Voice-band modem: A device to transmit data over telephone networks

Abstract

Over the last 40 years, there has been continuous evolution in the design of voice-band modems-starting at a data rate of 300 bits per second in the late 1950s, a rate of 33,600 bits per second has been achieved in 1995. Realising such high data rates over the voice band of 3400 Hz is a remarkable feat, made possible by combining sophisticated techniques from three disciplines, communication theory, signal processing and information theory. In this article, we briefly describe certain advanced ideas, which led to data rates very close to the channel capacity limit, established by Shannon.