**Before the**

**Federal Communications Commission**

**Washington, D.C. 20554**

In the Matter of )

)

Revision of Part 15 of the Commission's )

Rules Regarding Ultra-Wideband ) ET Docket No. 98-153

Transmission Systems )

# **NOTICE OF INQUIRY**

**Adopted: August 20, 1998 Released: September 1, 1998**

By the Commission:

**Comment date: \[insert date 75 days from publication in Federal
Register\]**

**Reply comment date: \[insert date 105 days from publication in Federal
Register\]**

# **INTRODUCTION**

Number range level0Number range level1Number range level2Number range
level3Number range level4Number range level5Number range level6Number
range level71. The Commission is initiating this inquiry on its own
motion to investigate the possibility of permitting the operation of
ultra-wideband (UWB) radio systems on an unlicensed basis under Part 15
of its rules. Such systems could provide an improved method for
providing radar applications where precise distance resolution is
required and for providing covert voice or data communications that
overcome multipath problems. Through this inquiry, we are seeking input
to help us evaluate UWB technology and what standards and operating
requirements are necessary to prevent interference to other users of the
radio spectrum. Upon review of the responses to this inquiry, we will
determine whether to propose any changes to the rules.

## **BACKGROUND**

2\. Part 15 of the rules permits the operation of low power radio
frequency devices without a license from the Commission or the need for
frequency coordination.[^1] The technical standards for Part 15 are
designed to ensure that there is a low probability that these devices
will cause harmful interference to other users of the spectrum.[^2]
Intentional radiators, *i.e.*, transmitters, are permitted to operate
under a set of general emission limits[^3] or under provisions that
allow higher emission levels in certain frequency bands.[^4] Intentional
radiators generally are not permitted to operate in certain
sensitive[^5] or safety-related bands, designated as restricted
bands,[^6] or in the bands allocated for television broadcasting.[^7]
The measurement procedures for determining compliance with the technical
requirements for Part 15 devices are provided or referenced within the
rules.[^8]

3\. Recently, we have learned of advances in the development of UWB
technology. UWB radio systems typically use extremely narrow pulse
(impulse) modulation or swept frequency modulation that employs a fast
sweep over a wide bandwidth. Because of the type of modulation employed,
the emission bandwidths of UWB devices generally exceed one gigahertz
and may be greater than ten gigahertz.[^9] In some cases, these pulses
do not modulate a carrier. Instead, the radio frequency emissions
generated by the pulses are applied to an antenna, the resonant
frequency of which determines the center frequency of the radiated
emission. The bandwidth characteristics of the antenna will act as a
low-pass filter, further affecting the shape of the radiated signal.

4\. UWB technology can be employed for radar systems, permitting the
precise measurement of distances, the detection of objects within a
defined range of distances, or high resolution imaging of objects that
are behind or under other surfaces. When combined with appropriate
modulation techniques, UWB devices also may be used for communications
purposes, such as the transmission of voice, control signals, and data.
Most of the current equipment designs that have been investigated by the
Commission contain high level, distinct spectral lines concentrated near
the center of the emission. However, we recognize that, as the
technology advances, this type of modulation is capable of spreading the
signal levels over such a wide bandwidth that the emissions would appear
to be similar to background noise. For such systems, the amount of
energy appearing in any particular band should be extremely low. Such
signals are not easily detected or intercepted.

5\. The current Part 15 rules pose two primary obstacles to the
implementation of UWB technology. First, the wide bandwidth of UWB
systems emissions may result in their fundamental emissions[^10] being
transmitted into the TV broadcast and in restricted frequency bands
which is prohibited under the Part 15 rules. It is difficult to avoid
operating in these bands as the ultra-wide bandwidth is intrinsic to the
operation of UWB equipment. Second, the current emission measurement
procedures specified in our Part 15 rules were developed for narrowband
systems and may be inappropriate for, and pose unnecessary restrictions
to, UWB technology. For example, the measurement procedures require the
application of a pulse desensitization correction factor.[^11] This
correction factor will cause UWB systems to exceed the peak emission
limits currently permitted under Part 15.[^12]

6\. The Commission now has before it three requests for waivers of the
Part 15 rules to permit the operation of UWB systems.[^13] U.S. Radar
Inc., on January 28, 1998, filed a Petition for Waiver to permit the
operation of a surface penetrating radar system that could be used to
detect buried objects and objects hidden behind walls.[^14] On February
2, 1998, Time Domain Corp. filed a Petition for Waiver to permit systems
that would be used by public safety personnel for communications,
location determination and high resolution imaging radar.[^15] On April
14, 1998, Zircon Corporation also filed a Request for Waiver to permit
radar systems that would be used by the construction industry to detect
objects hidden behind walls and other building materials.[^16] These
petitions for waiver will be addressed separately from this proceeding.

