# Hybrid Dual-Link Data Transmission Based on Internet of Vessels
## 3 Algorithm Design  
### HDTA Algorithm (Hybrid Dual-Link Transmission Algorithm Based on Internet of Vessels)  
In the Internet of Vessels, ships are equipped with dual-head nodes, allowing them to communicate both with underwater nodes and with other ships on the surface. Due to the limited communication range, a multi-hop transmission method is employed for data transmission. As shown in Figure 2, when the underwater node NA has data to send to the underwater node ND, it selects the ship SA on the sea surface to forward the data. Then, ship SA forwards the data to ship SB, and ship SB forwards the data to ship SC. When ship SC cannot find any neighboring ships, it transmits the data to the underwater node NB. If NB cannot find any ships on the surface, it transmits the data to the underwater node NC. Node NC locates the ship SD on the surface and transmits the data. Ship SD forwards the data to ship SE, and finally, ship SD sends the data to the target node ND. This study uses a Bayesian reputation-based spatial crowdsourcing allocation algorithm to select the next relay ship node. Since ships have stronger computational resources compared to underwater nodes and are more flexible, ships are prioritized as relay nodes. The Bayesian spatial crowdsourcing allocation algorithm not only considers the reputation value but also factors in the location of the target node and the occurrence of black holes. This ensures that the algorithm improves transmission efficiency while maintaining stable transmission and minimizes the length of the transmission path. Ships are capable of satellite communication, allowing direct communication with cloud servers via satellites. However, due to the high cost of satellite communication, it is not suitable for large-scale data transmission over long distances and is only used for path planning. During data transmission, data are transmitted via multi-hop communication between ships and nodes using wireless and acoustic communication methods. As shown in Figure 3 (the blue dashed line represents broadcasting, the red line represents request selection, the green line represents response selection, and the black line represents data transmission), when an underwater node collects data to send to other underwater nodes or to the shore station, it first sets a timer T and broadcasts to the ships within its communication range. If multiple ships respond, the responding ships will forward their information along with the pre-transmission information to the cloud server. The server uses the HDTA algorithm to calculate and update the ship's reputation, selecting the ship with the highest overall score, which is the ship that the underwater node should select. The server then returns the selected ship's information in an encrypted form to the ship, which then forwards it back to the underwater node. After decryption, the underwater node sends the data to the selected ship, completing the first phase of data transmission. When the timer T expires and no ship has responded, the node will send the data to the nearest underwater node, which will redistribute the task. Figure 3: Information transmission from underwater node to ship. Figure 2: HDTA algorithm data transmission path. As shown in Figure 4, when a ship needs to transmit collected data to other ships, shore stations, or underwater nodes, it sets a timer T and broadcasts a data transmission request. If multiple units respond, the ship collects the positions of the responding ships and shore stations, then sends this information along with its own data back to the cloud server. After the cloud server processes the information using an algorithm, it returns the results to the ship. The ship that is sending the data uses the server's selection to determine the next relay node to complete the data transmission. If no ships or shore stations respond, the ship will wait for a period of time before sending another broadcast request.