To Launch or Not to Launch VoLTE — Questions to Be Answered

Are you really ready to launch your VoLTE network?

Yes, you’ve laid the groundwork with your LTE deployment. You’ve got your marketing materials ready to go. You’re right on the cusp.

Or are you?

After all, it feels like operators have been knocking on the VoLTE door for years, espousing its benefits since at least 2011. So why haven’t many of them pulled the trigger yet?

Here’s why:


Interference is Interfering

Operators continue to spend billions of dollars deploying LTE networks and maximizing their performance. The problem is that many of those networks are burdened by enormous amounts of data and experience significant interference, which is detrimental to LTE. LTE prefers a cleaner, less overlapped network. This is especially true of networks that base their LTE design on spread-spectrum 3G technologies like CDMA & WCDMA. These technologies were built on the principle of operating in noise. They use Walsh/OVSF codes to extract data and, with soft handoff, provide macro diversity for optimal performance.

VoLTE requires even less interference and is less tolerant to PER due to the very nature of voice service. As such, when preparing for VoLTE, operators must first ensure that their current networks are optimized to greatly reduce the amount of network interference. The target is generally less than 0.01%, which is also the requirement for QCI-1. QCI-1 is the Quality Channel Index defined with certain requirements to meet quality-of-service targets for voice over LTE. This dictates the need for extremely minimal interference to deliver even adequate VoLTE performance.

It’s not just about optimizing to mitigate interference, however. True and complete VoLTE optimization must take into consideration both core and physical network components. This involves management of the IP Multimedia Subsystem (IMS), corresponding bearers, and physical layers such as user equipment terminals and radio access networks.


Optimizing the Core Layer

IMS is a standardized architectural blueprint for combining voice and data services, and is the foundation for VoLTE. Bearers – virtual concepts that are a component of IMS — help prioritize data delivery. They work in conjunction with each other to ensure that services get delivered in the most efficient manner possible to users, similar to how a service like UPS may prioritize parcel shipping to various customers.

Effective delivery of VoLTE services requires certain parameters, though. For example, operators must be able to support a QCI-1 bearer that is suitable for voice delivery, which requires a sub-100ms delay with a Guaranteed Bit Rate (GBR) and targeted Packet Error Rate (PER) of less than 0.01%. Ensuring this and other parameters requires continual analysis and overview of network performance.


Optimizing the Physical Layer

As important as the virtual layer is, it’s important not to forget that VoLTE is still based on a physical layer that also needs to be optimized. No matter how well-tuned the core network is, if the physical layer is not ready to support VoLTE, the user experience is bound to suffer.

There are several components to this. The radio frequency network must be optimized for carrier to interference-plus-noise ratio (CINR). Likewise, radio access networks, including base stations and handsets, must also be optimized for CINR. This should be done parallel to the core network optimization.


Successful VoLTE and Network Capacity

It is very important for the operators that VoLTE succeed from a network capacity perspective as well. A successful VoLTE network will eventually help shift traditional voice traffic to an advanced, high-quality voice experience through VoLTE, freeing up 2G or 3G networks. That will in turn allow them to re-harvest spectrum and add additional capacity to 4G networks.


— Bhupinder Mann


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