we show how our techniques can be applied to existing programs without modifying the source code. Although, like assertions, our approach cannot prove the absence of errors, it gives the programmer a more powerful means of automatically checking assumptions about his program at runtime.

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2007-16: Adaptive Channel Assignment to Support QoS and Load Balancing for Wireless Mesh Networks
by Peter Schneider-Kamp 07 Aug '07

07 Aug '07

The following technical report is available from http://aib.informatik.rwth-aachen.de: Adaptive Channel Assignment to Support QoS and Load Balancing for Wireless Mesh Networks Sadeq Ali Makram, Mesut Güneç, Martin Wenig, Alexander Zimmermann AIB 2007-16 One of the most promising wireless technologies are Wireless Mesh Networks (WMN). The aggregate capacity of wireless mesh networks can be improved significantly be equipping each node with several Wireless Network Interfaces (WNICs) and by using multiple channels in order to minimize the interference and to provide high performance in such networks. To achieve these benefits it requires a good channel assignment planning. The channels have to be assigned in such a way, that interference is decreased and performance is increased at the same time. Since the number of available channels is limited, it is desired to allocate and reallocate channels dynamically on-demand. In this paper, a dynamic channel assignment, is proposed to the aforementioned problem which is adaptive to the load in the wireless mesh network. The algorithm add or select a channel for those heavy loaded nodes, based on the local informations of the neighbor nodes. The selected or the added channel that minimizes the interference and insure the network connectivity. The simulation results show that our algorithm improve the network capacity by approximately 50% in comparison to a static channel assignment.

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