Key techniques for 5G wireless communications： network architecture, physical layer, and MAC layer perspectives

The fourth generation （4G） mobile communication systems are offering service worldwide steadily. Although 4G systems could be loaded with much more services and data than previous systems, there is still a dramatic gap between the people＇s practical requirements and what can be offered by the 4G technologies. Consequently, the research and development for the fifth generation （5G） systems have already been started. This article presents an overview of potential network architecture and highlights several promising techniques which could be employed in the future 5G systems. These techniques include non-orthogonal multiple access （NOMA）, massive multiple input and multiple output （MIMO）, cooperative communications and network coding, full duplex （FD）, device-to-device （D2D） communications, millimeter wave communications, automated network organization, cognitive radio （CR）, and green communications. The state-of-art and implementation issue of these techniques are also addressed.