Please any one can explain about how PLCC(power line carier communications) works?

Question

basic principle

Answer 1

The power lines act as the transmission lines for the communication signals (in addition to transmitting power).

Unfortunately power lines are not designed to carry RF efficiently, they are designed to carry power efficiently, so some compromises must be made when using these lines for comm.

The comm. transmitters and receivers are isolated from the high voltages (even 240 volts is 'high') by small valued capacitors, that represent high impedances to the 50 or 60 Hz, but low impedances to the RF.

Most RF carriers for PLCC that I have seen are in the neigborhood of several 10s of kHz up to a few 100 kHz. Carriers around 120 kHz are popular. This frequency proviced for enough distance, while allowing for a decent bandwidth for the information to be transmitted.

Once you have a carrier established (the receivers can reliably pick up the carrier), you can use most any form of modulation. The transmitters I have seen are for binary information, so a pulse-code modulation scheme is used, and certain receiver devices respond only to their codes, then act on the coded commands given. Here is a website that explains more, and a wiki article that is accruate:
http://www.x10.com
http://x10-mentor.com/
http://en.wikipedia.org/wiki/Power_line_communication

For longer distance comm. lower frequencies carry further, but the bandwidth for information is greatly reduced.

The IEEE has standards for high speed ethernet over power-lines but they are not widely used.

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Answer 2

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