Often times, if an indoor BDA (Bi Directional Amplifier)
system’s uplink is not properly optimized, it can create a lot of problem at
the cell site due to uplink noise issues or excess power. BDAs often try to
keep the Uplink (UL) and Downlink (DL) balanced, by keeping same gain in both
directions or by a few dB offset. In this post, I am proposing to keep the BDA
on its ALC (Automatic Level Control) feature and limit the UL ALC to a level which can be
calculated and then adjusted based on real situations. This discussion is for a
CDMA system where power management is an important issue.
Assume that you want your uplink signal to hit the donor
(i.e., Cell Site) BTS at -85 dB. Then for the above diagram, a basic link
budget becomes,
ALCUL – Indoor side cable & other losses + Donor Antenna
Gain – Free Space Path Loss –
Clutter Loss – Fade Margin + Gain in Cell Site Antenna – Cell Site side cable & other losses = -85
Clutter Loss – Fade Margin + Gain in Cell Site Antenna – Cell Site side cable & other losses = -85