## **DISCUSSION**

7\. We believe that UWB technology has unique attributes that could lead
to a wide variety of new beneficial uses that may be in the public
interest. Radar systems are currently being developed to detect buried
objects such as plastic gas pipes or hidden flaws in airport runways or
highways. Other radar systems would be used as fluid level sensors in
difficult-to-measure situations such as oil refinery tanks and other
storage tanks. Public safety personnel have expressed a desire for radar
systems that can detect people hidden behind walls or covered with
debris, such as from an earthquake. Public safety personnel also have
expressed a need for UWB communications systems that can operate
covertly. These communications systems could also be employed by heavy
industrial manufacturers to overcome multipath[^17] and
machinery-generated radio noise.

8\. The Commission has a long history of facilitating the introduction
of new technologies under Part 15 of its rules. For example, in the
mid-1980's the Commission provided new rules for spread spectrum
technology that led to the growth of an industry and a wide array of
products. In the past few years, the Commission has amended Part 15 to
provide for unlicensed personal communication service devices,
unlicensed national information infrastructure devices and millimeter
wave technology. We are initiating this Notice of Inquiry to determine
what, if any, changes to our rules may be appropriate to facilitate the
development of UWB technology and what standards and operating
requirements are necessary to prevent interference to other users of the
radio spectrum. We seek information on the topics identified below to
help us determine whether to propose any changes to our Part 15 rules.

9\. [Applications and general characteristics]{.underline}. Currently,
two general types of UWB systems have been presented to the Commission:
radar systems and communications systems that can be used for voice,
data and control signals. These products are comparable to spread
spectrum modulated systems. Like spread spectrum systems, UWB systems
are able to employ gain processing on the received signal and can
operate in the presence of higher powered transmission systems without
receiving interference. UWB systems also may have a low potential,
relative to the total peak powers employed, for causing harmful
interference to other users of the spectrum if the transmitted signal is
spread over a wide bandwidth which may result in a relatively low
spectral power density. We invite comments on the following issues:

 What types of UWB devices can we expect to be developed?

 What are the frequency ranges and bandwidths expected to be used by
UWB devices?

 What are the expected total power levels and spectral power densities,
peak and average, of UWB devices?

 What are the expected or desired operating distances?

10\. [Regulatory treatment]{.underline}. We understand that UWB systems
will operate at very low spectral power densities, producing noise-like
signals. Further, it appears that UWB systems will operate over very
short distances.[^18] Because of this, it appears appropriate to provide
for UWB technologies under Part 15 of the rules. We invite comments on
whether it would be appropriate to apply our Part 15 rules to UWB
technologies.

 Are there certain types of UWB devices or applications that should be
regulated on a licensed basis under some other rule part? If so, which
rule parts?

 If provisions are made for UWB technology under Part 15, how should we
define UWB technology?

11\. [TV broadcast and restricted bands]{.underline}. Part 15 designates
certain sensitive and safety-related frequency bands as restricted
bands.[^19] Only spurious emissions[^20] not exceeding the general
emission limits are permitted within these restricted bands or, with few
exceptions, within the frequency bands allocated for TV broadcasting.
However, it is difficult, if not impossible, for UWB systems to avoid
placing fundamental emissions within the restricted bands or the TV
broadcast bands. Accordingly, comments are requested on whether the
Commission should eliminate the requirement that only spurious emissions
be permitted to fall within the restricted bands and the TV broadcast
bands.

 Should the rules generally continue to prohibit operation of UWB
systems within the restricted bands and the TV broadcast bands?

 Are there certain restricted bands where operation could be permitted,
but not others? If so which bands and what is the justification?

 If certain restricted bands were retained, what impact would this have
on the viability of UWB technology?

