Reliable open spectrum communications through proactive spectrum access

Open Spectrum systems offer an attractive solution to the reuse of under-utilized licensed spectrum. Existing proposals take a reactive sense-and-avoid approach to impulsively reconfigure spectrum usage without any knowledge of future dynamics. We propose a proactive spectrum access approach where secondary users utilize past observations to build predictive models on spectrum availability, and intelligently plan channel usage to maximize utilization and minimize disruptions to primary users. Based on the characteristics of TV-broadcast, we develop a simple availability metric and apply a usability filter to eliminate unreliable channels with heavy and frequent appearance of primary users. Our experimental results show that the proactive approach can significantly reduce the number of disruptions. We also observe a clear tradeoff between the disruption rate and the throughput at secondary users. By varying the usability filter threshold, we can to control this tradeoff according to the constraints of primary users and the application requirements at secondary users.