5G Network Architecture: Being Built Like Lego Blocks

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China is now in the 3G and 4G era and, at the current rate of progress, will be in the 5G era by 2020. 5G means everything in the digital world will be more interconnected including man-to-man, man-to-machine, and machine-to-machine communications. 5G era communications will feature dramatically improved network performance, such as 10 Gbps throughput, 1 ms delay and over one million connections. Moreover, it will feature in-depth convergence with diverse vertical industries, enabling a wealth of new applications, such as high-speed railway, the intelligent car, remote telecom-operation, virtual and augmented reality.

In the 5G era, many use cases and customer-oriented businesses will be supported. A 5G network will be quickly set up and modified with higher performance than previous generations. This presents a major challenge for existing ‘legacy’ mobile network architecture.

A legacy network is function oriented with dedicated hardware used for RAN and core functions, and circuit and packet switching processed separately. However, a 5G network will be a unified, service-oriented, flexible telecom platform that can support an abundance of applications such as iOS or Android in smartphones. The top of the platform enables diverse applications through simple development and adaption.

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The three-layer network architecture proposed by The Next Generation Mobile Networks (NGMN) Alliance has been accepted in the telecom industry as the de facto model. At the bottom of the architecture is the infrastructure resource layer that includes access nodes, cloud nodes and networking nodes (Fig. 1). This layer virtualises physical resources. In the middle of the architecture is the business enablement layer, which provides a common information repository and a library of network functions such as the control plan, user plan, state information, and radio access technology (RAT) configuration. At the top of the architecture is the business application layer, which can deliver a variety of services to operators, enterprises and even over-the-top (OTT) and third party players. These three layers can be managed end-to-end and can be dynamically orchestrated by the management and orchestration technologies.

ZTE’s 5G network architecture is consistent with NGMN’s initiative. The future 5G network will be a software-defined network (SDN) that includes the following four key characteristics (see Fig 2):

  1. Software-defined infrastructure (SDI)
  2. Software-defined network function (SDNF)
  3. Software-defined network slice (SDNS)
  4. Software-defined service interface (SDSI)

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Software-defined infrastructure (SDI)

The SDI corresponds to the infrastructure resource layer of NGMN. Legacy hardware elements such as radio access networks (RAN) and the core are redefined. All other hardware resources except dedicated hardware are virtualised.

These resources are uniformly managed and scheduled so that on-demand virtual resources can be provided to the upper layer. The SDI concept is similar to infrastructure-as-a-service (IaaS) as part of an IT ecosystem. The infrastructure resource layer is separated into the physical domain and the virtualisation domain (Fig. 3).

The physical domain provides physical resource nodes, including the access node, computing node, networking node, and storage node. On top of the physical resource nodes is a virtualisation layer built using the open-source software platform for OpenStack cloud computing which provides virtualised resources to the upper layers.

The virtual infrastructure management (VIM) on the right side manages resources in a unified way and provides IaaS interfaces. VIM also manages dedicated hardware to enhance telecom service performance such as user data forwarding, encryption and decryption.

Software-defined network function (SDNF)

The SDNF is the business enablement layer of NGMN, providing common functions and business components. The SDNF concept is similar to platform-as-a-service (PaaS) as part of an IT ecosystem. An execution environment is needed for telecom cloud. Common services such as communication, load balancing, monitoring and databases are embedded in the execution environment (Fig. 4).

On top of these services, a network function blueprint repository is provided. The network function blueprint is a file that describes how components are composed in order to form a network function. The network function blueprint does not really work in the data centre but is a configuration to describe how components are orchestrated similar to an app in the app store.

The management system assembles and orchestrates these components, involving service topology management, orchestration management, and service lifecycle management.

Software-defined network slice (SDNS)

The SDNS corresponds to the business application layer of NGMN. SDNS can provide different network slices to meet application requirements. Similar to a network function blueprint, a slice blueprint is a description file composed of a number of network functions for end-to-end applications. Slice instances are running programs that can implement specific applications, such as smartphone games downloaded from the app store.

Figure 5 shows the business application layer. SS

The small hexagonal block in Fig. 5 is a network function. Blocks 1, 3 and 4 are used in both slices A and B, but their properties differ. Block 1 is a shared network function (also called a multiple instance). Blocks 3 and 4 have a different copy in terms of instance. The fact that block 1 is shared demonstrates that there may be dedicated hardware that cannot be split, or that the same virtual resource must be used, such as the air interface.

The red, blue and yellow ellipses indicate the slices after instantiation. These slices are programs that run in the network. The red and yellow ones are instantiated by slice A and provide the same type of applications for different users, such as vehicle to vehicle (V2V) to vehicle companies. The blue ellipses is instantiated by slice B and can provide another type of service such as IoT.

Software-defined service interface (SDSI)

The SDSI provides open application program interfaces such as IaaS, PaaS and NaaS interfaces, as well as some user data and operating data. All this data can be delivered to a variety of vertical industries.

Based on the three-layer network architecture, a new functional module or a specific slice can be created without affecting other existing modules or slices. ZTE’s new 5G architecture is built on virtual, componentised, independent modules, like Lego building blocks, and can be flexibly adapted to various businesses and industries to meet the challenges of the new era.