Installation Manual Part 3

PRELIMINARY
7-37
BWX 8415 Basestation Installation and Commissioning Guide
OL-19519-01
Chapter 7 Commissioning
7.7 Calibration
7.7 Calibration
7.7.1 What it Means to Calibrate
Performing a calibration on the BS detects the phase differential between the antenna elements and
matches the output power across all antenna elements in the BWX 8415 Antenna Unit. On a new
installation, the calibration procedure should be performed at least 3 times to verify consistency of the
returned values. Ensure that the BS has been powered on, with the Power Amplifiers on, for at least 15
minutes to allow them to warm up and stabilize.
Caution Do not attempt to calibrate the basestation while performing a software upgrade or downgrade.
Calibrating during an upgrade or downgrade can interfere with the loading of files into system
components and may produce faults or other problems.
7.7.2 Types of Calibration
Assuming the BS has been powered up and left on for at least 15 minutes, and that all alarms have been
cleared, you can now run a calibration. There are 2 types of calibration:
• Full Calibration
• Online Calibration
Typically, only the Full Calibration is done manually by the service provider. For the initial installation,
the Full Calibration will be run at least 3 times.
Note Cisco recommends that a Full Calibration be performed on each BS, at least once every 4 weeks.
When a Full Calibration is invoked, the BS is out of service for about 2 minutes. After installation,
commissioning, and acceptance testing, Cisco recommends that a Full Calibration be run every 4 weeks
during off hours. During Full Calibration the Digital card pre-calibrates itself and the BS closes any
ongoing sessions with modems that are currently registered. The transmit gain in the IF section is
adjusted for each of the 8 transmit paths individually so that the level of power delivered at the base of
each antenna element is exactly the value specified by the Antenna Power parameter.
The receive gain is adjusted for each of the 8 receive paths individually so that when the level of power
specified by the Rx Sensitivity parameter is received at the base of each antenna element, it will
correspond to the maximum voltage that the card can handle. If the card is unable to adjust either the TX
gain or the RX gain for a particular antenna element, both gain values are set to zero (0) and this antenna
element is taken out of service.
Then, all paths are turned on using the gain settings just determined by the calibration, and the phase and
amplitude changes introduced in each sub-carrier between the BS and the base of each antenna path are
determined, both in the transmit and receive directions. This is done with power applied to all antenna
paths and using the TX and RX gains in the card, as determined in the previous step, in order to achieve
the power levels specified by the Antenna Power and Rx Sensitivity parameters.
Once the new phase change values are determined, they are compared with previous results kept in the
BS’s memory. If there is a large discrepancy with the previous results, an alarm is generated and the BS
uses the most likely correct set of values. Otherwise, the new results are sent to the EMS and kept in the
BS’s memory for future comparisons.