Since the commercial launch of 4G, imaginations have run wild in the industry about the next generation of mobile communications technology. The future technology must be able to provide super-fast peak data rates, support massive connections, have a very short latency, and use frequency bands above 6-GHz. This vague outline of 5G has been made clearer through the joint efforts of telecoms operators, manufacturers and research institutes. Today, it is clear that the era of 5G is approaching.
The diverse expectations of 5G vision have been converged. The 5G user case has been divided into three typical scenarios – enhanced mobile broadband (eMBB), massive machine type communications (mMTC), and ultra-reliable low latency communications (URLLC). KPIs relating to each scenario have also been thoroughly discussed and accepted by major players in the industry. In order to achieve the anticipated 5G KPIs, many new technologies have been proposed. The following are some of these key technologies that have been gradually accepted in the industry and will play important roles in 5G standards.
Massive MIMO has contributed much to 4G LTE and will contribute more to 5G, especially in high-frequency communication systems. The core of a high-frequency communication system is to use the beams formed by multiple antennas at the sending and receiving sides to resist against high propagation loss of high-frequency signals. The concept of beams is also used in low frequencies to further improve coverage and capacity.
Lean design is vital for network efficiency and forward compatibility. Its principle is to send few signals that are not directly associated with user data distribution. Such design is applicable not only to common macro coverage but also to scenarios with dense node deployments or a variety of services. The lean design allows the nodes that are not transmitting data to quickly enter a state of deep dormancy, so that power can be saved. Moreover, these dormant nodes can also reduce interference to their neighboring nodes.
Separation of user and control
Control here refers to some system information, for example, the system information that a UE needs to access a network. User and control may have different scalable design, if they are separated. Generally, user data should be supported by densely-deployed transmission nodes, while control should be supported by a wide coverage. The separation of user and control can be extended to different frequency bands and RATs. For example, user data is carried over 5G high frequency bands, while control information is transmitted on low-frequency LTE bands. The separation of user and control also makes it easy to transmit beam-based 5G user data in future.
A D2D communication function with certain restrictions has been introduced in LTE. At the beginning of 5G design, D2D communication was considered as a part of the whole wireless communication solution rather than an independent solution. In addition to direct UE-to-UE communication, 5G D2D communication also involves using a UE as a relay to extend network coverage. To avoid uncontrollable interference, 5G D2D communication should be defined under the overall control of a network, especially under the licensed spectrum.
Unified design of backhaul and access
Wireless technologies have been applied to backhaul usually for high-frequency millimeter waves in fixed point-to-point line of sight (LOS) environment. In the 5G era, high-frequency millimeter waves will also be used for access links (base stations and terminals). When transmission points are densely deployed and have low power, radio backhaul should be expanded to the non-line of sight (NLOS) environment as access links. Radio access links and backhaul links, therefore, cannot be considered as two independent links in the 5G era. This is why the unified design of backhaul and access is proposed, in which the same infrastructure and techniques are used to enhance spectrum utilization and reduce O&M costs.
As 5G technologies have gradually been established, global telecoms operators and regulators are stepping up their 5G preparation work. 5G network infrastructure is viewed as the cornerstone of future network society and also an excellent opportunity to push traditional industries into the digital age. Governments worldwide have all been gearing up and investing heavily in research into 5G and 5G-based new applications.
In July 2016, the US government released an Advanced Wireless Research Initiative (AWRI), claiming that it would invest $400 million in four cities to build 5G platform trials in the next seven years. The IMT-2020 (5G) Promotion Group initiated by the Chinese government has directed China’s national 5G tests and attracted the participation of major mobile equipment vendors worldwide. The European Union has launched the 5G-PPP project to maintain its leadership in the future mobile communication industry. In 2014, South Korea announced a plan dubbed “Creative 5G Mobile Strategy” that would inject 1.6 trillion won through 2020 with local firms to build the country as 5G market activator, 5G technology leader, and 5G standard innovator. To support the 2020 Tokyo Summer Olympics, the Japanese Ministry of Internal Affairs and Communications (MIC) has made its radio policy drafts toward 2020 to encourage the 5G research.
ZTE has been devoted to developing 5G. The company has proposed multiple 5G candidate key technologies. Among them is multi-user shared access (MUSA) that supports grant-free transmission and can significantly increase the number of connections supported by the system. ZTE has creatively applied massive MIMO technology into the 4G network in advance, and has successfully rolled out Pre5G commercial products for operators worldwide. At the ITU-R WP5D#25 meeting in October 2016, ZTE was recognized by the ITU Expert Group for its 5G high-frequency hybrid channel model based on the 3D digital map. The channel model has been included in the framework of IMT-2020 (5G) technical evaluation report.
In addition to researching 5G standards and key technologies, ZTE has also invested heavily in developing different kinds of 5G prototypes, and has cooperated with operators and regulatory authorities to carry out a variety of related tests. In September 2016, ZTE was the first to complete the phase 1 testing of key 5G technologies organized by the Chinese Ministry of Industry and Information Technology. The tests verified performance of multiple ZTE’s key 5G technologies including massive MIMO, 5G high-frequency communications, MUSA&MUST, and 5G network architecture.
With the joint effort of industrial players, 5G preparation work is carrying through smoothly. The 5G technical architecture is taking shape, its standardization is speeding up, and 5G prototypes are closer for commercial readiness. Looking into future, 5G is not just a simple substitute for next-generation mobile communications, but an enabler of innovations on which an abundance of new services will be developed. With more than 30 years of development, mobile communications have greatly changed people’s daily life. With the advent of 5G, bigger changes will be taking place in the future.
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