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时代，从大规模天线阵列向更大规模天线阵列的演进趋势得以延续。然而，在用户设备（UE）的有限空间中安装更多天线面临挑战，尽管网络侧支持不断增加天线数量，但端用户所能获得的容量扩增增益仍然受限。为解决该问题，我们提出一种以终端用户为中心的协作MIMO（UE-CoMIMO）框架，该框架通过聚合多个固定或便携设备，提供虚拟的海量天线资源。本文阐述了高级L1中继与常规中继如何实现设备协作，从而在分集增益、秩增益及定位增强方面带来提升。通过系统级仿真，我们验证了UE-CoMIMO方法可带来显著的性能增益。最后，本文探讨了将UE-CoMIMO应用于6G所需的重点研究投入及未来研究方向。