Automatic Link Establishment (ALE)
49
To select the best sounding cycle time, the trade-offs must be
considered. On the one hand, a shorter cycle ensures a more updated
LQA memory; thus the channel with the highest LQA value will, in fact,
have the best link quality at that point in time. On the other hand, a
shorter sounding cycle increases network occupancy due to more
frequent sounding messages, leaving less channel-free time for the
users.
Figure 1 shows network occupancy in relation to sounding cycles of 30,
60, 90, and 120 minutes. (Note that both axes have logarithmic scales.)
The chart also shows 80% and 95% occupancy in a 120-minute
sounding cycle at a very rapid scanning rate (applicable only to multiple-
channel networks).
Figure 1: Network Occupancy
It is clear from the chart that if there are two or three channels in the
network, a sounding cycle of 30 minutes allows enough channel-free
time, even for as many as ten users. The best way of using this chart is
given in the following example: in a network of nine channels used by
eight members, a 30-minute sounding cycle would result in 80%
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