Packet-Based Ranging with a Low-Power, Low-Cost Acoustic Modem for Micro AUVs

The development of cheap micro autonomous underwater vehicles (uAUVs) offers an entirely new technology for monitoring of and maintenance in limnic waters. A vivid vision is that of autonomous swarms of muAUVs performing tasks such as spotting sources of environmental pollution, regularly examining of water quality, or assisting divers in dangerous missions. In this context, a primary focus has been set on underwater communication. While commercial products are prohibitively expensive or too large, we developed a low-power, low-cost acoustic underwater modem for communication. However, underwater distance assessment among muAUVs and relative or absolute self-localization are also mandatory for swarm formation and navigation. In this paper, we explore the ability of the modem to also perform the task of ranging as a preparation for our ongoing work on underwater self-localization. We employ a method for ranging that can be embedded into regular data traffic - hence adding neither extra communication, power consumption, nor hardware - but can also be used stand-alone. Furthermore, we present results of the ranging accuracy from both laboratory and real-world experiments and discuss influencing factors and practicability issues.