Extending the benefits of VoLTE to international voice calls.

Voice over LTE (VoLTE) delivers increased network efficiency, trusted mobile operator voice services, and high quality video calling. Mobile operators around the world are now launching national Voice over LTE service to their subscribers. To achieve the full benefits promised by VoLTE, they must also offer international VoLTE calling. This presents major implementation challenges, including:

  • Achieving global reach for VoLTE calls;
  • Supporting interworking between operator networks;
  • Exploiting HD Voice capabilities; and
  • Selecting the best VoLTE roaming model for your business.


Operators can choose different models for servicing VoLTE subscribers originating or receiving calls while roaming in another VoLTE network. iBasis supports both of the GSMA-defined models: Local Breakout (LBO) and S8 Home Routed (S8HR).

LBO is designed to replicate todays roaming architecture, functionality and commercial model, while S8HR’s goal is to simplify VoLTE roaming implementation and reduce time-to-market for global VoLTE roaming. S8HR has drawbacks when it comes to full telecommunications features. For example, it offers no support for Lawful Intercept, emergency calling, and visited network data retention, as well as other features. It also has shortcomings related to quality, including negative impact to handover time in case of eSRVCC and delay impact on regional calls.  iBasis’ S8HR solution, provided as part of iBasis’ existing S8/GRX service, eliminates S8HR drawbacks.  The drawbacks can be addressed individually by iBasis or collectively addressed by utilizing the iBasis IPX Hub Breakout (HBO) solution. With iBasis enhanced S8HR, VoLTE operators can take advantage of the accelerated roaming implementation offered by S8HR, without sacrificing telecommunications functionality and high voice quality.