distributed antenna system (DAS)

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.

Over the past five years, wireless data traffic has increased more than 20,000 percent on AT&T’s wireless network alone. People are no longer only accessing the Internet at home or in the office, they are doing it wherever they are from their mobile device.

AT&T network engineers are helping enable this shift in Internet usage habits by putting in place new technologies, such as Distributed Antenna Systems (DAS). A DAS network consists of many antennas tuned to precisely match the areas of a building or venue where boosted service is needed. AT&T DAS helps address the exponential network traffic growth at large venues and other hard to serve areas, such as sporting and entertainment venues, hospitals, college campuses, airports, hotels, conference centers and more.

DAS helps boost mobile broadband coverage, improve reliability in heavily trafficked areas and enhance network capacity, alleviating pressure on wireless networks when thousands of people in close proximity are actively using their mobile devices simultaneously. DAS is seamless and invisible for customers, but the results are easy to see. Data and voice capacity more than doubled at the pro sports venues that installed AT&T DAS in 2011.