The invention provides a layered modulation data communication systems characterized by numerous, asynchronous data transmitters operating on a power line. Data is modulated onto relatively low frequency subcarriers. Subcarriers are used to modulate carriers centered on a common frequency. The subcarriers...http://www.google.es/patents/US5581229?utm_source=gb-gplus-sharePatente US5581229 - Communication system for a power distribution line
Communication system for a power distribution line
