A Distributed Antenna System (DAS) has several antennas as opposed to one antenna to provide wireless coverage to the same area but with reduced total power and additional reliability. A DAS use RF directional couplers and/or wireless amplifiers to split and amplify the wireless signal from the source out to the distributed antennas. Most of the times DAS will use a combination of low loss coaxial cabling as well as fiber optic cabling supporting radio over fiber (RoF) technology to distribute the wireless signals to the antennas. The wireless services typically provided by a DAS includes PCS, cellular, Wi-Fi, police, fire, and emergency services.
antenna system (DAS) or a distributed radio system (DRS) generally refers to a
radio access architecture comprising a large number of antennas distributed
widely across a large coverage area and connected to a centralized Access Point
(AP). The radiation coverage of each antenna typically has a much smaller
footprint than that of a base-centrally-located antenna/base station in a
conventional cellular system.
The DAS architecture has two main advantages:
First, it is possible to achieve high spatial re-use capacity due to the small coverage area of each antenna.
Second, the centralized access point has complete control of all the radio resources used for each antenna and can, therefore, coordinate the transmission and reception of signals to minimize interference in an increased system capacity.
A DAS installation consists of a network of separately installed antenna nodes that are connected to a common source through fiber or coaxial cable. Typically, the antennas in a DAS connected to the AP through optical fibers. The AP may process the received (uplink) signals from multiple devices using appropriate combining techniques, such as maximum ratio combing (MRC) or interference rejection combining (IRC). On the downlink, the AP may transmit to multiple devices using zero forcing or dirty paper coding to suppress interference if the forward link channel is known.