Resource Allocation in Cooperative NOMA: Opportunities and Challenges

The radio access technology keeps users connected to communication networks anywhere and anytime in Fifth Generation and beyond wireless communication systems (b5G). Future radio access technologies incorporate major wireless communication system parameters, like huge data rates, massive connectivity, high energy efficiency, very low latency, etc. Hence, there is a need to bring revolutionary changes in the present radio access technologies (RATs). The employment of 5G and beyond technologies aim to provide better throughput, lower latency, excellent user connectivity and quality of service, and reliability. Non-orthogonal multiple access (NOMA) techniques are employed to allow users to share the same time-frequency blocks. NOMA can support huge data rates, massive connectivity and promises user fairness. The user capacity of NOMA can be enhanced by integrating it with the cooperative relay networks, that provide enhanced spectral efficiency, energy efficiency and user connectivity. This article presents the detailed review of resource allocation techniques in Cooperative NOMA (CNOMA) with discussion about the challenges in implementing CNOMA in multi-user communications system.