Not very high power usually. They're usually made of piezoceramics.
I think they're expensive because they're niche. Narrow band piezoceramics which are used in fish finders and other commercial equipment are pretty cheap. These wider band transducers are niche to underwater comms.
> Also what frequency does an acoustic modem typically use?
Usually in the 10s of kHz. The NATO JANUS standard is around the 12kHz center frequency.
Subnero | Singapore | Full-time | Systems Software Engineer | embedded / Linux + C, Julia, Rust
Subnero (https://subnero.com) is a Singapore-based company creating in-water wireless networks. We create innovative products (hardware and software) at the cutting edge of underwater communications and networking. Our products are used in environmental monitoring, offshore oil and gas, and defense industries.
We're looking to hire a Systems Software Engineer to join our team. Our devices run embedded Linux and our software stack interfaces deeply with hardware. We're looking for someone to join the team in maintaining and improving the embedded side of our software stack. We're looking for someone comfortable working with Linux, device drivers, and hardware APIs. Experience with Julia and Rust would be a plus.
Yea. It's Singapore's form of protectionism, if we want to hire foreigners we need to first post it on MyCareerFuture and show that we tried to hire locally before we looked at around the world. Anyway, just email career@subnero.com and I'll make sure it reaches the right person.
While illumos carries a port of bhyve which is largely similar to upstream FreeBSD, there are several areas where it diverges. Propolis (the userspace VMM component) relies on some of those differences to function, especially when it comes to live migration.
Not technically a startup anymore, (our bizdev manager likes to call us a "grownup startup",) but we're making underwater acoustic wireless communication devices. We're taking a more software defined approach allowing us to be much more leaner, flexible and do more more IoT-esque things in an underwater wireless network.
It's an strange but interesting field. Loads of real, physical problems still left to solve and space for innovative solutions. Lots of hard engineering (software, hardware, etc) to do. But the marine tech industry is traditionally very slow to adopt any new technologies. Makes for some fun conversations. :P
One of my pet peeves is that the Linux SPI driver framework has a very transactional API. You can read/write N bytes to a bus at a time.
Some SPI devices can stream out lots of data on the bus. I’m looking at you ADCs.
It’d be nice to have a stream style API for that. Not sure which Linux framework is best suited for that. Maybe IIO but something on those lines might be fun to explore.
JANUS looks great on paper, but is pretty restrictive for doing anything useful in real life.
At the standard frequency bands they've chosen (9440-13600 Hz), with the type of coding scheme they use FH-BFSK, the bandwidth is too limited (4KHz -> ) to do anything except service discovery.
Having said that, I agree, it should have been mentioned.
The article doesn't mention OSC Bundles, which is a group of OSC messages which are designed to be 'interpreted' together. A bundle usually has a timestamp associated with it.
I agree this might not be the best method of dealing with out of order reception of packages, but it does exist in the protocol.
I think they're expensive because they're niche. Narrow band piezoceramics which are used in fish finders and other commercial equipment are pretty cheap. These wider band transducers are niche to underwater comms.
> Also what frequency does an acoustic modem typically use?
Usually in the 10s of kHz. The NATO JANUS standard is around the 12kHz center frequency.