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Chapter 9. X-10, CEBus, HomePlug

Chapter 9. X-10, CEBus, HomePlug

Power lines and wall plugs can be found in every room of a residence. Building construction codes mandate that a power plug be accessible from anywhere in a room within the distance of the power cord of an electrical device. There are usually many more power line wall plugs than telephone wall jacks at most indoor places. Establishing communication links over an indoor power line is almost equivalent to wireless because every stationary communication device is usually connected to the power plug for powering. On the other hand, trying to establish communication links over a power line is not that easy. The power line provides a very hostile communication environment with noises generated by local electrical appliances and collected over the radio wave. The signal attenuation over a power line connection can be severe as a result of random branches of electrical cables and low impedances of connected appliances. These impedances can also be time-variable if appliances are turned on and off manually and if embedded control electronics such as dimmers are used for consumption regulation. Wall plugs in most residences are also randomly wired with two different phases causing additional attenuation for communication devices operating at relatively low frequency bands.

Among many indoor power line–based communication systems, X-10 has found applications mainly for home automation, where lights and other appliances can be turned on and off via short command packets transmitted over the power line. CEBus is an industry standard intended for the same home automation and entertainment information distribution applications. CEBus standards define multiple transmission systems over existing home wiring (including telephone wiring, coaxial cable, and power line), radio frequency, and infrared as well as a control application language called CAL. The power line–based CEBus physical layer has found good applications in commercial buildings as well as over the wiring of commercial trucks for relaying information from different parts of a vehicle. Most recently, many attempts have been made to carry broadband data traffic, equivalent to that of Ethernet, over the indoor power line. After numerous field tests and trials, a HomePlug specification has been established for a power line–based transmission system capable of a throughput of more than 10 Mbps.


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