The role of small cells, coordinated multipoint, and massive MIMO in 5G

TLDR

5G must support a wide range of new applications requiring higher data rates, lower latency, better indoor coverage, and more devices, and the expected traffic growth can be met by expanding spectrum, increasing spectral efficiency, and densifying cells. The article proposes a smart combination of small cells, joint transmission coordinated multipoint, and massive MIMO to enhance spectral efficiency and improve coverage for cell‑edge users. The authors review recent progress in moving these concepts from theory to practice, outlining how the integrated small‑cell, JT CoMP, and massive‑MIMO architecture can be implemented with affordable complexity. Measurements in macro‑plus‑small‑cell scenarios demonstrate that flexible clustering, efficient user selection, and adaptive feedback compression boost spectral efficiency and reduce overhead, while fast feedback with advanced channel prediction mitigates JT CoMP impairments.

Abstract

5G will have to support a multitude of new applications with a wide variety of requirements, including higher peak and user data rates, reduced latency, enhanced indoor coverage, increased number of devices, and so on. The expected traffic growth in 10 or more years from now can be satisfied by the combined use of more spectrum, higher spectral efficiency, and densification of cells. The focus of the present article is on advanced techniques for higher spectral efficiency and improved coverage for cell edge users. We propose a smart combination of small cells, joint transmission coordinated multipoint (JT CoMP), and massive MIMO to enhance the spectral efficiency with affordable complexity. We review recent achievements in the transition from theoretical to practical concepts and note future research directions. We show in measurements with macro-plus-smallcell scenarios that spectral efficiency can be improved by flexible clustering and efficient user selection, and that adaptive feedback compression is beneficial to reduce the overhead significantly. Moreover, we show in measurements that fast feedback reporting combined with advanced channel prediction are able to mitigate the impairment effects of JT CoMP.