Ask HN: Why WiFi switching is so hard for iPhone?

https://news.ycombinator.com/item?id=31796180

by garyfirestorm • 4 years ago

12 17 4 years ago

news.ycombinator.com

I have a main router and since my back patio and garage don't get the WiFi coverage, I have installed a range extender. Whenever I visit the garage my iPhone 12 Pro Max doesn't seem to switch to the range extender, I have to manually open WiFi settings and click on it for it to connect. Now I go back to my living room and sit right next to my main router, my phone is still talking to the range extender even throws poor connection/no internet (!) and I have to walk again through the settings and select my main router. Is it that hard to automatically switch between saved Access Points based on relative signal strengths?

jackweirdy• 4 years ago

Are your SSIDs named the same or differently?

If you name them the same, they should auto-switch more aggressively, but probably still not optimally.

For that communication between the routers is needed and each will kick you over to the other when they agree it’s necessary

Recommended reading: https://support.apple.com/en-gb/HT202628

garyfirestorm2• 4 years ago

They were named differently. Main being Router-5G and extender is Router-5G_EXT. Like you suggested I changed the name of the extender to main routers SSID. I’m already seeing improvements. I thought ‘what’s in the name’

bradknowles• 4 years ago

Amplifi has both "band steering" and "router steering" options that you can configure on the routers.

Band Steering will cause the routers and access points to kick you off 5Ghz faster, if 2.4Ghz would give you stronger signal, and vice-versa.

Router Steering will cause the routers and access points to kick you off the one you are attached to more quickly, and thus cause you to re-associate with the network on a router or access point that is closer to you and would give you a stronger signal.

I can't speak for any other vendors, but that's the kind of thing I think you're looking for.

desro• 4 years ago

The roaming protocol prioritizes the continuity of the connection you already have until signal strength (or another metric) falls past a certain threshold.

I tried to find the Apple whitepaper I read about this exact topic a couple years ago, but couldn't find it. Hopefully someone with more precise insight can chime in.

One practical solution may be to reduce the signal strength of each of your access points so the threshold for jumping APs is hit more easily.

capableweb2• 4 years ago

until signal strength (or another metric) falls past a certain threshold

Not sure that is working correctly/using the right metric/using the right thresholds if what OP is saying is true.

my phone is still talking to the range extender even throws poor connection/no internet

Seems like if you're sitting right next to another AP while being connected to one that you're almost fully out of range of, it should be switching to the closer AP already.

Or, scary thought but hear me out: Let users configure the threshold themselves so users can configure it to what works for them. But this is Apple we're talking about, so probably impossible to implement.

daviddever23box3• 4 years ago

Too complicated. Why not simply get a WiFi system that works? Or, have someone who knows what they're doing set it up.

There seems to be quite a bit of engineering AROUND the problem, without actually dealing with it head-on.

seaghost• 4 years ago

You should get a WiFi mesh system, I had the same issue and it solved it.

webmobdev• 4 years ago

It's even worse with hidden wifi network. Other devices don't have an issue with hidden netowrks but iDevices always delay connecting to a hidden wifi network.

garyfirestorm2• 4 years ago

Mine is not hidden but thanks for the info

cr3ative• 4 years ago

Your transmit power is too high on both units. Turn it down and it’s more likely to notice the drop, rather than see a strong signal it can’t actually reach.

daviddever23box3• 4 years ago

Not a fan of range extenders; definitely a fan of (carefully-selected) fixed-frequencies, distinct SSIDs on unique APs, and per-MAC rate limiting. Use wired Ethernet wherever possible. Choose the physical placement of your APs wisely.

As for mesh networking, nice to have in the suburbs, though never as good as a fully-managed, wired-AP solution, especially in Manhattan high-rises.

jhugo3• 4 years ago

You should set a higher minimum RSSI on your APs, and/or reduce their transmit power. Also, ensure they have the same SSID. With different SSIDs you are not roaming and it won't consider switching until it completely loses the connection of the first.

toast0• 4 years ago

I haven't seen good results with minimum RSSi; if the client has chosen an AP to connect to, denying it's attempts is mostly going to cause delay; maybe it will chose another AP after, but maybe this is the only AP it can see, and low signal is better than nothing. Although, maybe some systems are better at it than the ones I've used.

Reducing Tx power seems to help a lot more. Default high power Tx seems to send beacons farther than most clients can successfully negotiate anyway; some APs get distortion at higher power, so useful signal is strictly lower (but you can see the beacons farther!), and clients seem to be looking at the signal strength (rather than signal quality) as a sign to scan and roam, you want to make sure strength isn't so high that roaming is avoided.

jhugo3• 4 years ago

I haven't seen good results with minimum RSSi; if the client has chosen an AP to connect to, denying it's attempts is mostly going to cause delay; maybe it will chose another AP after, but maybe this is the only AP it can see, and low signal is better than nothing. Although, maybe some systems are better at it than the ones I've used.

This comes down to the overall system design. If a client could have a usable connection with an RSSI below the minimum and can't see any other APs then either a) your minimum RSSI is too high, or b) you don't have sufficient or correctly placed APs to cover the desired coverage area.

jhugo3• 4 years ago

Reducing Tx power seems to help a lot more. Default high power Tx seems to send beacons farther than most clients can successfully negotiate anyway; some APs get distortion at higher power, so useful signal is strictly lower (but you can see the beacons farther!), and clients seem to be looking at the signal strength (rather than signal quality) as a sign to scan and roam, you want to make sure strength isn't so high that roaming is avoided.

Yes, one common effect of too-high Tx power is that the clients can hear the AP beacons but the AP can't reliably hear the clients, causing the clients to repeatedly try to associate. Most clients will backoff a given BSSID after a few association failures though. Ideally you set your Tx power to just slightly overlap the next AP. A lot of gear doesn't properly implement fast roaming though, in which case proper RF design will result in clients disconnecting for noticeable periods of time around the borders between APs. It's more often the base station gear's fault than the end-device's fault; in particular Apple's recent gear roams really well on a properly designed and implemented network.

Ask HN: Why WiFi switching is so hard for iPhone?

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