Coherent underwater communication

Type: Master's Assignment
Student: Jordy Huiting
Contacts: Koen Blom, Wouter van Kleunen, André Kokkeler
Project: SeaSTAR
Location: CAES, University of Twente

Introduction

Communication is getting increasingly important, high speed wireless digital communication can be found everywhere. Underwater the situation is different, underwater electromagnetic communication is due to attenuation practically unusable. The ocean environment is being researched more intensively and there is a need for communication. For example to transmit sensor data back to shore. Also offshore industries need communications to monitor pipelines and valves for example.

 

The wireless communication systems that do exist use acoustics or optical waves to transmit data. The optical systems are limited in range and can have a high throughput. The acoustic devices can offer communication over a larger range but generally offer low data rates. By using multiple relatively cheap nodes which operate in a wireless sensor network, higher bandwidth and power efficiency could be achieved. Nodes could communicate with each other and work together to transmit information to the surface.

The underwater acoustic channel is challenging due to limited bandwidth, severe multipath, frequency dependent fading, and Doppler shifts. Furthermore these characteristics are time varying.

Assignment

The topic for the master's thesis is the evaluation of different equalization and synchronization algorithms and especially their application to underwater communications.

Temporal versions of  the blind CMA and ECMA equalizers will be simulated and compared with a different solution. A traditional uses a decision feedback equalizer combine with synchronization. This approach can also be restructured to operate in a multichannel setup.

According to the literature there are no models to describe the underwater channel adequately. By using a channel model that includes doppler effects and intersymbol interference, at least the algorithms can be compared.

Underwater communication hardware is not readily available.  Special ordered hydrophones are going to be used for field tests.  During first experiments a sound card is used to sample data. In a later stage a BeMicro evaluation kit can be used to sample the underwater channel. These samples can be offline processed with different algorithms and an evaluation of the algorithms can be made.

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