12\. [Emission limits]{.underline}. The wide bandwidth of the emission
from a UWB system, especially when combined with a modulation technique
that pseudorandomizes the time position of the pulses, can make the
signal appear to be broadband noise.[^21] The current Part 15 rules are
based on the equivalent of a spectral power density, *i.e.*, a field
strength limit is specified along with a measurement bandwidth. In most
cases, emissions at or below 1000 MHz are based on the use of a
quasi-peak detector which employs a designated measurement
bandwidth.[^22] Above 1000 MHz, emissions are based on average field
strength limits with a minimum measurement bandwidth of one
megahertz.[^23] Where an average limit applies, there is also a limit on
peak emission levels.[^24] These emission bandwidths were chosen to
approximate the bandwidths of receivers that could receive interference.
Further, the emission limits were established based on the potential
interference from a single Part 15 device and do not take into account
cumulative effects that could occur if there is a high level of
equipment proliferation. The Commission requests comments on the
appropriateness of applying the existing general emission limits to UWB
systems.

 Are the existing general emission limits sufficient to protect other
users of the spectrum, especially radio operations in the restricted
bands, from harmful interference?

 Should different limits be applied to UWB systems?

 Should we specify a different standard for UWB devices based on
spectral power density? Should these standards be designed to ensure
that the emissions appear to be broadband noise?

 What is the potential for harmful interference due to the cumulative
impact of emissions if there is a large proliferation of UWB devices?
Could the cumulative impact result in an unacceptably high increase in
the background noise level? Should the Commission limit proliferation by
restricting the types of products or should the rules permit
manufacturers to design products for any application as long as the
equipment meets the standards?

 Should a limit on the total peak level apply to UWB devices?

 Can emissions below or above a certain frequency range be further
filtered to reduce the potential for interference to other users of the
radio spectrum without affecting the performance of the UWB systems?

 Are the existing limits on the amount of energy permitted to be
conducted back onto the AC power lines appropriate for UWB devices?

 What operational restrictions, if any, should be required to protect
existing users?

 Is the use of UWB modulation techniques necessary for certain types of
communication systems; if so, for what purposes?

13\. [Measurements]{.underline}. The testing procedures for measuring
compliance with the technical requirements applicable to Part 15
intentional radiators are specified in Sections 15.31-15.35 of the
rules. Among other things, these rules reference the specific
measurement procedure to be employed,[^25] the frequency range over
which measurements are to be made,[^26] and the measurement detector
functions and bandwidths to be employed.[^27] As indicated above, the
measurement procedures require the use of a pulse desensitization
correction factor to measure the total peak power emitted by a device.
With conventional Part 15 intentional radiators, the peak level provides
an indication of the interference potential of a device by measuring the
total amount of power that may appear in the passband of a receiver.
However, a UWB system's emission spreads the energy over a wide
bandwidth, and these transmitters typically operate with a low duty
cycle. Thus, comments are requested on whether the peak output level
continues to be indicative of the interference potential of a UWB
system. Comments are also requested on the following issues:

 Is a pulse desensitization correction factor appropriate for measuring
emissions from a UWB device? Should any modifications be made to this
measurement procedure for UWB devices?

 Would another measurement procedure that does not apply a pulse
desensitization correction factor be more appropriate for determining
the interference potential of an UWB device?

 The frequency range over which measurements are required to be made
depends on the frequency of the fundamental emission. Is the frequency
of the fundamental emission readily discernible for UWB devices? Are the
current frequency measurement ranges specified in the rules appropriate
for UWB devices or should these ranges be modified?

 Are the measurement detector functions and bandwidths appropriate for
UWB devices? Should these standards be modified and, if so, how?

 Are there any other changes to the measurement procedures that should
be applied to UWB devices?

14\. [Other matters]{.underline}. There is a prohibition in the rules
against the use of a Class B, damped wave emission.[^28] This
prohibition stems from a similar International Telecommunication Union
regulation and is a throwback to the days when spark gap transmitters
were employed.[^29] Such transmitters were noisy and generated a wide
emission bandwidth. There is no longer a clear definition of a Class B,
damped wave emission.[^30] While UWB systems produce broadband
emissions, we do not believe they should be considered as generating
Class B, damped wave emissions. The prohibition against Class B
emissions was intended to prevent the generation of wasteful radio
frequency energy and the use of inefficient transmission techniques.
This does not appear to be the case for the current UWB products.
Comments are requested on the following issues:

 Should the prohibition against Class B, damped wave emissions apply to
UWB systems or is the prohibition irrelevant, especially in light of the
relatively low power levels employed by UWB devices?

 Comments are invited on any other matters or issues that may be
pertinent to the operation of UWB systems.

### **PROCEDURAL MATTERS**

15\. This is a non-restricted notice and comment rule making proceeding.
*Ex parte* presentations are permitted, except during the Sunshine
Agenda period, provided they are disclosed as provided in the
Commission's rules. *See generally* 47 CFR §§ 1.1202, 1.1203, and
1.2306(a).

