Selectively triggered cooperative sensing in cognitive radio networks

In cognitive radio networks, spectrum sensing is critical to the discovery of spectrum opportunities for secondary systems. To enhance the accuracy of spectrum sensing, cooperative sensing has been considered, but it incurs communication overhead as well as more energy consumption of secondary users. To alleviate these problems while taking advantage of cooperative sensing, the authors propose a two-step spectrum sensing scheme, where only one or a few selected sensors are involved in the first step, but the second step occurs for cooperative sensing when the outcome of the first step is uncertain to make a decision in the presence of primary users. For this, there are two thresholds for measured energy in the first step; if the sensed energy by the designated sensor in the first step is between these thresholds, the second step incurs cooperative sensing of all the other sensors; otherwise, the second step is not triggered. This way, they can enhance the probability of detection and reduce consumed energy as well as communication overhead while maintaining a reasonable sensing time. The authors´ analysis and simulation results confirm that their proposed selectively triggered cooperative sensing with two steps outperforms the conventional schemes.