* Using distributed antenna systems for internal cell coverage
In-building cellular coverage is notoriously spotty or non-existent. And underground areas stand nary a snowball’s chance in Hades of picking up a cell signal — at least, not without a little technical help.
International law firm K&L Gates was keen to this situation when it planned construction of a new building in Washington, D.C., for relocating its employees. Because of a 13-storey building height limit in the U.S. capital, the company built three underground floors that housed support staff and parking facilities, explains Rodney Carson, the firm’s local director of administration.
K&L runs a traditional Siemens PBX and desktop phones for business phone calls. However, as part of its disaster recovery emergency plan and for personal calls, Carson says, there are 500 K&L users with cellular connections. To provide internal coverage to those devices, K&L installed a distributed antenna system (DAS) from LGC Wireless, a project that was coordinated by Glasgow Group Inc. (GGI), a Great Falls, Va., telecom consultancy.
DASs, also available from companies such as Inner Wireless and Mobile Access, pick up signals from a local, carrier-provided radio frequency source and distribute them, via cabling, to antennas strategically positioned throughout the company for the best coverage. LGC’s system, an “active” system, not only repeats signals but also boosts them along the way over shielded twisted-pair wiring.
K&L has two populations of cellular service users, each using different carriers.
“So the DAS configuration had to be able to support feeds from two operators,” explains Richard Glasgow, president of GGI. The network carriers themselves provide small base stations, often called picocells, as the RF source. K&L purchased both the DAS and the carrier picocells.
About 250 K&L attorneys and company managers carry Research In Motion BlackBerry 7290 voice/data devices that operate on T-Mobile service. T-Mobile provides a T-1 link from its central office to a local picocell, which connects to the DAS.
Another 250 users have their own cell phones for personal use, most on the Verizon Wireless network. Verizon provides an air interface from a local picocell to the DAS.
Once some post-installation antenna-location tweaking improved coverage on a couple of floors, Carson says internal cell use has been “smooth.”
The most difficult aspect of the project? Carrier cooperation. More on this issue next time.
