DETEWE OpenCom 130, User Manual

Page: 105 / 204

Voice over IP (VoIP) Fundamentals
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G.729A (Level 2): Reduction to approximately 8 kilobit/s.
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G.723.1 6.3 (Level 3): Reduction to 6.3 kilobit/s.
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G.723.1 5.3 (Level 3): Reduction to 5.3 kilobit/s.
Unfavourable packet length selection may reduce voice quality. The duration of
the recording and not the data packet’s byte count is relevant in making this
selection:
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Duration <= 30 ms: optimal transmission
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Duration 40 - 60 ms: one quality-level depreciation
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Duration > 60 ms: two quality-levels depreciation
The achievable voice quality also depends on the packet propagation delay and
the packet loss between the terminals involved. These parameters can be deter-
mined using the “ping” program.
Note: Measurements made with “ping” are round-trip pro-
pagation delays. Divide the maximum value displayed by
two.
Packet Propagation Delay and Packet Loss
Value Quality Level Value Quality Level
Propagation delay
< 50 ms Optimal Loss < 1 % Optimal
Propagation delay
50-100 ms 0.5 level
depreciation Loss 1-2 % 0.5 level
depreciation
Propagation delay
100-150 ms 1 level
depreciation Loss 2-3 % 1 level
depreciation
Propagation delay
150-200 ms 2 level deprecia-
tion Loss 3-4 % 2 level
depreciation
Propagation delay
200-300 ms 3 level deprecia-
tion Loss 4-6 % 3 level
depreciation
Propagation delay
> 300 ms 4 level deprecia-
tion Loss > 6 % 4 level
depreciation