Cognitive radio, which utilizes frequency effectively, needs a highly reliable sensing technique. Cooperative sensing techniques have been studied to meet this need. However, conventional techniques have a high false alarm rates. To solve this problem, we propose an innovative cooperative sensing technique in which the power levels at several radio stations are multiplied by different weights and added. Whether or not radio waves are present is determined based on this added power level. We used computer simulations to evaluate the proposed technique and demonstrated that it can perform at the required misdetection rate but has a lower false alarm rate than conventional techniques. We also propose an improved technique that takes account of correlated shadowing and is more effective in correlated shadowing environments.