Adaptive differential pulse code modulation system with transmission error compensation
First Claim
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1. A communications system that compensates for transmission errors, comprising:
- A) input means for accepting an analog signal;
B) encoding means, connected to the input means, for encoding the analog signal according to adaptive differential pulse code modulation techniques to generate an encoded output, the encoded output comprising at least one codeword; and
C) compensation means, connected for communication with the encoding means, for accepting the encoded output and for limiting a range of amplitudes of the encoded output to generate a compensated output based on the encoded output.
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Abstract
A codeword forcing technique is applied which provides gradual degradation of an audio output during fading such that analog degradation in a fading signal environment is simulated. The system may be used in conjunction with digital cordless telephones where gradual degradation of a 32 Kbit/s ADPCM signal is obtained by indirectly detecting a transmission bit error rate, The bit error rate detection is accomplished by sensing the occurrence of an invalid all-zero code, Codeword forcing techniques are then applied to compensate for the inaccurate transmission and associated noise level,
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20 Claims
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1. A communications system that compensates for transmission errors, comprising:
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A) input means for accepting an analog signal; B) encoding means, connected to the input means, for encoding the analog signal according to adaptive differential pulse code modulation techniques to generate an encoded output, the encoded output comprising at least one codeword; and C) compensation means, connected for communication with the encoding means, for accepting the encoded output and for limiting a range of amplitudes of the encoded output to generate a compensated output based on the encoded output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A process for compensating for transmission errors in a communications system, comprising the following steps:
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A) receiving an analog signal; B) converting the analog signal to a digital signal by performing adaptive differential pulse code modulation on the analog signal; C) transmitting the digital signal in the form of at least one codeword; D) estimating a bit error rate of the transmitted digital signal; E) comparing the estimated bit error rate of the transmitted digital signal to a threshold value; F) narrowing a range of amplitudes of the transmitted digital signal if the estimated bit error rate is greater than the threshold value; and G) performing adaptive differential pulse code modulation decoding on the transmitted digital signal. - View Dependent Claims (10, 11, 12)
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13. A communications system that compensates for transmission errors, comprising:
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A) input means for accepting an analog signal; B) encoding means, connected to the input means, for encoding the analog signal according to adaptive differential pulse code modulation techniques to generate an encoded output, the encoded output comprising at least one codeword; C) transmission means, connected to the encoding means, for transmitting the encoded output; D) a communications channel, connected to the transmission means; E) reception means, connected to the communications channel, for receiving the encoded output; F) compensation means, connected to the reception means, for limiting a range of amplitudes of the encoded output to generate a compensated output based on the encoded output; and G) decoding means, connected to the compensation means, for decoding the compensated output according to adaptive differential pulse code modulation techniques, to generate an analog output. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification