Power line carrier (PLC) is a communication technique that uses the existing power wiring (120 v,240,etc) to carry information .It is kind of "wireless" means of communication, because PLC technology can supersede the installation of dedicated wring in some applications. Various applications use PLC technology from power company equipment controlling to computer networking.

Typical frequency ranges used in power line communication is from 30 KHz to 150 KHz. In Europe mains power line communication is standardized at 1991 in EN50065-1 standard. EN 50065-1 is defined to standardize signaling on tow-voltage electrical installations in the frequency range 3 kHz to 148, 5 kHz. It gives general requirements, frequency bands and electromagnetic disturbances. The frequency range of EN 50065-1 is split to four different frequency bands. In the A-band, the carrier signal can be from 9 KHz to 95KHz where electricity suppliers and their licensees are permitted to communicate. Power lines can also be used for other applications. The C-band is for consumer use with air access protocol. This band goes from 125 KHz to 140KHz. Between the A-band and C-band is the B-band, used for consumer use without an access protocol so this band has some freedom of communication. Devices can interfere with one another and baby alarms use this band.

Above 150 KHz communication is prohibited in Europe. But in USA those higher frequencies are usable, popular "wireless" intercom systems for example operate at around 150 kHz - 500 KHz frequency range.The power line environment is hard environment for any communication. For example vacuum cleaners, hand-held drilling machines etcetera which use universal series wound motors generate a lot of impulse noise to power line. TV sets are a very common source of distortion. Light dimmers are also a source of mains noise. Switch mode power supplies use high frequency components, and usually a lot of tonal noise is generated. Everything can change over the frequency range, both the attenuation, phase response and noise level.
Three different techniques can be used for mains power !!rte communications With a PLY (Phase Looked Loop), the transmission could be performed with Amplitude Shit Keying, Frequency Shift Keying or Phase Shift keying. This is a well known technology that is inexpensive, but it's performance is limited.

A second technique is based upon Spread Spectrum with a correlates. Here a transmitted signal occupies a bandwidth considerably bigger than the minimum necessary to send the information so it has to be spread and modulated. The receiver has to know the transmitted pattern and the signal is sampled regularly. In practical applications the bandwidth available is a threshold because of the Senesce regulations. Low bandwidth increases susceptibility to signal distortion so it needs correction (TV-sets are a very common source of distortion).The third technique incorporates a DST working in a narrow band and using dual carrier frequency operation mode with impulse noise cancellation and an adaptive distortion correction mechanism.

Power line communication technology, which is the ability to transfer data over standard AC wiring, has existed for many years. However, the technology has not yet been widely adopted for data networking in homes and small businesses due to high cost, low speed, low functionality, and other barriers. There are numerous incompatible technologies trying to use the same AC wiring in a home or office in the same frequency range: the 2-30 MHz sweet spot, each targeting a specific application space.