check the paper:
"On the side effects of proprietary solutions for fading and interference mitigation in IEEE 802.11b/g outdoor links"

Hi, I tested iwlagn driver for 4965agn of T61 before. The SNR is similar to
your figure.
But I do not test ath5k.



On Tue, Oct 12, 2010 at 5:04 PM, Wenhua Zhao <> wrote:

> Hi,
> We recently find some issues with the transmitter signal level.
> In the tests, an AP running madwifi driver transmits packets to a
> station running intel iwlagn driver.  In the iwlagn receiver, we
> create a monitor interface and use tcpdump to collect the SNR of the
> packets.
> Attached figure shows the SNR.  X-axis is the packet number and Y-axis
> is the SNR.  The figure shows periodic dips of SNR.  Tests for madwifi
> ad-hoc mode have similar results.
> When ath5k is used for AP/ad-hoc, there is no such dip.
> Did anyone see similar behavior before?
> Regards,
> Wenhua