Do you know the Voice Call we Perform Daily is being tracked by Operators for KPIs?
Each Dropped Call, Bad Quality, Delayed Packet has some significant impacts on KPI Standards and a Operator rating relies on Successful Calls.
So before launch or post how these Voice Call Performance is tested, let us understand on details.
Voice quality in telecom networks is measured using objective algorithms and standards like:
POLQA (ITU-T P.863)
Latest standard for measuring voice quality.
Works for narrowband, wideband, super-wideband.
Used for VoLTE, VoNR, and modern codecs.
Objective → produces MOS score (1–5).
PESQ (ITU-T P.862)
Older standard.
Limited to narrowband/wideband.
Still widely used.
MOS (Mean Opinion Score)
Scale: 1 (Bad) → 5 (Excellent).
Originally subjective (humans listen & score).
Now estimated via objective algorithms (e.g. POLQA).
E-Model (ITU-T G.107)
Predicts voice quality mathematically.
Calculates “R-factor” → maps to MOS.
Used for network planning.
How these models are tested?
LAB Testing (Pre-Launch)
Field Testing (Field Trials/Customer Complaints)
Network Analytics (Post Network Deployment , Production, KPI)
What is the range for the KPI MOS Score?
- #4.3 ~ #5.0 - Excellent Score
- #3.5 ~ #4.3 - Good Score
- #2.6 ~ #3.5 - Fair Score
- #1.9 ~ #2.6 - Poor Score
- #<1.9 - Bad Score
What Tools can test this.
Lab Testing
- R&S CMX500 / CMW500 Rohde & Schwarz
- UXM Wireless Test Set Keysight Technologies
- MT8821C Radio Communication Analyzer Anritsu
- LandSlide,iTest Spirent Communications
Field Testing
- TEMS (Infovista) Infovista
- NEMO Keysight Technologies
- QualiPOC Rohde & Schwarz
How these Quality Tools Measures
SendReferenceVoiceSignal (e.g.“Hello Suraj K How are you?”)
The Tool Play Pre-recorded Voice Audio Files.
RecordReceivedSignal
Codecs (e.g. EVS,AMR-WB,AMR-NB etc.)
Packet loss, Packet Delay, Jitter
Note : It depends upon huge load of factors, RAN, CORE, CLOUD, Infrastructure Deployments. (Which has no right thumb rule).
CompareSignals
POLQA and PESQ algorithms analyze:
Distortion
Frequency response changes
Time alignment shifts
Clipping, noise, echoes
Calculate MOS
How Instruments works?
➤ Rohde & Schwarz CMX500
- Plays test voice file through UE.
- Records signal over radio or audio interface.
- Runs POLQA internally → reports MOS.
➤ TEMS / Nemo Drive Test
- Makes a real call on the live network.
- Records audio from microphone.
- Compares result to reference audio → computes POLQA score post-processing.
➤ Keysight UXM / Anritsu MT8821C
- Simulates network environment.
- Plays voice file via simulated call.
- Records degraded signal → runs POLQA.
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