Bozena Wozna-Szczesniak

The BMC method for the existential part of RTCTLK and interleaved interpreted systems

In the paper, we focus on the formal verification of multi-agent systems - modelled by interleaved interpreted systems - by means of the bounded model checking (BMC) method, where specifications are expressed in the existential fragment of the Real-Time Computation Tree Logic augmented to include standard epistemic operators (RTECTLK). In particular, we define an improved SAT-based BMC for RTECTLK, and present performance evaluation of our newly developed BMC method by means of the well known train controller and generic pipeline systems.

Adapted and constrained Dijkstra for elastic optical networks

We present an optimal and efficient algorithm for finding a shortest path in an elastic optical network. The algorithm is an adaptation of the Dijkstra shortest path algorithm, where we take into account the spectrum continuity and contiguity constraints, and a limit on the path length. The adaptation redefines the node label in the Dijkstra algorithm, allows for revisiting nodes even at a higher cost for different slices, avoids loops, and prunes worse labels. The algorithm is generic and agnostic of a specific spectrum allocation policy, as it finds the largest set of available slices from which slices can be allocated in any way. We describe and motivate the algorithm design, and point to our freely-available implementation using the Boost Graph Library. We carried out 8100 simulation runs for large, random and realistic networks, and found that the probability of establishing a connection using the proposed algorithm can be even twice as large as the probability of establishing a connection using the edge-disjoint shortest paths, and the Yen K shortest paths.

Interoperator fixed-mobile network sharing

We propose the novel idea of interoperator fixed-mobile network sharing, which can be software-defined and readily-deployed. We study the benefits which the sharing brings in terms of resiliency, and show that, with the appropriate placement of a few active nodes, the mean service downtime can be reduced more than threefold by providing interoperator communication to as little as one optical network unit in one hundred. The implementation of the proposed idea can be carried out in stages when needed (the pay-as-you-grow deployment), and in those parts of the network where high service availability is needed most, e.g., in a business district. While the performance should expectedly increase, we show the resiliency is brought almost out of thin air by using redundant resources of different operators. We evaluated the service availability for 87400 networks with the relative standard error of the sample mean below 1%.