Cognitive Radio Networks and Dynamic Spectrum Access
This chapter focuses on the cooperative dynamic spectrum access in cognitive radio networks. It utilizes multiple-input/multiple-output (MIMO) systems and the emerging cooperative communications to enhance the dynamic spectrum access process. MIMO techniques refer to a family of techniques wherein multiple antennas are used to enhance system capacity and to mitigate channel impairments. There is a multiplicity of spectrum sensing methods proposed in the literature, each assuming some level of prior knowledge about the primary user’s signal. The most commonly studied methods are energy detection, cyclostationarity detection, covariance detection, and others, such as matched filters. The main advantage of cognitive relay networks is achieving seamless transmission if there is a continuous set of available spectrum bands between the source and the destination. In the cognitive relay networks, each relay node uses at most two of the available spectrum bands to receive and then relay the message one step to the destination.