Now & Later

Mar 15, 2001 12:00 PM, John Rockhold, News Editor

Finding a site to meet today’s needs is enough of a challenge. Soon, though, wireless carriers might want to consider if new sites will work for 3G.

Ask any carrier to identify the hardest part of site selection, and it’s a good bet zoning will be its first choice. Although no one has found a magic solution to make the zoning process easier, carriers almost have the engineering side of site selection down to a science. That’s not to say that it’s easy; rather, it’s just a matter of execution.

Bring Your Own Balloon

You need a site. What comes first? One of the first distinctions to make is whether the site is needed to improve capacity or coverage, according to Keith Radousky, Cingular executive director, engineering. For capacity sites, Cingular uses voice-channel forecasts, normally two years out, to predict when current sites will reach their limits (www.cingular.com). An area to search is then issued. From that, the carrier determines possible site locations, ranked in order of preference. Then Cingular runs models to see how the new site would relieve its stressed predecessors.

“Typically we try to make sure that the new site coming on is going to offload the existing site by 40% to 50%, so that we have plenty of room for growth on the site that we’re forecasting to congest,” Radousky said.

For sites to improve coverage, the selection process is much the same. The purpose of the site, though, may be different based on whether it’s for a cellular or a PCS network. For cellular networks, it’s a matter of filling in coverage holes. New PCS sites are generally footprint expansions into new territories.

Handoff limits are another consideration in existing markets. Carriers looking to expand coverage need to know existing sites’ reach to decide where to place a new site.

Drive-testing of the potential site may be done early, or not until a lease is in hand, depending on the carrier’s penchant for risk, said Dave Snyder, CTO for site company Crown Castle (www.crowncastle.com). Depending on whether or not a crane is needed to conduct the test, a drive-test can cost anywhere from $1,000 to $3,000, Snyder said. Carriers that expect zoning difficulties sometimes delay that expense until the acquisition is guaranteed.

During some drive-tests, the site could be taller than your crane will reach. Snyder called this the trickiest part of site selection, ultimately forcing carriers to make “an educated guess.”

“You have to use predictive models that have inherent reliability issues,” Snyder said. “Most predictive models are accurate to ±8dB. Say, I test at 150 feet, and I’m trying to predict what’s going to happen at 300 feet. I’m trying to do it with a model that has a statistical deviation greater than what that change would introduce.”

Although this presents an easy opportunity for error, Snyder said most engineers get it right because they’re conservative. If the transmitter tests well at 100 feet, they’ll assume a site at 200 feet would work well. If the test doesn’t go smoothly, then it’s time to send up a balloon for more tests.

Getting Physical

As the distance between sites diminishes, interference problems can arise. Cingular’s Radousky said that it’s better for a site to have a neighbor just above it than have one 100 yards away on the same horizontal plane.

Less breathing room also leaves the site-selection process less room for error.

“You’re getting to the point where they need to be closer and closer to X marks the spot, just because of your proximity to the next site over,” said James Watson, U.S. Cellular director of regional engineering, east (www.uscc.com). “If you’ve got two sites blocking, and you want to put a site in the middle of them, and you don’t get it right in the middle, then you’re going to offload one site but not the other.”

Another thing to watch out for is development in the area. Radousky said future buildings that could block the site would pose a nightmare. All told, though, just getting the preferred location is the hardest part of site selection.

“The No. 1 issue is the engineer getting the site where he or she wants it,” Radousky said.

3G Compatible?

As 3G gets closer, carriers have another consideration on their site-selection checklists. Options for building 3G sites include using the existing antenna system, swapping new antennas out for the old or building an entirely new site. Any of those could happen depending on the technology and the specific site. Today’s decisions, then, become all the more important for the long term.

“We don’t want to choose a site now that is going to give us trouble when we go to 3G,” Cingular’s Radousky said.

Overloading a tower is the prime mistake to avoid. If the tower is overrun with antennas, there’s no room for any additional equipment for 3G.

Although Radousky expects to leverage existing sites for 3G, others don’t agree.

More Sites Probable

Crown Castle’s Snyder said the tower company’s predictive model in the United Kingdom suggests that 3G will require a significant increase in the number of sites. Snyder added that American carriers are expecting to need more sites.

“If you take the presumption that there is a demand for high-speed mobility services, then, yes, there will have to be more sites,” he said.

Although it will be another year before carriers know the 3G-build-out model, there are things to consider now. Rooftop antennas are at such a fixed height that they won’t make the best 3G option, Snyder said. The height of antennas on towers also should be considered. If a carrier needs to go lower on a tower to improve cell density, there has to be room below.

“They would want the option to be lower on that same location or they might have to abandon that location altogether,” Snyder said. “The interference contour from a high site could make that site unusable in a 3G system.”

U.S. Cellular’s Watson said that 3G is too distant to factor in a site decision. The carrier is, however, moving to a smaller grid to meet its capacity needs.

3G on Back Burner

Site-planning strategies for 3G will come to the fore once the market decides what applications and demographics will drive 3G adoption. Today, there’s no clear-cut driver for an American carrier to build 3G services, Snyder said. Until there is one, a carrier only needs to keep 3G in the back of its mind during site selection.

“Carriers will probably want to proceed cautiously or know that they are rolling out a service that is going to have the demand that will drive the making of a high-density 3G system,” Snyder said.

A Little Help

However a carrier conducts site selection, it’s critical to get it right.

“If a site will not perform the way it was supposed to, it’s very difficult to fix unless you increase the height or actually move the site,” said Oscar Miranda, CelPlan vice president (www.celplan.com).

In addition to carriers’ engineering wisdom, vendors and tower companies often help in the hunt for sites. Specific circumstances call for certain approaches, but some carriers like to keep the testing in-house.

“The data is the same, but the ownership of the process is better when you do it internally,” said James Watson, U.S. Cellular director of regional engineering, east (www.uscc.com). “If it’s just a report on your desk, it’s not as meaningful because you didn’t see the site.” Telephia’s (www.telephia.com) network-monitoring services let carriers know how their current and new site performance compares to that of their competitors. CelPlan lets carriers plan ahead with a window of six months to one year. Carriers can input future cell sites and then observe how the overall network performs with the expansion.

Judging by their performance, carriers have kept their balance on the tightrope between success and failure.

John Oyler, Telephia president, said that engineers face complex problems from a cost perspective and in forecasting how usage will grow over time.

“Every time I see these problems, it gives me a new appreciation that my phone works at all,” he said.