Scaling up MIMO: Opportunities and Challenges with Very Large Arrays

TL;DR

This survey explores the potential and challenges of very large MIMO systems with hundreds of antennas, highlighting their paradigm shift in wireless communication, system design, and implementation.

Contribution

It provides a comprehensive overview of recent advances, identifies key challenges, and discusses future research directions for very large MIMO technology.

Findings

Very large MIMO can serve more terminals by combining with traditional multiplexing.

Channel-state information acquisition limits the number of simultaneously served terminals.

Integration with OFDM enables accommodating more users in large MIMO systems.

Abstract

This paper surveys recent advances in the area of very large MIMO systems. With very large MIMO, we think of systems that use antenna arrays with an order of magnitude more elements than in systems being built today, say a hundred antennas or more. Very large MIMO entails an unprecedented number of antennas simultaneously serving a much smaller number of terminals. The disparity in number emerges as a desirable operating condition and a practical one as well. The number of terminals that can be simultaneously served is limited, not by the number of antennas, but rather by our inability to acquire channel-state information for an unlimited number of terminals. Larger numbers of terminals can always be accommodated by combining very large MIMO technology with conventional time- and frequency-division multiplexing via OFDM. Very large MIMO arrays is a new research field both in communication theory, propagation, and electronics and represents a paradigm shift in the way of thinking both with regards to theory, systems and implementation. The ultimate vision of very large MIMO systems is that the antenna array would consist of small active antenna units, plugged into an (optical) fieldbus.