Performance Analysis of Mixed-ADC Massive MIMO Systems Over Spatially Correlated Channels

This paper analyzes the uplink performance of multiuser massive multi-input-multi-output systems with spatially correlated channels by using a mixed analog-to-digital converter (ADC) architecture, where the base station (BS) is equipped with two resolution level's ADC. More specifically, the exponential correlation matrix model is used for modeling spatially correlated channels. Meanwhile, the additive quantized noise model and the maximum ratio combining technique are used at the BS receiver. Thereby, closed-form approximations for the achievable rate are derived under perfect and imperfect channel state information (CSI), respectively. In addition, we have studied the tradeoff between achievable rate and energy efficiency. Then, the influence of physical parameters on the corresponding results is analyzed, including user transmit power, the number of BS antennas, spatial correlation coefficient, CSI errors, and ADC quantization resolution. The numerical results show that as the spatial correlation coefficient increases, the achievable rate is almost constant at the low signal-to-noise-ratio (SNR) stage, but the achievable rate is gradually reduced to near zero at the high SNR stage. Furthermore, in terms of the tradeoff between achievable rate and energy efficiency, the performance of the two-level ADC architecture is significantly better than the uniform ADC architecture.