Underwater Communication

          UNDERWATER COMMUNICATION

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INTRODUCTION

Underwater communication is one of the most difficult communication as compared to  Land and space communication. Advancement in technology makes wireless communication in our daily lives, but still under sea and ocean the wireless communication idea is still achievable.

 PROBLEMS:

1. Multipath Propagation.

      2. Time variations of the channel.

      3. Use of Acoustic Waves.

     

      4.  Attenuation. 

Some of Technology :

Wired communication is one of fastest communication, But submarines and ships and other underwater vehicles travel long distances, so we can’t provide wires for long distances.

Mobile Phones are not used because of the EMW waves Principle,this creates a huge attenuation in underwater .

1. Li Fi  Technology: Li Fi (Light Fidelity) is an impressive and emerging technology which uses the visible light spectrum for communication introduced by Professor Harald Haas.In Li-Fi data is fed into LED light bulbs, it then sends data(embedded in its beam) at rapid speed to photodetector. The tiny changes in rapid dimming of LED bulbs is then converted by the receiver into an electric signal. The signal is converted back into binary data. This modulation is executed in such a way that it is not visible to the human eye. Li-Fi is unique where visible light energy used for illumination may also be used for communication.

2. One of the Recently researched ways for communication is QKD (Quantum Key Distribution). This one of secure communication,  where Third parties won't be able to communicate between send and receiver. It implements the security protocols that perform security related functions and applied cryptographic methods that follow quantum physics that are used in underwater communication.The advantage of QKD is that the   communication between sender and receiver will be able to detect the third party involvement

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3. ACOUSTIC MODEM: Converts Digital data into special underwater sound signals.

These signals are then received by a second acoustic modem and converted back into Digital data.

        

4. HYDROPHONE: Hydrophone are designed to be used underwater for recording or listening to underwater sounds. These are based on Piezoelectric transducers that create electricity when introduced to pressure variation. Unique thing of Transducers is that they convert sound signals into electrical signals.This was introduced during world war1.

5. SONAR:It's used to communicate in order to detect the thing. A sound pulse is generated and sent through the transmitter in sonar devices. The Receiver receives the sound waves that are reflected by submerged objects. The reflected signal is picked up and analysed by a receiver, which can calculate the target's range, bearing, and relative motion. Receiving sensors that pick up the noise emitted by the target makeup passive systems (such as a ship, submarine, or torpedo). Waveforms detected in this manner can be evaluated for features, as well as direction and distance. Acoustic communication systems are the third type of sonar device, and they require a projector and receiver at both ends of the acoustic path.

 These are Some of the Techniques for underwater communication.  Still Research is going on underwater communication for finding more convincing ways to communicate.