How to ease the pain of 4G and 5G interworking
Choices, choices! A recent report by Strategy Analytics examines the complex choices for operators as they move from 4G to 5G, via 5G Non-Standalone (NSA) architecture, a 5G Standalone (SA) Core or a progression from one to the other. In among all this complexity the author, Sue Rudd, hones in on a critical success factor with whatever path operators choose – and that is the crucial need for 4G and 5G to work together.
The pending 3GPP Release 16 – which at the time of writing has been frozen until June 2020 – paves the way to transition from 4G to 5G by bridging the two major network generations. Critically, Release 16 stipulates the separation of 5G functions and 5G data, says Oliver Korfmacher, vice president of product management at Enea.
Tectonic shifts ahead
By separating 5G functions and data, operators immediately gain more control, freeing them from the vendor lock-ins that have dogged previous network generations. With the open architecture of the 5G core, operating a best-of-breed multi-vendor network environment becomes possible, if not preferable.
Pragmatically too, especially now, many operators will not be able to afford to fully deploy 5G using large vendors because future revenues may not support such a move. The coronavirus pandemic will only serve to increase price sensitivity in consumer and business markets globally, putting operators in the familiar painful territory of having to balance market share and scale versus margins.
For competitive reasons, some operators will provide 5G at the same or similar fees to 4G and others will decide that they will only be able to charge a small premium. Operators, therefore, might need to consider vendors that can offer “pay as you grow” versus CAPEX-intensive pricing models, to make 5G monetisable as they transition from 4G.
Unsurprisingly, some large legacy vendors are resisting this drive towards interoperability because it reduces operators’ reliance upon them and represents a clear and present danger to their revenues.
The unlikely battleground
The unlikely battleground for 4G/5G interworking – and wrestling back control of the network from legacy vendors – will be subscriber data for voice termination. Many network providers have already identified a problem with voice termination between 4G and 5G. For interworking between 4G and 5G networks, the handover between 4G legacy circuit switch systems and 5G-based IP is problematic.
The crux of the problem is that the 4G core doesn’t know that the 5G core exists. As such, the 5G network needs to emulate the behaviour of the 4G network to avoid termination issues. This can be achieved by emulating some of the 4G network functions using the mobility management entity (MME) to map certain attributes and fields to 4G-compatible values.
A recent experience with a US Tier 1 North American operator is the perfect microcosm of the entire 4G/5G interworking challenge – and the challenge of wrestling back control of the network from large vendors. And the way they manage these challenges is entirely emulate-able. The network provider, which has a large subscriber base, was using a legacy vendor to handle its 3G and 4G subscriber data management (SDM). This vendor attempted to retain ownership of the subscriber data and demanded extra money for SDM and for the transition from 4G to 5G call termination.
However, the carrier wanted to take a best-of-breed approach for 4G/5G interworking using standard interfaces. For 5G, the network provider wanted a different vendor for each domain, meaning there would be one vendor for SDM and another for IP switching. The operator identified the critical use cases that it needed to be free from vendor lock-in; in this case, 4G calls to 5G IP voice termination.
The multi-vendor solution had zero negative impact on existing systems and it saved the operator from paying extra money to the incumbent vendor. The operator looked for solutions that created minimum impact on existing infrastructure and shielded their business from future problems. They then deployed a universal 4G/5G data management strategy to permanently break the cycle of vendor lock-ins, making all network and subscriber data universally accessible by the network elements and applications that need it. This made it impossible for large legacy vendors to claim ownership of subscriber data – or any other data – in the future.
4G and 5G will likely coexist for several years – there is little doubt about that. Based on many discussions with operators, there are some clear takeaways that operators need to bear in mind as they mull over their choices for 4G/5G interworking and 5G data management.
Firstly, to unlock the benefits of 5G, start by identifying the critical use cases that require 4G interworking and engage vendors early to achieve this vision. Ultimately, the success of 4G and 5G interworking rests on vendors being cloud-native and having continuous integration and delivery (CI/CD) processes for improvement. They should also have automation capabilities to ensure that the operator’s network meets demand now and well into the future. It is worth remembering that interworking supports a seamless handover between the EPC and the 5G core.
Secondly, when addressing the requirements of 5G data management (covering 3GPP applications such as UDM, UDR, UDSF, AUSF, PCF and EIR), ensure that you’re creating a single-control database that can work across 4G and 5G frontends to achieve a universal data management approach. This will obviate double-provisioning and ensure there are no consistency problems between the two technologies. It will also increase reliability and scalability while reducing operational costs thanks to automation.
It is time for operators to leverage the full potential of agile 5G architecture. The challenges created by 5G rollout scenarios and the current pandemic are creating enough complexity as it is. However, the strategy to grapple with 4G/5G interworking is thankfully nowhere near as complex.
A typical architecture when a subscriber wants to approach 5GC, messages go directly to UDM/HSS combo and 5G profiles are stored in 5G UDR.
The author is Oliver Korfmacher, vice president of product management at Enea.