this post was submitted on 22 Sep 2023
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802.15.4a/ab/ac, seems even weirder, given what we've become used to with AM/FM signaling modes.
After the usual "Huh, that seems like a clever way to send signals" reaction, a closer perusal of the tech & its established industrial capabilities, reveals Surface penetrating radar for machine vision & medical imaging, P2P, P2MP, local file-exchange, low-power low-latency streaming, greater range than bluetooth, greater interference resistance than WiFi, & reduced airtime per Mb, at lower emission power than a hair dryer or cellphone.
Gee, I wonder why it got forcibly channeled into exclusively device-to-device location pings, with no direct radio access or firmware, available to devs?
Seriously, go look at what the military, industrial, security, & medical sectors have already been doing with UWB, then look at the specs for the compact chipsets & SOCs released since 2017, & then look at what BMW, Apple, Google, & Samsung are doing with it. Oh yay, Airtags. I mean, they do work, but they're about 1/1000th of what the U1 could do, if app devs had access to the radio instead of being gatekept behind the FindMy device-to-device services.
Even plain old wifi is fascinating in terms of signaling, they use ofdm, or orthogonal frequency division multiplexing to encode data. The whole concept is crazy.
To summarize, the waveform (sine wave) is measured by degrees from zero, where 90 is the peak, 180 is when it crosses the middle line again, 270 is the trough, and at 360 it returns to zero. What OFDM does is interrupt the normal sine wave and jump from 90 to 180 to encode bits.
What gets crazier is that this is divided into dozens of different positions that represent different bit encodings. Then they go more crazy and run... I think it's 10 by 2mhz wide carriers, all doing this same thing (for a 20mhz wide channel width) to encode more data into the bandwidth.
Then they get more crazy and implement AM on top of it, so you get high power OFDM and low power OFDM divisions that can do upwards of double the symbols on the same carrier.
The wizardry to make all this work is insane, and the fact that we've mastered it to the point where we can sell wifi cards for something like $20 USD just kind of blows my mind. This is crazy to me!
Airtags is just bluetooth WiGLE for one vendor