**APPENDIX B**

**PART 15 UNWANTED EMISSION SEPARATION**

**DISTANCE ANALYSIS**

In the Notice Proposed Rulemaking (NPRM), the Federal Communications
Commission (Commission) proposes an in-channel power level of 6 watts or
38 dBm for higher powered unlicensed devices employing cognitive radio
technologies.[^1] The NPRM also proposes to limit the unwanted emissions
for these higher powered unlicensed devices to the levels specified in
Section 15.247(c) of the Commission's Rules.[^2] Section 15.247(c)
specifies that unwanted emissions in any 100 kHz be at least 20 dB below
that in the 100 kHz bandwidth within the band that contains the highest
level of the desired power. The unwanted emission level based on the
Commission's proposal is:

38 - 20 = 18 dBm

Converting this level to a reference bandwidth of 1 MHz results in an
unwanted emission level:

18 + 10 Log (1x10^6^/100x10^3^) = 28 dBm

The receiver system noise level is computed using the following
equation:

N = -114 + 10 Log (BW) + NF (B-1)

where:

N = the receiver system noise level (dBm);

BW = the receiver intermediate frequency bandwidth (MHz);

NF = the receiver noise figure (dB).

If the licensed receiver has a bandwidth of 1 MHz and a noise figure of
3 dB, the system noise level computed using Equation B-1 is:

N = -114 + 0 + 3 = -111 dBm

Using an interference-to-noise ratio (I/N) of --6 dB as the criteria,
the allowable interference level is:

I = N + I/N = -111 + (-6) = -117 dBm

The path loss that is required to preclude interference is given by:

L~p~ = P~U~ + G~T~ + G~R~ - I (B-2)

where:

L~p~ = the path loss (dB);

P~U~ = the unwanted power level of the unlicensed device (dBm);

G~T~ = the transmit antenna gain of the unlicensed device (dBi);

G~R~ = the receive antenna gain (dBi);

I = the allowable interference level (dBm).

Using 0 dBi for the unlicensed transmit antenna gain and the receive
antenna gain, the required path loss to preclude interference computed
using Equation B-2 is:

L~p~ = 28 + 117 = 145 dB

The following equation is used to compute the distance separation that
is required to preclude potential interference:

10n Log D = L~p~ - 20 Log F + 27.55 (B-3)

where:

F = the frequency (MHz);

D = the separation distance (m);

n = the path loss exponent.

The path loss exponent indicates the rate at which the path loss
increases with distance. The value of path loss exponent depends on the
specific propagation environment. Table B-1 provides path loss exponents
for different propagation environments.[^3]

Table B-1. Path Loss Exponents for Different Environments

+-----------------------------------+-----------------------------------+
| **Propagation Environment**       | **Path Loss Exponent**            |
+-----------------------------------+-----------------------------------+
| # Free Space                      | 2                                 |
+-----------------------------------+-----------------------------------+
| **Urban Area**                    | 2.7 to 3.5                        |
+-----------------------------------+-----------------------------------+
| **Shadowed Urban Area**           | 3 to 5                            |
+-----------------------------------+-----------------------------------+
| **In-Building Line-of-Sight**     | 1.6 to 1.8                        |
+-----------------------------------+-----------------------------------+
| **Obstructed In Building**        | 4 to 6                            |
+-----------------------------------+-----------------------------------+
| **Obstructed In Factory**         | 2 to 3                            |
+-----------------------------------+-----------------------------------+

As shown in Table B-1 typical values for the path loss exponent are
between 2 to 4.

Using Equation B-3 and the path loss required to preclude interference,
the required separation distances necessary to preclude interference as
a function of frequency and path loss exponent are given in Table B-2.

Table B-2. Summary of Analysis Results

  ----------------------- -------------------- --------------------------
  **Frequency**           **Path Loss          **Required Separation
                          Exponent**           Distance**

  1000 MHz                2                    422 km

  1000 MHz                3                    5.6 km

  1000 MHz                4                    649 m

  2000 MHz                2                    211.3 km

  2000 MHz                3                    3.5 km

  2000 MHz                4                    469 m

  5000 MHz                2                    84 km

  5000 MHz                3                    1.9 km

  5000 MHz                4                    290 m
  ----------------------- -------------------- --------------------------

As shown in Table B-2, using the unwanted emission limit in Section
15.247(c), large separation distances are necessary to preclude
interference, even in environments where obstructions are present (e.g.,
n = 4).

