Diversity-Multiplexing Tradeoff in Selective Cooperation for Cognitive Radio
In this paper, the authors first explore a selective cooperation framework for secondary user transmissions in a cognitive radio network with single relay. In the selective cooperation framework, two transmission modes (i.e., relay diversity transmission and non-relay direct transmission) are considered. They study two specific selective cooperation schemes with and without an ACKnowledgement (ACK) from a cognitive destination as to if it succeeds in decoding or not, called ACK and non-ACK based selective cooperation, respectively. They derive closed-form outage probability expressions for the two schemes with imperfect spectrum sensing, showing that an outage probability floor occurs in high Signal-to-Noise Ratio (SNR) regions due to mutual interference between primary and secondary users.