Carrier Approved
Off Air

Passive DAS

In Passive DAS, the signal source (which is BTS outsite or Antenna on the roof) connects to a cellular amplifier or repeater, which then connects to the distributed antenna around the building or facility using coaxial cable and splitters, where appropriate. There is no amplification between the repeater and the distributed antennas, hence the name passive distributed antenna system.

There are limitations to the reach of passive DAS solutions. Because they use coax cable to distribute signal, signal loss is higher than with active DAS. The further away the antennas are from the amplifier, the higher the signal loss. The signal loss results in lower downlink output power.

But the advantages of passive DAS solutions are considerable. In particular, they are considerably cheaper than active DAS. Because they typically rebroadcast the macro network’s signal, there is less need for carrier approval and coordination.

Off-Air DAS

  • Off-Air, or Passive DAS, uses a Donor Antenna on the exterior of a building that connects to the closest cell site and re-amplifies signal in a building (using a device called a Bi-Directional Amplifier or BDA). This is essentially a glorified antenna system. This means that Passive DAS heavily rely on adequate signal from a nearby cell tower. So, if you have good signal at the Donor Antenna this is a cost-effective solution for many venues that simply have a coverage (not a capacity) problem. 
  • A passive DAS uses passive RF components such as coaxial cable, splitters, taps and couplers to distribute signal inside a building. The farther the antenna is from the signal source and any amplifiers, the more attenuation (loss) there will be in the power broadcast from that antenna.
  • There are a number of manufacturers of Passive DAS systems using BDAs: Wilson Electronics, SureCall and Nextivity e.g. Nextivity’s Cel-Fi Quatra product is an excellent choice if you have existing CAT5/6 in your building (most products utilize coax).
  • These solutions had been frowned upon the carriers prior to FCC approval of the technology in 2013, but that has ended and for many customers it is the solution of choice.