Cell-free massive multi-input multi-output (CFmMIMO) offers uniform service quality through distributed access points (APs), yet unresolved issues remain. This paper proposes a heterogeneous system design that goes beyond the original CFmMIMO architecture by exploiting the synergy of a base station (BS) and distributed APs. Users are categorized as near users (NUs) and far users (FUs) depending on their proximity to the BS. The BS serves the NUs, while the APs cater to the FUs. Through activating only the closest AP of each FU, the use of downlink pilots is enabled, thereby enhancing performance. This heterogeneous design outperforms other homogeneous massive MIMO configurations, demonstrating superior sum capacity while maintaining comparable user-experienced rates. Moreover, it lowers the costs associated with AP installations and reduces signaling overhead for the fronthaul network.

翻译：无蜂窝大规模多输入多输出（CFmMIMO）通过分布式接入点（AP）提供均匀的服务质量，但仍存在未解决的问题。本文提出了一种异构系统设计，通过利用基站（BS）与分布式AP的协同作用，超越了原始CFmMIMO架构。根据用户与BS的距离远近，将用户划分为近端用户（NU）和远端用户（FU）。BS服务于NU，而AP则服务于FU。通过仅激活每个FU最近的AP，实现了下行链路导频的使用，从而提升了系统性能。该异构设计优于其他同构大规模MIMO配置，在保持可比用户感知速率的同时，展现出更优的总容量。此外，它还降低了AP部署成本，并减少了前传网络的信令开销。