Uplink Power Control for Distributed Massive MIMO with 1-Bit ADCs

TL;DR

This paper investigates uplink power control in distributed massive MIMO systems with 1-bit ADCs, introducing algorithms to optimize transmit power and dithering to improve signal quality across multiple base stations.

Contribution

It provides new insights into SNDR behavior with 1-bit ADCs, and proposes three algorithms for joint power and dithering optimization in multi-UE scenarios.

Findings

SNDR is unimodal with single BS, and can be made unimodal with dithering in multi-BS setups.

Optimal UE power depends on the farthest BS distance when using joint combining.

Dithering significantly improves SINDR, especially with large path loss disparities.

Abstract

We consider the problem of uplink power control for distributed massive multiple-input multiple-output systems where the base stations (BSs) are equipped with 1-bit analog-to-digital converters (ADCs). The scenario with a single-user equipment (UE) is first considered to provide insights into the signal-tonoise-and-distortion ratio (SNDR). With a single BS, the SNDR is a unimodal function of the UE transmit power. With multiple BSs, the SNDR at the output of the joint combiner can be made unimodal by adding properly tuned dithering at each BS. As a result, the UE can be effectively served by multiple BSs with 1-bit ADCs. Considering the signal-to-interference-plus-noise-anddistortion ratio (SINDR) in the multi-UE scenario, we aim at optimizing the UE transmit powers and the dithering at each BS based on the min-power and max-min-SINDR criteria. To this end, we propose three algorithms with different convergence and complexity properties. Numerical results show that, if the desired SINDR can only be achieved via joint combining across multiple BSs with properly tuned dithering, the optimal UE transmit power is imposed by the distance to the farthest serving BS (unlike in the unquantized case). In this context, dithering plays a crucial role in enhancing the SINDR, especially for UEs with significant path loss disparity among the serving BSs.