WCDMA downlink coverage: interference margin for users located at the cell coverage border

The scope of this paper is to derive a simple equation for the WCDMA downlink interference margin as a function of the relative downlink load. This interference margin can then be used as an input for a typical link budget. Due to the complexity of the WCDMA downlink, a fully analytical approach would probably result in a rather complicated and/or inaccurate approximation. Therefore, in this paper the actual equation for the interference margin is derived from the WCDMA theory, and the missing parameter values are obtained from a number of system simulations. The downside of this approach is that a fully flexible usage of the approximated interference margin requires input from a number of measurements or system simulations with different initial assumptions.