Cell-free massive MIMO (CF-mMIMO) network and its user-centric (UC) version are considered as promising techniques for the next generations of wireless networks. However, fronthaul and backhaul assignments are challenging issues in these networks. In this paper, energy efficiencies of uplink transmission for the CF- and UC-mMIMO networks are studied, wherein access points (APs) are connected to aggregation nodes (ANs) through radio frequency (RF) and/or free-space optic (FSO) fronthauls, and the ANs are connected to a central processing unit via fiber backhauls. The achievable data rates are derived by taking into account the effects of hardware non-ideality at the APs and ANs, FSO alignment and weather conditions. To have a robust and energy-efficient network, especially in the presence of FSO misalignment and adverse weather conditions, firstly, a cognitive RF--FSO fronthaul assignment algorithm is proposed at the cost of sharing the available RF bandwidth between the access and fronthaul links. Then, optimal power allocations at the users and APs are investigated, and two analytical approaches are proposed to solve the non-convex optimization problem. Through numerical results, we have discussed how utilizing the cognitive RF--FSO fronthaul assignment achieves higher energy efficiency compared to that of FSO-only, RF-only, or simultaneously using RF and FSO fronthaul links, e.g., achieving up to $198\%$ higher energy efficiency under unfavorable conditions. Moreover, the effects of FSO misalignment, weather conditions, and power allocations on the performances of the CF- and UC-mMIMO networks are discussed.

翻译：无细胞大型MIM(CF-MMIM)网络及其用户中心(UC)版本被视为对下一代无线网络而言很有希望的技术。然而,Fronthaul和Forthaul任务是这些网络中具有挑战性的问题。在本论文中,研究CF-和UC-MIMIM网络的升级传输链的能源效率,其中接入点通过无线电频率(RF)和(或)自由空间光学(FSO)前厅(FSO)与集合节点(AN)连接,而ANs则通过纤维回流连接与中央处理单位连接。可实现的数据率是考虑到APs和ANs硬件非理想性效应、FSO的匹配和天气条件的影响而得出的。要有一个强大和节能的网络,特别是在FSO的不匹配和恶劣的天气条件下,首先提出认知RF-F-FSO前门分配算法,然后在前端连接和前门链接中分享现有的RFFFRF的节带带带。最佳的电力分配方式,然后在FFFSO上进行分析,然后进行,然后分析,然后分析,然后分析结果,然后分析,然后分析SOSOSO分配如何分配,然后分析,然后分析,然后分析,然后分析,然后分析结果,然后分析,然后分析SOSOAFSO分配如何如何分配。