Millimeter Wave Receiver Efficiency: A Comprehensive Comparison of Beamforming Schemes with Low Resolution ADCs

TL;DR

This paper compares the spectral and energy efficiency of different beamforming schemes for millimeter wave receivers with low resolution ADCs, considering all component power consumption and practical limitations.

Contribution

It provides a comprehensive analysis and performance charts for Analog, Hybrid, and Digital Combining schemes, including a multi-objective optimization for SE-EE trade-offs.

Findings

AC is optimal only in low-rank, low SNR, or low power scenarios.

DC does not always require the highest power, contrary to common belief.

HC can outperform DC in SE-EE trade-offs depending on component power characteristics.

Abstract

In this work, we study the achievable rate and the energy efficiency of Analog, Hybrid and Digital Combining (AC, HC and DC) for millimeter wave (mmW) receivers. We take into account the power consumption of all receiver components, not just Analog-to-Digital Converters (ADC), determine some practical limitations of beamforming in each architecture, and develop performance analysis charts that enable comparison of different receivers simultaneously in terms of two metrics, namely, Spectral Efficiency (SE) and Energy Efficiency (EE). We present a multi-objective utility optimization interpretation to find the best SE-EE weighted trade-off among AC, DC and HC schemes. We consider an Additive Quantization Noise Model (AQNM) to evaluate the achievable rates with low resolution ADCs. Our analysis shows that AC is only advantageous if the channel rank is strictly one, the link has very low SNR, or there is a very stringent low power constraint at the receiver. Otherwise, we show that the usual claim that DC requires the highest power is not universally valid. Rather, either DC or HC alternatively result in the better SE vs EE trade-off depending strongly on the considered power consumption characteristic values for each component of the mmW receiver.