[Paper Review] Mixed-ADC/DAC Multipair Massive MIMO Relaying Systems: Performance Analysis and Power Optimization

Jiayi Zhang, Linglong Dai+3 more|arXiv (Cornell University)|Sep 10, 2018

Cooperative Communication and Network Coding37 references4 citations

TL;DR

This paper proposes a mixed-ADC/DAC architecture for multipair massive MIMO relaying systems, combining high- and low-resolution converters to reduce hardware cost and power consumption. Using the additive quantization noise model, it derives exact and approximate closed-form expressions for achievable rate, showing that 2–3 bits of resolution can approach unquantized performance, while a power scaling law enables inverse proportional power reduction with increasing antennas.

ABSTRACT

High power consumption and expensive hardware are two bottlenecks for practical massive multiple-input multiple-output (mMIMO) systems. One promising solution is to employ low-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). In this paper, we consider a general multipair mMIMO relaying system with a mixed-ADC/DAC architecture, in which some antennas are connected to low-resolution ADCs/DACs, while the rest of the antennas are connected to high-resolution ADCs/DACs. Leveraging on the additive quantization noise model, both exact and approximate closed-form expressions for the achievable rate are derived. It is shown that the achievable rate can approach the unquantized one by using only 2-3 bits of resolutions. Moreover, a power scaling law is presented to reveal that the transmit power can be scaled down inversely proportional to the number of antennas at the relay. We further propose an efficient power allocation scheme by solving a complementary geometric programming problem. In addition, a trade-off between the achievable rate and power consumption for different numbers of low-resolution ADCs/DACs is investigated by deriving the energy efficiency. Our results reveal that the large antenna array can be exploited to enable the mixed-ADC/DAC architecture, which significantly reduces the power consumption and hardware cost for practical mMIMO systems.

Motivation & Objective

• To address high power consumption and hardware cost in massive MIMO relaying systems.
• To investigate the performance of mixed-ADC/DAC architectures where only a subset of antennas use low-resolution converters.
• To derive closed-form expressions for achievable rate under mixed-ADC/DAC configurations.
• To optimize power allocation and reveal energy efficiency trade-offs in practical mMIMO relaying systems.

Proposed method

• Uses the additive quantization noise model (AQNM) to model non-linear quantization effects in low-resolution ADCs/DACs.
• Derives exact and approximate closed-form expressions for the achievable rate in a multipair massive MIMO relaying system with mixed-ADC/DAC architecture.
• Applies large-scale MIMO channel assumptions and statistical channel state information (CSI) to compute expectation terms over fading distributions.
• Proposes a complementary geometric programming-based power allocation scheme to optimize system performance under hardware constraints.
• Derives a power scaling law showing that transmit power scales inversely with the number of relay antennas.
• Evaluates energy efficiency by analyzing the trade-off between achievable rate and power consumption across different numbers of low-resolution ADCs/DACs.

Experimental results

Research questions

• RQ1 Can a mixed-ADC/DAC architecture achieve spectral efficiency close to that of unquantized systems with only 2–3 bits of resolution?
• RQ2 How does the achievable rate scale with the number of antennas and the number of low-resolution converters in the system?
• RQ3 What power scaling law governs the transmit power reduction in mixed-ADC/DAC massive MIMO relaying systems?
• RQ4 How can power be efficiently allocated to maximize spectral efficiency under hardware and energy constraints?
• RQ5 What is the trade-off between spectral efficiency and energy efficiency for different configurations of low-resolution ADCs/DACs?

Key findings

• Achievable rate with 2–3 bits of ADC/DAC resolution can closely approach the unquantized system performance.
• The system achieves a power scaling law where transmit power scales inversely with the number of relay antennas, enabling significant energy savings.
• The proposed power allocation scheme based on complementary geometric programming effectively optimizes spectral efficiency under hardware and energy constraints.
• Energy efficiency is maximized by carefully selecting the number of low-resolution ADCs/DACs, showing a clear trade-off between rate and power consumption.
• The mixed-ADC/DAC architecture enables substantial reductions in hardware cost and power consumption while maintaining high spectral efficiency.
• Theoretical analysis confirms that large antenna arrays can effectively mitigate the performance loss from coarse quantization, making the architecture viable for practical mMIMO relaying.