User's Manual

Menus and Parameters
Manual Revision 1.0
4-41
Power Control Parameters
The Automatic Transmit Power Control (ATPC) algorithm simplifies the
installation process and ensures optimal performance while minimizing
interference to other units. This is achieved by automatically adjusting
the power level transmitted by the RB according to the actual level at
which it is received by the BU. To support proper operation of the
system with optimal performance and minimum interference between
neighboring systems, the ATPC algorithm should be enabled in all
units.
The algorithm is controlled by the BU that calculates for each received
frame the average SNR at which it receives transmissions from the RB.
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 SNR is determined by a configurable
parameter. In addition, the higher the time that has passed since the
last calculation, the lower the impact of history on the calculated
average. If the average SNR is not in the configured target range, the BU
transmits to the RB a power-up or a power-down message. The target is
that the RB will be received at an optimal level, or as high (or low) as
possible if the optimal range cannot be reached because of specific link
conditions.
Each time that the RB tries to associate with the BU (following either a
reset or loss of synchronization), it will initiate transmissions using its'
Transmit Power parameters. If after a certain time the RB does not
succeed to synchronize with the BU, it will start increasing the transmit
power level.
In a BU typically the maximum supported transmit power is used to
enable maximum coverage. However, there may be a need to decrease
the transmitted power level in order to support relatively small cells and
to minimize the interference with the operation of neighboring cells.
Different power levels may be used for different modulation levels to
optimize performance taking into account the different modulation
schemes as well as possible regulatory restrictions.
Transmit Power in BU
The Transmit Power parameters define the transmit power level of the
BU. These parameters are not part of the ATPC algorithm.
Transmit Power for Modulation Levels 1 to 5
Valid range: -10 to 21 (dBm), using a 1dBm resolution.