User's Manual

Menus and Parameters
Operation and Administration
137
In certain units with an integral antenna the Antenna Gain is not available as a
configurable parameter. However, it is available as a read-only parameter in the
applicable “Show” menus.
The range is 0 – 50 (dB). A value of “Don’t Care” means that the actual value is
not important. A value of “Not Set Yet” means that the unit will not transmit until
the actual value (in the range 0 to 50) is configured. The unit can be configured to
“Don’t Care” or “Not Set Yet” only in factory (when upgraded to SW version 2.0
from a lower version it will be set automatically to one of these options). Once a
value is configured, it is not possible to reconfigure the unit to either “Don’t Care”
or “Not Set Yet”.
The default value depends on unit type. In SUs with integral antenna it is set to
21 (read only). The default value for AUs that are supplied with a detached
antenna is in accordance with the antenna’s gain. In units supplied without an
antenna the default is typically “Not Set Yet”.
4.2.6.2.10 Cell Distance Parameters (AU only)
The higher the distance of an SU from the AU that is serving it, the higher the
time it takes for messages sent by one of them to reach the other. To ensure
appropriate services to all SUs regardless of their distance from the AU while
maintaining a high overall performance level, two parameters should be adapted
to the distances of SUs from the serving AU:
 The time that a unit waits for a response message before retransmission (ACK
timeout) should take into account the round trip propagation delay between
the AU and the SU (The one-way propagation delay at 5 GHz is 3.3
microseconds per km/5 microseconds per mile.). The higher the distance from
the AU of the SU served by it, the higher the ACK timeout should be.
The ACK timeout in microseconds is: 20+Distance (km)*2*3.3 or
20+Distance (miles)*2*5.
 To ensure fairness in the contention back-off algorithm between SUs located
at different distances from the AU, the size of the time slot should also take
into account the one-way propagation delay. The size of the time slot of all
units in the cell should be proportional to the distance from the AU of the
farthest SU served by it.
The Cell Distance Mode parameter in the AU defines the method of computing
distances. When set to Manual, the Maximum Cell Distance parameter should be
configured with the estimated distance of the farthest SU served by the AU. When
set to Automatic, the AU uses a special algorithm to estimate its distance from
each of the SUs it serves, determine which SU is located the farthest and use the
estimated distance of the farthest SU as the maximum cell distance. The value of
the maximum cell distance parameter (either computed or configured manually)