WDS and TX rates, signal measurements

Jouni Malinen jkmaline at cc.hut.fi
Sun Jun 8 21:15:42 EDT 2003


On Sun, Jun 08, 2003 at 09:29:24AM -0400, Sergio M. Ammirata wrote:

> There are a few issues that are still pending in the latest CVS code:
> 1) The default value for basic_rates is 3. Shouldn't it be 15?

No, the default basic rate set should be 1 Mbps and 2 Mbps. This is
required for compatibility with IEEE 802.11 (i.e., non-802.11b)
stations. Basic rates are used for multicast/broadcast, ACKs, RTS/CTS,
but most unicast frames can use higher rates.

> 2) WDS link autorate negotiation does not work with hostapd (it stays
> stuck at 2Mbit) but it does in kernel mode. When I look at the stats of
> the neighbor in /proc/.. I see that that the supported_rates are blank
> when you use hostapd and they are filled in correctly in kernel mode.

Which method do you use to add WDS links? Kernel driver is not
processing beacon frames when hostapd is used, so it cannot
automatically get the supported rates list. However, when the station
entry for WDS peer is added with iwpriv wds_add or based on incoming WDS
frame, supported rates are set to 1, 2, 5.5, and 11 Mbps. I did not see
them blank in any of my tests with hostapd running.

Anyway, I think I will change the driver to process beacon frames even
when hostapd is running

> 3) Did the signal measurement conversion change? Before, the noise level
> was around -100Dbm, now it is around -30Dbm.

If I remember correctly, I changed at least one of the signal quality
conversion to use new function. This should match with the numbers
reported by latest firmware versions. It will most probably give
incorrect values for older firmware versions.

Unfortunately, these numbers seem to vary a lot based on both hardware
model and firmware version. In addition, they are not documented very
well. I do not have enough interest and energy in going through all the
possible combinations in search of the correct value..

-- 
Jouni Malinen                                            PGP id EFC895FA



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