Adaptive PPM Acoustic Detection in very Shallow Water Reservoir

Underwater acoustic communications can be used for several applications. When the underwater link is related to a reservoir, applications can go from water monitoring, both in terms of pollution and physical characteristics, as for example, temperature. Another class of applications can be the remote control of small vehicles/vessels. Due to the limited depth, this kind of underwater acoustic connection suffers from delay spread and, in a wider sense, intersymbol and/or interpulse interference. In this work we analyze the problem of delay spread and test the performance in terms of BER for single link in a reservoir when 16-PPM is used according to Desert Star Systems LLC SAM-1 Modem. We propose also an adaptive detection scheme so as to reduce bit error rate. Last we compare the performance of the modem in the receive mode with a hybrid receiver characterized by hardware/software operations.