Beamforming and temporal power optimisation for an overlay cognitive radio relay network

The authors consider co-existence of a secondary network with a primary network under an overlay framework and propose beamformer design and power allocation using an iterative optimisation technique. The secondary network serves multiple users in the same frequency band as of the primary network; however, in order to compensate the interference leakage to the primary user terminals, the secondary network acts as a relay to forward the primary user signals. The interference and noise level at the primary terminals during various time slots are different; therefore the primary network needs to allocate resources asymmetrically during various time slots for the optimal performance. Hence, the authors have proposed a joint spatial and temporal resource allocation technique to enhance the overall system power saving while satisfying the data rate or the signal-to-interference plus noise ratio requirement of the primary and secondary users.