DAS Flower: an interesting way to understand DAS platform

If you are new to DAS, here is an easy way to understand DAS platforms by solving a very simple puzzle. Based on 3 simple rules below you will have to figure out what will be the connection type in picture 1 between the blue ball (Antenna) and the square box (media converter)?

3 simple rules:

1. RF travels on coaxial cable. Antenna can only receive RF signal.
2. Loss of signal is high in a coaxial cable (signal loss is 50% every 100 ft for a typical ½” cable)
3. Signal loss in fiber is minimal even on a long run (such as over 1000 ft) 

Controlling Uplink ALC for a BDA

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

Info-graphics: service affecting components in a DAS

Impact of service diminishes as you move downstream from head-end on a DAS. Need for redundancy, therefore, increases in the opposite direction.

System Map: how can it reduce troubleshooting time?

Close-out package has a lot of benefits. But it should be built around one principal premise:
How much time can it cut down during troubleshooting?

Finding out the source of the problem is a big deal during DAS troubleshooting - especially if you have a short Service Level Agreement (SLA) to resolve issues with a tough customer. Most of the DAS elements being hidden above the ceiling tile, and spread out through a building does not make life easy. A System Map can help... actually quite a bit.

System Map is essentially a spreadsheet (i.e., hardware summary) that allows a technician to quickly trace DAS elements from head-end all the way to floor level where the antennas are installed.