Retry

In wired communication, many problems can start from the assumption that the link is mostly stable. Wireless cannot. There is no private wire between two devices. The signal travels through air, walls, people, metal, other devices, and a changing field environment.

Wireless protocols must start with three facts:

• Airtime is shared
• Channel quality changes
• Successful transmission needs acknowledgement or tolerance

That is why Wi-Fi, BLE, Zigbee, Thread, and NB-IoT look different but all involve channels, interference, backoff, hopping, acknowledgement, retransmission, or redundancy.