## 7 Results and Comparisons  
The simulation of SES was done in MATLAB (Mathworks Inc., Natick, MA, USA) to compare the performance of modulation, in terms of PSD and bandwidth utilization, between the unipolar, polar, bipolar, and Manchester methods. Firstly, the coordinates of \"x\" and \"y\" were measured using the statistical method to analyze the performance of various line codes as shown in Table 4. The principal of the statistical model is based on mean, mode, and standard deviation to validate the results. The statistical analysis of PSD, which has been performed for SES and other well-known modulation techniques based on the properties of line codes, is given below. The statistical comparison and configuration setup are illustrated in Figure 8.  
* Min =  
Secondly, the SES was also compared with the IoT-based modulation technique Chirp Spread Spectrum (CSS), with the configuration of the LoRA and SigFox communication network that is dedicated to IoT devices in smart cities. A total of 15 data frames were generated in the network between the sender and receiver to calculate the bit error rate (BER). The signal-to-noise ratio (SNR) is also taken in the simulation to compare SES with CSS. The SNR simulation configuration is based on Equation (12), which is taken from [32]. \[\text{SNR (dB)}\approx 20\ \text{log}10\ \text{A}+6.02\text{bits}+9.03r-3.41. \tag{12}\]  
Equations (1)-(5) and (9) have been used to calculate PSD for various line codes. The graphical representation of results for multiple line codes and SES against PSD is shown in Figure 9. It seems that SES utilizes PSD better than the other digital-to-digital encoding schemes. This is because SES does not modulate the signal repeatedly, due to the forwarding of a shadow copy of the same bitstream without performing modulation. Table 4 presents a comparison of the x and y coordinates of SES with the unipolar and polar methods. The total of the \"y\" column for unipolar is 4.264236, and SES's is 4.2587352. SES almost uses the same PSD as unipolar. Unipolar is based on just an +A amplitude with the DC component, and has synchronization issues, while SES is based on different level voltages without synchronization problems. The difference between the two digitizing approaches is only 0.0144992. The difference in PSD between SES and polar is 5.2493118 to modulate a signal. The polar digitizing scheme requires almost 44% more power as compared to SES. Therefore, SES has a better performance in signal modulation. Figure 9: PSD calculation of SES with other digitizing schemes. The Manchester encoding scheme provides a good solution, but it requires double the bandwidth to transmit a bit. During the simulation of Manchester and calculation coordinates, it was determined that it needed extra energy for bits modulation. Table 5 shows the \"x\" and \"y\" coordinates of the Manchester and bipolar encoding schemes. The Manchester encoding scheme is expensive on the PSD property. The SES requires very low power in comparison to the Manchester coding scheme. The bipolar encoding scheme uses three voltage levels. At the co-ordinate values of x and y, where the total 8.89774 PSD is used by bipolar and SES uses less power spectrum as compared to bipolar. The difference between both digitizing schemes is 4.6190048. The bipolar is required 48% more power for data bits transmission. SES again achieves a better performance than the bipolar digitizing scheme. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**SES Signal**} & \multicolumn{2}{c}{**Unipolar Signal**} & \multicolumn{2}{c}{**Polar Signal**} \\ \hline
**x** & **y** & **X** & **y** & **x** & **y** \\ \hline
0 & 0 & 0.05 & 0.4959 &  
Figure 10 shows the PSD comparison of selected digitizing schemes in a line graph. It has been observed that SES used PSD better than the other digitizing schemes. SES utilizes less bandwidth because the shadow copy of the same previous bitstream is transferred, rather than the original stream of bits.