Analysis of non-orthogonal multiple access for 5G

The major challenge faced by the fifth generation (5G) mobile network is higher spectral efficiency and massive connectivity, i.e., the target spectrum efficiency is 3 times over 4G, and the target connection density is one million devices per square kilometer. These requirements are difficult to be satisfied with orthogonal multiple access (OMA) schemes. Non-orthogonal multiple access (NOMA) has thus been proposed as a promising candidate to address some of the challenges for 5G. In this paper, a comprehensive survey of different candidate NOMA schemes for 5G is presented, where the usage scenarios of 5G and the application requirements for NOMA are firstly discussed. A general framework of NOMA scheme is established and the features of typical NOMA schemes are analyzed and compared. We focus on the recent progress and challenge of NOMA in standardization of international telecommunication union (ITU), and 3rd generation partnership project (3GPP). In addition, prototype development and future research directions are also provided respectively.