– D2 –
ND-71503(E) Rev.5.0
9papd001.fm
In 2000 IPS, the IP-PAD is used to relay the voice data on the IP network (on the IP packet) to the signals
(PCM data) on TDM. The IP-PAD is equipped with an echo canceller circuit to suppress the echoes that
influence calls. However, the echo canceller by itself cannot diminish echoes completely in some hardware
configuration that contains lines on the TDM side.
This appendix describes how to reduce echoes in 2000 IPS and the setup method.
COUNTERMEASURES FOR ECHO
IP-PAD Channel Automatic Selection Procedure
(1) About IP-PAD Channel Automatic Selection
The echo canceller installed in the IP-PAD card has a function that automatically learns (trains) the
characteristics of echoes that were generated, corrects the echoes, and stores the information.
However, one to two seconds are required for training and when the “actual call status” and “the echo
characteristics that were stored” do not match, echoes may occur for one to two seconds from the
start of a call. 2000 IPS reduces echoes by “storing the status of the echo characteristics and using
the result as the key for selecting the next channel” for each IP-PAD channel, using the echo canceller
circuit function.
In practice, the system classifies echo canceller training results into the models (levels) as indicated
STEP2 of “(2) Setting Up Procedure for IP-PAD Channel Automatic Selection” according to the
“connection destination on the TDM side” and stores the information for each IP-PAD channel.
These levels are organized in the sequence starting from the level with the characteristics closest to
those of the channel.
The level of each IP-PAD channel that has been stored is maintained unless the system or the IP-PAD
card is reset (When using Series 3100 software or later, the level of each IP-PAD channel that has
been stored is maintained even if the system or the IP-PAD card is reset).
After the levels of all the IP-PAD channels are set, the IP-PAD channel storing the level matching
with that of the connection destination is used in subsequent connection processing. If there is an IP-
PAD channel whose level has not been set, the channel is captured first and trained.
(2) Setting Up Procedure for IP-PAD Channel Automatic Selection
[Cautions and Reference Information]
• When the setup described in this section is not carried out or the channel setting distribution ratio
is incorrectly set, customers may experience echoes for 1 to 2 seconds until all the IP-PAD
channels are used. However, by continuing the operation, the value is set to the optimum value
automatically under the customer's use environment. (Actually, if the number of IP-PAD channels
is greater, the level matching probability increases so that the number of channels also influences
the echo occurrence frequency).
JANUARY/16/2004
COUNTERMEASURES FOR ECHO
CÔNG TY VIỄN THÔNG VIỆT PRO
Chuyên phân phối tổng đài NEC
http://vietpro.com.vn
