Acoustic Communication System for Underwater Wireless Sensor Networks Underwater communication Ra´ ulS´aez,AntonioS´anchez,RicardoMercado, ` Angel Perles, Pedro Yuste, Juan Vicente Capella, Sara Blanc, Vicente Busquets, Juan Jos´ e Serrano, and Rafa Ors Instituto ITACA, Universitat Polit` ecnica de Val` encia, Camino de Vera s/n, 46022 Valencia, Spain; e-mail: ucert@upv.es; website: http://ucert.upv.es Abstract. Underwater wireless sensor Networks (UWSN) provide a va- riety of attractive working fields such as aquaculture, offshore exploita- tion and underwater monitoring. These applications require spreading an important number of nodes which requires to develop simple, reliable and energy efficient modem architectures to reduce the economical cost, the developing time and the power consumption, still being efficient and robust. This paper overviews research efforts of our research team conducted during the last year to develop an acoustic communication system for UWSN. To address the cost and power consumption limitations, the de- sign and the implementation of a low cost and energy efficient underwater modem and a new acoustic-triggered wake-up system were researched. The result of combining both researches resulted in the development of ITACA-S1000 modem, a solution with a very low power consumption and with a very advanced remote wake-up system. Since this modem was the first coherent FSK solution presented to date, it was necessary to reach a new optimal multipath and Doppler-shift correction algorithm for co- herent FSK modem architectures with resources and power limitations to archive an efficient and robust communication. Keywords: underwater wireless sensor networks; acoustic modems; uwsn; underwater sensor networks; wake-up 1 Introduction Underwater Wireless Sensor Network (UWSN) development is of current inter- est due to the potential variety of attractive working fields such as aquaculture, offshore exploitation, biological monitoring as well as water and seafloor pollu- tion,seismicactivityandoceancurrents.Applicationsofthesefieldsmayrequire one or more of the following: short range underwater communications between collaborative devices; short/medium range communications between sea bottom 82 C.Fernandez-Llatas and A. Bonastre (Ed.): Workshop on Innovation on Information and Communication Technologies (ITACA-WIICT 2014) ISBN 978-84-697-1166-8