Access BPL - Computer Definition
An access, or local loop, technology that runs over medium voltage (MV) power lines in the power utilities distribution networks. At utility substations, the high voltage (HV) lines, which run at 165,000 765,000 volts, are stepped down to medium voltage, which runs at up to 7,200 volts, for the distribution network (see Figure A-1). At the substation, the BPL provider typically terminates a fiber optic network connection in a device that accomplishes the optoelectric conversion process. Inductive couplers wrapped around the power lines, without touching them, serve both as injectors for downstream transmissions and as extractors for upstream signals. The injectors and extractors share a common frequency band on the MV power lines for both upstream and downstream communications through the use of a version of orthogonal frequency division multiplexing (OFDM) specially tailored for powerline environments, the radio frequency (RF) carrier supporting the communications signals can share the same line with the electrical signals. The BPL signal uses the frequency band between 2 MHz and 80 MHz, and repeaters must be spaced at intervals of 300 meters or so. Extractors remove downstream signals from the distribution power lines just ahead of the remote transformers that step the voltage down from MV to the low voltage (LV) level of 110/220 volts used within the premises. The connection to the premises can be over the LV lines, or via IEEE 802.11 wireless local area network (WLAN) technology, also known as Wi-Fi. Within the premises, communications can make use of InHouse BPL or more traditional technologies. See also FOTS, In-house BPL, local loop, OFDM, RF, transformer, volt, voltage, Wi-Fi, and WLAN.