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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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)

10. 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

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

12. 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)

13. Thank you