QAM soft symbol to hard symbol/bit conversion


#1

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?


#2

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


#3

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 B. 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