Internet Engineering Task Force (IETF) A. Mancuso, Ed.
Request for Comments: 6953 Google
Category: Informational S. Probasco
ISSN: 2070-1721
B. Patil
Cisco Systems
May 2013
Protocol to Access White-Space (PAWS) Databases:
Use Cases and Requirements
Abstract
Portions of the radio spectrum that are assigned to a particular use
but are unused or unoccupied at specific locations and times are
defined as "white space". The concept of allowing additional
transmissions (which may or may not be licensed) in white space is a
technique to "unlock" existing spectrum for new use. This document
includes the problem statement for the development of a protocol to
access a database of white-space information followed by use cases
and requirements for that protocol. Finally, requirements associated
with the protocol are presented.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6953.
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Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Introduction to White Space . . . . . . . . . . . . . . . 3
1.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1. In Scope . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.2. Out of Scope . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 5
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Global Applicability . . . . . . . . . . . . . . . . . . . 6
3.2. Database Discovery . . . . . . . . . . . . . . . . . . . . 8
3.3. Device Registration . . . . . . . . . . . . . . . . . . . 8
3.4. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.5. Data Model Definition . . . . . . . . . . . . . . . . . . 9
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Master-Slave White-Space Networks . . . . . . . . . . . . 9
4.2. Offloading: Moving Traffic to a White-Space Network . . . 11
4.3. White Space Serving as Backhaul . . . . . . . . . . . . . 13
4.4. Rapid Network Deployment during Emergencies . . . . . . . 14
4.5. White Space Used for Local TV Broadcaster . . . . . . . . 15
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1. Data Model Requirements . . . . . . . . . . . . . . . . . 16
5.2. Protocol Requirements . . . . . . . . . . . . . . . . . . 17
5.3. Operational Requirements . . . . . . . . . . . . . . . . . 19
5.4. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Security Considerations . . . . . . . . . . . . . . . . . . . 20
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1. Normative References . . . . . . . . . . . . . . . . . . . 22
8.2. Informative References . . . . . . . . . . . . . . . . . . 22
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1. Introduction
1.1. Introduction to White Space
Wireless spectrum is a commodity that is regulated by governments.
The spectrum is used for various purposes, which include, but are not
limited to, entertainment (e.g., radio and television), communication
(e.g., telephony and Internet access), military (e.g., radars, etc.),
and navigation (e.g., satellite communication, GPS). Portions of the
radio spectrum that are assigned to a licensed (primary) user but are
unused or unoccupied at specific locations and times are defined as
"white space". The concept of allowing additional (secondary)
transmissions (which may or may not be licensed) in white space is a
technique to "unlock" existing spectrum for new use.
An obvious requirement is that these secondary transmissions do not
interfere with the assigned use of the spectrum. One interesting
observation is that often, in a given physical location, the primary
user(s) may not be using the entire band assigned to them. The
available spectrum for secondary transmissions would then depend on
the location of the secondary user. The fundamental issue is how to
determine, for a specific location and specific time, if any of the
assigned spectrum is available for secondary use.
Academia and industry have studied multiple cognitive radio [CRADIO]
mechanisms for use in such a scenario. One simple mechanism is to
use a geospatial database that contains the spatial and temporal
profile of all primary licensees' spectrum usage, and require
secondary users to query the database for available spectrum that
they can use at their location. Such databases can be accessible and
queryable by secondary users on the Internet.
Any entity that is assigned spectrum that is not densely used may be
asked by a governmental regulatory agency to share it to allow for
more intensive use of the spectrum. Providing a mechanism by which
secondary users share the spectrum with the primary user is
attractive in many bands, in many countries.
This document includes the problem statement followed by use cases
and requirements associated with the use of white-space spectrum by
secondary users via a database query protocol. The final sections
include the requirements associated with such a protocol. Note that
the IETF has undertaken to develop a database query protocol (see
[PAWS]).
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1.2. Scope
1.2.1. In Scope
This document covers the requirements for a protocol to allow a
device to access a database to obtain spectrum availability
information. Such a protocol should allow a device to perform the
following actions:
1. Determine the relevant database to query.
2. Connect to and optionally register with the database using a
well-defined protocol.
