Power control models in cellular CDMA systems

Abstract

CDMA cellular systems are expected to solve demand explosion by its large capacity. But its advantages including capacity improvement need some more complicated operations. Among these, power control on radio link is a fundamental one. That is, large capacity is obtained only if transmitters appropriately control their powers. Therefore many researches on this topic have been reported, but these studies concentrate only on the traffic channel, so powers of other channels including pilot channel are neglected or regarded implicitly as constants. As a result, cell boundary is unstable, even worse service-blank area may be occurred in the worst case. In this paper, we consider the power control models in which power of pilot channels are also taken into account. Power balancing problem and power minimization problem are introduced and formulated as a linear program and a nonlinear program, respectively. Next, a solution method for each of them is suggested. For the numerical experiment of the above models, various environments - large/small number of cells, uniform/nonuniform traffic and sparse/dense traffic, are considered. After a round of tests for the examples, it is found that given traffic, the power of pilot channel is usually constant over cells and that the power of traffic channels are mainly proportional to both traffic densities of cells and the average distances between mobiles and base-stations.