Behind the VoLTE Curtain, Part One

QUANTIFYING THE PERFORMANCE OF A COMMERCIAL VoLTE DEPLOYMENT Part of “The Mother of all Network Benchmark Tests” Series of Reports

08/07/2014 | 67 pages
Price: $1,750.00

Benchmark study of AT&T's VoLTE service

We conducted a network benchmark study of AT&T’s VoLTE service in Minneapolis-St. Paul in collaboration with Spirent Communications who provided us with its test equipment and engineering support. In a forthcoming report due out later this fall, we will leverage data observations that we made in this study and apply them to a lab-based study where we can conduct additional testing in a very controlled environment.
KEY OBSERVATIONS INCLUDE THE FOLLOWING:

• VoLTE is pretty much everything that we hoped it would be.
• The call quality (MOS), based on the POLQA algorithm, greatly exceeded that of 3G CS Voice and it was measurably higher Skype (over Wi-Fi and LTE). With background applications running on the same phone and transferring data with the network the VoLTE results were considerably better than Skype – the latter seemingly showed no impact while the latter frequently failed to deliver the voice packets in many cases.
• Relative to 3G CS voice, VoLTE’s big advantage was the call setup time with a CSFB call taking nearly twice as long to establish as a VoLTE call. o VoLTE required substantially fewer network resources (DL/UL resource blocks, scheduled TTIs, PDCCH scheduling grants) than Skype and presumably other OTT voice applications. We attribute this advantage to QCI=1 features, such as RoHC, TTI bundling, and DTX/DRX, which are either not supported by an OTT application or which are supported less efficiently. Once SPS and short DRX are launched the differences should be even more substantial.
• The network savings also translates into VoLTE call requiring less current drain and power consumption than a Skype call, meaning a longer batter life. Presently 3G CS voice has a slight advantage over VoLTE in this category.
• Continued improvements in LTE network coverage will give VoLTE an even greater advantage in the future and it will reduce the number of eSRVCC handovers to the 3G CS network.