PAWS Mancuso, Ed.
Internet-Draft Probasco
Intended status: Informational Patil
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Protocol to Access White Space (PAWS) Database: Use Cases and
Requirements
draft-ietf-paws-problem-stmt-usecases-rqmts-11
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. An obvious
requirement is that these additional transmissions do not interfere
with the assigned use of the spectrum. One approach to using white
space spectrum at a given time and location is to verify spectrum
availability with a database that manages spectrum sharing and
provides spectrum-availability information. The IETF has undertaken
to develop a Protocol to Access Spectrum Database [1] for such a
management database.
This document describes a number of possible use cases of white space
spectrum and technology as well as a set of requirements for the
database query protocol. The concept of white spaces is described
along with the problems that need to be addressed to enable white
space spectrum for additional uses without causing interference to
currently assigned use. Use of white space is enabled by querying a
database that stores information about spectrum availability at any
given location and time.
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].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on July 29, 2013.
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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Introduction to white space . . . . . . . . . . . . . . . 4
1.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1. In Scope . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.2. Out of Scope . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 5
2.1. Conventions Used in This Document . . . . . . . . . . . . 5
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
3. Protocol Services . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Protocol services . . . . . . . . . . . . . . . . . . . . 6
3.1.1. White space database discovery . . . . . . . . . . . . 6
3.1.2. Device registration with trusted database . . . . . . 7
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Use cases . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. Master-slave white space networks . . . . . . . . . . 8
4.1.2. Offloading: moving traffic to a white space network . 10
4.1.3. White space serving as backhaul . . . . . . . . . . . 11
4.1.4. Rapid network deployment during emergency scenario . . 12
4.1.5. White space used for local TV broadcaster . . . . . . 13
5. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 14
5.1. Global applicability . . . . . . . . . . . . . . . . . . . 15
5.2. Database discovery . . . . . . . . . . . . . . . . . . . . 17
5.3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.4. Data model definition . . . . . . . . . . . . . . . . . . 17
6. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.1. Data Model Requirements . . . . . . . . . . . . . . . . . 17
6.2. Protocol Requirements . . . . . . . . . . . . . . . . . . 19
6.3. Operational Requirements . . . . . . . . . . . . . . . . . 20
6.4. Guidelines . . . . . . . . . . . . . . . . . . . . . . . . 22
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
9. Summary and Conclusion . . . . . . . . . . . . . . . . . . . . 25
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
11.1. Normative References . . . . . . . . . . . . . . . . . . . 26
11.2. Informational References . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
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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 [2] 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.
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:
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1. Determine the relevant white space database to query.
2. Connect to and optionally register with the database using a
well-defined protocol.
3. Provide its 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 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.
1.2.2. Out of Scope
The following topics are out of scope for this specification:
1. Co-existence and interference avoidance of white space devices
within the same spectrum.
2. Provisioning (releasing new spectrum for white space use).
2. Conventions and Terminology
2.1. Conventions Used in This Document
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].
2.2. 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 A unique number for each master device.
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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.
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.
3. Protocol Services
3.1. Protocol services
A complete protocol solution must enable many different potential
white space services. This section describes the features required
of the protocol.
3.1.1. White space database discovery
White space database discovery is preliminary to creating a radio
network using white space; it is a prerequisite to the use cases
below. The radio network is created by a master device. Before the
master device can transmit in white space spectrum, it must contact a
trusted database where the device can learn if any spectrum is
available for its use. The master device will need to discover a
trusted database, using the following steps:
1. The master device is connected to the Internet.
2. The master device constructs and sends a service request over the
Internet.
3. 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.
Optionally the radio device is pre-programmed with the Internet
address of at least one trusted database. The device can establish
contact with a trusted database using one of the pre-programmed
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Internet addresses and establish a white space network (as described
in one of the following use cases).
3.1.2. Device registration with trusted database
In some regulatory domains, the master device must register with the
trusted database before it queries the database for available
spectrum. Different regulatory domains may have different device
registration requirements.
Figure 1 (Figure 1) shows an example deployment of this scenario.
----------
\|/ |Database|
| .---. / ---------
|--|--------| ( ) /
| Master | / \
| |========( Internet)
|-----------| \ /
( )
(---)
Figure 1: Example illustration of registration requirement in white
space use-case
A simplified operational scenario showing registration consists of
the following steps:
1. If required by the regulatory domain, the master device registers
with its most current and up-to-date information. If subject to
registration, typically the master device will register after
power up, after changing location by a predetermined distance,
and after prescribed time intervals.
