In Section 3.10 of the Sigfox radio spec, we have a convolutional coding with three possible polynominals. Is this really error correcting code (ECC) like in Downlink? It is strange because the output length and the input length are identical (Figure 3-6).

If this is ECC, could anyone tell me what is the code rate? Thanks.

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**Answer** by mfalkvidd
·
Aug 13 at 11:53 AM

For N=3, the message is sent three times. First with R=1 which doesn't modify the message. Second with R=1+X+X2 and third with R=1+X2. The three messages together form the ECC, with an output length of 3x the message length.

It is kind of there, exactly in the 3.10 section you referred to:

But I guess it is a bit hard to interpret unless you already know the answer :-)

3-10.png
(59.7 kB)

I guess we could say the paragraph at the end of 3.13.1 can be the hint for the ECC.

"single or multiple frame(s) carry the same UL-CONTAINER and the same UL-CRC ; **only convolution code and FT value** are different."

However, the ways they use the word "convolution code" and also the mapping of UL-CONTAINER to the three frames in Figure 3-7 are very misleading.

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