Application of maximum-length sequences to impulse response measurement of hydroacoustic communications systems

There is a growing interest in digital transmission of telemetry data on ultrasonic waves. The dependence of signal attenuation on squared frequency, specific to the hy-droacoustic systems, induces problems that do not exist in monochromatic, narrowband radio communications systems. For adapting the transmission parameters to current propagation conditions, a precise knowledge of instantaneous changes of channel performances is needed. Simulating and testing of broadband communications techniques require robust, reliable and efficient method of impulse response measurements in natural exploitation conditions. The paper presents the MLS (Maximum-Length Sequence) correlation method applied to impulse response measurements of electroacoustic transducers as elements of communication chain.