Implementation of an adaptive burst DQPSK receiver over shallow water acoustic channel

In an environment such as underwater channel where placing test equipments aredifficult to handle, it is much practical to have hardware simulators to examine suitablydesigned transceivers (transmitter/receiver). the simulators of this kind will then allowresearchers to observe their intentions and carry out repetitive tests to find suitable digitalcoding/decoding algorithms.in this paper, a simplified shallow water digital data transmission system is first introduced.the transmission channel considered here is a stochastic dsp hardware model in whichsignal degradations leads to a severe distortion in phase and amplitude (fades) across thebandwidth of the received signal. a computer base-band channel model with frequencynon-selective feature is derived by the authors [10-11]. this system was based on fullraisedcosine channel modelling and proved to be the most suitable for vertical and shortrangeunderwater communication csdfher), with a reflected path (specula component, whenthe acoustic hydrophone receives reflected signals from surface and bottom of the sea) anda random path (diffused component, when the acoustic hydrophone receives scatteredsignals from the volume of the sea). the model assumed perfect transmitter-receiversynchronization but utilized realistic channel time delays, and demonstrated the timevaryingcharacteristics of an underwater acoustic channel observed in practice. in thispaper, they are used to provide a full system simulation in order to design an adaptivereceiver employing the most advanced digital signal processing techniques in hardware topredict realizable error performances.