Mitel MiVOICE BUSINESS, Engineering Manualline

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Bandwidth, Codecs and Compression
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The wideband codec used by Mitel is G.722.1 at 32kbits/s/ (which is not to be confused with
the G.722 wideband codec, or the G.722.1C codec, or the G.722.1 at 24kbits/s).
Mitel currently uses the following CODECs in IP Telephony:
• G.711 (A-Law and µ-Law)
• G.729a
• G.722.1 at 32kbits/s
VOICE QUALITY AND CODEC SELECTION
The voice quality of the CODECs available is usually expressed in terms of a Mean Opinion
Score (MOS). The scores range in value from 1 to 5. Scores 4 and above are considered toll
quality. Table shows some typical CODEC MOS scores.
CODEC SELECTION
The CODEC to be used for a connection depends on a number of configurable parameters
including:
• Which Zone the network elements and devices are in
• Bandwidth Management - Call Admission Control Thresholds
• Network Zones - Intra-zone compression - Yes/No
• Network Zone Topology - Bandwidth Limits
• ARS Routes - Compression On/Off/Auto. Compression 'On' may override zone settings
(
Auto setting is recommended
)
The endpoint CODEC to use is also influenced by:
Can the end device support this CODEC? (Not all phones will support G.722.1, and some earlier
phone models may not support G.729. See phone details)
• Can the CODEC frame rate fit with the packet rate specified
• The MiVoice Business/3300ICP system can negotiate different CODEC types, but can only
terminate calls in G.711 or G.729, e.g. when used as a PSTN or TDM gateway. The same
CODEC G.729 is generally referred to as "compression" even though this is a generic term. CODEC
G.722.1 is generally referred to as "wideband" even though it also provides a bandwidth usage
improvement over G.711.
Table 55: CODEC MOS Scores
CODEC TYPE MOS LAN BANDWIDTH
G.711 4.4 ~100 kbit/s
G.729a 4.0 ~40 kbit/s
G.722.1 4.4 ~65 kbit/s