PowerLine Technology | PowerLine Technology |
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The newest technology uses an enhanced form of orthogonal frequency-division multiplexing (OFDM) with forward error-correction, it is currently used in DSL technology, wireless distribution of television signals, and has also been adapted for IEEE's high rate wireless LAN Standards (802.11a and 802.11g). OFDM is a variation of the frequency-division multiplexing (FDM) used in phone-line networking. FDM puts computer data on separate frequencies from the voice signals being carried by the phone line, separating the extra signal space on a typical phone line into distinct data channels by splitting it into uniform chunks of bandwidth.
In the case of OFDM, the available range of frequencies on the electrical subsystem (4.5 MHz to 21 MHz) is split into 84 separate carriers. OFDM sends packets of data simultaneously along several of the carrier frequencies, allowing for increased speed and reliability. If noise or a surge in power usage disrupts one of the frequencies, the PowerLine chip will sense it and switch that data to another carrier. This rate-adaptive design allows PowerLine technology to maintain an Ethernet-class connection throughout the PowerLine network without losing any data. For example if a hi-voltage load appliance such as vacuum cleaner or hair dryer is turned on. The PowerLine device will then adapt to that change. By constantly adapting to the powerline medium, reliable communication can be guaranteed at every power outlet. PLC technology supports DES for encryption – security. This usually takes the form of an encryption key for each PowerLine unit. For Outdoor PowerLine security (PowerLine connectivity covering complete building/buildings or villages, the technology may not be same as above, it usually depends on vendor’s specific product. For example Telkonet has products which implement 256-bit Advanced Encryption Standard (AES) and is FIPS 140-2 compliant which is used mainly for government installations their products also support 3DES (triple DES) security. The next generation of product from the Homeplug Alliance will support the standard AES in the form of 128-bit encryption. |
