Implementation of a real-time time-varying channel simulator for verification tests of underwater acoustic communication systems

Abstract

Generally, sea trials for performance tests of underwater acoustic communication modems and network algorithms are time- and cost-consuming process, because the performance should be verified for various underwater channels and operating conditions. The Doppler shift channel environment due to the relative modem movement, the time-varying channel with time-varying environment, and various types of channels according to depth and locations are some examples. For this reason, we developed a real-time channel simulator that can simulate time-varying channels including Doppler shift in various marine environments and test conditions. In the simulator the Doppler shift was implemented using the change of the impulse response function according to the movement of the modem. Similarly, the time-varying channel is simulated by random change of each impulse in magnitude and time delay according to a given probability distribution function over time. The simultaneous sampling frequency of the eight-channel input and output module is 1 MHz, which covers operating frequency of eight modems up to several hundred kHz. It also has the simulation capability of delay time more than 20 s which corresponds to 30 km distance. For the system verification performance test was conducted and verified the key performances.