Cellular service 5000 feet up

AirCell has cleared some major hurdles in its efforts to reuse cellular frequencies for delivery of communications services to small aircraft and, perhaps one day, commercial airline passengers.

In June, the FCC ruled against major carriers, including AirTouch Cellular, AT&T Wireless Services, GTE Wireless and Bell Atlantic Mobile, which claim that AirCell's offering interferes with their terrestrial-based systems.

Some of those operators, such as GTE, might want AirCell to fail for competitive reasons. GTE Airfone, for example, offers ground- and satellite-based service on commercial airlines.

Because AirCell reuses cellular frequencies, those operators claim it can interfere with their terrestrial systems. Terrestrial networks reuse frequencies every several cell sites. "When you have an airplane with a transmitter seeing multiple cell sites using the same frequencies, the chance for cross-interference is extremely high," said a Verizon Wireless spokesman who was with Bell Atlantic Mobile. From the air, an airplane transmitter can see and reuse frequencies from far more cell sites than a user on the ground.

AirCell executives say its technology avoids interference. "AirCell has developed a series of techniques that, when you put them all together, it makes the probability of interfering with ground systems a few parts per million," said Jim Stinehelfer, president and CEO of AirCell. The system uses limited power, horizontal instead of vertical polarization and carefully shaped antenna patterns - all of which are designed to avoid interference with terrestrial systems or other aircraft, he said.

AirCell began experimenting with the system in 1994 with the FCC's approval, and in 1996, the company received experimental licenses to beta test the concept. At that time, several operators objected. "The FCC required us to do a series of grueling tests, which they observed," Stinehelfer said. From the "volumes of reports" generated from the tests, the FCC found that AirCell has a very low probability of interfering with ground systems, he said.

Operators continued to file objections until the most recent ruling from the FCC, which deemed all of the objections moot. AirCell likely hasn't seen the end of the battle yet, however. "We are investigating what to do next because we are still extremely concerned about interference," said the Verizon spokesman.

On the other side of the fence, 24 cellular companies support AirCell's system. These companies, including Alltel, Western Wireless, US Cellular and Rural Cellular Corp., have signed facilities-based reseller agreements with AirCell. "I don't think [the arguments of opponents] have any merit whatsoever," said Scott Donlea, vice president of market development for RCC.

As part of the relationship with these operators, AirCell places its special antennas, which are angled upward, at select base station sites. The antenna connects to ordinary cellular equipment. "We optimize it for handoffs in our environment and for low power signals," Stinehelfer said. AirCell chooses sites with a clear line of sight to aircraft and that can support another antenna.

AirCell uses four of RCC's sites, but Donlea said RCC would like to share more sites with AirCell.

"We bring extra revenue to rural sites," Stinehelfer said.

AirCell also buys airtime from its partners. From an operator perspective, that part of the relationship is shaped like a roaming deal. "To us they look like another roamer," Donlea said.

AirCell only needs about 150 operating sites to cover the U.S. It currently has about 85 operational sites and is commercially offering service. The company hopes to have about 110 sites up around early September when it will have coverage of about 90% of the U.S.

Although the service today is largely targeted to small aircraft users, AirCell believes with third generation networks, it may be able to offer service to commercial airlines.