Network Latency Jitter & MOS Quality Estimator
Calculate Mean Opinion Score (MOS) for VoIP and video quality from latency, jitter, and packet loss using ITU-T E-Model
Worked Examples
Example 1: VoIP Call Quality Assessment
Problem:Corporate office has 50ms latency, 10ms jitter, 0.3% packet loss using G.711 codec for internal calls. Is quality acceptable for business?
Solution:Network Metrics:\n- RTT: 50ms (one-way: 25ms)\n- Jitter: 10ms (good)\n- Packet loss: 0.3% (good)\n- Codec: G.711 (uncompressed)\n\nE-Model Calculation:\n- R0 (base): 94.2\n- Id (delay impairment): 0.024 × 25 = 0.6\n- Ie (codec): 0 (G.711)\n- Ipl (loss): 0 + (95 - 0 - 0.6) × 0.3 / (0.3 + 25.1) = 1.1\n- Jitter impairment: 10 × 0.15 = 1.5\n- R-factor: 94.2 - 0.6 - 1.1 - 1.4 - 1.5 = 89.6\n\nMOS Calculation:\n- R = 89.6 (>80)\n- MOS = 1 + 0.035(89.6) + 7e-6(89.6)(89.6-60)(100-89.6)\n- MOS ≈ 4.38\n\nQuality Rating: Excellent\nVoIP Target: 4.0 ✓\nVerdict: Quality exceeds business VoIP standards
Result:MOS: 4.38 (Excellent) | Meets target | Network quality excellent for business VoIP
Example 2: Video Conference Troubleshooting
Problem:Remote worker experiences choppy video. Latency 120ms, jitter 35ms, packet loss 1.5% on Opus codec. Why is quality poor?
Solution:Network Analysis:\n- Latency: 120ms RTT (60ms one-way) - Acceptable\n- Jitter: 35ms - High (threshold: 30ms)\n- Packet loss: 1.5% - High for video (threshold: 1%)\n- Codec: Opus (good loss concealment)\n\nImpairment Breakdown:\n- Delay impairment: 60ms one-way = 1.44\n- Jitter impairment: 35 × 0.15 = 5.25 (significant)\n- Loss impairment: ~6.5 (1.5% loss)\n- Total R-factor: ~75\n\nMOS ≈ 3.4\nQuality: Fair (below 3.8 video target)\n\nRoot Causes:\n1. High jitter (35ms) causes variable delay\n2. 1.5% loss creates visible artifacts\n3. Combined impact reduces MOS below acceptable\n\nSolutions:\n- QoS marking (DSCP EF) to prioritize traffic\n- Check WiFi congestion (switch to 5GHz or wired)\n- Reduce other network usage during calls\n- Increase jitter buffer (adds latency but smooths)\n- If pe
Result:MOS: 3.4 (Fair) | Jitter + loss are primary issues | QoS + wired connection recommended
Frequently Asked Questions
What is MOS (Mean Opinion Score)?
MOS is a numerical measure (1-5) of voice or video quality as perceived by users. 5 = Excellent, 4 = Good, 3 = Fair, 2 = Poor, 1 = Bad. It's based on subjective listening tests or objective models like E-Model (ITU-T G.107). MOS predicts user satisfaction—scores below 3.5 often result in complaints.
How does latency affect call quality?
Latency (round-trip time) causes conversational delay. <150ms is imperceptible; 150-300ms is noticeable; >300ms disrupts natural conversation flow. One-way delay >177ms degrades MOS exponentially. Satellite links (500-700ms) make real-time conversation difficult. Latency also affects echo perception.
What is jitter and why does it matter?
Jitter is variance in packet arrival times. Constant 50ms delay is manageable; 10-100ms variable delay causes choppy audio. Jitter buffers smooth this (30-100ms typical) but add latency. High jitter (>30ms) requires larger buffers, increasing delay. VoIP is particularly sensitive—jitter >50ms causes noticeable degradation.
How do I measure network quality for VoIP?
Tools: ping (latency), iperf (throughput), smokeping (jitter), wireshark (packet loss). Continuous monitoring: use SIP agents to simulate calls, measure MOS. Cloud services: Twilio, AWS ChimeSDK provide quality metrics. On-premises: PRTG, SolarWinds. Test during peak hours—quality varies by time.