Anyone who has been working in wireless infrastructure long enough will tell you that most technologies don’t last 30 years. They get replaced. They get absorbed into something newer. But distributed antenna systems (DAS) have been a different story. We’ve been deploying DAS for over three decades now, and rather than winding down, the industry is investing more, not less. Fortune 100 enterprises are still specifying DAS in new builds. Carriers are still designing around it. New use cases keep showing up.

So, what makes DAS the exception? The truth is, it comes down to a problem that never got solved by anything else.

A problem that only got worse

It was the desire to fix a long-standing problem in physics that ultimately led to the development of DAS. Since 1993, it has been increasingly difficult to get radio-frequency (RF) signals through steel, concrete, and glass. This is now much worse than before due to the increased use of new modern materials in construction, new types of window film on windows, and more densely populated buildings. The fundamental need to provide reliable coverage within buildings has only become greater as a result.

The earliest systems consisted of very basic technologies. Companies like Decibel Products and LGC Wireless built the first generation of passive coax-based setups, simple components that could extend an RF source into tunnels, train systems, and two-way radio deployments. Active DAS followed, using powered components to overcome the signal loss inherent in passive designs and adding the scalability and remote monitoring that integrators needed. An industry was born.

One early proof point that sticks with me: the 2002 Salt Lake City Olympic Games. I was the principal engineer on that deployment, engineering DAS solutions that provided multi-operator coverage for four mobile network operators (MNOs) across several venues, including Rice-Eccles Stadium. That project showed me firsthand what we've since confirmed over and over: DAS scales in ways that other in-building solutions struggle to match.

The technology didn’t stand still

If you’ve ever heard someone dismiss DAS as being legacy technology, they’re usually picturing systems from 15 years ago. DAS has evolved significantly since then. We went from systems designed with only five- to 10-megahertz of bandwidth and used only a few frequency bands, to modern DAS that can provide more than 300-megahertz of bandwidth using many different frequencies. These systems are now deployed at large commercial buildings in order to support several mobile network operators using a common shared platform. This is known as the neutral-host model. It has become the new standard among large enterprise and venue users.

The analog vs. digital DAS argument is a perfect example of how the industry has matured. When the digital form of DAS first came onto the market, people viewed it as the Holy Grail. However, we have found that this may or may not be true depending upon the application. For simple applications, analog DAS will always provide the least expensive option while providing all the necessary coverage. On the other hand, digital DAS will provide the most detailed level of control for more complex applications. Today's experienced system designers see both analog and digital DAS as complimentary tools rather than competitive.

Competing with small cells and BDAs – or completing them?

This is where the conversation gets interesting. Small cells and bi-directional amplifiers (BDAs) can be viewed as DAS replacements, but they do nothing to explain how we will deploy them in the field.

We’re seeing it firsthand. In many enterprise environments, small cells serve as the RF source that feeds into a DAS distribution network. The small cell supplies the RF signal; DAS provides the coverage area. Trying to provide coverage on a 500,000-square-foot corporate campus using only small cells creates a density and management issue that DAS resolves more efficiently. Similarly, BDAs and DAS components are increasingly showing up in hybrid configurations, particularly for public safety and life-critical emergency responder communication enhancement systems (ERCES) deployments where reliability isn’t optional.

The real story isn’t DAS vs. small cells vs. BDAs. Rather, modern in-building wireless systems are moving toward a hybrid architecture and DAS remains the common thread that makes the whole system work.

Where DAS is headed next

What excites me most about DAS isn’t where it’s been, it’s where it’s going. Today’s wireless platforms are now capable of supporting all major carrier bands at the same time while delivering multigigabit speeds across a shared infrastructure. In a recent Fortune 100 class A deployment, simultaneous download speeds exceeding 1 Gb/s were observed across AT&T, T-Mobile US, and Verizon on a common DAS platform.

DAS has also evolved to include private network capabilities and continues to evolve as an enterprise-wide solution for wireless communication. As such, Citizen Broadband Radio Service (CBRS) in the United States and select n78 bands internationally are now routinely supported, giving enterprises with dedicated wireless bandwidth above and beyond their service providers' coverage.

The next generation of DAS platforms will continue to increase support for large scale multiple-input, multiple-output (MIMO) technologies as well as expand the number of frequency bands that may be supported due to the increasing demand for in-building wireless services from 5G-Advanced.

Why it still matters

DAS isn’t surviving on momentum, it’s surviving because nothing else can agnostically extend mobile operator, private wireless, and public safety coverage inside buildings at the same scale. Until something else can do all three – reliably, across multiple operators, on a single infrastructure – DAS will remain a critical part of the wireless fabric that connects the buildings where we work, live, and gather.

Thirty years in, this technology is aging better than most of us. And if you’ve been in this industry as long as I have, you know that’s saying something.