Decreasing the txpower to a very low value

[sunny sunny]

Hi all,

I am creating a test bed for which I would like to decrease the
txpower of the AP (using hostAP drivers) below certain level so that
the client drops the connection. The client (or station) is about 2 m
distance from the AP.

AP and client machines are IBM T30 (using internal wireless card) both
using hostAP driver (version 0.0.4) .

I went over the older mailing list from which I could setup the
txpower level to a low value using
iwpriv eth1 alc 0; iwpriv eth1 txpower 127. 

This gives me the signal level of -100dBm (Noise: -139dBm, link
quality = 16/92) at the client. However the station can still ping the
AP pretty well. I would like to lower the power level gradually so
that the station would see a decrease in power level and finally see
the signal level drop to the noise level.

Any suggestions as in using specific card or some other setting would
be very helpful.

Thanks.
Santosh.