2. To register with the database, 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, street and email address, and telephone number of a
contact person responsible for the device's operation.
3. The database responds to the registration request with an
acknowledgement 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 according to regulatory requirements.
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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. Use cases
4.1.1. 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 may notify them when they
are required to change white space frequencies or cease white space
communications.
Figure 2 (Figure 2) depicts the general architecture such a simple
master-slave network, in which the master device communicates on its
own behalf and on behalf of slave devices with a white space
database.
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--------
|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 device 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 may occur in master-slave networks include the
following:
1. The master device powers up.
2. Slave devices 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.
3. The master has Internet connectivity, determines (or knows) its
location, and establishes a connection to a trusted white space
database (see Section 4.1.1).
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4. The master optionally registers with the trusted database (see
Section 4.1.2).
5. The master sends a query to the trusted database requesting a
list of available WS channels based upon its geolocation. Query
parameters may include the master's location, device identifier,
and antenna height.
6. The database responds to the master's query with a list of
available white space spectrum, associated maximum power levels,
and a duration of time for its use.
7. The slave devices may query the master for a channel list. The
master may relay available-spectrum requests to the database on
behalf of slave devices, then transmit the obtained available-
spectrum lists to the slaves (or the master may allocate spectrum
to slaves from the obtained spectrum lists).
8. Once a slave device has been allocated available white space
spectrum frequencies for communication over the network, it may
inform the master of the frequencies and power level it has
chosen, and the master may, in turn, relay such usage to the
database.
9. Further communication among masters and slaves over the network
occurs via the selected/allocated white space spectrum
frequencies.
4.1.2. 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 Internet connectivity
service is provided over white space as a supplemental or alternative
datapath to a more costly Internet connection (metered wire service,
metered wireless service, metered satellite service). In a typical
deployment scenario, an end user has a primary Internet connection,
but may prefer to use a connection to the Internet provided by a
local white space master device that is connected to the Internet.
Figure 3 (Figure 3) shows an example deployment of this scenario.
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\|/
|
|
|------------|
/| Master | \
(Air)-/ |------------| \
--------- / \ -----------
|Slave |/ \ (----) | 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 the a metered Internet connection to the a WS connection
consists of the following steps:
1. The slave device connects to a metered Internet service, and
selects a video for streaming.
2. The slave device switches mode and associates with a master white
space device.*
3. The master queries the database for available white space
spectrum and relays it to the slave device as described in
Section 4.1.1.*
4. The slave uses available white space spectrum to communicate with
the master and connect to the Internet to stream the selected
video.
* Note that the slave device may query the database directly for
available white space spectrum through its metered connection to the
Internet, thus eliminating steps 2 and 3.
4.1.3. 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
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space master/slave network providing backhaul connectivity to the
Internet. Note that Wi-Fi is referenced in Figure 4 (Figure 4) and
the following discussion, but any other technology can be substituted
in its place.
Figure 4 (Figure 4) shows an example 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 (WS + 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 (WS + Wi-Fi) is connected to a master
device operating in the WS spectrum (the master obtains available
white space spectrum as described in Section 4.1.1).
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.
4.1.4. Rapid network deployment during emergency scenario
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 the 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,
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wireless ad-hoc network radios working independent of a fixed
infrastructure, and satellite links for backup where lack of
coverage, overload, or outage of wireless access links can occur.
Figure 5 (Figure 5) shows an example deployment of this scenario.
\|/
| ad hoc
|
|-|-------------|
| Master node | |------------|
\|/ | with | | Whitespace |
| 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: Rapid-deployed Network with Partly-connected Nodes
In the ad-hoc network, all nodes are master nodes that allocate RF
channels from the white space database (as described in
Section 4.1.1). 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
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.
4.1.5. 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
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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 4.1.1), 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 their portable device monitors.
Figure 6 (Figure 6) shows an example deployment of this scenario.
\|/ |------------|
| |White Space |
| Database |
| .---. / |------------|
|-----------| ( ) /
| Master | / \
| |========( Internet)
|-----------| \ /
| ( )
/|\ (---)
(White Space
Broadcast)
\|/ \|/ \|/ \|/ \|/ \|/ \|/
| | | | | | | .................
----- ----- ----- ----- ----- ----- -----
| | | | | | | | | | | | | |
| | | | | | | | | | | | | |
----- ----- ----- ----- ----- ----- -----
USB TV receivers connected to laptops, cellphone, tablets ....
Figure 6: White Space Used for Local TV Broadcast
5. 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. The databases may be regulatory specific
since the available spectrum and regulations may vary, but the
fundamental operation of the protocol should be regulatory
independent.
