Her Majesty the Queen in Right of Canada As Represented by the Minister of Industry Through the Communications Research Centre Canada

Her Majesty the Queen in Right of Canada, As Represented by the Minister of Industry Through the Communications Research Centre

Ken Gracie

John Lodge

Andrew Hunt

Stewart N Crozier

Paul Guinand

A method for lost speech samples recovery in speech transmission systems is disclosed. The method employs a waveform coder operating on digital speech samples. It exploits the composite model of speech, wherein each speech segment contains both periodic and colored noise components, and separately estimates these two components of the unreliable samples. First, adaptive FIR filters computed from received signal statistics are used to interpolate estimates of the periodic component for the unreliable samples. These FIR filters are inherently stable and typically short, since only strongly correlated elements of the signal corresponding to pitch offset samples are used to compute the estimate. These periodic estimates are also computed for sample times corresponding to reliable samples adjacent to the unreliable sample interval. The differences between these reliable samples and the corresponding periodic estimates are considered as samples of the noise component. These samples, computed both before and after the unreliable sample interval, are extrapolated into the time slot of the unreliable samples with linear prediction techniques. Corresponding periodic and colored noise estimates are then summed. All required statistics and quantities are computed at the receiver, eliminating any need for special processing at the transmitter. Gaps of significant duration, e.g., in the tens of milliseconds, can be effectively compensated.

Method for recovery of lost speech data

Methods of reduced-complexity max-log-APP processing are disclosed for use with Turbo and Turbo-like decoders. The invented methods of decoding are derived from max-log-APP processing and significantly lower the processing required for decoding convolutional codes by eliminating a portion of the calculations conventionally associated with max-log-APP processing. The disclosed embodiments provide simplified methods of metric combining based on determining the bits of an MLSE sequence with different alternative approaches. Also disclosed is an early stopping method that uses the reduced-complexity max-log-APP decoder to reduce the average number of decoding operations required by an iterative Turbo decoder.

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Ottawa, Canada

Ken Gracie