Control At The Core: Lucent preps for wireless evolution with open, client/server approach

Lucent Technologies plans to inaugurate the next generation of wireless network design this week with the introduction of a standards-based, network-centric evolutionary scheme.

At the Cellular Telecommunications Industry Association's Wireless '98 show in Atlanta, Lucent will unveil Flexent, a modified network architecture intended to allow code division multiple access (CDMA) operators to leverage existing investments as they move toward third generation capabilities.

"3G to some vendors means a parallel network," said Bob Sellinger, director of PCS product marketing and business development at Lucent. "We see a very step-wise, smooth, natural migration that protects investment."

Flexent follows a traditional client/server intelligence distribution model. The mobile switching center (MSC) acts as the server that consolidates control and processing resources and offers them to all network clients, which in the wireless network case means radio base stations. The key to that structure is maintaining a standards-based, open approach to ensure that carriers have multiple vendor options.

"No vendor and no carrier wants to go down the 3G path with a proprietary network," Sellinger said.

The first concrete example of the Flexent scheme is Lucent's new CDMA microcell and applications server. The applications server is an open computing platform attached to the MSC that contains the majority of the radio control functionality for the microcell. Centralizing those control functions translates into cheaper and smaller microcells, Sellinger said.

"Unlike some of our competitors that see functions being increasingly decentralized, and that tout wireless as good base stations and the network as somewhat secondary in importance, we have the opposite opinion," Sellinger said. "In the future, wireless networks will be more than just good radios. It is the network that will provide the distinguishing traits in the long term, and the radio will become more of a commodity."

Canadian PCS operator Clearnet is currently evaluating the new Lucent microcell architecture for potential use in the corridors and valleys of its network and for in-building applications. The idea of daisy-chaining more compact microcells allows flexibility in network design, said Stephen Howe, director of RF engineering at Clearnet.

"Centralization saves a lot of processing power," Howe said. "It's a good sign because it should save real estate. It also becomes a pretty quick deployment option for us."

One industry analyst said the success of Lucent's design will depend on achieving an optimal balance of intelligence between the switch and the radios, but the most crucial issue is adhering to open standards.

"They feel it is not cost-effective to have a totally distributed network because you're replicating functions in other parts of the network," said Herschel Shosteck, president and CEO of Herschel Shosteck Associates. "The important aspect is that Lucent recognizes that it can't hold on to a proprietary switch. The reason the switch must be opened is that no one knows what the future applications are going to be."

On the subject of open standards, Sellinger noted that as wireless networks become more versatile transport vehicles, asynchronous transfer mode technology will play an increasingly important transmission role. To account for that, vendors must develop their gear to IS-634 Revision A, the only industry standard that embraces ATM connectivity of radios and switches, he said.

"With 3G, you need megabit or higher data rates to connect the radios back to the switch," Sellinger said. "ATM is critically important to delivering the promise of 3G."