System Description

Chapter 2 - MAIN FEATURES, PROTOCOL AND QoS
MCIL -WIPLL-SDN_R2_00 Marconi Communications Ltd. 2-11 of 2-12
2.5. Echo Management
Packet based systems are likely to introduce more delay (and variable) than circuit
switched systems. Increased delay could present quality problems with time
bounded services such as voice communication.
SPR
1
PSTN
IP Network
Base Station Site
1
n
BSR
10BaseT
10BaseT
H-E
GW
GW
International
Traffic
Ethernet
SDTA
SDTA
Ethernet
Switch
Ethernet
RJ-11
RJ-11
Figure 2-2: Echo Control
As can be seen from Figure 2-2, echo becomes an issue when a voice call is
established between a customer connected to an SDTA and a PSTN customer. Echo
is generated at the 2 wire-4 wire hybri
be cancelled. Note that a voice call between two customers, both connected to an
SDTA, will not suffer from echo because the SDTA customers effectively become
4-wire customers.