# A Novel Signal Design and Performance Analysis in NavCom Based on LEO Constellation
## 4 Performance Evaluation
### Communication Performance Analysis  
As a verification indicator for the NavCom signal, the communication link budget between the LEOs and the terminal is extremely critical and the required parameter settings are shown in Table 2. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Indicator** & **Symbols** & **Values** \\ \hline Carrier frequency range & \(f\) & 2483.5–2500 MHz \\ Carrier center frequency & \(f\) & 2491.75 MHz \\ Carrier wavelength & \(\lambda\) & 0.12 m \\ Bandwidth & \(B\) & 16 MHz \\ \hline \hline \end{tabular}
\end{table} 
Table 2: List of parameter settings. Figure 19: Histogram of anti-jamming level among proposed signal, BPSK (1), BPSK (4), BOCs (5, 2), BOCs (5, 2.5), and MSK (10). The dark red bar shows significantly stronger anti-jamming for the matching spectrum (Dem and AJMS) merit factor and anti-narrowband jamming (Dem and AJNW) merit factor in the demodulation process than other bars, and the code tracking is resistant to the matching spectrum interference (CT and AJMS) merit factor, which is slightly stronger than the others and significantly lower than the others in the code tracking anti-narrowband jammer (CT and AJNW). Our proposed signal has better comprehensive anti-interference characteristics. According to the parameters shown in the above list, assuming that the propagation channel model is a free space model, the transmission loss can be estimated as follows:  
\[ \begin{array}{ll}L_{0}&=32.45+20\cdot\log(f)+20\cdot\log(D)\\ &=32.45+20\cdot\log(2491.75)+20\cdot\log[(500\sim 1000)\times 2.2]\\ &=32.45+67.93+20\cdot\log[(500\sim 1000)\times 2.2]\\ &=100.38+(60.83\sim 66.85)_{dB}\\ &=(161.21\sim 167.23)_{dB}\\ \end{array} \]  
For the uplink from the ground terminal transmitter to the LEO receiver, the bit signal-to-noise ratio can be estimated as:  
\[ \begin{array}{ll}E_{b}/N_{0}=&EIRP-(L_{0}+L_{s})+(G_{r}/T)_{dB}-(k)_{dB}-1 0\cdot\log(R_{b})\\ &=\ (11+3)-L_{0}-1-6.5+228.6-10\cdot\log(64,000)\\ &=13\ \ -L_{0}-6.5-48.06+228.6\\ &=187.04\ \ -L_{0}\\ &=187.04\ \ -[161.21\sim 167.23]_{dB}\\ &=[19.81\ \sim 25.83]_{dB}\\ \end{array} \]  
Using Figure 20 as an input, an LEO satellite with an orbit height of 600 km and an orbital inclination of 45\({}^{\circ}\) was constructed through simulation verification by STK 11.6, named WuhanSat001. The ground station, named WHUT-FIXED, was set as a longitude of 114.367022\({}^{\circ}\) E, the latitude was 30.544342\({}^{\circ}\) N, the altitude was 27.1 m, and the transmitter and receiver were established on the satellite and ground station, respectively. The simulation was performed as shown in Figures 20 and 21. Figure 21: Two–dimensional diagram of the parameter settings. The red solid line represents the orbital area covered by the ground fixed transmitter in the set conditions, while the yellow area denotes the satellite transmitter coverage for the Earth’s surface. Figure 20: Three-dimensional diagram of the parameter settings. Via STK 11.6 simulation for the above-mentioned parameters, the signal transmitted by the ground station WHUT-FIXED shows that the standard received power on the satellite is \(-\)152.917 dBW, while the carrier (signal) power/noise spectral density is about 69.18 dB-Hz. The carrier/noise ratio is about 6 dB, the bit signal-to-noise ratio is 21.12 dB, and the bit error rate is maintained at an ultra-low level of 1 \(\times\)10\({}^{-30}\). This means that the uplink tradeoff performed remarkably in all the above parameters. From Figure 22, it is obvious that, under the simulation conditions, the BER is 1 \(\times\) 10\({}^{-30}\) in the uplink, which is far better than the threshold of 1 \(\times\) 10\({}^{-6}\). Additionally, \(E_{b}/N_{0}\) has a redundancy of 18.4299-29.2671 dB and \(C/N\) has a redundancy of 3.4814-14.3186 dB.