Cooperative cognitive radio network with energy harvesting: Stability analysis

This paper investigates the maximum stable throughput of a cooperative cognitive radio system with energy harvesting Primary user (PU) and Secondary user (SU). Each PU and SU has a data queue for data storage and a battery for energy storage. These batteries harvest energy from the environment and store it for data transmission in next time slots. The SU is allowed to access the PU channel only when the PU is idle. The SU cooperates with the PU for its data transmission, getting mutual benefits for both users, such that, the PU exploits the SU power to relay a fraction of its undelivered packets, and the SU gets more opportunities to access idle time slots. To characterize the system's stable throughput region, it is noted that the queues in the system are interacting, i.e., the service process of any queue depends on the current state of the other queues, which renders the analysis intractable. To simplify the analysis, a dominant system approach is used to obtain a closed form expressions for the system's stable throughput region. Results reveal that, the non-cooperative system outperforms the cooperative system for low SU energy harvesting rate and irrespective of the PU energy harvesting rate, while the cooperation benefits are seen for high SU energy harvesting rate.