Distributed Cross-layer Power Control in Pre-equalized Downlink of a MC-CDMA System

Abstract

The main purpose of this elaboration is to determine the optimal powers of mobile users in a multi-carrier CDMA (MC-CDMA) system receiving data from a base station (BS). The downlink transmission is pre-equalized and the utility function is a generalized energy efficiency (EE) based on a cross-layer approach and taking into account the presence of a queue. We rely on game theory as a mathematical tool by considering a non-cooperative game whose equilibrium point is called Nash equilibrium (NE) defining the optimal powers. Accordingly, we developed a distributed algorithm aiming at determining this equilibrium. When the subcarriers number increases, important interference is then introduced. In such case, we showed that the social welfare (sum of utilities of all users) decreases while powers at NE increase. In addition, we deduced that a good choice of the consumed power leads to minimize the individual power and maximize the utility at the NE. Moreover, we noticed that when the packet arrival rate increases, the considered generalized EE can be maximized compared to the conventional EE approach while the power at the NE can be minimized. Therefore, we contribute to improve globally the system performances in terms of social welfare, individual utility function and individual power.