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.

Behind the scenes making this innovation possible are AT&T engineers implementing a variety of strategies to meet the unique needs of each venue or building owner.

Chad Townes, Vice President of AT&T’s Antenna Solutions Group (ASG), oversees all of the company’s DAS installations. As Towne’s group began to notice smartphone trends and usage patterns skyrocket, increased emphasis was placed on getting ahead of the curve by installing DAS in a variety of locations, including sports venues. As Vice President of AT&T’s ASG, Townes is responsible for the end to end deployment of AT&T wireless infrastructure delivered via DAS. This includes the Sales, Negotiations, RF Engineering, Design, and Construction of both in building and outdoor DAS applications throughout AT&T’s network.

Bill Schlough, Senior Vice President and Chief Information Officer for the San Francisco Giants, sensed mobile data demand was on a sharp rise as early as 2009, which led his charge to create an extremely tech-friendly atmosphere at AT&T Park, home of the San Francisco Giants. Leading up to the 2010 baseball season, Schlough and his team already had an AT&T Wi-Fi system in place, but worked with AT&T to install a DAS to combat the data crunch coming from the nimble hands of smartphone-wielding fans at the ballpark.

Since the installation, the mobile experience at the ballpark has been night and day according to Schlough. While many fans might not know that DAS or Wi-Fi are powering their network at Giants games, they do notice the reliable and consistent mobile Internet connection they have come to trust and rely on to enhance the experience at games.

AT&T is a leader in the DAS space and annually installs hundreds of systems across the country. However, as new technology and opportunities present themselves, AT&T’s ASG will continue to adapt and modify the way its DAS perform and operate in order to provide the best possible end-user experience:

• Faster Speeds. As DAS deployments continue nationwide at sporting stadiums, campuses, airports and other venues, AT&T is beginning to upgrade and build new DAS with ultra-fast 4G LTE speeds.
• DAS on Wheels (DOW). At the recent major political convention in Charlotte, N.C. AT&T rolled out its first ever DAS on Wheels. The mobile DAS consisted of a mobile head end situated in an AT&T truck and portable antennas located throughout a major Charlotte Arena. AT&T is currently exploring future opportunities to deploy DOW.