**APPENDIX C**

**ISSUES RELATED TO GEO-LOCATION**

**COGNITIVE RADIO TECHNIQUES**

The positional accuracies available from GPS receivers range from,
centimeters for carrier-phase survey grade receivers, to about 40 meters
for users operating civilian grade coarse/acquisition (C/A) code
tracking receivers in autonomous mode. Satellite availability, which is
related to the GPS received signal level and satellite geometry, affects
positional accuracy. Satellite augmentation systems such as the Federal
Aviation Administration's Wide Area Augmentation System (WAAS)[^4] and
differential GPS (DGPS),[^5] the increased number of in orbit GPS
satellites,[^6] and the anticipated additional satellites from the
European Union's radionavigation satellite system, Galileo, will
increase the positional accuracy of GPS receivers. Additional, planned
civil-signals also can be used by ground-based GPS receivers to,
increase positional accuracy. The Commission adopted accuracy and
reliability requirements for Automatic Location Identification as part
of its rules for wireless carrier enhanced 911 (E911) service.[^7] The
accuracy and reliability requirements for E911 Phase II operations for
handset-based solutions are 50 meters for 67 percent of calls, 150
meters for 95 percent of the calls. The Commission could adopt
positional accuracy requirements for CR devices employing geo-location
capabilities that are at least as stringent as the E911 requirements.
Many manufacturers are developing GPS chipsets to meet the Commission's
December 31, 2005 Phase II deadline, so the technology should be
available at a reasonable cost. The Commission's Office of Engineering
and Technology has also developed guidelines for testing and verifying
these positional accuracy requirements.[^8]

In comments filed in response to another rulemaking proceeding, the
Institute of Electrical and Electronics Engineers (IEEE) 820.18 Radio
Regulatory Technical Advisory Group stated that embedding GPS technology
in unlicensed devices is technically feasible and could be used to limit
the device so it does not transmit when located in or near an area where
interference to a fixed receiver is likely.[^9] The IEEE also states
that unlicensed devices that employ GPS technology in conjunction with
an on-line database of the fixed site locations can be used to prohibit
that device from operating in those areas.[^10] To implement this
technique, for example, the unlicensed device could connect to the
Internet to receive updated fixed site location information. Such
updates could be accomplished over-the-air or through a computer with a
wired connection, such as by attaching to a universal serial bus port
through a cradle as currently is done for personal data assistants
(PDAs) and cell phones. Issues related to the accuracy and integrity of
the on-line databases of the fixed site locations are critical to
successfully implementing geo-location techniques. When implementing
geo-location techniques in non-government frequency bands, the
Commission's Universal Licensing Service (ULS) can be used to create and
maintain the fixed site location information. The ULS can be updated on
a daily basis to ensure that it contains the most accurate information.
The ULS is being successfully used today for non-government public
safety and non-public safety frequency bands. If geo-location techniques
are implemented in government frequency bands, NTIA can develop and
maintain a web-based capability that could be used to provide the
location information. The database of the fixed site locations would
have to be downloaded to the geo-location equipped unlicensed device on
a weekly basis in order to ensure that all fixed sites are adequately
protected.

The IEEE has stated that it is feasible to incorporate GPS chipsets
within unlicensed devices. As discussed earlier, GPS chipsets are being
incorporated in handsets to meet the Commission's E911 mandate.
Incorporating the geo-location hardware in the unlicensed device is the
only practical way to effectively, from an interference protection
standpoint, implement geo-location technology. If the Commission permits
geo-location technology to facilitate sharing with other fixed
receivers, the location positioning technology should be incorporated
within the unlicensed device.

