Distributed Antenna Systems (DAS) are the most common method selected by operators to achieve Inbuilding coverage and capacity. Traditionally, the same macro cell base station deployed in the outdoor environment has been deployed indoors to serve as a signal source to feed a network of antennas distributed throughout the venue. Alternatively, a repeater or bi- directional amplifier (BDA) can be deployed as the signal source to amplify downlink signals from a donor site as well as amplify uplink signals from users inside the building. In either case, the network equipment manufacturer’s base band processing and radio resources are centrally located, either in a DAS head-end equipment room at the venue or in the shelter of the donor site in the case of a repeater / BDA.
Distributed Antenna Systems (DAS) are able to accept RF inputs from a variety of signal sources, making them network equipment manufacturer as well as technology (2G, 3G, 4G) neutral. For this reason, a DAS is often the IBW system of choice for multi-operator, multi-manufacturer, multi-technology applications. Many different types of DAS exist today based on the method used to distribute the network equipment manufacturer’s RF signals to the remote antennas. These include passive DAS, active DAS, hybrid DAS and recently introduced Digital DAS.
In a passive DAS, signals from one or more RF sources are distributed throughout the venue using only passive components (coaxial cable, splitters, directional couplers, etc.). Beyond the signal sources, there are only losses (no gain elements.) Sectorization is determined by hard wiring capacity from each signal source to specific zones within the building.