FTP PUT sometimes crap performance

Question

Hi,
The Windows Status window on XP Prof. says data rate 54M (.11g).
When I'm not transfering data to or from the wireless client roaming behaviour, when client is not physically moving, is stable, predictable and intuitive.
I'm testing FTP GET and PUT from a wireless client.
The test file is 32MB in size which I've uploaded and downloaded from a data centre host many times over several days.
FTP GET always takes about 20seconds.
Data rate as reported by Windows Status window stays at 54Mbps.
Client does not roam from the AP it's currently Associated with (it is not being moved during these tests).
That's all fine.
The FTP PUT of the same file for most runs of the FTP PUT test file transfer takes about 20sec. which is fine.
Data rate as reported by Windows Status window is mostly stable at 54Mbps.
Client mostly does not roam from the AP it's currently Associated with (it is not being moved during these tests).
However sometimes with an FTP PUT the data rate as reported by Windows Status window wanders all over the place (6M, 18M, 24M, 36M, 48M, 54M).
and sometimes the client roams to a neighbouring AP.
These 2 instabilities (data rate & roaming) only happen during the FTP PUT.
It happens about 1 in 20 test FTP PUTs.
Has anyone seen similar behaviour?
Any clues as to the reason for this behaviour and possible solutions?
Client is HP Laptop NC6220 with Intel 2915AG wireless card built-in with latest driver 9.0.4.33
Wireless infrastructure is Cisco WiSM (s/w ver. 4.0.179.11) with 1131AG APs.
Thanks for any help.

Answer 1

Network as such is fine since FTP Get is working fine. Generally reason for the client roam is Signal Strength in which case you could try to increase the Access Point and see if this happens again.