Non-orthogonal multiple access (NOMA), as the newest member of the multiple access family, is envisioned to be an essential component of 5G mobile networks. The combination of NOMA and multi-antenna multi-input multi-output (MIMO) technologies exhibits a significant potential in improving spectral efficiency and providing better wireless services to more users. In this article, we introduce the basic concepts of MIMO-NOMA and summarize the key technical problems in MIMO-NOMA systems. Then, we explore the problem formulation, beamforming, user clustering, and power allocation of single/multi-cluster MIMO-NOMA in the literature along with their limitations. Furthermore, we point out an important issue of the stability of successive interference cancellation (SIC) that arises using achievable rates as performance metrics in practical NOMA/MIMO-NOMA systems. Finally, we discuss incorporating NOMA with massive/millimeter wave MIMO, and identify the main challenges and possible future research directions in this area.
@article{arxiv.1802.00754,
title = {Signal Processing for MIMO-NOMA: Present and Future Challenges},
author = {Yongming Huang and Cheng Zhang and Jiaheng Wang and Yindi Jing and Luxi Yang and Xiaohu You},
journal= {arXiv preprint arXiv:1802.00754},
year = {2018}
}
Comments
14 pages (single column), 4 figures. This work has been accepted by the IEEE Wireless Communications, the special issue of non-orthogonal multiple access for 5G