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A flexible radio resource utilization in W-CDMA systems, like UMTS, can be achieved using call admission control (CAC) schemes since the number of calls admitted can be adjusted according to interference conditions. Efficient CAC schemes proposed for the uplink direction take the acceptance decision estimating the effect of new call on the signal-to-interference ratio (SIR) of the already active calls. In order to reach this goal, predictive schemes measure the total received power at the base stations and estimate the interference increase due to the new call. In this paper we propose a new predictive scheme, iterative interference-increase estimation (I3E), and compare its performance with that of previously proposed schemes based on the estimation of the noise raise. We show that the traffic acceptable with the noise raise scheme is far from the upper capacity bound, while with our new scheme it can be increased remarkably and at the same time the call dropping probability can be kept very low.