Re: aironet signal/noise stats

Doug Ambrisko wrote:
> Marco Molteni writes:
> | On Tue, 15 Oct 2002, "Douglas S. J. De Couto" <[email protected]> wrote:
> | 
> | > Does anyone know what the units are for the an driver's noise level
> | > information?  Is it, for example, a dBm value that can be compared to
> | > the signal value to get a signal-to-noise ratio?
> | 
> | does this work for you?
> | 
> | +       u_int8_t                an_noise_prev_sec_pc;   /* 0x7A */
> | +       u_int8_t                an_noise_prev_sec_db;   /* 0x7B */
> | +       u_int8_t                an_avg_noise_prev_min_pc;       /* 0x7C */
> | +       u_int8_t                an_avg_noise_prev_min_db;       /* 0x7D */
> | +       u_int8_t                an_max_noise_prev_min_pc;       /* 0x7E */
> | +       u_int8_t                an_max_noise_prev_min_db;       /* 0x7F */
> 
> Thanks for decoded these.  I think now I got all my units figured out 
> for the in kernel cache and the summary.  They finally make sense
> and agree.  Now I just have to clean it up and I should be able to commit 
> my latest changes.
> 
> Doug A.


Thanks Marco, I think this does work for me.  Do you have documentation 
about these values, or are you making an educated guess?  I have an old 
(pre-cisco) aironet programming manual that doesn't mention any of these 
values.

I guess I have to ask the question, what are the *_pc values in relation 
to?  i.e. percentage of what?  Similar question for the *_db values... 
or are they really dBm (dB relative to 1mW)???

on a related note, you might also be able to make guesses about the link 
by looking at what speed the sender chose to send the packet at.  i.e. 
look in the an_rx_rate field of an_rxframe header.  Of course, this 
assumes the sender is doing something smart when it chosses transmission 
rates, like use slower rates from links with worse SNR.

d

-- 
Douglas S. J. De Couto    [email protected]



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