# Investigation of OFDM-Based HS-PON Using Front-End LiFiSystem for 5G Networks
## 3 Results and Discussions
Figure 10 shows that the logarithmic BER value decreases down to \(-20\) whenever the detection area exceeds 1.5 cm\({}^{2}\). As shown in Figure 10a, even at high data rates of 50 Gbps, the BER falls within the range of approximately \(10^{-9}\) to \(10^{-20}\) when the surface area ranges between 1.5 and 4 cm\({}^{2}\). Similarly, for UP transmission signals, the BER ranges from \(10^{-9}\) to \(10^{-20}\), which offers better performance than other ranges do, as shown in  
Figure 9: Tx and Rx angle versus BER performance of different frequency signals in (**a**) DN and (**b**) UP transmission; insets: corresponding Lambertian patterns. Also, for both DN and UP transmissions, on a 4 cm\({}^{2}\) detection surface area, a fine eye opening is observed. For LiFi systems with fixed transceivers, the Tx and Rx must be properly coordinated, which has several advantages [37]. The plots in Figure 11a,b show the BER performance versus the varied LiFi channel ranges with fixed 10 km fiber ranges in DN and UP directions, respectively. When LiFi channel ranges increase from 10 to 20 m, logarithmic BER values increase from \(-10\) to \(-3\) for DN and from \(-10.5\) to \(-3\) for UP transmission signals. As the transmission range increases, the model BER performance increases for all transmission signals. This trend is due to the presence of LiFi channel impairments like channel noise and misalignments, which increases the disturbance as the range increases. Figure 11: LiFi range versus BER performance for (**a**) DN and (**b**) UP transmission; insets: corresponding eye patterns. Figure 10: Detection surface area versus BER performance of different frequency signals in (**a**) DN and (**b**) UP transmission; insets: corresponding eye patterns on 4 cm\({}^{2}\) surface area. LiFi ranges of up to 20 m can be achieved using DN and UP transmission signals with BERs as low as \(10^{-3}\), as illustrated in Figure 11a,b. Marginally better performance is also offered by UP transmission signals compared to DN transmission signals. Furthermore, it is observed that eye patterns at 10 m transmission ranges are wider and more open than those at 20 m transmission ranges in both directions. For shorter transmission ranges, distinct DN and UP signals are observed as a clearer and wider eye opening than that for longer transmission ranges because the signals become less distorted by the generated noise. When signals are transmitted over a distance of 20 m, the eye pattern becomes thicker, indicating distorted signal quality. Table 3 indicates the 3D and 2D BER patterns of the proposed model over various LiFi channel ranges with a fixed 10 km fiber at a 50 Gbps data rate. These patterns revealed that continuous and regular BER patterns are obtained ina 10 m range followed  
Table 4 indicates the performance evaluation of the proposed model over a 10 km SMF and a 10 m LiFi range at a 50 Gbps data rate. The evaluated performance metrics include the gain, noise figure, SNR, and optical SNR, as given in expressions (20)-(22). Table 5 illustrates the comparative analysis of existing methods. It shows that a high-speed full-duplex hybrid fiber-LiFi in a hybrid PON/LiFi model provides superior performance for multi-users. As shown in the table, the prior work used three LEDs over 1.6 m to achieve a 15.73 Gbps data rate [39]. Previous work did not include fiber links. Compared to previous work, our proposed solution uses blue LEDs to offer 20 m LiFi communication at a rate of 4 \(\times\) 50 Gbps on a 100 km fiber. Based on this, it becomes evident that the proposed model provides a high data rate, high bandwidth, scalability, flexibility, reliability, and easy upgradeability to next-generation optical networks. It is crucial to consider the trade-offs