Superconductors Become Cool

Companies tend to play the waiting game with new technology. It's unproven, expensive, and no one wants to be the first to try it.

So it was with superconductors and the wireless industry. Carriers had heard of the benefits, and many thought the technology had potential. But they took a wait-and-see approach.

High-temperature superconductor (HTS) companies set out to prove their technology to wireless carriers. By 1999, they were making inroads.

Dobson Cellular Systems started testing superconductors more than two years ago and arranged to deploy the units last year.

The carrier now has installed more than 100 superconductors in its network, with plans to put in at least 200 by the end of its 2-year contract.

U.S. Cellular has deployed HTS systems in its network as well.

“Initially, when they came out, they were just so expensive that you couldn't justify the cost,” said Jeff Baenke, U.S. Cellular RF engineering manager.

However, prices fell as manufacturers improved production methods. Baenke said U.S. Cellular looked at superconductors for about three years and did a variety of trials before adding them to its network.

Both Dobson and U.S. Cellular became interested in HTS technology for the range extension. By putting these units in base stations, they were able to increase the reverse-path capability of a cell site.

Dobson conducted tests at two highway sites where wireless coverage was poor.

“After deploying these units at both sites, we were able to improve the coverage to the point where (the sites) didn't drop any (calls),” said Scott Jones, Dobson national director of RF engineering.

“Range extension gets you a variety of things, some of which are hard to quantify,” Jones said. “But, certainly, there's additional minutes of use, which is revenue, and that's what we're all after.”

U.S. Cellular's Baenke agreed.

“We're able to serve the customers better by putting these in without building out a large number of cell sites,” he said.

Other Benefits

ISCO wanted to test how its technology controlled interference on CDMA networks. It partnered with Verizon and put superconductors in 37 base-station sectors surrounding Chicago's O'Hare International Airport.

“It's the heaviest traffic zone in the Verizon Midwestern network,” said George Calhoun, ISCO CEO. “We thought it was the perfect opportunity for us to really examine the effects of removing or controlling interference on a CDMA network operating under a heavy load.”

During the tests, traffic on Verizon's airport sites increased by one-third.

Conductus also sees interference control as an important factor.

“Everybody is transmitting on certain given frequencies, and signals are leaking into the wrong bands,” said Charlie Shalvoy, Conductus president & CEO.

A superconductor builds a metaphorical brick wall around a cell site and protects it from the effects of interference. This means that more calls can be completed, increasing minutes of use.

Future Implications

With all of the benefits carriers see from superconductors, what's keeping them out of every base station?

“I'm not sure why the technology isn't more deployed than it is,” Jones said, “but it's probably due to its cost.”

Superconductor manufacturers know that their wares are pricier than traditional base stations. Adding HTS systems to a network costs about $20,000 per base station, said Michael Williams, Superconductor Technologies director of marketing. Conductus charges about $50,000 to retrofit two sites.

All manufacturers are quick to point out that although this may seem like a big chunk of change, it doesn't compare to the cost of a new cell site.

If carriers can extend their range with superconductors and fill a coverage hole without building a new site, it can save them thousands, Shalvoy said. As demand goes up, costs will come down.

“It's very early in the life cycle of these units,” U.S. Cellular's Baenke said.

Jones said his company is happy with the cost-effectiveness of its superconductors.

“If you're going into an area and doing a green-field build with a brand new network, you could probably eliminate the need to build a site or two,” he said. “That saves enormous amounts of money. In mature systems, we'll deploy on an as-needed basis, looking for opportunities to get our best payback.”

Some carriers, such as Canada's Bell Mobility, are evaluating superconductors for future networks. As 2.5G and 3G networks are deployed, superconductors' filtering abilities might become more significant.

“Our brains are much more resistant to interference than computers are,” said Brian O'Shaughnessy, Bell Mobility technology vice president. “In terms of hearing a little bit of static, someone can work around it. But, if a computer loses the signal or can't make sense of a message, it's a problem.”

History Lesson

The discovery of superconductivity dates back to 1911, but it wasn't until the mid-1980s that superconductors began to look viable for a variety of industrial uses. Before that, superconductors only worked at inordinately low temperatures, 4° K, or about -452° F. That temperature can be achieved by using liquid helium, but helium is difficult to work with and expensive.

In 1986, a group of compounds was discovered that became superconductive at 77° K, about -321° F. The higher temperature could be reached using liquid nitrogen, which is much less expensive than its helium counterpart.

It was then that companies started looking at how high-temperature superconductors could be used in various industrial areas, including the emerging wireless industry.