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!
From: Paco G. email@example.com
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
…/benchma-m dqpsk -f 1.25G -m dqpsk --tx-amplitude=500 -r 1M -M
…/benchmark_rx.py -r 1M -m dqpsk --log --costas-alpha=0.05 -S 4
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
get a much better constellation than this one (
I am using the latest gnuradio trunk and the
I have disabled all the data loggins but the rx_receiver.dat from the
the computational requirements.
I tried the 0.5M as eric suggested but the results are even worse (
The 2M rate constellation is the same as 1M.
If I go with BPSK, I get this:
…/benchmark_tx.py -m dbpsk -f 1.25G -m dbpsk --tx-amplitude=500 -r 200k
…/benchmark_rx.py -m dbpsk --verbose -S 4 -r 200k --excess-bw=0.35 -f
–rx-gain=30 > debug
The image below shows the costas loop error:
( http://img156.imageshack.us/img156/1521/screenshot11.png )
(zoom frequency >
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
The M&M block influences a lot, if I change the samples per symbol to 2
get this: ( http://img201.imageshack.us/img201/9436/screenshot14.png )
I have also tried via air interface getting similar results. My question
whether this is normal for the mpsk gnuradio block receiver
or I am doing something wrong.
What are your thoughts about this?
Thank you for your time.
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