Abstract: A system for updating filter coefficients for use with an echo canceller, a related method for updating filter coefficients and an echo canceller including the system or the method. In one embodiment, the echo canceller has a nonadaptive filter and an adaptive filter, the nonadaptive filter having nonadaptive filter coefficients and configured to develop a nonadaptive error signal as a function of the nonadaptive filter coefficients, and the adaptive filter having adaptive filter coefficients and configured to develop an adaptive error signal as a function of the adaptive filter coefficients. The system includes a monitoring subsystem configured to monitor a quality of the nonadaptive and adaptive error signals and a selection subsystem configured to select one of the nonadaptive and adaptive filter coefficients for use by the nonadaptive filter based on the quality of the nonadaptive and adaptive error signals.

Abstract: A method and apparatus to perform a real-time drift correction of a remote handset's local oscillator in a digital cordless telephone. The remote handset begins in a standby (sniff) mode. The remote handset periodically wakes from a sleep mode and goes into a normal link verification mode. Once in the link verification mode, the remote handset enters a time division duplexing (TDD) mode and attempts to establish a link with a base unit based on the timing of the TDD data frame. After the remote handset establishes a link with the base unit, the remote handset requests a security word from the base unit. Upon receiving the requested security word, the remote handset determines if the requested security word matches a security word of the remote handset. The remote handset implements a software frequency adjustment of its local oscillator. Once per frame, the remote handset enters a timing recovery state where the current state of the frame is compared with a previous state.

Abstract: The present invention provides a system for updating filter coefficients for use with an echo canceller, a related method for updating filter coefficients and an echo canceller including the system or the method. In one embodiment, the echo canceller has a nonadaptive filter and an adaptive filter, the nonadaptive filter having nonadaptive filter coefficients and configured to develop a nonadaptive error signal as a function of the nonadaptive filter coefficients, and the adaptive filter having adaptive filter coefficients and configured to develop an adaptive error signal as a function of the adaptive filter coefficients. In an exemplary embodiment, the system includes a monitoring subsystem configured to monitor a quality of the nonadaptive and adaptive error signals. The system further includes a selection subsystem configured to select one of the nonadaptive and adaptive filter coefficients for use by the nonadaptive filter based on the quality of the nonadaptive and adaptive error signals.

Abstract: Residual echo components resulting from an adaptive echo canceler are minimized by employing a subband echo suppressor. The residual echo components are minimized by individually, controllably adjusting the echo suppressor attenuation level in each of the subbands to gradually attenuate echo peaks having a magnitude lower than a clipping threshold with the magnitude of the attenuation increasing for residual echoes of decreasing magnitude. Additionally, the threshold of suppression engagement is dynamically matched to the signal gain in the echo path for each subband. If the signal gain in a subband is high (strong echo), the suppressor must attenuate residual echo peaks in the subband of higher energy to maintain a constant quality of service.

Abstract: A subband acoustic echo canceller for a telecommunications teleconferencing room is equiped with subband adaptive filters and filter taps associated with said subbands. A data store is provided containing a weight list for controlling allocation of the filter taps among the subbands. An optimum tap profile as determined by the weights is a composite of room acoustic impulse response and weighting adjustments based on one or more measures of perceived human acoustic sensitivity experienced by far-end users. An active periodic adjustment of the weights responsive to detection of sibilant energy in the incoming path further improves echo cancellation. Active measurement and updating of the room acoustic impulse response provides further refinement.