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From: | Kyeong Su Shin |
Subject: | Re: How to add fec in GMSK |
Date: | Wed, 29 Apr 2020 13:06:25 +0000 |
Hello Quenten:
Hamming code is just an example, I am not suggesting you to implement it. What I want to say is that, the decoder usually needs to know where the code block starts and where it ends in order to correctly decode it, just like in case of the Hamming code. That
is why you need to use packets or frames in this situation. You need to align your data for the decoder before putting it in.
Since the whole point of using frames or packets (in this case) is to align your data for the FEC decoder, you want to make sure that each frame (or packet) contains nicely aligned encoded code blocks. If it doesn't, then it is pretty much useless. If the frame
generator or packet generator requires zero paddings in order to achieve this, then you do the zero padding (you can strip the paddings before pusing the data to the decoder). Also, this generally means that you will want to fix the payload size of your packets
or frames to some integer multiple of the code length (clearly, this is not about the UDP payload size).
Also, zero paddings are often necessary for convolutional codes, which you are using. I do not remember the exact math behind this, so you will have to rely on a textbook (or maybe someone else's reply). GNU Radio's cc_encoder will help you with this, but
I do not remember if it is sufficient. See:
https://www.gnuradio.org/doc/doxygen/classgr_1_1fec_1_1code_1_1cc__encoder.html .
For packetized data, you can refer to example codes at
https://github.com/gnuradio/gnuradio/tree/maint-3.7/gr-digital/examples/packet . You can also write your own GNU Radio blocks, as suggested in
https://wiki.gnuradio.org/index.php/Tutorials . Writing blocks can be a bit difficult on a Windows system, however (works better on Linux). In that way, pretty much anything is possible
(You can still write Embedded Python Blocks on Windows without much hassle).
Regards,
Kyeong Su Shin
보낸 사람: Quenten . <address@hidden>
보낸 날짜: 2020년 4월 29일 수요일 오후 9:15 받는 사람: Kyeong Su Shin <address@hidden> 참조: address@hidden <address@hidden> 제목: Re: How to add fec in GMSK Hello,
Yes I know what hamming code is(I have had the theory but also only the theory, no real life experience).
But I don't know any way how to add it in GNU radio (A lot of examples on the internet used a LP, and yeah i know not everything on the internet can be trusted).
What I am doing here with this 'test' flowgraph is to try to solve the problem the I had in this post: https://lists.gnu.org/archive/html/discuss-gnuradio/2020-04/msg00148.html.
I also tested just the source and sink with the packet en-/decoder but there wasn't even a output signal (so I will not use these anymore unless suggested otherwise).
And you tals about :add paddings and tails on your packets and fix the paylod size to a certain number to get things working. Why Where and how do you do it.
Ps if you are talking about the
payloadsize of the UDP I have already adjusted these so they work without the '(de)modulation techniques'(UDP source to sink).
Someone advised me that this could be possibly solved with using FEC
Op wo 29 apr. 2020 om 10:44 schreef Kyeong Su Shin <address@hidden>:
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