## 5 Conclusions  
In this paper, we proposed the SOCA for the VDES network in the MIoT to mitigate the impact of interference caused by transmissions of AIS messages on transmissions of VDE-TER data in coastal areas with a high concentration of ship stations. SOCA operates with four steps: (1) construction of the NIT and VDES frame maps, (2) construction of the candidate slot list, (3) TDMA channel selection, and (4) slot selection for collision avoidance. To demonstrate the superiority of SOCA, we conducted experimental simulations under static and dynamic ship scenarios. In the static ship scenario, SOCA outperforms the existing VDES, achieving improvements of 13.58% in aggregate throughput, 11.50% in average latency, 33.60% in collision ratio, and 22.64% in packet delivery ratio. Similarly, in the dynamic ship scenario, SOCA demonstrated improvements of 7.30%, 11.99%, 39.27%, and  
Figure 8: Packet delivery ratio: (**a**) static ship scenario and (**b**) dynamic ship scenario.  
11.82% in the same metrics, respectively. The results show that SOCA has the potential to overcome the limitations of slot allocation in the existing VDES, such as frequent collisions caused by AIS messages and transmission delays of VDE-TER data, in high-density and dynamic maritime communication networks.  
SOCA is a MAC layer enhancement of standard VDES, ensuring compatibility with the VDES system and simplifying potential implementation issues. From this perspective, it is expected to be a promising solution for future large-scale MIoT applications, such as autonomous ships, real-time maritime traffic management, and remote ship monitoring, all of which demand substantial data exchange. Meanwhile, the simulation environment in this study does not fully reflect the complexity of the real-world maritime conditions. Therefore, we consider it future work to study an enhancement of SOCA that incorporates more realistic conditions for maritime ad hoc networks, enabling ship stations to exchange MIoT application data via VDE-TER, even in long-range offshore environments.  
Conceptualization: S.-B.L., J.-H.K. and E.-J.K.; methodology: S.-B.L., J.-H.K. and E.-J.K.; software: S.-B.L., J.-H.K. and E.-J.K.; validation: S.-B.L., B.-Y.K., W.-S.S., T.S. and E.-J.K.; formal analysis: S.-B.L., B.-Y.K., W.-S.S., T.S. and E.-J.K.; investigation: J.-H.K. and E.-J.K.; resources: B.-Y.K., W.-S.S., T.S. and E.-J.K.; data curation: J.-H.K., B.-Y.K., W.-S.S. and T.S.; writing--original draft preparation: [PERSON]-B.L., [PERSON]-H.K. and [PERSON]-J.K.; writing--review and editing: [PERSON]-[PERSON], [PERSON]-[PERSON] and [PERSON]-J.K.; visualization: [PERSON]-B.L.; supervision: [PERSON]-[PERSON]; project administration: [PERSON]-[PERSON]; funding acquisition: W.-S.S. and E.-J.K. All authors have read and agreed to the published version of the manuscript.  
This research is supported by a grant from Republic of Korea National R&D Project \"Development of Internet like maritime network technology and diversification of LTE-Maritime user equipment\" funded by Ministry of Oceans and Fisheries (KS211523).  
Not applicable.  
Data Availability Statement: Data is contained within the article.  
The authors declare no conflicts of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} AI & Artificial intelligence \\ AIS & Automatic identification system \\ ASC & Announcement signalling channel \\ ASM & Application specific message \\ BBSC & Bulletin board signalling channel \\ DC & Data channel \\ DSCH & Data signalling channel \\ ID & Identifier \\ ITU & International Telecommunication Union \\ MAC & Medium access control \\ MASS & Maritime autonomous surface ship \\ MIoT & Maritime Internet of Things \\ NI & Nominal increment \\ NIT & Neighbor information table \\ NM & Nautical mile \\ NS & Nominal slot \\ NTS & Nominal transmission slot \\ RAC & Random access channel \\ RC & Ranging channel \\ RI & Reporting interval \\ Rr & Report rate \\ SI & Selection interval \\ SOCA & Slot occupancy-based collision avoidance \\ \end{tabular}