User Manual

Bay Level Offset Calibration

3-78 1X SC4812T–MC BTS Optimization/ATP 5/21/04

DRAFT

Introduction

Bay Level Offset (BLO) calibration is the central activity of the

optimization process. BLO calibration compensates for normal

equipment variations within the BTS RF paths and assures the correct

transmit power is available at the BTS antenna connectors to meet site

performance requirements.

RF Path Bay Level Offset

Calibration

Calibration identifies the accumulated gain in every transmit path (BBX

slot) at the BTS site and stores that value in a BLO database calibration

table in the LMF. The BLOs are subsequently downloaded to each BBX.

For starter frames, each receive path starts at a BTS RX antenna port and

terminates at a backplane BBX slot. Each transmit path starts at a BBX

backplane slot, travels through the Power Amplifier (PA), and terminates

at a BTS TX antenna port.

For expansion frames each receive path starts at the BTS RX port of the

cell site starter frame, travels through the frame-to-frame expansion

cable, and terminates at a backplane BBX slot of the expansion frame.

The transmit path starts at a BBX backplane slot of the expansion frame,

travels though the PA, and terminates at a BTS TX antenna port of the

same expansion frame.

Calibration identifies the accumulated gain in every transmit path (BBX

slot) at the BTS site and stores that value in a BLO database. Each

transmit path starts at a C–CCP shelf backplane BBX slot, travels

through the PA, and ends at a BTS TX antenna port. When the TX path

calibration is performed, the RX path BLO is automatically set to the

default value.

At omni sites, BBX slots 1 and 13 (redundant) are tested. At sector sites,

BBX slots 1 through 12, and 13 (redundant) are tested. Only those slots

(sectors) actually equipped in the current CDF or NEC file are tested,

regardless of physical BBX board installation in the slot.

When to Calibrate BLOs

Calibration of BLOs is required:

S After initial BTS installation

S Once each year

S After replacing any of the following components or associated

interconnecting RF cabling:

– BBX board

– C–CCP shelf

– MCIO card

– MCIO to Power Amplifier backplane RF cable

– Parallel Linear Amplifier Combiner