Network function virtualization (NFV) is the development trend of core network. The most important feature of NFV is to use the common hardware and NFVI to provide unified operation resources for all the higher-level VNFs. The NFV technology provides the basis for flexible deployment, rapid delivery, smart and automated O&M of VNFs, and network transformation. It enables the decoupling of NE software from underlying hardware so that the deployment of VNFs no longer depends on the dedicated hardware, which also makes centralized and large-scale network deployment possible. This article briefly analyzes centralized deployment of a virtualized core network shared across a big area.
The big-area centralized deployment is opposed to distributed deployment by province. In the existing telecom networks (physical equipment), each provincial branch of the operator has its independent equipment room, hardware, software, and BOSS. Resources from different provinces are mutually independent, so both hardware and software are maintained on a provincial basis. The big-area centralized deployment means that the network devices from multiple provinces are centrally deployed and maintained to provide network services to all the users in the coverage area. In general, NEs that are deployed centrally in a big-area DC include service NEs, data management NEs, control plane NEs, and latency-insensitive user plane NEs. User plane NEs are deployed on demand according to the geographical area size. If the area is small, 4G EPC user planes and 5G eMBB UPFs can be deployed centrally. If the area is large, 4G EPC user planes and 5G UPFs can be moved to edge DCs or access DCs (Fig. 1).
Issues in Big-Area Centralized Deployment
Since the big-area centralized core network deployment is significantly different from the distributed deployment in different provinces, it is necessary to make comprehensive analysis. Great attention should be paid to the following issues.
The big-area centralized deployment means that the traffic needs to be converged. The control plane traffic and user plane traffic (all or partial) need to be converged in the DCs where VNFs are centralized. It is necessary to build a new transmission network or transform the existing transmission network, especially that between wireless network and core network. Wireless networks are deployed in different provinces. Core network centralization means that the backhaul networks must be converged in the big area. The larger user base a big area has, the higher transmission bandwidth is required. In addition, along with the increase of user traffic, the demand for higher transmission bandwidth will also be increasing.
In a wireless network, services have varying QoS demands. There are latency-insensitive services (e.g. NB-IoT), latency-sensitive services (e.g. real-time gaming, voice, and real-time video), and ultra-low latency services (e.g. connected autonomous driving and industry control). Different levels of QoS should be deployed to ensure a good user experience.
It is necessary to take disaster recovery into consideration so that large-area centralized deployment have the same disaster recovery capability as the existing provincially distributed deployment mode.
It is also necessary to consider the interoperation with the existing network in each province to ensure the service continuity and promote user experience.
The large-area centralized deployment mode will coexist for a long time with the existing provincially distributed deployment mode, and a long-term plan should be made to ensure that users can be migrated smoothly from a province to a big area.
Resource Use Ratio
The resource utilization ratio could be increased by giving full play to the centralization advantage and exploiting the potential of cloudified networks.
One of the advantages of the large-area centralized deployment lies in the large-scale resource pool. Both NFVI and VNFs can centrally operated and maintained, and automation tools must be deployed to promote O&M efficiency. Technologies such as big data analysis and AI can be used to increase O&M automation levels and reduce the maintenance costs.
While core networks are centralized to support a large area, wireless networks and existing networks are still configured for different provinces. It is necessary to consider the coordination between a large area and a provincial branch, including organization structure change, division of responsibilities, fault processing flow, service development coordination, and differentiated operations.
Analysis of User Plane Deployment Forms
In the big-area core network deployment scenario, control plane NEs would normally use the NFV equipment. The deployment form of user plane NEs (such as 4G GW-U and 5G UPF) is currently one of the hot topics. The user plane deployment should take the following factors into consideration (Fig. 2).