A Novel Method for Improving the Capacity in 5G Mobile Networks Combining NOMA and OMA

Non-Orthogonal Multiple Access (NOMA) has been suggested as one of the technologies to be implemented in the fifth generation - 5G - mobile networks. NOMA helps increasing the capacity by offering a more effective use of the available resources, but it also intentionally introduces interference in the transmitted signal. This means that higher signal-to-interference-plus-noise ratio (SINR) values are required to decode the received signal, in comparison to orthogonal multiple access (OMA). Since it is unrealistic to consider a system working only with NOMA because not all the users (UEs) will meet the requirements to use this multiple access (MA) method, a hybrid MA system combining NOMA with OMA is expected. In this paper we present the performance evaluation of a hybrid MA system combined with a novel pairing algorithm based on modulation and coding scheme (MCS) adjustment and extra transmission power (Tx power) allocation. The purpose of such pairing approach is to help the NOMA UEs reach the needed SINR while improving the overall system capacity. Moreover, we use mmWave for the signal propagation to further increase the system capacity. The results show that such a system with an extra Tx power between 14% and 19% of the total Tx power for OMA, can offer the best tradeoff with a system capacity gain up to 1.78-fold for a total of 6.7 Gbps, an average 3.31-fold increase for the UEs bit rate, and a block error rate (BLER) below 10%.