Core Network Requirements and Architecture in the 5G Era

As a mobile communication system increases its bandwidth and capability, individual and enterprise mobile applications develop rapidly and social informatization accelerates its development, information communication will be the main artery maintaining normal operation of the entire social ecosystem. With ubiquitous usage and convenient access, mobile communication will no longer be confined to man-to-man communication. Instead, it will play an increasingly important role in the future information communication system, and it will be extended to all aspects of human society. Future mobile communication will evolve to be intelligent, user-centered, and elastic network oriented to full-service applications instead of simply seeking higher rate, higher bandwidth, and higher capacity air interface technologies. 5G mobile broadband systems will be full-service, multi-technology convergence network that will use ICT technological evolution and innovation to meet fast-growing requirements of all kinds of services containing a wide range of data and connections and to meet user-centered network requirements.

New Network, New Requirements
3GPP standards have entered the post-LTE era. The maturation of cloud computing technologies in the IT industry is driving mobile networks to adopt new implementation and business models. The rapid development of software-defined network (SDN) technology is also causing industry to reconsider the deployment of mobile network architecture and services.
The booms in machine-to-machine (M2M) communication, smart terminals, and mobile user base and data traffic have increased the requirement for network capacity. Smart terminals and over-the-top (OTT) providers are gaining prominence, while operators are gradually being marginalized and are becoming pipe providers. Carrier-grade telecom systems are becoming a burden, and the current network architecture cannot be easily transformed. Therefore, there is a pressing need to change system technology.
5G is a brand new wireless communication system that will serve the information society in 2020. The key 5G requirements will involve:
● requirement for user service. 5G user experience will interlace and integrate multiple terminals, rich applications, and high bandwidth. Emerging services need higher bandwidth, lower delay, higher reliability, and greater intelligence. Users need to access a 5G network anytime, anywhere. In an era the web is becoming more socially orientated, massive, high-density terminals will access the 5G network. The access-independent feature will meet 5G requirements for rich applications and terminal access abilities. Moreover, a 5G network must also be secure and reliable.
● requirement for operation service. 5G will be a huge multi-network, multi-layer, multi-domain network requiring elastic, automatic, and intelligent network operation and management. The 5G network will have large capacity, high bandwidth, high flexibility, high reliability, and low delay. Network resources will be efficiently and intelligently used in order to save energy, reduce cost, and increase revenue.
● requirement for business service. 5G will help people enter a networked society where all aspects of people’s lives are closely connected with networks. There will be many more new services and businesses. Conventional services including voice will be inherited, enhanced, and innovated. Feature-rich service patterns such as device to device (D2D), machine type communication (MTC), and virtual operation will be delivered over 5G networks. These new services can be flexibly deployed, and their content can be distributed according to user information and network status and topology. The function, performance, and intelligence for processing user traffic data will be enhanced as well.

From the perspective of industry, network capabilities will also need to be open to different participants in the industry so that they can customize their key 5G capabilities.

New Technologies, New Challenges
To meet all these requirements, ZTE has identified the following key technologies that will be possibly used in future 5G networks.

Network Functions Virtualization
NFV involves decoupling software from hardware. IT is used to reconstruct CT, and the commercial off-the-shelf (COTS) platform can be used to construct a telecom infrastructure environment in order to significantly reduce hardware infrastructure costs. Through NFV, an operator can uniformly purchase or customize NE hardware infrastructure resource and environment. This dramatically increases network agility and flexibility and shortens service deployment time. The new challenge for NFV is to combine the same functions of multiple physical NEs to optimize network architecture and the end-to-end signaling procedure.

Software-Defined Networking
SDN involves controlling networks through software and fully opening network capabilities. SDN is also a new network architecture and technology characterized by separate control and forwarding, centralized logic control, and open APIs. SDN can turn a closed vertical network architecture into a converged, open, elastic, application-focused, and horizontally layered architecture. The new challenge for SDN is to reconstruct network functions and design new interface protocols to optimize network architecture and end-to-end signaling. 

Information-Centric Network
ICN is a network that separates content from terminal location and provides named content and name-based content routing. Everything in an ICN is called information that can be interconnected and labeled by name. The role of the network is to manage flowing and caching of all information and respond quickly to requesters with the correct information. ICN is another revolution in the telecom industry. Because ICN makes an end-to-end modification of the entire network, its compatibility with existing networks is a big problem.

Big Data
Big data refers to a massive amount of data that cannot be collected, managed, and processed by simple tools in reasonable time to help enterprises make proper operating decisions. The core of big data is prediction, and its strategic significance is to professionally handle meaningful data. The challenge for big data is how to process and use the data.

5G Architecture
Considering the above-mentioned 5G requirements and new technologies, ZTE has devised a 5G network architecture that consists of five layers: hardware, virtualization, application, management, and capability opening (Fig. 1).

High-Performance and Reliable Network: Large Capacity, Low Delay, and High Reliability
Because SDN separates the control plane from the user plane, 80% of packets can be directly forwarded via the SDN forwarding layer. This facilitates local offloading, improves forwarding efficiency, shortens delay, and enhances user experience. NFV enables decoupled software and hardware so that all kinds of applications can be deployed on the COTS hardware platform. The market size of COTS devices is larger than that of telecom devices, and their computing cost per unit is far less than that of telecom devices. Moreover, COTS devices reduce costs two to three times faster than telecom devices and have faster update cycle (usually three to four years). Therefore, new IT technologies can be quickly adopted to maintain leading device performance. Hardware resources can be virtualized into multiple virtual machines (VMs), each of which can be migrated and reborn to ensure high network reliability.

Software-Based Intelligent Network: Flexible Resource Scheduling
Using virtualization that enables decoupled software and hardware as well as cloud computing that enables rapid deployment, the period of NE capacity configuration can be shortened from weeks to minutes, thereby greatly increasing flexibility in network expansion and eliminating device bottlenecks. Operators and equipment vendors can shift their focus to service innovation and create more opportunities for profit.

Automatic Distributed Network: Local Offload, Centralized O&M, and Unified Management
ICN and SDN enable data forwarding nodes to be deployed in a distributed mode. This can implement local forwarding or caching and reduce detours. A 5G network can automatically perceive virtual servers and perform the reconfiguration when the network changes its location after virtual servers are migrated and scheduled. Centralized O&M reduces costs. The 5G network also supports real-time operation of telecom NEs so that NEs and NaaS can be integrated for automatic O&M.

Open and Convergent Network: Capability Opening and Rapid Innovation
Network capability opening architecture and available big-data technology are used to completely open up the whole mobile network including hardware, software, network, applications, and data. This facilitates rapid service innovation and significantly reduces deployment time for new services.