What is a DAS and where are they used?
8 January 2014 - 22:20, by , in Blog, 7 comments

DAS is the acronym we use in the wireless industry for DISTRIBUTIVE ANTENNA SYSTEM (DAS).

A Distributive Antenna Solutions can connect to a variety of wireless services and then rebroadcast those signals throughout the areas in which the system is installed. The applications can include cellular service from multiple wireless carriers, public safety radio frequencies, and Wi-Fi. Campus style environments can benefit greatly from DAS systems. In a medical clinic or hospital the special medical wireless systems it uses also can be supported with a DAS solution as well as cellular e, Wi-Fi and public safety.

DAS

To understand how a DAS operates, it helps to know some of the methods by which wireless signals are propagated. Nearly all of us know what a cell tower looks like; well, each of those towers carries antennas for one or more macrocells (multiple carriers when there are “layers” of antenna arrays). Wireless carriers use microcells to add capacity in areas with a high density of mobile wireless device users. In a DAS setup, any or all of these technologies may come into play.

Now that we know we’re “inserting” signals, the next logical step is to think about what we’re doing with them. Every DAS has a “head end” into which these source signals are combined for distribution. The signals are amplified and carefully “combed” together as needed, in the electronic equipment and filters at the head end. Intermediate amplifiers (usually referred to as bi-directional amplifiers or BDAs) are added to make up for signal losses due to the physical limitations in how far a cable can carry the signal. Cables then carry the signal out to passive antennas placed where more signal strength or coverage is needed. A DAS might use fiber from the head end to the remote BDAs, plus coaxial or shielded Category 5/6 cable from there. One of the selling points of a DAS is that a properly designed and installed system is able to support all your wireless traffic: Wi-Fi, cellular, PCS, paging, maintenance, and public safety. Just be aware that each of these technology types uses different radio frequencies, which directly affects the DAS design and the type of antennas to be installed in the buildings. It is best to decide in advance which wireless systems the DAS needs to support.

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