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)量化与前传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射远程天线单元(T-RAU)与上行用户的功率分配，以及上下行前传压缩噪声的方差，提出最大化加权上下行和速率的方案。针对这一难题，进一步采用逐次凸逼近(SCA)方法处理非凸双向有限容量前传约束。仿真结果验证了所提SCA算法的收敛性，并分析了前传容量与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出重要结论：在实用有限分辨率DAC场景下，NAFD相比同频同时全双工云无线接入网络(CCFD C-RAN)具有更优性能增益。具体而言，8-bit DAC量化时的性能差距显著大于1-bit DAC量化，前者可实现5.5倍的性能提升。