Power allocation for cooperative cognitive networks

We consider cooperative cognitive networks with two source-destination pairs assisted by a cognitive relay, such that one of the source-destination pair is a primary user (PU), and the other is cognitive user (CU). Two source-destination (S-D) pairs and cognitive relay share a single common channel instead of waiting for an idle channel which is traditional for a cognitive radio. The cognitive relay assists primary user and cognitive user in communicating the messages to their respective destinations. Assuming a slotted-system operating in a half-duplex mode, we propose relaying schemes using “amplify-and-forward” (AF). We examine the lower bound of achievable rate for primary user and cognitive user. We characterize the power allocation of cognitive user and cognitive relay by imposing constraints on the transmission power, so that they operate below the noise floor of primary user for not affecting the communication of the primary user. Rate of cognitive radio user can be enhanced by optimizing the power allocation of cognitive user and cognitive relay.