Implications of Time Variability on a Ricean Noncoherent Model in Acoustic Underwater Communication

This paper investigates the implications of time variability in the underwater acoustic channel on coded multiple tone frequency-shift keying (FSK) that uses a Rice model on narrow toneband envelopes. It is evaluated with Convolution coded frequency parallel binary FSK in the 5 Watermark replay channels, in terms of the bit error rate over the noise measure E
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, where the model parameters are tracked using known pilots. The performance varies with pilot sparseness; however, it is significantly improved by limiting the likelihood input signalto-noise ratio, which enables using a simple data model with minimal estimation overhead, and pilots can be separated by up to 10 [s].