Another hotel has "done the DAS thing" by installing multi-carrier distributed antenna systems throughout its property so that guests and residents have clear indoor access to their cellular provider of choice.

This time it's the 92-story Trump International Hotel & Tower in Chicago, the second tallest building in the world next to Chicago's Sears Tower. As you likely know, the higher you go, the tougher it is to provide cell service directly from the carriers' outdoor macro cell towers.

"Cell towers are designed to cover people at street level. Their goal is a horizontal plane, not a vertical plane," says Jerry Chang, IT director at the Trump hotel and condominium property, which opened in February 2008.

Distributed antenna systems (DAS) amplify licensed signals from a source base station or microcell provided by each cellular operator across fiber or coaxial cabling throughout the premises to distributed internal antennas. Chang discovered the DAS alternative during the building construction phase.

"Sprint was already in the building, because our construction company needed Nextel signaling for workers," Chang explains. "We started talking to Sprint," which pointed Chang's team toward the fiber-based InterReach Fusion DAS from ADC. Among other suppliers that support multiple cellular carriers' signals are Andrew, InnerWireless and MobileAccess.

"The only thing we specified was that we wanted [a DAS] robust enough to layer on other carriers," Chang says. "[Sprint] installed all cabling, fiber and coax" but all the carriers – Sprint, AT&T, T-Mobile and Verizon – are funding their own signaling source equipment, he says.

Sprint is on its own ADC system, which uses six main hubs, 25 expansion hubs and 168 remote antenna units. The Sprint DAS captures Sprint signals from a Sprint outdoor macro cell tower using a rooftop antenna and captures Nextel signals from a micro base station in the hotels' network operations center.

A separate system is needed for Sprint because of a "potential [interference] issue with [Sprint] Nextel iDEN signal and the AT&T uplink/downlink," Chang says. Nextel has also come under fire for potentially interfering in 800MHz public safety networks.

So ADC designed a multicarrier system to work with the other vendors. Verizon Wireless is on DAS No. 2 and provides remote monitoring services. Trump is still working with AT&T and T-Mobile to get them onto that same system.

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.