# Combined Improved CEEMDAN and Wavelet Transform Sea Wave Interference Suppression
## 4 Experimental Results
Figure 5: (**a**) One\(-\)dimensional range result of the WSAW and sea wave interference; (**b**) range change result. vibration position of the water's surface was found, and the scattered power amplitudes in the range bins were searched to the left and right. The maximum value was taken as the actual water surface's reflected power. The change trend of the water surface obtained through the phase change is shown in Figure 5b. Figure 5b includes the sea wave signals and WSAW signals. In order to eliminate the sea wave signals, an improved CEEMDAN decomposition was carried out, which decomposed the superimposed signals into multiple IMFs and the residual error. During the signal processing, the signals were artificially added with the same decomposition Gaussian white noise, and wavelet denoising was performed on each IMF to reduce the influence of the errors on the subsequent signal reconstruction. The IMF corresponding to the initial reconstruction scale was determined using Equation (17), and then the IMF corresponding to the reconstruction scale \(k\) was determined using Equation (18). Thus, the reconstruction scale \(k\) corresponding to the IMFs included the WSAW signals. The remaining IMFs were discarded to realize the separation of the WSAW signal and sea wave interference signal. Under the condition of a weak wind in the 1 st gear of the variable, the correlation coefficients of the underwater speaker frequencies calculated using Equation (18) were 0.9747, 0.9843, 0.9776, 0.9826. The corresponding reconstruction scale signals were selected for reconstruction. Figure 6a shows the result obtained using the proposed method, and Figure 6b is the corresponding time-frequency analysis. The results of the proposed method are basically consistent with the transmitting frequencies of the underwater speaker. In this paper, the interference suppression method in translational acoustic-RF communication (TARF) was selected as a comparison. TARF proposes a filtering method to  
Figure 6: (**a**) The proposed algorithm’s result (weak wind); (**b**) time\(-\)frequency result; (**c**) filtering method’s result (weak wind); (**d**) time\(-\)frequency result. eliminate water surface interference caused by swimming in a pool. We designed a band-pass filter as a comparison of the proposed algorithm. The bandpass range was 80-420 Hz due to the communication frequencies of 100 Hz, 200 Hz, 300 Hz, and 400 Hz. Figure 6c shows the sea wave interference suppression result. Figure 6d shows the corresponding time-frequency analysis result. It can be clearly seen from the results that the effect of the filtering method on the interference suppression was not obvious. For the weak wind condition, Table 2 shows the BER for the two different methods. In Figure 7, the blue circle is an ideal constellation. The black asterisk represents the decoding result of the filtering, and the BER was 12.71%. The red plus sign represents the processing result of the proposed algorithm, and the BER was 0. The BER of the proposed algorithm was much lower than that of the filtering method. Figure 8 shows the results of the variable fan under in 4 th gear. The initial reconstructed signals were correlated with the transmission frequency reconstructed signals, and the correlation coefficients calculated using Equation (18) were 0.9825, 0.9730, 0.9672, 0.9688. The corresponding reconstruction scale signals were selected for reconstruction. \begin{table}
\begin{tabular}{c c} \hline
**Algorithm** & **Bit Error Rate** \\ \hline Proposed algorithm & 0 \\ Filtering method & 12.71\% \\ \hline \end{tabular}
\end{table} 
Table 2: BER of the proposed algorithm and filtering (weak wind). Figure 7: The results of the constellations of the ideal, proposed algorithm and filtering (weak wind). Figure 8a is the result obtained by the proposed method, and Figure 8b is the corresponding time-frequency analysis. Figure 8c shows the result obtained by filtering, and Figure 8d is the corresponding time-frequency analysis.