## 6 Conclusions and Final Discussion
Therefore, it is very important to introduce new solutions, among which one should reduce the throughput by introducing new Splits/Options. Figures 10 and 11 show the calculation results for two selected eCPRI interface splits, where we see a very large drop in the demand for bit-rate. This is done at the expense of the need to perform more operations in the antenna-radio terminal, but the profit is significant, because the demand for bit-rate at the maximum values of the radio signal balances around 1 Tbps. This is associated with the occupancy of an acceptable number of optical DWDM/UDWDM channels in the fronthaul/midhaul optical path. In order to increase the transparency of the potential application of the presented solutions, some exemplary scenarios (Section 5) are given in which the transition from the D-RoF format to the A-RoF format is suggested. The basic scenarios constitute the merits of undertaking the research topic, as they show the direction of the RAN network evolution along with the increase in the use of fronthaul/midhaul links for this purpose, as well as the signal processing centers. Detailed scenarios are examples in which a specific D-RoF interface can be replaced with the A-RoF interface due to a smaller occupancy of the optical band in the fronthaul/midhaul link/path. Scenario No. 1 concerns the comparison of BBoF and CPRI interfaces that work at the same split level--Table 3. When using the BBoF optical channel with the minimum width matched to the modulation signal band, the gain is almost 24-fold. Scenario No. 2 shows a comparative overview of BBoF interfaces (Option 8) and eCPRI (Option 6)--Table 4. The eCPRI interface uses the fact that the so-called layers are most often associated with the number of radiated beams by use of DBF or HBF method. A large part of operations related to processing a radio signal is transferred to the gNB-DU/RRH. In this case, the gain for the optical UDWDM channel (1.5625 GHz) is over 19, while for the DWDM channel (12.5 GHz) only 2.4. In this example, it is clearly visible what effect the channel width has on the optical bandwidth saving, which is a serious technological limitation in the production of tunable lasers, photonics switches, and filters used in PXC/ROADM. Scenario No. 3 concerns the comparison of RFoF (Option 10) and CPRI (Option 8) interfaces--Table 5. In this comparison it is difficult to find a profit which for example BB 100 and 400 MHz channels shows losses. It should be added, however, that the RRH/AAU in the case of RFoF is almost completely unloaded from the signal processing. Here, even the RF carrier is built on the SPC/CU side. The calculations were carried out assuming a separate transfer of the BB channel with the RF carrier. If we send more BB channels on one RF carrier, then the profit will be significant, but we will limit the possibilities of independent beamforming in particular BB ranges. We eliminate this problem in the next scenario. Scenario No. 4 includes the technique of creating layers that manage beams. Here we compare the RFoF (Option 10) and eCPRI (Option 6) interfaces--Table 6. The situation is similar, because there is no profit here or there is a loss. Therefore, the situation is similar to scenario 3, and the significant difference in the occupation of the optical band between the scenarios results mainly from the compression consisting in the BB encoding in the layer-related stream. Scenario No. 5 concerns the comparison between IFoF (Option 9) and CPRI (Option 8)--Table 7. The introduction of the IFoF format for the 100 MHz BB channel gives about 3.3-fold gain on the optical FH/MH band. At the 400 MHz BB channel, the profit is already 6 times. In the case of the introduction of the BB channel multiplexing technique around IF subcarriers, the gain can be improved [53]. Scenario No. 6 shows the comparison of IFoF (Option 9) and eCPRI (Option 6) interfaces, also for 2 sample BB channel widths--Table 8. For both cases, we have a similar gain of around 3.