Echo controller with compensation for variable delay networks

摘要

The present invention provides a method of and system for controlling and effectively reducing the echo introduced in telephone connections over variable delay networks such as LAN/WAN networks. The invention includes estimation of the round-trip user-to-user delay in the telephone connection. This estimation can be made in a number of different ways, including using timestamps in existing data packets according to a Real-Time Protocol (RTP) or a Real-Time Control Protocol (RTCP) and by sending timestamps in data packets according to an Internet Control Message Protocol (ICMP). The invention further includes determination of an echo control target for the telephone connection based upon the estimated user-to-user delay. This target represents the total amount of echo control required to limit the probability of objectionable echo to less than a predetermined threshold. The amount of echo control required increases as the length of the estimated user-to-user delay increases. The invention further includes determination of the minimum amount of signal-dependent loss required to supplement the acoustic echo cancellation in order to reach the determined echo control target. Then, in the invention, the determined amount of signal-dependent loss is applied to the telephone connection to effectively reduce echo based upon the estimated user-to-user delay.