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
>
address@hidden> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio>
>
> _______________________________________________
> Discuss-gnuradio mailing list
>
address@hidden>
http://lists.gnu.org/mailman/listinfo/discuss-gnuradio>
>
--
Best wishes,
Yufeng