MIT Creates Battery-Free Underwater GPS

MIT Creates Battery-Free Underwater GPS

If you need to know where you are, there’s a network of GPS satellites in orbit that can tell you with a high degree of accuracy. That is, unless, you’re underwater. The GPS radio signal dissipates quickly when it hits water, causing a headache for scientific research at sea. The only alternative is to use acoustic systems that chew through batteries. A team from MIT has devised a battery-free tracking technology called Underwater Backscatter Localization (UBL) that could end this annoyance.

Currently, scientists who want to track a drone or a tagged animal have to use power-hungry acoustic location technologies. These devices require batteries, which add bulk and limit the useful lifespan of trackers. Recharging batteries is often difficult, verging on impossible. If you’re trying to follow a tagged whale, for example, you probably won’t get close enough to swap the battery.

The technology was developed under the supervision of lead study author Reza Ghaffarivardavagh and Fadel Adib, who leads the research team. UBL still relies on sound waves, but it’s much more efficient about it. Adib and his team leveraged piezoelectric materials, a technique they previously used to create battery-free sensors (see below). These materials generate an electric charge in response to mechanical stress. In this case, the mechanical stress is the vibration from soundwaves.

The charge generated by the piezoelectric sensor allows the system to selectively reflect some soundwaves back into the underwater environment. Meanwhile, a receiver translates those reflections (the backscatter) into either a 1 (reflected) or a 0 (not reflected). Put that together, and you have a low-bitrate binary code. To turn this into location technology, an observation unit simply emits soundwaves and tracks how long it takes for the piezoelectric sensor to return the signal.

There’s a kink in this plan, though. Sound waves propagate in all directions, causing a messy acoustic environment that would be computationally expensive to analyze. The team devised a solution with frequency hopping similar to the approach that helps wireless networks avoid interference. The observation unit emits several different frequencies so the waves bounce back in phases, making the signal easier to parse.

The approach showed promise off the bat, but there were some additional challenges. To combat echoes in shallow water, the researchers found they could slow the bitrate from 2,000 bits/second to 100 bits/second. That’s still plenty for a location lock on slow-moving or stationary objects, but the team is still experimenting with higher bitrates (around 10,000 bits/second) for moving objects. Finding the balance between echoes and bitrate will take some time, but UBL could eventually lead to a boom in ocean exploration.

Continue reading

NASA Created a Collection of Spooky Space Sounds for Halloween
NASA Created a Collection of Spooky Space Sounds for Halloween

NASA's latest data release turns signals from beyond Earth into spooky sounds that are sure to send a chill up your spine.

Intel Launches New Xe Max Mobile GPUs for Entry-Level Content Creators
Intel Launches New Xe Max Mobile GPUs for Entry-Level Content Creators

Intel has launched a new consumer, mobile GPU — but it's got a very specific use-case, at least for now.

The Best Web Hosting Services for Creative Pros
The Best Web Hosting Services for Creative Pros

There are plenty of articles comparing standard web hosting sites, but most of those options aren't a great fit for creative professionals such as photographers, videographers, and graphic artists. We take a look at some of the offerings that are and share our experiences with them.

Scientists Create Ultra-Hard Diamonds at Room Temperature
Scientists Create Ultra-Hard Diamonds at Room Temperature

Natural diamonds only form deep in the Earth under intense heat and pressure, but researchers say they've developed a way to create diamonds at room temperature.