Echo cancellation in a VoIP based PBX System

VoIP PBX systems utilize a combination of public telephone networks and packet switching technology. This kind of PBX phone system being hosted by a service provider usually does not suffer from the limitations faced by the conventional premise based PBX systems. However, since VoIP technology is still in its evolution stage, there are some minor problems to be sorted out.

One of the problems faced by a VoIP based system is the echoes. Echoes are caused by reflections of signals from the receiver to the sender. In a public telephone network, the delay between transmission of signals and echoes is less than 50 milliseconds, which is manageable. The echoes can be masked by the side tone a telephone generates. However, in case of packet networks the delay is more than 50 milliseconds. Here echo cancellation techniques need to be applied.

Providers of quality hosted PBX systems currently implement echo cancellers that follow the ITU standard G.165 specifications. These echo cancellers work by comparing the voice data that are received and transmitted by the packet network. Any similarities found is considered echo and promptly cancelled. Echoes that are transmitted from the telephone network to the packet network are removed using digital filters.

PBX phone system

Created by: accessdirect, Last modification: Tue 04 of Jul, 2006 (06:12 UTC) by e42006
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