Power-Domain Non-Orthogonal Multiple Access (NOMA) in 5G Systems: Potentials and Challenges

TLDR

Non‑orthogonal multiple access (NOMA) is a promising radio access technique that offers greater spectrum efficiency than OFDMA, with power‑domain and code‑domain variants capable of meeting 5G data‑rate requirements. This paper surveys recent progress of power‑domain NOMA in 5G systems, reviewing capacity analysis, power‑allocation strategies, user‑fairness, and user‑pairing schemes. It examines power‑domain NOMA using superposition coding at the transmitter and successive interference cancellation at the receiver, and discusses its integration with cooperative communications, MIMO, beamforming, space‑time coding, and network coding. The paper identifies key implementation challenges of NOMA and outlines potential directions for future research.

Abstract

Non-orthogonal multiple access (NOMA) is one of the promising radio access techniques for performance enhancement in next-generation cellular communications. Compared to orthogonal frequency division multiple access (OFDMA), which is a well-known high-capacity orthogonal multiple access (OMA) technique, NOMA offers a set of desirable benefits, including greater spectrum efficiency. There are different types of NOMA techniques, including power-domain and code-domain. This paper primarily focuses on power-domain NOMA that utilizes superposition coding (SC) at the transmitter and successive interference cancellation (SIC) at the receiver. Various researchers have demonstrated that NOMA can be used effectively to meet both network-level and user-experienced data rate requirements of fifth-generation (5G) technologies. From that perspective, this paper comprehensively surveys the recent progress of NOMA in 5G systems, reviewing the state-of-the-art capacity analysis, power allocation strategies, user fairness, and user-pairing schemes in NOMA. In addition, this paper discusses how NOMA performs when it is integrated with various proven wireless communications techniques, such as cooperative communications, multiple input multiple output (MIMO), beamforming, space time coding, and network coding, among others. Furthermore, this paper discusses several important issues on NOMA implementation and provides some avenues for future research.