Abstract
Underlay cognitive radio allows simultaneous primary and secondary transmissions over the same band given that the secondary interference is below an acceptable level. This paper proposes an interference alignment (IA) based joint optimization design for the single secondary transceiver. To regulate the secondary interference on the primary receiver and maximize the secondary rate, the precoding and power allocation matrices are jointly optimized in both perfect and imperfect channel knowledge. Numerical results show that the proposed methods are able to protect the licensed user and support higher secondary rates due to the interference allowance on the primary receiver.