Automated organization, multi-RAT and multi-layer heterogeneous networks are being listed in mobile of 2020, at least by the kinds of committees that brought us bluetooth 7 years late. It's the 5G era, what vendors say will be the first meaningful unified wideband mobile communication system. 

4G LTE systems, supporting up to 100Mbps data rate, at least in laboratories, have been globally deployed and are offer multimedia services like HD video, but with the mobile Internet and Internet of things (IoT) as the buzzwords for the future, current 4G systems may not satisfy the explosive growth of data, massive device connection and services and application scenarios committees probably have not thought of yet.

It is assumed that 5G systems would offer maximum 1Gbps user experienced data rate, tens of Gbps peak data rate, tens of Tbps/km2 traffic volume density, millisecond level of end-to-end latency and support 500+km/h mobility. 5G would permeate every corner of our life and build a truly user-centralized information eco-system.

The world's major developed countries and regions have already launched 5G research projects and a recent systematic overview discussed progress this research and highlighted the network architecture and techniques which might be employed in the future 5G systems. 

The new paper presents an overview of potential network architecture and highlights several promising techniques which could be employed in the future 5G systems by deeply analyzing 5G requirements and current research. 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 etc. The state-of-art and implementation issue of these techniques are also addressed.

"The quest to improve the spectral efficiency has been regarded as the most important but yet challenging task in the design of future wireless communication systems," the authors wrote in the paper. It seems that NOMA, Massive MIMO, full-duplex, and D2D communications etc. would be the sharp weapons.

 Global wireless communications would suffer from the "Spectrum crisis" and radio spectrum resource has gradually become the bottleneck of development of broadband wireless communications. There are two main ways to overcome this problem: one is to develop the millimeter wave frequency spectrum, the other is to fully utilize current spectrum resource by the cognitive radio technique.

Citation: MA Zheng, ZHANG ZhengQuan, DING ZhiGuo, FAN PingZhi, LI HengChao. Key techniques for 5G wireless communications: network architecture, physical layer, and MAC layer perspectives. SCIENCE CHINA Information Sciences, 2015, 58(4): 041301(20)