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

## TL;DR

This paper analyzes the performance of mixed-ADC massive MIMO systems over Rician fading channels, deriving closed-form expressions for achievable rates and exploring energy efficiency and power scaling laws.

## Contribution

It introduces novel analytical expressions for mixed-ADC massive MIMO over Rician channels and examines the trade-offs between energy efficiency and achievable rate.

## Key findings

- Achievable rate converges with increasing Rician K-factor.
- Transmit power can be scaled down inversely with the number of antennas.
- Mixed-ADC architecture offers better energy-rate trade-off than pure low- or high-resolution systems.

## 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.