A fuzzy control approach for adaptive traffic routing

The application of fuzzy control to adaptive traffic routing in telephone networks is investigated. The authors use, on one hand, the properties of fuzzy control techniques and adaptive routing, on the other hand, to derive a routing system that is robust and efficient. They analyze the impact of various availability indicators on performance, which indicates that the choice of a suitable indicator must be made to characterize circuit group availability. When used in the fuzzy control framework the indicator used appears clearly to improve the performance of the routing algorithm as compared to existing routing systems. On the other hand, the use of this indicator in a classical way appears to be of poor utility. The study compares the performance of methods usually applied to adaptive traffic routing and the fuzzy control approach and shows that the fuzzy control approach could provide an effective framework for robust control of traffic routing in communications networks. Research studies still need to be carried out to develop fuzzy adaptive routing on different network structures and to evaluate its impact on performance     

Kalman filtering of traffic fluctuations for real-time network management

Discrete- time stochastic models of sequential traffic records in telephone networks are considered. They appear to be well suited for a use of the Kaiman filter. A version of the filtering algorithm is adopted to deal with traffic fluctuations. The overall approach is tested against the real data gathered by the supervisor of the French toll network. The adaptive traffic estimator is inserted into a simulator of a testbed network operated in the urban zone of Paris. The traffic estimations provided by the filter are used to decide an overflow hierarchy.     

Towards formalising AADL in Proof Assistants

This paper presents first steps towards a formalisation of the Architecture Analysis and Design Language, mainly concentrating on a representation of its data model. For this, we contrast two approaches: one set-based (using the B modelling framework) and one in a higher-order logic (using the Isabelle proof assistant). We illustrate a transformation on a simplified part of the AADL metamodel concerning flows.     

Maximum a posteriori parameter estimation in large-scale systems

In this paper we examine the use of the maximum a posteriori (MAP) approach for parameter estimation in large-scale interconnected dynamical systems. We examine both the suboptimal approach of Sage and the optimal approaches which arise on solving within a multi-level structure the resulting nonlinear two point boundary value problem. In particular we consider two optimal methods i.e. the costate prediction method and the state estimation approach of Chen and Perlis as applied to parameter estimation. We illustrate the approaches on a simple example which is used as a bench mark problem for purposes of comparison of the numerical efficiency of the various techniques.     

Performance issues in the design of dynamically controlledcircuit-switched networks

The evolution of circuit-switched networks is analyzed with respect to the functional innovations that allowed for new traffic controls. The technical alternatives for routing techniques and their integration with congestion and flow control are considered. The performance of dynamically controlled networks is analyzed in the framework of research done at the Centre National d'Etudes des Telecommunications (CNET) together with studies carried out in other research laboratories. Comparisons are made of dynamic routing versus fixed hierarchical routing and time-dependent routing versus adaptive routing. For adaptive routing, centralized and isolated methods are compared. The benefits of advanced control methods are summarized     

Supporting network management with real-time traffic models

Real-time routing and flow control in circuit-switched networks is investigated. An algorithm which updates routing tables and flow-control parameters according to changing load conditions is derived. The network is described by means of stochastic difference equations. A control structure imposed by hardware requirements and realistic network status information patterns is considered. It is shown that the global objectives can be achieved by means of shortest-route algorithms with state-dependent route lengths. Implementation issues which are related to traffic estimation and prediction are discussed. The performance of a particular algorithm implementation is investigated by simulation     

Une maquette pour expérimenter I’acheminement adaptatif en France

This paper is concerned with the development of a system to test adaptive traffic routing in France. Presently, the switches are not provided with the facilities enabling the introduction of adaptive traffic routing in the telephone network. We are therefore developing a new system — star system — in order to provide the necessary functions to implement such a strategy for a field trial in the Paris area that could be experimented in the very near future. The main objective of the paper is to describe the star system and its operation within the network.