**APPENDIX F**

**NTIA PHASE 2 STUDY BPL DEPLOYMENT MODELS**

**F.1 INTRODUCTION**

The potential interference from mature large-scale deployments of BPL
networks due to signal aggregation and propagation will be addressed in
NTIA's Phase 2 study. NTIA's BPL deployment models[^1] encompass three
scenarios where the effects of aggregated BPL emissions are of interest.
Differing mainly in geographic size and the potential interference
impact to licensed radio service receivers, these three deployment
models are:

-   the neighborhood deployment model, in which the radio receiver
    antennas are at heights lower than the power lines (*e.g.*, a land
    mobile vehicle antenna);

-   the antenna coverage area deployment model where radio receiver
    antennas are located above power lines (*e.g.*, atop buildings and
    masts and on aircraft) having a view of one or more neighborhoods;
    and

-   the more expansive regional deployment model, from which BPL signals
    could arrive at a receiver via ionospheric (\"skywave\")
    propagation.

The objective for NTIA\'s family of BPL deployment models is to define
potential physical layouts of BPL systems having various architectures
that, when coupled with realistic cross-sections of radiation,
propagation and signal aggregation, will aid in predicting the total
levels of co-frequency BPL signals at various radio receiver antenna
locations. Each model is parametric (*i.e.*, several factors will be
varied), recognizing that many factors are variables that may greatly
influence the predictions. For example, the geographic densities of
emitting elements within the successively larger neighborhood, coverage
area and regional geographic domains are expected to be highly
influential, and the degree of influence will be determined in
sensitivity analyses. At one extreme, we have the present limited
deployment of experimental systems. Once BPL services are commercially
available, there could be a rapid ramp up in deployment densities in all
three geographic domains. In the long term, but at different times in
the neighborhood, coverage area and regional domains, the deployment
densities will converge on maximum levels. The interference risks in
each geographic domain will concurrently increase over time. Variants of
the BPL deployment parameters will be based on information filed in
response to the BPL NOI as well as NTIA\'s research.

**F.2 NEIGHBORHOOD DEPLOYMENT MODEL**

The neighborhood deployment model addresses the case of a land mobile
radio operating inside a BPL service area. The land mobile radio may be
within 10 meters of the nearest active BPL device and one block away
from another simultaneously active, co-channel BPL device.[^2] An
initial analysis is presented in Section 6, assuming the case of a
single co-channel BPL device operating under existing Part 15 rules. The
worst case which will be considered for the neighborhood deployment
model would consist of a land mobile receiver operating in the presence
of three co-channel BPL systems, two operating over power lines in close
proximity to the receiver and one operating on a power line located one
block away from the receiver. Considering the manner in which separate
MV power lines are deployed and the coupling between adjacent power
lines, it is unlikely that co-channel emissions from more than 3 BPL
devices will aggregate significantly at any given land mobile receiver
location.

The characteristics for this model are depicted in Figure F.1 and are as
follows:

-   Victim HF receiver with whip antenna located 2 meters above the
    ground;

-   Two BPL injectors mounted on the same power pole, located no closer
    than 3 meters lateral to the victim receiver and 10 meters above the
    ground (location of receiver will be varied);

-   A co-channel BPL extractor at 10 meters above the ground, located
    100 meters away from the above injectors at a 45° angle. This is
    consistent with a power line feeding an adjacent street.

\(a\) Horizontal View

Figure F-1: Assumed Aggregate Neighborhood Deployment Scenario

![](media/image1.wmf){width="5.4375in" height="3.9722222222222223in"}(b)
Overhead View

Figure F-1 continued: Assumed Aggregate Neighborhood Deployment Scenario

The transmit duty cycle for the two BPL injectors, T~i~, and for the
extractor, T~e~, are parameters for the model.

The output of the neighborhood deployment model is a probability that
three co-channel BPL devices, having the assumed physical orientation
relative to the victim receiver as noted above, will be transmitting
simultaneously. Using this result along with an emissions model for BPL
devices attached to power lines, an analysis will be performed to
estimate the percentage of local land mobile vehicle locations where
harmful, co-channel interference may occur.

