Singal Levels For Clients

Jouni Malinen jkmaline at cc.hut.fi
Thu May 22 23:08:54 EDT 2003


On Thu, May 22, 2003 at 02:57:14PM -0500, Michael Shuler wrote:

> I understand what most everything in there is except for "last_rx:
> silence=11 signal=79 rate=110 flow=0"
> What does flow and silence mean?  What are the units of measurement....

Those are raw values from the Prism2 RX descriptor. Unfortunately, the
units of silence and signal fields seem to vary based on firmware
version. I do not know what they are in all the versions, but in the
latest versions they are supposed to be (val-100) dBm. I don't think
flow has been implemented in the firmware, so it is probably always 0.

> signal actually -79 db and silence is really the SNR...which would make the
> nose floor at -90 db?  So does that mean that I have 11db of "clean" signal?
> If that is true than at what speed does the radio run for X amount of
> SNR...i.e. 10db = 11Mbps, 8db = 5.5, etc....any help would be appreciated.

If I remember correctly, there is a knowledge base entry at Intersil's
web site that gave some examples of needed signal ratios for different
rates.

> Also using commercial APs such as Orinoco they will show you the AP's
> receive signal level and the client's signal level...from what I understand
> the info is in the 802.11 frames, is it possible to get a last_tx equivalent
> for last_rx without having to get the value from my client radio?

There is a proprietary data frame that is used to pass some RX signal
values. Prism2 firmware (at least older versions) seem to be handling
these internally, so there is no way of accessing the information in the
host driver.

-- 
Jouni Malinen                                            PGP id EFC895FA



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