Mixed-ADC Massive MIMO Uplink in Frequency-Selective Channels

TL;DR

This paper investigates mixed-ADC massive MIMO uplink in frequency-selective channels, proposing a frequency-domain equalizer and analyzing achievable rates, showing significant performance gains over one-bit architectures.

Contribution

It introduces a novel mixed-ADC architecture with a frequency-domain equalizer for frequency-selective channels and derives analytical bounds for achievable rates.

Findings

Mixed-ADC architecture achieves most of the ideal rate with few high-resolution ADCs.

The proposed equalizer effectively mitigates inter-carrier interference.

Performance significantly surpasses one-bit massive MIMO systems.

Abstract

The aim of this paper is to investigate the recently developed mixed-ADC architecture for frequency-selective channels. Multi-carrier techniques such as orthogonal frequency division multiplexing (OFDM) are employed to handle inter-symbol interference (ISI). A frequency-domain equalizer is designed for mitigating the inter-carrier interference (ICI) introduced by the nonlinearity of one-bit quantization. For static single-input-multiple-output (SIMO) channels, a closed-form expression of the generalized mutual information (GMI) is derived, and based on which the linear frequency-domain equalizer is optimized. The analysis is then extended to ergodic time-varying SIMO channels with estimated channel state information (CSI), where numerically tight lower and upper bounds of the GMI are derived. The analytical framework is naturally applicable to the multi-user scenario, for both static and time-varying channels. Extensive numerical studies reveal that the mixed-ADC architecture with a small proportion of high-resolution ADCs does achieve a dominant portion of the achievable rate of ideal conventional architecture, and that it remarkably improves the performance as compared with one-bit massive MIMO.