I. Introduction
SINCE the early work of [1], there have been many research studies on power control of wireless networks. Due to the complexity of most wireless systems, and also the lack of full knowledge of the network parameters, instantaneous calculation of the optimal power vector is generally so hard and sometimes even impossible. Therefore, many of the power update algorithms use distributed iterative methods for reaching the optimal or suboptimal equilibrium power vector. Existence of fixed-point and convergence to the corresponding fixed-point are the first essential properties that must be verified for any iterative power update function. While in iterative power update functions, the transmit-power vector at any time step is a function of the transmit-power vector of the previous time step, in most existing distributed algorithms, the power update function of each user reduces to be only a function of the effective interference (the ratio of the interference to the path gain between that user and its corresponding receiver) experienced by that user (e.g., [2]– [7]).