In-building Components
The exact components that the enterprise (or the enterprise’s integrator or carrier) select will depend on the square footage requiring coverage, how many different wireless networks are to be supported, and the number of floors comprising the building. But the two basic components required to blanket a building or campus with strong cellular signals are a cellular radio-frequency (RF) signal source and a DAS.
* Micro base stations—The cellular source in larger organizations (100,000 square feet and up) is likely to be a small base station installed in the enterprise’s building and supplied by the enterprise’s mobile carrier(s), who owns the license to use the cellular spectrum. Some enterprise-sized base stations are called microcells; smaller versions are called picocells. Still smaller is an emerging class of product called femtocells, which are currently being deployed in residences by mobile network operators. Femtocells hold promise for distributed deployment throughout the enterprise without the need for a DAS (Table 1), but are not available yet as an enterprise-grade product.
“Femtocells will probably be the next big push,” said AT&T’s Erickson. “We’re right in the middle of evaluating what’s out there, the pluses and challenges.”
* Repeaters—An alternative to a small base station as an in-building RF source might be a nearby cell tower, whose signal strength is enhanced by a repeater supplied by an operator-certified third party and installed either on the roof or inside the building. Smart repeaters offer some management of the signal and are generally used in buildings requiring coverage of less than 100,000 square feet.
Spotwave is one supplier of smart repeaters for sites needing less than 50,000 square feet of coverage. Its equipment has been certified by all the major North American mobile network operators. Most Spotwave installations cost less than $10,000, according to Mike Roper, the company’s chief technology officer.
Microcells, picocells and smart repeaters are often used with distributed antenna systems.
* DASs—The DAS transports the carrier’s signals from antenna to antenna throughout the building via cabling. There are various architectural approaches to DASs. The differences, most notably, are whether the system uses passive or active components; the type of cabling it uses; and whether or not it supports more than one frequency and network type.
