Abstract: Underwater acoustic(UWA) network protocol simulation on OPNET software could not follow the changing of channel structure and did not support custom modulation. In view of the limitations mentioned, a more realistic method of UWA protocol simulation on OPNET was introduced. UWA network ALHOA protocol simulation was token as an example. The physical layer modulation customized was called π/4-DM-DQPSK which was based on Chirp Spread Spectrum. In Matlab, the system would generate a modulation curve which would then be imported into OPNET to adjust the configuration of other pipelines. The simulation results of ALHOA protocol was verified in two Bellhop channels with different structures, which showed changing structure had a sensitive impact on ALHOA protocol. The method introduced has reference value on simulating UWA network protocol flexibly in OPNET.

Key words: Underwater Acoustic Communications, Chirp Spread Spectrum, Underwater Acoustic Network, OPNET Simulation