All-Digital Massive Mimo With a Fronthaul Constraint

Abstract

We analyze the uplink and downlink rates achievable in an all-digital massive multiple-input multiple-output system in which the base station (BS) is equipped with low-precision analog-to-digital and digital-to-analog converters, the size of the antenna array is limited, and there is a bandwidth constraint on the fronthaul link connecting the remote radio head to the digital baseband processing unit at the BS. Our results show that, at low SNR, it is better to use antenna arrays with many antenna elements, each one connected to low-precision converters, because this yields a beneficial array gain. On the contrary, at high SNR, it is better to reduce the number of active antenna elements, but increase the precision of the converters connected to them, because this allows one to separate more easily the data streams of the different users with simple linear baseband processing techniques.