Underwater acoustic 1
- 1. Made by- Digisha Singhal 13bec026 Kinjal Aggrawal 13bec054 Guided by- Dr. Mehul Naik
- 2. 1. Deficiency in current communication 2. Necessity of underwater acoustic communication 3. Acoustic communication 4. Basic acoustic communication model 5. Acoustic modem 6. Applications 7. Limitations 8. Conclusion 9. References
- 4. Radio waves propagate under water at extremely low frequencies (30Hz-300Hz) & require large antennae and high transmission power. Optical waves do not suffer much attenuation but are affected by scattering. Wired underwater is not feasible in all situations as shown below-: o Breaking of wires o Significant cost of deployment Acoustic waves are the single best solution for communicating Under water.
- 5. Underwater Acoustics is the study of propagation of sound in water & interaction of mechanical waves that constitute with water & its boundaries. Underwater wireless communication is the wireless communication in which acoustic signals (waves) carry digital information through an underwater channel. Typical frequencies associated with Underwater Acoustics are 10Hz to 1MHz. The propagation of sound in the ocean at frequencies lower than 10 Hz is not possible. Frequencies above 1 MHz are rarely used because they are absorbed very quickly.
- 7. When no data is being transmitted, the modem stays in sleep mode, it periodically wakes up to receive possible data being transmitted by far end modem. This results in low power consumption. Similarly when the data is to be transmitted , the modem receives data from its link in sleep mode and then switches to transmit mode and transmit the data. This technology can also be used to control small, unmanned submarines, called Autonomous Undersea Vehicles (AUV's).
- 8. Oceanographers use acoustics to control underwater instruments and acquire the data that they collect remotely. Underwater acoustic modems are relatively slow compared to telephone or cable modems on land. Equipment Autonomous Undersea Vehicles (AUVs) Underwater sensors (UW-ASN)
- 9. A robot crawler carries a modem, a camera, and a digital signal-processing unit. Traversing the seafloor, searches for an object. When an object is found, sends an acoustic signal to a ship or shore based station. It can then be commanded to take a still frame photo, compress it and transfer the image to an acoustic signal that is sent back to the investigator.
- 10. Autonomous vehicles working under the ice can be controlled and their data can be transmitted to a topside station using underwater acoustic links.
- 11. Underwater data links can be combined with satellite data links to provide data in real-time from instruments on the seafloor to scientists ashore. Pressure sensors that are deployed on the seafloor can detect tsunamis. Solar powered AUVs. Pollution monitoring.
- 12. Battery power is limited and usually batteries cannot be recharged easily. The available bandwidth is severely limited. Underwater sensors are prone to failures because of fouling, corrosion, etc. Highly affected by environmental and natural factors such as heterogeneities of the water column, variations of sound velocity versus depth, temperature and salinity, multiple and random sea reflections and significant scattering by fish and bubble clouds.
- 13. The main objective is to overcome the present limitations and implement advanced technology for oceanographic research and cope up with the environmental effects on the noise performance of acoustic systems to compete with the future challenges like effective transmission of audio and video signals etc.
- 14. 1. www.ieee.org/organizations/pubs/newsletters/oes/html/spring06 /underwater.html 2. www.link-quest.com/html/oceans2000.pdf/ 3. www.gleonrcn.org/pgmdownload_media.php?name=Aquanode.p ps 4. www.cs.virginia.edu/sigbed/archives/akyildiz.pdf