Advances in fronthauling of communication technologies: A review

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 stateof-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.