Maximum throughput of a cooperative energy harvesting cognitive radio user

In this paper, we investigate the maximum throughput of a saturated rechargeable secondary user (SU) sharing the spectrum with a primary user (PU). The SU harvests energy packets (tokens) from the environment with a certain harvesting rate. All transmitters are assumed to have data buffers. In addition to its own traffic buffer, the SU has a buffer for storing the admitted primary packets for relaying; and a buffer for storing the energy tokens harvested from the environment. We propose a new cooperative cognitive relaying protocol that allows the SU to relay a fraction of the undelivered primary packets. We consider an interference channel model (or a multi-packet reception (MPR) channel model), where concurrent transmissions can survive with certain probability characterized by the complement of channel outages. The proposed protocol exploits the primary queue burstiness and receivers´ MPR capability. In addition, it efficiently expends the secondary energy tokens. Our numerical results show the benefits of cooperation, receivers´ MPR capability, and secondary energy queue arrival rate on the system performance from a network layer standpoint.