Head of Laboratory – Dr.Sc. (Technology) Sergei Stepanov

Tel.: (095) 299-94-15; E-mail: stepanov@iitp.ru

The leading researchers of the laboratory include:

The laboratory deals with the development of teletraffic theory and its applications in telecommunications and computer systems. The following problem areas and models are studied at the laboratory in 1999.

• the construction of numerically optimized algorithms of calculation the performance measures of queueing models described by multi-dimensional Markovian processes.
• the development and analysis of teletraffic models for performance evaluation of new cost-effective telecommunication systems.
• the development of the software tools based on the efficient algorithms to support the performance modelling of the teletraffic models.
• the construction of the asymptotically optimal procedures for the sequential design of experiments for statistical problems related to telecommunication networks.
• the analysis of switching systems and interconnection networks for telecommunication and multiprocessing systems.

An algorithm of optimal calculation of stationary performance measures of Markov models with retrials is suggested. The proposed method is based on the concept of truncated state space that is obtained after preliminary estimation and ignoring in the process of calculation the states with negligible probabilities. Formulae for determination of the error caused by using the truncated state space are presented together with an algorithm for estimation of the borders of the truncated state space providing given relative error of performance measures calculation. Suggested approach gives a great reduction of computer resources in estimating the performance measures of models with retrials (S. N. Stepanov.)

The model operated as a full availability system with a some number of Poisson input processes each having it's own availability and possibility of fixed number of retrials in case of blocking is considered. An approach of estimation the performance measures of this system is suggested. Presented algorithm can be generalized to the case of a state-dependent and multi-slot Poisson traffic processes. (S. N. Stepanov, E. O. Naumova, M. Yu. Zozulinskiy.)

Estimating of the second term of asymptotical expansion for the optimal sequential design of hypothesizes testing with guaranteeing decision was investigated. The true order of this term for robust sequential tests with asymptotically small error's probabilities was found. (I. I. Tsitovich.)

Preliminary investigation of microcell structure of subscriber's radioaccess was done. (A. D. Charkevich.)

Communication systems with additional paths are investigated. The using of additional paths gives the possibility to achieve the property of fault-tolerant of the constructed system. (V. A. Garmash.)

The investigation of robustness of characteristics of radiotechnical devices to the accuracy of input parameters is done. Our results show that the loaded reactive filter circuits of stair structure (RFSS) with negative components are well-conditioned. This fact have been earlier known for RFSS-circuit with positive inductances and capacitances. (A. A. Vitkova.)

The upper and lower error bounds for blocking probabilities of new calls at wireless communication networks under fixed channel allocation were derived. The comparison of blocking probabilities with corresponding measures of approximated model with product form solution was made. (O. V. Ivnitski.)

An explicit formulae for finding the stationary probabilities of models described by markov processes with special type of block structure is found. This result can be used both for models with finite and infinite number of states. (V. A. Naoumov.)