MIT Sends a Battery-Free GPS Underwater
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2020/11/06 08:57:00
Based on RF communication, GPS devices communicates with satellites to determine their location via trilateration. Besides vehicle navigation, if there were ever an application that would benefit from GPS technology, it would marine travel.
In the middle of the ocean, knowing a submarine’s location is absolutely essential. Unfortunately, conventional GPS does not work underwater and alternatives are power-hungry. Now, researchers at MIT may have come up with a solution, offering underwater localization without the need for large amounts of power.
Problems With GPS Underwater
GPS relies on RF communication, which refers to the transmission and reception of EM waves. While RF works just fine in the air, seawater presents a unique challenge because it is a highly conductive medium. The conductive nature of the water means that the medium offers high absorption and subsequently high attenuation, making it completely unfeasible for RF communication.
One of the major concerns of an underwater GPS is acoustic communication because it requires a large amount of power and replacing or recharging batteries in a submarine may not be entirely practical. In an attempt to address this problem, researchers at MIT have announced a new technique that they claim is a step towards battery-free underwater communication.
The working principle of the new technique called underwater backscatter localization (UBL) is that instead of emitting its own acoustic signals, it reflects modulated signals from its environment.
The technique uses piezoelectric material to generate charge as a result of its interaction with environmental acoustics. Then the material uses that charge to selectively reflect some soundwaves back into the environment.
A receiver translates that sequence of reflections, called backscatter, into a binary string where "1" represents acoustic signals being reflected, and "0" represents acoustic signals not reflected. The technique can relay information about the environment, perform localization using a time-of-flight clocking technique, and even track objects underwater.
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