Advanced Multiple‐access and MIMO Techniques

In this chapter, we present advanced schemes for the evolution of multiple access and MIMO. In particular, non‐orthogonal multiple access (NOMA) and smart vertical MIMO (SV‐MIMO) are introduced as new advanced interference management and MIMO schemes to enable future enhancements of spectrum efficiency. Both schemes aim to improve spectrum utilization efficiency without the need to install new antenna equipment. NOMA superposes multiple users in the power domain and exploits the channel‐gain differences among multiplexed users, while SV‐MIMO performs 3D MIMO transmission using antenna elements that are adaptively grouped vertically according to the type of signal or channel quality at the receiving mobile terminal. Regarding NOMA, we present our design concept and its performance gains over traditional OFDMA. Regarding SV‐MIMO, we describe the characteristics of adaptive mode selection, system‐level simulation results, and our experimental results, and compare its performance gains over conventional systems without adaptive antenna grouping.