## 6 Conclusions and Final Discussion
The amount of profit will depend heavily on the selection of the IF subcarrier in relation to the selected optical channel width from the grid of the next generation of EON/UDWDM networks. In the scenario examples we did not use the D-RoF digital indirect interface type eCPRI Split I\({}_{\text{U}}\)/II\({}_{\text{D}}\)--Figure 7. In this interface there is a strict dependence of the final FH/MH link bandwidth on the BB channel width and the number of active CP-OFDM sub-carriers--Figure 11. In the eCPRI Split D (Option 6) interface, the fronthaul/midhaul link rate depends only on the number of active CP-OFDM sub-carriers. Considering that in the 5G-NR wireless interface the frequency distance between the CP-OFDM subcarriers increases faster than the number of subcarriers themselves, therefore with the increasing BB channel width the eCPRI Split I\({}_{\text{U}}\)/II\({}_{\text{D}}\) interface will become increasingly less efficient with A-RoF (profit results will be between scenarios 1-2, 3-4, and 5-6 respectively). Some of the issues related to the influence of the optical path or fiber-optic link on the behavior of the wireless radio channel has already been addressed in sub-Section 3.2. However, to a large extent these issues are not covered by the topic of this paper. It can be assumed that an all-optical path/link guarantees the stability of the delay. The amount of delay depends on the optical path length or link. This parameter, however, seriously affects the work of the DBF or HBF (regardless of the method used [54]), which requires conducting many calculations and practical tests in any implementation of subsequent C-RAN solutions. This applies to both the D-RoF format and the A-RoF format. With the narrowing the spatial beam on the side of the wireless link (massive MIMO), a faster feedback in the DBF control channel with the update of channel state information (CSI) data is needed--especially in the fast-moving UE. The use of HBF is helpful here, since the instant compensation resulting from the delay of the wired RAN part can be implemented with the ABF support. Interferences that can occur between adjacent cells or sectors can be reduced by allocating other physical resource blocks (PRBs) (time-frequency isolation). In the case of sectors belonging to the same gNB-DU/RRH or gNB-CU and spaced apart, interference is even indicated due to the constructive spatial surrounding of the UE. Time-space synchronization in the area of the distributed base station ensures the implementation of joint transmission (JT) and high spatial gain. By means of an antenna-array consisting of a large number of modules, a very narrow beam can be radiated, thanks to which the channel will be resistant to multi-path. In the optical path or fiber-optic link, the previously mentioned phenomenon of chromatic dispersion has a static character. During the DSB transmission, a relative delay of the side bands occurs, in which there is a signal coming from the wireless channel. CP-OFDM symbols are protected against this phenomenon by inserting a guard interval with a cyclic prefix. The optical path enhances the multi-path phenomenon, but it is a constant parameter that can be quickly determined and compensated by the exchange of CSI. The compensation of optical fiber chromatic dispersion can also be implemented permanently at the end of the optical path/link, which will ensure a constant minimization of the impact on the transported radio channel signal in the target format. The radio signal transported in the optical path in analog format is also influenced by noise. The main source of noise are the radio-photonic converters. The noise factor (NF) of the converter therefore decides on the extent of reduction of the SNR and indirectly influences the BER in the user channel. Optical power density should also be controlled due to the potential effect of nonlinear distortions. This is a price that in many cases is worth paying for a significant profit resulting from the compression of the used optical spectrum in the optical path/link.