Voice Quality Assessment for VoLTE Devices

Opale Systems   Thursday, 23rd June 2022

VoLTE device manufacturers' challenge

Modem chipset designers and cellular device manufacturers need to characterize the performance of their products. Not just under ‘ideal’ network conditions, but also in the ‘real world’ of packet loss and jitter.

Network Operators too need to satisfy themselves about the voice quality delivered by new devices. And this is not only when the network has plenty of capacity, but also at times of peak traffic and cell loading.

In all cases, organizations must take control of the process by making detailed assessments to understand and optimize the performance of the products. And all this has to be done at the right time, before the costs and commercial implications reach unacceptable levels.

The RTP packet stream from the network to the VoLTE device may be subject to impairments including loss, jitter and mis-sequencing. The impairments have the potential to degrade the listening quality of the speech heard by the user. For this reason, QA engineers must quantify this for many combinations of impairment, codecs, bitrates and operating modes.

To be certain of separating cause from effect, your tests need to be 100% repeatable. Using a standard packet impairment generator does not achieve this, since it generates random impairment patterns.

Opale Systems helps you analyze and understand behaviors in terms of user experience

MCodecs respond to and handle short durations of the sound elements in the speech signal. The characteristics of the human voice are such that the effect on listening quality of loss or other distortion depends on when it occurs in relation to the speech signal. The performance of the codec implementation must be assessed under diverse packet propagation conditions. If an issue is found or suspected, the ability to maintain precise impairment patterns is key: if any unfavorable behavior ‘escapes’ the QA process the consequences for product and brand reputation may be severe.

Opale Systems helps you analyze and understand behaviors in terms of user experience, in multiple scenarios. MultiDSLA also provides the tools to identify and confirm such behavior and the unique method of creating impairment overlays ensures:

1. 100% repeatability
2. As many combinations as are required
3. No need for a separate packet impairment generator

The MultiDSLA test system supports both SIP/VoIP and analog domains and makes test calls directly to a device under test (DUT), generating a clean or precisely impaired RTP stream. The analog interface collects the speech signal received at the DUT and the test system generates POLQA scores which accurately predict the Mean Opinion Score (MOS) for listening quality.

MultiDSLA supports EVS and AMR-WB/NB codecs at all the bitrates of both codecs, enabling QA engineers to perform testing under all relevant conditions.