16\. Pursuant to Sections 1.415 and 1.419 of the Commission's Rules, 47
CFR §§ 1.415 and 1.419, interested parties may file comments on or
before \[**insert date 75 dates from date of publication in the Federal
Register**\] and reply comments on or before \[**insert date 105 days
from date of publication in the Federal Register**\]. Comments may be
filed using the Commission's Electronic Comment Filing System (ECFS) or
by filing paper copies. *See Electronic Filing of Documents in
Rulemaking Proceedings*, 63 Fed. Reg. 23,121 (1998).

17\. Comments filed through the ECFS can be sent as an electronic file
via the Internet to \<<http://www.fcc.gov/e-file/ecfs.html>\>.
Generally, only one copy of an electronic submission must be filed. If
multiple docket or rule making numbers appear in the cation of this
proceeding, however, commenters must transmit one electronic copy of the
comments to each docket or rule making number referenced in the caption.
In completing the transmittal screen, commenters should include their
full name, Postal Service mailing address, and the applicable docket or
rule making number. Parties may also submit an electronic comment by
Internet e-mail. To get filing instructions for e-mail comments,
commenters should send an e-mail to <ecfs@fcc.gov>, and should including
the following words in the body of the message, "get form \<your e-mail
address." A sample form and directions will be sent in reply.

18\. Parties who choose to file by paper must file an original and four
copies of each filing. If more than one docket or rule making number
appear in the caption of this proceeding, commenters must submit two
additional copies for each additional docket or rule making number. All
filings must be sent to the Commission's Secretary, Magalie Roman Salas,
Office of Secretary, Federal Communications Commission, 1919 M St.,
N.W., Room 222, Washington, D.C. 20554. Comments and reply comments will
be available for public inspection during regular business hours in the
FCC Reference Center of the Federal Communications Commission, Room 239,
1919 M Street, N.W., Washington, D.C. 20554.

19\. The proposed action is authorized under Sections 4(i), 301, 302,
303(e), 303(f), 303®, 304 and 307 of the Communications Act of 1934, as
amended, 47 USC Sections 154(i), 301, 302, 303(e), 303(f), 303®, 304,
and 307.

20\. For further information regarding this Notice of Inquiry, contact
John A. Reed, Office of Engineering and Technology, (202) 418-2455.

#### FEDERAL COMMUNICATIONS COMMISSION

Magalie Roman Salas

Secretary

[^1]: *See* 47 CFR Section 15.1 *et seq*.

[^2]: The primary operating conditions under Part 15 are that the
    operator must accept whatever interference is received and must
    correct whatever interference is caused. Should harmful interference
    occur, the operator is required to immediately correct the
    interference problem, even if correction of the problem requires
    ceasing operation of the system causing the interference. *See* 47
    CFR § 15.5.

[^3]: *See* 47 CFR § 15.209.

[^4]: *See* 47 CFR §§ 15.215-15.407. In some cases, operation at the
    higher emission levels within these designated frequency bands is
    limited to specific applications.

[^5]: The sensitive bands referenced here are bands employed by radio
    services that must function, as a nature of their operation, using
    extremely low received signal levels. These systems may be passive,
    such as radio astronomy, or active, such as satellite down links and
    wildlife tracking systems.

[^6]: *See* 47 CFR § 15.205.

[^7]: *See* 47 CFR § 15.209(a).

[^8]: *See* 47 CFR §§ 15.31-15.35.

[^9]: Typical pulse widths currently are on the order of 2-0.1
    nanoseconds, or less, in width. The emission spectrum appears as a
    fundamental lobe with adjacent side lobes that can decrease slowly
    in amplitude. Annex J of Chapter 5 of the National
    Telecommunications and Information Administration Manual calculates
    the 20 dB bandwidth of a non-FM pulsed radar as B = 1.79/√(τ~r~τ) or
    6.36/τ, whichever is less, where B is the bandwidth in megahertz, τ
    is the emitted pulse duration, in microseconds, at the 50% amplitude
    (voltage) points and τ~r~ is the emitted pulse rise time in
    microseconds from the 10% to the 90% amplitude points on the leading
    edge. As an example, for a pulse with τ = 1.0 nS, ignoring rise
    time, the 20 dB bandwidth of the emission is calculated to be 6.36
    gigahertz. The spectrum produced by a pulsed emission consists of a
    line spectrum with the spectral lines separated by 1/T where T is
    the time, in seconds, of the pulse spacing.