3. Provide geolocation and perhaps other data to the database using
a well-defined format for querying the database.
4. Receive in response to the query a list of available white-space
frequencies at the specified geolocation using a well-defined
format for the information.
5. Send an acknowledgment to the database with information
containing channels selected for use by the device and other
device operation parameters.
Note: The above protocol actions should explicitly or implicitly
support the ability of devices to re-register and/or re-query the
database when they change their locations or operating parameters.
This will allow them to receive permission to operate in their new
locations and/or with their new operating parameters, and to send
acknowledgments to the database that include information on their new
operating parameters.
1.2.2. Out of Scope
The following topics are out of scope for this specification:
1. It is the device's responsibility to query the database for new
spectrum when the device moves, changes operating parameters,
loses connectivity, etc. Other synchronization mechanisms are
out of scope.
2. A rogue device may operate without contacting the database to
obtain available spectrum. Hence, enforcement of spectrum usage
by devices is out of scope.
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3. The protocol defines communications between the database and
devices. The protocol for communications between devices is out
of scope.
4. Coexistence and interference avoidance of white-space devices
within the same spectrum are out of scope.
5. Provisioning (releasing new spectrum for white-space use) is out
of scope.
2. Conventions Used in This Document
2.1. Terminology
Database: A database is an entity that contains current information
about available spectrum at a given location and time, as well as
other types of information related to spectrum availability and
usage.
Device Class: Identifies classes of devices including fixed, mobile,
portable, etc. May also indicate if the device is indoor or
outdoor.
Device ID: An identifier for a device.
Master Device: A device that queries the database, on its own behalf
and/or on behalf of a slave device, to obtain available spectrum
information.
Slave Device: A device that queries the database through a master
device.
Trusted Database: A database that is trusted by a device or provides
data objects that are trusted by a device.
White Space (WS): Radio spectrum that is available for secondary use
at a specific location and time.
White-Space Device (WSD): A device that uses white-space spectrum as
a secondary user. A white-space device can be a fixed or portable
device such as an access point, base station, or cell phone.
2.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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3. Problem Statement
The use of white-space spectrum is enabled via the capability of a
device to query a database and obtain information about the
availability of spectrum for use at a given location. The databases
are reachable via the Internet, and the devices querying these
databases are expected to have some form of Internet connectivity,
directly or indirectly. While databases are expected to support the
rule set(s) of one or more regulatory domains, and the regulations
and available spectrum associated with each rule set may vary, the
fundamental operation of the protocol must be independent of any
particular regulatory environment.
An example of the high-level architecture of the devices and
databases is shown in Figure 1.
-----------
| Master |
|WS Device| ------------
|Lat: X |\ .---. /--------|Database A|
|Long: Y | \ ( ) / ------------
----------- \-------/ \/ o
( Internet) o
----------- /------( )\ o
| Master | / ( ) \ o
|WS Device|/ (_____) \ ------------
|Lat: X | \------|Database B|
|Long: Y | ------------
-----------
Figure 1: High-Level View of White-Space Database Architecture
Note that there could be multiple databases serving white-space
devices. In some countries, such as the U.S., the regulator has
determined that multiple databases may provide service to white-space
devices.
A messaging interface between the white-space devices and the
database is required for operating a network using the white-space
spectrum. The following sections discuss various aspects of such an
interface and the need for a standard.
3.1. Global Applicability
The use of white-space spectrum is currently approved or being
considered in multiple regulatory domains, whose rules may differ.
However, the need for devices that intend to use the spectrum to
communicate with a database remains a common feature. The database
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implements rules that protect all primary users, independent of the
characteristics of the white-space devices. It also provides a way
to specify a schedule of use, since some primary users (for example,
wireless microphones) only operate in limited time slots.
