We Ask the Experts: How Can VoLTE Outperform Circuit-switched Services?

Next Generation Communications Blog

We Ask the Experts: How Can VoLTE Outperform Circuit-switched Services?

By Jean Jones, Director, Wireless Marketing, Alcatel-Lucent

This second blog in our series begins a discussion of the most basic, yet crucial voice over LTE (VoLTE) question: How can you make sure your 4G voice service works as well — if not better — than familiar 3G wireless services. Your subscribers’ expectations are high now, as VoLTE services are launched on a larger scale. And they’re looking for carrier-grade quality.

To satisfy these expectations (and reap all the benefits of VoLTE), you need to start with a new way of thinking about service deployment. According to the VoLTE experts I’ve talked to, that means developing an end-to-end strategy. Then, ideally, carrying out your plan with the help of a cross-functional team.

The rest of this blog takes a closer look at this distinctive approach, using information from my interviews with:

  • Luis Venerio, who works with the VoLTE Readiness Services team
  • Micky Choi, who provides IMS engineering expertise for new services

They both have experience working on some of the world’s largest VoLTE deployments representing millions of subscribers— and their insights provide real-world lessons straight from the field.

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Thinking end-to-end

Why is a new vision of deployment essential for VoLTE? --Because mobile IP voice blends mobility, IP and real-time communication.  It begins with a subscriber’s smartphone. Then relies on integration with all three layers of the LTE network — access, packet core and IMS — in order to deliver the requisite service. As Luis says, “This cross-domain service touches nearly every network element.” Or, as Micky describes it from an IMS point of view, “VoLTE differs from other IMS-based services by having interdependencies with more domains.”
As a result, you’re faced with new points of failure to consider, along with new sensitivities involved in delivering voice across each of those domains. So, to deliver optimal performance, you need to look at the big picture, end to end, and make sure that everything is tightly integrated. But you also need a fine-grained understanding of the requirements, technologies and network elements within each domain.

That’s why the ideal way to get ready for VoLTE is to work with a cross-functional team that can offer both points of view. This approach differs from current practices, Micky explains, because “most large carriers have separate organizations managing and operating the various segments and technologies. But to deliver VoLTE with high quality and scale for a large deployment, all the organizations and technologies have to come together and be well integrated."

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Working cross-functionally

Coming together starts at the design phase. Micky believes that collaboration is crucial for designing the end-to-end architecture and points out that, “Special consideration is needed at the key interfaces where various technologies intersect, such as the edge of IMS access and the device. Existing standards provide guidelines for that particular interface — and others. But VoLTE performance is optimal where there is tight integration. So we recommend documenting common requirements for both sides. This helps you avoid different interpretations of the standards and prevents issues from arising later. For example, it’s a good idea to define whether IPsec will be used, what transport type will be used and so forth.”

Luis agrees that cross-domain awareness begins with service design — and continues throughout each phase of VoLTE deployment. He says, “You have to look, first, at how the network is configured and how calls are establishing. Then you quantify performance to make sure everything is optimized and meeting expectations. Then there’s the deep dive to troubleshoot. But even at that phase, the Alcatel-Lucent VoLTE Readiness team looks across domains by using logs and other tools to identify the source of a problem.”

For example, in a recent deployment, the cross-functional team identified several cases of imperfect race condition handling in the interface between network elements. This condition occurs when there are conflicts in the sequence or timing of certain processes, so that messages get dropped. It’s most common when network elements are from different vendors, Luis points out, but they are notoriously difficult to identify. Using a collaborative approach, the Alcatel-Lucent team identified a race condition occurring between the Mobility Management Entity (MME), a key control node for an LTE access network, and a third-party gateway. Once the issue was discovered, both sides continued working together in design discussions and agreed on enhancements that will improve integration in future releases.

Putting an end-to-end strategy into practice

Of course, having a new way of thinking and working isn’t the only requirement for providing a high-quality 4G voice service. But it provides the crucial foundation you need for addressing VoLTE’s unique characteristics. So you can deliver optimal performance on your launch date. Then keep your service operating at its best day after day.  

My upcoming blogs will offer a more detailed view of how an end-to-end strategy gets put into practice. They’ll focus more specifically on ensuring high QoE, achieving KPIs, troubleshooting, maintaining reliability and more. My next blog asks the experts about their insights on how to achieve exceptional QoE in VoLTE networks.

Read the first blog in our series We Ask The Experts: A Blog Series on Real-World VoLTE Deployments.

Click here to subscribe to our series. To join the discussion on Twitter, follow #VoLTE, or connect with @JeanSJones or @EdElkin1.

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