Analysis of soft handover margin in downlink WCDMA system

The focus of the paper is to analyze the downlink performance of a wideband code division multiple access (WCDMA) system with site selection diversity transmission (SSDT) power control during soft handover (SHO) mode and to find the optimum SHO margin (M_SH) in terms of maximum system capacity under energy-per-bit to noise spectral density ratio (E_b/N_o) quality requirements. Analyzing the dependency of the connection probabilities, percentage of users connected to one, two, or three base stations (BSs) simultaneously as a function of the M_SH. The result of this analysis shows an increase in user capacity of about 16% - 20% for the optimum M_SH of 5-5.5 dB. Nevertheless, the resources required (number of scrambling codes) by the base station increases faster than the number of active users in terms of M_SH.