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Re: [Discuss-gnuradio] BER Example - With QT Gui Chooser for Different M

From: Luis Felipe Albarracin Sanchez
Subject: Re: [Discuss-gnuradio] BER Example - With QT Gui Chooser for Different Modulations Issue
Date: Mon, 28 Jan 2019 11:49:47 -0500

Hello Cinaed,

Thank you for the response,

I have detailed your Flowgraph, and I placed a "QT GUI Constellation Sink" after the chunks to symbols block, and what I found is that the modulation part only modulates in B-PSK, and this is beacuse you set it  in the "Chunks to symbol block" with a dimension of "1", once I placed different "Symbol Table" and a "dimension" of 2 in the "Chunk to symbol block" the correct modulation appeared, but the BER gave really high values (even if in the "Constellation Decoder" is set to  QPSK or DQPSK).

I believe you only modulated in BPSK and in the decoder it matched the constellation points for -1 and 1, but not for any other constellation points, I would appreciate if you correct me if i am wrong.

Kind regards.

On Mon, Jan 28, 2019 at 5:12 AM Cinaed Simson <address@hidden> wrote:
On 1/27/19 7:03 PM, Luis Felipe Albarracin Sanchez wrote:
> Hello Cinaed,
> Thank you so much for all the work in the BER, i tested both of the
> flowgraphs and they are very accurate regarding the BER measurements, i
> have a couple of questions if you don´t mind:
> 1- In the latest flowgraph you sent (my-ber-test.grc from Jan 25th) how
> do you change the modulations in the chunks to symbols block, in the
> flowgraph you sent me the flowgraph table was fixed with the values of
> "-1, 1", what line of commands should be place there to switch to other
> modulations?

Correct - I already explain why.
> 2- The BER measurements you sent me seem so accurate,

As I already indicated, you still need to add a complex gaussian noise

 I wonder if you
> could take a look at the flowgraph i sent you

No, use the last flowgraph I sent you.

> (my_ber_simulation_LFA.grc), what i did there was connecting a QT GUI
> Chooser to the functions i thougth would change the constellation
> selected,  do you have any ideas why  my change is not working, when i
> change in the QT GUI Chooser?, i would appreciate your help regarding this.
> 3- Attached is a flowgraph i have devloped for doing modulations up to
> 64 QAM, please take a look at it, and if you have any ideas on how i
> would make a good BER measurement of higher modulations (32 -QAM and
> 64-QAM) please let me know. To select the modulatios, the easiest way is
> to define in the default value of the QT GUI chooser the value of 3 (for
> 32-QAM) and the value of 4 (for 64 QAM).

I not going to look your flowgraph - you should be able to add the QAM
constellations to the last flowgraph I sent you.

And to be clear, I don't believe can change the modulation of the
flowgraph with QT. Since you're the believer, the burden of proof is on

You need to first demonstrate you can add the 64QAM, and 32QAM to the
last flowgraph I sent you with DER 0.

Then add whatever QT modifications you need to make QT change the
modulation and demonstrate the BER is 0.

Or just demonstrate you can add QT code which changes the modulation to
last flowgraph I set you. If can't make the changes so it has BER of 0,
adding different of more modulations isn't going to help.

-- Cinaed

> Once again thanks a lot for all the help.
> Kind regards.
> On Fri, Jan 25, 2019 at 3:20 PM Cinaed Simson <address@hidden
> <mailto:address@hidden>> wrote:
>     It bothered me that the random source wasn't working.
>     So I took at it again last night and discovered I needed to unpack a bit
>     from the random source stream.
>     Using the random source, the following work:
>       BPSK
>       QPSK
>       8PSK
>       16QAM
>     using the pull down menu.
>     There is, however, one caveat: for 8PSK you have to enable the complex
>     Multiply Const by -1 block after the Chunks to Symbols block.
>     Alternatively, you could change Chunks to Symbols from -1,1 to 1,-1 -
>     but that's many more key strokes then just enabling and disabling the
>     Multiply Const block.
>     They all work with the GLFSR source too and with the same caveat.
>     And you were right you don't need the PSK symbol table - you can use
>     Chunks to Symbols -1,1 (except for 8PKS.)
>     Also, I had to add a unpack k=1 block after the decoder - otherwise for
>     DPSK, 8PSK and 16QAM there was a vertical offset and BER sky rockets.
>     The unpack k=1 is not needed for BPSK and QPSK - but it doesn't create
>     any problems so I left it enabled.
>     You just need to add the complex noise source
>     Have fun with QT.
>     Actually, there is already a QT menu - the properties of Constellation
>     Object. You might want to look at the source - just figure what you need
>     to do to keep it open.
>     -- Cinaed
> --
> Eng. Luis Felipe Albarracin
> Msc. Telematics / MBA
> ITIL v3 Foundation
> "Die Grenzen meiner Sprache bedeuten die Grenzen meiner Welt"

Eng. Luis Felipe Albarracin
Msc. Telematics / MBA
ITIL v3 Foundation
"Die Grenzen meiner Sprache bedeuten die Grenzen meiner Welt"

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