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RFC 6953 - Protocol to Access White-Space (PAWS) Databases: Use


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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.

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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   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

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]).

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.

   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].

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

   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.

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.

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.

   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.

   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.

   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;

           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.

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

   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

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.

   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.

   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.

   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.

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

         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.

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.

Authors' Addresses

   Anthony Mancuso (editor)
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA  94043
   US

   EMail: amancuso@google.com

   Scott Probasco

   EMail: scott@probasco.me

   Basavaraj Patil
   Cisco Systems
   2250 East President George Bush Highway
   Richardson, TX  75082
   US

   EMail: basavpat@cisco.com

 

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