Joint Antenna Activation and Power Allocation for Energy-Efficient Cell-Free Massive MIMO Systems

In this letter, a joint antenna activation and power allocation (JAAPA) scheme is proposed for the downlink energy efficiency (EE) optimization in cell-free massive multiple-input multiple-output (MIMO) systems. Different from the traditional optimization approaches that only focus on power allocation, the proposed JAAPA scheme introduces the activated antenna number into the consideration of EE optimization, thus leading to a further improvement of EE. Specifically, the JAAPA scheme is formulated as a non-convex fractional optimization problem. In order to solve it in an efficient approach, we adopt the monotone accelerated proximal gradient (APG) algorithm to obtain a sub-optimal solution. Finally, simulation results validate that the proposed JAAPA scheme achieves a better trade-off between EE performance and computational complexity compared to the existing resource allocation schemes.