In this work, we study massive multiple-input multiple-output (MIMO) precoders optimizing power consumption while achieving the users' rate requirements. We first characterize analytically the solutions for narrowband and wideband systems minimizing the power amplifiers (PAs) consumption in low system load, where the per-antenna power constraints are not binding. After, we focus on the asymptotic wideband regime. The power consumed by the whole base station (BS) and the high-load scenario are then also investigated. We obtain simple solutions, and the optimal strategy in the asymptotic case reduces to finding the optimal number of active antennas, relying on known precoders among the active antennas. Numerical results show that large savings in power consumption are achievable in the narrowband system by employing antenna selection, while all antennas need to be activated in the wideband system when considering only the PAs consumption, and this implies lower savings. When considering the overall BS power consumption and a large number of subcarriers, we show that significant savings are achievable in the low-load regime by using a subset of the BS antennas. While optimization based on transmit power pushes to activate all antennas, optimization based on consumed power activates a number of antennas proportional to the load.

翻译：本文研究了大规模多输入多输出（MIMO）系统中优化功耗同时满足用户速率需求的预编码器设计。我们首先在低系统负载且天线功率约束不成立的情况下，对窄带和宽带系统中最小化功率放大器（PA）功耗的解进行解析表征。随后，我们聚焦于渐近宽带场景。进一步研究了整个基站（BS）的功耗及高负载场景。我们得到了简单解，并在渐近情况下最优策略简化为确定最优活跃天线数量，依赖于已知的活跃天线间预编码器。数值结果表明：在窄带系统中，通过天线选择可实现显著的功耗节省；而在仅考虑PA功耗的宽带系统中，所有天线均需激活，此时功耗节省较少。当考虑整体基站功耗及大量子载波时，我们证明在低负载场景下通过使用基站天线子集可实现显著节能。基于发射功率的优化倾向于激活所有天线，而基于总功耗的优化则激活与负载成比例的天线数量。