if you want begin with 5G concepts and it relations with FWA an Non-3GPP networks I recomended the 5G Cicle video in: https://www.youtube.com/playlist?list=PL0QSAEWH0x_hBjTjob2z9sdaXeWP_oMTP
I see the use of the ideas of SDN (Software Defined Networking) and Digital Twins in Mobile Wireless Networks as a very topical and interesting research topic with regard to future 5G and 6G mobile networks. So I would suggest the following topic:
Digital-Twin-Enabled and Software Defined Wireless Networks
My literature sources are intended to give you an introduction to the proposed topic.
General idea of DTs fill my figures at the address
Huan X. Nguyen, Ramona Trestian, Duc To, Mallik Tatipamula: Digital Twin for 5G and Beyond; IEEE Communications Magazine, Vol. 59(2), Feb 2021; DOI: 10.1109/MCOM.001.2000343
Latif U. Khan, Walid Saad, Dusit Niyato, Zhu Han, Choong Seon Hong: “Digital-Twin-Enabled 6G: Vision, Architectural Trends, and Future Directions”; arXiv:2102.12169v1 [cs.NI] 24 Feb 2021
https://arxiv.org/abs/2102.12169
Xiaohu You, Cheng-Xiang Wang, Jie Huang, Xiqi Gao, et al.: Towards 6G wireless communication networks: vision, enabling technologies, and new paradigm shifts; Science China Information Sciences, Vol. 64, Article number: 110301, Jan 2021; DOI: 10.1007/s11432-020-2955-6
Jesús Antonio, Puente Fernández, Luis Javier García Villalba , Tai-Hoon Kim: Software Defined Networks in Wireless Sensor Architectures; Entropy 2018, 20, 225; doi:10.3390/e20040225