**SECTION 1**

**INTRODUCTION**

## Number range CHAPTERBACKGROUND

On April 23, 2003, the Federal Communications Commission (Commission or
FCC) adopted a Notice of Inquiry (NOI) seeking information on several
aspects of Broadband over Power Line (BPL) systems as well as associated
changes that may be needed to accommodate BPL systems in Part 15 of the
Commission\'s rules.[^1] The NOI described \"access\" BPL systems as a
backbone network of devices that use low and medium voltage electrical
power lines for transmission of broadband data to, from, and within the
geographic area of BPL network users.[^2] \"In-house\" BPL systems were
described as using low voltage wiring and electric power outlets for
networking within the user's premises, and for connecting end-user
devices to the access BPL network. Because BPL systems unintentionally
radiate emissions at radio frequencies, the NOI focused several
questions on Part 15 provisions that control the risk of interference to
radio reception. In its comments to the Commission, the National
Telecommunications and Information Administration (NTIA) summarized
Federal Government usage of the 1.7-80 MHz frequencies of prime interest
to BPL developers, identified associated interference concerns, and
outlined the studies it planned to conduct to address those
concerns.[^3]

Over five-thousand comments and replies were filed with the Commission
in response to the NOI. These comments provided substantial technical
details of BPL system design and operating features as well as analyses
of potential interference and the underlying factors that may cause
interference. Working independently of, but in coordination with the
Commission's Office of Engineering and Technology (OET), NTIA designed
its study approach to add substantially to the information filed in
response to the NOI. Considerations and findings of Phase 1 of NTIA's
study are reported herein. Phase 2 of NTIA's study will evaluate
potential interference from mature deployments of BPL systems via
ionosperic signal propagation and further assess risks of local
interference under various candidate BPL rules, including rules
suggested in NTIA's Phase 1 study.

## OBJECTIVES

The objectives of this technical study are to define interference risks
from operation of BPL systems under field strength limits and associated
compliance measurement procedures specified in Part 15 of the
Commissions rules, identify interference risk mitigation techniques that
may be employed by BPL manufacturers and system operators and, if
appropriate, recommend modifications to Part 15 provisions that will
reduce the interference risks.

## APPROACH

Phase 1 of NTIA's study addresses issues deemed most important to
formulation of a regulatory framework that would limit risks of local
interference from outdoor elements of BPL systems. NTIA reviewed
publications and comments submitted in response to the FCC NOI to
characterize existing and potential future BPL systems and deployments
(Section 2). NTIA also reviewed relevant domestic and foreign studies
and regulations to help refine NTIA\'s analysis approach and to prevent
unneeded redundancy (Section 3). Technical and operating parameters of
potentially affected Federal Government radiocommunications systems were
compiled and representative systems were identified for consideration in
the analyses (Section 4). NTIA analyzed BPL signal radiation and
propagation and summarized key findings from NTIA\'s measurement and
computer modeling efforts to date (Section 5). The report discusses
environmental Radio Frequency (RF) noise levels insofar as ambient noise
is an important factor in the evaluation of interference. Recognizing
these considerations and assuming that BPL systems comply with existing
Part 15 provisions, NTIA evaluated the risks of interference to
representative Federal Government systems (Section 6). NTIA then
developed recommendations for clarification and modification of existing
Part 15 compliance measurement procedures to reduce the potential for
underestimating the peak field strength (Section 7). NTIA identified
techniques for preventing and mitigating BPL interference (Section 8).
NTIA applied the results of these studies in recommendations regarding
the Part 15 field strength limits and compliance measurements relevant
to BPL systems, identified areas where further investigation by BPL
proponents may lead to means for reducing interference risks and
facilitating rapid elimination of interference, and outlined the focal
points for NTIA's Phase 2 studies (Section 9).

## SCOPE

This study considers BPL systems utilizing fundamental frequencies in
the 1.7 - 80 MHz frequency range.[^4] In this Phase 1 study, NTIA
defines risks of interference from BPL systems to local radio reception
assuming BPL systems comply with existing Part 15 field strength limits
and compliance measurement procedures. Issues not addressed in Phase 1
include the following:

-   Regulatory framework, including the suitability of Part 15 for
    accommodation of BPL.

-   Aggregation of interfering signals from BPL systems via ionospheric
    propagation. This is of concern insofar as skyward emissions from
    hundreds of co-frequency BPL systems deployed over a large area
    theoretically could produce a significant composite interfering
    signal level at a very distant receiver. This phenomenon would not
    be possible until BPL technology is widely deployed.

-   Potential BPL emissions at frequencies other than the fundamental
    frequencies employed by the BPL system. In other words, BPL
    out-of-band emissions and intermodulation products were not a focal
    point.

-   Radio systems typically used by non-federal entities, except to the
    extent that their technical and operating parameters are similar to
    those of Federal Government systems.

-   BPL transmission over indoor low voltage wiring, noting that this is
    a focal point of the Commission\'s studies.[^5]

-   Potential interference or damage to BPL systems from local radio
    transmissions.

> NTIA's Phase 2 study will assess the interference risks due to
> aggregation and ionospheric propagation of interfering signals from
> BPL systems. NTIA has developed BPL deployment models in the Phase 1
> study to support the analysis of BPL signal aggregation and
> propagation (Appendix F); however, these models will be refined and
> applied in the Phase 2 Study. In its Phase 2 study, NTIA will also
> evaluate the effectiveness of proposed Part 15 measurement refinements
> and provide additional clarifications as appropriate.

[^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]: The Commission further expanded the definition of access BPL to
    include high voltage electrical power lines carrying greater than
    40,000 Volts. *See Amendment of Part 15 regarding new requirements
    and measurement guidelines for Access Broadband over Power Line
    Systems,* Notice of Proposed Rule Making, ET Docket No. 04-37,
    February 23, 2004 ("BPL NPRM"), at ¶32.

[^3]: Comments of the National Telecommunications and Information
    Administration, BPL Inquiry, August 13, 2003.

[^4]: The BPL Inquiry identified the 1.7-80 MHz frequency range to be of
    principal interest for BPL operations. BPL Inquiry at ¶15.

[^5]: Comments of the Office of Engineering and Technology (*Initial
    results of FCC tests related to in-house Power Line Communications
    (PLC))*, BPL Inquiry, September 16, 2003.