VoLTE: innovating voice

Voice calls remain central to mobile operator’s business model as they receive over 60% of their revenues from voice and SMS traffic. Operators know there is no room for error. It is therefore necessary to have a viable and standardized solution to provide these services and protect this revenue. LTE is designed as a complete IP system for carrying data exclusively where initially operators have to carry voice by reverting to 2G/3G networks through CS Fall Back. Today, VoLTE has become the next logical move for handling end-to-end voice calls over IP. South Korean pioneers introduced VoLTE in mid 2012 and this year, operators worldwide will multiply lab and field tests to offer innovative voice experience.

VoLTE promises

VoLTE provides a range of advantages that includes:
  • Better call quality: as VoLTE introduces High Definition voice and faster call establishment.
  • Higher spectral efficiency: an operator refarming its 2G bands into 4G will be able to handle 6 times more voice calls.
  • Rich Communication Services (RCS): with VoLTE, mobile operators can deliver a new conversation experience of enriched voice, often bundled with new and attractive services (such as instant messaging, video calls, file sharing) and unlock new revenue potential. Moreover, VoLTE with RCS is an excellent vehicle to build a key differentiator to compete with OTT players such as Skype and WhatsApp: universal reachability through a standard MSISDN phone number.

Ensuring on-time VoLTE introduction

As with any new network feature introduction, VoLTE comes with a lot of challenges to be tackled within a very aggressive time schedule. Astellia provides a troubleshooting solution with dashboards to efficiently benchmark vendors, detect malfunctioning handsets and assess interoperability issues between vendors. On top of its product portfolio, Astellia offers Consultancy Services consisting of on-site experts engaged with operator’s teams during Lab Tests, Field Interoperability and Friendly User Tests. They generate dedicated reports, pinpoint issues, find out root causes, and provide evidence to transfer tickets to the right vendor.

1. Ensuring voice call establishment

For a good voice call experience it is crucial to be always reachable and get fast access to your respondent. Astellia addresses the needs of Core EPC and Core IMS teams. In addition to reporting 4G bearer setup success or delays, Astellia monitors SIP at S1-U interface to detect interworking issues between 4G network layers and SIP voice service layers. Furthermore, Astellia provides in-depth monitoring, analysis and troubleshooting of SIP/Diameter at the Core IMS. 


2. Ensuring voice call continuity
When a subscriber leaves the LTE coverage area a handover to 3G/2G layer is automatically performed thanks to Single Radio Voice Call Continuity (SRVCC) bridging VoIP IMS Core with the legacy Core CS. Astellia brings KPIs to monitor, analyze and troubleshoot E2E call traces and hand-over efficiency between Core IMS, legacy Core CS, EPC, and 4G RAN, 2G/3G RAN. Through E2E KPIs Astellia masters the global performance of SRVCC and pinpoints origin of delays occurring during handover.
3. Ensuring voice and data quality
Subscribers moving to VoLTE expect the highest voice experience as HD voice is marketed. But they don’t have a clue of the difficulty for operators to handle VoIP end-to-end down to the handset. Astellia provides VoIP call quality metrics including Mean Opinion Score (MOS), packet delay, jitter, packet loss and latency. Through relevant Key Performance Indicators (KPIs) mobile network operators get precious information which helps them troubleshoot areas with poor quality, investigate customer complaints and hence improve the customer experience.