From: yufeng wang <address@hidden>
To: Bill Stevenson
<address@hidden>
Sent: Friday, April 10, 2009 6:17:49 PM
Subject: Re: [Discuss-gnuradio] QPSK phase noise
Thanks, Bill. I think we may also use the plot codes under the file
gr-utils, where
plot_const.py and
usrp_fft.py can be found. I have
used the usrp_fft.py to display the output signal, and I'm trying to
install scipy to enable the plot_const.py, etc. I also wanna load the
data using Matlab, I wonder how can you output the data to a sink
file? Thanks!
On Fri, Apr 10, 2009 at 4:46 PM, Bill Stevenson
<
address@hidden> wrote:
> Hi,
>
> We can output the data to a sink file, from which we load the data using
> Matlab. Then we use scatterplot.
>
> Thanks!
>
> Bill
>
>
________________________________
> From: yufeng wang <
address@hidden>
> To: Bill Stevenson <
address@hidden>
> Sent: Friday, April 10, 2009 12:22:15 PM
> Subject: Re: [Discuss-gnuradio] QPSK phase noise
>
> Hi, Bill,
>
> Regarding to Paco's images, I wonder which programme did you use to
> display the output of the images that he had got? like the
> constellations?
>
> I'm using
benchmark.py to transmit and receive BPSK signals. I can use
> usrp_fft.py to display the output of the transmitter. Thanks in
> advance!
>
>
>
> On
Fri, Apr 10, 2009 at 12:03 PM, Bill Stevenson
> <
address@hidden> wrote:
>> Hi, Paco
>>
>> Actually, I got the similar result as you did. I think there was something
>> wrong in the mpsk_receiver block. I am checking it. Thanks!
>>
>> Bill
>>
>> ________________________________
>> From: Paco Garcia <
address@hidden>
>> To:
address@hidden>> Sent: Wednesday, April 8, 2009 9:26:36 AM
>> Subject: Re: [Discuss-gnuradio] QPSK phase
noise
>>
>>
>> Johnathan, you were right with the distortion issue at the TX, I am now
>> using
>> these parameters:
>>
>> ./benchma-m dqpsk -f 1.25G -m dqpsk
--tx-amplitude=500 -r 1M -M 99999999
>> --excess-bw=0.35
>> ./benchmark_rx.py -r 1M -m dqpsk --log --costas-alpha=0.05 -S 4 --verbose
>> -r
>> 1M --gain-mu=0.01 --excess-bw=0.35 -f 1.25G --rx-gain=45
>>
>> But still, for a 40dB SNR (
>> http://img149.imageshack.us/img149/4583/screenshot4h.png ) I think we>> should
>> get a much better constellation than this one (
>> http://img149.imageshack.us/img149/7968/screenshot3t.png )>>
>> I am using the latest gnuradio trunk and the
>> ../gnuradio-examples/digital/benchmark....
>> I have disabled all the data loggins but the
rx_receiver.dat from the
>>
/usr/local/lib/python2.5/site-packages/gnuradio/blks2impl/dqpsk.py to
>> reduce
>> the computational requirements.
>>
>> I tried the 0.5M as eric suggested but the results are even worse (
>> http://img18.imageshack.us/img18/2306/screenshot5hhm.png )>>
>> The 2M rate constellation is the same as 1M.
>>
>> If I go with BPSK, I get this:
>> http://img212.imageshack.us/img212/3010/screenshot10.png>> using
>> ./benchmark_tx.py -m dbpsk -f 1.25G -m dbpsk --tx-amplitude=500 -r 200k -M
>> 99999999 --excess-bw=0.35
>> ./benchmark_rx.py -m dbpsk --verbose -S 4 -r 200k --excess-bw=0.35
-f
>>
1.25G
>> --rx-gain=30 >
debug
>>
>> The image below shows the costas loop error:
>> ( http://img156.imageshack.us/img156/1521/screenshot11.png )>> (zoom frequency > http://img514.imageshack.us/img514/2173/screenshot12.png>> )
>> blue: phase
>> red: phase_error
>> cian: Q
>> purple: I
>> green: freq
>>
>> So once the costas locks, there is still some error which is causing the
>> blur constellation. But I think that for an almost 40dB SNR signal (
>> http://img212.imageshack.us/img212/551/screenshot13.png ) we should
get>> much
>> better
results.
>>
>> The M&M block influences a lot, if I change the samples per symbol to 2 I
>> get this: ( http://img201.imageshack.us/img201/9436/screenshot14.png )>>
>> I have also tried via air interface getting similar results. My question
>> is
>> whether this is normal for the mpsk gnuradio block receiver implementation
>> or I am doing something wrong.
>>
>> What are your thoughts about this?
>>
>> Thank you for your time.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> View this message in context:
>> http://www.nabble.com/QPSK-phase-noise-tp22934944p22950446.html>> Sent from the GnuRadio mailing list archive at
Nabble.com.
>>
>>
>>
>> _______________________________________________
>> Discuss-gnuradio mailing list
>>
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>>
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>>
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http://lists.gnu.org/mailman/listinfo/discuss-gnuradio>>
>>
>
>
>
> --
> Best wishes,
>
> Yufeng
>
>
--
Best wishes,
Yufeng