A sensing efficiency optimization scheme based on two-stage spectrum sensing that maximizes the achievable throughput of the secondary network and minimizes the average sensing time is proposed in this paper. A selection method for the threshold is proposed and proved to ensure optimal sensing performance. An effective iterative algorithm is presented to solve the constructed efficiency optimization problem.

This letter proposes a new asymmetric watermarking scheme. In the proposed scheme, a non-full rank matrix is applied to an embedded watermark to form an asymmetric detection watermark. To detect the embedded watermark, the watermarked signal is transformed through the matrix firstly. Then a correlation test between the detection watermark and the transformed signal is performed. This scheme allows for the public release of all information, except for the embedded watermark. The performance of the scheme is analyzed, and the simulation results demonstrate that the proposed scheme is secure and robust to some common attacks.