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J-Series Data Radio – User Manual
Part D – Features
Hopping Intervals
Frequency Hopping Spread Spectrum (FHSS) radios like the
J-Series operate in an unlicensed shared frequency band and
collisions can be expected when multiple radios are operating in
the same area.
Due to the hopping nature of the radio, the radio “hops” between
a specific number of distinct frequencies in a specific pattern. The
length of time that the radio remains on any one frequency is called
the “Hopping Interval”. Data is transferred between radios during
this time.
Once the hopping interval has expired, the transmitter (if active) is
stopped, and all radios in the system “hop” to the next frequency in
the hopping pattern. Whilst the radios are hopping, no data can be
transferred between radios.
When two radios in the same area are transmitting on the same
unique frequency, a data collisions may occur and this will prevent
successful data transfer until one or both radios “hop” onto another
frequency.
Shorter hop intervals will reduce the amount of time that any such
collisions may impact on the radio link and as such will make the
radio link less susceptible to interference. However, the usable
bandwidth of the radio will be reduced because the ratio of time
spent hopping to a new frequency vs time spent transmitting data
is higher.
Longer hop intervals will increase the amount of time that any such
collisions may impact on the radio link and as such will make the
radio link more susceptible to interference. However, the usable
bandwidth of the radio will be increased because the ratio of time
spent hopping to a new frequency vs time spent transmitting data
is lower.
The radio will default to a Hopping Interval of 100mS. For
most systems, this setting provides a good balance between
susceptibility to interference vs usable bandwidth.