Re: [Discuss-gnuradio] Constallation receiver block in gnuradio companion

[Ben Reynwar]

On Thu, Jun 14, 2012 at 4:53 PM, Nazmul Islam
<address@hidden> wrote:
> Hello,
>
> I want to transmit a continuous stream of data and obtain its synchronized
> version (before decoding) at the receiver using gnuradio companion.
> Following the generic_mod_demod.py, I have designed the transmit and receive
> path in the following way
>
> Tx:    GLFSR source (producing +1 & -1) --> RRC filter --> USRP Sink
>
> Rx: USRP Source --> AGC2 --> FLL Band Edge --> Polyphase Clock Sync.
>
> I want to insert the Constellation Receiver block at the end of the
> Polyphase Clock Sync. I have two questions on this:
>
> 1. The Constellation Receiver block asks for "constellation object" and it
> accepts raw data type. What should I put here? I tried using the options 2
> and bpsk but they did not work.

digital.constellation_bpsk()

>
> 2. The Constellation_Receiver_cb accepts baseband complex streams and
> returns byte level data. Will it output the decoded data? I want the complex
> data, that has gone through the costas and M&M recovery block, but has not
> been decoded yet. How can I obtain that?

constellation_receiver_cb only does some fine tuning of the phase, and
then the mapping to symbols.  If you want to get the fine tuning
without the mapping then you'll need to edit
gr-digital/lib/gr_constellation_receiver_cb.cc.  Currently the block
can have 1 or 4 outputs.  If one it just outputs the symbols.  If four
it outputs symbol, phase error, phase estimate, and frequency
estimate.  You could edit the block so that it also outputs the fined
tuned complex data.

>
> Any suggestion will be appreciated.
>
> Thanks,
>
> Nazmul
>
>
> --
> Muhammad Nazmul Islam
>
> Graduate Student
> Electrical & Computer Engineering
> Wireless Information & Networking Laboratory
> Rutgers, USA.
>
>
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