T.L. Doumi

Teletraffic analysis and simulation for nongeostationary mobile satellite systems

The teletraffic performance parameters of a nongeostationary satellite system are estimated through analytical and simulation methods. In order to reduce the number of assumptions, the simulation tool that was developed emulates a mobile satellite system that is closer to the real thing. Parameters of interest include blocking, handover failure, noncompletion, and forced-termination probabilities. These are analyzed in terms of variations in satellite spot cells coverage, overlapping between cells, and in terms of a mobility factor. Additionally, the effect on the grade of service of different channel assignment strategies, for handover purposes, are investigated. The results show that the analytical work is in good agreement with the simulation outcome.

Teletraffic analysis and simulation of mobile satellite systems

The teletraffic performance parameters of a mobile radio network based on a non-geostationary satellite system are estimated through analytical and simulation methods. Parameters of interest include blocking, handover failure and non-completion probabilities. Effects of different handover channel assignment strategies upon the grade of service are investigated. Results will show that the estimated parameters are in good agreement with the simulation results.

Delay-spread considerations of same-frequency repeaters in wideband channels

In current analog cellular systems, same-frequency repeaters are very often used as gap fillers. With digital wideband systems, the use of a repeater, with its inherent group delay added to the differential propagation delay, may yield a degradation in the performance in view of the resulting delay spread. An approach to estimate the statistics of the delay spread when each link is subjected to lognormal shadowing and each channels power-delay profile follows an exponential decay is presented. Expressions for the cumulative density function (CDF), mean value, mean-square value, and standard deviation for the RMS delay spread are derived, and their accuracy is verified through simulation.

Delay spread statistics in a two-path radio environment

This article focuses on the statistics of the RMS delay spread in an area illuminated by two signal sources, transmitting identical data on the same frequency. The considered channel consists of two delta impulses, separated by a differential propagation delay, each of them subjected to Nakagami or log normal fading. Analytical expressions for the PDF, mean value and standard deviation of the delay spread are presented, and the effects of each type of fading are compared.

Teletraffic performance in indoor cordless communications with co-existing voice and data services

A simulation of the Digital European Cordless Telecommunications (DECT) system catering for voice and a variety of data services in a typical office environment has been undertaken to assess its teletraffic performance. The mixture of duplex connections employing distinct numbers of time slots per TDMA frame resulted in a poorer grade of service (GoS) for those services having a higher frame occupancy. Though, differences in GoS were significant at high traffic levels (in excess of 5 Erl/base) and when data services requests were a minority, ISDN and Fax services were found to be best served by the use of a single slot type through multibearer connections.<<ETX>>