Cooperative Communication With Regenerative Relays for Cognitive Radio Networks

Cognitive radios hold tremendous promise for increasing spectral efficiency in wireless systems. In cognitive radio networks, secondary users equipped with frequency-agile cognitive radios communicate with one another via spectrum that is not being used by the primary, licensed users of the spectrum. The authors consider a cooperative communication scenario in which a secondary transmitter can communicate with a secondary receiver via a direct communication link or a relay channel, depending on the state of a primary transmitter. They develop a decode-and-forward transmission strategy that exploits the presence of spectrum holes both in time and in space.