Re: [Discuss-gnuradio] Measuring RSSI on USRPN200

[Vanessa Gardellin]

Hi,
I was reading your very interesting discussion and I was wondering if
you can give us some tips on how to compute the RSSI by software and
hence the blocks that we should add.

Tnx

Vanessa

On Sun, Oct 23, 2011 at 3:35 PM, Marcus D. Leech <address@hidden> wrote:
> On 22/10/11 10:56 PM, Bonee Soibam wrote:
>
> Hi Marcus ,
> Sorry i did not explain to you my set-up , i have two usrpn200's with RX2400
> as the daughterboards . i have omnidirectional antennas . Its a line of
> sight experiment .  i used .benchmark_tx.py -f 2475M -m bpsk
> --from-file=test.pdf -S 2 -s 50 --tx-amplitude=0.25 -v
> and on the receiver side i ran ./uhd_fft.py and ./rx_ascii_art_dft.py  .
> the problem i get in uhd_fft.py is that , as i vary  the transmit powers
> from 0.25 to 0.85 , i am getting -20 dB  constant peak at a fixed distance .
> logically it should increase as you said but i am getting constant received
> values .
>
> My suspicion, having not looked at the code, is that the magnitude of the
> signals arriving at the
>   "amp" block in that flow-graph are already sufficiently larger than "1",
> that you're seeing clipping
>   somewhere in the chain.
>
>
>
> Please tell me what to do next . i read on your site that , you can measure
> analog  RSSI measurements using read_aux_adc(side,0) .
> Can you explain a little bit on which file it is referring too . looks like
> the repository has moved too so i am unable to find which app it is
> referring to .
> Eagerly anticipating your reply
> Bonee
>>
>> o
>
> You *could* read the RX-side aux_adc, but it would give you mis-leading
> results, since the power-detector
>   is showing you the power across the entire post-mixer bandwidth.  It
> really, really is better to calculate
>   the RSSI from the incoming data, and since you'd have to modify your
> application anyway to
>   read the aux_adc, you might as well add a couple of blocks to calculate
> received power properly.
>
> Also, not all cards *have* an RSSI detector available in hardware, so
> assuming that they do is
>   non-portable to other types of cards.
>
>
> --
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
> http://www.sbrac.org
>
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>



-- 
Vanessa GARDELLIN, Ph.D.
Researcher
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
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