In a Cognitive radio network (CRN) the priority of radio frequency spectrum is assigned between Primary User (PU) and Secondary User (SU) to improve the competence of spectrum usage. Secondary users are meant to share the vacant frequency spectrum of the primary user. Due to the high computational complexity involved in regulating the best possible secondary users through spectrum sensing, we propose a “Multiplex Relay Coded “Protocol to concurrently sense and acquire the available spectrum. The MRC protocol makes use of both Full-Duplex (FD) and Half-Duplex (HD) techniques for dynamic spectrum sharing. A cooperative full-duplex/half-duplex communication switching Scheduling based on threshold and power allotment is examined to maximize the spectrum allocation of cognitive radio networks. The full-duplex improves spectrum usage but suffers from self-interference and half-duplex is preferred when there is a congested network to overcome collision. Simulation results show the sensing detection by analyzing the Probability of Detection with Probability of False Alarm, the spectrum usage between Primary User and Secondary User thus improving spectrum efficiency.