411 on DAS

September 28, 2017 at 8:00 AM

 

If you’ve ever lost your cellular signal in a building that you thought would be covered by your cellular network, you probably would have appreciated the help of a distributed antenna system (DAS). Today’s construction techniques and materials block or weaken internal and external wireless communication signals inside buildings. Blocked radio and cellular reception isn’t only a nuisance for consumers, it can be detrimental to public safety and hinder first responders in an emergency situation. Thus, distributed antenna systems were designed to counteract those effects and extend wireless coverage within structures to allow radios and cell phones to work everywhere within the building.

 

A distributed antenna system uses several small antennas, as opposed to one antenna, to provide wireless coverage and eliminate spots of poor coverage inside a large building. These antennas serve as repeaters and provide reliable coverage within the structure, without requiring much additional power. They provide voice and data services, just like a cellular tower would, without any noticeable difference to mobile device reception. Any densely populated indoor space is a good candidate for DAS deployment, such as shopping malls, medical centers and high-rise buildings. Distributed antenna networks also provide wireless coverage to hotels, subways, airports, hospitals, businesses, roadway tunnels and more. In addition to indoor use, a DAS can be designed to extend wireless coverage for outdoor use. Distributed antenna systems typically provide wireless services that include PCS, cellular, Wi-Fi, police, fire and emergency services.

 

A DAS often uses RF directional couplers and/or wireless amplifiers to split and amplify the wireless signal from the source to the distributed antennas. In many cases, a DAS will use a combination of low-loss coaxial cabling as well as fiber optic cabling to support radio-over-fiber (RoF) technology and distribute the wireless signals to the antennas. The antennas are physically connected to a central controller, which is then connected to the wireless carrier network’s base station. At least one carrier network must be involved with a DAS deployment because the systems operate on the RF spectrum, which is licensed to wireless carriers.

 

Distributed antenna systems can be passive or active. A passive DAS grabs cellular signals from roof antennas and runs them through leaky feeder cables that distribute the signal throughout the building. An active DAS passes the signal from the roof antennas through fiber cables, boosting and amplifying the signals as needed.

 

Deploying DAS is the most expensive aspect of the project, as it can be very labor intensive to install the antennas and run cables between antenna modules and the controller. Usually, the carrier network manages the cost and maintenance of the DAS system, as long as it aligns with their network plan and fills a significant gap in service. Responsibility for a distributed antenna system may be shared by multiple carriers to keep costs down.

 

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