Power line communications

A Power Line Communication Tutorial Challenges and Technologies
Phil Sutterlin and Walter Downey Echelon Corporation 4015 Miranda Ave. Palo Alto, CA 94304 USA Phone: [phone] FAX: [phone] Keywords: Communication, Spread Spectrum, Digital Signal Processing Abstract - This paper reviews the sources of attenuation, noise and distortion encountered when communicating over AC power wiring. Various technologies which have been used to address these challenges, such as spread spectrum and digital signal processing, are then examined in light of the known channel conditions.

Introduction
While the idea of sending communication signals on the same pair of wires as are used for power distribution is as old as the telegraph itself, the number of communication devices installed on dedicated wiring far exceeds the number installed on AC mains wiring. The reason for this is not, as one might think, the result of having overlooked the possibility of AC mains communication until recent decades. In the 1920’s at least two patents were issued to the American Telephone and Telegraph Company in the field of “Carrier Transmission Over Power Circuits”. United States Patents numbers 1,607,668 and 1,672,940, filed in 1924 show systems for transmitting and receiving communication signals over three phase AC power wiring. Others have suggested that what was required for power line communication to move into the main stream was a commercialized version of military spread spectrum technology. It has been suggested that this is what was needed in order to overcome the harsh and unpredictable characteristics of the power line environment. Commercial spread spectrum power line communication has been the focus of research and product development at a number of companies since the early 1980’s. After nearly two decades of development, spread spectrum technology has still not delivered on its promise to provide the products required for the proliferation of power line communication.