Avaya BCM 2.0 IP Telephony Manual de usuario descargar pdf (Pagina 13)

Overview 13

P0911590 Issue 02 Enterprise Edge 2.0 IP Telephony Configuration Guide

All gateways in the intranet must use the same codec types.

Each gateway is configured with available codecs with the selected order of use.

The codecs configuration must reflect available bandwidth on the network. Codec

options are between quality compared to bandwidth.

The supported codec types are configured in the Modifying the Local Gateway

Configuration table section on page 65. The G.711 codec provides the best audio

quality but uses the greatest amount of bandwidth. The G.729 and G.723.1 codecs

use less bandwidth, but reduce audio quality. The installer or administrator

determines the best option for the user and the available bandwidth on the intranet.

For example, if the WAN link cannot support multiple 64 kbit/s calls, G.711 must

not be configured as a supported codec.

Enterprise Edge supports and recommends the following order for codec selection:

• G.729

• G.723.1 (6.3 kbit/s or 5.3 kbit/s)

• G.711

The G.729 codec provides the best balance of quality audio plus bandwidth savings.

For more information about codecs, see the Codec types section on page 37.

Silence compression

G.723.1 and G.729, Annex B support Silence compression.

A key to VoIP Gateway’s success in business applications is reducing WAN

bandwidth use. Beyond speech compression, the best bandwidth reducing

technology is silence compression, also known as silence suppression. Silence

compression technology identifies the periods of silence in a conversation, and

stops sending IP speech packets during those periods. Telco studies show that in a

typical telephone conversation, only about 36-40% of a full-duplex conversation is

active. When one person talks, the other listens (known as half-duplex). And there

are important periods of silence during speaker pauses between words and phrases.

For more information about silence compression, see the Silence compression

section on page 38.

Echo cancellation

When a two-wire telephone cable connects to a four-wire PBX interface or a central

office (CO) interface, the system uses hybrid circuits to convert between two wires

and four wires. Although hybrid circuits are very efficient in their conversion

ability, a small percentage of telephony energy is not converted but instead is

reflected back to the caller. This is called echo.

For more information about echo cancellation, see the Echo cancellation section on

page 40.

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Avaya BCM 2.0 IP Telephony Manual de usuario Pagina 13