Lucent Technologies' Microelectronics Group announced the first four-channel programmable communications semiconductor chip, combining echo cancellation and coding/decoding (codec) functions, that provides a ten decibel improvement in telephone line echo return loss performance compared to traditional echo cancellation methods. The system-on-a-chip solution, called the T8533, has the potential to substantially reduce total system costs compared to traditional network echo cancelers, while providing great flexibility and convenience.

Echo cancelers eliminate the annoying echo caused by network delays and by impedance mismatches at the "hybrid," the location where telephone lines connect to a digital voice network.

Lucent's integrated chip is the industry's first to comply with the International Telecommunications Union G.168 and G.712 standards for echo cancellation and codec technologies. The chip can be located on the telephone subscriber's premises; at the gateway to an Internet Services Provider's (ISP) Voice-over-Internet Protocol (VoIP) network; or at the point in a local exchange carrier's network where voice traffic is digitized or packetized.

Newer entrants, such as competitive local exchange carriers, may prefer to put echo cancellation closest to the point where voice traffic enters their networks: a digital loop carrier system or a telephone central office. This approach improves echo cancellation performance and can cost less, depending on configuration, than the typical $60 per line for network-based echo cancellation equipment. And the Lucent chip also has the potential to improve modem connection speeds.

ISPs that want to provide voice capability, and other carriers implementing VoIP technology, must add echo cancellation where voice traffic is packetized for transport over the network-at a modem, set-top or cable box, or network gateway.

"Designers of packetized voice networks can use the T8533 to eliminate echo before signal processing begins, while automatically adapting to all impedance conditions encountered on customers' lines," said Randy Pitts, an analog line card product manager with Lucent's Microelectronics Group. "And by integrating the echo cancellation function on the codec chip, the T8533 allows designers to use their digital signal processors for other functions, avoiding the need to develop or license the software to perform echo cancellation separately."

Network designers can easily place this echo canceler chip at the location closest to where the echo is generated, providing superior echo cancellation performance.

This product is very timely. With the increasing use of the Internet for voice traffic and the expense of current echo cancellation techniques not much has been done by ISPs to correct problems; also, with the demand for better and faster modem connections by Internet users, the existence of previous-generation cancellation circuits for echoes on conventional circuits restricts connection speeds; turning echo cancellation off, as happens with the T8533, will increase most users' connection speeds with V90 modems.

Meeting the new ITU recommendations for echo cancellation and codecs, this T8533 will be a rapidly adopted part; the cost per channel is dramatically lower than existing echo cancellation and the built-in codec will save even more expense for the users.