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Code-division multiple-access (CDMA) is one of the major candidate access techniques for third generation systems, In recent years, 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

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In the recent technical literature on cellular networks Code Division Multiple Access (CDMA) has received a large attention as a promising radio interface access technique. Many studies are devoted to the capacity evaluation of the radio interface adopting CDMA, but seemingly none of them accounts for the variability of the user spatial density due to user mobility. This should be a concern especially in a microcellular environment, where it cannot be relied upon a significant spatial average over the radio coverage area of a Base Station. The major aim of this work is a preliminary assessment of the effects of ''bursty'' user mobility on the capacity of the CDMA radio interface. To this end, we introduce a user mobility model apt to describe large fluctuations of the number of users in a radio cell area. A reference model of a CDMA network is used to evaluate the effects of user mobility on the capacity for a wide range of the model parameters, by means of simulations accounting for shadowing, call attempt process, voice activity and antenna directivity and assuming perfect power control. We show that user mobility can remarkably affect the CDMA capacity, mainly because of the resulting highly bursty behaviour of self-noise. A simple traffic control scheme is devised to increase the capacity of the CDMA network, under a joint constraint on link availability, call blocking and call dropping probabilities. It is pointed out that the concepts introduced in this paper are independent of the specific CDMA implementation, i.e. they hold for any asynchronous CDMA based cellular network