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An example high-level architecture of the devices and white space
databases is shown in Figure 7 (Figure 7).
-----------
| Master |
|WS Device| ------------
|Lat: X |\ .---. /--------|Database X|
|Long: Y | \ ( ) / ------------
----------- \-------/ \/ o
( Internet) o
----------- /------( )\ o
| Master | / ( ) \
|WS Device|/ (_____) \ ------------
|Lat: X | \--------|Database Y|
|Long: Y | ------------
-----------
Figure 7: High-level View of White Space Database Architecture
In Figure 11, note that there could be multiple databases serving
white space devices. The databases are locale specific since the
regulations and available spectrum may vary. In some countries, for
example, 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.
5.1. 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
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:
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1. Radio/air interface agnostic - The radio/air interface technology
used by the white space device in available spectrum can be IEEE
802.11af, IEEE 802.15.4m, IEEE 802.16, IEEE 802.22, LTE etc.
However the messaging interface between the white space device
and the database should be agnostic to the air interface while
being cognizant of the characteristics of various air-interface
technologies and the need to include relevant attributes in the
query to the database.
2. Spectrum agnostic - the spectrum used by primary and secondary
users varies by country. Some spectrum has 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 locale where such spectrum is available and a common
interface ensures uniformity in implementations and deployment.
Since the White Space Device must know its geospatial location to
do a query, it is possible to determine which database, and which
rules, are applicable, even though they are locale specific.
Note that although a device may know its geolocation, it may not
know the country or regulatory domain that it is in. Further,
even if the device knows this information, it may not be
sufficient for the device to know its expected behaviour in its
domain of operation since one domain may adopt a rule set for
white space device operation from another regulatory domain
(Brazil may adopt the "FccWhitespace2010" US rule set). To allow
the global use of white space devices in different countries
(whatever the regulatory domain), the protocol should support the
Database communicating applicable rule set information to the
white space device.
4. Flexible and extensible data structures - Different databases are
likely to have different requirements for the kinds of data
required for registration (different 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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5.2. Database discovery
Another aspect of the problem space is the need to discover the
database. A white space device needs to find the relevant database
to query, based on its current location or for another location.
Since the spectrum and databases are domain specific, the device will
need to discover the relevant database. The device needs to
determine the location of the specific database to which it can send
queries in addition to registering itself for operation and using the
available spectrum.
5.3. 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.
5.4. Data model definition
The contents of the queries and response need to be specified. A
data model is required which enables 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 and 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.
6. Requirements
6.1. Data Model Requirements
D.1 The Data Model MUST support specifying the geolocation of the
WSD, the uncertainty in meters, the height & its uncertainty,
and confidence in percentage of the location determination.
The Data Model MUST support WGS84 (see NGA: DoD World Geodetic
System 1984 [3]).
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 its current location.
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D.3 The Data Model MUST support device description data that
identifies a device (serial number, certification IDs, etc.)
and describes device characteristics, such as or 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 subject, such as:
antenna height
antenna gain
maximum output power, EIRP (dBm)
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 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, name of transmitter operator, postal
address, email address and phone number of the transmitter
operator.
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).
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D.9 The Data Model MUST support specifying the frequencies and
power levels selected for use by a device in the
acknowledgement message.
6.2. Protocol Requirements
P.1 The address of a database (e.g., in form of a URI) can be
preconfigured in a master device. The master device MUST be able
to contact a database using a pre-configured database address.
The master device may validate the database against a list of
approved databases maintained 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 the current location or the master (or slave)
device(s).
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.
P.7 The protocol MUST support the master device registering with the
database (see Device Registration (Section 3.1.2)).
P.8 The protocol MUST support a registration acknowledgement
including appropriate result codes.
P.9 The protocol MUST support an available spectrum request from the
master device to the database. These parameters MAY include any
of the parameters and attributes required to be supported in the
Data Model Requirements.
P.10 The protocol MUST support an available spectrum response from
the database to the master device. These parameters MAY include
any of the parameters and attributes required to be supported in
the Data Model Requirements.
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P.11 The protocol MUST support a spectrum usage message from the
master device to the database. These parameters MAY include any
of the parameters and attributes required to be supported in the
Data Model Requirements.
P.12 The protocol MUST support a spectrum usage message
acknowledgement.
P.13 The protocol MUST support a validation request from the master
to the database to validate a slave device. The validation
request MUST include the slave device ID.
P.14 The protocol MUST support a validation response from the
database to the master to indicate if the slave device is
validated by the WSDB. The validation response MUST include a
response code.
