## 4 Simulation and Experimental Results
### Experiment
#### 4.2.2 Experimental Results and Discussion  
The signal files stored in the Rx computer were post-processed using the software receiver for statistics code-tracking accuracy. For all compared signals, the mean value of the tracking accuracy for each \(C/N_{0}\) was calculated for five groups of signal files, each with 2000 ms (DLL steady state output). Figure 14(a),b show the experimental code-tracking accuracy for the DLL with coherent integration times of 1 ms and 10 ms, respectively. The lowest \(C/N_{0}\) in Figure 14(a),b is 35 dB-Hz and 25 dB-Hz, respectively. Because the coherent integration time determines the tracking threshold of the loop. From Figure 14(b), we can see that the proposed signal is still able to track the signal stably even at a shallow \(C/N_{0}\) level. This indicates that the proposed signal is robust in high-noise scenarios. Figure 14 illustrates that the code-tracking accuracy of pulsed and continuous signals with the same modulation is approximately the same. The \(C/N_{0}\) of Pulse-OTFS(10,1023) and OTFS(10,1023) is about 8 dB lower compared to Pulse-BPSK(5) and BPSK(5) with the same code-tracking accuracy; in other words, the proposed signal has a higher delay measurement accuracy with the same \(C/N_{0}\). Because Pulse-OTFS(10,1023) has a steeper main peak of the autocorrelation function with the same bandwidth, as shown in Figure 4, this benefits delay resolution and measurement accuracy. At medium and high \(C/N_{0}\), the experimental results agree well with the theoretical results in Figure 8(b), although the experimental results have a minor deviation from the latter. Figure 15 gives a plot of the magnitude of the correlator peaks corresponding to the correct code phase in the signal acquisition process. It reflects the variation in the correlation loss at different Doppler frequency offsets. The \(C/N_{0}\) is 55 dB-Hz for all received signals, and the Doppler frequency search interval is 500 Hz. From the figure, we can see that the correlation loss of the pulsed signals is much lower than that of the continuous signals. Table 5 lists the magnitude values of correlator peaks corresponding to different Doppler frequency offsets in Figure 15. Specifically, the correlation peak magnitudes for all signals are approximately the same at 0 Hz, and the acquisition results have no loss. The correlation peak magnitudes of Pulse-OTFS(10,1023) and Pulse-BPSK(5) at \(\pm\)0.5 kHz decrease little, but they suffer severe loss for OTFS(10,1023) and BPSK(5). It is not until the Doppler frequency offset of \(\pm\)5 kHz that the correlation peak magnitudes of Pulse-OTFS(10,1023) and Pulse-BPSK(5) reach the level of OTFS(10,1023) and BPSK(5) at \(\pm\)0.5 kHz. The tolerable frequency offset of the pulsed signal is 10 times that of a continuous signal, and the proposed signal can therefore be searched with a Doppler search interval 10 times that of BPSK(5). This enables the proposed signal to search for the Doppler frequency using large steps, thus speeding up the signal acquisition process. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline RF frequency & 2 GHz \\ Sampling rate & 20 MHz \\ Signal bandwidth (\(B\)) & 10.23 MHz \\ Signal period (\(NT\)) & 1 ms \\ Duty cycle (\(1/N\)) & 0.1 \\ Coherent integration time (\(T_{coh}\)) & 1 ms or 10 ms \\ Early-late spacing of the correlator & 1 chip \\ Bandwidth of the DLL & 1 Hz \\ Bandwidth of the PLL & 10 Hz \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Experiment parameters. To verify the acquisition efficiency of the proposed signal in the hardware system, we counted the average running time of 100 times the acquisition program with the PCS scheme in different Doppler frequencies, as shown in Table 6. We can see that the running time of the program is close to the same at 0 Hz and 40 kHz Doppler frequency offset. This is because we use a commonly employed detection and decision method, which searches for all correlation results in Doppler frequency points and finds the maximum value before the acquisition.