Lqa Memory; Automatic Sounding; Sounding Cycle Time - Motorola MICOM-2E ALE Owner's Manual

MICOM-2E-ALE Owner's Manual

LQA Memory

The ALE builds a database of connectivity information based on calls
and digital ALE "sounding" messages transmitted by other stations in
the network. This information is stored in a special "LQA memory" and
used to determine the link quality of all channels in the networks. The
data in LQA memory is "time-weighted", that is, recent information is
given more value than old, thus compensating for changing propagation
conditions.

Automatic Sounding

Automatic sounding is a method for testing the selected channels and
the propagation path under field conditions. The sounding signal is a
very short (beacon-like), unilateral identifying broadcast, carried out in
periodic intervals on unoccupied channels.
Identifying the sounding signal sent from a station indicates a high
probability of bilateral connectivity.
Long or short sounding cycles are mainly determined according to
propagation conditions. In case of slow propagation changes, long
intervals of about 1 or 2 hours may be sufficient. If, however, the
propagation changes are erratic and rapidly changing, or if the
connectivity information is critical, then shorter intervals are
recommended. Each station may also measure BER and S/N, and
update the LQA table accordingly.
The maximum score for receiving an optimum
sounding is 70%; the minimum score is 30%. The
score given to a station that did not send any sounding
or a station whose sounding has not been received is
also 30%.

Sounding Cycle Time

The sounding messages is repeated at regular intervals on all channels
in the network. A complete round of sounding messges, or "sounding
cycle," can be programmed to 30, 60, 90, or 120 minutes when the
automatic sounding is on. The sounding can be initiated manually when
there is a specific need for it, even if the system is set to operate in the
automatic mode.
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