The deployment of large-scale antenna arrays for cellular base stations
(BSs), termed as `Massive MIMO', has been a key enabler for meeting the
ever-increasing capacity requirement for 5G communication systems and beyond.
Despite their promising performance, fully-digital massive MIMO systems require
a vast amount of hardware components including radio frequency chains, power
amplifiers, digital-to-analog converters (DACs), etc., resulting in a huge
increase in terms of the total power consumption and hardware costs for
cellular BSs. Towards both spectrally-efficient and energy-efficient massive
MIMO deployment, a number of hardware limited architectures have been proposed,
including hybrid analog-digital structures, constant-envelope transmission, and
use of low-resolution DACs. In this paper, we overview the recent interest in
improving the error-rate performance of massive MIMO systems deployed with
1-bit DACs through precoding at the symbol level. This line of research goes
beyond traditional interference suppression or cancellation techniques by
managing interference on a symbol-by-symbol basis. This provides unique
opportunities for interference-aware precoding tailored for practical massive
MIMO systems. Firstly, we characterize constructive interference (CI) and
elaborate on how CI can benefit the 1-bit signal design by exploiting the
traditionally undesired multi-user interference as well as the interference
from imperfect hardware components. Subsequently, we overview several solutions
for 1-bit signal design to illustrate the gains achievable by exploiting CI.
Finally, we identify some challenges and future research directions for 1-bit
massive MIMO systems that are yet to be explored.Comment: This work has been submitted to the IEEE for possible publication.
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