WX GUI Constellation sink plot freez?

Hello list,

I got questions re the WX GUI Constellation Sink block:

1/ Could anyone give descriptions of what is

  • Theta ?
  • Loop bandwidth ?
  • Max Freq ?
  • Mu ?
  • Gain Mu ?
  • Symbol Rate ?
  • Omega Limit ?

2/ What are the essential params of the block to adjust, for my case I
am
receiving a BPSK signal (Params @ Tx are: 10 MHz samp_rate, ow_format
sc8,
Samples/Symbol = 4, Spread signal with a 11 chips code),

I set:
sample_rate = 10 MHz,
Frame rate = 512,
Constellation Size = 512,
M = 2,

3/ Once the constellation plotted it freezes and "O"s appears in the
terminal section of GRC ?
What am I doing wrong ?

Regards,


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On Mon, Nov 25, 2013 at 12:26 PM, Naceur [email protected] wrote:

  • Gain Mu ?
  • Symbol Rate ?
  • Omega Limit ?

This block basically uses the M&M clock recovery block:
http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1clock__recovery__mm__cc.html

And the Costas loop block:
http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1costas__loop__cc.html

That should explain much about those parameters. The Theta value is
the phase rotation of the locked constellation. So you can readjust a
QPSK that sits on the +/-1 +/- 1j points to the x and y axes by
setting theta to pi/4.

2/ What are the essential params of the block to adjust, for my case I am
receiving a BPSK signal (Params @ Tx are: 10 MHz samp_rate, ow_format sc8,
Samples/Symbol = 4, Spread signal with a 11 chips code),

I set:
sample_rate = 10 MHz,
Frame rate = 512,
Constellation Size = 512,
M = 2,

Drop the frame rate. You’re trying to display 512 frames/second, which
is too fast for you to even see and asking your computer to do a lot
of extra work. The default of 5 should be enough.

3/ Once the constellation plotted it freezes and "O"s appears in the
terminal section of GRC ?
What am I doing wrong ?

Regards,

That indicates not enough processing power. You’re now trying to do
too much in the graph for your processor. Can you try a lower symbol
rate signal to start off with? Get the feel for the parameters and
setup and try to understand the performance limitations before jumping
right in to your full signal. But also, just dropping the frame rate
as I suggest above should give you back a lot of processing time.

Tom

Thank you for the reply :slight_smile:


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