Broadband over power lines

Broadband over power lines (BPL) is a method of power-line communication (PLC) that allows relatively high-speed digital data transmission over the public electric power distribution wiring. BPL uses higher frequencies, a wider frequency range and different technologies compared to other forms of power-line communications to provide high-rate communication over longer distances. BPL uses frequencies that are part of the radio spectrum allocated to over-the-air communication services; therefore, the prevention of interference to, and from, these services is a very important factor in designing BPL systems. BPL is based on PLC technology developed as far back as 1914 by US telecommunications company AT&T. Electricity companies have been bundling radio frequency on the same line as electrical current to monitor the performance of their own power grids for years. More recently there have been attempts to implement access BPL, or the provision of internet services to customers via the grid. The prospect of BPL was predicted in 2004 to possibly motivate DSL and cable operators to more quickly serve rural communities. The high level of attenuation (or data signal loss) from access BPL power cables had two critical effects: First, a request to increase signal levels was opposed by groups within the radio community (DOD, FAA, FEMA, amateur radio) that had already documented significant interference. Second, the data rate was greatly reduced when a robust error correction code was added. Generally BPL is described as either In-House BPL to network machines within a building (including power line-based WiFi extenders), or Access BPL which will carry broadband Internet using power lines and allow power companies to monitor power systems. Because electric current and radio (data) signals oscillate at different frequencies they do not interfere with each other enough to significantly disrupt data transmission. Medium voltage (MV) lines carry generally up to a few tens of kilovolts, over a few kilometres between the electricity distribution stations and pole-mounted transformers.