Subject: [NEXTEL-1] MUST READ- NTIA On BPL Phase I Report 04-413

From: [email-masked]
Date: Wed, 28 Apr 2004 02:39:44 -0400

NTIA BPL Phase I Report 04-413

April, 2004

EXECUTIVE SUMMARY

On April 23, 2003, the Federal Communications Commission (Commission or
FCC)
adopted a Notice of Inquiry (NOI) seeking information on potential
interference from Broadband over Power Line (BPL) systems and associated

changes that may be needed to accommodate BPL systems in Part 15 of the
Commission's rules.[1] As described in the NOI, "access" BPL systems
transmit Internet and other data at radio frequencies over neighborhood
power lines and use electrical outlets in BPL users' premises as data
ports
for computers and other devices. "In-house" BPL systems use indoor
wiring
for networking within the user's premises.

In its response to the NOI, the National Telecommunications and
Information
Administration (NTIA) described Federal Government usage of the 1.7-80
MHz
frequency range, identified associated interference concerns, and
outlined
the studies it planned to conduct to address those concerns.[2] NTIA
reviewed relevant studies and regulations in order to help refine the
scope
and priorities for its studies. NTIA parsed its planned studies into two

time phases, first addressing technical issues of the most immediate
importance. As reported herein, Phase 1 defines interference risks to
radio
reception in the immediate vicinity of overhead power lines used by
"access"
BPL systems. It also suggests means for reducing these risks and
identifies
techniques for mitigating local interference should it occur. Phase 2 of

NTIA's studies will evaluate the effectiveness of NTIA's Phase 1
recommendations and address potential interference via ionospheric
propagation of BPL emissions from mature large-scale deployments of BPL
networks.

NTIA reviewed the comments submitted in response to the NOI in order to
characterize existing and potential future BPL systems and deployments.
Simple BPL deployment models were addressed in the Phase 1 interference
risk
analyses. NTIA also developed more sophisticated deployment models for
use
in future studies.

NTIA summarized technical and operating parameters of over
fifty-nine-thousand (59,000) Federal Government frequency assignments in
the
1.7-80 MHz frequency range. This information may help operators of BPL
systems in development of BPL frequency plans. NTIA then defined
representative radio systems for consideration in interference analyses:

(1) a land vehicular receiver; (2) a shipborne receiver; (3) a receiver
using a rooftop antenna (e.g., a base or fixed-service station); and (4)
an
aircraft receiver in flight. Federal communications require exceptional
protection on frequencies amounting to about 5.4% of the 1.7-80 MHz
frequency range. NTIA will address the associated protection
requirements
in on-going studies.

NTIA executed three two-week measurement campaigns and used Numerical
Electromagnetic Code (NEC) software to characterize BPL signal radiation
and
propagation. These efforts revealed that 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. BPL systems generate peak field strength having
horizontal-perpendicular polarization at small distances (e.g., less
than 30
meters) from both the BPL device and power lines. Thus, measurements
intending to demonstrate compliance with the Part 15 field strength
limits
should not focus solely on the BPL device.

Using NEC, NTIA evaluated interference risks in terms of the geographic
extent of locations where interference may occur to radio reception at
four
frequencies used by outdoor, overhead BPL systems conforming to existing

Part 15 rules. 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.
Assuming that co-frequency BPL devices are deployed at a density of one
per
km2 within a circular area of 10 km radius, interference to aircraft
reception of moderate-to-strong radio signals is likely to occur below 6
km
altitude within 12 km of the center of the BPL deployment. Interference
likely would occur to aircraft reception of weak-to-moderate radio
signals
within 40 km of the center of the BPL deployment area. However, at two
of
the four BPL frequencies considered with the assumed power lines, NTIA
predicted smaller areas over which interference is likely.

Critical review of the assumptions underlying these analyses revealed
that
application of existing Part 15 compliance 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 do not address unique physical and
electromagnetic characteristics of BPL radiated emissions. Refining
compliance measurement procedures for BPL systems will not impede
implementation of BPL technology because BPL networks reportedly can be
successfully implemented under existing field strength limits.[3]
Accordingly, NTIA does not recommend that the FCC relax Part 15 field
strength limits for BPL systems. Further based on studies to date, NTIA
recommends several "access" BPL compliance measurement provisions that
derive from existing Part 15 measurement guidelines. Among these are
requirements to: use measurement antenna heights near the height of
power
lines; measure at a uniform distance of ten (10) meters from the BPL
device
and power lines; and measure using a calibrated rod antenna or a loop
antenna in connection with appropriate factors relating magnetic and
electric field strength levels at frequencies below 30 MHz.

NTIA suggested several means by which BPL interference can be prevented
or
eliminated should it occur. Mandatory registration of certain parameters
of
planned and deployed BPL systems would enable radio operators to advise
BPL
operators of anticipated interference problems and suspected actual
interference; thus, registration could substantially facilitate
prevention
and mitigation of interference. BPL devices should be capable of
frequency
agility (notching and/or retuning) and power reduction for elimination
of
interference. NTIA further recommends that BPL developers consider
several
interference prevention and mitigation measures, including: routine use
of
the minimum output power needed from each BPL device; avoidance of
locally
used radio frequencies; differential-mode signal injection oriented to
minimize radiation; use of filters and terminations to extinguish BPL
signals on power lines where they are not needed; and judicious choice
of
BPL signal frequencies to decrease radiation.
----------------------------------------------------------------------------

----

[1] Inquiry Regarding Carrier Current Systems, including Broadband over
Power Line Systems, Notice of Inquiry, ET Docket No. 03-104, April 28,
2003
("BPL Inquiry").

[2] Comments of the National Telecommunications and Information
Administration, BPL Inquiry, August 13, 2003.

[3] Comments of PowerWAN, Inc., BPL Inquiry, July 3, 2003 at 8-9;
Comments
of Amperion, Inc., BPL Inquiry, July 7, 2003 at 4.8; Reply Comments of
PowerComm Systems, Inc., BPL Inquiry, August 20, 2003 at 40.

NTIA BPL Phase I Report 04-413:
http://www.ntia.doc.gov/ntiahome/fccfilings/2004/bpl/index.html

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