A detailed review of cellular generations is done with respect to fronthauling (FH) with the existing and upcoming key communication technologies. The journey of FH from migration to functional split as per the requirements of 5G and beyond is detailed with the standardized communication network technologies. In concern to efficient utilization of frequency spectrum; cost and time, the millimeter-wave (MMW) over fiber techniques are studied and further its great contributions to passive optical network (PON) technologies are highlighted with several features and limitations. In this paper, the MMW over next generation-PON stage-2 (NGPON2) is described to match the FH network requirements under the International Telecommunication Union (ITU-T) G.989. For better clarity and understanding, the numerical simulations of MMW over NGPON2 are presented and discussed in the scenario of eight wavelengths for both asymmetric and symmetric networks. The detailed state-of-the-art comparisons are presented and found that the MMW over NGPON2 is a good candidate for the 5G and beyond FH network. With the concern of future 5G FH networks, the advanced modulation technique 4-phase amplitude modulation (4-PAM) is studied by utilizing the MMW at 28 GHz. A revolutionary concept that can improve NGPON2 performance, spectrum efficiency, and signal capacity is the 50G-based conjunction of 4-PAM and MMW which presents the innovative idea for FH. To support the literature, the working of the 50Gbps-based 4-PAM network and results have been discussed in detail under the standard ITU-T G.9804. Another aspect of this appraisal is also highlighted to discover the way to explore the future directions.

针对前传 (FH) 以及现有和即将推出的关键通信技术，对蜂窝各代进行了详细审查。通过标准化的通信网络技术，详细描述了跳频从迁移到按照 5G 及更高标准的要求进行功能拆分的过程。关注频谱的有效利用；考虑到成本和时间，我们对光纤毫米波 (MMW) 技术进行了研究，并进一步强调了它对无源光网络 (PON) 技术的巨大贡献，并强调了其几个特点和局限性。本文描述了下一代 PON 第 2 阶段 (NGPON2) 上的毫米波，以满足国际电信联盟 (ITU-T) G.989 下的 FH 网络要求。为了更好地清晰和理解，在非对称和对称网络的八个波长场景中介绍和讨论了 NGPON2 上的毫米波的数值模拟。详细的最新技术比较显示，NGPON2 上的毫米波是 5G 及超跳频网络的良好候选者。着眼于未来5G FH网络，利用28 GHz毫米波研究先进的调制技术四相幅度调制（4-PAM）。4-PAM和MMW基于50G的结合是一个能够提高NGPON2性能、频谱效率和信号容量的革命性概念，它提出了跳频的创新理念。为了支持文献，基于 50Gbps 的 4-PAM 网络的工作原理和结果已在标准 ITU-T G.9804 下进行了详细讨论。此次评估的另一个方面也强调了如何探索未来的方向。