[Make-wifi-fast] Latency spikes every few minutes?

dpreed at deepplum.com dpreed at deepplum.com
Sat Mar 24 16:52:42 EDT 2018

My understanding, which may be wrong, is that a channel scan requires listening for either a packet or a beacon on each channel. Beacons being the longest you have to wait. But adding up across all the 5 GHz channels + 2.4 GHz channels, assuming most are unused, you get real long delays!

A better idea would be listening for beacons with a simple secondary receiver. That receiver could be a variable bandwidth front end, so it could listen on adjacent channel groups at the same time, in parallel with the normal stuff.

It would be even easier if you were only interested in newer and louder signals than the current one, because you could just open the channel filter bandwidth (getting worse SNR) and use SDR to sample for louder signals, if any.

Conceptually, what you probably want is good hints about what fallback channel you might switch to. Channel scanning one at a time is a poor, poor algorithm for that.

And even for fixed stations, propagation varies -- turn on a fan in the room causing time varying multipath distortion, or open a metal filing cabinet drawer. So a fallback is useful to have for quick association switching. However, the ideal thing at that point is to be associated simultaneously with multiple APs or mesh peers, and maybe even have DHCP leases with fallback nets.

-----Original Message-----
From: "Dave Taht" <dave.taht at gmail.com>
Sent: Fri, Mar 23, 2018 at 5:15 pm
To: "Rich Brown" <richb.hanover at gmail.com>
Cc: "Rich Brown" <richb.hanover at gmail.com>, make-wifi-fast at lists.bufferbloat.net
Subject: Re: [Make-wifi-fast] Latency spikes every few minutes?

On Fri, Mar 23, 2018 at 2:12 PM, Rich Brown  wrote:
> Hi folks,
> My Google-fu is weak today. I know that someone described the reason that some Wifi sees big latency spikes every few minutes. I remember it being related to an AP scanning something, for some reason, but that's all I remember. Could someone refresh my brain? Thanks.

> Rich
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> Make-wifi-fast mailing list
> Make-wifi-fast at lists.bufferbloat.net
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Dave Täht
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