The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 18, 1986
Filed:
Oct. 31, 1983
Jagannath P Agrawal, Lafayette, LA (US);
Subramaniam S Iyer, Sunnyvale, CA (US);
University of Southwestern Louisiana, Lafayette, LA (US);
Abstract
Speech bit rate reduction by robbing, e.g. periodically not transmitting, a percentage of speech data samples in a communication system employing differential pulse code modulation (DPCM) or adaptive differential pulse code modulation (ADPCM). To overcome feedback interference introduced in the code by sample robbing, a robbed sample is replaced by its estimate so that the coding process continues in a normal manner. The estimate is established on the basis of autocorrelation statistics of the speech data samples. At the receiving end of the communication system, the robbed sample is estimated by the same process and re-estimated again using delayed interpolation after one period of delay. The technique is particularly useful where graceful degradation is desired under heavy traffic loading on the data channel, and is found most beneficial when the bit rate is about 24kb/s or lower where a relatively larger quantizing noise masks the interpolation noise introduced by sample robbing. The technique also facilitates handling speech packet loss in packet-networks. The signal-to-noise ratio was improved up to 3 db using a DPCM coder and 1.5 db using an ADPCM coder.