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Wifi has an "interference robustness" option which is designed with microwave ovens in mind. The power output of a microwave is a sine wave, because it's power
by jrockway 3y ago
Wifi has an "interference robustness" option which is designed with microwave ovens in mind. The power output of a microwave is a sine wave, because it's powered from your AC line power, and doesn't emit energy during the zero crossings. "Interference robustness" times packet sends (and lengths) to be when the microwave is producing the least amount of power. Thus, you spend half of every 60th of a second irradiating your food, and the other half downloading videos. (Needless to say, having this on and your microwave going in the background reduces throughput. But, dropped packets are worse than small packets that always get through, and this aims to eliminate completely stomped-on packets.)
Wifi also has a listen-before-talk model. If it "hears" a microwave running, it thinks it's another station transmitting, and backs off. This feature of the protocol is why long-range networks worked so poorly in the past. If station A can't hear station B, but the AP can hear both of them, then A and B are going to step on each other and the AP won't be able to communicate with either station. This is why the "enterprise" way of deploying networks was to have a ton of access points running at low power; that works well with the listen-before-talk model since the AP likely can't talk to or hear stations that are too far away for the stations in its range to hear.
I don't know if interference robustness still exists in modern standards, as I haven't seen it in a control panel for decades, but it was definitely in 802.11b. I have never tested Bluetooth (or read the standard), but basically... the industry knows this is a problem, and handled it a long time ago. Bluetooth might ignore the problem because it plans on frequency-hopping (away from the microwave) anyway, but like all software, that can easily be bugged.
- function_seven 3y agoI have an inverter microwave. Before I went crazy with APs around my house, that microwave would win the war; no zero-crossings to sneak a packet by it. Now my bluetooth only drops when I'm fairly close to the microwave as it runs. (EDIT: my WiFi, not my Bluetooth)
- mikestew 3y agoAre you saying that adding WiFi APs improved your Bluetooth connections when the microwave is running? Or is there such a thing as Bluetooth APs? Pardon my confusion.
- function_seven 3y agoWow. I have no idea how I confused that. Yeah, the WiFi is improved. The Bluetooth is the same as it ever was. I pardon your confusion.
- mikestew 3y agoCool, I just thought I was missing out on something. :-)
- RF_Savage 3y agoThere is also a fun regulatory hack in bluetooth. As it is frequency hopping, FCC considers it spread spectrum, but only if it hops across a large enough set of channels. This matters because spread spectrum radios can run significantly more power. Bluetooths frequency hopping system avoids interference to it and from it by dropping channels with interfernce or other users from the hop set. So with enough interference, even monentary interference and the hop set reduces and regulatory limits require dropping power from 100-200mW to 25mW. This usually cuts the connection.