Adaptive differential pulse code modulation (ADPCM) systems
US4860313A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 21, 1987 |
| Grant date | Aug 22, 1989 |
| Priority date | — |
| Expiry date | Sep 21, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M3/042
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Apparatus and technique for ADPCM transmission of voiceband data at rates up to and including 9600 bits/s via an ADPCM system comprising an ADPCM transmitter receiving PCM encoded signals at an 8 KHz sampling rate and being operative to transmit data at a sampling rate of 6.4 KHz and a transmission rate of 5 bits per sample and an ADPCM receiver having apparatus for receiving the transmitted data from the ADPCM transmitter and being operative for providing PCM encoded signals at an 8 KHz sampling rate. The ADPCM transmitter includes an adaptive quantizer which is operative to provide an output signal I(n), employing a scale factor adapted according to a discrete function difference signal W(I) having a relationship to I(n) which typically is substantially different from that given in recommendation G.721 of the CCITT. The ADPCM transmitter also includes an adaptive predictor having predictor coefficients which are updated using a leak factor lower than that shown in recommendation G.721 of the CCITT.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.