Digital transmission of acoustic signals over a noisy communication channel
First Claim
1. A method for error control coding of digital data, the method comprising the steps of:
- dividing said digital data into a plurality of bit vectors, including a first bit vector;
encoding said bit vectors with error control codes, to produce encoded bit vectors, including an encoded first bit vector;
generating a modulation key from at least said first bit vector; and
using said modulation key to modulate at least some of said encoded bit vectors.
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Abstract
The performance of digital communication over a noisy communication channel is improved. An encoder combines bit modulation with error control encoding to allow the decoder to use the redundancy in the error control codes to detect uncorrectable bit errors. This method improves the efficiency of the communication system since fewer bits are required for error control, leaving more bits available for data. In the context of a speech coding system, speech quality is improved without sacrificing robustness to bit errors. A bit prioritization method further improves performance over noisy channels. Individual bits in a set of quantizer values are arranged according to their sensitivity to bit errors. Error control codes having higher levels of redundancy are used to protect the most sensitive (highest priority) bits, while lower levels of redundancy are used to protest less sensitive bits. This method improves efficiency of the error control system, since only the highest priority data is encoded with the highest levels of redundancy. The effect of uncorrectable bit errors is reduced by adaptively smoothing the spectral parameters in a speech decoder. The amount of smoothing is varied depending upon the number of errors detected during the error control decoding of the received data. More smoothing is used when a large number of errors are detected, thereby reducing the perceived effect of any uncorrectable bit errors which may be present.
87 Citations
20 Claims
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1. A method for error control coding of digital data, the method comprising the steps of:
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dividing said digital data into a plurality of bit vectors, including a first bit vector; encoding said bit vectors with error control codes, to produce encoded bit vectors, including an encoded first bit vector; generating a modulation key from at least said first bit vector; and using said modulation key to modulate at least some of said encoded bit vectors. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of decoding digital data of the type encoded by an encoding method comprising the steps of:
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dividing said digital data into a plurality of bit vectors, including a first bit vector; encoding said bit vectors with error control codes, to produce encoded vectors, including an encoded first bit vector; generating a modulation key from at least said first bit vector; and using said modulation key to modulate at least some of said encoded bit vectors, to produce modulated encoded bit vectors; said method of decoding comprising the steps of; dividing the digital data to be decoded into a plurality of code vectors, said code vectors corresponding to said modulated encoded bit vectors; generating a demodulation key from at least one of said code vectors; using said demodulation key to demodulate at least some of said code vectors, to produce demodulated code vectors; and error control decoding at least some of said demodulated code vectors. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification