Wireless auction concerns rise as some airwaves languish

In addition to the D block, the airwaves up for auction are divided into a "C" block, which will have to be open to any device and software application as long as the $4.7 billion minimum price on it is met.

Bids on the C block topped $3.78 billion Tuesday.

Other spectrum up for auction includes local chunks set aside in blocks designated "A" and "B." The final "E" block is considered less useful because it is limited to one-way data transmission.

The 700-megahertz signals are valuable because they can go long distances and penetrate thick walls. The airwaves are being returned by television broadcasters as they move to digital from analog signals in early 2009.

(Editing by Tim Dobbyn)