A fast way to achieve optimum quiet period in cognitive network and its implementation

摘要

IEEE 802.22 wireless regional area networks standard regards base station (BS) as data fusion centre while both BS and customer premises equipments (CPEs) as secondary users (SUs). BS decides the quiet period and sends it to each CPE. Both BS and CPEs would cease transmission in the quiet period so as to detect reliably the primary user's presence. Liang et al. have studied the relation between quiet period and data throughput. It proves that optimal quiet period can be achieved when probability of false alarm is lower than 0.5, while complex computation is necessary if BS needs to find the optimum quiet period. Aiming to reduce the computation effort, we further investigate a look-up table (LUT)-based way to quickly achieve optimal quiet period corresponding to one specific signal-to-noise ratio (SNR) based on maximum ratio combination (MRC). Also, we verify that there exists an effective range of SNR to satisfy the requirement of maximum probability of false alarm, e.g., MRC-based SNR should be greater than -16.3 dB if the maximum probability of false alarm equals 0.1. Finally, to testify the performance in application, a filed programmable gate array-based simulation is performed, the result of which shows that only a delay of 30 ns is needed to output the value of the optimal quiet period after SNR is inputted, indicating its feasibility in the engineering applications.