Frameworks of non-orthogonal multiple access techniques in cognitive radio communication systems

Recently, the increasing demand of radio spectrum for the next generation communication systems due to the explosive growth of applications appetite for band-widths has led to the problem of spectrum scarcity. The potential approaches among the proposed solutions to resolve this issue are well explored cognitive radio (CR) technology and recently introduced non-orthogonal multiple access (NOMA) techniques. Both the techniques are employed for efficient spectrum utilization and assure the significant improvement in the spectral efficiency. Further, the significant improvement in spectral efficiency can be achieved by combining both the techniques. Since the CR is well-explored technique as compared to that of the NOMA in the field of communication, therefore it is worth and wise to implement this technique over the CR. In this article, we have presented the frameworks of NOMA implementation over CR as well as the feasibility of proposed frameworks. Further, the differences between proposed CR-NOMA and conventional CR frameworks are discussed. Finally, the potential issues regarding the implementation of CR-NOMA are explored.