CDMA base station maker Airvana is retooling its CDMA 1X EV-DO kit to act as an air-to-ground backhaul link, enabling Wi-Fi in airplanes. The vendor is developing the technology in conjunction with Verizon Airfone, the Verizon Communications subsidiary that provides in-flight communications through seat-back phones common on major airlines.

Airvana’s technology is designed to support Verizon’s bid for 800 MHz spectrum the FCC is auctioning off for air-to-ground communications. If Verizon wins the bid, then the carrier will build a terrestrial EV-DO network that will cover airspace throughout the U.S., said Randy Battat, CEO of Airvana.

The ground link uses an optimized base station based on EV-DO revision A technology, the first 3G CDMA standard that stipulates quality of service, thus enabling VoIP. Because of the clear line of sight between the ground and aloft airplanes, the usual range restrictions for CDMA networks are easily extended from a few miles to hundreds of miles, Battat said.

“With as many [cellular] base stations as it would take to cover a moderate-sized city, you can cover the entire country,” Battat said. “The number of base stations would be in the hundreds, with which you can blanket North America.”

The basic technology remains the same--supplying downlink speeds of 2.4 Mb/s like a standard revision A network--but Airvana has had to tweak it to meet both regulatory requirements and the special situation of airplanes traveling 600 miles per hour miles above the ground, Battat said. In addition to building special radios for the band, Airvana has added filtering software that insulates the transmissions from other bands. It also had to develop software to overcome the Doppler Effect problems of fast-moving planes. When someone is using a cellphone in a vehicle that is moving toward a base station, the radio waves from the transmission compress. When the vehicle moves away from the base station the waves spread further apart. While the effect is negligible in a car on the highway, the effect is definitely felt by a plane moving at close to the speed of sound, Battat said.

The EV-DO link would provide only the backhaul link to the plane. A Wi-Fi system on the plane would provide data connections for laptop users, and the onboard Airfone voice system would be powered by VoIP, either through a wired onboard network or over Wi-Fi.