P.15 The protocol between the master device and the database MUST
support the capability to change spectrum availability information
on short notice.
P.16 The protocol between the master device and the database MUST
support a spectrum availability request which specifies a
geographic location as an area as well as a point
6.3. Operational Requirements
This section contains operational requirements of a white space
database-device system, independent of the requirements of the
protocol for communication between the white space database and
devices.
O.1 The database and the master device MUST be connected to the
Internet.
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 or have the capability to
determine its location to the required accuracy. A mobile master
device MUST have the capability to determine its location to the
required accuracy.
O.3 The master device MUST identify a database to which it will
register, make spectrum availability requests, etc... The master
device MAY select a database for service by discovery at runtime
or the master device MAY select a database for service by means of
a pre-programmed URI address.
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O.4 The master device MUST implement at least one connection method
to access the database. The master device MAY contact a database
directly for service or the master device MAY contact a database
listing server first followed by contact to a database.
O.5 The master device MUST obtain an information on the rule set of
the regulatory body that applies to the master device at its
current location (and/or the location of any slave devices on
whose behalf the master device is operating).
O.6 The master device MAY register with the database according to
local regulatory policy. Not all master devices will be required
to register. Specific events will initiate registration, these
events are determined by regulator policy (e.g., at power up,
after movement, etc...). When local regulatory policy requires
registration, the master device MUST register with its most
current and up-to-date information, and MUST include all variables
mandated by local regulator policy.
O.7 A master device MUST query the database for the available
spectrum based on its current location before starting radio
transmission in white space. Parameters provided to the database
MAY include device location, accuracy of the location, antenna
characteristic information, device identifier of any slave device
requesting spectrum information, etc.
O.8 The database MUST respond to an available spectrum list request
from an authenticated and authorized device and MAY also provide
time constraints, maximum output power, start and stop frequencies
for each band in the list and any additional requirements for
sensing.
O.9 According to local regulator policy, a master device MAY inform
the database of the actual frequency usage of the master and its
slaves. The master MUST include parameters required by local
regulatory policy, e.g., device ID, manufacturer's serial number,
spectrum usage and power level information of the master and its
slaves.
O.10 After connecting to a master device's radio network a slave
device MUST query the master device for a list of available
spectrum. The slave MUST include parameters required by local
regulatory policy, e.g., device ID, device location.
O.11 According to local regulatory policy, the master device MAY
query the database with parameters received from the slave device.
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O.12 The database MUST respond to a query from the master device
containing parameters from a slave device.
O.13 A master device MUST repeat the query to the database for the
available spectrum as often as required by the regulation (e.g.,
FCC requires once per day) to verify that the operating channels
continue to remain available.
O.14 A master device which changes its location more than a
threshold distance (specified by local regulatory policy) during
its operation, MUST query the database for available operating
spectrum each time it moves more than the threshold distance
(e.g., FCC specifies 100m) from the location it previously made
the query.
O.15 According to local regulator policy, a master device may
contact a database via proxy service of another master device.
O.16 A master device MUST be able to query the whitespace database
for spectrum availability information for a specific expected
coverage area around its current location.
O.17 A Master device MUST include its unique identity in all message
exchanges with the database.
6.4. Guidelines
The current scope of the working group is limited and is reflected in
the requirements captured in Section 6.1. However white space
technology itself is expected to evolve and address other aspects
such as co-existence 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 out
messaging specific, administrative specific, and spectrum
specific parts into separate modules.
2. The protocol SHOULD support determination of which administrative
specific and spectrum specific modules are used.
7. IANA Considerations
This document makes no request of IANA.
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8. Security Considerations
PAWS is a protocol whereby a Master Device requests a schedule of
available spectrum at its location (or location of its Slave Devices)
before it (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:
It is assumed that an attacker has full access to the network
medium between the master device and the white space database.
The attacker may be able to eavesdrop on any communications
between these entities. The link between the master device and
the white space database can be wired or wireless and provides
IP connectivity.
It is assumed that both the master device and the white space
database have NOT been compromised from a security standpoint.
Threat 1: User modifies a device to masquerade as another valid
certified device
Regulatory environments require that devices be certified and
register in ways that accurately reflect their certification.
Without suitable protection mechanisms, devices could simply
listen to registration exchanges, and later registering
claiming to be those other devices. Such replays would allow
false registration, violating regulatory regimes. A white
space database may be operated by a commercial entity which
restricts access only to authorized users. A master device MAY
need to identify itself to the database and be authorized to
obtain information about available spectrum.
