A recent article from Electronic Design magazine authored by Lou Frenzel discusses the continuing viability of Power-Line Communications (PLC) as a "core network technology." As pointed out by Frenzel, PLC is similar to wireless in that "you don’t have to install or otherwise fuss with the medium -- it’s just there." PLC uses available AC power mains as a networking communications channel. As such, residential electric meters and emerging home-area networking (HAN) technologies play heavily into the PLC equation. PLC superimposes communications data on the 50- or 60-Hz channels of the existing AC power mains. Frenzel notes while the concept of using the power line as a communications path has been attempted for decades with varying success, new standards and technologies have boosted PLC, at least in the eyes of more than a few networking chip and equipment vendors.
The article cautions that "while PLC is convenient and can save money, it [also] has its limitations." With PLC, issues such as noise and severe attenuation, common to any communications medium, must be accounted for. Communicated data first is used to modulate a carrier, which rides on the AC voltage. Amplitude shift keying (ASK) modulation was traditionally used for this purpose; more recently, frequency shift keying (FSK) has been used, due to its higher noise immunity. The medium can be unfriendly to higher frequencies and has a limited range of transmission. For higher speeds and improved noise mitigation, orthogonal frequency division multiplexing (OFDM) is increasingly being used in modern PLC systems.