Evolution concept and candidate technologies for future steps of LTE-A

This paper presents our views on the evolution concept and candidate technologies for future steps of 3GPP LTE-Advanced (LTE-A), which was the first major step in the continuous evolution of LTE. In the future steps of LTE-A, we will need to ensure the sustainability of 3GPP radio access technologies in order to respond to the anticipated challenging requirements in the future. Taking into account the ever-increasing importance of local area (small cells) and the need for further spectrum extension in particular, we present a common evolution concept for the future steps of LTE-A (referred to as LTE-B, C, and so on). This concept emphasizes integration of local area and wide area and focuses on frequency-separated deployment between local area and wide area as an important scenario for the efficient utilization of higher frequency bands. Furthermore, we identify key potential technologies for further spectrum efficiency enhancements, e.g., 3D/massive MIMO/beamforming, receiver interference cancellation, and dynamic TDD, and for integrating local area with wide area assuming the frequency-separated scenario using the proposed macro-assisted small cell that we refer to as a Phantom cell.