**F.3 ANTENNA COVERAGE AREA DEPLOYMENT MODEL**

Another case of interest is the mobile-service, aircraft or
fixed-service base station receiver operating in close proximity to a
fully deployed BPL service area. Receiving antennas for these stations
typically can have unobstructed or lightly obstructed views of many more
co-channel BPL devices that might affect a land mobile receiver in the
neighborhood environment. HF base stations are frequently located in
rural areas where the level of man-made noise is expected to be low;
however, power lines are present in this environment. Over the years, a
number of these remote locations have seen residential areas develop
nearby, potentially resulting in an increase in the noise floor seen by
the receiver. In some cases, HF stations are located in or near
residential communities.[^3] Aircraft and fixed stations generally are
variously located anywhere.

The coverage area deployment model assumes that the radio station is
located within or adjacent to a BPL service area and that the radio
antenna has variously obstructed and unobstructed views of the BPL
service area. The characteristics of the BPL deployment are described in
the following section on the regional deployment model, the main
difference being the size of the BPL deployment area being considered. A
single county with a predominately suburban population density will be
used to arrive at the density of BPL devices in the coverage area
deployment model. In addition, the coverage area model assumes that the
entire county is covered by the BPL service. This is a reasonable
assumption since the housing density will be sufficiently high to
provide good incentive for the electrical utility to make this service
widely available to all its electricity customers.

The output of the coverage area deployment model will be a density of
BPL devices and their locations relative to the radio station. As will
be further described in the regional deployment model, the BPL service
area will be composed of cells operating on the same or different
frequency bands with variable frequency reuse patterns. This will be
used to develop a model of aggregated emissions from the BPL service
area as seen by the radio receiver.

**F.4 REGIONAL DEPLOYMENT MODEL**

In order to assess the aggregated electrical field strength arising from
future, wide-scale deployments of BPL systems, a regional deployment
model for BPL networks is proposed herein. The model characterizes the
number and distribution of active BPL devices across the entire United
States. Among other things, the results of this model will be used to
characterize the effect BPL systems have on distant federal
communication systems due to any increase in background noise level as a
result of ionospheric propagation of unintentional BPL radiated
emissions. This will also help address concerns that other countries may
have with deployment of BPL systems in the United States.

The approach taken in developing the regional BPL deployment model is
to:

-   characterize the number and distribution of households served by the
    nation's electrical power distribution network based on U.S. Census
    Bureau data;

-   estimate the number of BPL devices based on the density of
    households and the BPL device capacities and range, as provided by
    the BPL proponents in their NOI comments and reply comments;

-   factor in the characteristics of the various BPL signals such as
    frequency ranges used, bandwidths, network access mechanisms, and
    frequency reuse; and

-   estimate the percentage of these households that will end up being
    served by BPL service providers (i.e., market penetration), based on
    subscriber growth rates of competing technologies, such as cable and
    DSL.

**F.4.1 Regional Deployment Model Description**

As of 2000, there were 105.5 million occupied households in the United
States,[^4] and over the past 10 years, the number of households has
been growing at an annual rate of approximately 1.4%.[^5] The U.S.
Census data provides the number of households (H~cty~) and the area
(A~cty~) for each of the 3,142 counties and independent cities in the
United States, with a breakdown by urban and rural classifications. The
housing density within individual counties may vary widely, with a mix
of urban, suburban, and rural areas. An individual county may also have
large, unpopulated areas where no MV lines are present.

In Phase 1 of the NTIA study, development of the regional deployment
model focuses initially on urban area deployment of BPL. Here, the
housing densities are sufficient to support a large number of MV power
lines in a given area, and access to the Internet backbone is widely
available. Closely spaced BPL network cells, and cells sharing the same
geographic location but separated by power line phase, will be
considered in estimating the extent of frequency reuse in urban areas.
The regional deployment model will be expanded in NTIA's Phase 2 studies
to include the rural BPL environment, where the wide variability of
rural housing density, MV power line density, and the availability of
access to the Internet backbone will be considered.

The regional deployment model makes some simplifying assumptions to
reduce data base and computational complexities and a number of the
model's characteristics have been parameterized to enable sensitivity
analysis of those characteristics.

**F.4.2 Density and Distribution of Households**

The average housing density (ρH) for each county is then given by

ρH~cty,u~ = H~cty,u~ / A~cty,u~ urban households / sq. km. (F.1)

To account for the growth in the number of households over "y" years,
the urban housing densities will be scaled by a factor of (1+ rate)^y^.

**F.4.3 Density and Distribution of BPL Devices**

The regional deployment model estimates the number of BPL devices for
the urban areas of each county.

