Handing it to the carrier
UMA-based services do away with the need for an on-site server. Instead, these functions are shifted to the UMA controller in the carrier network, acting as an interface between the IP world of a WLAN and the mobile carrier's core network. Kineto Wireless is a UMA vendor, and T-Mobile uses the gear for services like Hotspot @Home."
One company testing out T-Mobile's UMA offering is Anthony Marano Company, a family-owned fresh-food distributor. The company since 2004 had been using a jointly developed, dual-mode solution from Motorola, Proxim Wireless and Avaya, with dual-mode handsets, a 75-access-point 802.11a WLAN, and a SIP-based PBX with software to manage the handoff with the cellular network. In general, the systems worked well, says CTO Chris Nowak. But one problem is a wireless "speed limit": Employees zipping around the 460,000-square-foot warehouse on pallet jacks or other vehicles lost the Wi-Fi connection when they drove at more than a few miles per hour.
The company wants to upgrade, and last fall deployed a pilot WLAN from Extricom, with six antennas distributed through the warehouse, and about 50 UMA-enabled BlackBerry 8320 handsets with built-in cameras and Bluetooth, on T-Mobile's cellular network. Extricom uses what it calls a channel-blanket architecture. The 802.11 media-access-control functions run entirely on a central controller, so the "access points" in the warehouse are nothing more than antennas. There is no handoff among them because the entire system in effect works as one access point.
The sleek new BlackBerries "see" the Wi-Fi network via a one-time scan. The user enters a key, and the device registers via IP and the Internet with the T-Mobile UMA controller. The controller "knows" where each handset is, uses the appropriate wireless connection for the voice call and shifts between them seamlessly. "I'm happy not to know how all this works, as I have to know with the Avaya gear," Nowak says. The handover "works most of the time and that's good enough for us," he says.
The Extricom WLAN has been a key element in the quality of the service. "We're not worrying now about co-channel interference," Nowak says. "That was a constant issue [in the past]. We were constantly changing [radio] power levels and channels to make it 'just right.'"
Nowak is evaluating the additional capabilities the carrier can offer, as well as the degree to which T-Mobile will be able to offer PBX-like functions and how important they are to Anthony Morano.
