More APs with single SSID

Milan Krčmář krcmar at datinel.cz
Sat Jan 26 15:07:27 EST 2013


Hello and sorry for a more general question which is not directly
connected to hostapd.

I have tried to solve it many times again and again in last years: I
have several APs in a single building, all connected to a shared
ethernet segment, all broadcasting the same SSID.

STAs, typically Windows XP/7 notebooks, often associate to a
particular AP and preserve the association as long as possible: you
can move such an STA to another AP, which has stronger signal, but the
STA stays associated to the original AP, even if it has a very weak
signal - the STA just lowers modulation speed to cope with the weak
signal. The STA stays associated to the weaker AP for tens of minutes
- until the user loses patience and chooses to disconnect from the
SSID and reconnect again. Then only STA associates with the stronger
AP.

I would like to solve this general problem for future deployments. In
general, we can use Linux-based APs with recent Atheros Wi-Fi SoCs, so
we can adapt them fully to our needs. This is very problematic even
with small setups: four rooms, strong walls, three APs, user moves
with his notebook/smartphone from one room to another and is forced to
manualy switch off/on the Wi-Fi to associate with stronger AP within
the same SSID. Some users even prefer to use different SSIDs and have
full control over the unreliable roaming.

The only solution I think I have found so far is to watch STA's signal
on AP it is associated with and kick the STA when the signal falls
below some pre-defined level. Have I missed any better solution?

Milan


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