Performance measurements of a diverse collection of undersea acoustic communications signals

A diverse collection of underwater signaling waveforms provided by four acoustic modem developers was tested in the April ModemEx´99 experiment 6 km southwest of San Diego in 200-m water. These waveforms and a variety of probe signals were bidirectionally transmitted between a surface ship and an autonomous, bottom-deployed instrument called the telesonar testbed. The intent of this test was to relate communications performance in a variety of channels to signal design, decoding method, and the channel response. To reduce the number of free parameters, all waveforms were transmitted, received and digitized using a common suite of electronics. Although a complete waveform set could not be transmitted within the channel coherence time, they were all subjected to approximately the same channel geometries and noise. This paper describes the experimental design for ModemEx´99.