Abstract: The present invention provides an adaptive filter. In one embodiment, the adaptive filter includes a solution vector generator that develops a sparse expression of an initial solution vector. In addition, the adaptive filter includes a proportionate normalized least mean squares (PNLMS) analyzer, coupled to the solution vector generator, that employs the sparse expression to converge upon at least one coefficient for the adaptive filter.

Abstract: The present invention provides an adaptive filter. In one embodiment, the adaptive filter includes a solution vector generator that develops a sparse expression of an initial solution vector. In addition, the adaptive filter includes a proportionate normalized least mean squares (PNLMS) analyzer, coupled to the solution vector generator, that employs the sparse expression to converge upon at least one coefficient for the adaptive filter.

Abstract: A fast affine projection adaptive filter capable of frequent parameter updating and fast convergence with low complexity. The invention mitigates affine projection adaptive filter complexity due to matrix inversion and the fact that a given excitation vector is weighted and summed into the adaptive coefficient vector many times. Embodiments of the invention achieve fast convergence through sample by sample updating and the exploitation of the shift invariant property of the excitation signal. Complexity is further reduced by a vector update procedure in which a given excitation vector is weighted and added into the coefficient estimate only once. Three illustrative embodiments are presented. The first of these is a relaxed adaptive filter, the second is an adaptive filter without relaxation and a third is an adaptive filter with suspended adaptation. The embodiments are presented in the context of electrical and acoustic echo cancellation.

Abstract: A subband echo canceler is disclosed in which blocks of real time are dynamically allocated to a plurality of generalized adaptive filters associated with a plurality of subbands in order to realize faster overall convergence to a desired impulse response. In one example, the real time block allocation is based on the weighted norm of the difference between the generalized adaptive filter coefficients from one sample period and an at least next subsequent sample period.

Abstract: In a private telecommunications network, a plurality of digital PBXs are interconnected via pairs of codecs. The codecs of each pair, or "tandem", are each operative to encode 64 kilobit/second (kbps) mu-law speech so as to compress it to 16 kbps speech for transmission to the other codec in the tandem. The latter is operative to thereafter decompress the 16 kbps speech back to 64 kbps. Each codec has a second mode of operation in which, rather than decode the encoded speech, it preserves the bits thereof in its own output signal. The codec transitions to this mode whenever it recognizes the presence of another codec on its high-bit-rate side of the connection. As a result, only one encoding/decoding cycle is performed across the connection, thereby minimizing the speech-coding-induced distortion and delay therein.