  Non-orthogonal multiple access (NOMA) has been widely recognized as a
promising way to scale up the number of users, enhance the spectral efficiency,
and improve the user fairness in wireless networks, by allowing more than one
user to share one wireless resource. NOMA can be flexibly combined with many
existing wireless technologies and emerging ones including multiple-input
multiple-output (MIMO), massive MIMO, millimeter wave communications, cognitive
and cooperative communications, visible light communications, physical layer
security, energy harvesting, wireless caching, and so on. Combination of NOMA
with these technologies can further increase scalability, spectral efficiency,
energy efficiency, and greenness of future communication networks. This paper
provides a comprehensive survey of the interplay between NOMA and the above
technologies. The emphasis is on how the above techniques can benefit from NOMA
and vice versa. Moreover, challenges and future research directions are
identified.
