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With the purpose of maximizing spectral efficiency and allow for network carrier aggregration, the roll-out of VoLTE in existing LTE networks is a critical step. With the introduction of any new voice technology, there is a need for measuring the actual voice quality of the network. This is the complete end to end voice quality rather than the method on mature networks of evaluating the quality of the radio link. The MOS (Mean Opinion Score) is required to determine the customer experience. Traditionally this requires the use of additional test equipment, base systems, and the application of voice quality algorithms such as PESQ, which uses actual human voice samples to measure what the end user would hear.
With VoLTE comes the PESQ algorithm successor, POLQA. POLQA is a non-public ITU standard which allows for the generation of MOS scores on IP based voiced networks. Beyond VoLTE, this could include services like Skype, Google Voice, etc. Some overview information on POLQA technology which is also available at: http://www.polqa.de/
With the use of such algorithms, the purpose and scope of requirement needs to be realized. MOS scoring is vital for the following purposes:
- Quality of Network Before Launch
- Ensuring Radio Link Quality matches MOS Quality
- Network benchmark to determine quality over time
The focus on these items is based on the idea that once the Radio Link Quality measurements are in tune with expected voice quality to the user, the only non measured changes from field data collection would be quality issues introduced in the core network. Core network quality is difficult to measure issues and degradation beyond traditional outages. This difficulty introduces the need for POLQA type systems.
When considering your test measurement requirements, determine the long term versus short term requirements for a MOS type scoring system. The greater the complexity of test setups typically introduces the possibility of error, more data not analyzed, and most importantly greater costs which may not be needed.