Underwater wireless communication By: k.shiva shankar Electronics and communication engineering (06J11A04A4)

INTRODUCTION wireless communication technology today has become part of our daily life, the idea of wireless underwater communications may still seem far-fetched Although cabled submersible systems remain indispensable but if high-speed communication link is to exists wireless underwater communications with sensor technology and vehicular technology

Communication channel The signals that are used to carry digital information through an underwater channel are acoustic signals An underwater acoustic channel presents a communication system designer with many difficulties The signal is subject to multipath propagation, which is particularly pronounced on horizontal channels

Wave propagation The figures show multipath propagation in water In shallow water, multipath occurs due to signal reflection from the surface and bottom In deep water, it occurs due to ray bending tx rx tx distance c

Adaptive decision-feedback equalizer (DFE) inp. K com- biner forward + _ decision feedback Adaptation inp.1 inp.2 data out sync. filter coefficients training data data est. Adaptive decision-feedback equalizer (DFE) Equalizer task is to unravel the inter symbol interference

Underwater networks Integrated networks of instruments, sensors, robots and vehicles will operate together in a variety of underwater environments Depending on the application there two types of Acoustic network “Acoustic networks, navigation and sensing for multiple autonomous underwater robotic vehicles

Centralized network topology Centralized network, nodes communicate through a base station that covers one cell In a decentralized network, nodes communicate via peer-to-peer To accommodate multiple users within a selected network topology, the communication channel must be shared Methods for channel sharing are based on scheduling or on contention Centralized network topology Decentralized network topology

Current achievements The modem has successfully been deployed in a number of trials This modem is implemented in a fixed-point DSP with a floating-point co-processor Multi-user communications each at 1.4 kbps in 5 kHz band

Autonomous underwater vehicle (AUV) Autonomous underwater vehicle (AUV) is a robot that travels underwater Modem’s fit easily into the AUV Low power consumption Very reliable for high level throughput Autonomous underwater vehicle (AUV)

Application to oil-field monitoring short distance high bandwidth acoustic link platform base station power, communications, oil AUV sea level Application to oil-field monitoring

Applications Marine archaeology Search and rescue missions Defence Environmental monitoring to gathering of oceanographic data Marine archaeology Search and rescue missions Defence

Conclusion The aim of this is to build a acoustic communication as in figure This is not only the way for underwater communication By using optical waves which offers higher throughput (Mbps) over short distances (up to about 100 m)

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