# Recent Progress on Underwater Wireless Communication Methods and Applications
## 3 Wireless Communication System Applied in Underwater Devices  
As underwater missions grow in complexity and sophistication, communication systems have become pivotal in enhancing the performance of various underwater devices. These devices increasingly rely on reliable and efficient communication technologies to accomplish their tasks effectively. This section offers a comprehensive review of wireless communication technologies applied to underwater systems, organized into two key parts. First, it provides an overview of current mainstream communication methods and discusses their applicability and challenges across different types of underwater devices. Acoustic communication remains a cornerstone due to its long-range capabilities despite limitations like low data rates and high latency. Optical communication offers high-speed data transfer in clear water but faces significant attenuation in turbid environments. RF communication, while effective for short-range applications, suffers from high attenuation in seawater. More recently, underwater electric field communication has emerged as a promising alternative, offering advantages such as low power consumption and reliability in short-range and complex environments. Second, the section delves into recent advances involving the integration of multiple communication technologies. By combining these methods, researchers aim to leverage the strengths of each while mitigating their individual weaknesses. Additionally, the application of machine learning (ML) techniques is explored, showing potential in optimizing communication protocols and improving reliability. Cross-medium communication strategies are also discussed, highlighting efforts to bridge underwater systems with surface and airborne platforms. These innovations collectively pave the way for more robust and versatile underwater communication systems that can adapt to diverse mission requirements and environmental conditions. This review aims to provide a holistic understanding of the current state and future directions  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Modality** & **System Type** & **Example** & **Data Rate** & **Range** & **Notes** \\ \hline Acoustic & Commercial & EvoLogics S2C R & 6–13.9 kbps & Up to 6000 m & \begin{tabular}{c} Reliable; widely \\ deployed; limited \\ bandwidth \\ \end{tabular} \\ \hline Acoustic & Research & OFDM-SPM [50] & \(\sim\)25 kbps & \(\sim\)3000 m & \begin{tabular}{c} Higher throughput \\ using subcarrier \\ power modulation \\ \end{tabular} \\ \hline Optical & Commercial & Hydromea Luma X & 10 Mbps & \(\sim\)30 m & \begin{tabular}{c} LED-based modem for \\ compact AUVs \\ \end{tabular} \\ \hline Optical & Research & LD-QPSK [17] & 8 Gbps & \(\sim\)0.6 m (scattering) & \begin{tabular}{c} Coherent system, \\ high-fidelity in \\ turbulence \\ \end{tabular} \\ \hline RF & Commercial & Seatooth S100 & \(\sim\)100 kbps & 5–10 m & \
\begin{tabular}{c} Asset tracking, \\ diver-AUV \\ communication \\ \end{tabular} \\ \hline RF & Research & Multi-band OFDM [80] & 1 Mbps & \(\sim\)15 m &
\begin{tabular}{c} Adaptive modulation, \\ energy-efficient design \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 7: Comparison between commercially available systems and research prototypes.  
of underwater communication technologies, emphasizing their critical role in advancing underwater exploration and operations.