Joint power control and relay design in underlay cognitive networks with multiple transmitter-receiver pairs

We consider an underlay cognitive network with L transmitter-receiver pairs and K relays in a two-hop half-duplex cooperative scheme. While the transmitters use a shared channel to transmit to the relays, the relays use either a shared channel or L orthogonal channels to communicate with the L receivers. For both second-hop-channel cases, we jointly determine the transmitters´ powers and the relaying weights that maximize the worst signal-to-interference-plus-noise ratio subject to the transmitters´ total and individual and the relays´ total power constraints while guaranteeing that the interference powers on M existing primary users are below some required thresholds.