This article proposes a method that can calculate the blocking probability of multi-service cellular systems with Wideband Code Division Multiple Access radio interface. The method considers a finite and an infinite source population and takes into account the interdependency of calls service processes in neighboring cells and in both the uplink and the downlink directions. The basis of the proposed method is the fixed-point methodology. A comparison of the results of analytical calculations to those of simulations confirms the accuracy of the proposed method. The proposed scheme can realize cost-effective radio resource management in 3G mobile networks and can be easily applied to network capacity calculations.