DSI TRANSMISSION SYSTEM AND METHOD OF ALLEVIATING BACKGROUND NOISE SIGNAL CONTRAST IN DSI TRANSMISSION SYSTEM

摘要

MITIGATION OF NOISE SIGNAL CONTRAST IN A DIGITALSPEECH INTERPOLATION TRANSMISSION SYSTEMAbstract of the DisclosureA DSI transmission system is described in whichnoise signal contrast is mitigated by transmitting not only activechannels but also channels which carry background noise, theresolution of the background noise channels being varied independence upon the number of channels transmitted. In thedescribed system, the DSI transmission is effected in superframeseach of which consists of an overhead information frame and aplurality of digital message frames. The overhead informationframe contains a word indicating the transmission status of eachchannel during the superframe, a code indicating the number of bitsof each digital message, and maximum segment value information bitsfor each of the active channels which are transmitted using nearlyinstantaneous companding. Each of the remaining frames contains adigital message in respect of each active channel. Remainingspace in these frames is occupied by digital messages in respect ofthe background noise channels, which are allocated to the frames bycyclic assignment and are transmitted using compact PCM encoding.For each superframe, active and background noise channels aredetermined using speech, echo, and off-hook detectors, and thenumber of bits of each digital message in the superframe isdetermined in dependence upon the total number of active andbackground noise channels.- i -