Cooperative Relaying to Improve the Spectrum Utilization of Multi-channel CR Networks
Cognitive radio (CR) allows unlicensed users to dynamically access the underutilized frequency bands of licensed primary users, to improve the spectrum utilization. Because of the scarcity of the radio spectrum, improving utilization of the spectrum is the primary design goal of CR systems. In this paper, we employ cooperative relaying to improve the spectrum utilization. Conventionally, cooperative relaying is used to achieve a diversity gain at the cost of spectral efficiency. In the proposed scheme, the relay node uses the spectrum that is not available for the source-to-destination direct link. Hence, it improves spectrum utilization in addition to diversity gain. To achieve diversity gain along with coding gain, we use a coded diversity that transmits incremental redundancy through relay. Tight upper bounds for bit error rate and frame error rate of the proposed scheme are also derived. Analysis and simulation results show that the proposed scheme achieves full diversity, along with improved utilization of the spectrum.
cooperative relaying spectrum utilization cognitive radio coded diversity fading channel