[Discuss-gnuradio] Re: QAM soft symbol to hard symbol/bit conversion

[Silpan gmail]

Hi

Thank you for your help.

I am now using this function to decode the data.  I have another 
question you may be able to answer.  I am trying to implement the BDTI 
OFDM benchmark in gnu radio.  A block diagram can be seen on this 
website.

http://www.bdti.com/products/services_comm_benchmark.html

Do you know if something like this is already in the GNU radio code?

Also, another question regarding data types.  I have the output of the 
constellation decoder connected to a gr.char_to_float block.  The output 
of this is then input to gr.decode_ccsds_27_fb.

So it goes
 gr.constellation_decoder_cb->gr.char_to_float->gr.decode_ccsds_27_fb

I havent seen anything on the input/output definition of the ccsds code, 
so I am suspicious of this arrangement.

If you have N possible complex symbols, where N is typically 2^1, 2^2, 
2^3, 2^4, etc,
I am assuming the output of constellation_decoder is log2(N) chars 
(gnuradio bits) per complex input symbol.  Then char_to_float takes each 
char and converts it to its floating point representation, which is then 
valid input to the ccsds decoder.

Does this all sound right?


Eric Blossom wrote:
> On Thu, Jan 08, 2009 at 05:56:45PM +0100, Silpan Patel wrote:
>> Hi everyone
>> 
>> 
>> I have searched around for this information, but am having a tough time
>> finding it.  I am trying to do 64QAM soft symbol to bit conversion in
>> gnu radio.  It would be something similar to gr.binary_slicer_fb, but
>> work on complex data and output binary data.
>> 
>> Is there anything like this in gnu radio?
> 
> Have you looked at gr.constellation_decoder_cb?
> It's not fast, but could be made fast.
> 
> Eric

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