DOA Estimation for Hybrid Massive MIMO Systems using Mixed-ADCs: Performance Loss and Energy Efficiency

TL;DR

This paper proposes a mixed-ADC and hybrid analog-digital architecture for DOA estimation in massive MIMO systems, deriving performance bounds, analyzing energy efficiency, and demonstrating a favorable trade-off between cost, power, and estimation accuracy.

Contribution

It introduces a novel combination of mixed-ADC and HAD structures for DOA estimation, providing closed-form performance bounds and analyzing energy efficiency in massive MIMO.

Findings

HAD with mixed-ADCs reduces power consumption and hardware cost.

The architecture achieves a better trade-off between performance loss and energy efficiency.

2-4 bit resolution ADCs are effective in practical systems.

Abstract

Due to the power consumption and high circuit cost in antenna arrays, the practical application of massive multiple-input multiple-output (MIMO) in the sixth generation (6G) and future wireless networks is still challenging. Employing low-resolution analog-to-digital converters (ADCs) and hybrid analog and digital (HAD) structure is two low-cost choice with acceptable performance loss.In this paper, the combination of the mixed-ADC architecture and HAD structure employed at receiver is proposed for direction of arrival (DOA) estimation, which will be applied to the beamforming tracking and alignment in 6G. By adopting the additive quantization noise model, the exact closed-form expression of the Cram\'{e}r-Rao lower bound (CRLB) for the HAD architecture with mixed-ADCs is derived. Moreover, the closed-form expression of the performance loss factor is derived as a benchmark. In addition, to take power consumption into account, energy efficiency is also investigated in our paper. The numerical results reveal that the HAD structure with mixed-ADCs can significantly reduce the power consumption and hardware cost. Furthermore, that architecture is able to achieve a better trade-off between the performance loss and the power consumption. Finally, adopting 2-4 bits of resolution may be a good choice in practical massive MIMO systems.