Superimposed training low probability of detection underwater communications

Low probability of detection underwater acoustic communications using direct-sequence spread spectrum.

Direct-sequence spread spectrum is used for underwater acoustic communications between nodes, at least one of which is moving. At-sea data show that the phase change due to source motion is significant: The differential phase between two adjacent symbols is often larger than the phase difference between symbols. This poses a challenge to phase-detection based receiver algorithms when the source...

Adaptive Underwater Acoustic Communications

Underwater wireless networks consist of mobile and static nodes, which usually communicate using the acoustic channel since radio transmissions attenuate rapidly and optical communication is only suitable for short distances. The underwater acoustic channel is plagued with issues of high transmission power requirements, rapidly changing channel characteristics, multi-path echoes, possible high ...

Covert underwater acoustic communications.

Low probability of detection (LPD) communications are conducted at a low received signal-to-noise ratio (SNR) to deter eavesdroppers to sense the presence of the transmitted signal. Successful detection at intended receiver heavily relies on the processing gain achieved by employing the direct-sequence spread-spectrum (DSSS) technique. For scenarios that lack a sufficiently low SNR to maintain ...

Blind equalization for underwater communications

AUV Application for Inspection of Underwater Communications

Regular inspection of underwater communications (pipelines and cables) is actual problem of modern oil and gas industry. Specially equipped vessels, towed underwater devices and remote operated vehicles /ROV/ are applied for these purposes as usually, but quality of acquired data does not always allow revealing emergencies at the proper time. “Spot” inspections by ROVs give difficultly comparab...