New Benchmark Studies Evaluate Enhanced Voice Services (EVS) in the Lab and Live Network

Signals Research Group and Spirent prove the benefits of the EVS codec in their “All Things VoLTE” series
woman looking at a cell phone standing by a bridge

San Jose, Calif. – (August 3, 2016) — Spirent Communications and Signals Research Group (SRG) revealed their latest collaboration on chapter 5 and 6 in the multi-part study of all things VoLTE. With global interest in the 3GPP-defined Enhanced Voice Services (EVS), the two industry leaders recently executed back-to-back studies to explore the benefits and user experience of this promising voice services codec, both in the lab and on a live commercial network.

The EVS codec is designed to support high quality and high efficiency and has intrigued wireless operators worldwide. Unlike its predecessor, AMR, which was used for initial VoLTE deployments and marketed as “HD Voice”, EVS was developed and optimized specifically for LTE. EVS is a feature-rich codec that supports everything from narrow band (NB) to super wide band (SWB) with bit rates starting at 5.9 kps to 128 kps and a multitude of advanced error treatment capabilities.

“Naturally, we were excited to take a close look at the promises of this new voice codec,” said Michael Thelander, President of SRG. “With all the hype over what EVS can deliver and the many features and deployment options for carriers, it is a great opportunity to evaluate many different use case scenarios and benchmark performance results. We ran round one on Spirent’s Elevate test system in the lab using Spirent Nomad to measure audio quality and then took the same Nomad measurement system to the field on a commercial network. The bottom line, EVS outperforms it predecessors and exhibited significant benefits.”

“Behind the VoLTE Curtain, Part 5” provided the industry’s first independent performance analysis of EVS and how it compares to AMR under a wide range of conditions in a tightly controlled lab environment. The Spirent lab configuration enabled precise control over the conditions (clean channel and noise) as well as the introduction of IP impairments including delay, jitter and packet loss which led to several key findings:

  • The EVS codec, when configured to operate in super wide-band mode, can deliver superior voice quality to AMR-WB while simultaneously consuming fewer network resources
  • With noise in the channel or IP impairments the benefits of EVS are very evident especially with EVS –SWB
  • The quality and tuning of the audio circuitry can have an impact on the voice quality and potentially negate the benefits of the wider bandwidth and higher bit rate codec options

“Behind the VoLTE Curtain, Part 6” leveraged a commercial network to conduct additional EVS tests and capture additional KPIs including the relative impact on network resources and current consumption. Highlights of this study include:

  • The EVS codec generally delivered superior voice quality when compared with AMR-WB voice codec, and in many cases the differences were substantial
  • The EVS codec generally required fewer network resources and sometimes meaningful fewer network resources to support a voice call compared with AMR-WB codec
  • No measureable differences in the power requirements were detected between EVS and AMR

“By testing in a commercial network, we were able to confirm that the observations we made in the lab environment carried forward to a commercial deployment, noted Mr. Thelander. “At the same time, testing in a commercial network meant dealing with an uncontrolled environment where variances in the test results were inevitable due to the nature of the beast.”

Signals Research Group has partnered with Spirent for over a decade on various benchmark studies with the EVS studies being the most recent chapters in a two-year focus on the investigation and evaluation of all VoLTE-related activities including VoLTE vs OTT, Video telephony and VoWiFi. Spirent and SRG plan to continue exploring additional EVS testing in the lab and are preparing a second round of video testing in both lab and field – stay tuned for more exciting results.

For a preview of the report in Signals Ahead, “Behind The VoLTE Curtain, Part 5 and 6” please visit www.signalsresearch.com.

For more information on testing the EVS Codec download our white paper "Testing the EVS Codec: Addressing Complex Challenges to Ensure Superior Audio Quality Performance". For more on Spirent’s Elevate VoLTE audio quality system, please visit http://www.spirent.com/Products/IMS_VoLTE_and_RCS_solution.

For more information on Spirent’s Nomad – part of the Umetrix User Experience Evaluation Platform, please visit http://www.spirent.com/Products/User_Experience_Evaluation.