Exploiting Multi-Antennas for Opportunistic Spectrum Sharing in Cognitive Radio Networks

For opportunistic spectrum sharing in cognitive radio (CR) networks, maximizing own transmit rate and minimizing interference powers at primary receivers are in general two conflicting goals to be accomplished by a secondary user. This paper studies this fundamental tradeoff from an information-theoretic perspective by characterizing the secondary user's channel capacity under both its own transmit-power constraint and an interference-power constraint at each primary receiver. In particular, this paper exploits multi-antennas at the secondary transmitter to balance effectively between spatial multiplexing and interference avoidance. Both optimal and suboptimal algorithms for design of the secondary user's transmit spatial spectrum are presented and their performances are compared.