Space–Time Coding for an Energy Harvesting Cooperative Secondary Terminal

In this letter, we consider a cognitive scenario where an energy harvesting secondary user (SU) shares the channel with a primary user (PU). The SU is equipped with two antennas. It maintains a finite capacity energy queue and two infinite capacity data queues: one for storing its own data packets and the other for storing the primary undelivered data packets. The PU communicates with its destination whenever it has data at its queue head. During idle sessions of the PU, if the secondary energy queue maintains at least K packets, the SU employs the Alamouti coding scheme over two of its data packets. The optimization problem for secondary throughput maximization is stated under the stability of all queues in the network and a specific end-to-end queueing delay for the primary packets.