# Investigation of OFDM-Based HS-PON Using Front-End LiFiSystem for 5G Networks
## 3 Results and Discussions
[31; 32; 33] with a channel capacity of 2 \(\times\) 4.2 Gbps [31], 3 \(\times\) 1 Gbps [32], and 2 \(\times\) 5.2 Gbps [33], the proposed HP-PONs/LiFi system exploits a significant amount of optical beams to offer greater capacity as well as more flexibility for end users at a symmetric and bidirectional data rate of 4 \(\times\) 50 Gbps. This approach has acquired considerable attention from industry and academia [34]. Figure 8a,b illustrate the model's BER performance versus its throughput for DN and UP transmission over LiFi channels, respectively. Signals transmitted uplink perform slightly better than signals transmitted downlink. A maximum transmission data rate of 50 Gbps can be achieved at a BER limit of \(10^{-3}\). Additionally, the BER values increase as the channel throughput increases. The minimum BER for DN and UP transmissions is \(10^{-20}\) (187.5 THz) and \(10^{-22}\) (195.3 THz), respectively. In Figure 8a,b, the eye patterns for different DN and UP transmitted signals are more open at low throughputs, while at high throughputs of 50 Gbps, they are acceptable. This proves the feasibility of the proposed model at a high throughput. DN transmission signals, however, become more closed from 10 Gbps to 50 Gbps per channel, compared with UP  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Range (km)** & **HS-PON** & **LiFi** \\ \hline
**100** & **187.3T** & **187.6T** & **187.9T** \\
**188.2T** & **188.2T** & **188.2T** & **666.2T** \\
**18  
transmission signals. The most prominent degradation factor of hybrid PON/LiFi systems is the fiber inter-symbol interference and LiFi channel disruptions. Hybrid fiber-LiFi link technology is therefore promising because it can significantly enhance reliability and availability compared to individual channels, as well as providing adaptive solutions for high-throughput LiFi connectivity, transmission rates, and insensitivity to channel impairments [35]. Figure 9a,b present the achieved BER for different irradiance and incidence half-angle values for DN and UP transmission signals, respectively. The transmitter half-angle is set at 60\({}^{\circ}\), while both the irradiance half-angle and incidence half-angle vary equally from 10\({}^{\circ}\) to 50\({}^{\circ}\). In the case of indoor wireless communication via a LiFi medium, the performance of all transmission signals degrades as the angle increases. For downlink and uplink transmission, the lowest BER can be obtained as 10\({}^{-12}\) (187.6 THz) and 10\({}^{-13}\) (195.4 THz), at a 10\({}^{\circ}\) irradiance half-angle and 10\({}^{\circ}\) incidence half-angle, respectively. The logarithmic BER value increases from \(-12\) to \(-3\) for DN and \(-13\) to \(-3\) for UP transmission signals as angles increase from 10\({}^{\circ}\) to 50\({}^{\circ}\). Figure 9 also indicates the LiFi illuminance distribution in a 10 \(\times\) 10 \(\times\) 10 m sized room. Illuminance levels are highest in the center of the room, while they are significantly lower in the corners. A number of factors influence the illumination of an LED, including its location, field of view, orientation, output power, emission patterns, color temperature, bandwidth, etc. [36]. According to the results, the SNR in a directed path decreases with an increasing irradiance and incidence angle. As a result, Lambertian patterns have limited performance but large coverage areas. However, at an angle of angle, the SNR value is high, which means improved system performance in terms of an extended communication range and limited coverage area. Figure 10a,b illustrate the BER performance of DN and UP transmission signals over a 10 km fiber and 10 m wireless range for the varied detection of surface areas of LiFi channels. Based on these plots, we can conclude that the detection surface area is still highly dependent on the system's performance. Multiple transmission signals can be received with greater power due to the increased surface area of LOS communication.