# An Overview of Massive MIMO Research at the University of Bristol

## TL;DR

This paper reviews the University of Bristol's massive MIMO research, highlighting real-world trials with a 128-antenna testbed that achieved record spectral efficiencies and exploring future research directions for practical deployment.

## Contribution

It presents the first real-time 128-antenna massive MIMO testbed and reports record spectral efficiency results, advancing pragmatic understanding of the technology.

## Key findings

- Achieved 79.4 bits/s/Hz spectral efficiency in trials
- Demonstrated potential to increase efficiency to 145.6 bits/s/Hz
- Outlined ongoing research in wave-front analysis, power control, and localization

## Abstract

Massive MIMO has rapidly gained popularity as a technology crucial to the capacity advances required for 5G wireless systems. Since its theoretical conception six years ago, research activity has grown exponentially, and there is now a developing industrial interest to commercialise the technology. For this to happen effectively, we believe it is crucial that further pragmatic research is conducted with a view to establish how reality differs from theoretical ideals. This paper presents an overview of the massive MIMO research activities occurring within the Communication Systems & Networks Group at the University of Bristol centred around our 128-antenna real-time testbed, which has been developed through the BIO programmable city initiative in collaboration with NI and Lund University. Through recent preliminary trials, we achieved a world first spectral efficiency of 79.4 bits/s/Hz, and subsequently demonstrated that this could be increased to 145.6 bits/s/Hz. We provide a summary of this work here along with some of our ongoing research directions such as large-scale array wave-front analysis, optimised power control and localisation techniques.