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Voice over X: Prominent voice technologies associated with LTE

Several avenues are available to operators who want to provide voice services on their LTE networks. To better understand the trade-offs that LTE operators face when providing high-quality and reliable voice services, each voice technology should be demystified.

What are the different voice technologies that can be deployed on LTE networks? What advantages and challenges are involved in their implementation? This blog post breaks it down for you.

Voice Technologies in the LTE Landscape


For operators deploying LTE, the most logical first step to provide voice services is to “fall back” to their legacy 2G/3G circuit-switched networks. This approach of falling back to an existing legacy network for voice services is called circuit-switched fallback (CSFB).

CSFB is generally seen as a temporary, stopgap solution because it enables the delivery of voice services in the short term with minimal network upgrades. However, due to other reasons, such as longer call setup times and suspension of ongoing data sessions, CSFB should not be considered a permanent and long-term solution.

2. VoLTE

VoLTE is a voice technology that was developed to support voice/SMS services natively on LTE networks. Because voice is delivered as data directly on the LTE network, the legacy circuit-switched voice networks no longer need to be maintained. Practically, however, they must be preserved because legacy 2G/3G networks cannot be decommissioned overnight, at least not until LTE provides full coverage of the operator’s market.

There are many documented advantages to VoLTE: high-definition (HD) voice quality, efficient use of spectrum, faster call setup times, seamless interworking between operators, to name just a few. Although these advantages are clear and manifest, VoLTE remains an extremely demanding service, putting tremendous stress on the network, both in terms of voice data processing at the highest priority level and significantly increased signaling traffic associated with policy and charging control (PCC).

3. VoWi-Fi

VoWi-Fi is a voice technology that uses Wi-Fi as the access technology to extend service to areas where coverage and congestion is a problem. This extra spectrum—and its widespread availability—has helped operators to substantially reduce the cost per bit. The presence of access points, which are located indoors and, therefore, are closer to subscribers, ensures suitable signal strength. These benefits led operators to consider Wi-Fi for voice services. Thus, VoWi-Fi was born.

Along with the benefits of offloading the network, it also provides other major benefits. With VoWi-Fi, operators have the ability to provide roaming subscribers with access to their home network via the Wi-Fi access of the visiting network. This means that subscribers can enjoy local rates even while roaming. Such service availability and cost savings are beneficial for both subscribers and operators.

Each voice technology associated with LTE is challenging in itself. The challenge in wireless networks today is the fact that multiple voice technologies need to coexist and interwork seamlessly with each other. This is the challenge of Voice over X.

To learn more about these voice technologies and the solution to successfully overcoming the Voice over X challenge, read the application note Demystifying Voice Technologies on LTE Networks.