In the fifth generation (5G), the traditional restrictions that limit the capacity of wireless communication must be overcome. Non-orthogonal multiple access (NOMA) is a promising solution capable of overcoming these constraints to meet the requirements of 5G. The multiple-input multiple-output (MIMO) scheme that employs beamforming precoding technology can achieves NOMA. In this letter, we proposed non-unity beamforming precoding based on maximum signal to leakage ratio (SLR) algorithm as NOMA for multi-user MIMO (MU-MIMO) system. Then, we will compare between the proposed scheme and the classical SLR-based on beamforming precoding algorithm. This paper evaluates the symbol-detection performance for proposed and classical MU-MIMO beamforming over a Rayleigh fading channel and Rician fading channel. Simulation results show that the proposed scheme has better performance than the classical scheme. And the Rician fading channel has performance improvement until with low Rician factor value, compared to a Rayleigh channel.

Keywords - 5G, NOMA, SLR, MU-MIMO, Fading

1. F. Boccardi, R. W. Heath, A. Lozano, T. L. Marzetta, and P. Popovski, “Five disruptive technology directions for 5G,” IEEE Commun. Mag., vol. 52, no.
2, pp. 74–80, Feb. 2014.
2. Y. Saito, A. Benjebbour, Y. Kishiyama and T. Nakamura, "System-level performance evaluation of downlink non-orthogonal multiple access (NOMA),"
2013 IEEE 24th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), London, 2013, pp. 611-615.
3. NTT DOCOMO, “Requirements, candidate solutions & technology roadmap for LTE Rel-12 onward,” 3GPP RWS-120010, June 2012.
4. Y. Kishiyama, A. Benjebbour, H. Ishii, and T. Nakamura, “Evolution concept and candidate technologies for future steps of LTE-A,” IEEE ICCS2012, Nov. 2012.
5. L. Dai, B. Wang, Y. Yuan, S. Han, C.-L. I, and Z. Wang, “Nonorthogonal multiple access for 5G: Solutions, challenges, opportunities, and future
research trends,” IEEE Commun. Mag., vol. 53, no. 9, pp. 74–81, Sep. 2015.
6. F. Fang, H. Zhang, J. Cheng, and V. Leung, “Energyefficient resource allocation for downlink nonorthogonal multiple access network,” IEEE Trans. Commun., vol. 64, no. 9, pp. 3722–3732, Sep. 2016.
7. Y. Sun, D. Ng, Z. Ding, and R. Schober, “Optimal joint power and subcarrier allocation for full-duplex multicarrier non-orthogonal multiple access systems,”
IEEE Trans. Commun., vol. 65, no. 3, pp. 1077–1091, Mar. 2017.
8. Y. Saito, A. Benjebbour, Y. Kishiyama, and T. Nakamura, “Systemlevel performance evaluation of downlink non-orthogonal multiple access (NOMA),”
in Proc. IEEE Annu. Symp. Pers. Indoor Mobile Radio Commun., London, U.K., Sep. 2013, pp. 611–615.
9. Y. Saito, A. Benjebbour, Y. Kishiyama, and T. Nakamura, “Systemlevel performance evaluation of downlink non-orthogonal multiple access (NOMA),”
in Proc. IEEE Annu. Symp. Pers. Indoor Mobile Radio Commun. (PIMRC), London, U.K., Sep. 2013, pp. 611–615.
10. Z. Ding, P. Fan, and H. V. Poor, “Impact of user pairing on 5G nonorthogonal multiple access downlink transmissions,” IEEE Trans. Veh. Technol., 2016, to be published.
11. T. Cover and J. Thomas, Elements of Information Theory, 6th ed. New York, NY, USA: Wiley, 1991. 12. G. J. Foschini and M. J. Gans, ”On limits of wireless
personal communications in a fading environment when using multiple antennas,” Wireless Pers. Commun., vol. 6, pp. 311-335, March 1998.
13. Jai-Hoon Lee, Seokkwon Kim, Seung-Ri Jin and Dong-Jo Park, 2011. A Multi-User Beamforming Scheme in MIMO Downlink Channels for Multi-Cell
Networks. Consumer Electronics (ICCE), IEEE International Conference.
14. Ahlem Khlass, Thomas Bonald and Salah Eddine Elayoubi, 2014. Flow-level Modeling of Multi-User Beamforming in Mobile Networks. Modeling and
Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 12th International Symposium.
15. S. A. Jafar and A. Goldsmith, Jun. 2004. "On the capacity region of the vector fading broadcast channel with no CSIT," in Proc. IEEE ICC, Paris, Multiuser
Space-Time Block Coded MIMO System with Downlink Precoding.
16. Runhua Chen, J. G. Andews, and R. W. Health, 2004. Multiuser Space-Time Block Coded MIMO System with Downlink Precoding. Communications,IEEE
International Conference on (Volume:5 )
17. X. Shi, C. Siriteanu, S. Yoshizawa, and Y. Miyanaga, October 2011. "MIMO precoding performance for correlated and estimated Rician fading,". in Proc. 11th
Int. Symp. on Communications and Information Technologies, (ISCIT '11), Hangzhou, China, accepted.
18. A. Tarighat, M. Sadek, and A. Sayed, “A MULTI USER BEAMFORMING SCHEME FOR DOWNLINK MIMO CHANNELS BASED ON MAXIMIZING SIGNAL-TO-LEAKAGE RATIOS”. In IEEE Trans. Acoust., Speech, Signal Processing, vol.3. March 2005.
19. W. Fezali and J.G. Proakis, April, 1990. ”Adaptive SVD algorithm for covariance matrix eigenstructure computation,” in Proc. Int. Conf. Acoustics, Speech,
Signal Processing, Albuquerque, NM, vol. 5, pp. 2615- 2618.
20. A. Tarighat, M. Sadek, and A. H. Sayed, “A multiuser beamforming scheme for MIMO channels based on maximizing signal-to-leakage ratios,” in Proc. 2005
IEEE International Conference on Acoustics, Speech, and Signal Processing, pp. 1129–1132.
21. Y. S. Cho, J. Kim, W. Y. Yang, C-G. Kang. MIMOOFDM WIRELESS COMMUNICATIONS WITH MATLAB 2010
22. X Shi, C Siriteanu, S Yoshizawa and Yoshikazu Miyanaga, 2012. Realistic Rician Fading Channel based Optimal Linear MIMO Precoding Evaluation.
Communications Control and Signal Processing (ISCCSP), 5th International Symposium.
23. P. Chang, M. Tao, W. Zhang, "A new SLNR-based linear precoding for downlink multi-user multi-stream MIMO systems", IEEE Commun. Lett., vol. 14, no.
11, pp. 1008-1010, Nov. 2010.
24. E. Bjornson, M. Bengtsson, B. Ottersten, "Optimal multiuser transmit beamforming: A difficult problem with a simple solution structure", IEEE Signal Process.
Mag., vol. 31, no. 4, pp. 142-148, Jul. 2014.