GPS signal failures can occur in urban canyons, indoors, or in shaded
areas where there is too much noise or the received signals are too
attenuated or distorted by multipath to be received and used reliably in
ranging. Under such conditions, demodulating the navigation data
included in the satellite broadcast becomes practically impossible.[^11]
These difficulties can be somewhat compensated for by providing
additional data through a cellular network. This technique is referred
to as network or assisted GPS (AGPS).[^12] The network must be able to
supply at least the satellite orbital parameters and exact time to
enable position calculation from attenuated signals. GPS receivers in
autonomous mode are capable of providing position information during
momentary losses of the satellite signals, which occurs frequently in
urban environments. The time between when this momentary loss of
satellite signals occurs and when the receiver can no longer provide
position information depends of the GPS receiver architecture,
application, and manufacturer implementation. Since unlicensed devices
that employ geo-location techniques require a position location to
control device transmissions, it is important to determine how much time
should be permitted after the position location is lost and when the
device must cease all transmissions. For example, if a distance of 100
meters (330 feet) is assumed as the critical distance and a person is
walking at 4 miles per hour, the time required to cover this distance is
56 seconds. Therefore, using 60 seconds after position information is no
longer available as the upper limit for unlicensed devices employing
geo-location techniques to cease transmissions seems reasonable.
However, larger separation distances between unlicensed devices and the
fixed receivers could accommodate longer periods of time when the
geo-location capability is not available.

Geo-location technology used in conjunction with an on-line database of
sites that require protection holds promise for facilitating sharing
between unlicensed devices and radio services using receivers at fixed
locations. GPS-based technology incorporated within the unlicensed
device is capable of providing position locations with the necessary
accuracy. However, many issues related to the accuracy and integrity of
the on-line database as well as the integrity of the data downloaded to
the unlicensed device must be addressed. If the geo-location device is
unable to obtain a location, or the database is not successfully
downloaded, the unlicensed device should not be permitted to transmit.
In a separate rulemaking, the Commission is proposing to implement
geo-location techniques to permit sharing between unlicensed devices and
fixed-satellite earth station and radar receivers operating in the
3650-3700 MHz band. The experience gained with implementing geo-location
technology in the 3650-3700 MHz band can be used to address the issues
related to the interface with the on-line database.

**APPENDIX D**

**ISSUES RELATED TO DEVICES EMPLOYING**

**MESH NETWORKING**

Wireless networks have long embraced a centralized model that holds the
potential for bottlenecks and a single point of failure. However,
wireless mesh networks are emerging as an alternative to wireless
switching. Mesh networks distribute intelligence from switches to access
points by incorporating a grid-like topology. The development of this
topology parallels the architecture evolution in the computer industry.
First, computing environments were stand-alone mainframes; these were
followed by client/server and then peer-to-peer. Network architecture
inevitably will evolve to a distributed, dynamic wireless architecture.

Mesh networking is typically implemented in two basic modes:
infrastructure and/or client meshing. In order to gain the maximum
benefit that mesh networks have to offer, both modes need to be
supported simultaneously and seamlessly in a single network.[^13]
Infrastructure meshing creates a wireless backhaul mesh among wired
access points and wireless routers. This reduces system backhaul costs
while increasing network coverage and reliability. Client meshing
enables wireless peer-to-peer networks to form between and among client
devices (e.g., end users) and does not require any network
infrastructure to be present. In this case, clients can hop through each
other to reach other clients in the network.

In mesh networks, sophisticated digital modulation schemes, traffic
routing algorithms, and multi-hop architectures are employed that use
minimal transmission power to increase data throughput over greater
distances. With mesh networks, any node within the network can send or
receive messages and can relay messages for any one of its neighboring
nodes, thus providing a relay process where data packets travel through
intermediate nodes toward their final destination. In addition,
automatic rerouting provides redundant communication paths through the
network should any given node fail. This ability to reroute across other
links not only provides increased reliability but extends the network's
reach as well. This resilient, self healing nature stems from their mesh
networks distributed routing architecture where intelligent nodes make
their own routing decisions, avoiding a single point of failure. Because
mesh networks are self-forming, adding nodes is also relatively simple.
Because mesh networks do not rely on a single access point for data
transmissions, users of this technology can extend their communication
range beyond that of a typical wireless local area network. Achieving
the benefits of self-forming and self-healing, while using minimal power
to reduce signal interference within the mesh, involves the
implementation of sophisticated routing logic within the software and
hardware to enable maximum throughput, as well as maximum
reliability.[^14]

