The protocol stack is similar to other stacks following the OSI model. There are three levels, detailed here:
- PHY Layer: Synthesizes and modules signals using DBPSK in the uplink direction and GFSK in the downlink direction as previously detailed.
- MAC Layer: Adds fields for device identification/authentication (HMAC) and error correcting code (CRC). The Sigfox MAC does not provide any signaling. This implies that devices are not synchronized with the network.
- Frame Layer: Generates the radio frame from application data. Also, it systematically attaches a sequence number to the frame:
Sigfox Protocol Stack versus simplified ...