Non Orthogonal Multiple Access verses Orthogonal Multiple Access performance comparison in 5G communication systems

The current generation of mobile networks requires speeding up the steps to meet the future demand for high data rates, and low latency. In 5G, the Third Generation Partnership Project (3GPP) is working to support numerous users and high spectral efficiency via different technologies, such as the Non-Orthogonal Multiple Access (NOMA) scheme. This paper provides a study of NOMA and how NOMA addresses the 5G requirements, ongoing standardization efforts for NOMA, and a comparative study of NOMA with other OMA schemes like orthogonal frequency division multiple access (OFDMA). The results show improved user productivity in NOMA compared to OFDMA. We also proposed a new technique called the multi-tier hybrid NOMAOMA to get the robustness of OMA and the flexibility of NOMA to increase the spectrum efficiency and the number of users. The multi-tier facilitates the user such that to reduce the interference. We also study the impact of several tiers on the capacity, the result shows that five tiers provide the best capacity in multi-tier hybrid NOMAOMA.