Energy-Efficient Cell-Free Systems Using Finite Rate Feedback

Abstract

Cell-free system is a promising technology in which a group of base stations (BSs) cooperatively serves the user. One potential drawback of cell-free systems is that the intensive deployment of BSs might increase the energy consumption of the network. In order to improve the energy efficiency of cell-free systems, acquisition of accurate downlink channel state information (CSI) at the BSs is crucial. However, downlink CSI acquisition is not easy due to the CSI feedback overhead. This issue is even more pronounced in the cell-free systems since the user has to feed back the downlink CSIs of multiple BSs. In this paper, we propose energy-efficient dominating path selection (EE-DPS) algorithm to maximize the energy efficiency of cell-free systems with finite rate feedback. Key idea of the proposed algorithm is to choose a few dominating paths maximizing the energy efficiency and then only feed back the path gain information (PGI) of the chosen paths to the BSs. In doing so, the BSs can acquire relatively accurate PGI and utilize it to improve the energy efficiency. From the simulation results, we show that the proposed algorithm can improve the energy efficiency by more than 40% over the conventional power control schemes relying on the CSI feedback.