Devices need to be able to query a database, directly or indirectly,
over the public Internet and/or private IP networks prior to
operating in available spectrum. Information about available
spectrum, schedule, power, etc., are provided by the database as a
response to the query from a device. The messaging interface needs
to be:
1. Interface agnostic - An interface between a master white-space
device and database can be wired or unwired (e.g., a radio/air
interface technology such as IEEE 802.11af, IEEE 802.15.4m, IEEE
802.16, IEEE 802.22, LTE, etc.) However, the messaging interface
between a master white-space device and the database should be
agnostic to the interface used for such messaging while being
cognizant of the characteristics of the interface technology and
the need to include any relevant attributes in the query to the
database.
2. Spectrum agnostic - The spectrum used by primary and secondary
users varies by country. Some spectrum bands have an explicit
notion of a "channel": a defined swath of spectrum within a band
that has some assigned identifier. Other spectrum bands may be
subject to white-space sharing, but only have actual frequency
low/high parameters to define primary and secondary use. The
protocol should be able to be used in any spectrum band where
white-space sharing is permitted.
3. Globally applicable - A common messaging interface between white-
space devices and databases will enable the use of such spectrum
for various purposes on a global basis. Devices can operate in
any location where such spectrum is available and a common
interface ensures uniformity in implementations and deployment.
To allow the global use of white-space devices in different
countries (whatever the regulatory domain), the protocol should
support the database that communicates the applicable regulatory
rule-set information to the white-space device.
4. Built on flexible and extensible data structures - Different
databases are likely to have different requirements for the kinds
of data required for registration (different regulatory rule sets
that apply to the registration of devices) and other messages
sent by the device to the database. For instance, different
regulators might require different device-characteristic
information to be passed to the database.
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3.2. Database Discovery
The master device must obtain the address of a trusted database,
which it will query for available white-space spectrum. If the
master device uses a discovery service to locate a trusted database,
it may perform the following steps (this description is intended as
descriptive, not prescriptive):
1. The master device constructs and sends a request (e.g., over the
Internet) to a trusted discovery service.
2. If no acceptable response is received within a pre-configured
time limit, the master device concludes that no trusted database
is available. If at least one response is received, the master
device evaluates the response(s) to determine if a trusted
database can be identified where the master device is able to
receive service from the database. If so, it establishes contact
with the trusted database.
3. The master device establishes a white-space network as described
in Section 4.
Optionally, and in place of steps 1-2 above, the master device can be
pre-configured with the address (e.g., URI) of one or more trusted
databases. The master device can establish contact with one of these
trusted databases.
3.3. Device Registration
The master device may register with the database before it queries
the database for available spectrum. A registration process may
consist of the following steps:
1. The master device sends registration information to the database.
This information may include the device ID; serial number
assigned by the manufacturer; device location; device antenna
height above ground; name of the individual or business that owns
the device; and the name, postal address, email address, and
phone number of a contact person responsible for the device's
operation.
2. The database responds to the registration request with an
acknowledgment to indicate the success of the registration
request or with an error if the registration was unsuccessful.
Additional information may be provided by the database in its
response to the master device.
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3.4. Protocol
A protocol that enables a white-space device to query a database to
obtain information about available spectrum is needed. A device may
be required to register with the database with some credentials prior
to being allowed to query. The requirements for such a protocol are
specified in this document.
3.5. Data Model Definition
The contents of the queries and response need to be specified. A
data model is required; it must enable the white-space device to
query the database while including all the relevant information, such
as geolocation, radio technology, power characteristics, etc., which
may be country, spectrum, and regulatory dependent. All databases
are able to interpret the data model and respond to the queries using
the same data model that is understood by all devices.
4. Use Cases
There are many potential use cases for white-space spectrum -- for
example, providing broadband Internet access in urban and densely
populated hotspots, as well as rural and remote, underserved areas.
Available white-space spectrum may also be used to provide Internet
'backhaul' for traditional Wi-Fi hotspots or for use by towns and
cities to monitor/control traffic lights, read utility meters, and
the like. Still other use cases include the ability to offload data
traffic from another Internet access network (e.g., 3G cellular
network) or to deliver data, information, or a service to a user
based on the user's location. Some of these use cases are described
in the following sections.
