A practical guide to chirp spread spectrum for acoustic underwater communication in shallow waters

Abstract

Small and cheap micro AUVs enable diverse underwater monitoring applications in shallow inshore waters; e.g., inspection of underwater assets, observation of water quality, and identification of pollution sources. The formation and collaboration of swarm members yet requires communication and self-localization based on cheap, miniature acoustic devices. However, this is severely hampered by the effects of multi-path propagation and scattering in shallow waters. In general, we discovered improvements of chirp-based---i.e., frequency-sweep---synchronization in these scenarios. This paper presents strategies to find proper chirp parameters. First, we study the benefits and applicability of chirp-based modulation against FSK. Second, we discuss the impact of the chirp parameters in real-world scenarios and identify sweep spots w.r.t. bandwidth to improve the standard deviation of the position in the time domain up to 86 % above this point. Third, we present instructions to choose these parameters in an efficient and appropriate way for any shallow water scenario.