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Versions: 00 01 02                                                      
Individual Submission                                      B. Patil, Ed.
Internet-Draft
Intended status: Informational                               S. Probasco
Expires: January 12, 2012                                       G. Bajko
                                                                   Nokia
                                                                B. Rosen
                                                                 Neustar
                                                           July 11, 2011


       Protocol to Access White Space database: Problem statement
                    draft-patil-paws-problem-stmt-02

Abstract

   Governments around the world continue to search for new bands of
   radio spectrum which can be used by the expanding wireless
   communications industry to provide more services in the usable
   spectrum.  The concept of allowing secondary transmissions (licensed
   or unlicensed) in frequencies occupied by a primary user is a
   technique to "unlock" existing spectrum for new use.  An obvious
   requirement is that these secondary transmissions do not interfere
   with the primary 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 allocated to them.  The available spectrum
   for a secondary use 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 primary spectrum
   is available for secondary use.  Academia and Industry have studied
   multiple cognitive radio mechanisms for use in such a scenario.  One
   simple mechanism is to use a geospatial database that records the
   primary users occupation, and require the secondary users to check
   the database prior to selecting what part of the spectrum they use.
   Such databases could be available on the Internet for query by
   secondary users.  This document discusses the problems that need to
   be addressed for enabling the use of white space spectrum by
   obtaining information from such a database.

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-
   Drafts is at http://datatracker.ietf.org/drafts/current/.




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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 January 12, 2012.

Copyright Notice

   Copyright (c) 2011 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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   described in the Simplified BSD License.






























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Prior Work . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     3.1.  The concept of Cognitive Radio . . . . . . . . . . . . . .  7
     3.2.  Background information on white space in US  . . . . . . .  8
     3.3.  Air Interfaces . . . . . . . . . . . . . . . . . . . . . .  8
   4.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Global applicability . . . . . . . . . . . . . . . . . . .  9
     4.2.  Database discovery . . . . . . . . . . . . . . . . . . . . 10
     4.3.  Data model definition  . . . . . . . . . . . . . . . . . . 11
     4.4.  Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 11
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   7.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 12
   9.  Informative References . . . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
































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1.  Introduction

   Spectrum useable for data communications, especially wireless
   Internet communications, is scarce.  One area which has received much
   attention globally is the TV white space: portions of the TV band
   that are not used by broadcasters in a given area.  In 2008 the
   United States regulator (the FCC) took initial steps when they
   published their first ruling on the use of TV white space, and then
   followed it up with a final ruling in 2010[FCC ruling].  Finland
   passed an Act in 2009 enabling testing of cognitive radio systems in
   the TV white space.  The ECC has completed Report 159 [ECC Report
   159] containing requirements for operation of cognitive radio systems
   in the TV white space.  Ofcom published in 2004 their Spectrum
   Framework Review [Spectrum Framework Review] and their Digital
   Dividend Review [DDR] in 2005, and have followed up with a proposal
   to access TV white space.  More countries are expected to provide
   access to their TV spectrum in similar ways.  Any entity holding
   spectrum that is not densely used may be asked to give it up in one
   way or another for more intensive use.  Providing a mechanism by
   which secondary users share the spectrum with the primary user is
   attractive in many bands in many countries.

   The concept of allowing secondary transmissions in frequencies
   occupied by a primary user is a technique to "unlock" existing
   spectrum for new use.  An obvious requirement is that these secondary
   transmissions do not interfere with the primary use of the spectrum.
   The fundamental issue is how to determine for a specific location and
   specific time if any of the spectrum is available for secondary use.
   There are two dimensions of use that may be interesting: space (the
   area in which a secondary user would not interfere with a primary
   user, and time: when the secondary use would not interfere with the
   primary use.  In this discussion, we consider the time element to be
   relatively long term (hours in a day) rather than short term
   (fractions of a second).  Location in this discussion is geolocation:
   where the transmitters (and sometimes receivers) are located relative
   to one another.  In operation, the database records the existing
   user's transmitter (and some times receiver) locations along with
   basic transmission characteristics such as antenna height, and
   sometimes power.  Using rules established by the regulator, the
   database calculates an exclusion zone for each authorized primary
   user, and attaches a time schedule to that use.  The secondary user
   queries the database with it location.  The database intersects the
   exclusion zones with the querier location, and returns the portion of
   the spectrum not in any exclusion zone.  Such methods of geospatial
   database query to avoid interference have been shown to achieve
   favorable results, and are thus the basis for rulings by the FCC and
   reports from ECC and Ofcom.  In any country, the rules for which
   primary entities are entitled to protection, how the exclusion zones



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   are calculated, and what the limits of use by secondary entities are
   may vary.  However, the fundamental notion of recording primary
   users, calculating exclusion zones, querying by location and
   returning available spectrum (and the schedule for that spectrum) are
   common.

