Freq agility and channel hoping concepts are used in two different contexts.
- Freq. agility is often related to NWK layer changing operation channels after a rather long period of time (5 seconds or so). This is like the RF4CE or ZigBee channel agility. RF4CE performs Energy detection every 5 seconds to see if there is a better channel to switch. ZigBee on the other hand, triggers changing channel requested by specific conflicts in the network, or if the user decides to change channels.
- Channel hoping is mostly related to Link Layer where the MASTER of connection decide with anticipation which channels they will use for sharing data. Then you can’t stay longer than 100ms sending data in the same frequency. This is a more complex mechanism. This is mandatory for certifications in Sub-GHz frequencies or communication protocols like Bluetooth.