V U Reddy is with the Electrical Communication Engineering Department, Indian Institute of Science. His research areas are adaptive signal processing, multirate filtering and wavelets, and multi-carrier communication.

Over the last 40 years, there has been continuous evolution in the design of voice-band modems - starting at the data rate of 300 bits per second in the late 1950s, a rate of 33,600 bits has been achieved in 1995. Realizing such high data rates over the voice-band of 3400 Hz is remarkable feet made possible by combining sophisticated techniques from three different disciplines, communication theory, signal processing and information theory. In this article, we begin with brief introduction of voice-band modems and then introduce basic principals of data transmission. 

Read full article (242  Kb)

Address for Correspondence
V Umapathi Reddy
 Electrical Communication Engineering 
Indian Institute of Science, Bangalore 560012, India. 
Email: vur@ece.iisc.ernet.in