Delay and power metric in a cognitive radio system with queue and retransmission over a nakagami-m fading channel

This paper investigates the performance of a Cognitive Radio Network, emphasizing the secondary users performance. Users are modeled by a priority M/G/1 queue, in which primary users have a higher priority than secondary users. The performance of the system is evaluated by a performance metric called Power Metric. We considered that transmissions occur over a Nakagami-m channel model. Different modulation orders are analyzed and retransmissions are considered. In the first model, retransmissions are considered unlimited, ensuring the correct transmission of a packet. In the second model, a defined maximum number of retransmissions is adopted. The numerical results show that an ideal modulation order can be used to maximize the value of Power Metric, in order to optimize the performance of the system.