Question 15/XVII - Data transmission over intercontinental switched
telephone
connections
(Continuation of Question 15/XVII, 1985-1988)

Considering

(a) that approximately 55-60% of the intercontinental switched telephone
network trunks use satellite circuits;

(b) that a very small but growing percentage of these trunks are derived
from TASI and TDMA/DSI equipments;

(c) that the traditional echo suppressors are being replaced with new
echo cancellers,

what is the overall data transmission performance that might be expected
over intercontinental switched telephone network connections using
existing V-Series modems?

This study should include, inter alia, the following points:

1. the effects of echo, with variable delay, on the performance of V-
Series modems including items such as:

a) effect on circuit 109, etc.

2. the effects of TDMA/DSI, TASI and echo control devices (both echo
suppressors and echo cancellers) on duplex and half-duplex data
transmission, including items such as:

a) circuit 105 to 106 delay intervals;

b) effect on the training sequence of certain V-Series modems;

c) effect of echo suppressors and echo cancellers, including the
techniques of disabling the suppressors and/or cancellers, on two-wire
duplex modem operating at data signalling rates of 2400 bit/s and
greater.