User Manual

Chapter 2 - MAIN FEATURES, PROTOCOL AND QoS
1QDF10134AAP-SYD-FCC Issue 03
4Mbit - Draft 05
2-11 of 2-14
5) Session type - VoIP
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
SDA
SDA
Ethernet
Switch
Ethernet
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 SDA and a PSTN customer. Echo is
generated at the 2 wire-4 wire hybrid in the PSTN customer’s line card and has to be
cancelled.