## 4 Results and Discussion
### SCs Type 1, 2, and 3  
The same procedure reported in Section 4.1 was repeated for different type of SCs, the analysis is repeated while changing SCs and the number of channels adjusted to fit the DAC sampling rate of 12 GSa/s. The parameters and obtained results are summarized in Table 2.  
The electrical spectrum of SCs type 1 for \(n=36\), 2 for \(n=18\), and 3 for \(n=9\) NR channels at the input of RX DSP obtained by FDMA and TDMA aggregation is shown in Figures 7-9, respectively. The red line is used for FDMA and the blue line is used for TDMA. The total bandwidth occupied by FDMA is obtained as \(n\times\) sampling rate of each NR channel = \(\sim\)4700 MHz (including 300 MHz guard from DC) for all SCs types. Instead, the total bandwidth occupied by TDMA is \(n\times\) bandwidth (BW) of each NR channel = \(\sim\)3600 MHz for all SCs types. Hence, TDMA saves \(\sim\)1.1 GHz bandwidth when compared with FDMA for the same number of channel aggregation and SCs, as described in Table 2. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameters** & **Type 0** & **Type 1** & **Type 2** & **Type 3** \\ \hline \(n\) & 72 & 36 & 18 & 9 \\ BW of each NR channel (MHZ) & 50 & 100 & 200 & 400 \\ Sampling rate of each NR channel (MSa/s) & 61.44 & 122.88 & 245.76 & 491.52 \\ Total BW TDMA (GHz) & 3.6 & 3.6 & 3.6 & 3.6 \\ Total BW FDMA (GHZ) & 4.72 & 4.72 & 4.72 & 4.72 \\ BW TDMA \(-\) BW FDMA (GHz) & \(\sim\)1.1 & \(\sim\)1.1 & \(\sim\)1.1 & \(\sim\)1.1 \\ Optimum Clipping Ratio & 12 dB & 12 dB & 12 dB & 12 dB \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Summary of parameters and results for different types of SCs. BW—bandwidth; TDMA—time division multiple access; FDMA—frequency division multiple access. Figure 6: Mean EVM vs. ODN loss for 72 NR (50 MHz) channels at 12 dB clipping. (**a**) PUCCH; (**b**) PUSCH. Figure 8: Power spectral density of aggregated 18 NR (200 MHz) SCs type 2 channels at the receiver DSP input obtained at 20 dB ODN loss. Figure 7: Power spectral density of aggregated 36 NR (100 MHz) SCs type 1 channels at the receiver DSP input obtained at 20 dB ODN loss. The clipping optimization for SCs type 1 for \(n=36\), 2 for \(n=18\), and 3 for \(n=9\) NR channels on both signal types (PUCCH and PUSCH) at 29 dB ODN loss is shown in Figure 10a,b, Figure 11a,b and Figure 12a,b, respectively. The optimum clipping ratios for both signal types, DSP aggregation techniques, and all SCs types are obtained as 12 dB, as described in Table 2.  
Figure 10: Clipping optimization for 36 NR (100 MHz) channels at 29 dB ODN loss. (**a**) PUCCH; (**b**) PUSCH. Figure 9: Power spectral density of aggregated 9 NR (400 MHz) SCs type 3 channels at the receiver DSP input obtained at 20 dB ODN loss. The EVM (mean) as a function of the ODN loss for SCs type 1 for \(n=36\), 2 for \(n=18\), and 3 for \(n=9\) NR channels evaluated at the optimum clipping for PUCCH and PUSCH is reported in Figure 12(a,b), Figure 13(a,b), and Figure 14(a,b), respectively. The mean EVM performance of the TDMA scheme is slightly better at higher ODN loss for both signal types (PUCCH and PUSCH). This is associated with TDMA's spectral compactness when compared with FDMA, which is less affected by the optical channel response towards the higher channels, and the maximum reach for each case is summarized in Table 2.  
Figure 11: Clipping optimization for 18 NR (200 MHz) channels at 29 dB ODN loss. (**a**) PUCCH; (**b**) PUSCH. Figure 12: Clipping optimization for 9 NR (400 MHz) channels at 29 dB ODN loss. (**a**) PUCCH; (**b**) PUSCH. Figure 6:0 Mean EVM vs. ODN loss for 36 NR (100 MHz) channels at 12 dB clipping. (**a**) PUCCH; (**b**) PUSCH. The decoded constellation after channel equalization on the ninth NR (400 MHz) SCs type 3 channel is shown in Figure 6:1 Figure 16a,b show the receive signal constellation of PUCCH at EVM = 6% and PUSCH at EVM = 7.5%, respectively, obtained using FDMA. Figure 16c,d show the receive signal constellation of PUCCH at EVM = 5.5% and PUSCH EVM = 6.5%, respectively, using TDMA 29 dB ODN loss.