DAS technology was originally developed as a two-way radio communication system using radiating cable within tunnels, mines and subways. Today, in addition to two-way radio communications, DAS is also used in emergency response systems and in areas needing licensed wireless access (hotels, casinos, arenas, airports, etc.) due to high densities of people and high bandwidth levels. With the emergence of 5G, DAS is also a viable solution to bring those licensed network signals indoors.
A DAS uses fiber, coax cable and antennae to distribute signals inside a building either from a donor antenna or a direct connection to the carrier network via a base transceiver station (BTS). Each floor of a building is equipped with a remote unit (RU) that is fed from the DAS Head End Unit (HEU) with fiber optic cabling. The RU converts the light source back to an RF signal (600 MHz to 2700 MHz) and is connected to several passive antennae through low-loss coaxial cable. The DAS provides two-way wireless communication between the carrier and users. This approach enables owners to extend licensed networks inside their buildings. To better understand this system, each part of a DAS will be discussed.