Mitigation of noise signal contrast in a digital speech interpolation transmission system
First Claim
1. A method of mitigating noise signal contrast in a multi-channel digital speed interpolation transmission system, comprising the steps of:
- determining each channel which is active and each channel which carries background noise;
transmitting the active channels; and
transmitting the channels which carry background noise with a resolution which is dependent upon the number of channels transmitted and which is reduced as said number is increased.
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Abstract
A DSI transmission system is described in which noise signal contrast is mitigated by transmitting not only active channels but also channels which carry background noise, the resolution of the background noise channels being varied in dependence upon the number of channels transmitted. In the described system, the DSI transmission is effected in superframes each of which consists of an overhead information frame and a plurality of digital message frames. The overhead information frame contains a word indicating the transmission status of each channel during the superframe, a code indicating the number of bits of each digital message, and maximum segment value information bits for each of the active channels which are transmitted using nearly instantaneous companding. Each of the remaining frames contains a digital message in respect of each active channel. Remaining space in these frames is occupied by digital messages in respect of the background noise channels, which are allocated to the frames by cyclic assignment and are transmitted using compact PCM encoding. For each superframe, active and background noise channels are determined using speech, echo, and off-hook detectors, and the number of bits of each digital message in the superframe is determined in dependence upon the total number of active and background noise channels.
21 Citations
14 Claims
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1. A method of mitigating noise signal contrast in a multi-channel digital speed interpolation transmission system, comprising the steps of:
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determining each channel which is active and each channel which carries background noise; transmitting the active channels; and transmitting the channels which carry background noise with a resolution which is dependent upon the number of channels transmitted and which is reduced as said number is increased. - View Dependent Claims (2, 3)
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4. In a multi-channel digital speech interpolation transmission system, the improvement comprising:
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means for determining each channel which carries background noise, in addition to each channel which is active; and means for transmitting, in addition to each active channel, each channel which carries background noise with a resolution which is dependent upon the number of channels transmitted and which is reduced as said number is increased.
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5. A digital speech interpolation transmission system for transmitting a plurality of digital signal channels via a transmission link, comprising:
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means for forming superframes each comprising a plurality of multi-bit frames; means for determining, for each superframe, which channels are active and which channels carry background noise (b.n. channels); and means for transmitting, in a normal loading situation, a digital message in respect of each active channel in each of said frames of the superframe and digital messages in respect of the b.n. channels in said frames of the superframes, the transmitting means comprising; means for determining for each superframe, in dependence upon the numbers of active channels and b.n. channels for that superframe, numbers of bits for the digital messages of each active channel and each b.n. channel; means for producing said digital messages, each of the respective number of bits, from the digital signals of each active channel and each b.n. channel; and means for producing and transmitting, for each superframe, digital information relating to the transmission status of each channel, and the determined number of bits of each of the digital messages, in that superframe. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification