Backhaul in the spotlight
By Dan O'Shea

For being a portion of the network most mobile users aren't much aware of, mobile backhaul transport has been getting a lot of attention the last year or so, and this week's Wireless 2007 in Orlando will be the second straight CTIA show at which backhaul has been a hot topic. Then again, backhaul still isn't likely to become something users are aware of unless it fails.

The mobile backhaul market is undergoing great change as many new product and architectural approaches look to replace the leased T-1 lines that currently account for roughly 95% of the backhaul facilities in the U.S. Those T-1s are costly and inflexible to potential future growth in mobile broadband applications, which itself is likely to proceed along an unpredictable, incremental growth track.

Vendors are rushing to help carriers address their backhaul concerns and create new backhaul strategies. Among those vendors, Tellabs this week will issue a new case study about its work with Telecom Italia to help the carrier of mobile broadband and fixed/mobile converged services use pseudowire technology to backhaul mobile traffic over ATM to its Ethernet backbone.

Elsewhere on the show floor, Dragonwave, the fixed wireless vendor that earlier this month announced its Horizon Compact product to address cellular backhaul needs with wireless Ethernet, will have that product on display. The system is a Gigabit Ethernet microwave transmission system that offers 800 Mb/s full duplex capacity and operates at frequencies between 11 GHz and 38 GHz, said Erik Boch, cofounder, chief technology officer and vice president of engineering for Dragonwave.

“The frequencies up to eleven gigahertz are very congested and not good for backhaul, and above thirty-eight gigahertz, the propagation limits start to make it more of a short-haul technology,” Boch said. “As more common carrier bonds open up, that will probably happen at eighteen gigahertz or above, where there is clearer spectrum for backhaul. Twenty-four gigahertz is good because it's unlicensed, but its uses are highly regulated for point-to-point applications.”

Boch said that although the potential for rapid bandwidth growth in mobile broadband networks is causing the industry some concern, the bandwidth increase isn't as much an influencing factor for backhaul as the changing nature of connection sessions. “Video is a mobile application that's getting a lot more interest, and fundamentally, it's the difference between that sort of data connection event and a regular voice connection event that is driving backhaul bandwidth needs,” he said.

Meanwhile, among other new backhaul trends, some vendors say mobile carriers may be candidates to own backhaul transport or last-mile facilities that they currently lease. Even as T-1 leasing costs are declining, overall leasing costs may tend to increase as mobile carriers have more mobile switching centers and offices to reach in their largest markets.

“It's like a real-estate transaction because generics don't apply, and it's just the realities of a given market,” said Michael McCalpin, a network architect in the wireless market development group for Fujitsu Network Communications. “If you've got seven [mobile telephone switching offices] in one market, it might make sense to own the transport and still lease the last mile.” Fujitsu is targeting its Flashwave 4500 multiservice switching platform and 7500 ROADM solutions at this potential new trend.

“Some wireless carriers have viewed backhaul as just a last-mile issue, something they write a check for, but that view is too limited,” he said. “When we first went to carriers about this idea, they didn't give us the time of day, but now we have three RFPs going. They are feeling the incentive to do something about backhaul.”

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