5G Millimeter Wave Cellular System Capacity with Fully Digital Beamforming

TL;DR

This paper demonstrates that low-resolution digital beamforming in 5G mmWave systems can achieve near-optimal capacity with significant power savings, enabling flexible and efficient cellular communication.

Contribution

It introduces an AWGN-based model to evaluate low-resolution quantization effects, showing minimal capacity loss at 3-4 bits per ADC, thus supporting power-efficient digital beamforming.

Findings

Negligible capacity loss at 3-4 bits ADC resolution

Low-resolution ADCs limit high SNR operation

Digital beamforming offers enhanced control and comparable data performance

Abstract

Due to heavy reliance of millimeter-wave (mmWave) wireless systems on directional links, Beamforming (BF) with high-dimensional arrays is essential for cellular systems in these frequencies. How to perform the array processing in a power efficient manner is a fundamental challenge. Analog and hybrid BF require fewer analog-to-digital converters (ADCs), but can only communicate in a small number of directions at a time,limiting directional search, spatial multiplexing and control signaling. Digital BF enables flexible spatial processing, but must be operated at a low quantization resolution to stay within reasonable power levels. This paper presents a simple additive white Gaussian noise (AWGN) model to assess the effect of low resolution quantization of cellular system capacity. Simulations with this model reveal that at moderate resolutions (3-4 bits per ADC), there is negligible loss in downlink cellular capacity from quantization. In essence, the low-resolution ADCs limit the high SNR, where cellular systems typically do not operate. The findings suggest that low-resolution fully digital BF architectures can be power efficient, offer greatly enhanced control plane functionality and comparable data plane performance to analog BF.