The WaterCom lab testbed is for emulation experiments with real underwater wireless modems and try-run tests before conducting field experiments. The WaterCom experimental framework has been designed to be cloud hosted, extensible and reliable. Experimental nodes can come online at any time, poll the cloud based job scheduler queue, locally execute their experiment set, and periodically reconnect to the cloud service to upload results and execution status information. These operational modalities support permanently connected, occasionally connected, and predominantly disconnected modalities.
There are six OFDM acoustic modems in total in our testbed. Three of which are AquaSeNT AM-OFDM-13A models that can send out stronger signals whose communicate range is up to 5 km, and the rest are the educational version OFDM models that can communicate up 150m. Transducers and hydrophones of all modems are placed in a small tank as shown above. Next, we lined the bottom and four sides of our water tank with foam to attenuate the acoustic waves propagating along the tank, as well as the reflections. Finally, using the same foam material, we divided the tank into three compartments with a pair of strong and weak modems in each compartment. By applying these foam material, acoustic wave could be attenuated faster than usual, which will help us to customize the link topology. This allows us to create a topology where the educational modems must go through at least one stronger radio to reach any of the other radios.