I had this thought just now at the gym. I noticed multiple people, myself included, using wireless earbuds during our workouts – specifically AirPods.
My question is, if multiple people are using AirPods that work on the same frequency/signal, how come our music doesn’t all interfere with each other? How do each of our phones/AirPods differentiate from the others a few feet away from me?
In: Engineering
Digital communications over radio frequencies might as well be magic compared to the beginning of radio back in the 1920s or so. CDMA (code division multiple access) technology which is the part of most protocols effectively just transmits a signal into a giant pile of noise from everything else. The other side of the transmission is decoded by just mathing the hell out of what that noise consists of. Multiple sites just broadcast over each other and filter out what isn’t theirs.
The frequencies that unlicensed devices operate in (433MHz, 900MHz, 2.4GHz, 5GHz and others) are cesspools of transmissions from everything and anything. Somehow we have used an alchemy of physics and math to make it work.
That’s just the transport layer for communications, once you get beyond that you enter encryption and other protocols for actually transmitting useful data.
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