When urban microwave backhaul makes sense for wireless operators

By Jessica Scarpati 17 Sep 2009 | SearchTelecom.com

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"When compared to the costs of leased access and to other backhaul solutions, our microwave system provides a significant advantage for our WiMax service." John Saw CTO, Clearwire Communications

"Especially in an urban area, microwave is making a lot more sense just by virtue of how choked up a lot more things are in the ground," said Mike Jude, a program manager in consumer communications services at market research company Frost & Sullivan.

"Will a microwave backhaul link ever be up to the same standards as a fiber link? No," Jude added. "But if you're a new entrant [to the wireless operator market], then using microwave is a pretty good way to get into a market relatively cheaply."

Clearwire Communications, a wireless broadband Internet services provider (ISP) based in Kirkland, Wash., has built its wireless backhaul networks in Atlanta and Las Vegas almost entirely with microwave, said CTO John Saw. The company recently announced it would be testing a 20-square-mile site in Silicon Valley for its 4G WiMax service.

"We aren't applying a specific figure to the savings our microwave structure will allow us to realize, but when compared to the costs of leased access and to other backhaul solutions, our robust and low-cost microwave system provides a significant advantage for our WiMax service," Saw said.

Backhaul resources Preparing metro networks for 4G LTE backhaul Building out mobile backhaul infrastructure without overspending For telecoms expanding services, wireless backhaul gives flexibility

Microwave backhaul can be appealing in urban settings for the same reasons it is in rural areas -- namely, fiber is expensive. It typically costs $100,000 to $200,000 to trench a mile of it, and it can take three to nine months to get the necessary permits to dig, said Amir Zoufonoun, CEO of Exalt Communications Inc., a wireless backhaul solutions vendor.

"There's this huge cost differential," Jude said. "[Microwave] doesn't involve rights of way in a traditional sense. It's usually a lot more cost-effective to put in a link through microwave."

Cost and logistics of trenching fiber in urban markets can be prohibitive

In some urban areas, zoning barriers can delay a project even longer. For instance, San Francisco zoning laws allow a site to be dug into only once per year, Zoufonoun said. If the local water utility already installed a new main this year, a wireless operator is out of luck. In other densely-populated cities, ripping up main arteries just isn't an option logistically.

"It's one thing to dig fiber out (in the suburbs). It's another thing to dig fiber out across Lexington Avenue in downtown New York," said Greg Friesen, director of product management for DragonWave Inc., an Ottawa-based microwave wireless backhaul solutions vendor. "In a lot of those metro areas, we're seeing it's impossible to get any additional bandwidth there."

In many cities, tier-one telecoms have already installed fiber rings, according to Emmy Johnson, founder and principal analyst of Sky Light Research. But those rings aren't always the best solution for small and midsized wireless operators.

"It really depends on the capacity of those fiber rings, what they're being used for and where your mobile towers are," she said. "If there's not the capacity that you need going to that cell tower … you need to either trench more (fiber) or do something different, and that's where microwave makes a lot of sense."

Fiber optics networks still reign as best choice for 4G data traffic

Despite microwave's reach, even its proponents acknowledge fiber is still king, able to deliver anywhere from 10 to 100 times more than the capacity of microwave backhaul.

"If there's fiber … then you should go ahead and user the fiber or the OC3 or whatever pipe is already trenched," Johnson said.

Microwave backhaul might be a good choice for a wireless operator just entering a market or looking to supplement its edge of network coverage, but it may be a questionable choice as a long-term urban strategy.

"Ultimately, fiber is the preferable option simply because you can support practically infinite data rates," said Jude, of Frost & Sullivan. "You have to use good network planning, and that's especially important as we have evolved from 3G to 4G because … if you have a particular cell site and you're feeding 3G or 4G access that has a fairly high data rate, it's pretty easy to saturate your backhaul if you have a significant number of subscribers."

Jude said wireless operators should be cautious of the sensitivity a microwave backhaul network has in an urban setting. A low-flying bird, a new building or wild weather could hinder network performance.

Vendors have introduced products that expand the capacity and reduce the costs of microwave wireless backhaul in order to make it more attractive despite its limitations.

DragonWave recently launched Horizon Quantum, a link that can deploy 4 Gbps in half the rack space required by the company's previous model, which maxed out at 1.6 Gbps.

Exalt also recently unveiled ExtendAir, a $5,000-per-link-line of point-to-point radios that can support 120 Mbps over 10 miles but can cover as much as a 30-mile range. Other lines cost as much as $40,000 per link and support 400-plus Mbps.

"Fiber's been able to deliver more than microwave," said DragonWave's Friesen. "We think we've now taken and expanded the applications base of microwave into the realm of fiber."

Click here for part two: Copper, T1s not backhaul options for 4G wireless operators

Let us know what you think about the story; email: Jessica Scarpati, News Writer

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