Power control algorithms and stability analysis for radio network control

Power control algorithms in cellular radio networks are analyzed. This is basically a MIMO problem where the controlled input is the powers used by the transmitters, and the measurements consist of signal to interference ratios for each receiver. These algorithms can, for each single connection and neglecting the cross couplings, be interpreted as a feedback system. The main contribution here is to analyze a generic control algorithm, which covers some important suggested classical control theory methods such as the root locus and describing function. The results include the important conclusion that unavoidable time delays and nonlinearities (saturation and quantization) in the feedback loop can cause a considerable loss in the stability margin. The results are supported by simulations