A distributed antenna system (DAS) is a system designed to extend the coverage of typically outdoor wireless services such as cellular, private radio systems, public-safety radios, etc., but can also be used for indoor wireless, such as wireless LANs. The penetration of these services into buildings varies with their frequency and power, but it is generally difficult for an outdoor signal to cover a large space inside a building well. A distributed antenna system can function as a repeater, or it can be used to provide complete infrastructure for the wireless services.
A distributed antenna system is a connected
network of antenna sites called nodes that provide wireless service within a
geographic area or structure. The individual antennas are typically mounted on
top of light or utility poles, in secured cabinets, or in ceilings.
Since DAS originated within the cellular
industry, it should come as no surprise this is also where they are currently
most effective. The current common use for a distributed antenna system is for
extending coverage in the cellular industry for both voice coverage and data
coverage. Other applications are on the horizon for these systems such as
building management, energy management, physical and other security, and, even
provisioning WLANs are just a few examples of this growing market.
In some areas, the use of a distributed
antenna system just makes sense. For example, in the health care industry,
areas such as operating rooms have to remain sterile, so maintenance to
equipment in the rooms or installation of new equipment can cause harmful
disruptions. DAS should be installed either when the hospital is built or is
under renovation. The same can be said for lab areas, where precision
measurements and testing requires a clean room.
Another use for a distributed antenna
system would be in a high security area with restricted access. Typically,
encryption and authentication methods in these areas are beyond AES and 802.1X,
such as FIPS 140-2 and the encryption standards for classified communications
are also in place. DAS can work in these areas carrying WLAN traffic for only
authorized personnel.
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