With low transmission power requirements and a multi-hop architecture,
mesh networks can increase the aggregate spectral capacity of existing
nodes, providing eater bandwidth across the network. Since mesh networks
transmit data over several smaller hops instead of spanning one large
distance between hops, mesh network links preserve signal-to-noise
ratios (S/N). In terms of scalability, mesh networks can accommodate
hundreds or thousands of nodes with control of the wireless system
distributed throughout the network, allowing intelligent nodes to
communicate with one another without the expense or complication of
having a central control point. Furthermore, these networks can be
installed in a matter of days or weeks without the necessity of planning
and site mapping for expensive cellular towers. As with other
peer-to-peer router-based networks, mesh networks offer multiple
redundant communication paths, allowing the network to automatically
reroute messages in the event of an unexpected node failure.[^15]

If traffic is being relayed between a large number of nodes, the latency
involved in the relaying can affect time-bounded traffic, such as voice
or video. This problem can be addressed in the routing protocols used to
implement the mesh, but it is still a potentially serious concern. In
addition, if traffic is traveling through intermediate nodes in a mesh
(as it most often will), security is an issue. Intermediate nodes might
be able to eavesdrop on data not intended for them. This problem could
be addressed by employing the end-to-end Virtual Private Network
techniques currently used on the Internet, where the same problem
exists.[^16]

The IEEE 802.15.4 standard specifies a physical layer that could be used
for mesh networking devices. The physical layer defines parameters such
as the frequency, bandwidth, transmit power, and receiver sensitivity.
The frequency bands specified in this standard are: 915 MHz, and 2.4
GHz. The standard specifies the minimum transmit power is 1 milliwatt
with a requirement to have transmitter power control (TPC) when higher
power levels (greater than 40 milliwatts) are used. The standard is
intended to provide reliable data transmission at a range of 100 meters
or more.[^17]

Given the large number of transmitters in a mesh network that can be
operating simultaneously, there is a potential risk for aggregate
interference to authorized radio services. As discussed earlier, mesh
networks by design transmit data over multiple short paths instead of a
single longer path. This means that power levels of the transmitters
used in a mesh network can be low and still achieve the necessary S/N
for a communications link.[^18] The lower power levels of the mesh
network transmitters also reduce interference to other mesh network
receivers. Currently, the IEEE 802.15.4 standard is implemented in the
902-928 MHz and 2400-2483.5 MHz ISM bands. Because these bands are used
primarily by unlicensed devices there is no impact on federal government
operations if mesh network operations are implemented in them. However
before mesh networks can be implemented in the 5725-5850 MHz ISM band,
technical analysis similar to those for the U-NII devices in the 5 GHz
band would have to be performed assessing the potential impact to
government radars that also operate in this band. The analysis should
consider the appropriate technical and operational characteristics of
the radar systems as well as those of the mesh network systems. Based on
the results of the analysis, the maximum transmit power and any
interference mitigation techniques (e.g., DFS and TPC) for the mesh
network devices that are necessary to ensure compatible operation with
the radars can be determined.

Since the length of communications paths for mesh network devices are
short by design, it may be possible to implement this technology at
higher frequency bands where propagation losses are greater. Radio
signals at higher frequencies (e.g., above 10 GHz) are increasingly
reflected and absorbed by rain and atmospheric gases. The maximum usable
range of such signals is partly dependent on the tolerable degree of
interruption by inclement weather. Further ranges are subject to greater
chances of interruption by rainstorms. Still higher in frequency, radio
signals are absorbed by gases in the atmosphere. For example, water
vapor lightly absorbs radio signals near 20 GHz, and oxygen very
strongly absorbs signals near 60 GHz.[^19] Atmospheric absorption would
be considered a disadvantage for many radio systems, however, mesh
network systems may be able to use this phenomenon to limit the range of
interfering signals within the mesh network and to substantially
increase frequency reuse.

