21-07-2012, 12:15 PM
Designing an Adaptive Acoustic Modem for Underwater Sensor Networks
[attachment=28306]
INTRODUCTION
UNDERWATER sensor networks have a wide range
of oceanographic applications including marine exploration,
environmental monitoring and coastal surveillance. The
preferred mode of wireless communication in these networks
is based on acoustic signals. This is due to the fact that
radio frequencies suffer high attenuation underwater. Optical
communication is possible but only in clear water at relatively
short distances. Unfortunately, acoustic communication
is challenging due to large and variable multipath delay spread,
Doppler shifts and long propagation delays [1].
ADAPTIVE ACOUSTIC MODEM DESIGN
Underwater acoustic modems consist of three fundamental
components as shown in Fig. 1: a transducer, an analog
transceiver and a digital hardware platform for signal processing
and control. This article focuses on the design of the
physical layer on the digital platform.
SIMULATION AND SEA TEST RESULTS
To evaluate the proposed adaptive modem, we did both
simulations and sea tests. We executed a set of simulations
to find the best data rates for different links in a network and
to understand the potential benefits of modifying the data rates
on a per link basis. We also performed sea tests to evaluate
the performance of the major components of the proposed
adaptive modem in a real environment.
CONCLUSION
This article makes a case for an adaptive acoustic modem in
underwater sensor networks. We describe the potential benefits
of the adaptive modem and describe a general digital hardware
platform architecture. We perform a set of experiments and
sea tests that quantify the benefit of different modulations,
types of channel estimation and symbol synchronization.
[attachment=28306]
INTRODUCTION
UNDERWATER sensor networks have a wide range
of oceanographic applications including marine exploration,
environmental monitoring and coastal surveillance. The
preferred mode of wireless communication in these networks
is based on acoustic signals. This is due to the fact that
radio frequencies suffer high attenuation underwater. Optical
communication is possible but only in clear water at relatively
short distances. Unfortunately, acoustic communication
is challenging due to large and variable multipath delay spread,
Doppler shifts and long propagation delays [1].
ADAPTIVE ACOUSTIC MODEM DESIGN
Underwater acoustic modems consist of three fundamental
components as shown in Fig. 1: a transducer, an analog
transceiver and a digital hardware platform for signal processing
and control. This article focuses on the design of the
physical layer on the digital platform.
SIMULATION AND SEA TEST RESULTS
To evaluate the proposed adaptive modem, we did both
simulations and sea tests. We executed a set of simulations
to find the best data rates for different links in a network and
to understand the potential benefits of modifying the data rates
on a per link basis. We also performed sea tests to evaluate
the performance of the major components of the proposed
adaptive modem in a real environment.
CONCLUSION
This article makes a case for an adaptive acoustic modem in
underwater sensor networks. We describe the potential benefits
of the adaptive modem and describe a general digital hardware
platform architecture. We perform a set of experiments and
sea tests that quantify the benefit of different modulations,
types of channel estimation and symbol synchronization.