✨ Nora Tindall  🪐

You've never seen thin-net jam when one station had a bad card and made everyone else think the network was busy and never free? CDMA only works when every station on the network obeys the rules (or minimally breaks them; was it the 3Com card that transmitted early? Not sure).

I think in any distributed comms system you have to have a commonly agreed system of rules I.e protocol

You sure not confusing with Ethernet? CSMA/CD? CDMA is something different, more like FDM in the digital domain.

Sorry, yes. But here we don't have a spectrum, we just have a single value. An infinitely variable value, but just a single value. So the jamming resistance of CDMA doesn't seem to apply; the jammer effectively blocks the whole range in one go with a single transmission.

Sure you have a spectrum. The voltage between ends of an antenna is a scalar, and it _does_ pick up all frequencies, although some more strongly than others; it's up to the rest of the circuitry to filter down to the one you care about. I think CDMA is a great idea here.

Then I'm clearly misunderstanding what you meant by "single value". An attacker doesn't need to block values in the spectrum between 50->100 or 100->200 or... they just need to keep asserting 42, and if they do it quicker than you can sample and read then you'll only get 42.

Yeah, apologies - that was maybe unclear. If you think about something like the electromagnetic field (which is a vector field), you can measure its value at any time at a given point in space. By measuring rapidly (at some frequency S) you are able to observe multiple signals...

... of any frequency below S/2 (by Nyquist). This is a similar idea, except without the requirement of "any point in space"; it's as if when you put up an antenna, you got the same stations, no matter where in the universe you are.