[^10]: Fundamental emissions consist of the carrier and modulation
    products but exclude unwanted emissions. In other words, the
    fundamental emission is equivalent to the necessary bandwidth. The
    necessary bandwidth is defined and calculated in 47 CFR § 2.202, and
    the definition of unwanted emissions, consisting of out-of-band
    emissions and spurious emissions, is contained in 47 CFR § 2.1.

[^11]: *See* the measurement procedure specified in 47 CFR §
    15.31(a)(6). This procedure references the use of HP Application
    Note 150-2 which specifies the use of a pulse desensitization
    correction factor.

[^12]: *See* 47 CFR §§ 15.35(b) and 15.209. Because ultra-wideband
    systems normally have a low duty cycle, the peak levels are quite
    high compared to the average emission levels.

[^13]: In addition, there have been several applications for grants of
    equipment authorization and an even greater number of inquiries to
    the staff to permit these systems.

[^14]: The U.S. Radar system employs different antennas, depending on
    the specific application. While the bandwidth employed by the radar
    can occupy up to several gigahertz of spectrum, the antennas are
    centered at 250 MHz, 500 MHz, 1000 MHz and 2000 MHz. U.S. Radar
    predicts that approximately 25 systems per year would be imported
    into the U.S. over a ten year period. The U.S. Radar petition was
    placed on Public Notice for comments on February 6, 1998.

[^15]: The Time Domain systems have emissions centered in the 2-4 GHz
    band and occupy several gigahertz of spectrum. Time Domains
    indicates that sales would be restricted to no more than 2500 units
    which would be marketed to fire and police departments. The Time
    Domain petition was placed on Public Notice for comments on February
    6, 1998.

[^16]: The Zircon system has its emissions centered within the 200 MHz
    to 4 GHz band and emits an average radiated power of approximately
    125 uW. Zircon states that it would limit sales to \"professional
    tradespeople for use primarily in high noise construction
    environments.\" The Zircon petition was placed on Public Notice for
    comments on May 18, 1998.

[^17]: Multipath is the propagation phenomenon that results in signals
    reaching the receiving antenna by two or more paths, usually due to
    reflections of the transmitted signal. The ability to time-gate the
    receiver would allow it to ignore signals arriving outside a
    prescribed time interval, such as signals due to multipath
    reflections.

[^18]: While Part 15 does not specifically restrict operating distance,
    the technical standards inherently limit the range for most devices
    to 100 meters or less. We recognize, however, that certain Part 15
    devices use high gain, directional antennas to achieve operating
    distances of 30 kilometers or more for point-to-point operations.

[^19]: *See* 47 CFR § 15.205.

[^20]: Spurious emissions are emissions outside of the necessary
    bandwidth, the level of which may be reduced without affecting the
    transmission of information. *See* 47 CFR § 2.1.

[^21]: The shape of the emission spectrum is dependent on the type of
    modulation employed, *e.g.*, whether the system uses pulsed
    modulation or swept frequency FM, and the method used to encode
    information on the transmission. For example, a pulse train without
    modulation or with minimal pulse position modulation will produce a
    line spectrum whereas modulation that shifts these pulses over
    larger time frames results in a spectral output that appears closer
    to noise.

[^22]: *See* 47 CFR § 15.35(a).

[^23]: *See* 47 CFR § 15.35(b). Some rule sections also specify the
    application of a total peak power limit over a wider bandwidth.
    *See*, for example, 47 CFR § 15.247(b).

[^24]: *See* 47 CFR § 15.35(b).

[^25]: *See* 47 CFR § 15.31(a)(6).

[^26]: *See* 47 CFR § 15.33.

[^27]: *See* 47 CFR § 15.35.

[^28]: *See* 47 CFR §§ 2.201(f) and 15.5(d).

[^29]: *See* Chapter II, Article 5, Section 8 of the Radio Regulations
    of the International Telecommunication Union.

[^30]: The term \"damped waves (Type B)\" was last defined in Article 5,
    Section 1 of the 1938 version of the ITU regulations as \"\[w\]aves
    composed of successive series of oscillations the amplitude of
    which, after obtaining a maximum, decreases gradually, the wave
    trains being keyed according to a telegraph code.\" A more modern
    version of the term \"damped wave\" is defined in the IEEE Standard
    Dictionary of Electrical and Electronic Terms, IEEE Std 100-1972, as
    \"\[a\] wave in which, at every point, the amplitude of each
    sinusoidal component is a decreasing function of time.\"