Threat 2: Spoofed white space database
A master device discovers a white space database(s) through
which it can query for available spectrum information. The
master device needs to ensure that the white space database
with which it communicates with is an authentic entity. The
white space database needs to provide its identity to the
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master device which can confirm the validity/authenticity of
the database. An attacker may attempt to spoof a white space
database and provide responses to a master device which are
malicious and result in the master device causing interference
to the primary user of the spectrum.
Threat 3: Modifying a query request
An attacker may modify the query request sent by a master
device to a white space database. The attacker may change the
location of the device or the capabilities in terms of its
transmit power or antenna height etc., which could result in
the database responding with incorrect information about
available spectrum or max transmit power allowed. The result
of such an attack is that the master device would cause
interference to the primary user of the spectrum. It could
also result in a denial of service to the master device by
indicating that no channels are available.
Threat 4: Modifying a query response
An attacker could modify the query response sent by the white
space database to a master device. The available spectrum
information or transmit power allowed type of parameters
carried in the response could be modified by the attacker
resulting in the master device using spectrum that is not
available at a location or transmitting at a greater power
level than allowed resulting in interference to the primary
user of that spectrum. Alternatively the attacker may indicate
no spectrum availability at a location resulting in a denial of
service to the master device.
Threat 5: Third party tracking of white space device location and
identity
A white space database in a regulatory domain may require a
master device to 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
tracking purposes. A master device may prefer to keep the
location/identity information hidden from eavesdroppers, hence
the protocol should provide a means to protect the location and
identity information of the master device and prevent tracking
of locations associated with a white space database query.
When the master device sends both its identity and location to
the DB, the DB is able to track it. If a regulatory domain
does not require the master device to provide its identity to
the white space database, the master device may decide not to
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send its identity, to prevent being tracked by the DB.
Threat 6: Malicious individual acts as a PAWS entity (spoofing DB
or as MiM) to terminate or unfairly limit spectrum access of
devices for reasons other than incumbent protection
A white space database MAY include a mechanism by which service
and spectrum allocated to a master device can be revoked by
sending an unsolicited message. A malicious node can pretend
to be the white space database with which a master device has
registered or obtained spectrum information from and send a
revoke message to that device. This results in denial of
service to the master device.
Threat 7: Natural disaster resulting in inability to obtain
authorization for white space spectrum use by emergency responders
In the case of a sizable natural disaster a lot of Internet
infrastructure ceases to function, emergency services users
need to reconstitute quickly and will rely on establishing
radio WANs. In such cases, radio WAN gear that has been unused
suddenly needs to be pressed into action. And the radio WANs
need frequency authorizations to function. Regulatory entities
may also authorize usage of additional spectrum in the affected
areas. The white space radio entities may need to establish
communication with a database and obtain authorizations. In
cases where communication with the white space database fails,
the white space devices cannot utilize white space spectrum.
Emergency services, which require more spectrum precisely at
locations where network infrastructure is malfunctioning or
overloaded, backup communication spectrum and distributed white
space databases are needed to overcome such circumstances.
Alternatively there may be other mechanisms which allow the use
of spectrum by emergency service equipment without strict
authorization or with liberal interpretation of the regulatory
policy for white space usage.
The security requirements arising from the above threats are captured
in the requirements of Section 6.1 (Section 6.1).
9. Summary and Conclusion
Wireless spectrum is a scarce resource. As the demand for spectrum
grows, there is a need to more efficiently utilize the available and
allocated spectrum. Cognitive radio technologies enable the
efficient usage of spectrum via means such as sensing or by querying
a database to determine available spectrum at a given location for
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opportunistic use. "White space" is the general term used to refer
to the bands within the spectrum which are available for secondary
use at a given location. In order to use this spectrum, a device
needs to query a database that maintains information about the
available spectrum within a band. A protocol is necessary for
communication between the devices and databases that is globally
applicable.
The document describes some examples of the role of the white space
database in the operation of a radio network, and also provides
examples of services provided to the user of a white space device.
From these use cases, requirements are determined. These
requirements are to be used as input for the development of a
Protocol to Access White Space database (PAWS).
10. Acknowledgements
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, Pete Resnick,
Brian Rosen, Andy Sago, Peter Stanforth, John Stine and, Juan Carlos
Zuniga for their contributions to this document.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11.2. Informational References
URIs
[1]
[2]
[3]
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Authors' Addresses
Anthony Mancuso (editor)
Scott Probasco
Phone:
Fax:
Email: scott@probasco.me
URI:
Basavaraj Patil
Phone:
Fax:
Email: bpatil@ovi.com
URI:
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