Voice transmission over mixed packet- and circuit-switched networks

A discussion is presented of the effects of this additional delay on speech transmission over a mixed packet and circuit connection. The authors find that the additional delay introduced by a packet network remains within acceptable bounds for normal conversation, and thus does not degrade the service quality. However, the additional delay can cause severe problems because of the presence of echoes if proper suppression measures are not incorporated. They argue that echoes can be reduced to acceptable limits by using echo cancellation devices at the gateways between the packet network and the circuit-switched network, with no changes required in the circuit-switched part of the network