This is the question about Sigfox radio specification.

The stack: enter image description here

Specifically, in Section 3.10 of the specification, we have a convolutional coding (after CRC) with three possible polynominals.

I am wonder whether really error correcting code (ECC) because the output and the input lengths are identical (Figure 3-6 in the specification, or see below).

enter image description here

The question is that if this is ECC, could anyone tell me what is the code rate? And if this is not ECC, what is its role?

  • $\begingroup$ Consider the possibility that there is a typo in the figure. They are apparently using a $(3,1)$ systematic convolutional code with generator matrix $[1,1+x+x^2, 1+x^2]$ and so the coded UL-PHY-CONTENT should read "$240$ to $528$" or "$240$ to $536$" bits if the trailing tail of 6 bits (caused by the emptying of the code buffer) is included. $\endgroup$ – Dilip Sarwate Aug 13 '19 at 19:30
  • $\begingroup$ @DilipSarwate yes it should. In fact I got the answer. The output should be 240 to 528 bits, but they are divided into three frames (three UL-PHY-CONTENT). That's where the ECC are implemented and this is an classic convolutional code. The specification is not clear at all. $\endgroup$ – Rokai Aug 14 '19 at 11:50

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