We refer to the possible performance improvement consequent to the introduction of dynamic carrier allocation (DCA) strategies in the pan-European Global System for Mobile communications (GSM) cellular network. The impact of the introduction in a real network of two of the more promising DCA strategies is assessed, also in terms of the entailed signalling exchanges between base stations. A performance evaluation of a realistic cellular network exploiting the above-mentioned DCA strategies is carried out, taking into account all the main GSM transmission and network aspects. The simulations have been performed by considering a realistic cell layout corresponding to the urban area of Rome, its realistic propagation environment, and an user mobility model based on the building percentages in such area. The results of the performance evaluation show that, by carefully choosing the values of the parameters characterizing each of the considered DCA strategies, a conspicuous increase in the number of users supported by the cellular network can be achieved.

We refer to the implementation and the performance of a specific class of dynamic carrier allocation (DCA) strategies which is suitable for being introduced in the pan-European Global System for Mobile communications (GSM) cellular network. One of the main concerns of this work is to verify if and to what extent strategies belonging to this class can offer better performance than fixed channel allocation (FCA) in realistic traffic and propagation conditions. The impact of the introduction in a real network of two of the more promising DCA strategies in the considered class is assessed. In particular, solutions are presented concerning the signaling exchanges entailed by the implementation of each of the considered DCA strategies. A performance evaluation of a realistic cellular network exploiting the above-mentioned DCA strategies is carried out, taking into account all of the main GSM transmission and network aspects. The simulations have been performed by considering a realistic cell layout corresponding to the urban area of Rome, its realistic propagation environment, and a user mobility model based on the building percentages in such an area. The results of the performance evaluation show that, by carefully choosing the values of the parameters characterizing each of the considered DCA strategies, a conspicuous increase in the number of users supported by the cellular network can be achieved.

This paper describes the structure of a multicast asynchronous transfer mode (ATM) switching node employing a recursive copy generation algorithm, based on a self-routing network with a limited copying capability and a few added elements. With the network generates only a few copies a time of an input multicast cell, the remaining are obtained by recycling the output copies to the corresponding inputs as many times as necessary. The proposed recursive copy generation is also suitable to dynamically include new destinations and to delete old ones. The performance of the proposed structure, that has been implemented in a test-bed prototype, is also evaluated in terms of throughput and delay, via computer simulation, showing a possible performance improvement for multicast traffic with respect to an equivalent unicast input traffic. The cell loss probability in such structure is also evaluated.

Code-division multiple-access (CDMA) is one of the major candidate access techniques for third generation systems. A great deal of effort has been devoted to the study of the capacity it can support. This paper presents analytical derivations which allow the determination of the link availability in the presence of user mobility and power control imperfections in a CDMA network; moreover, it provides the guidelines which permit the implementation of a simple and flexible simulation tool which is independent of the specific CDMA implementations. As a matter of fact, the reported concepts can be applied to any asynchronous CDMA system, i.e., they hold both for the American Standard IS-95 and for the European Community Standard developed in the framework of the RACE CODIT Project.

In this paper an expression of the link availability in CDMA cellular networks which takes into account user mobility is determined. The performed simulations are based on this expression and on a simple but meaningful mobility which also considers hot cells where mobile users tend to accumulate. Two mechanisms for limiting the negative effects yielded by the bursty user mobility are presented. Such mechanisms aim at preventing the accumulation of a large amount of mobile users in a given cell, thus limiting the occurrence of situations in which the self-noise is so high that the target quality requirements are not met (i.e. the link is unavailable). The consequent increase in link availability takes place at the expense of the rising of non-null blocking and dropping probabilities. In this view, an optimization process is presented which achieves the maximum capacity while satisfying the given performance targets.

A recursive multistage structure for multicast asynchronous transfer mode (ATM) switching is proposed, based on a connection network with a copying facility and external links connecting the outlets to the inlets. While the network generates only a few copies of an output multicast cell, the remaining are obtained by recycling the output copied cells to the corresponding inputs as many times as necessary. The basic features of a prototype binary multicast switch following the strategy are described. Its performance is also evaluated in terms of throughput and delay, via computer simulation. It is shown that due to the recursive mechanism, the copy generation is spatially distributed in the whole structure and is spread in time. This favorably affects the network's performance.>