Doubly Massive mmWave MIMO Systems: Using Very Large Antenna Arrays at Both Transmitter and Receiver

TL;DR

This paper explores the concept of doubly massive MIMO systems at mmWave frequencies, where both transmitter and receiver have large antenna arrays, fundamentally changing the channel properties and system design considerations.

Contribution

It introduces the doubly massive MIMO concept at mmWave, highlighting the shift in multiplexing and channel rank dependence from antenna count to environmental scattering clusters.

Findings

Channel rank depends on scattering clusters, not antenna numbers.

Doubly massive MIMO alters transceiver processing requirements.

Implications for energy efficiency and throughput are discussed.

Abstract

One of the key features of next generation wireless communication systems will be the use of frequencies in the range 10-100GHz (aka mmWave band) in densely populated indoor and outdoor scenarios. Due to the reduced wavelength, antenna arrays with a large number of antennas can be packed in very small volumes, making thus it possible to consider, at least in principle, communication links wherein not only the base-station, but also the user device, are equipped with very large antenna arrays. We denote this configuration as a "doubly-massive" MIMO wireless link. This paper introduces the concept of doubly massive MIMO systems at mmWave, showing that at mmWave the fundamentals of the massive MIMO regime are completely different from what happens at conventional sub-6 GHz cellular frequencies. It is shown for instance that the multiplexing capabilities of the channel and its rank are no longer ruled by the number of transmit and receive antennas, but rather by the number of scattering clusters in the surrounding environment. The implications of the doubly massive MIMO regime on the transceiver processing, on the system energy efficiency and on the system throughput are also discussed.