VoLTE is the all-IP method that tightly links the voice application to the LTE network to assure the best subscriber experience in terms of performance, reliability, interoperability and global roaming.
The Value of VoLTE
- It integrates voice with 4G LTE to ensure the critical reliability and quality of that voice service.
- It ensures subscribers continue to enjoy key mobile features such as global roaming, global interoperability and a global ecosystem of smartphones and tablets.
- It enables new services beyond traditional mobile telephony.
- With VoLTE, smartphones and tablets remain in the 4G LTE network even during voice calls, allowing new services such as video-communications and converged IP messaging to be delivered.
However there is a different method to support Voice when you’re in 4G Network, (CSFB: CS Fallback) where a voice call (originating or terminating) forces a fallback to legacy 2G or 3G service. This means that during voice calls the subscriber is limited to legacy circuit-switched (CS) voice, texting and slower 3G mobile data services — or the subscriber may lose mobile data service altogether during a fallback to 2G.
The Difference between VoLTE and CSFB:
This figure from Alcatel-Lucent shows that has a good edge than CSFB specially in Voice quality and Call Setup time and those are one of main KPIs that are measured by some of 3rd party company like P3 Group to make a benchmark between operators.
VoLTE optimizes the spectral efficiency of mobile voice in 4G LTE networks. It does so through optimizations such as
- Robust Header Control ([RoHC].
- Reducing bandwidth consumed).
- Semi-Persistent Scheduling ([SPS].
- Reducing the control channels used.
- Transmission Time Interval (TTI) bundling.
For more about VoLTE principles, IMS architecture, VoLTE End-to-End Call and VoLTE main features, I prepared this intensive
VoLTE Optimization Training.