Article #4 for the series 'Publishing RFP for DAS project'.

Provide coverage goal, DAS platform (optional) and test guidelines along with building information

Along with building information, it's a good practice to provide following information. If you are not sure about all the information, please contact us for a free spreadsheet.

1. Coverage goal: what kind of signal coverage you want the DAS to achieve?

2. DAS platform: If you have any preference for a particular DAS platform(s), this is the time to specify that. Most integrators, however, can pick a platform even if you don't provide it.

3. Test guidelines: provide some guidelines on the key indicators for sweep, PIM, OTDR and OLT tests.

Provide a coverage goal

Tell the bid participants the carriers signal you are expecting to broadcast through your system. Do you want all 4 carriers – like AT&T, Sprint, TMBL and Verizon, or do you just want 1 or 2? This is important to specify because they will have an impact on the design and price of the DAS.

This should include technology, signal strength & quality, and the percentage of the area you want your DAS to cover.

Specify to the bid participants what technology, signal strength & quality and percentage of area you want DAS to cover.

For example, for LTE – the 3rd line under technology, you can ask for RSRP of -90 dBM with signal to noise ratio of 12 at 90% of the coverage area. RSRP is a signal strength measuring parameter for LTE. All qualified DAS vendors will understand what you are asking for.

Coverage percentage is also important and can make an impact on the overall budget. I have asked for 90% in the table. Lot of times clients ask for 95%. Although this difference in area to be covered is only 5%, incremental cost can be quite a bit more.

Last 10% gets more expensive to cover, because in a lot of cases these areas are not easy or cost effective to reach  – especially in the higher frequencies – such as 1900 and up. In my opinion, user experience does not increase as much after 90% coverage, but the cost of DAS will.

Public Safety coverage is regulated by the Local Jurisdiction. If you know what they are, then use those numbers, if you don’t just go with this table.

It's also a good idea to provide channels and frequency information for the carriers. I have provided generic channels by frequencies to use as a baseline. If you know the exact information from the RF Engineers of the carrier or operator, use that information.

Provide channels and frequency information for the carriers. Getting information directly from Operators is always the best.

DAS Platform

Do you want DAS 2.0 (mixed coax & fiber) or 3.0 (all-fiber DAS)?

Do you have any specific DAS platform(s) or OEMs in mind? Give a few options. Or, you can keep this option open. Let the vendor select what they think will be the best solution for your campus. They deal with these situations all day long.

Most important thing here is that whatever platform the bid participant selects that has to be approved by the carriers you are trying to bring in.

You can also request top 3-5 reasons why vendors pick a particular DAS platform over other.

Provide specifications for all tests

When it comes to cable tests, it’s quite possible that different vendors may make different assumptions , and each assumption will create different types of cost, so it’s important to provide some guidelines to make the ROM from different vendors a level field.

There are mainly 4 types tests that you need to do during DAS construction.

1. Sweep test is for coaxial cables. Specify the bands you want the vendors to sweep, type of tests and passing threshold. Do you want them to do just segment test or both segment and system tests? In the template bid form, the tests I have shown will be acceptable by most if not all carriers.

2. PIM or passive intermodulation test is another test for coaxial cables. Specify the bands you want the vendors to test and what is the passing threshold. Do you want them to do just segment test or both segment and system tests?  For the template form, we are using the values that should be acceptable by all carriers.

3. OTDR test for fiber – do you want unidirectional or bi-directional and what wavelength? A Unidirectional OTDR should suffice. This test is mainly required by the Operators. However, OTDR test itself does not add a lot of value to the DAS. OLT tests for fiber is more important for DAS verification.

4. Optical loss tests: all DAS gears have their own optical budget or optical loss they will allow to make the system perform optimally. You can just ask the participants to match the passing optical loss required by their proposed DAS platform.

Feel free to customize the cable test parameters as you deem appropriate for your project.

Related Articles:

ROM based RFP: Framework

Building information you need to provide for ROM bid

To download the ROM-based workbook template, please contact us.