Performance Analysis of Mixed-ADC Massive MIMO Systems over Rician Fading Channels (1703.03642v1)

Abstract: The practical deployment of massive multiple-input multiple-output (MIMO) in future fifth generation (5G) wireless communication systems is challenging due to its high hardware cost and power consumption. One promising solution to address this challenge is to adopt the low-resolution analog-to-digital converter (ADC) architecture. However, the practical implementation of such architecture is challenging due to the required complex signal processing to compensate the coarse quantization caused by low-resolution ADCs. Therefore, few high-resolution ADCs are reserved in the recently proposed mixed-ADC architecture to enable low-complexity transceiver algorithms. In contrast to previous works over Rayleigh fading channels, we investigate the performance of mixed-ADC massive MIMO systems over the Rician fading channel, which is more general for the 5G scenarios like Internet of Things (IoT). Specially, novel closed-form approximate expressions for the uplink achievable rate are derived for both cases of perfect and imperfect channel state information (CSI). With the increasing Rician $K$-factor, the derived results show that the achievable rate will converge to a fixed value. We also obtain the power-scaling law that the transmit power of each user can be scaled down proportionally to the inverse of the number of base station (BS) antennas for both perfect and imperfect CSI. Moreover, we reveal the trade-off between the achievable rate and energy efficiency with respect to key system parameters including the quantization bits, number of BS antennas, Rician $K$-factor, user transmit power, and CSI quality. Finally, numerical results are provided to show that the mixed-ADC architecture can achieve a better energy-rate trade-off compared with the ideal infinite-resolution and low-resolution ADC architectures.

• The paper derives approximate uplink achievable rate expressions under both perfect and imperfect CSI, considering key parameters like quantization bits and the Rician K-factor.
• It establishes power-scaling laws that allow reduced user transmit power with increasing base station antennas even under nonzero Rician conditions.
• It evaluates the energy efficiency versus rate trade-off to optimize mixed-ADC configurations for scalable 5G implementations.

Performance Analysis of Mixed-ADC Massive MIMO Systems over Rician Fading Channels

The paper "Performance Analysis of Mixed-ADC Massive MIMO Systems over Rician Fading Channels" by Jiayi Zhang et al. explores the intricacies of implementing massive MIMO systems in the context of Rician fading channels for 5G communications. The paper addresses the significant challenges associated with hardware cost and power consumption due to the large number of RF chains required by traditional massive MIMO architectures. The authors propose and analyze a mixed-ADC architecture as a practical solution to mitigate these issues.

Main Contributions

The paper primarily contributes to the field by focusing on several novel aspects related to the mixed-ADC architecture in the presence of Rician fading channels:

1. Achievable Rate Expressions: The authors derive closed-form approximate expressions for the uplink achievable rate in massive MIMO systems, considering both perfect and imperfect channel state information (CSI). They address the influence of several parameters, such as the number of base station (BS) antennas, quantization bits, and the Rician K-factor.
2. Power-Scaling Laws: The research outlines power-scaling laws, demonstrating that user transmit power can be proportionally reduced with an increase in the number of BS antennas. This holds for both perfect and imperfect CSI scenarios, provided the Rician K-factor is nonzero.
3. Energy Efficiency vs. Achievable Rate Trade-Off: Through a generic power consumption model, the authors explore the trade-off between rate and energy efficiency with varying parameters like the number of high-resolution ADCs and quantization levels. They provide insights into optimizing these configurations to achieve the best energy-rate trade-offs.

Key Findings and Implications

A significant finding from this research is the convergence of the achievable rate to a fixed value as the Rician K-factor increases, indicating robustness in LoS-dominant conditions. The paper confirms that while the mixed-ADC architecture can approximate the performance of high-resolution ADC systems, it offers a more favorable balance between performance, energy consumption, and hardware cost, making it a viable option for scalable 5G implementations.

The findings also highlight that improvements in energy efficiency can be achieved by adjusting the proportion of high- to low-resolution ADCs, especially under strong Rician fading conditions. This implies that the mixed-ADC architecture can be particularly beneficial in scenarios with high user mobility or urban environments where Rician fading is prevalent.

Future Directions

The implications of this paper extend towards future designs and optimizations in massive MIMO systems using mixed-ADC architectures. Given the results, further exploration into adaptive algorithms that can dynamically adjust ADC configurations based on environmental and operational conditions could be compelling. Additionally, expanding this analysis to consider more advanced signal processing techniques or hybrid architectures that integrate mixed-ADC with other energy-efficient schemes could pave the way for even more effective 5G systems.

This research, therefore, provides a strong foundation for optimizing the balance between achievable rates and energy efficiency in 5G networks, potentially influencing future standards and hardware designs in wireless communication systems.