Low Signal-to-Noise Ratio Underwater Acoustic Communications

摘要

Cmmunications with low input signal-to-noise ratios(SNRs)are often called covert communications,as the probability of detection and interception decreases with decreasing SNR.Direct-sequence spread-spectrum(DSSS)signaling works at low SNRs because of the processing gain derived from the signal time bandwidth product.The underwater acoustic channel faces high multipath spread and rapidly changing channel conditions.