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Full Reconfiguration of Underwater Acoustic Networks through Low-Level Physical Layer Access

Underwater acoustic communications experiments often in-
volve custom implementations of schemes and protocols for
the physical and data link layers. However, most commercial
modems focus on providing reliable or optimized communi-
cation links, rather than on allowing low-level reconfigura-
tion or reprogramming of modulation and coding schemes.
As a result, the physical layer is typically provided as a closed,
non-reprogrammable black box, accessible by the user only
through a specific interface. While software-defined modems
would be the ultimate solution to overcome this issue, having
access to the symbols transmitted by the modems using a
proprietary modulation format already opens up a number of
research opportunities, e.g., aimed at the cross-layer design
and optimization of channel coding schemes and communi-
cation protocols.
In this paper, we take the latter approach. We consider the
commercial EvoLogics modem, driven by a custom firmware
version that bypasses the channel coding methods applied by
the modem, and allows the user to set the transmit bit rate to
any desired value within a given set. This makes it possible to
evaluate different coding schemes in the presence of different
bit rates. Our results show that the custom firmware offers
sufficient flexibility to test different configurations of the
coding schemes and bit rates, by providing direct access both to correctly decoded and to corrupted symbols, which can be
separated at the receiver for further processing. In addition,
we show that the DESERT Underwater framework can also
leverage the same flexibility by employing low-level physical
layer access in more complex networking experiments.

Authors:

Filippo Campagnaro, Roberto Francescon, Oleksiy Kebkal, Paolo Casari, Konstantin Kebkal, Michele Zorzi

Published On:

WUWNet’17 Halifax

Publication Year:

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