Limited fronthaul capacity is a practical bottleneck in massive multiple-input multiple-output (MIMO) 5G architectures, where a base station (BS) consists of an advanced antenna system (AAS) connected to a baseband unit (BBU). Conventional downlink designs place the entire precoding computation at the BBU and transmit a high-dimensional precoding matrix over the fronthaul, resulting in substantial quantization losses and signaling overhead. This letter proposes a splitting precoding architecture that separates the design between the AAS and BBU. The AAS performs a local subspace selection to reduce the channel dimensionality, while the BBU computes an optimized quantized refinement precoding based on the resulting effective channel. The numerical results show that the proposed splitting precoding strategy achieves higher sum spectral efficiency than conventional one-stage precoding.

翻译：有限的前传容量是大规模多输入多输出（MIMO）5G架构中的一个实际瓶颈，其中基站（BS）由连接至基带单元（BBU）的先进天线系统（AAS）构成。传统的下行链路设计将完整的预编码计算置于BBU，并通过前传传输高维预编码矩阵，导致显著的量化损失与信令开销。本文提出一种分裂预编码架构，将设计任务分离至AAS与BBU。AAS执行本地子空间选择以降低信道维度，而BBU则基于所得等效信道计算优化的量化修正预编码。数值结果表明，所提出的分裂预编码策略相比传统单级预编码实现了更高的总频谱效率。