EVM Analysis of Distributed Massive MIMO with 1-Bit Radio-Over-Fiber Fronthaul

TL;DR

This paper evaluates a distributed massive MIMO system with 1-bit quantized RF signals over fiber fronthaul, focusing on performance tradeoffs and optimal design to outperform traditional setups.

Contribution

It introduces a novel architecture eliminating local oscillators at APs and analyzes the tradeoff between spatial and temporal oversampling under fronthaul constraints.

Findings

Optimal dither signal design improves performance.

Minimum fronthaul rate needed for superiority over co-located MIMO.

Tradeoff analysis guides system design choices.

Abstract

We analyze the uplink performance of a distributed massive multiple-input multiple-output (MIMO) architecture in which the remotely located access points (APs) are connected to a central processing unit via a fiber-optical fronthaul carrying a dithered and 1-bit quantized version of the received radio-frequency (RF) signal. The innovative feature of the proposed architecture is that no down-conversion is performed at the APs. This eliminates the need to equip the APs with local oscillators, which may be difficult to synchronize. Under the assumption that a constraint is imposed on the amount of data that can be exchanged across the fiber-optical fronthaul, we investigate the tradeoff between spatial oversampling, defined in terms of the total number of APs, and temporal oversampling, defined in terms of the oversampling factor selected at the central processing unit, to facilitate the recovery of the transmitted signal from 1-bit samples of the RF received signal. Using the so-called error-vector magnitude (EVM) as performance metric, we shed light on the optimal design of the dither signal, and quantify, for a given number of APs, the minimum fronthaul rate required for our proposed distributed massive MIMO architecture to outperform a standard co-located massive MIMO architecture in terms of EVM.