Instruction manual

Menus and Parameters
2-57
BreezeACCESS Version 4.3 System Manual
 If required for compliance with local regulations or other restrictions
related to maximum allowable transmitted power.
In addition to the ability to set the transmit power to a certain fixed
level, BreezeACCESS units support an Automatic Transmit Power
Control (ATPC) algorithm. The ATPC algorithm automatically adjusts
the power level transmitted by each SU according to the actual level at
which it is received by the AU. To support proper operation of the
system with optimal performance and minimum interference between
neighboring sectors, the ATPC algorithm should be enabled in all units.
The algorithm is controlled by the AU that calculates for each received
frame the average RSSI at which it receives transmissions from the
specific SU. The average calculation takes into account the previous
calculated average, thus reducing the effect of short temporary changes
in link conditions. The weight of history (the previous value) in the
formula used for calculating the average RSSI is determined by a
configurable parameter. In addition, the higher the time that has passed
since last calculation, the lower is the impact of history on the
calculated average. If the average RSSI is not in the optimal range
(typically between -74dBm to -64dBm), the AU transmits to the SU a
power-up or a power-down message. The target is that each SU will be
received at an optimal level, or as high as possible if the optimal range
cannot be reached because of specific link conditions.
Each time that the SU tries to associate with the AU (following either a
reset or loss of synchronization), it will initiate transmissions using the
Current Transmit Power Control, which is the last value that was
previously used by the ATPC mechanism. If after a certain configurable
time the SU did not succeed to synchronize with the AU, it will start
transmitting using the level configured for the Transmit Power Control
parameter. (If this is the first time that the SU is powered up, or if the
ATPC algorithm was not used, the Current Transmit Power Control
equals the value of Transmit Power Control).
 Transmit Power Control – Controls the relative gain of the Tx
power circuits.
A value of 7 represents the highest transmit power level, which is
the maximum level supported by the specific unit. A lower value
represents a lower transmit power level. The effect of this parameter
on the transmitted power is not linear, since it is affected by the
length (attenuation) of the IF cable.
In SUs, if the ATPC Option is enabled this parameter serves for
setting the initial value to be used by the ATPC algorithm after the
first time of powering-up the unit. It will also be used in the
following cases:
a. If the unit does not succeed to associate with the AU after reset
b. If the unit does not succeed to re-synchronize with the AU after
losing synchronization