In this paper, we investigate network-assisted full-duplex (NAFD) cell-free millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems with digital-to-analog converter (DAC) quantization and fronthaul compression. We propose to maximize the weighted uplink and downlink sum rate by jointly optimizing the power allocation of both the transmitting remote antenna units (T-RAUs) and uplink users and the variances of the downlink and uplink fronthaul compression noises. To deal with this challenging problem, we further apply a successive convex approximation (SCA) method to handle the non-convex bidirectional limited-capacity fronthaul constraints. The simulation results verify the convergence of the proposed SCA-based algorithm and analyze the impact of fronthaul capacity and DAC quantization on the spectral efficiency of the NAFD cell-free mmWave massive MIMO systems. Moreover, some insightful conclusions are obtained through the comparisons of spectral efficiency, which shows that NAFD achieves better performance gains than co-time co-frequency full-duplex cloud radio access network (CCFD C-RAN) in the cases of practical limited-resolution DACs. Specifically, their performance gaps with 8-bit DAC quantization are larger than that with 1-bit DAC quantization, which attains a 5.5-fold improvement.

翻译：本文研究了采用数模转换器（DAC）量化与回程压缩的网络辅助全双工（NAFD）无小区毫米波大规模多输入多输出（MIMO）系统。我们通过联合优化发送远程天线单元（T-RAU）和上行用户的功率分配，以及上下行回程压缩噪声的方差，来最大化加权上下行和速率。针对这一复杂问题，我们进一步应用逐次凸近似（SCA）方法处理非凸的双向有限容量回程约束。仿真结果验证了所提出的基于SCA算法的收敛性，并分析了回程容量与DAC量化对NAFD无小区毫米波大规模MIMO系统频谱效率的影响。此外，通过频谱效率对比得到了一些深刻结论：在有限分辨率DAC的实际场景中，NAFD相比同时间同频率全双工云无线接入网络（CCFD C-RAN）实现了更优的性能增益。具体而言，8-bit DAC量化时的性能差距大于1-bit DAC量化的情况，前者实现了5.5倍的性能提升。