Lucent Technologies Inc.

Herbert B Cohen

Lujing Cai

Mingjie Wang

Nuri Ruhi Dagdeviren

Richard Rogoszewicz

A modem monitor for monitoring full duplex communications comprises one receiver for each data stream and an echo canceler for canceling 'far' echo. Prior to each receiver decoding the data stream it is designed to monitor, it replicates an echo expected to be found in its received data stream from a sample of each of the other predecoded data streams. The echo canceler then subtracts the expected echo from the received data stream to remove all far echoes caused by the other data streams. The echo canceled data stream is then decoded. The monitor can also include a data communications network interface and a sample rate converter operating with the PSTN for converting from the network transmission rate to the data transmission rate.

Apparatus and method for monitoring full duplex data communications

A method is presented to enable high speed transmission in the upstream channel from a customer's modem to a PCM modem connected to the public switched digital network. The upstream channel is equalized by having the client modem send a known training sequence in the upstream direction to the server modem. The server modem calculates the cross-correlation between the known training sequence and the sequence as actually received from the client modem. The cross-correlation is then multiplied by the known auto-correlation of the training sequence to produce a model of the channel response. The channel response is then reported to the client modem so that it may adjust its pre-equalizer to construct the signal that the client modem will thereafter send in the upstream direction.

Method of upstream channel modeling for PCM modem

For use with an analog communications device coupled to an analog interface of a digital telecommunications network, the analog interface having signal conversion values corresponding to an n-level symbol table, a system and method that dynamically selects a constellation of symbols from the n-level symbol table, and a modulator/demodulator ('modem') employing the system or the method. The system includes (1)a logic circuit that selects m symbols, m being less than or equal to n, from the n-level symbol table, the m symbols being a function of the signal conversion values, and (2) a transmission circuit adapted to transmit data identifying the m symbols to a remote device digitally-coupled to the digital telecommunications network, the data allowing the analog communications device and the remote device to communicate with a common symbol table dynamically adapted to the signal conversion values of the analog interface of the digital telecommunications network.

Growing community of inventors

Morganville, NJ, United States of America

Herbert B Cohen