**F.4.3.1 Injectors**

Within urban areas, where there are a substantial number of power line
branches and distribution transformers, the range of BPL injectors
without requiring repeaters, "r~u~", is expected to be up to ½ to 1
kilometer (¼ to ½ mi).[^6] Thus, the number of injectors is given by

I~cty,u~ = A~cty,u~ / r~u~^2^ urban injectors (F.2)

**F.4.3.2 Repeaters**

The transmission ranges of BPL repeaters are expected to be the same as
those for injectors. Like injectors in adjacent BPL cells, repeaters are
generally expected to transmit using different frequencies to minimize
the levels of co-channel interference. In addition, repeaters have two
BPL transmitters, whereas injectors have only one BPL transmitter. BPL
service providers may vary the size of each cell to account for the
availability of fiber or T1 access to the Internet backbone.

From the standpoint of maximizing the utilization of the available
bandwidth, it is more advantageous for BPL service providers to deploy
injectors instead of repeaters wherever possible. In urban areas where
there is ready access to the Internet backbone, the number of repeaters
in a given area is assumed to be negligible as compared to the injector
quantity for the area under consideration.

**F.4.3.3 Extractors**

BPL extractors (also referred to as repeaters in System #3) are
typically located at each LV transformer. The parameter "x" defines the
number of households per distribution transformer and ranges from 3 -- 8
households per LV distribution transformer.[^7] The resulting quantity
of extractors is

EX~cty,u~ = H~cty,u~ / x urban extractors (F.3)

For System #2, a WiFi™ (or other non-BPL) interface to the subscribers'
homes is used instead of the wired BPL interface implemented in the
other system architectures. Therefore, the extractors for System #2 have
only one BPL transmitter associated with them.

**F.4.4 Other Factors**

**F.4.4.1 Frequency Range**

In comments responding to the NOI, the BPL vendors and service providers
stated widely varied frequency ranges that they propose using for BPL
service.[^8] The frequency range assumed for the regional deployment
model is 1.7 -- 80 MHz, although BPL devices will not be uniformly
distributed in frequency (another variable in the models).

**F.4.4.2 Frequency Reuse**

In order to minimize signal degradation associated with co-channel
interference, System #2 uses different frequency bands for upstream and
downstream communications, and for adjacent BPL devices. Communication
with the subscribers' homes is not accomplished using BPL. System #1
uses one frequency band for all access BPL devices and in-house BPL
devices use another band. System #3 uses the same frequency band for all
devices. Assuming that an injector serves one BPL cell, the number of
frequency bands used in a cell is shown in Table F.1.

Table F-1: BPL Frequency Bands per Cell

+--------------------------------------+-------------------------------+
| **Architecture**                     | **Number of Bands**           |
+--------------------------------------+-------------------------------+
| System #1                            | 2                             |
|                                      |                               |
|                                      | (1 Access + 1 In-House)       |
+--------------------------------------+-------------------------------+
| System #2                            | 2                             |
|                                      |                               |
|                                      | (Access)                      |
+--------------------------------------+-------------------------------+
| System #3                            | 1                             |
|                                      |                               |
|                                      | (Access & In-House)           |
+--------------------------------------+-------------------------------+

In the regional deployment model, System #1 is assumed to reuse the same
two frequency bands for each injector and its associated extractors. The
model will scale the number of simultaneously active System #1 BPL
devices in an area by a factor of ½.

In an urban environment, System #2 is expected to utilize separate
frequencies for the injectors in adjacent cells. A minimum of 3 cells is
required to implement frequency reuse in a cellular transmission
architecture.[^9] Assuming that the frequency range used for BPL
services is 1.7 -- 80 MHz, an urban deployment of System #2 devices (2
simultaneous Access transmissions per cell) would result in a maximum
duplex bandwidth of approximately 26 MHz per cell (i.e., 78 MHz ÷ 3
cells). The regional deployment model will scale the number of
simultaneously active System #2 BPL devices by a factor of 1/(2\*3) =
1/6.

System #3 is assumed to reuse the same frequency band for every cell;
therefore, the regional deployment model will assume simultaneously
active System #3 BPL devices with no scaling.

A final point about frequency reuse is that with 3-phase MV power lines,
three co-channel cells could share the same geographic location,
assuming they can tolerate any coupling that occurs between the
conductors of each phase.

