One of the main requirements of cognitive radio (CR) systems is the ability to reliably detect the presence of licensed primary users. After determining the availability of the licensed spectrum bands, CR users must select appropriate transmission parameters to better utilize these bands and avoid possible interference to the licensed users. This dissertation focuses on two main objectives. First, we address the temporal centralized cooperative spectrum sensing under correlated lognormal shadowing. Formulating the spectrum sensing problem as a Gauss- Gauss hypothesis test, we derive the optimal detector under Bayesian criterion. We calculate the upper and lower Bhattacharyya bounds and in this way we investigate the effect of the number of CR users and their correlation on the error performance of spectrum sensing. Second, we address the problem of joint sensing and resource allocation with the goal of energy consumption minimization in code-division multiple access (CDMA)-based and orthogonal frequency-division multiple access (OFDMA)-based CR networks. In addition, we study the separate optimization problem in which the sensing parameters are determined regardless of the allocated resources. The comparison between the joint and separate optimization shows more clearly the benefits of the joint optimization method for energy saving. Key Words Cognitive Radio, Cooperative spectrum sensing, Resource Allocation, Energy Efficiency.
