In 6G, the trend of transitioning from massive antenna elements to even more massive ones is continued. However, installing additional antennas in the limited space of user equipment (UE) is challenging, resulting in limited capacity scaling gain for end users, despite network side support for increasing numbers of antennas. To address this issue, we propose an end-user-centric collaborative MIMO (UE-CoMIMO) framework that groups several fixed or portable devices to provide a virtual abundance of antennas. This article outlines how advanced L1 relays and conventional relays enable device collaboration to offer diversity, rank, and localization enhancements. We demonstrate through system-level simulations how the UE-CoMIMO approaches lead to significant performance gains. Lastly, we discuss necessary research efforts to make UE-CoMIMO available for 6G and future research directions.

翻译：在6G中，从大规模天线阵列向超大规模天线阵列演进的趋势得以延续。然而，在用户设备（UE）的有限空间内安装更多天线极具挑战性，导致尽管网络侧支持天线数量增加，但终端用户仍面临容量扩展增益受限的问题。为解决这一难题，我们提出一种以用户为中心的协作MIMO（UE-CoMIMO）框架，该框架通过聚合多个固定或便携式设备，形成虚拟的丰富天线阵列。本文阐述了先进的L1中继与常规中继如何通过设备协作实现分集增益、秩增益及定位增强。通过系统级仿真，我们验证了UE-CoMIMO方案可带来显著的性能提升。最后，本文讨论了使UE-CoMIMO适用于6G所需的关键研究方向及未来探索方向。