Enhanced soft handover algorithms for UMTS system

In this paper, we propose novel soft handover algorithms for unbalanced traffic loads in a CDMA based cellular radio system. Cell traffic load is taken into account as one of the criteria for making soft handover decisions. The term traffic indicator is introduced for producing adaptive adding or dropping thresholds according to the cell load. Different possible schemes of forming adaptive threshold based algorithms have been investigated. The simulations are performed in the UMTS vehicular testing environment. The results have been compared to that of the traditional soft handover algorithm. It has been observed that an adaptive threshold based algorithm can balance the traffic to some extent thereby enhancing the system performance. However, the choice of adaptive thresholds depends on the optimisation of different soft handover performance indicators.