A Survey of Downlink Non-orthogonal Multiple Access for 5G Wireless   Communication Networks
  Non-orthogonal multiple access (NOMA) has been recognized as a promising multiple access technique for the next generation cellular communication networks. In this paper, we first discuss a simple NOMA model with two users served by a single-carrier simultaneously to illustrate its basic principles. Then, a more general model with multicarrier serving an arbitrary number of users on each subcarrier is also discussed. An overview of existing works on performance analysis, resource allocation, and multiple-input multiple-output NOMA are summarized and discussed. Furthermore, we discuss the key features of NOMA and its potential research challenges. 
Zhiqiang Wei and Jinhong Yuan and Derrick Wing Kwan Ng and Maged   Elkashlan and Zhiguo Ding
cs.IT math.IT