Power control and slot allocation in a TD-CDMA system

Power control is a very important feature of CDMA systems and it dramatically impacts the cellular capacity. The UTRA-TDD (Universal Terrestrial Radio Interface with Time Division Duplex) adopted for third generation systems is a hybrid radio interface, which mixes TDMA and CDMA schemes. Therefore, power control and slot allocation must be optimised jointly. In this paper, we introduce two slot allocation methods combined with optimal power control. In the first method, we calculate the mean normalized path loss of mobile stations and try to obtain for each cell an allocation with the same mean normalized path loss on all time slots. In another way, we try to obtain the same signal to interference ratio in all cells. The principle of the second method is to group mobile stations with close path loss values on the same slot for each cell and associate a set of high-gain mobile stations of a cell with sets of low-gain mobile stations from neighbouring cells in the same time slot. The second method performs better than the first one and gives very close results to the optimal ones.