# Hybrid Dual-Link Data Transmission Based on Internet of Vessels
## 1 Introduction  
Data transmission plays a crucial role in marine networks. Efficient and real-time data transmission enables the precise monitoring and management of the marine environment, resources, and facilities, supporting marine disaster warning, ecological protection, and sustainable resource development [1]. Data collection devices, such as sensors, buoys, and unmanned submersibles, continuously gather key data on marine temperature, salinity, water quality, meteorological conditions, and more. The transmission system ensures that this information is delivered in a timely and accurate manner to shore-based or cloud platforms for analysis and processing [2]. Stable data transmission technologies effectively support intelligent applications such as autonomous navigation and underwater robotics [3], enhancing the efficiency of marine management and emergency response. Data transmission in the marine environment faces numerous technical challenges. Underwater communication is heavily affected by seawater absorption and scattering, resulting in significant signal attenuation, especially in deep-water areas where the communication range and data transfer rates are limited. Bandwidth constraints make large-scale data transmission and real-time monitoring difficult, while noise interference in the marineenvironment further degrades signal quality [4]. The energy consumption of devices is another major issue, particularly for unmanned underwater devices, where the limited energy restricts the operational time. Additionally, transmission delays impact real-time applications such as disaster warning and environmental monitoring. Although technologies like acoustic communication have been applied, the complexity of the marine environment makes overcoming issues such as signal attenuation and bandwidth limitations a pressing challenge. Many scholars are actively researching this issue, but an ideal solution has yet to be found. In recent years, the development of marine Internet of Things (IoT) technology has been rapid, especially in utilizing surface vessels to form a vessel network for data transmission (as shown in Figure 1a), making it possible to leverage surface vessel resources to improve underwater communication performance. Compared to underwater networks, vessel networks offer several advantages, including faster transmission speeds, longer transmission distances, lower bit error rates, more stable links, lower energy consumption, easier deployment and maintenance, and a wider variety of devices. Against this backdrop, this paper proposes a Hybrid Dual-Link Transmission Algorithm (HDTA) based on the Internet of Vessels, aimed at improving underwater communication performance by utilizing vessel resources. Figure 1b shows the sensor nodes used in this study. These nodes were independently developed by the Sensor Network Laboratory in collaboration with our team and deployed on the OceanSense marine sensor network test platform in Qingdao Bay. These sensor nodes have bidirectional communication capabilities between above-water and underwater environments, allowing for effective data transmission across both, which we refer to as \"dual-head nodes\". The OceanSense platform provides a real-world experimental environment for this study, used to validate the communication and data transmission capabilities of marine sensor nodes in complex oceanic conditions. In this study, we deploy bidirectional sensor nodes on vessels to verify their feasibility and performance in underwater and surface communications. These vessels can not only communicate with underwater sensor nodes but also exchange information with other vessels, thus establishing a dual-link communication model between the surface and underwater. Specifically, the dual-link data transmission based on the vessel network faces two main challenges: first, how to select suitable vessels as relay nodes, and second, how to determine the data transmission path.