Abstract:

Underwater acoustic communication requires waveforms that are robust to the signal distortions caused by the acoustic channel. Many waveforms used for this purpose require the transmission of training symbols that span the intersymbol interference to “learn” and compensate for these channel effects. These waveforms also require exacting coordination between the transmitters to avoid multiple access interference. Differential frequency hopping (DFH) is a fast frequency hopping, digital signaling technology that requires minimal information at the transmitter to communicate in the underwater channel. DFH has the desirable performance features of noninterfering spread spectrum operation, spectral reuse, and fading and interference resistance. This presentation describes the baseline autosynchronizing, single‐user DFH decoder for a multiple hydrophone receiver and investigates two processing techniques incorporated for shallow‐water multiuser applications: fading mitigation and multiuser interference mitigation, as implemented in conjunction with array processing. We present the performance of the baseline DFH decoder in terms of bit error rate with and without these enhancements on single‐ and multiuser data collected at sea during the 2008 Surface Processes and Acoustic Communications Experiment (SPACE08).