[Swprograms] CQ Magazine's take on the NTIA's BPL Report

[Richard Magdy <rsm@xxxxxxxxxxx>]

>From the CQ Magazine 4/28/04
http://www.cq-amateur-radio.com/


The National Telecommunications and Information Administration (NTIA)
has issued its long-awaited report on the interference potential of
Broadband over Power Lines (BPL). Despite a generally-glowing news
release, the report itself identifies significant interference risks
from BPL and concludes that the methods currently used for measuring
BPL noise levels are inadequate and that more study is needed on such
areas as ionospheric propagation of BPL signals.

The full report may be downloaded, either in full or chapter by
chapter, from the NTIA website at: <http://www.ntia.doc.gov/new.html>.
Our summary of the report's major findings follow.

CQ Summary of NTIA report to the FCC on BPL:

NTIA concluded?
1) ?that the methods currently used to measure noise levels and
interference potential are inadequate:   ?(A)pplication of existing
Part 15 measurement procedures for BPL systems results in a
significant underestimation of peak field strength. Underestimation of
the actual peak field strength is the leading contributor to high
interference risks. As applied in current practice to BPL systems,
Part 15 measurement guidelines to not address unique physical and
electromagnetic characteristics of BPL radiated emissions.? (Executive
Summary)

2) ? that noise levels must be measured from BPL-energized power lines
as well as the ?device? coupling the signal to the power lines: ?BPL
systems generate the highest electric field strength near the BPL
device for horizontal-parallel polarized signals. However, these
systems generate peak vertically-polarized field strength under and
adjacent to the power lines and at impedance discontinuities at
substantial distances from the BPL device.? (Executive Summary)

3) ? that interference to weak-to-medium strength signals is likely
out to 460 meters (1500 feet; more than 1/4 mile) from a BPL noise
source at ground level  and out to a 40-kilometer (25 mile) radius
from the signal source for an airplane at an altitude of up to 6
kilometers (approx. 20,000 feet): ?Interference to land vehicle, boat,
and fixed stations receiving moderate-to-strong  radio signals is
likely in areas extending to 30 meters, 55 meters, and 230 meters,
respectively, from one BPL device and the power lines to which it is
connected. With low-to-moderate desired signal levels, interference is
likely at these receivers within areas extending to 75 meters, 100
meters and 460 meters from the power lines ? (I)nterference to
aircraft reception of moderate-to-strong radio signals is likely to
occur below 6 km altitude within 12 km center of the BPL deployment.
Interference likely would occur to aircraft reception of
weak-to-moderate radio signals within 40 miles of the center of the
BPL deployment area. (Executive Summary)

4) ? that results of BPL tests and implementations in other countries
have been mixed: ?BPL apparently has been implemented with success in
some countries, while other countries have postponed implementation of
BPL systems until further interference studies are ? conducted. Still
others have withdrawn their approval for operation of BPL systems
after experiencing interference problems.? (Section 9, Summary of
Results). One example cited was that ?(d)uring an emergency exercise
of the Austrian Red Cross in May 2003, communication was massively
disturbed by (BPL), with interference levels exceeding the limits by a
factor of 10,000.? (Appendix B)

5) ? that more study is needed in several important areas, including
skywave propagation of BPL signals, that it will conduct further
studies and issue a report later this year: ?NTIA will complete a
Phase 2 study later this year that will assess the potential
interference risks due to aggregation and ionospheric propagation of
interfering signals from BPL systems; refine and apply BPL deployment
models; and evaluate the effectiveness of proposed Part 15 measurement
techniques.? (NTIA News Release)

NTIA is recommending more stringent measurement standards and
procedures, along with several interference mitigation techniques
some not mentioned in the NPRM  although it admitted that the nature
of power lines and of BPL would limit the effectiveness of some of
them. Additional recommendations are likely after the second phase of
the NTIA study is completed later this year. Acting NTIA Administrator
Michael Gallagher called the NTIA recommendations ?the technical
foundation for the responsible deployment of broadband over power
lines.?

CQ Opinion: It is clear from the results of the NTIA study that the
FCC?s rulemaking proposal is premature at best, and it would be
irresponsible of the FCC to go forward in enacting BPL rules before
the NTIA Phase 2 study is completed later this year. 




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