Sprint picks Canadian wireless backhaul firm for WiMAX network

When Sprint Nextel’s new WiMAX network in the U.S. makes its debut later this year it will be supported by some Canadian infrastructure.

The carrier has chosen wireless Ethernet backhaul equipment from Ottawa’s DragonWave for its first three markets in Baltimore, Washington, D.C., and Chicago, the companies announced this week.

”Landing a marquee name like Sprint is really a big deal for the company,” said Alan Solheim, DragonWave’s vice-president of product management.

The backhaul networks will start to be rolled out this month by Sprint’s new XOHM division and will be completed by the end of the year. Sprint has said its service, to be called XOHM WiMAX, will first be commercially available in Baltimore in September.

However, the deal initially only covers the three cities. Sprint has yet to chose its wireless IP backhaul provider for other cities it will expand the WiMAX network to.

The network will take advantage of a new generation of WiMAX-equipped handsets and laptops.

Backhaul has been a challenge for the WiMAX network because Sprint will need high capacity to support the fast service it’s promising, which the carrier estimates will deliver between 2Mbps (bits per second) and 4Mbps to each customer. That service will come from a WiMAX radio serving part of a city, but Sprint needs to find a way to carry the traffic of all the customers in that area to the Internet.

U.S. cellular networks are typically backhauled over T-1 lines, which deliver just 1.5Mbps. Faster leased connections such as DS-3 lines (45M bps) aren’t available at many of the sites Sprint wants to use, Sprint CTO Barry West said in April. Setting up backhaul was one of the biggest hurdles holding up commercial release of WiMAX, he said. Sprint was working on using wireless but had difficulty getting unobstructed line-of-sight paths, finding qualified engineers and dealing with zoning issues, he said.

DragonWave makes Ethernet equipment that uses point-to-point microwave links instead of cables or fibers for transmission, Solheim said. The company’s mesh technology improves upon traditional microwave backhaul so carriers and enterprises can deploy more resilient backhaul networks while paying less for antennas, he said.

Usually, microwave networks use a “hub and spoke” design of antennas, which can pose a problem if the “hub” can’t be placed exactly where the engineers want it. DragonWave’s mesh system uses a core ring of five to 10 sites which interconnect to others, Solheim said.

In a mesh of radios, if one base station fails or has to be taken offline, traffic can take a different path. This is especially important for point-to-point microwave radios because of “churn” among radios caused by problems with zoning or property-owner permissions, according to Solheim. It also allows for shorter paths between nodes, so smaller antennas can be used, he said. DragonWave claims its smaller antennas can be as much as 50 per cent less expensive to use over traditional installations.

Sprint will use a combination of DragonWave’s Horizon Compact and Horizon Duo units, for the edge and the core of networks, respectively, Solheim said. These are much fatter pipes than typical leased lines: 800M bps on one link for the Compact and 1.6G bps per link for the Duo. Multiple links can be set up on each. Rain can affect the speed of a link, but distance is not a factor in DragonWave networks, where the nodes are typically placed less than five kilometers apart, Solheim said.

Sprint struggled with wireless backhaul at first because it has traditionally used leased lines and lacked in-house expertise in this type of technology, Solheim said. DragonWave doesn’t have trouble finding qualified engineers, according to him. But he acknowledged that microwave backhaul is much more widely used outside the U.S., which he estimated is less than 10 percent of the global market for it. Relatively abundant and inexpensive T-1 lines have stifled the technology here, according to Sprint’s West.

DragonWave is one of a number of vendors Sprint is working with in its WiMAX deployment. They include FiberTower for wireless backhaul services, and Nokia and others for network infrastructure.

Sprint announced earlier this year it would form a joint venture with ClearWire to offer the WiMAX service, a deal that is still pending regulatory approval. DragonWave already provides wireless backhaul equipment to ClearWire, according to Solheim.

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