An effective dynamic slot allocation strategy based on zone division in WCDMA/TDD systems

WCDMA/TDD systems deal efficiently with asymmetric traffic because the number of uplink and downlink slots in the TDD frame can be dynamically adjusted to match the traffic asymmetry in a cell. In a multi-cellular environment however, the traffic asymmetry between TDD cells may be significantly different and the application of slot allocation strategies on a per cell basis can result in high levels of inter-cell interference during 'crossed-slots'. In this paper we propose an adaptive dynamic slot allocation strategy (DSA) that resolves crossed-slot interference in multi-cell environments by dividing the coverage area of each cell into a number of distinct service zones. This is coupled with a co-ordination algorithm that ensures that system resources are allocated to users according to the level of mutual interference between the service zones. System capacity calculations validate our DSA strategy and demonstrate that it outperforms both conventional 'same slot' allocation schemes and other previously proposed DSA schemes in heterogeneous traffic environments.