Experimental threshold determination for secondary users using USRP and Gnu radio

Cognitive radio (CR) is an upcoming technology that provides viable solution for congested wireless spectrum. The basic idea behind cognitive radio is the utilization of unused frequency bands of primary or licensed users (PU) by secondary or unlicensed users (SU). The unused licensed spectrum is called white space or spectrum hole. CR utilizes these spectrum holes for unlicensed spectrum users. The success of CR depends on spectrum sensing efficiency. Hence, a major challenge in cognitive radio is to detect the presence of primary users in a licensed spectrum. Energy detection method is one of the methods available for spectrum sensing. The success of this method totally depends on the threshold set by the system. The threshold is used by Secondary users to know whether there is a primary user activity. In this paper, we propose a new threshold formulation by an effective iterative method for efficient spectrum sensing using energy detection method. The proposed algorithm is implemented and experimentally verified using USRP2 and Gnu radio, and even the Receiver Operating Characteristics (ROC) is compared with Matlab Simulation to check the accuracy of the algorithm. The experimental verification is done by introducing a secondary user, which makes use of the data generated from the Algorithm to check the accuracy of the data. The paper further introduces the concept of developing Look up Table (LUT) of instantaneous threshold in the form of cache which can be referred by the cognitive radio for threshold determination.