A distributed antenna system (DAS) is a way to deal with isolated spots of poor coverage inside a large building by installing a network of relatively small antennas throughout the building to serve as repeaters.
The antennas are physically connected to a central controller which is connected to the wireless carrier network’s base station. Because distributed antenna systems operate on RF spectrum licensed to wireless carriers, an enterprise cannot undertake a DAS deployment on its own without involving at least one carrier.
Distributed antenna systems can be passive or active. A passive DAS grabs cellphone signals from antennas on the roof and runs them through leaky feeder cables throughout the building. In this approach, the signal leakage distributes the signal. In an active system, the signal is passed from roof antennas through fiber cables. Along the way, systems boost and amplify signals as needed.
Deployment is the most expensive stage of a DAS project because installing antennas and stringing fiber optical or coaxial cable between antenna modules and the controller are all very labor intensive processes. Generally, the carrier bears the costs of installing the system as well as maintenance expenses and many times, the carrier will only agree to take on these costs if the deployment fits within their network plans, covers a large number of subscribers or fills an significant gap in service. To keep the cost down, a DAS may be shared by multiple carriers.
Distributed antenna systems are transparent to mobile devices, providing both voice and data services to mobile devices just like any tower on a cellular network. Densely populated indoor spaces such as shopping malls, medical centers and high-rise buildings are all good candidates for DAS deployments.