Migration Strategies for 5G Core Networks

Gabriel Brown

Operators worldwide are preparing to deploy 5G networks to improve the economics of mobile broadband and to introduce new capabilities and service types. The core network -- which controls authentication, session management, mobility, quality of service (QoS) and more -- is critical to operating 5G and to enabling advanced services, such as network slicing and converged fixed/mobile access. This makes the core network critical to a mobile operator's 5G business strategy.

For early 5G deployments, many operators are expected to deploy 5G radio access networks (RANs) in non-standalone (NSA) mode on an LTE network. The use of an LTE radio for over-the-air signaling and a 4G core network to anchor and manage sessions offers a fast, practical way to introduce 5G into commercial service. Over time, to meet new requirements, operators will introduce 5G core networks to support 5G in standalone (SA) mode. This 5G core will ultimately serve as a common core for evolved LTE (eLTE) and 5G RANs, as well as potentially for wireline and WiFi access.

To investigate this transition, I have written a new white paper entitled 5G Mobile Core Networks: Migration From NSA to SA 5G Core.

This is a complex subject with numerous potential migration options that are more, or less, attractive, according to such factors as the operator's service vision, coverage strategy and expected uptake of 5G devices. How operators will, and should, proceed is not entirely clear and is subject to revision. However, there are two leading options for the migration, summarized in the diagram below:

Migration From “5G-EPC” to 5G Core
Source: Heavy Reading
Source: Heavy Reading

The diagram shows that operators can either start with Option 3x, upgrade to Option 7x/4 and then migrate to Option 2 (SA), or go directly from Option 3x to Option 2. (Refer to the paper for an explanation of these terms -- warning, there's lots of jargon). To summarize:

  • The Option 3x > Option 7x/4 > Option 2 migration offers a good solution where the operator wants tight 4G-5G interworking at the RAN level. This is attractive in some aspects, but this path increases costs in terms of gNB software upgrades and reconfiguration of transport. Neither Option 7x nor Option 4 has a committed device chipset roadmap at this stage.

  • In some cases, especially where extensive 5G coverage is deployed and compatible devices are available in volume, the operator may elect to migrate directly to a 5G core using Option 2. In this case, the 5G core interworks with the existing EPC at the core level. In this scenario, the existing EPC may continue to support NSA devices connected to the same NR radio as devices capable of SA-mode. That is to say, Option 3x and Option 2 operate in tandem.

Did I mention this is complicated? There remains significant work to be done in standards, devices and service portfolios for operators to crystallize and develop their core network strategies. Despite this multitude of moving parts, the hope is that the move to cloud-native core networks, already underway, will allow operators to make this migration in software as much as in hardware.

This blog is sponsored by Huawei

— Gabriel Brown, Principal Analyst, Mobile Networks and 5G, Heavy Reading

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