Re: [Discuss-gnuradio] use of CCSDS 27 encoder-decoder blocks

[Tom Rondeau]

On Tue, Jan 12, 2016 at 6:47 AM, Hitesh Kasera <address@hidden> wrote:

hello tom,

i tried to put a block of packing bits after FEC decoder block but still received data is not same as transmitted. here i am working in simulation environment not on air so i think there will not be any delay problems.

Hitesh 

Delays are also caused by filters. This isn't an issue in your case, but just so you know.

As for your current issues, it'll be hard to help you without running your program directly. However, we have a lot of debugging tools, and using the QT GUI blocks to plot the signals and try and observe what's happening is a useful way of debugging on your own.

Also, look at $prefix/share/gnuradio/examples/fec. There are a lot of examples for using the FEC blocks here.

Tom

 

On Mon, Jan 11, 2016 at 10:54 PM, Tom Rondeau <address@hidden> wrote:

On Fri, Jan 8, 2016 at 12:44 PM, Hitesh Kasera <address@hidden> wrote:

thanks tom for your reply. as you told me to use fec api blocks i tried to use fec encoder and decoder blocks but still my output is not same as input. may be i am missing something while i am using these blocks. i have attached the image and .grc file of my flowgraph.

Hitesh

You probably need to pack your bits after the FEC decoder block. There might also be some offsets that'll you'll need to deal with, though probably not in this case. If you add anything with a filter (like a modulator/demodulator), there will be a group delay you'll need to deal with and figure out where the start of your actual information bits is.

Tom

 

On Mon, Jan 4, 2016 at 8:30 PM, Tom Rondeau <address@hidden> wrote:

On Fri, Jan 1, 2016 at 3:17 AM, Hitesh Kasera <address@hidden> wrote:

Hi everyone,

I am trying to use ccsds 27 encoder-decoder to transmit some data. The decoded data is not same as transmitted. As a source i am transmitting ones and zeros but after decoding sometimes i am receiving values which are greater than 1.  i am not able to recognize where am i going wrong. if anyone has any idea please tell me. i have attached both grc file and png image of my flow graph.

Best Regards,

Hitesh

Changing the problem a bit, I'd recommend moving away from the CCSDS encoder/decoder blocks and using the FEC API blocks, instead. See:

http://gnuradio.org/doc/doxygen/page_fec.html

The CC Encoder and CC Decoder are basically the CCSDS codes (you might have to swap the two polynomials; I always forget off the top of my head which is called which code here).

Tom