Capacity analysis in downlink WCDMA systems using soft handover techniques with SIR-based power control and site selection diversity transmission

This paper analyzes the downlink performance of a wideband code-division multiple-access system with site selection diversity transmission power control during soft handover (SHO) mode. Signal-to-interference ratio power control techniques are modeled and used in the simulations of this analysis. The study is focused on finding the optimum SHO margin in terms of maximum system capacity under energy-per-bit to noise spectral density ratio (E_b/N₀ ) quality requirements. The results of this analysis show an increase in user capacity of about 15%-20% for optimum SHO margins of 5-5.5 dB. Nevertheless, the resources required (number of scrambling codes) by the base station increase faster than the number of active users in terms of SHO margin up to values of approximately 9.5 dB