4.1. Master-Slave White-Space Networks
There are a number of common scenarios in which a master white-space
device will act as proxy or mediator for one or more slave devices
using its connection to the Internet to query the database for
available spectrum for itself and for one or more slave devices.
These slave devices may be fixed or mobile, in close proximity with
each other (indoor network or urban hotspot), or at a distance (rural
or remote WAN). Once slave devices switch to white-space spectrum
for their communications, they may connect through the master to the
Internet or use white-space spectrum for intra-network communications
only. The master device can continue to arbitrate and control white-
space communications by slave devices, and it may notify them when
they are required to change white-space frequencies or cease white-
space communications.
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Figure 2 depicts the general architecture of such a simple master-
slave network in which the master device communicates with a database
on its own behalf and on behalf of slave devices.
--------
|Slave |
|Device| \ \|/ ----------
| 1 | (Air) | |Database|
-------- \ | (----) /|--------|
| \ ------|------ ( ) /
| \| Master | / \
-------- /| |======= ( Internet )
|Slave | / | Device | \ /
|Device| (Air) | | ( )
| 2 | / |-----------| (----)
-------- /
o | /
o | (Air)
o | /
-------- /
|Slave | /
|Device| /
| n |
--------
Figure 2: Master-Slave White-Space Network
The protocol requirements for these master-slave devices and other
similar scenarios is essentially the same: the protocol must support
the ability of a master device to make available-spectrum query
requests on behalf of slave devices, passing device identification,
geolocation, and other slave device parameters to the database as
required to obtain a list of white-space spectrum available for use
by one or more slave devices. Of course, different use cases will
use this spectrum information in different ways, and the details of
master/slave communications may be different for different use cases.
Common steps that may occur in master-slave networks include the
following:
1. The master device powers up.
2. Slave devices may power up and associate with the master device
via Wi-Fi or some other over-the-air, non-white-space spectrum.
Until the slave device is allocated white-space spectrum, any
master-slave or slave-slave communications occurs over such non-
white-space spectrum.
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3. The master has Internet connectivity, determines (or knows) its
location, and establishes a connection to a trusted database (see
Section 3.2).
4. The master may register with the trusted database (see
Section 3.3).
5. The master sends a query to the trusted database requesting a
list of available white-space spectrum based upon its
geolocation. Query parameters may include the master's location,
device identifier, and antenna height. The master may send
available-spectrum requests to the database on behalf of slave
devices.
6. The database responds to the master's query with a list of
available white-space spectrum, associated maximum power levels,
and durations of time for spectrum use. If the master made
requests on behalf of slave devices, the master may transmit the
obtained available-spectrum lists to the slaves (or the master
may allocate spectrum to slaves from the obtained spectrum
lists).
7. The master may inform the database of the spectrum and power
level it selects from the available spectrum list. If a slave
device has been allocated available white-space spectrum, the
slave may inform the master of the spectrum and power level it
has chosen, and the master may, in turn, relay such slave device
usage to the database.
8. Further communication among masters and slaves over the white-
space network may occur via the selected/allocated white-space
spectrum frequencies.
Note: Steps 5 through 7 may be repeated by the master device when it
(or a slave device that uses the master as a proxy to communicate
with the database) changes its location or operating parameters --
for example, after a master changes location, it may query the
database for available spectrum at its new location, then acknowledge
the subsequent response received from the database with information
on the spectrum and power levels it is using at the new location.
4.2. Offloading: Moving Traffic to a White-Space Network
This scenario is a variant of the master-slave network described in
the previous use case. In this scenario, an access point (AP) offers
a white-space service that offloads Internet traffic as an
alternative data path to a more congested or costly Internet wire,
wireless, or satellite service.
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Figure 3 shows an example of deployment of this scenario.
