Frequency Agility & Channel hoping

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Frequency Agility & Channel hoping

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AlanCollins
Contributor V

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.
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billpoole
Contributor III

For a license free sub-GHZ product in the 902-928 MHz ISM band operating in the US or Canada, FCC part 15.249 allows the equivalent of less than 1 milliwatt, about -1 dBm output power, but does not require frequency hopping. Part 15.247 allows power as high as 1 Watt, +30 dBm, if frequency hopping spread spectrum is employed. Typically hopping over 50 or more channels (each accomodating a signal 250 KHz or less wide) and dwelling less than 400ms on any given channel in any 20 second period.

The range enhancement of using a thousand times as much power can often justify the added software complexity needed to implement the freqeuncy hopping algorithm and control.

Freescale's MKW01Z128 can be operated under either part 15.247 or 15.249 with the proper software implementation and off-chip power amplifier.

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dougshade
NXP Employee
NXP Employee

(test ignore)

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