Alcatel Canada Inc.

Ciena Corporation

Eric Verreault

Song Zhang

John C Fischer

A system improves reconstruction of real-time data in a packetized network. The system includes the following elements. A play-out buffer receives packets from the network. A playback element, coupled with the play-out buffer, retrieves packets from the play-out buffer and outputs data for the reconstruction of real-time data. A time adjuster alters the rate at which the data is output in accordance with the availability of the packets.

System and method for compensating packet delay variations

Method and apparatus detect voice activity for spectrum or power efficiency purposes. The method determines and tracks the instant, minimum and maximum power levels of the input signal. The method selects a first range of signals to be considered as noise, and a second range of signals to be considered as voice. The method uses the selected voice, noise and power levels to calculate a log likelihood ratio (LLR). The method uses the LLR to determine a threshold, then uses the threshold for differentiating between noise and voice.

Method and apparatus for detecting voice activity

A fast-converging, computationally simple, method for recognizing a single frequency tone or a sinusoid in a signal without prior knowledge of the tone frequency. The method employs a second order or higher auto-regressive model and includes: (a) sampling the signal at a constant sampling rate, and, for each sample, recursively determining a finite number of correlation coefficients using a time-reversed, exponentially weighted, future sliding equivalent of the signal, wherein the correlation coefficients are determined using pre-existing values of the correlation coefficients determined in a previous iteration, a current sample of the signal and at least two consecutively previous samples of the signal; (b) periodically determining at least the second auto-regressive coefficient modeling the signal using the correlation coefficients; and (c) recognizing the presence of the tone based on the value of the second auto-regressive coefficient.

Recognition of a single frequency tone

A method for recognizing tones in a signal in a telecommunication transmission uses samples of the signal to determine whether a tone of an expected frequency and wave shape is contained in the signal. If the method accurately predicts the value of the next sample, then a tone of the expected frequency and wave shape has been detected. Another method may be used to recognize sequences of tones comprising intervals with particular frequencies and durations. The method may be applied to the detection of initiation sequences for fax and modem transmissions, for example the ITU-T recommendation T.30 V.21 fax initiation sequence and the ITU-T recommendation V.25 modem transmission preamble. The method may be incorporated in a device for detecting modem or fax transmissions on a line and routing such modem and fax transmissions to a modem/fax relay. Thus the invention can be used with devices which provide voice compression by ensuring that fax and modem transmissions are not corrupted by being passed through the voice compressors.

Method and device for recognizing tones and sequences thereof

A relay device associated with each end point modem in a data communication network provides a system for transporting data over a communication channel employing voice compression. Each relay device exchanges relevant parameter information with its associated modem and with each other in order to negotiate compatible data transfer conditions. The protocol exchange between each relay and its associated modem will typically include the calculation of inter-loop delay values for echo cancellation and line probing for line equalization or bandwidth optimization. Supported data rates, modulation type and encoding information is also exchanged. The invention provides a system for full duplex transmission of data over modems while saving on bandwidth because of voice compression techniques.

Growing community of inventors

Ottawa, Canada

Eric Verreault