\|/
|
|--|----------|
\|/ /|Access Point |\
| (Air)--/ |-------------| \
--|------ / \ -----------
|Portable|/ \ (----) | Database|
| Device | \ ( ) /----------
|--------|\ \ / \
\ X( Internet )
\ / \ /
(Air) / ( )
\ / (----)
\ /
\|---------------|/
| Metered |
| Service |
|---------------|
Figure 3: Offloading Traffic to a White-Space Network
A simplified operation scenario of offloading content, such as video
stream, from a congested or costly Internet connection to a white-
space service provided by an AP consists of the following steps:
1. The AP contacts the database to determine channels it can use.
2. The portable device connects to a paid Internet service and
selects a video for streaming.
3. The portable device determines if it can offload to a white-space
AP:
A. If the portable device knows its location, it
1. asks the database (using the paid service) for available
white-space spectrum;
2. listens for and connects to the AP over the permitted
white-space spectrum.
B. If the portable device does not have GPS or other means to
determine its position, it
1. uses non-white-space spectrum to listen for and connect
to the AP;
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2. asks the AP to query the database for permitted white-
space spectrum on its behalf;
3. uses the permitted white-space spectrum to connect to the
AP.
4. The portable device accesses the Internet through the AP to
stream the selected video.
4.3. White Space Serving as Backhaul
In this use case, an Internet connectivity service is provided to
users over a common wireless standard, such as Wi-Fi, with a white-
space master/slave network providing backhaul connectivity to the
Internet. Note that Wi-Fi is referenced in Figure 4 and the
following discussion, but any other technology can be substituted in
its place.
Figure 4 shows an example of deployment of this scenario.
\|/ White \|/ \|/ Wi-Fi \|/
| Space | | |
| | | |-|----|
(----) |-|----| |-|------|-| | Wi-Fi|
( ) |Master| | Slave |--(Air)--| Dev |
/ \ | |--(Air)--| Bridge | |------|
( Internet )---| | | to Wi-Fi |
\ / |------| |----------| \|/
( ) \ |
(----) \(Air) |-|----|
\--| Wi-Fi|
| Dev |
|------|
Figure 4: White-Space Network Used for Backhaul
Once the bridged device (Slave Bridge + Wi-Fi) is connected to a
master and WS network, a simplified operation scenario of backhaul
for Wi-Fi consists of the following steps:
1. A bridged slave device (Slave Bridge + Wi-Fi) is connected to a
master device operating in the WS spectrum (the master obtains
available white-space spectrum as described in Section 4.1).
2. Once the slave device is connected to the master, the Wi-Fi
access point has Internet connectivity as well.
3. End users attach to the Wi-Fi network via their Wi-Fi-enabled
devices and receive Internet connectivity.
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4.4. Rapid Network Deployment during Emergencies
Organizations involved in handling emergency operations maintain an
infrastructure that relies on dedicated spectrum for their
operations. However, such infrastructures are often affected by the
disasters they handle. To set up a replacement network, spectrum
needs to be quickly cleared and reallocated to the crisis response
organization. Automation of this allocation and assignment is often
the best solution. A preferred option is to make use of a robust
protocol that has been adopted and implemented by radio
manufacturers. A typical network topology solution might include
wireless access links to the public Internet or private network,
wireless ad hoc network radios working independently of a fixed
infrastructure, and satellite links for backup where lack of
coverage, overload, or outage of wireless access links can occur.
Figure 5 shows an example of deployment of this scenario.
\|/
| ad hoc
|
|-|-------------|
| Master node | |-------------|
\|/ | with | | White-Space |
| ad hoc /| backhaul link | | Database |
| /---/ |---------------| |-------------|
---|------------/ | \ /
| Master node | | | (--/--)
| without | | -----( )
| backhaul link | | Wireless / Private \
----------------\ | Access ( net or )
\ | \ Internet )
\ \|/ | ------( /
\ | ad hoc | | (------)
\ | | / \
\--|------------- /Satellite ----------
| Master node | / Link | Other |
| with |/ | nodes |
| backhaul link | ----------
-----------------
Figure 5: Rapidly Deployed Network with Partly Connected Nodes
In the ad hoc network, all nodes are master nodes that allocate radio
frequency (RF) channels from the database (as described in
Section 4.1). However, the backhaul link may not be available to all
nodes, such as depicted for the left node in the above figure. To
handle RF channel allocation for such nodes, a master node with a
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backhaul link relays or proxies the database query for them. So
master nodes without a backhaul link follow the procedure as defined
for clients. The ad hoc network radios utilize the provided RF
channels. Details on forming and maintenance of the ad hoc network,
including repair of segmented networks caused by segments operating
on different RF channels, is out of scope of spectrum allocation.
