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Clearwire leans heavily on wireless to backhaul WiMax network

According to CTO, 90% of all cell sites are linked by IP radios with fiber used primarily as an aggregation tool

Clearwire (NASDAQ:CLWR) isn’t just relying heavily on point-to-point wireless links to backhaul its WiMax, it’s using it almost exclusively. Faced with the need for high-capacity links to each cell site and the frustrating lack of fiber serving those sites, Clearwire has built its backhaul transport network almost exclusively with IP radios for DragonWave (TSE:DWI), Motorola (NYSE:MOT) and other vendors, according to new chief technology officer John Saw.

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Saw said that 90% of Clearwire’s cell sites are connected via wireless backhaul links, providing 30 Mb/s or greater capacity—bandwidth that would require the provisioning of 20 T1 lines or more to achieve via standard copper connections. While incumbent wireline operators are making greater strides in extending fiber and Ethernet to the tower to support coming 4G networks, the pace isn’t fast enough, Saw said. Clearwire is deploying a full-fledged 4G network today, the demands on which will only increase dramatically in the future, Saw said. The typical cell site runs three sectors, each carrying an average payload of 10 Mb/s, which is by no means their limit. As Clearwire signs up more customers and individual customers start consuming more data, the backhaul network needs to support more capacity on those current sectors as well as deploy new ones, Saw said.

“We see demand at each site easily going up to 100 Mb/s,” Saw said. “30 Mb/s is not enough. It’s just enough to get started.”

Clearwire isn’t shunning fiber entirely, though. It actually provisions links from a long list of providers including Level 3 Communications (NASDAQ: LVLT) and incumbents AT&T (NYSE:T) and Verizon Communications (NYSE:VZ). It also works closely with its investors Sprint (NYSE:S), Comcast (NASDAQ:CMCSA) and Time Warner Cable (NYSE:TWC).  At the 10% of its sites where fiber is available and relatively inexpensive, Clearwire uses the resource due to its reliability and the fact it doesn’t face the line-of-site issues of wireless. Clearwire also uses fiber at most of its aggregation points, which are much easier to map onto the fiber footprints of wireline operators and can handle the enormous capacity demands of multiple cell sites funneled into the same pipe, Saw said.

Because of the huge fiber builds before the turn of the millennium, Clearwire has little trouble reasonably priced fiber links in the major markets for its core and transport networks. But Clearwire isn’t just building in the big markets. Of the 25 markets it plans to launch this year, more than half will be in smaller markets like Midland-Odessa, Texas, or Bellingham, Wash., where the fiber glut never materialized.

“In West Texas, the fiber prices are either two expensive because there are only one or two providers, or there is just no fiber,” Saw said. “There we are running wireless for transport for long distances.”

That’s why Saw is encouraged by new high-capacity backhaul radios that are emerging in the market. Today, Clearwire supplier DragonWave unveiled a new backhaul system capable of supporting a 4 Gb/s link using dual polarized radios. The radio isn’t yet commercial, so Clearwire has yet to trial it, much less commit to deploying yet, but Saw said supercharged radios like DragonWave’s new Horizon Quantum will be ideal for Clearwire’s networks in the future. 4 Gb/s might seem excessive for a cell site link, but in low-fiber-penetration areas Clearwire will eventually have to move wireless further into the network core, where such capacity will be critical.

Considering Clearwire owns its own backhaul network, it could find itself in a unique position to supply transport for other operators. Not only is Clearwire putting in high-capacity links, it’s implementing a next-generation Ethernet transport architecture using Ciena (NASDAQ:CIEN) gear, which would be ideal for transporting the cellular operators’ ever-increasing loads of 3G and eventually 4G data traffic. Saw said Clearwire is focused on building its own network now, not on becoming a backhaul link supplier, but he admitted it was a thought that had occurred to him.

“We’re at cell sites where we several other carriers all adding more and more T1s, while we’re running a wireless link,” Saw said.

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© 2014 Penton Media Inc.

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