Stable throughput tradeoffs in cognitive radio networks with cooperating rechargeable nodes

In this paper, we consider a cognitive radio system with a primary user and a secondary user, both powered by batteries that can recharge over time by harvesting energy from renewable sources. Both users store packets in queues for transmission. We consider a cooperation scenario where secondary user receives unsuccessful packets transmitted by primary user and relays them to primary receiver. For the system to be stable, all queues in the system should be stable. We find the stable throughput region for given system model. In battery powered transmitters, amount of energy available at a transmitter affects the activity of users, therefore affecting the stable throughput region of system. Based on the analysis of stability region, we present numerical results and study the effect of energy arrival rate as well as battery capacity on stability region and on delay of primary user packets. Finally, we compare the cooperation scheme with non-cooperation case for different energy arrival rates.