PERFORMANCE ANALYSIS OF HETEROGENEOUS TRAFFIC ON AN INTEGRATED NETWORK LINK WITH FINITE WAITING ROOM AND ANTICIPATED-RELEASE RESERVATION POLICY

We consider a system where the superposition of two heterogeneous Poisson traffic streams is offered to an integrated network link in synchronous transfer mode, where one stream follows the blocked-and-cleared mode (‘loss’ mode) and the other can wait (finitely) if bandwidth is not available for connection at the time of arrival (‘hold’ mode). We assume that each stream has different bandwidth requirements per call. A reservation scheme, called anticipated-release policy, is introduced where an arrival is accepted into a waiting room only if the amount of time this customer is expected to wait is within acceptable limits. For such a loss/hold system, we provide analytical performance models for exponential service time distributions for both streams as well as for the non-exponential service time distribution case for the traffic stream in ‘hold’ mode. We also present a method on how to model the waiting time distribution of the traffic stream with ‘hold’ mode. From numerical studies, we observe that blocking can be reduced considerably for both services just by introducing a small waiting room for one traffic class compared to ‘loss’ mode for both traffic classes. Furthermore, this holds true for the case when a maximum tolerable time limit is imposed on the waiting. Finally, our results indicate that this loss/hold scenario with limited waiting room appears to be virtually insensitive to the service time distribution of the ‘hold’ mode traffic.     

Density variation and piezoelectric properties of Ba(Ti1 − x Sn x )O3 ceramics prepared from nanocrystalline powders

Nanocrystalline powders of tin-doped barium titanate with different concentrations of tin have been synthesized by a combination of solid state reaction and high-energy ball milling. The average particle size of the milled powders as determined from TEM analysis was about 5·96 nm. Analysis of all the milled powders using X-ray diffraction method showed single phase perovskite structure. The density variation of the ceramics with sintering temperature has been studied by sintering the samples at different temperatures. Density variation results show that 1350°C is the optimum sintering temperature for tin-doped barium titanate ceramics. SEM micrographs show high density and increasing trend of grain size with increasing content of Sn. The ferroelectricity decreases with increasing concentration of Sn. The electromechanical coupling coefficient also decreases with increasing Sn content corroborating decreasing trend of ferroelectricity. The bipolar strain curves show piezoelectric properties of the prepared ceramics.