Chapter 7 - Energy-Efficient Power Control Games

Abstract

Energy-efficiency is defined as the net number of information bits that are transmitted without error per unit time to the transmit power level. This chapter considers the pragmatic performance measure for analyzing the problem of distributed power control in wireless systems. This consideration is a distributed multiple access channel which consists of a network of several transmitters and one receiver. A static or one-shot game model is discussed. It is exploited to analyze the distributed power control problem where the transmit power level is updated once per block. The unique outcome of the game is a pure Nash equilibrium (NE). There is a linear pricing-based control, under which a pricing mechanism is introduced to improve the transmitters utilities at equilibrium. Implementing this pricing mechanism requires global channel state information at all the transmitters. Hierarchical power control game can be a given feature of the network, or it can be introduced in a distributed network to improve the network equilibrium efficiency. It explains repeated power control game in which the power levels are chosen in an independent manner from block to block. This chapter also includes slow power control and stochastic games under which two reasons are considered. First, the normalization “trick” used to exploit repeated games leads to sub-optimal expected utilities. Second, the framework of stochastic games is needed to study problems where the instantaneous utilities depend not only on the played actions, but also on the current channel state. Finally, this chapter discusses relaxing information and behavior assumptions. It is more realistic to assume that a transmitter can only have access to a certain estimate of the individual CSI (channel state information) or global CSI.