In recent years, non?orthogonal multiple access (NOMA) has attracted a lot of attention as a novel and promising power?domain user multiplexing scheme for Long?Term Evolution (LTE) enhancement and 5G. NOMA is able to contribute to the improvement of the tradeoff between system capacity and user fairness (i.e., cell?edge user experience). This improvement becomes in particular emphasized in a cellular system where the channel conditions vary significantly among users due to the near?far effect. In this article, we provide an overview of the concept, design and performance of NOMA. In addition, we review the potential benefits and issues of NOMA over orthogonal multiple access (OMA) such as orthogonal frequency division multiple access (OFDMA) adopted by LTE, and the status of 3GPP standardization related to NOMA.
multiple access; non?orthogonal multiple access (NOMA); power?domain; multi?user detection; MUST