Today's enterprises embrace wireless applications that depend on an array of wireless technologies and frequencies. While IT departments are most familiar with WLAN-based applications, consider the escalating indoor use of mobile phones and PDAs, the regulatory push for public safety radio coverage in large venues, and the buzz surrounding new Mobile WiMax and 4G technologies.
Unfortunately for the IT department, most large enterprise facilities are black holes from a wireless perspective-wireless coverage doesn't just happen. Most often, RF (radio frequency) signals are blocked by a building's reflective glass coating or signals are absorbed by dense structural materials so they're unable to evenly penetrate the building's core. To ensure "five-bar" wireless coverage indoors, IT managers need to deploy a "plumbing" infrastructure for wireless. Known as DAS (Distributed Antenna Systems), these infrastructure solutions overcome a building's inherent structural impediments and deliver robust wireless coverage throughout the facility.
What Is a DAS?
At the simplest level, DAS solutions provide a wired path for delivering wireless services. They use a cabling infrastructure for RF signal transport from signal sources to a network of distributed antennas that broadcast signals throughout a facility. The DAS cabling infrastructure may employ coaxial, fiber optic, or Category 5/6 cabling in various combinations.
Of course, to function, a DAS must be connected to the RF signal sources associated with wireless services. The simplest option is to "siphon" wireless signals from a nearby cellular tower using a rooftop antenna linked to a BDA (bidirectional amplifier). While this approach is simple, it can impact a carrier's macro network. For a larger investment, a carrier can also place a wireless BTS (base transceiver station) inside the facility with a T1 backhaul connection to its macro network, thereby improving capacity of the larger network.
Once a signal source has been established inside a facility, signals are "distributed" at the building core to ensure even indoor coverage for a variety of RF services. The newest flavor of DAS on the market also supports integrated WLAN capabilities over DAS cabling, eliminating the need for separate WLAN-only wiring. This approach enables IT departments to cost-effectively piggyback their WLAN deployment over the same infrastructure used to support other wireless services.