An introduction to Broadband over Power Lines

Recent developments in technology have delivered chipsets designed for transmission of high speed data at Broadband speeds over existing power line infrastructure in a range of scopes including existing premises power wiring, the low voltage (LV) distribution network, and high voltage (HV) transmission network.

Power Line Communications (PLC) is not new; it has been in use for a very long time for electricity network protection, control, telemetry, voice and data communications, and demand side load management. Some of these applications are more broadly captured by the term Power Line Telecommunications (PLT).

Broadband over Power Lines (BPL) is a specialised form of PLT, it is designed to deliver high speed data services at Broadband speeds (greater than 256Kbps), usually delivered to the customer with an Internet Protocol (IP) interface and principally for access to the Internet.

It is a combination of the growing demand for Broadband data services and development of powerful digital signal processing capability on silicon chips that has encouraged BPL.

BPL achieves the high data rates by modulation of carriers at radio frequencies with the data, and transmission of that radio frequency energy on the power line media. BPL does not depend on radiation of radio frequency energy for its operation; BPL uses conduction on the metallic power line conductors to carry the modulated data signals from the sending BPL modem to the receiving BPL modem.

Power lines in their various forms are almost universally unsuitable media for transmission of radio frequency energy for a number of reasons, but most importantly to users of radiocommunications services, because of the leakage of substantial radiocommunications energy from the power lines and in-building wiring and the consequent risk of interference to radiocommunications services.

Current BPL technologies mainly use the radio spectrum from about 2MHz up to 30MHz to 80MHz (HF and VHF radio spectrum). BPL signals that leak from infrastructure are quite unlike any other form of radio frequency radiation, they are wideband (typically several MHz wide for individual links) with almost uniform power density across that bandwidth when in traffic, and they have the potential to interfere with a very large number of radiocommunications services used for diverse purposes.

BPL interference is a most serious threat to all radiocommunications users, and especially to Radio Amateurs because of their use of relatively weak signal operation, often limited only by external noise and interference.