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| Titel |
Optical Communication System for an Underwater Wireless Sensor Network |
| VerfasserIn |
C. Gabriel, A. Khalighi, S. Bourennane, P. Léon, V. Rigaud |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060683
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| Zusammenfassung |
| Seventy percent of the Earth is covered with water. Yet, we know so little about what lies
below the sea surface. One new emerging technology that can help in oceans exploration is
underwater wireless sensor network (UWSN). In such a network, a number of sensors are
connected to a set of nodes that collect the data from them. Then, each node communicate its
retrieved data to the other parts of the network through wireless links. So, an important step in
the implementation of an UWSN is the design of an adequate transmitter/receiver system
that is reliable, easy to implement, energy efficient and adapted to the underwater
environment.
Thanks to its cost-effectiveness and low-energy consumption property, optical underwater
communication turns to be the most adequate solution for medium range node connections in
an UWSN. To evaluate the optical underwater channel, we have studied its impulse response
using a Monte Carlo simulator that takes into consideration all the transmitter, receiver and
medium characteristics. We have demonstrated through these simulations that the channel
delay dispersion is negligible in most practical cases. Therefore, we do not need to perform
computationally complex signal processing such as channel equalization at the
receiver.
After studying the channel characteristics, we have turned our attention onto the
transmitter/receiver system design. For this, we have simulated a system composed by a
high-power monochromatic 532 nm LED transmitter and a Silicon PIN photodiode receiver
with a collimating lens for capturing the scattered light. After photo-detection, the
photo-current is converted to a voltage and low-pass filtered to limit the thermal
noise variance which is the dominant noise in the receiver. Note that, in our case,
background noise can be neglected because we are working in deep waters were the
sunlight cannot penetrate. Then, using on-off-keying (OOK) modulation, we have
proceeded to signal detection based on optimum thresholding. We have evaluated
this system by studying its bit-error-rate (BER) performances in different water
types as a function of the transmitted power, the transmission range and the receiver
lens aperture size. As a typical case, considering an acceptable BER of 10-6, we
have shown that in clear ocean waters, for a transmit power of 0.1 W and a 20 cm
lens aperture at the receiver, we can reach up to 20 m while transmitting at 1 Gbps
bit-rate.
Now, we are working on the development of new signal processing techniques related to
the transmitter and the receiver in order to improve the system performance and enable
transmission over longer distances and with higher bit-rates. |
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