# A Novel Signal Design and Performance Analysis in NavCom Based on LEO Constellation
## 4 Performance Evaluation
### Navigation Performance Analysis
For the 16.5 MHz receiver front-end bandwidth, the gray dashed line corresponding to \(k=2\) has the best Gabor bandwidth, which means that broadband receivers can have better positioning and resolution capabilities, consistent with NavCom. * Compatibility  
Figure 12 shows the SSC between the target modulation signal and single interference modulation signal. The smaller the SSC is, the smaller the interference between the two will be and the easier it will be to separate the target signal. It can be seen from Figure 12 that the SSC of the CE-OFDM-PM-modulated signal has significantly smaller advantages of SSC than the other signals. The scheme proposed in this paper can even reach a value of \(-107.9\) dB/Hz for the SSC of MSK (10) and performs better for BPSK (1) and BPSK (4). Both BOCs (5, 2.5) have spectral separation coefficients greater than or equal to 100 dB/Hz; thus, compared with the other listed modulation signal schemes, this scheme is able to extract and separate signals after mixing. Figure 13 shows the code tracking spectral sensitivity coefficient (CT-SSC) between different spread spectrum modulated signals, which is used to measure the spread spectrum code tracking performance of the interference signal on the target signal under the special code tracking loop discriminator. Normally, the smaller the CT-SSC is, the smaller the influence of the interference signal on the tracking performance of the target signal's spreading code will be. It can be seen from Figure 13 that when the proposed scheme is used as the target signal, the CT-SSC value of other spread spectrum modulated signals is the smallest value in each row of the matrix. As the target signal, the value of the CT-SSC proposed in this article is also the smallest value in each column of the matrix. Therefore, this shows that the solution proposed in this article has a smaller impact on the tracking performance of the target signal spreading code. Other signals have less influence on it. Figure 11: Comparison of code tracking errors with CE-OFDM-PM under the conditions \(k\)= 1, 2, 4, 8. It can be found that the gray dashed line has more advantages in terms of code tracking error. Figure 12: Proposed signals’ spectral separation coefficients compared with BPSK (1), BPSK (4), BCCs (5, 2), BCCs (5, 2.5), SRC (0.2,1), MSK (10), CE-OFDM-PM (1), CE-OFDM-PM (4), and CE-OFDM-PM (8). Obviously, the SSC of our proposed scheme and the above-listed modulation is significantly smaller than that of other spread spectrum signals. Except for CE–OFDM–PM (4) and CE–OFDM–PM (8), which shows that our proposed scheme can easily be compatible with service signals of the same frequency band, while their own compatibility is also remarkable. Figure 13: Proposed signals’ code tracking spectral sensitivity coefficients compared with BPSK (1), BPSK (4), BCCs (5, 2), BCCs (5, 2.5), SRC (0.2, 1), MSK (10), CE–OFDM–PM (1), CE–OFDM–PM (4), and CE–OFDM–PM (8). From the perspective of the row or column, except for CE–OFDM–PM (4) and CE–OFDM–PM (8), regardless of whether our proposed signal is a jammer or desired signal, its interference with other signals or the influence of other jammers is very small. Additionally, this indicates that the proposed signal has an outstanding compatibility in the code tracking process. Anti-multipath  
Figure 14 shows the multipath error envelope of different spread spectrum-modulated signals under the condition of multipath delay within 500 m. It can be clearly seen from the envelope line that the solution proposed in this paper (marked by the grey dashed line) is a multipath error and is significantly smaller than that of several other types of spread spectrum-modulated signals, which means that the proposed scheme has a better anti-multipath performance when there are short-distance multipath delays.