4.5. White Space Used for Local TV Broadcaster
Available white-space spectrum can be deployed in novel ways to
leverage the public use of hand-held and portable devices. One such
use is white-space spectrum used for local TV transmission of audio-
video content to portable devices used by individuals in attendance
at an event. In this use case, audience members at a seminar,
entertainment event, or other venue plug a miniature TV receiver fob
into their laptop, computer tablet, cell phone, or other portable
device. A master device obtains a list of available white-space
spectrum (as described in Section 4.1), then broadcasts audio-video
content locally to the audience over one of the available
frequencies. Audience members receive the content through their
miniature TV receivers tuned to the appropriate white-space band for
display on the monitors of their portable devices.
Figure 6 shows an example of deployment of this scenario.
|------------|
|White-Space |
| Database |
.---. / |------------|
|-----------| ( ) /
| Master | / \
| |========( Internet)
|-----------| \ /
| ( )
/|\ (---)
(White-Space
Broadcast)
\|/ \|/ \|/ \|/ \|/ \|/ \|/
| | | | | | | .................
----- ----- ----- ----- ----- ----- -----
| | | | | | | | | | | | | |
| | | | | | | | | | | | | |
----- ----- ----- ----- ----- ----- -----
USB TV receivers connected to laptops, cell phones, tablets ...
Figure 6: White Space Used for Local TV Broadcast
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5. Requirements
5.1. Data Model Requirements
D.1 The data model MUST support specifying the geolocation of the
white-space device, the uncertainty in meters, the height and
its uncertainty, and the percentage of confidence in the
location determination. The data model MUST support [WGS84].
D.2 The data model MUST support specifying the data and other
applicable requirements of the rule set that applies to the
white-space device at a specified location.
D.3 The data model MUST support device description data that
identifies a white-space device (serial number, certification
IDs, etc.) and describes device characteristics, such as device
class (fixed, mobile, portable, indoor, outdoor, etc.), Radio
Access Technology (RAT), etc.
D.4 The data model MUST support specifying a manufacturer's serial
number for a white-space device.
D.5 The data model MUST support specifying the antenna- and
radiation-related parameters of the white-space device, such as:
antenna height
antenna gain
maximum output power, Equivalent Isotropic Radiated Power
(EIRP) in dBm (decibels referenced to 1 milliwatt)
antenna radiation pattern (directional dependence of the
strength of the radio signal from the antenna)
spectrum mask with lowest and highest possible frequency
spectrum mask in dBr (decibels referenced to an arbitrary
reference level) from peak transmit power in EIRP, with
specific power limit at any frequency linearly interpolated
between adjacent points of the spectrum mask
measurement resolution bandwidth for EIRP measurements
D.6 The data model MUST support specifying owner and operator
contact information for a transmitter. This includes the name
of the transmitter owner and the name, postal address, email
address, and phone number of the transmitter operator.
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D.7 The data model MUST support specifying spectrum availability.
Spectrum units are specified by low and high frequencies and may
have an optional channel identifier. The data model MUST
support a schedule including start time and stop time for
spectrum unit availability. The data model MUST support maximum
power level for each spectrum unit.
D.8 The data model MUST support specifying spectrum availability
information for a single location and an area (e.g., a polygon
defined by multiple location points or a geometric shape such as
a circle).
D.9 The data model MUST support specifying the frequencies and power
levels selected for use by a white-space device in the
acknowledgment message.
5.2. Protocol Requirements
P.1 The master device identifies a database to which it can
register, make spectrum availability requests, etc. The
protocol MUST support the discovery of an appropriate database
given a location provided by the master device. The master
device MAY select a database by discovery at run time or by
means of a pre-programmed URI. The master device MAY validate
discovered or configured database addresses against a list of
known databases (e.g., a list of databases approved by a
regulatory body).
