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Aleksandar Lebl, Dragan Mitić, Žarko Markov and Mihailo Stanić

Abstract

This paper considers two methods for voice channel seizure in one GSM cell, which uses VAMOS technics for traffic efficiency improvement. An important characteristic for models comparison is call loss caused by unsuccessful connection pairing in one timeslot. The first method gives priority to voice connection quality, and the other one to traffic efficiency. The methods are estimated by the simulation, which is first tested by comparing its results to the calculation results for a very small system. The influences of traffic intensity, allowed power difference of two paired connections and attenuation coefficient on the loss caused by unsuccessful pairing are assessed.

Open access

Aleksandar Lebl, Dragan Mitić, Žarko Markov and Željka Tomić

Abstract

In this paper it is presented the process of designing equi-interference lines in the CDMA mobile telephony systems. It is proved that shape of these lines in one base station cell is determined by emission characteristics of that base station and the base stations, which form the first ring around the considered cell. The influence of base stations from the other rings after the first one is dominantly noticed as the interference increase in each point of equi-interference line. The value of interference increase depends on the value of environmental propagation coefficient. For its small values it is necessary to consider the influence of base stations from more than twenty rings around the analyzed cell, while for great values it is enough to consider only two rings.

Open access

Staniša Lj. Perie, Dragan S. Antic, Vlastimir D. Nikolic, Darko B. Mitic, Marko T. Milojkovic and Šaša S. Nikolic

Abstract

In this paper we introduce a new approach to the sliding mode control design based on orthogonal models. First, we discuss the sliding mode control based on a model given in controllable canonical form. Then, we design almost orthogonal filters based on almost orthogonal polynomials of M¨untz-Legendre type. The advantage of the almost orthogonal filters is that they can be used for the modelling and analysis of systems with nonlinearities and imperfections. Herein, we use a designed filter to obtain several linearized models of an unknown system in different working areas. For each of these linearized models, corresponding sliding mode controller is designed and the switching between controls laws depends only on input signal. The experimental results and comparative analysis with relay control, already installed in laboratory equipment, verify the efficiency and excellent performance of such a control in the case of anti-lock braking system.

Open access

Dragan Mitić, Aleksandar Lebl, Mladen Mileusnić, Branimir Trenkić and Žarko Markov

Abstract

This paper presents simulation model for the analysis of characteristics of base station, which may establish half-rate connections. Accuracy of realized simulation model is analyzed comparing its results to a number of corresponding results, which are obtained by calculation or presented in referenced literature. These corresponding results are obtained, in the first case, analytically, solving the system of equations, which are modelling the system and, in the second case, from the literature, which deals with the similar systems. At the end, simulation model is implemented to analyze in detail several systems with different total number of traffic channels. The results of simulation pointed out how much probability of connection loss decreases in the case of great traffic load, when half-rate connections realization is implemented.

Open access

Aleksandar Lebl, Dragan Mitić, Miroslav Popović, Žarko Markov, Mladen Mileusnić and Vladimir Matić

Abstract

In this paper we analyze the influence of users’ density distribution in one cell of CDMA mobile network (ie adjusted power control on the forward link) on base station emission power. This influence is analyzed for different circles radii around base station within which same emission power is generated for all mobile users, and for different values of propagation loss coefficient. It is proved that emission power in this cell must be increased comparing to the similar cell, which uses complete power control. The power increase is greater when greater number of users are situated near base station, and for greater values of propagation loss coefficient. The results are presented, illustrated by numerical examples and verified by simulation for three users’ density distributions: uniform, decreasing and increasing density from the base station to the cell rim. The simulation process, which is based on random traffic process, is presented briefly.