An Alternative ApproachBy David Strom | Posted 2009-03-04 Email Print
For wireless applications to function properly, they require the right in-building coverage, which involves more than just proper antenna placement and access point design.
A different method is used by ADC and Powerwave. They have a separate antenna array for each wireless service, connecting each via standard Category 5 twisted-pair wiring to bring the radio signals back to the floor’s wiring closet. This has the advantage of using common wiring that is probably already installed and is well-understood by most corporate infrastructure engineers.
ADC places more active elements closer to the users, which can be more costly, depending on the configuration. The trade-off is using cheaper passive antennae but having more expensive cabling compared with a single set of active antennae that are less expensive than cable but require separate antennae. Part of the biggest cost component of any antenna installation is the final few yards of cabling that will go closest to the users.
“There is a big labor cost to go in the ceiling, and the less you can do there and the more you can do in the wiring closet when you want to add your second and third frequency band, the less costly your job will be,” says GE Healthcare’s Sbihli. “You might also design a system for future expansion so that you don’t have to pull more cable two or three years from now.”
That was the motivation behind the design of the Comcast Center, an office tower in Philadelphia that is the home office of Comcast Corp.
“We wanted an in-building antenna system to future-proof the building,” says Fred Dougherty, vice president of portfolio technology for Liberty Property Trust and the developer of the skyscraper. “Given the height of our building and the fact that we were using low-energy emissions glass cladding that would block a lot of cellular radio transmissions, we had to do something to support four major cellular carriers and Wi-Fi throughout the complex.”
Liberty chose MobileAccess to deploy its wireless solution after evaluating several vendors.
“Each tenant can connect its private network to the MobileAccess equipment and benefit from a fully engineered wireless network distribution system in its space,” Dougherty says. “The reliability of the system is exceptional, and all of our property management and building staff have superior communications. Wireless coverage is complete, without interference or any signal loss throughout the building.”
Supporting in-building wireless requires a lot of planning and specifications development. For example, the Comcast project started seven years ago when the first requests for proposals for its IT infrastructure were created.
The good news is that the technology is improving, and it’s getting easier to support multiple wireless frequencies.