Underwater sound communication
Abstract
Underwater acoustic signal transmission was investigated. The successful application of spread spectrum techniques in acoustic underwater transmission channels is controlled by the stochastic nature of the channel. The coherent gain losses due to the limited coherence time and coherence bandwidth of the channel were calculated for FM-chirp and PN-code modulated signals. Further gain losses occur due to the mismatch between the actual and the assumed relative speed between transmitter and receiver. The chirp signal is less sensitive to Doppler mismatch and thus requires fewer Doppler channels. The possibility of reducing the redundancy of speech signals and thus of reducing the stringent coherence constraints on the channel is discussed.
- Publication:
-
Unknown
- Pub Date:
- June 1985
- Bibcode:
- 1985usc..rept.....S
- Keywords:
-
- Signal Transmission;
- Sound Transmission;
- Underwater Acoustics;
- Underwater Communication;
- Chirp Signals;
- Coherent Acoustic Radiation;
- Doppler Effect;
- Frequency Modulation;
- Acoustics