Analysis of Uplink Cell-Free Massive MIMO System With Mixed-ADC/DAC Receiver

Abstract

A generalized uplink cell-free massive multi-input multi-output (MIMO) system assuming access points (APs) are paired with mixed-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) is investigated in this article. Specifically, the mixed-ADC/DAC architecture sacrifices part of performance gains and advocates a few low-precision ADCs/DACs to reduce the power consumption. Based on this antenna structure, we derive closed-form achievable rate expressions for maximal ratio combining (MRC) receiver filters by drawing support from the additive quantization noise model (AQNM) and analyze the impacts of the key design parameters, i.e., the number of total antenna arrays, the precision of coarse ADCs/DACs, the proportion of ideal ADCs/DACs in the mixed ADCs/DACs structure, and the power control strategy. In addition, the energy efficiency (EE) of the considered mixed-ADC/DAC architecture is also explored by recalling a generic power consumption model. Aside from this, to guarantee uniformly good service wherever users are geographically located, a max–min fairness power optimization algorithm is proposed, which can be determined by solving a geometric programming problem. Numerical simulations validate our theoretical analyses and examine the effectiveness of the proposed algorithm.