Dynamic Base Station Sleep Control and RF Chain Activation for Energy-Efficient Millimeter-Wave Cellular Systems

Abstract

In a millimeter-wave base station (BS) with hybrid precoding, the radio frequency (RF) chain is the main contributor to the energy consumption. As the traffic pattern varies over time, part of the RF chains in a BS or the entire BS can be turned off to prevent overheating and save energy. However, to guarantee the multiplexing gain of a hybrid precoding system, a certain number of RF chains needs to be activated. In addition, as BSs are turned off , the quality of service of users would be degraded. Thus, the number of active RF chains and the set of operating BSs should be carefully designed to achieve a tradeoff between data rate and energy consumption. We consider dynamic BS sleep control and RF chain activation to maximize the energy efficiency (EE) of a multicell millimeter-wave cellular systems. We formulate such a problem as an integer programming problem with two sets of variables. We first develop a centralized scheme, and then apply a primal decomposition to derive the optimal solution of the convex problem. Based on such solution, we derive the near optimal BS sleep control strategy with a greedy algorithm. With given BS on–off states, the optimal user association and RF chain activation are obtained by solving a linear programming problem. We then propose a distributed scheme based on a matching between users and BSs, and show that the matching process converges. The proposed schemes are evaluated with simulations, showing that near optimal performance can be achieved. Compared with baseline schemes, the system EE can be significantly improved while the data rate loss due to BS sleep control and dynamic RF chain activation is relatively small.