Reliable mobile underwater acoustic communication systems must compensate for strong, time-varying Doppler effects. Many Doppler correction techniques rely on a single bulk correction to compensate first-order effects. In many cases, residual higher-order effects must be tracked and corrected using other methods. The contributions of this paper are evaluations of (1) signal-to-noise ratio (SNR) performance from three Doppler estimation and correction methods and (2) communication performance of Doppler correction with static vs. adaptive equalizers. The evaluations use our publicly available shallow water experimental dataset, which consists of 360 packet transmission samples (each 0.5s long) from a five-channel receiver array.
Abstract-Underwater acoustic communication (ACOMMS)is critical for many applications including marine science, oceanographic exploration, offshore surveying/drilling, and military uses. ACOMMS data rates are usually limited by multiple propagation paths with different time delays and Doppler characteristics. It is often difficult to coherently recombine all paths, especially in shallow water, leaving incoherent paths that interfere with the receiver.One way to suppress unwanted paths is with a directional receiving array. Indeed, many existing large, directional acoustic arrays could be used as ACOMMS receivers.In a number of these arrays, wideband monopulse outputs could be made available. These directional beam outputs, in monopulse pairs, can selectively suppress, or even null, offending multipath when combined with a simple scalar weight. Using an experimental system, we show how a relatively short equalizer, using as inputs the wideband monopulse beam outputs of a large array, can form the backbone of an ACOMMS system that performs effectively in a multipath-limited environment. Our contributions include (i) a multipath-Doppler channel model validated by experimental results, (ii) a receiver design that utilizes monopulse processing, and (iii) an analysis of its performance using simulated and experimental data.
0 5 10 15 0 0.5 1 0.2 0.4 0.6 0.8 1 S y s te m ti m e ( s ) Ch an ne l im pu lse re sp on se (m s) Direct path First echo Reverberation Fig. 1. Channel impulse response magnitude variation vs. time from a boat to a stationary platform at 820 ft (250 m) range. The direct path and first echo are approx. stationary over the system time whereas the reverberation varies largely over the system time.
ABSTRACTCoherent underwater communication systems in shallow water must compensate for several impairments, including Doppler shift and reverberant channels. In this paper, we quantify tradeoffs in communication performance vs. computational complexity in designing receivers to compensate for these impairments. Our communication system is unidirectional, single-carrier, wideband, and packet-based. We use 1.5 hours of recorded data from an experimental system on a public lake with a moving transmitter and stationary receiver. Our contributions include acoustic channel modeling and a tradeoff analysis for Doppler shift estimation, multi-stage equalizers and sparse equalizers. We compare multi-stage and sparse equalizers against traditional equalizers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.