# Generalized Frequency Division Multiplexing-Based Low-Power Underwater Acoustic Image Transceiver
## 3 Simulation Results  
A MATLAB-based UWA channel model was developed by [PERSON] et al. [31], and the MATLAB-based UWA channel model was integrated into the simulation. The UWA channel model, having a carrier central frequency of 40 kHz, a underwater channel bandwidth of 20 kHz, and a transmission distance of 100 m, was used for simulations. The transmission distance was 100 m, the water was 14.5 m deep, and the transmitter and receiver were set 3 m and 2 m beneath the sea surface, respectively. The simulation parameters of the proposed GFDM-based low-power UWA image transceiver are listed in Table 1.  
Figure 2 shows the BER performance of the GFDM-based UWA image transceiver. When using the 4-QAM strategy, the BER values of the proposed transceivers with CEEs of 0%, and 5% with 12.22 dB SNR are \(2.73\times 10^{-5}\), and \(4.55\times 10^{-5}\), respectively, while the SNR values with CEEs of 10%, and 20% for BER of \(2.73\times 10^{-5}\), are 13.01 dB, and 13.98 dB, respectively. In addition, the SNR increases as the CEE changes from 0% to 10%, and 10% to 20% are 0.79 dB and 0.97 dB, respectively. The proposed GFDM-based UWA image transceiver with the PCE can have the same transmission BER performance with a lower SNR than the transceiver with a CEE of 20%. When using the 16-QAM strategy, BER values with CEE of 0%, and SNR of 18.33 dB, is \(10^{-4}\), while the SNR values with CEEs of 5%, and 10%, for a BER of \(7.27\times 10^{-5}\), are 19.21 dB, and 20.97 dB, respectively. The SNR performance with 20% CEEs for BER of \(2.73\times 10^{-5}\) is 26.02 dB. The SNR of the proposed transceiver increases as the CEE changes from 0% to 5%, and 5% to 10% are approximately 0.88 dB and 1.76 dB, respectively. The results show that the 4-QAM has better transmission BER performances than the 16-QAM in the underwater environment, while the 16-QAM has a higher transmission throughput than 4-QAM. \begin{table}
\begin{tabular}{l l} \hline \hline
**Technology** & **Technology Characteristics** \\ \hline GFDM modulation & [PERSON] et al. [15] \\ Channel model & [PERSON] et al. [31] \\ Number of subcarriers (B) & 128 \\ Number of subsymbols (C) & 9 \\ Filter method & Root-raised cosine \\ Roll-off factor & 0.1 \\ Channel bandwidth & 20 kHz \\ Adaptive modulation & 4-QAM and 16-QAM \\  & (2000, 1000) LDPC code encoder with a code \\ Channel coding & rate of 1/2, a column weight of 3, a row \\  & weight of 6 \\ UW transmission media & Image signal \\ Power weighting factors & \(1/10\), \(2/10\), \(\ldots\),10/10 \\ BER limits for image transmission & \(10^{-4}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters of the proposed GFDM-based low-power UWA image transceiver. The image MSE (IMSE) of a \(g\times h\) image is defined as follows:  
\[IMSE=\frac{1}{g{t}}\sum_{i=0}^{g-1}\sum_{j=0}^{h-1}{[P(i,j)-Q(i,j)]}^{2} \tag{20}\]  
where \(P(i,j)\) and \(Q(i,j)\) are matrices with the pixel values of the original and received UW image signals, respectively. The peak signal-to-noise ratio (PSNR) (dB) is expressed as  
\[PSNR=10\log_{10}(\frac{Max(I(i,j))^{2}}{IMSE}) \tag{21}\]  
Figure 3a,b shows the received underwater image 1 signals using 4-QAM, with the transmission BERs of \(10^{-3}\) and \(10^{-4}\), respectively, in the GFDM-based underwater image transceiver with a CEE of 10%. The PSNRs are 50.31 dB and 62.39 dB, respectively. Figure 4a,b shows the received underwater image 2 signals using 4-QAM, with the transmission BERs of \(10^{-3}\) and \(10^{-4}\), respectively, in the GFDM-based underwater image transceiver with a CEE of 10%. The PSNR is 34.74 dB and 44.46 dB, respectively. Figure 5a,b shows the received underwater image 3 signals using 4-QAM, with the transmission BERs of \(10^{-3}\) and \(10^{-4}\), respectively, in the GFDM-based underwater image transceiver with a CEE of 10%. The PSNR is 34.73 dB and 45.64 dB, respectively.