Distributed antenna systems: A cell tower inside your building
Jade Communications Staff | 01/19/2017
A distributed antenna system (DAS) solves the problem of poor coverage by linking an array of antenna modules to a central controller, which then connects to the wireless operator’s base station. Unlike a cellular repeater, which collects in-building wireless signals to rebroadcast outdoors, a DAS includes all of the components of a cellular tower.
“A DAS is essentially an in-building cell site, with its own wired backhaul to the operator network. In some cases, a DAS will connect to another cell site wirelessly, but the goal is to take pressure off of the operator network, not add to it,” said Peter Jarich, a research director for wireless infrastructure.
Distributed antenna systems are transparent to mobile devices, providing both voice and data services to mobile devices like any tower on the cellular network. DAS units are also largely vendor neutral, allowing any number of operators to support multiple wireless services, such as 2G, 3G and 4G, on a single DAS platform.
“Like cellular towers, we partner with other operators to share space on a DAS. After we deploy a system, we actually turn it over to the tower folks to let others tap into it,” said Jim Parker, senior manager at an Antenna Solution Group.
Because distributed antenna systems operate onspectrum licensed to wireless operators, an enterprise cannot undertake a DAS deployment without involving the operators. In fact, wireless operators initiate the majority of DAS deployments, Jarich said. Wireless operators use both their own proactive traffic monitoring and customer feedback to determine locations to deploy distributed antenna systems, according to Parker. Densely populated spaces, such as shopping malls, medical centers and high-rise buildings, are likely candidates for DAS deployments. In such cases, the wireless operator will bear the costs of installing the system, as well as ongoing maintenance expenses.
When Parker’s team identifies a location that can benefit from a DAS, it engages the site's owner or manager to work out an agreement for the space needed to house the DAS components. Deployment is the most expensive stage of a DAS project because installing antenna modules, stringing fiber optical or coaxial cable between antenna modules and the controller, and installing a base station are all very labor intensive processes.
In many deployments, a carrier will install a separate wireless LAN infrastructure for hotspot access alongside the DAS solution, said Parker. A Wi-Fi hotspot deployment in parallel to a DAS enables operators to offload wireless data traffic from its stressed cellular networks, saving the spectrum for voice traffic. Many of the operator’s smartphone offerings, including the iPhone and BlackBerry devices, are pre-programmed to switch to Wi-Fi whenever they are in range of a global Wi-Fi network, completely transparent to the user.
While a distributed antenna system may sound like the perfect solution for your cellular coverage woes, there is no guarantee that a wireless operator will agree to install one for your enterprise facility. DAS solutions are an expensive proposition, both in terms of equipment, installation and ongoing maintenance costs. The carriers will only agree to take on these costs if the deployment fits within their network plans, covering a large number of their subscribers or filling an obvious gap in their service. Likewise, a DAS solution is ultimately owned and managed by the wireless operator and not the building management or tenants, which means a building owner cannot relocate or add to the antenna arrays.