   In a typical implementation of geolocation and database to access TV
   white space, a radio is configured with its location in latitude and
   longitude.  There are multiple ways to configure this location
   information, e.g. programmed at installation (e.g. for a fixed
   device) or determined by GPS (e.g. for a or mobile device).  At
   power-on, before the device can transmit in TV white space
   frequencies, the device must contact a database, provide its
   geolocation and receive in return a list of unoccupied or "white
   space" spectrum (for example, in a TV White space implementation, the
   list of available channels at that location).  The device can then
   select one of the channels from the list (note that it is possible
   they list is empty; there are no unoccupied channels at the location
   of the device) and then begins to transmit and receive on the
   selected channel.  The device must query the database again for a
   list of unoccupied channels based on certain conditions, e.g. a fixed
   amount of time has passed, the device has changed location beyond a
   specified threshold.  The basic scenario is that before transmitting
   in TV white space, the device must get permission from the database.

   This arrangement assumes that the device querying can complete a
   query before it transmits, or some other entity is able to query the
   database.  A common arrangement for this kind of service is a fixed
   tower with a wired infrastructure that provides Internet service to a
   network of client devices.  In this scenario, the tower has Internet
   access from its upstream service, and can query the database for
   channels within the tower service area.  It can then provide beacon
   service to its clients, and assign them channels within the list of
   channels that the tower gets from the database.

   Another arrangement might be an ad-hoc mobile network where one or
   more members of the ad hoc network have an independent radio IP
   connection (perhaps a commercial cellular wireless data network)
   which can be used to query the database over the Internet.

   A third possibility is a mechanism where the database is accessed on
   a private IP network.

   The low frequencies of the TV bands (470-790 MHz) have good
   propagation characteristics.  At these low frequencies, a radio
   signal will travel ~3 times further than traditional WLAN at 2.5 GHz,
   assuming the same transmit power.  Because of these characteristics
   and new cognitive radio techniques, when TV white space becomes



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   available, this will enable new use cases and new business
   opportunities.  Not only is the capacity of new spectrum needed, but
   this propagation trait by itself makes TV white space attractive for
   providing broadband wireless access in rural, sparsely populated
   areas, as well as for extended range home hot-spot coverage (similar
   to WLAN today, but with improved coverage).  In addition to
   propagation characteristics, the geolocation database may provide new
   capabilities for devices that use TV white space.  When a device
   using TV white space registers its location in the database, this
   simple act makes the location of the device available for location
   based services.

   Other spectrum that might also be available for sharing using white
   space techniques exist in every country.  A great many primary users
   were allocated space a time when there were many fewer potential
   users of the space, and the primary users are not making efficient
   (in geospatial and time aspects) use of the space.  In the past,
   relocating existing primary users was the only feasible alternative.
   Using white space techniques to share spectrum without imposing
   burdens on the primary users is more attractive.

   This document discusses the problem statement related to enabling the
   "secondary" use of spectrum owned by a primary user without causing
   interference to the primary user(s).  One approach to avoiding
   interference is to verify with a database about the available
   channels and spectrum at a given location.  This document also
   identifies various issues that need to be addressed by the protocol
   between a white space device and such a database.


2.  Terminology

   White Space

      Radio spectrum which has been allocated for some primary use, but
      is not fully occupied by that primary use at a specific location
      and time.

   TV White Space

      TV white space refers specifically to radio spectrum which has
      been allocated for over the air television broadcast, but is not
      occupied by a TV broadcast, or other licensed user (such as a
      wireless microphone), at a specific location and time.







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   White Space Device

      A device which is a secondary user of some part of white space
      spectrum.  A white space device can be an access point, base
      station, a portable device or similar.  In this context, a white
      space device is required to query a database with its location to
      obtain information about available spectrum.

   TV White Space

      TV white space refers specifically to radio spectrum which has
      been allocated for TV broadcast, but is not occupied by a TV
      broadcast, or other licensed user (such as a wireless microphone),
      at a specific location and time.

