Spectrum characterization for opportunistic cognitive radio systems

Spectrum sensing is one of the most challenging problems in cognitive radio systems. The spectrum of interest needs to be characterized and unused frequencies should be identified for possible exploitation. This process, however, should be computationally simple and fast in order to catch up with the changing transmission parameters. This paper proposes a sensing method for identifying the unused spectrum- for opportunistic transmission by estimating the RF transmission parameters of primary users. The primary users are identified by matching the a priory information about their transmission characteristics to the features extracted from the received signal. The application of the proposed sensing method to WiMAX mobile stations for finding the active channels during initial network entry is also discussed as a case study.