Abstract: VHF Data Link (VDL) Mode 2 is a critical infrastructure of the civil aviation air traffic management (ATM) sys-tem. The future ATM system will adopt the trajectory -based operations (TBO) paradigm, which imposes morestringent requirements on VDL Mode 2. To enhance the performance of VDL Mode 2, this paper develops a simu-lation model of its medium access control (MAC) protocol using the optimized network engineering tools (OPNET).The protocol employs the p-persistent carrier sense multiple access (p-CSMA) mechanism. Through extensivesimulations, the influence of the persistence parameter p on system throughput, transmission delay, and frameloss rate is systematically analyzed. The results show that p has a significant impact on these three performancemetrics, and a clear trade -off exists among them. By appropriately selecting the value of p, it is possible toachieve high throughput while maintaining low transmission delay and frame loss rate, thereby satisfying the reli-ability and real-time communication requirements of TBO operations.

Key words: aeronautical data link, VDL Mode 2, medium access control, optimized network engineering tools (OPNET) modeling