Conceptual Views and Radio Access Technologies for Future Evolution of LTE-A

摘要

This paper presents our views on the evolution concept and candidate technologies for the next steps of 3GPP LTE-Advanced (LTE-A), which are referred to as LTE-B and so on. In the future steps, we will need to ensure the sustainability of 3GPP radio access technologies in order to respond to the very challenging future requirements, including more than 500-fold increase in mobile data traffic. Taking into account the ever-increasing importance of local area (small cells) and the need for spectrum extension in particular via the efficient utilization of higher frequency bands, we propose in this paper a common evolution concept between the future steps of LTE-A. Our proposed concept emphasizes on an integrated enhancement of the radio interface of local area and wide area, and on frequency-separated deployment between wide area (mainly to provide basic coverage) and local area (mainly for high data rate transmission) as an important scenario for future enhancement of local area and efficient utilization of higher frequency bands. Furthermore, we identify potential key technologies for spectrum efficiency enhancements (e.g., 3D massive MIMO/beamforming, non-orthogonal multiple access, and dynamic TDD), and for the integration of local area with wide area assuming the frequency-separated scenario using the proposed macro-assisted small cell, named "Phantom cell", (e.g., inter-eNB CA, small cell discovery, flexible duplex support).%本稿では，3GPP LTE-Advanced (LTE-A)の次のステップとしてLTE-B等とも呼ばれる将来のLTE (Release 12以降） の発展に向けたコンセプトとキー無線アクセス技術について著者らの見解を述べる.スマートフォン等の高機能端末の急激な普及 に伴い，今後10年で500倍以上とも予測されるトラヒック量の増大に備えるため，LTE-Aの将来のステップにおいて，引き続き 3GPP 無線アクセス技術を持続的に発展しつつ，小セル化に伴ってより重要となるローカルエリアの無線アクセスの高度 化，および，さらなる広帯域化のため高い周波数帯の有効利用を考慮した新しい技術の導入を考えていく必要がある.従 つて，提案するコンセプトでは，ローカルエリアとワイドエリアの高度化を統合した無線インタフェースによって，別周 波数帯でワイドエリア（カバレッジ確保用のマクロセル）とローカルエリア（高速伝送用のスモールセル）をサポートし， ローカルエリアの高度化と高い周波数帯の有効利用の両立を目指す.さらに，周波数利用効率向上の要素技術（3D/massive MIMO/beamforming, non-orthogonal multiple access, dynamic TDD等）の適用，および，ローカルエリアとワイドエリアの統 合に有効なソリューションとして，マクロセルがスモールセルの制御プレーンをアシストするファントムセルを提案し， それを実現するための要素技術(e.g., inter-eNB CA, small cell discovery, flexible duplex support)につレ、て述べる.