Optimization of PHY-layer sensing and Mac-layer access based on adaptive threshold schedule for opportunistic spectrum access

We consider a scenario in which the secondary users opportunistic access the spectrum allocated to the primary user if the spectrum is sensed idle. In cognitive radio network, no matter what methods the secondary users use to sense, there are always missing detection and false alarm. Missing detection and false alarm probabilities characterize the protection to the primary user and the channel utilization efficiency of the secondary users respectively. In this paper, to maximize the channel utilization efficiency, the PHY-layer sensing and Mac-layer access are investigated in opportunistic spectrum access network. In the PHY-layer sensing, we aim to minimize the total error probability caused by missing detection and false alarm. The expression of optimal threshold and sensing time is derived. To further improve the channel utilization efficiency, we propose an adaptive threshold schedule scheme based on the dynamics of the primary network. In the Mac-layer access, we adopt different access policies according to the sensing time to protect the primary user adequately. Lastly, the optimal sensing time with different channel conditions is derived. The numerical results verify the confidence of the proposed scheme and perform better, in terms of sensing performance and the measurement of channel utilization efficiency.