A New Evaluation Criterion for Non-Orthogonal Multiple Access in 5G Software Defined Networks

In this paper, a new evaluation criterion is developed to investigate the performance of non-orthogonal multiple access (NOMA) from an information theoretic point of view. In particular, the relations among the capacity region of the broadcast channel and two rate regions achieved by NOMA and time-division multiple access (TDMA) are first illustrated. Based on these relations, a new evaluation criterion is proposed for NOMA in wireless fading scenarios, where the key idea is to compare NOMA with TDMA statistically in terms of not only the sum rate but also the individual rates. In a wireless downlink scenario with user pairing, the developed analytical results show that NOMA can outperform TDMA not only in terms of the sum rate but also in terms of each user's individual rate, particularly when the difference between the users' channels is large. The optimal power allocation for a special case of NOMA user pairing is also established.