Downlink capacity for WCDMA with soft and softer handover; advantages of unbalanced received powers

When studying the downlink of WCDMA radio systems, the trade-off between coverage and cell capacity is a critical aspect. In this work, a semi-analytical model is developed, considering the case of sectorized cells and taking soft and softer handover into account, which allows the investigation of the impact on downlink capacity of an unequal contribution of power coming from the base transceiver stations (BTSs) connected to the mobiles in soft (or softer) handover. A multi-service environment is investigated, in particular the case of mixed traffic scenarios. The results show the downlink capacity as a function of some interesting parameters, such as the cell radius, the number of bases in the users active sets, and the fraction of mobiles generating data traffic. It is shown that the system capacity can be maximized by selecting a proper unbalance between the contributions to the energy per bit over noise plus interference ratio, given by the different bases in the active set.