Motorola Micom 2 Manual

							MICOM-2E-ALE Owner’s Manual
42
Keyboard Beep (KBBP)
This menu toggles between enabling and disabling the beep for the
keyboard (keypad).
Press
[YES] to enable the keypad
beep.
Press
[NO] to disable the keypad beep.
Press
to confirm,to cancel.
Tone
This menu sets the keyboard beep tone to high or low volume.
Press
[YES] to set to low volume.
Press
[NO] to set to high volume.
Press
to confirm,to cancel. 
						

							Programming the Radio
43
Alternate Display Time-out (ADT)
This menu sets the time-out time of the menu display. You define the
number of seconds that elapse before the display returns to the
previous screen.
To set the time-out time:
1.Enter the Radio Programming menu (steps 1-4 on
page 29).
2.Press[PRMT].
3.Pressto scroll to the ADT option.
4.Press[ADT].
5.Press
Press
Press
Press[] to increment the displayed value by 1.
[1], to quick-set the value to 1.
[10], to quick-set the value to 10.
6.Press
 to confirm,to cancel. 
						

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Setting Radio Options
MICOM-2E offers three programmable radio options:
· Tuner (TUNE)
· Accessory (ACC)
· ALE
To set the radio option:
1.Enter the Radio Programming menu (steps 1-4 on
page 29).
2.Press[OPTS].
3.Press the function key beneath the option of your choice:
TUNE - toggles the tuner.
ACC - sets the accessory setting.
ALE - toggles ALE option on/off.
4.Press to confirm,to cancel. 
						

							45
Automatic Link Establishment (ALE)
The MICOM-2E unit incorporates Automatic Link Establishment (ALE) to
select the best working channel from the channels programmed into the
unit automatically without user intervention. The ALE incorporates all
advanced data transmission techniques required by MIL-STD-188/141A
and FED-STD-1045. The ALE feature thus ensures the user of the best
possible link without requiring prior knowledge of radio communications.
Previously, HF radio operations had to be familiar with the constantly
varying nature of the ionosphere, the atmospheric layer that reflects HF
radio waves back to earth. A knowledge of the ionizing effects of
sunspots, the seasons, time of day, and fluctuations in the earth’s
magnetic field was essential for the operator to find the best frequency
for any particular link.
Manufacturers of HF-SSB equipment tried numerous methods to assist
the operator in this difficult task. For example, various squelch circuits
are employed to overcome operator fatigue from interference noise.
Another aid is the use of several receivers so that the operator does not
have to search continuously for incoming calls. More advanced are
scanning receivers combining selective calling.
A more recent approach has been adopted to combine scanning with a
“handshake” to establish a link. However, because the first link is not
always the best, some manufacturers use Link Quality Analysis (LQA),
which measures a few propagation parameters, such as the bit error
rate (BER) and S/N. If the result is below a desired threshold, the
search continues until a reasonable link is found. Here again, there is no
guarantee that a better channel was not overlooked. Motorola’s ALE, a
technological breakthrough in HF-SSB communication, combines
scanning, selective calling, sounding, channel selection, and LQA.
These features, all automatic, ensure that even with an unskilled
operator, communication takes place on the channel with the best link
quality. 
						

							MICOM-2E-ALE Owner’s Manual
46
Activating/Deactivating the ALE
The MICOM-2E implements Automatic Link Establishment (ALE) that
selects the best working channel from the available channels that are
programmed for use. Using ALE is highly recommended for users
because it ensures the best link possible without an in-depth knowledge
of radio communications. Pages 45-51 describe the ALE features in
greater detail.
To disable ALE:
1.Pressto obtain the Menu display.
2.Press
option.
to obtain the menu with the PROG
3.Press[PROG].
4.Press[RAD].
5.
Press , [OPTS] to enter Radio Programming
mode.
6.Press[ALE].
7.Press[NO] to disable ALE.
8.Press to confirm. 
						

							Automatic Link Establishment (ALE)
47
To enable ALE (after disabling):
1.Pressto obtain the Menu display.
2.Press
option.to obtain the menu with the PROG
3.Press[PROG].
4.Press
[RAD].
5.
Press  [OPTS] to enter Radio Programming
mode.
6.Press[ALE].
7.Press[YES] to enable ALE.
8.Press to confirm. 
						

							MICOM-2E-ALE Owner’s Manual
48
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.
NOTE
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. 
						

							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% 
						

							MICOM-2E-ALE Owner’s Manual
50
occupancy. A 60-minute cycle would result in 40% occupancy. A 90-
minute cycle would result in 27% occupancy. A 120-minute cycle would
result in 20% occupancy.
It can now be decided which sounding cycle is the best for any
particular network, taking into account the trade-offs described above.
Under field conditions, the occupancy will usually be less than the value
obtained from the chart because not every station receives all the
soundings that are being broadcast on all channels. However, if the
system manager wants to increase channel-free time for the users by
reducing network occupancy, it is possible to do so through four
methods, listed below in their order of preference:
1.  Increasing the sounding cycle time (to 90 or 120 minutes).
2.  Reducing the number of channels in the network (for example, by
using different nets for different times of day).
3.  Reducing the number of stations in the network by re-arranging the
hierarchial subgrouping of stations.
4.  Requesting all stations to set the fast scan rate option.
Immediate (Manual) Sounding
If it is required to perform a rapid sounding cycle on all channels instead
of, or in addition to, the automatic sounding cycle, the Immediate
Sounding procedure can be used.
Optional Handshake/Call Reject
The “optional handshake” is programmable. If selected, each time a
sounding transmission is completed, the radio will listen for two
seconds. If a call is received on the same channel, the radio will
respond and establish a link. 
						

							Automatic Link Establishment (ALE)
51
Bi-directional Handshake
The bi-directional handshake is a shorcut procedure to exchange LQA
scores with other stations in the system without establishing a link. This
procedure is useful in the following cases:
· The radio has only recently been switched on and an automatic
sounding cycle has not been completed yet.
· The operator wishes to update the LQA scores before initiating a call
to another station.
· When a new or passive station joins to the system.
· In case of sudden atmospheric changes, etc.
The bi-directional handshake can be carried out either with a single
station or with all stations in the net; it can be carried out either on a
single channel or on all network channels. An AMD message can also
be added to the procedure.
At the end of the bi-directional procedure with a private station, the LQA
matrix is updated. The operator can then initiate a call and obtain the
best channel automatically. When the bi-directional procedure is
performed with a net, 
all stations in the net update their LQA tables.
ALE Programming
Motorola’s Mobile ALE is highly flexible. Its functions are programmed
from an external computer using the ALE Radio Service Software (RSS)
program. Refer to Motorola publication no. 68P02952C25.