An Analytic Approximation of the Uplink Capacity in a UMTS Network with Heterogeneous Traffic

The fast computation of blocking probabilities and the resulting capacity is one of the crucial tasks in the planning process of UMTS networks. The admission control in WCDMA networks bases on the momentary interference which includes both own-cell and other-cell interference. Since both interference terms are stochastic values we speak of soft blocking. The number of users in the system is not sufficient for deciding whether to accept a new call or not. Instead, it is blocked with a certain probability depending on the number of users in the system, the activity of the users, and the other cell interference. In this paper we present a time efficient algorithm to compute blocking probabilities in a WCDMA network operating with several services. Assuming Bernoulli activity and modelling the other cell interference as a lognormal random variable the blocking probabilities are computed using an approximation based on the Kaufman-Roberts recursion.