## 5 Applications of the Proposed Solutions  
All the solutions proposed in the work above can be applied in developing mobile communication and wireless access systems. The main destination is the RAN domain, whose architecture evolves strongly towards C-RAN. The result is a search for solutions that will allow for an efficient transmission of processed radio signals to maximally simplified radio modules. The presented concept of the network (Figure 5) is an unavoidable step that will allow virtualization of the computing power needed for the processed signals. The proposal for construction of the gNB-DU/RRH and coexistence of A-RoF and D-RoF links/paths in the same network is a combined approach to the solution that will enable dynamic management of optical resources of the fronthaul/midhaul, available cheap CU computing power, and radio resources. Basic application scenarios for fronthaul/midhaul C-RAN networks (we assume that optical network (ON) and signal processing center (SPC) provide many other services to other recipients) are the following:  
1. ON is heavily loaded, and SPC has a lot of free computing power resources. In this case, we can afford cheap signal processing even to the A-RoF. The A-RoF signals in most cases represent a high degree of spectral compression, so it will not be heavily loaded the ON links. 2. ON has a lot of free resources, and SPC is heavily loaded with other services. In this case, we can go to D-RoF modes, that is, lower the level of the split to the ceiling enabling the operation of the gNB-DU/RRH (even to Option 6 (eCPRI)--Figure 7). 3. Both ON and SPC are not overloaded. A case in which the D-RoF with Option 8 (CPRI) support may be enabled--Figure 7.
4. Both ON and SPC are heavily loaded. This is a very uncomfortable situation, because RAN has to go into the D-RAN mode, where the gNB-DU/RRH turns into the function of a classic gNB. A base station that does not have too much computing power and have limited access to the optical network must limit the supported wireless traffic. Scenarios of detailed applications enabling switching the format in the fronthaul/midhaul link of the C-RAN (comparison with reference to the bandwidth in FH/MH links/paths of optical networks, without analyzing the demand for computing power during signal processing to the target form) are as follows:  
1. The A-RoF and D-RoF interfaces on the same level of Option 8 (Figure 7), i.e., CPRI and BBoF. The comparative calculations are shown in Table 3.  
2. The A-RoF and D-RoF interfaces located at different levels of split (Figure 7), i.e., eCPRI and BBoF. Comparative calculations are shown in Table 4.
3. The A-RoF and D-RoF interfaces located at different levels of split (Figure 7), i.e., CPRI and RFoF. Comparative calculations are shown in Table 5.
4. The A-RoF and D-RoF interfaces located at different levels of split (Figure 7), i.e., eCPRI and RFoF. Comparative calculations are shown in Table 6.
5. The A-RoF and D-RoF interfaces located at different levels of split (Figure 7), i.e., CPRI and IFoF Comparative calculations are shown in Table 7.
6. The A-RoF and D-RoF interfaces located at different levels of split (Figure 7), i.e., eCPRI and IFoF. Comparative calculations are shown in Table 8. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Interface** & **BB** & \
\begin{tabular}{c} **Optical** \\ **Channel BW** \\ \end{tabular} & **OWS** &
\begin{tabular}{c} **Number of** \\ **Optical Channels** \\ \end{tabular} & **RF Carrier** & **Layers** & **Format/Split** \\ \hline - & (MHz) & (GHz) & (nm) & - & (GHz) & - \\ \hline RFoF & 100 & 12.5 & 0.9353 & 8 & 3.6 & 8 & A-RoF/Option 10 \\ eCPRI & 100 & 50 & 0.9351 & 2 & - & 8 & D-RoF/Option 6 \\ eCPRI & 400 & 50 & 1.4022 & 2 & - & 4 & D-RoF/Option 10 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Calculated comparative parameters for detailed scenario No. 4 to switch from D-RoF to A-RoF format (the optical channel count-down is starting from wavelength equal to 1675 nm)—Figures 10 and 12 (32-element antenna-array and 4-sector unit).