What is Carrier-Grade DAS?

Why can't we get cheaper DAS options from the Internet?

Wireless Service Providers such as AT&T, Sprint, Verizon and T-Mobile have spent billions in acquiring spectrum (signal frequencies) and spent even more developing their cellular networks. They want to make sure that any network built by a 3rd party (DAS for example) will not negatively impact their existing network. When we are deploying a DAS, if it's not properly engineered it can negatively impact these carriers' networks.

A carrier-grade DAS is one that is built with (carrier’s) laboratory approved hardware, exacting engineering specification, and goes through rigorous and tests and data collection.

Hardware (DAS platform):

Carriers usually have a set of approved DAS platform they will use. This means that if they were building their own DAS, they would use these platforms only. Corning and Commscope are common for all carriers. There are other DAS platforms such as ADRF, JMA, SOLiD where none of the carriers will have any issue connecting their signal sources. All of these platforms have gone through multi-parameter testing at Carriers laboratories.

Design and Engineering:

To design and build a carrier-grade DAS, carriers will expect you to follow certain processes and produce common deliverables.

Benchmark Data Collection: This tells carriers the current level of signal coverage inside the building. From the benchmark, data engineers will also determine coverage goals for each carrier by following their engineering requirements.

iBwave Design: iBwave has unofficially become an industry standard for the design and engineering of a DAS. Engineers have to enter all site-related information, and it will run link budget and propagation analysis to produce the following deliverables:

1. Logical Diagram

2. Floor Plan with Device Locations

3. Bill of Materials

4. Propagation Plots at desired frequencies

5. Various other reports such as SINR, MAX Data Rate, EMF Reports

The first 3 documents are sometimes called construction-ready documents because you can actually build the DAS from these 3 documents.

Engineers will also produce other important documents like elevation drawing, connection line diagram, etc. to help the low voltage vendors and equipment installers with their work.

Tests and data collection:

DAS engineers run 3 types of tests that will be common for most carrier-grade DAS:

1. Sweep and PIM (Passive Intermodulation) tests for coaxial cable

2. OTDR and Optical Loss Tests for fiber optic cable, and

3. CW (Continuous Wave) test on the completed system

Purpose of these tests are:

1. Finding a fault or defect in the system

2. Signal continuity at intended frequencies

3. Reducing loss while the signal is traveling through the system

4. Minimizing interference

During CW tests, engineers pass un-modulated (i.e., blank) signals through the system to make sure that the system is optimized for transmitting desired cellular signals.

All these approved gears, rigorous design, engineering, testing, and optimization can easily raise the price of carrier-grade DAS. Yes, you can get inexpensive repeater-based DAS on the internet, but make sure that engineers from carriers will be okay with that system.