The Key Considerations for IMS and 5G

Brandon Larson- SVP, GM, Multimedia Business Unit at Mavenir, talks about some of the key overlaps between IP Multimedia Subsystem and 5G.

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2022 - The 5G Year

Brandon Larson- SVP, GM, Multimedia Business Unit at Mavenir.


By Brandon Larson

The telecommunications industry is mirroring the IT industry, as cloud-native, agile design, containerization, dev ops, automation … it all sounds like a typical cloud-based IT industry conversation. The telco industry began moving in the IT direction over a decade ago when it took the first step to embrace Commercial off-the-shelf (COTS) hardware and now we’re delivering microservices on containers.

The industry pace toward IT trends is picking up and if you’re not onboard the cloud-native, 5G ship … well, it sailed!


Voice Services Based on IP Multimedia Subsystem (IMS) Will Evolve with 5G Core and Radio

To say that 5G is making waves across the entire mobile ecosystem is an understatement. It’s changing everything and driving the trend toward cloud-native IMS.

While we look forward to the day when all networks rely mainly on 5G infrastructures, for most that will require significant change. One thing is certain, IMS remains essential for operator voice services as we transition to 5G. IMS provides the foundation for voice through the packet core transition from 4G LTE, to 5G NSA, to 5G SA.


Having an IMS core deployed for voice services will make any move to 5G smoother. And the importance of changing the operations paradigm to reflect the 5G era is another requirement. The future will yield a single IMS core, deployed with a single set of services, as well as service parity—whether delivering the services over 4G or 5G and seamless mobility between the generations.

What IMS Changes are Needed for Full 5G?

The evolution will most likely be gradual. First, a company needs VoLTE and the IMS for voice calls deployment. This enables 5G devices to fall back to the VoLTE network for making and receiving calls. There is a fallback to the 3G standard being defined, but this will be a clunky 2 step procedure with higher latency and a poor user experience. The poor experience, coupled with the reality of a stop-gap solution involving declining 3G technology, makes it doubtful to be adopted in the market.


Companies can deliver voice over 5G Radio once it has placed the VoLTE network. Here the 5G radio uses the existing 4G packet core so there is no change to IMS in terms of connectivity. The IMS modification needed is to be ‘access aware’ so differentiation can be made for service assurance and billing operations.

The final step in the journey is connecting the IMS core to 5G packet core components. This is where we see the main IMS evolution in terms of connecting and interacting with the 5G packet core.

The Other Big Considerations for IMS on 5G


There are 2 big considerations to address as IMS evolves with 5G:

Network Technology Evolution: How do you make voice services work tomorrow like they do today but with a different packet core technology? How do you enable voice on a new 5G environment and not break the existing service?

Operational Evolution: The operational paradigm shift in 5G is a much heavier lift than the network technology evolution. Shifting to a 5G world with containerization and automation brings the promise of many benefits. However, this requires potentially difficult operational transformation as there is a lot of inertia in how the industry operates voice services today.


This is where we need the cloud-native IMS. The IMS core will coexist with the new 5G packet core so IMS must evolve to use the same container-based cloud infrastructure and adapt to a DevOps model of operation.

Speaking of the Containers in Store for 5G

Using containers in the cloud environment is another big change to the go-to-market strategy of operators. 5G core workloads are the tidal wave behind the move to containers in a Kubernetes environment today. In turn, this is driving all workloads and containers, not only IMS but messaging workloads as well. The goal is to have a common cloud infrastructure with operations harmonized across a common continuous integration/continuous deployment (CI/CD) pipeline and automation framework.


Evolution is one of the biggest challenges. All workloads must work in this new, cloud-native, containerized, fully automated environment. Automation is the cause and the method for changing the operations model. For example, CSPs operates more like a FANG (Facebook, Amazon, Netflix, Google) and less like a public utility. New plans will have to operate like a FANG, a true cloud-first company. It’s a completely different operating model and one that can be far more profitable.

Some of the key benefits of having all workloads working on the same cloud-based environment

  • Reduce the overall CAPEX burden. Operators will have the radio, packet core, IMS, and messaging workloads, all sharing the same computer hardware, network storage, and cloud infrastructure.
  • Harmonize the end-to-end network operations. Make deployment upgrades and configuration changes across all these different workloads more efficient. These workloads are all packaged in a common artifact framework, such as a container image and Helm V3 charts, which will be delivered to the same repository and deployed, updated, and maintained using the same CI/CD pipeline.
  • Enable a more holistic end-to-end view of services. Gain the ability to make more targeted and intelligent decisions in managing the network. All these workloads will plug into a common observable framework, which will put all the network information in a commonplace.

From a business perspective, a fully containerized and cloud-native IMS core allows for rapid service delivery. Highly automated, it reduces deployment time and optimizes application management. Containerization gives operators power over their own destiny. IMS has been around for quite a while, and we will continue to rely on it well into the future.

Brandon is the Senior Vice President and General Manager of Multimedia Business Unit at Mavenir. Brandon has diverse experience having held roles in sales, marketing, and program management at Nokia and Ciena.

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