**F.4.4.3 Media Access**

Based on BPL vendor comments, the media access protocols for their
systems permit transmission by only one device at a time per cell in a
given frequency band.[^10] For System #1, one access BPL device and one
in-house BPL device are active at a time. For System #2, one BPL
injector and one BPL extractor may be transmitting at a time within a
cell, with each transmission using separate frequency bands. For System
#3, one BPL device (injector or extractor) will normally be transmitting
at a time; however, it appears that the media access mechanism is
CSMA-CD and there is potential for multiple simultaneous co-channel
transmissions in the same cell, especially during peak use periods.

**F.4.4.4 BPL Market Penetration**

There are currently almost 20 million households in the United States
with a broadband connection to the Internet. Of these, approximately 6.5
million are xDSL customers and 12 million are cable customers. The
growth rate for these services this past year is approximately 2.5
million customers per year for xDSL and 4 million customers per year for
cable.[^11]

The regional deployment model assumes an insignificant number of BPL
customers in 2003, and an initially linear growth rate parameter that
has a range of 2 to 4 million households per year. In addition to the
growth of the overall BPL market, the model assumes an equal market
share for each of the three types of BPL systems described above. The
percentage of market share for each type of BPL system will be used to
scale the number of BPL devices (injectors, repeaters, extractors)
simultaneously using individual frequency bands throughout the United
States.

**F.4.5 Regional Model Output**

The output of the regional deployment model is the expected number and
distribution of BPL transmission sources, and the number of simultaneous
frequencies in use, based on the expected overall BPL market share over
a specified number of years. In NTIA's Phase 2 studies, these results
will be used in conjunction with a HF skywave propagation model to
determine the increase in noise floor resulting from wide-scale
deployment of BPL systems.

[^1]: The deployment models presented herein are preliminary. Comments
    from BPL proponents and opponents will be considered as the models
    are finalized and applied in NTIA's Phase 2 study.

[^2]: NTIA personnel have observed and measured signals from two DSSS
    BPL injectors co-located on a single power pole, isolated by using
    two different phases of the same run of three phase power lines.
    Located one block away was a DSSS BPL repeater (extractor) on the
    third phase line. Even though all three of these devices may be
    coupled to different, adjacent phase lines of the same MV
    distribution network serving a community, they would be operating
    co-channel and may be transmitting at the same time. Later NTIA
    measured two independent co-channel signals for this case and the
    composite emission had about twice the power of the individual
    emissions.

[^3]: Comments of the Federal Emergency Management Agency on Broadband
    Over Power Line Implementation, BPL Inquiry, December 4, 2003 at
    ¶10.

[^4]: County and City Data Book: 2000, U.S. Census Bureau, Table B-3.

[^5]: Meyers Group Report on Household Growth, by Bryan Glasshagel,
    <http://www.meyersgroup.com/analysisobjects/householdgrowth.asp?ProductCategory=NHMR>.

[^6]: Reply Comments of PowerComm Systems, Inc., BPL Inquiry, August 20,
    2003, ("PowerComm Reply Comments") at 16; Comments of Ambient
    Corporation, BPL Inquiry, July 7, 2003 at 5.

[^7]: Comments of Current Technologies, LLC, BPL Inquiry, July 7, 2003,
    ("Current Technologies Comments") at 4, 6.

[^8]: Comments of Ameren Energy Communications, Inc., BPL Inquiry, July
    7, 2003 at 12; Comments of Amperion, Inc., BPL Inquiry, July 7, 2003
    at 4; Current Technologies Comments at 17; Comments of Electric
    Broadband, BPL Inquiry, July 7, 2003 at 4; Comments of Main.net
    Communications, Ltd., BPL Inquiry, July 7, 2003 at 4; PowerComm
    Reply Comments at 4; Comments of PowerWAN, Inc., BPL Inquiry, July
    3, 2003 at 1; Comments of Progress Energy, Inc., BPL Inquiry, July
    7, 2003 at 2.

[^9]: Mobile Cellular Communication Systems, William C. Y. Lee,
    McGraw-Hill Book Company, 1989 at 52 -- 53.

[^10]: Reply Comments of Ameren Energy Communications Inc., BPL Inquiry,
    Aug 20, 2003 at 13; Current Technologies Comments at 15; Reply
    Comments of Current Technologies, LLC, BPL Inquiry, Aug 20, 2003 at
    12; Reply Comments of Main.net Communications LTD., BPL Inquiry,
    August 20, 2003 at 3.

[^11]: FCC News, *Federal Communications Commission Releases Data On
    High-Speed Services For Internet Access*, June 10, 2003,
    <http://hraunfoss.fcc.gov/edocs_public/attachmatch/DOC-235274A1.doc>.