## 3 Trends in Operational USVs
### Sensors and Situation Awareness Technologies  
Sensors are crucial components of USVs, and for the vehicles used in research papers, the list of sensors used is easily found [76; 77; 78], with model, main characteristics, and so on. However, for commercial USVs, there is limited publicly available information in this regard. Most sensors listed are related to the situation awareness capabilities of each USV model, which comprise radar, LiDAR (Light Detection and Ranging), thermal cameras, optical cameras (RGB), and AIS (Automatic Identification System) and are discussed in the next paragraph. But, certainly, most USVs are equipped with sensors such as GNSS (Global Navigation Satellite System), IMU (Inertial Measurement Unit), Radio Frequency (RF) communication, and voltage, current, and temperature sensors for battery management.  
The distribution of situation awareness technologies reveals that Automatic Identification System (AIS) and radar are the most commonly used sensing systems, reinforcing the maritime industry's reliance on these technologies for navigation and collision avoidance (Figure 9). AIS is widely adopted due to its ability to track nearby vessels and integrate with existing maritime traffic management systems. Radar, similarly, provides real-time environmental awareness, making it indispensable for autonomous operations, especially in adverse weather conditions. Camera-based systems also appear frequently, likely used for visual monitoring and object detection in combination with other sensors. Infrared (IR) and LiDAR, though less prevalent, play crucial roles in specific applications, such as night-time operations, obstacle detection, and high-precision mapping. The overall distribution of these technologies highlights a balance between traditional and advanced sensing solutions, with newer technologies like LiDAR gradually supplementing well-established methods. This trend suggests a continuous evolution in USV situational awareness capabilities, aiming for enhanced autonomy and safety in various operational environments.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**References** & **Comments** & **Type** & **Range** \\ \hline
[42; 43; 44] & BLOS (Beyond Line of Sight) & Terrestrial & Cellular (\(\sim\)50 km per tower) \\
[45; 46; 47] & GSM & Terrestrial & Cellular (\(\sim\)30 km per tower) \\
[48; 49; 50] & 3G & Terrestrial & Cellular (\(\sim\)10-30 km per tower) \\
[48; 49; 51] & 4G & Terrestrial & Cellular (\(\sim\)50 km per tower) \\
[48; 49; 52] & 5G & Terrestrial & Cellular (\(\sim\)1–10 km per tower) \\
[53; 54; 55] & Iridium & LEO (Low Earth Orbit) & Global \\
[56; 57; 58] & Starlink & LEO (Low Earth Orbit) & Global \\
[59; 60] & Inmarsat & MEO (Medium Earth Orbit)/GEO & Global \\
[51; 61] & MIMO radio & Terrestrial & Long (10–100 km) \\
[52; 62; 63] & Wi-Fi & Terrestrial & Short (\(\sim\)100 m-1 km) \\
[55; 60; 64] & VHF & Terrestrial & Medium (\(\sim\)50 km) \\
[63; 64; 65] & UHF & Terrestrial & Short–medium (\(\sim\)10–50 km) \\  & COFDM (Coded Orthogonal & & \\
[52; 66; 67] & Frequency Division & Terrestrial & Medium (\(\sim\)10–50 km) \\  & Multiplexing) & & \\
[60; 68] & DSC (Digital Selective Calling) & Terrestrial & Medium (\(\sim\)50 km) \\
[69; 70] & Kongsberg Maritime Broadband & Terrestrial & Medium (\(\sim\)50 km) \\  & Radio (MBR) & Terrestrial & Medium (\(\sim\)10–50 km) \\
[71] & Line-of-sight radio & Terrestrial & Short–medium (\(\sim\)10–50 km) \\
[65; 67; 72] & Mesh radio & Terrestrial & Medium (\(\sim\)10–50 km) \\
[37; 73] & Short-range radio & Terrestrial & Short (\(\sim\)1 km) \\
[73; 74] & Encrypted wireless network & Terrestrial & Short–medium (\(\sim\)1–50 km) \\
[44; 75] & RC transmitter & Terrestrial & Short (\(\sim\)1 km) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Solutions given by USVs’ Manufacturers.