As discussed earlier, another aspect of mesh networks is that the
capacity of the mesh increases as more nodes are added. This phenomenon
is known as Cooperation Gain.[^20] For example, rather than blast a
message at high power so that a receiver at the edge of town can hear
it, a message could be transmitted at a low power to a receiver that is
nearby, and it could then in turn transmit that low power signal to the
next receiver, and so on. Through their cooperation, these nodes
operating in a mesh could reduce the power required by any particular
transmission. If the power of any particular transmission is reduced,
then the total capacity would increase. It may also be possible to use
technologies for the mesh nodes such as ultrawideband, which has the
potential to support data rates of 100 mega bits per second or more at
short distances.

A mesh network allows nodes or access points to communicate with other
nodes without being routed through a central switch point, eliminating
centralized failure, and providing self-healing and self-organization.
NTIA believes that the short-range characteristics of mesh networks
lends itself to using higher frequencies. Higher frequencies will become
continually more attractive as: RF devices become cheaper and better;
denser device deployments such as mesh networks reduce the required path
length; and demand for wide bandwidths and frequency reuse increases.
Operating at higher frequencies will also reduce the potential for
aggregate interference to other radio services. NTIA also believes mesh
networks that have the capability to increase capacity as the number of
nodes increases can deliver broadband data rates to support high-speed
data, video and voice applications.

> **APPENDIX E**
>
> **GEO-ENCRYPTION TECHNIQUES AS A METHOD TO PROTECT OVER-THE-AIR
> SOFTWARE DOWNLOADS**
>
> A guiding principle behind the development of cryptographic systems is
> that security should not depend on keeping the algorithms secret, only
> the keys. This does not mean that the algorithms must be made public,
> but that they be designed to withstand attack under the assumption
> that the adversary knows them. Security is then achieved by encoding
> the secrets in the keys, designing the algorithms so that the best
> attack requires an exhaustive search of the key space, and using
> sufficiently long keys that the exhaustive search is infeasible.

Broadly speaking, encryption algorithms or ciphers can be divided into
two categories: symmetric algorithms and asymmetric algorithms.
Symmetric algorithms use the same key (such as a specific digital code
or bit pattern used with the algorithm) for encrypting (locking) plain
text and decrypting (unlocking) cipher text.[^21] Keeping the key
private is essential to maintaining security. Asymmetrical algorithms
have distinct keys for encryption and decryption. One major drawback to
asymmetrical algorithm is that their computational speed is typically
orders of magnitude slower than symmetrical algorithms. This has led to
hybrid algorithms, where a random key sometimes called the session key,
is generated by the originator and sent to the recipient using an
asymmetric algorithm. The session key is then used by both parties to
communicate securely using a much faster symmetric algorithm.

Location-based encryption or geo-encryption refers to any method of
encryption in which ciphertext can be decrypted only at a specified
location.[^22] If someone attempts to decrypt the data at another
location, the decryption process fails and reveals no details about the
original plaintext information. The device performing the decryption
determines its location using some sort of location sensor, such as a
GPS receiver. Location-based encryption can be used to ensure that data
cannot be decrypted outside of a particular facility (e.g., the
headquarters of a government agency or corporation). Alternatively, it
may be used to contain access to a broad geographic region. Time and
space constraints can also be placed on the decryption location.

One implementation of the geo-encryption builds on established security
algorithms and protocols, which modifies the previously discussed hybrid
algorithm to include a "Geo-lock".[^23] In this implementation, on the
originating (encrypting) side, a Geo-lock is computed on the basis of
the intended recipient's position, velocity, and time (PVT). The PVT
defines where the recipient must be in terms of position, velocity and
time for decryption to be successful. The Geo-lock is then added to the
session key to form a Geo-locked session key. The result is then
encrypted using an asymmetric algorithm and conveyed to the recipient,
much like that in the hybrid algorithm. On the recipient's (decryption)
side, Geo-locks are computed using a spoof-resistant GPS receiver for
PVT input into the PVT-to-Geo-lock mapping function.[^24] If the PVT
values are correct, then the resultant Geo-lock will be used with a
Geo-locked key to provide the correct session key. A point or a
geographic area with an arbitrary shape could be used to define the
Geo-lock. For example, the shape of the Disneyland theme park could map
into a single Geo-lock value to permit successful decryption when the
user is located in the theme park but not when outside.

