# Robust Anti-Jamming Algorithm Based on Transmit/Receive Time-Sharing Technology
## 4 Robust Anti-Jamming Algorithm Based on the Transmit/Receive Time-Sharing
### Performance Analysis  
In order to evaluate the proposed algorithm's performance under different factors, various experiments were carried out for different narrowband interference scenarios. It is assumed that the prior and burst signals are navigation signals from any random B3 satellite, the data length is 15 ms, the sampling rate is 25 MHz, the modulation mode is P code BPSK modulation, and the pseudo-code rate is 10.23 MHz. When analyzing the performance of the anti-jamming receiver, the CNR and convergence time after anti-jamming were considered, and the prospect of the robust anti-jamming algorithm was analyzed for possible application in BDS. Because of the considerable convergence time difference between the robust anti-jamming algorithm and the traditional anti-jamming algorithm, the data is expressed in dB form. The robust anti-jamming algorithm can improve the problem of increased CNR loss and increased signal loss caused by increased interference intensity. Figure 11 shows the simulation results of robust anti-jamming algorithms under different JSR. The original CNR is set to 55 dB-Hz, and the interference bandwidth is set to 2 MHz. As shown in the figure, the CNR loss in the traditional anti-time-domain interference receiver will gradually increase as the interference power increases. However, the robust anti-jamming filter can use the prior information to converge exceptionally quickly to ensure that the CNR loss is always less than 1 dB-Hz. In addition, the convergence time of the traditional anti-interference algorithm will gradually increase. In contrast, the convergence time of the robust algorithm is around \(-20\) dB less than the traditional one. The robust anti-jamming algorithm can improve the problem of longer convergence time caused by increased jamming bandwidth. The simulation results of the robust anti-jamming algorithm under different bandwidth interference are shown in Figure 12. The original CNR is set to 55 dB-Hz, and the JSR is set to 45 dB. Results show that the interference bandwidth within the range does not affect the CNR performance between the anti-jamming algorithms, traditional and proposed. However, the information loss shows the advantages of the robust method in the convergence time. The convergence time of the traditional algorithm increases with the increase of interference bandwidth, while the convergence time of the robust anti-jamming algorithm remains at 20 ns. Figure 10: The estimated CNR of the robust anti-jamming algorithm. Under the influence of navigation signal strength, the robust anti-jamming algorithm can improve CNR loss and convergence time increase in strong signal scenarios. Figure 13 shows the simulation results of the robust anti-jamming algorithms under different original CNR scenarios. Assuming that the JSR is 50 dB, and the interference bandwidth is 2 MHz, the anti-interference effect is optimized by adjusting the iteration step. The figure shows that the traditional algorithm in strong signal scenarios will produce a significant CNR loss with a longer convergence time. In contrast, the robust anti-jamming algorithm can achieve a slight CNR loss in a short convergence time. The CNR loss of the proposed algorithm is significantly smaller than the traditional one. Moreover, the advantage of the robust algorithm becomes more evident as the signal power increases. The application of T/R time-sharing technology in the future BDS has broad prospects. Figure 14 intuitively analyzes the convergence results of the robust anti-jamming algorithm with different signal reception intervals. Considering that 1.5 s navigation data can be sufficiently resolved in navigation receivers, other constellations and link communication may adopt a shorter period to realize the T/R time-sharing technology. Figure 14 analyzes the filter performance when the signal reception intervals are 15 ms and 75 ms, respectively.