Echo cancellation is a process used to remove echo from voice communications in order to improve voice quality on telephone calls. The process also reduces bandwidth consumption by eliminating echo traffic from the voice network. Unicoi Systems offers advanced solutions to enable telephony product developers to eliminate both acoustic and line echoes resulting from IP communications.
Acoustic echo is a type of echo common to the telephony world. Acoustic echo arises, for example, when a loudspeaker is placed near a microphone in a full-duplex communication application. In this case, the sound from the loudspeaker is picked up by the microphone, and transmitted back to the remote speaker. The remote speaker would then hear his or her voice distorted and delayed by the communications channel, which is called acoustic echo. Hands-free car communications systems, conference room speaker phones, and standard phones in hands-free or speakerphone mode are all subject to such acoustic echo problems.
An acoustic echo canceller (AEC) is used to prevent the transmission of acoustic echo back through the voice channel. The AEC on the receiving end must recognize the signal, then remove it by “subtracting” it from the signal, then transmitting the resulting signal through the voice channel.
Line echo arises during the conversion of a signal from 4-wire (network) to a 2-wire (telephone handset). An electric echo is created by the electrical circuitry attached to the wire lines. A portion of the signal from the far talker is coupled to the signal from the near-end talker and is returned to the far end. In networks with more than a 50-msec delay, including IP networks, line echo cancellation is critical to ensure quality voice communications.
As part of its Voice Processing Suite of software, Unicoi Systems offers both AEC and LEC solutions to dramatically improve the quality of voice communications over an IP network.
Acoustic Echo Canceller (AEC)
Unicoi’s Acoustic Echo Canceller (AEC) is designed to reduce acoustic echo that arises in communications products when a microphone and speaker are located relatively close together in an open field. Unicoi’s algorithm is proven, fully tested, and ready for integration.
G.168 Line Echo Canceller (LEC)
Unicoi’s G.168 Line Echo Canceller (LEC) is used to cancel echoes originating from 4-wire to 2-wire conversions in public switched telephone networks (PSTNs). LECs eliminate electric echo created by the electrical circuitry connected to the wire lines. This kind of echo is common for videophones, e-mailers, and other telecom devices with video codecs and vocoders, and ISDN telephones.
G.168-2000 Sparse Network Line Echo Canceller (LEC)
Unicoi’s G.168-2000 Sparse Network Line Echo Canceller (LEC) is ideal for gateways and central office equipment. The G.168-2000 can also be used as a full taps echo canceller if maximum echo path is less than 32 ms. The canceller's design allows trade-off between MIPS consumption and echo path tail for each channel separately, without any code modification.
Full-Duplex Speakerphone Algorithms
Unicoi’s Full-Duplex Speakerphone software is the highest quality full-duplex echo cancellation and voice clarity software for mobile phones. The Full-Duplex Speakerphone provides a combination of echo cancellation, noise cancellation, and sound enhancement along with sophisticated monitoring and control algorithms. The software is optimized to provide a high quality voice solution with minimal MIPS and memory usage. Unicoi’s voice software improves speech intelligibility, full-duplex operation, and speaker volume, enabling natural flowing communication for mobile video conferencing and hands-free speakerphone operation.
