Design and analysis of a DCSK-based cognitive radio system using hybrid underlay/overlay transmission

Abstract

In this paper, we present a hybrid Underlay/Overlay DCSK-based Cognitive Radio (DCR) system using the Cognitive Radio techniques and abilities of a Multi-Carrier DCSK (MC-DCSK) scheme together, which can be extended to many other similar non-coherent scenarios. In this scheme, secondary user (SU) employs the spectrum holes as a dedicated frequency to transmit reference signals in overlay mode and uses remaining common frequencies to transmit data bearing signals by an underlying approach. We derived an analytical BER expression for the DCR scheme over a frequency selective fading channel and adopted it as our optimization criterion. To formulate the optimization problem, we proposed a sub-carrier grouping approach in order to implement our min–max fairness strategy, considering the power budget and interference temperature constraints. The proposed DCR scheme not only employed spectrum holes, but also improved BER performance of the conventional multi-user MC-DCSK system significantly considering the power allocation policy and robustness against frequency selective channel. Finally, simulation results validated the advantages of the proposed scheme.