## 8 RAN Decomposition Scheme  
As stated earlier in Section 2.2, the ever-increasing network demands are becoming challenging to the current mobile networks. Good instances of this are the inability of the existing mobile network to match the performance of the modern fiber-based broadband systems regarding the latency and download speed [6; 249]. Based on this, there have been concerted research efforts and collaboration in the academia and telecommunication industry with both sectors giving apt attention to the 5G network with notable interests in the adoption of the small-cell concept. Apart from the densely deployed small-cell, there are other advanced technologies such as mm-wave, HetNets, massive MIMO, SDN/NFV, energy harvesting, multi-carrier modulation, and flexible spectrum management that have been researched for efficient implementation and deployment of 5G and beyond technologies. The networks are envisaged not only to offer wireless communications, but  
Figure 25: PON system coexistence (adapted from the work in [143]).  
also to support network slicing (Netsli), massive connectivity, and tactile internet with reasonable QoS. The required massive connectivity demands ultra-dense networks that are capable of offering advantages such as better frequency reuse, seamless coverage, and gigabit-per-second user experience with significant improvements in energy efficiency. Moreover, for effective management of the evolving complexity, due attention has been given to the C-RAN. This is owing to its valuable attributes regarding scalability, higher SE, cost-effectiveness, lower energy consumption, multiple technology support, network virtualization, easier network management, and operation. Besides, the C-RAN architecture offers considerable flexibility in the deployment of RRHs away from the BBU pool compared with the traditional RANs [47].  
Furthermore, as previously mentioned, in Section 6, the predominant means of connecting the BBU pool and the RRHs for baseband sample distributions over the C-RAN fronthaul networks are through the CPRI specifications. However, as expatiated in Section 8.1, CPRI-based links have associated stringent requirements, which could make them impracticable for future mobile networks. As the networks are anticipated to support schemes such as CA, massive heterogeneous devices, and multi-band along with the integration of technologies such as massive MIMO antennas and mm-wave.  
In this part of the tutorial, we evaluate and simulate required bandwidth by the conventional CPRI-based fronthaul for supporting different system bandwidths and antenna ports in the 5G wireless network considering typical transmission parameters specified by the 3 GPP. Furthermore, we consider some viable FSOns that are capable of relaxing the transport network constraints. In accordance with the 3 GPP WG3 5G assumptions, we evaluate and simulate the UL transmission bandwidth requirements for the considered FSOns. In addition, the implications of different FSOns on the FWA transport network are considered. Moreover, we present a high-level concept of vRANs with PTN for attending flexibly to the dynamic nature of different use cases by exploiting an open PTNI that is capable of supporting multi-vendor interoperability and PS adaptation. This will enable dynamic FSOns with efficient load management and real-time performance optimization. Furthermore, the proposed architecture can use Netsli to offer an on-demand resource provisioning with optimal utilization based on context-aware service delivery. Cost-effective architectural variants that can offer relatively simplified DU designs with a low footprint are also presented.