P.2 The protocol MUST support the database informing the master of
the regulatory rules (rule set) that applies to the master
device (or any slave devices on whose behalf the master is
contacting the database) at a specified location.
P.3 The protocol MUST provide the ability for the database to
authenticate the master device.
P.4 The protocol MUST provide the ability for the master device to
verify the authenticity of the database with which it is
interacting.
P.5 The messages sent by the master device to the database and the
messages sent by the database to the master device MUST support
integrity protection.
P.6 The protocol MUST provide the capability for messages sent by
the master device and database to be encrypted.
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P.7 Tracking of master or slave device uses of white-space spectrum
by database administrators, regulatory agencies, and others who
have access to a white-space database could be considered
invasive of privacy, including privacy regulations in specific
environments. The PAWS protocol SHOULD support privacy-
sensitive handling of device-provided data where such
protection is feasible, allowed, and desired.
P.8 The protocol MUST support the master device registering with
the database; see Device Registration (Section 3.3).
P.9 The protocol MUST support a registration acknowledgment
indicating the success or failure of the master device
registration.
P.10 The protocol MUST support an available spectrum request from
the master device to the database, which may include one or
more of the data items listed in Data Model Requirements
(Section 5.1). The request may include data that the master
device sends on its own behalf and/or on behalf of one or more
slave devices.
P.11 The protocol MUST support an available spectrum response from
the database to the master device, which may include one or
more of the data items listed in Data Model Requirements
(Section 5.1). The response may include data related to master
and/or slave device operation.
P.12 The protocol MUST support a spectrum usage message from the
master device to the database, which may include one or more of
the data items listed in Data Model Requirements (Section 5.1).
The message may include data that the master device sends on
its own behalf and/or on behalf of one or more slave devices.
P.13 The protocol MUST support a spectrum usage message
acknowledgment.
P.14 The protocol MUST support a validation request from the master
device to the database to validate a slave device, which should
include information necessary to identify the slave device to
the database.
P.15 The protocol MUST support a validation response from the
database to the master to indicate if the slave device is
validated by the database. The validation response MUST
indicate the success or failure of the validation request.
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P.16 The protocol MUST support the capability for the database to
inform master devices of changes to spectrum availability
information.
5.3. Operational Requirements
This section contains operational requirements of a database-device
system, independent of the requirements of the protocol for
communication between the database and devices.
O.1 The master device must be able to connect to the database to
send requests to the database and receive responses to, and
acknowledgments of, its requests from the database.
O.2 A master device MUST be able to determine its location including
uncertainty and confidence level. A fixed master device may use
a location programmed at installation.
O.3 The master device MUST be configured to understand and comply
with the requirements of the rule set of the regulatory body
that apply to its operation at its location.
O.4 A master device MUST query the database for the available
spectrum at a specified location before starting radio
transmission in white space at that location.
O.5 A master device MUST be able to query the database for the
available spectrum on behalf of a slave device at a specified
location before the slave device starts radio transmission in
white space at that location.
O.6 The database MUST respond to an available spectrum request.
5.4. Guidelines
White-space technology itself is expected to evolve and include
attributes such as coexistence and interference avoidance, spectrum
brokering, alternative spectrum bands, etc. The design of the data
model and protocol should be cognizant of the evolving nature of
white-space technology and consider the following set of guidelines
in the development of the data model and protocol:
1. The data model SHOULD provide a modular design separating
messaging-specific, administrative-specific, and spectrum-
specific parts into distinct modules.
2. The protocol SHOULD support determination of which
administrative-specific and spectrum-specific modules are used.
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6. Security Considerations
PAWS is a protocol whereby a master device requests a schedule of
available spectrum at its location (or the location of its slave
devices) before it (or they) can operate using those frequencies.
Whereas the information provided by the database must be accurate and
conform to applicable regulatory rules, the database cannot enforce,
through the protocol, that a client device uses only the spectrum it
provided. In other words, devices can put energy in the air and
cause interference without asking the database. Hence, PAWS security
considerations do not include protection against malicious use of the
white-space spectrum.
