Collaborative Quickest Spectrum Sensing via Random Broadcast in Cognitive Radio Systems

Quickest detection is applied in the spectrum sensing of cognitive radio systems when multiple secondary users collaborate with limited communication time slots. When transmissions are not coordinated to avoid collisions, random broadcast is used to exchange information. A necessary condition for optimal broadcast probability, as a function of the log likelihood ratio of local observation, is obtained using variational analysis. To alleviate the difficulty of computing optimal broadcast probability, a simple threshold broadcast scheme is proposed. Simulation shows that the proposed threshold broadcast scheme can achieve substantial performance gain (less than 60% in detection delay for the same false alarm rate) over random broadcast without regulation, as well as the single-user spectrum sensing.