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：本文研究大规模多输入多输出（MIMO）预编码器在满足用户速率需求的同时优化功耗的问题。我们首先解析性地刻画了低系统负载下窄带与宽带系统最小化功率放大器（PA）消耗的解，此时每天线功率约束未生效。随后，我们聚焦于渐近宽带场景。此外，我们还研究了整个基站（BS）的功耗以及高负载场景。我们得到了简洁的解，在渐近情况下的最优策略简化为依据已知预编码器确定最优激活天线数量，并在激活天线间应用这些预编码器。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消耗的宽带系统中，所有天线均需激活，因此节能幅度较小。当考虑基站整体功耗及大量子载波时，我们证明，在低负载场景下使用部分基站天线子集可实现显著的功耗节省。基于发射功率的优化会促使激活所有天线，而基于功耗的优化则激活数量与负载成比例的天线。