Speech Coding

Abstract

Speech is the communication mechanism that distinguishes humans from lower animal forms and is an essential part of what allows man to function in civilization — our sophisticated ability to use language and communicate directly with one another via an acoustic channel. With the invention of the telephone by A. G. Bell, a major advance in human communication took place. Now we can communicate “in real-time” (not by writing letters or sending telegrams) with one another while geographically separated, perhaps around the world or in an aircraft or space vehicle. Of course the telephone was until recently based on analog communication: a simple modulation of an electric current in proportion to the instantaneous intensity of an acoustic signal. In recent decades digital communications emerged as a revolutionary new technology for the transportation of information and allowed us to develop new digital highways and superhighways carrying a variety of traffic such as data, video, and multiple channels of voice with greater reliability, cost effectiveness, privacy and security. Advances in error control and modulation techniques, including spread-spectrum and trellis-coded modulation allow reliable digital communication over radio channels that often suffer from interference, fading, and other degradations.

This work was supported in part by the National Science Foundation under grant NCR 8914741 and by Bell Communications Research, Inc., Bell-Northern Research, Inc., Rockwell International Corp., and the State of California MICRO program.