Performance of diversity handover in DS-CDMA cellular systems

Diversity handover (DHO), which can reduce the transmit power and interference through the site diversity effect, is essential for high capacity DS-CDMA cellular systems. System capacity depends on how diversity handover is applied. This paper describes reverse and forward link system capacity for several typical handover schemes under transmit power control (TPC) based on SIR as determined by computer simulations. First, both link system capacities are shown under perfect TPC. These results give an ideal upper limit of capacity. We examine the increase in system capacity achieved by maximal-ratio-combining (MRC) and sectorization. Next, we consider TPC error, which leads to more realistic capacity values. This shows that system capacity with DHO is larger than with hard handover (HHO) in both links. Especially with MRC-DHO in the forward link, there is an optimum threshold for DHO that maximizes the capacity.