Unless the Roku behaves differently from every other Wi-Fi device, I don’t think there’s anything sinister or mysterious going on.
The Roku has one Wi-Fi radio. When it associates with the Internet Wi-Fi, the radio gets tuned to that channel.
When the Roku creates a Wi-Fi Direct SSID, it uses the same channel, because the only radio is already on that channel. It doesn’t assume the Internet AP knows anything and it doesn’t “chase” that SSID. I just IS on the same channel.
Wi-Fi uses CSMA/CA to sense other activity and avoid interfering with it. The Roku, like other Wi-Fi devices, literally listens before transmitting. It will delay transmitting if it hears somebody else talking. That’s how the spectrum is shared. It’s also how Wi-Fi can share the spectrum with non-Wi-Fi devices. (It’s ALSO why non-Wi-Fi devices that don’t use CSMA/CA can hurt Wi-Fi devices so badly - they don’t take turns.)
This is true when there’s one AP and multiple clients on a network; everybody listens before transmitting. CSMA/CA also works pretty well if there are two different APs on the same channel. The APs aren’t in charge of who can talk, anyway. So it doesn’t really matter if there’s one AP or two or 5. Everybody listens before transmitting.
That screenshot describes ACI - Adjacent Channel Interference. ACI is kinda harder to deal with, and happens in partially overlapping systems. It somewhat defeats CSMA/CA, because devices can’t “hear” each other consistently. You end up broadcasting garbage or getting talked over and getting errors.
I have no idea what the Roku is doing to avoid ACI. None of those look SUPPRESS THE ACCESS POINT or SCREAM LOUD or BREAK WI-FI, and that would be pretty foolish of the Roku. I also haven’t found any explanation of what those settings do, and I’m very curious! One strategy in noisy Wi-Fi environments is to use tiny packets, so that if others are talking on top of you, your packets take less time to make it through. That doesn’t negatively impact others. Another strategy is to break the Wi-Fi protocol and not wait your turn before sending - that does hurt others, but only when you are transmitting data. If anybody breaks Wi-Fi like that they deserve to be shamed.
Two APs on the same channel have little negative impact on each other if the channel isn’t saturated. Everybody takes turns, and it’s almost the same as if they were all joined to the same AP.
There are some bad ideas about how to do Wi-Fi spectrum management out there. There are even some APs that have dumb ideas about how to choose channels, and that “run away” (change channels) if they see another AP in the same frequency. Or if the other AP in the same channel is “loud” - whether it is active or not. Being able to hear another AP clearly is GOOD, because it’s easier to avoid talking on top of each other.
Obviously the ideal situation is to have no overlap at all. But the existence of another AP isn’t a good reason not to choose a channel. What matters is spectrum utilization. Access Points that change channels because they hear other APs are a special kind of stupid.
I see a few comments from people saying that the Roku Wi-Fi Direct interferes with their system, and that turning it off helps. I can’t argue with that. They also frequently say “I can see the SSID”, which is to be expected, and “My system changes channels automatically”, which is an indicator that they’re changing channels for the wrong reasons. “The FCC should be involved” is just a huge red flag. So is “I have lots of repeaters so I should have strong signal”.
My surprise is that the amount of traffic for a remote control should be very very low, and even more so if it’s just advertised but idle. If the existence of another (idle) AP causes another Wi-Fi network to totally collapse, something is already very wrong. I mean … definitely address the symptom, but maybe investigate the underlying problem, too?
I’m not claiming that two networks won’t contend for airtime. They absolutely will. But they should do it in a very predictable way, and it should be very similar to just having all of the devices on the same network in the first place.
And I’m not claiming that people haven’t had problems. I’m saying this pushes my “technology voodoo” buttons. I’d love to know what was really happening to those folks. I’d love to know what those settings actually do. There are tons of badly behaved Wi-Fi devices. Maybe the Roku is one, or maybe affected people had other badly-behaved Wi-Fi devices.
I haven’t been able to find an explanation of the Roku ACI settings or an explanation of what the Roku was doing wrong and why these networks were being so significantly impacted.
I love this stuff. Understanding how things go wrong is really interesting to me.
