Handoff insights with Prism2 driver: Part 2
victor.aleo at estudiant.upc.es
Fri Nov 8 12:15:41 EST 2002
After a very detailed study about the handoff using the Prism2 driver I still
cannot understand a very unexpected result.
First, the testbed consist of: 2 APs (with Prism2 driver) and 1 station (also
with Prism2 driver). The mechanism to force the handoff is switching off the radio transmitter of the old AP ("iwconfig wlan# txpower off").
Results: (I have a picture with all the detailed steps but I'm not sure if it is allowed to send it to the list, anyone knows?)
From the very first instant that I switched off the radio tx, the station goes on sending Data frames to the old AP as well RTS frames. This is the problem: this keeps going on during 2.2 seconds! After this 2.2 seconds, the station sends the first Probe request. Of course, the second AP answers it with a Probe response and the reassociation is done as usually without problems. This last step takes around 250 ms which was the expected.
My question: Is it this behaviour of the station normal? Thus, Why the station is waiting so long to send the first Probe request? Has anyone experimented a similar problem?
I will appreciate any kind of suggestions or comments.
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