Threat model for the PAWS protocol:
Assumptions:
The link between the master device and the database can be
wired or wireless and provides IP connectivity. It is assumed
that an attacker has full access to the network medium between
the master device and the database. The attacker may be able
to eavesdrop on any communications between these entities.
Threat 1: User modifies a device to masquerade as another valid
certified device
A master device identifies itself to the database in order to
obtain information about available spectrum. Without suitable
protection mechanisms, devices can listen to registration
exchanges and later register with the database by claiming the
identity of another device.
Threat 2: Spoofed database
A master device attempts to discover a database (or databases)
that it can query for available spectrum information. An
attacker may attempt to spoof a database and provide responses
to a master device that are malicious and result in the master
device causing interference to the primary user of the
spectrum.
Threat 3: Modifying or jamming a query request
An attacker may modify or jam the query request sent by a
master device to a database. The attacker may change the
location of the device or its capabilities (transmit power,
antenna height, etc.), and, as a result, the database responds
with incorrect information about available spectrum or maximum
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transmit power allowed. The result of such an attack is that
the master device can cause interference to the primary user of
the spectrum. It may also result in a denial of service to the
master device if the modified database response indicates that
no channels are available to the master device or when a jammed
query prevents the request from reaching the database.
Threat 4: Modifying or jamming a query response
An attacker may modify or jam the query response sent by the
database to a master device. For example, an attacker may
modify the available spectrum or power-level information
carried in the database response. As a result, a master device
may use spectrum that is not available at a location or may
transmit at a greater power level than allowed. Such
unauthorized use can result in interference to the primary user
of that spectrum. Alternatively, an attacker may modify a
database response to indicate that no spectrum is available at
a location (or jam the response), resulting in a denial of
service to the master device.
Threat 5: Third-party tracking of white-space device location and
identity
A master device may provide its identity in addition to its
location in the query request. Such location/identity
information can be gleaned by an eavesdropper and used for
unauthorized tracking purposes.
Threat 6: Malicious individual acts as a database to terminate or
unfairly limit spectrum access of devices
A database may include a mechanism by which service and
spectrum allocated to a master device can be revoked by sending
a revoke message to a master device. A malicious user can
pretend to be a database and send a revoke message to that
device. This results in denial of service to the master
device.
The security requirements arising from the above threats are captured
in the requirements of Section 5.2.
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7. Acknowledgments
The authors acknowledge Gabor Bajko, Teco Boot, Nancy Bravin, Rex
Buddenberg, Vincent Chen, Gerald Chouinard, Stephen Farrell, Michael
Fitch, Joel M. Halpern, Jussi Kahtava, Paul Lambert, Barry Leiba,
Subramanian Moonesamy, Pete Resnick, Brian Rosen, Andy Sago, Peter
Stanforth, John Stine, and Juan Carlos Zuniga for their contributions
to this document.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[WGS84] National Imagery and Mapping Agency, "Department of
Defense World Geodetic System 1984, Its Definition and
Relationships with Local Geodetic Systems", NIMA
TR8350.2 Third Edition Amendment 1, January 2000,
<
http://earth-info.nga.mil/GandG/publications/tr8350.2/
wgs84fin.pdf>.
8.2. Informative References
[CRADIO] Cognitive Radio Technologies Proceeding (CRTP), "Federal
Communications Commission", ET Docket No. 03-108,
August 2010, <
http://fcc.gov/oet/cognitiveradio>.
[PAWS] Chen, V., Ed., Das, S., Zhu, L., Malyar, J., and P.
McCann, "Protocol to Access Spectrum Database", Work
in Progress, May 2013.
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Authors' Addresses
Anthony Mancuso (editor)
Google
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
EMail:
[email protected]
Scott Probasco
EMail:
[email protected]
Basavaraj Patil
Cisco Systems
2250 East President George Bush Highway
Richardson, TX 75082
US
EMail:
[email protected]
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