## 3 O-RAN with 200 m FSO Link
### The 200 m FSO Link Backhaul for O-RAN with 10 km Fronthaul for Outdoor Network  
The results depicted in Figure 11 illustrate the network performance evaluation of the O-RU antenna over a 10 km fiber-optic fronthaul, directly supplying the cellular network or via CPE. In comparison to the schematic in Figure 6, the actual configuration in Figure 11 entails the transmission of the network from the FSO device at the ITB to the FSOs at the EB through a switch, followed by forwarding to the O-RAN and fronthaul to the O-RU antenna using a 10 km fiber. The O-RU antenna at the EB can establish connectivity with the cell phone or CPE at the ITB bal colony through a 200 m transmission accessibility field for cell phone connectivity. In addition, in the test where the cell phone connects to the network through the CPE with sampling every minute, the distance between the cell phone and the CPE was 1 m, and the CPE was more than 2 m above the ground to avoid being blocked by the bal colony wall and aligned with the O-RU antenna. Based on the downlink throughput, it is apparent that whether the cellular device was directly linked to the O-RU antenna or connected to the O-RU antenna via the CPE, the outcomes closely resemble those of the fronthaul when utilizing only a 4 m optical fiber. Similarly, the jitter and ping measurements demonstrate strong similarity to the fronthaul scenario using only 4 m of fiber. Furthermore, the uplink throughput of the O-RU antenna directly connected via cell phone was notably inferior than the throughput of the 4 m fronthaul scheme due to the path loss and lower power of the cell phone. The uplink throughput of the O-RU antenna via CPE was better than that of the 4 m fronthaul scheme and also better than that of the cell phone directly connected to the O-RU antenna, which is due to the matching of the pointing of the O-RU antenna with the CPE and the higher power of the CPE. It is worth noting that the measurements shown in Figure 11 illustrate that the variability in throughput was significantly reduced when transmitting through the open-air field compared to an indoor corridor. This reduction is due to the significant decrease in the impact of multipath effects. A single data measurement aligns with the values displayed in Figure 11 for the 10 km  
Figure 10: O-RU utilizes a 4 m fronthaul via CPE for cell phone network performance measurement. (**a**) shows uplink throughput; (**b**) shows downlink throughput; (**c**) shows jitter; (**d**) shows ping. The box-and-whisker plot uses 25% fractions and 75% fractions, and coef is 1.5.  
fronthaul solution scenario; this measurement was taken when the cell phone and CPE were positioned near the O-RU antenna without FSO transmission. To test the network performance limit, the same measurement structure as the results in Figure 11 was used, except that the distance between the cell phone and CPE was extended to 20 m and 40 m for single-data measurement. It was found that the 20 m and 40 m cases match the results in Figure 11, except that the uplink throughput in the 40 m case dropped to 45.7 Mbps. The measurement results and configuration aspects discussed in Section 3 indicate that the influence of FSOs as a backhaul and 10 km fiber as a fronthaul on network transmission appears to be minimal. The performance of the O-RAN is contingent upon its specific configuration [35]. The measurement outcomes of this study align closely with the test data provided by the O-RAN equipment vendor, and the internal configuration of the O-RAN is identical. The observed degradation in network performance can primarily be attributed to the potential misalignment of antennas and user devices, the multipath effect arising from the constraints of the measurement environment, and the operational range of user devices, such as CPE. Furthermore, while the beamforming configuration presented in this study operates independently of the O-RAN antenna unit, recent research has indicated the potential viability of integrating O-RAN antennas with beamforming technology [36, 37].