Verizon Wireless may have made a risky investment in its winning bid to capture airwaves that will be freed up when television broadcasters go digital next year, Bloomberg reported.

The company spent $9.36 billion on airwaves in three blocks, each with its own challenges. With the biggest block, bought for $4.74 billion, Verizon needs to let any type of device run on the network. Another block may have interference, and a third chunk came at an “extremely high” price, Goldman Sachs Group Inc. analyst Jason Armstrong said in a note to clients.

Verizon Wireless outbid larger rival AT&T Inc. to acquire the airwaves, which will help handle tasks such as sending video to phones. The companies, seeking to bolster growth through wireless subscriptions as customers drop home phone lines, drove up the prices in the bidding contest, while fending off competition from new entrants such Google Inc.

Verizon won enough licenses to provide wireless services in every state except Alaska, the Associated Press reported after the names of the bidders were released Thursday. Because the frequencies are subject to “open access” provisions, Verizon customers should be able to choose the phones and software they use over the network, AP said.

“They bought to protect their only really meaningful vehicle for growth right now,” said Jennifer Fritzsche, an analyst at Wachovia Securities Inc. in Chicago. “Wireless is key to their earnings.”

“The jury’s still out on what Verizon really means by opening up its network,” said Michael Nelson, an analyst at Stanford Group Co. in New York.

The most lucrative U.S. airwaves sale in history raised $19.6 billion, with more than four-fifths coming from AT&T and Verizon, the U.S. Federal Communications Commission said. Revenue from the auction, which required anonymous bids, topped government estimates of as much as $15 billion.

FCC Chairman Kevin Martin said yesterday that he had ordered an investigation into circumstances surrounding the failed auction of airwaves reserved for public safety services, the AP reported.