Sigfox Header Size

Question

I can't seem to find if the header size for Sigfox. Looking at their website (https://build.sigfox.com/study) it says "The Sigfox uplink payload is limited to 12 bytes (excluding the payload headers). The downlink payload is limited to 8 bytes (excluding the payload headers)." It never mentions anything about the size of these payload headers and I can't seem to find information on it anywhere. Any help would be greatly appreciated.

Answer 1

It's all documented in the Sigfox device radio specifications. For an uplink:

• 19 bits preamble
• 13 bits frame type
• 2 bits length indicator
• 1 bit bidirectional frag
• 1 bit repeated flag
• 12 bits message counter
• 32 bits identifier
• variable length uplink authentication (between 2 and 5 bytes)
• 16 bits CRC

Which gives a total of 112 to 136 bits, 14 to 17 bytes.

Note that I just glanced at the doc, so I may have missed things, there may be more stuff.