[ale] WIFI mystery speed problems

[Steve Tynor]

I'm looking for some brainstoming ideas to explain why my home wifi 
router's performance is suddenly acting so strange: periodically (about 
once a day), performance (as tested by speedtest.net) drastically 
decreases from ~30Mb/s to ~4Mb/s.

When this happens, there's nothing I can do to make it better. Rebooting 
the router has no effect.  The speed comes back when its good and ready 
- not before.  These "outages" usually last about 12 hours.  Performance 
is bad from all clients - macbook, ubuntu laptop, phones - so this seems 
to be router specific - not due to client config.

NOTE: tests via 10baseT wired connections are consistently at 29+Mb/s; 
wifi is 26-29 when good, when bad between 0.9 and 4Mb/s. When the wifi 
is bad, the wired results remain good: so this is a wifi problem - can't 
blame it on comcast :)

The router is an Asus RT-N16 running Tomato/Shibby.   Google shows 
others getting much better throughput with this hardware/firmware combo 
(70+Mb/s) so I don't think the router or firmware is likely to blame 
(unless I have flakey hardware ?)

I've been logging through a speedtest-cli cronjob for the past week and 
6 days out of 7, I see this behavior (performance degrades starting 
between 9pm and 2am, continues even after the router auto-reboots at 5am 
and then eventually returns to normal by about 9am.

Things I've tried:

  * I cannot identify any equipment in the house that might be causing
    radio interference - and certainly nothing that is on a periodic
    schedule that matches these overnight outages.
  * Reboot the router - has no effect.
  * Checked that this is not client specific. When the performance
    degrades, I measure the same throughput on all clients (laptops,
    phones).
  * There is no load on the wifi during these outages (no long running
    file transfers, backup rsync's or streaming).
  * I disabled bandwidth and ip monitoring (which I understand to be a
    known bottleneck in Tomato).  This improved the "normal" throughput
    a bit, but has not solved the periodic slow "outages".
  * I moved the router to a variety of locations (on theory that there
    may be some unusual interference on one location or the other)


I'm looking for ideas of more things to try before I reflash the 
original firmware and see if Asus's software works better... (followed 
by trash the asus and buy a new router :( ).

Help! (and thanks,)
Steve
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