Geo-encryption is an approach to location-based encryption that builds
on established cryptographic algorithms and protocols. Geo-encryption
techniques can allow information to be encrypted for a specific place or
broad geographic area, and it supports constraints in time as well as in
space. Geo-encryption can support both fixed and mobile applications and
a variety of data-sharing and distribution policies. Depending on
individual implementations, it can also provide strong protection
against location spoofing. NTIA believes that geo-encryption techniques
can be used in conjunction with existing encryption techniques to
provide protection of over-the-air software downloads.

[^1]: . *Facilitating Opportunities for Flexible, Efficient, and
    reliable Spectrum Use Employing Cognitive Radio Technologies*,
    Notice of Proposed Rulemaking, ET Docket No. 03-108, 18 F.C.C. Rcd
    26859, at ¶ 38 (2003).

[^2]: . *Id.* at ¶ 42.

[^3]: . The Institute of Electrical and Electronics Engineers Inc.
    Press, *Wireless Communications Principles and Practice*, at 104
    (1996).

[^4]: . WAAS is a system of satellites and ground stations that provide
    GPS signal corrections. A WAAS-capable GPS receiver can provide a
    positional accuracy of better than 3 meters 95 percent of the time.

[^5]: . DGPS provides corrections to the GPS signal via a datalink from
    base stations. Using DGPS the accuracy of GPS for instantaneous
    positioning is reduced from 40 meters 95% of time to typically 3
    meters 95% of the time.

[^6]: . There are currently 29 GPS satellites in orbit including spares.

[^7]: . *Revision of the Commission's Rules to Ensure Compatibility with
    Enhanced 911 Emergency Calling Systems*, Third Report and Order, CC
    Docket No. 94-102 (released October 6, 1999).

[^8]: . Federal Communications Commission, OET Bulletin No. 71*,
    Guidelines for Testing and Verifying the Accuracy of Wireless E911
    Location Systems* (April 12, 2000).

[^9]: . Institute of Electrical and Electronics Engineers Comments ET
    Docket No. 02-380, at 10 (April 17, 2003).

[^10]: . *Id.* The exclusion areas where unlicensed device operation is
    prohibited would be determined based on the characteristics and
    operational scenarios for the licensed service and the unlicensed
    devices.

[^11]: . A minimum of three to four satellites are necessary for a GPS
    receiver to determine a position location.

[^12]: . The data provided by AGPS can come in the form of sensitivity
    assistance designed to aid satellite acquisition or as assistance
    with time and timing functions.

[^13]: . Mesh Networks homepage at
    <http://www.meshnetworks.com/pages/technology/intro_technology.htm>.

[^14]: . National Telecommunications and Information Administration,
    NTIA Special Publication SP-04-409, *Proceedings of the
    International Symposium on Advanced Radio Technologies March 2-4*,
    *2004*, at 101 (March 2004).

[^15]: . *Id.* at 103.

[^16]: . Article on
    [http://wireless.itworld.com](http://wireless.itworld.com/), *The
    importance of wireless mesh networks*, at 2 (February 3, 2004).

[^17]: . The ZigBee Alliance employs the IEEE 802.15.4 standard for low
    power wireless data communications. The ZigBee Alliance is an
    association of companies working together to enable reliable, cost
    effective, low power, wirelessly networked monitoring and control
    products based on an open global standard.

[^18]: . Lower transmit power also conserves battery life, which is
    important for mesh network devices because for the network to be
    effective the individual nodes must remain on.

[^19]: . National Telecommunications and Information Administration,
    NTIA Report 98-349, *A Technological Rationale to Use Higher
    Wireless Frequencies*, at 4 (April 1998).

[^20]: . As computers get faster, this gain is referred to as processing
    gain. Radios can achieve a similar gain from cooperation.

[^21]: . Numerous very fast symmetrical algorithms are in wide spread
    use, including the Data Encryption Standard (DES) and Triple DES and
    the newly released Advanced Encryption Standard (AES).

[^22]: . Geo Intelligence, *GPS-Based Geo Encryption*, at 26 (Winter
    2003).

[^23]: . *Id.* at 28.

[^24]: . Most civil or non-military GPS receivers are easy to spoof or
    fool into determining erroneous positions. However, civil GPS
    receivers can be made to be more resistant to spoofing through a
    series of hardening measures.