Will BPL Interfere With In-Plant Radio Networks?
Broadband over power line (BPL) is a technology that allows Internet data to be transmitted over utility power lines. In order to utilize BPL, a subscriber installs a small modem similar to DSL or cable service, and plugs it into any ordinary AC wall outlet in any room. The modem then provides an Ethernet connection to a computer or home network. Radio signals carrying digital data are coupled onto the power line at a local utility substation in the area. These signals travel along the power grid and are then distributed into homes or offices. BPL has also been tested and proven to be capable of providing Voice over IP (VoIP) and Video on Demand (VoD) services. BPL is also known in some countries as PLT. It can also be referred to as Broadband Power Line Carrier, or just PLC.
Bob Landman, of H & L Instruments has been monitoring this technology and its potential effect on process and SCADA networking. The most significant problem so far has been that BPL appears to have real interference issues with amateur radio, and potentially, with 892.xx radio networks, such as WiFi, WiMax, and Zigbee.
Landman posted on the SCADAnet mailing list today this communique from ARRL (Amateur Radio Relay League, the controlling body of amateur radio):
==>NEW ARRL PETITION SEEKS TO RESOLVE BPL STANDOFF
Not all BPL systems are created equal. Some have far less potential to
interfere with Amateur Radio than others. That’s the rationale behind a
petition the ARRL filed this week, asking the FCC to modify the Part 15 BPL
rules it adopted a year ago and sharply reduce BPL’s interference potential.
In exchange, the League said it would withdraw its still-pending Petition
for Reconsideration in the BPL proceeding, ET Docket 04-37. The ARRL says
its suggested rule amendments–which take into consideration recent
advancements in BPL technology–will “resolve unsettled but substantial
interference issues” affecting Amateur Radio and other HF users.
“It is no longer the case that all BPL systems inherently radiate high
levels of RF energy on amateur allocations on overhead medium-voltage power
lines,” the ARRL said. “Thus, not all BPL architectures have similar
potential for harmful interference to the Amateur Radio Service (and to
other licensed services). Some have inherently greater potential for
interference, as currently configured, than others.”
The problematic systems, the League said, are those that make use of the HF
spectrum on unshielded overhead medium-voltage lines. BPL systems such as
those using DS2 or Main.net technology that lack fixed, permanent notches in
the ham bands, the ARRL noted, have been among those involved in
interference cases. “As detailed in ARRL’s Petition for Reconsideration in
this proceeding, “this has resulted, in field tests and in deployments, in
substantial, extremely difficult-to-resolve incidents of interference to
fixed and mobile Amateur Radio facilities,” the League said.
The ARRL said the FCC “has assisted not at all, or imperceptibly, in these
cases, and the BPL system operator has either been uncooperative or unable
to resolve the interference.”
The League said its proposed additional regulations would permit those BPL
architectures that are “benign,” while discouraging “first-generation
interference-causing BPL configurations, unless the latter modify their
systems in certain minor aspects.” A “benign” system, the ARRL noted, would
not apply HF signals on overhead medium-voltage lines and would include
fixed, permanent notches in the amateur bands.
Among the several BPL system designs that implement BPL without creating
harmful interference to amateur operations, the ARRL specifically cited the
Motorola Powerline LV BPL system. Motorola’s system doesn’t use
medium-voltage power lines, and it has been designed to preclude
interference to ham radio and other licensed services.
For several weeks, ARRL and Motorola have cooperated in a BPL test stand at
W1AW that has operated successfully without significant interference to
Amateur Radio. The League also cited BPL systems by Current Technologies,
IBEC and Corridor Systems as being among those that meet the additional
requirements it’s proposing. Current Technologies’ BPL deployment in the
Cincinnati, Ohio, area, for example, does not make use of medium-voltage
lines for transmission of HF signals and utilizes the HomePlug notching
protocol. Limited testing, the ARRL said, indicates that, as a result, the
interference potential “is minimal relative to Amateur Radio facilities.”
Incorporating three elements into the BPL rules adopted last year would
essentially resolve all issues that the ARRL and the Amateur Service have
with access BPL, the League said: Prohibiting all access BPL systems from
using Amateur Radio allocations (except the five channels at 5 MHz, which
the current HomePlug system architecture does not notch); prohibiting access
BPL systems from using HF bands on medium-voltage power lines; and measuring
signal decay from access BPL systems using a more accurate 20 dB/decade
extrapolation factor rather than the 40 dB/decade factor the current rules
Adopting its proposals, the League said, would result in a more robust
product that meets the Commission’s stated goals of accommodating BPL as an
additional broadband option while protecting licensed radio services. “The
present BPL rules achieve the first of the goals, but they are woefully
inadequate to meet the second,” the ARRL said.
“It is the Commission’s obligation to recognize and utilize this opportunity
and to amend its rules to protect licensed radio services for the first time
in this proceeding,” the ARRL concluded. “It can be done without significant
system redesign by any BPL provider.”
A copy of ARRL’s petition is on the League’s Web site.
While ARRL’s issue is strictly protection of the ham bands, it is clear that because of the propinquity of high voltage lines and transmission mains to most industrial process plants this is a significant potential problem for the growth of radio networks for process automation as well as SCADA and amateur radio.
What do YOU think?