Reliable Symbol
Synchronization in Software-Driven Acoustic Sensor Networks
R. Jurdak, A.G. Ruzzelli, G.M.P.
O’Hare, and C.V. Lopes
Abstract
Symbol
synchronization in traditional hardware-driven communication systems has relied
on the transmission of training sequences of symbols just before the beginning
of the frame symbols. The use of training sequences is not suitable for
software-driven communication systems, such as lightweight acoustic underwater
sensor networks [4, 5], in which the high symbol loss rate may cause the loss
of training symbols, preventing accurate symbol synchronization.
Software-driven communication networks require symbol synchronization that is
resilient to a high loss environment, that does not represent large
communication or processing overhead, and that is
tunable to the noise profile of different environments. These requirements are
emphasized for mote-based acoustic underwater sensor networks in which the
bandwidth and processing capability are sparse. This paper proposes the use of
a short signature synchronization symbol (S4) as both a preamble
and post-amble to enable receiver synchronization in mote-based acoustic
communication systems that rely on software modems. To synchronize to an
incoming signal, the receiver performs cross-correlation of N reference
signature symbols, generated apriori through the mote
hardware, with the incoming signal to identify the beginning of the preamble
and post-amble. The output of the cross-correlation yields 2N peak values, from
which the receiver chooses the sharpest and most symmetric for synchronization
to the beginning of the frame. Empirical experiments confirm that the
synchronization accuracy for the S4 is within 5 ms in air within a range
of 10.5 m, and 11 ms in water within a range of 15 m.
In proceedings of IEEE GLOBECOM,