Cognitive Radio: Wireless gets smart

“We are suspicious of cognitive radio because of the hidden-terminal problem,” says William Webb, R&D chief at Ofcom. The terminal—a cellphone, for example—can be hidden because a building stands between it and the cognitive radio that is vying to use the same frequency. No amount of sensitivity by the cognitive radio’s receiver will uncover it. “You can use databases and network information between radios, but you can’t be 100 percent sure,” Webb says. Ofcom says it’s therefore inappropriate to introduce cognitive radios in spectrum owned by others—that is, unless the incumbents themselves decide they want to allow them.

IEEE Spectrum, Click here for article