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Several multisatellite and multispot systems have been recently proposed for provision of mobile and personal services with global coverage, adopting GEO or non-GEO (i.e., MEO, LEO) satellite constellations. The paper addresses an in-depth analysis of these constellations, evaluating both geometrical performance measures and cochannel interference levels caused by extensive frequency reuse. The geometrical analysis yields the statistics for coverage, frequency of satellite hand-overs, and link absence periods. The interference analysis is based on a general model valid for all access techniques, which is here applied to the case of FDMA. The outage probability as a function of the specification on carrier-to-interference power ratio is evaluated for four selected constellations. Several techniques are introduced for interference reduction in non-GEO systems, in which the satellites coverage areas may intersect: spot turnoff, intraorbital plane frequency division, and interorbital plane frequency division. The effects of Rice fading have also been analyzed by means of an analytic approximated method. The overall analysis allows a fair comparison between LEO, MEO, and GEO constellations

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This paper addresses capacity estimation for cellular code-division multiple-access (CDMA) systems, assuming the IS-95 standard as a reference, Extending the analytical method from [6], we obtain a sequence of bounds on capacity, and then we introduce an accurate approximation to reduce computation complexity. The analysis accounts for interference internal and external to the reference cell, fading, shadowing, and imperfect power control. Outage probability is expressed in terms of the characteristic functions (cf's) of the interference and imperfect power control random variables (rv's), The interference contributions are computed on the basis of a Poisson distribution for the number of users in a lognormally shadowed channel. Results are provided for different channel conditions and are validated against Monte Carlo simulations, A comparison against previously published CDMA capacity estimates is carried out, aimed at clarifying some controversial issues. It is also confirmed that large system capacity is achievable under tight power control