   Database

      In the context of white space and cognitive radio technologies,
      the database is an entity which contains current information about
      available spectrum at any given location and other types of
      information.

   Protected Entity

      A primary user of white space spectrum which is afforded
      protection against interference by secondary users (white space
      devices( for its use in a given area and time.

   Protected Contour

      The exclusion area for a Protected Entity, held in the database
      and expressed as a polygon with geospatial points as the vertices.


3.  Prior Work

3.1.  The concept of Cognitive Radio

   A cognitive radio uses knowledge of the local radio environment to
   dynamically adapt its own configuration and function properly in a
   changing radio environment.  Knowledge of the local radio environment
   can come from various technology mechanisms including sensing
   (attempting to ascertain primary users by listening for them within
   the spectrum), location determination and internet connectivity to a
   database to learn the details of the local radio environment.  TV
   White Space is one implementation of cognitive radio.  Because a
   cognitive radio adapts itself to the available spectrum in a manner
   that prevents the creation of harmful interference, the spectrum can



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   be shared among different radio users.

3.2.  Background information on white space in US

   Television transmission in the United States has moved to the use of
   digital signals as of June 12, 2009.  Since June 13, 2009, all full-
   power U.S. television stations have broadcast over-the-air signals in
   digital only.  An important benefit of the switch to all-digital
   broadcasting is that it freed up parts of the valuable broadcast
   spectrum.  More information about the switch to digital transmission
   is at : [DTV].

   With the switch to digital transmission for TV, the guard bands that
   existed to protect the signals between stations can now be used for
   other purposes.  The FCC has made this spectrum available for
   unlicensed use and this is generally referred to as white space.
   Please see the details of the FCC ruling and regulations in [FCC
   ruling].  The spectrum can be used to provide wireless broadband as
   an example.  The term "Super-Wifi" is also used to describe this
   spectrum and potential for providing wifi type of service.

3.3.  Air Interfaces

   Efforts are ongoing to specify air-interfaces for use in white space
   spectrum.  IEEEs 802.11af task group is currently working on one such
   specification.  IEEE 802.22 is another example.  Other air interfaces
   could be specified in the future such as LTE.


4.  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 country specific since
   the available spectrum and regulations may vary, but the fundamental
   operation of the protocol should be country independent.

   An example high-level architecture of the devices and white space
   databases is shown in the figure below:









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           -----------
           |WS Device|                              ------------
           |Lat: X   |\           .---.    /--------|Database X|
           |Long: Y  | \         (     )  /         ------------
           -----------  \-------/       \/               o
                              ( Internet )               o
           -----------  /------(        )\               o
           |WS Device| /         (_____)  \         ------------
           |Lat: X   |/                    \--------|Database Y|
           |Long: Y  |                              ------------
           -----------


    Figure 1: High level view of the White space database architecture

   In the figure above, note that there could be multiple databases
   serving white space devices.  The databases are country specific
   since the regulations and available spectrum may vary.  In some
   countries, for example, the U.S., the regulator has determined that
   multiple, competing 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.  Other aspects of a solution
   including provisioning the database, and calculating protected
   contours are considered out of scope of the initial effort, as there
   are significant differences between countries and spectrum bands.

4.1.  Global applicability

   The use of TV white space spectrum is currently approved by the FCC
   in the United States.  However regulatory bodies in other countries
   are also considering similar use of available spectrum.  The
   principles of cognitive radio usage for such spectrum is generally
   the same.  Some of the regulatory details may vary on a country
   specific basis.  However the need for devices that intend to use the
   spectrum to communicate with a database remains a common feature.
   The database provides a known, specifiable Protection Contour for the
   primary user, not dependent on the characteristics of the White Space
   Device or it's ability to sense the primary use.  It also provides a
   way to specify a schedule of use, because 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



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   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.  Radio/air interface agnostic - The radio/air interface technology
       used by the white space device in available spectrum can be
       802.11af, 802.16, 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 protected entity 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 country where such spectrum is available and a common
       interface ensures uniformity in implementations and deployment.
       Since the White Space device must know it's geospatial location
       to do a query, it is possible to determine which database, and
       which rules, are applicable, even though they are country
       specific.

   4.  Address regulatory requirements - Each country will likely have
       regulations that are unique to that country.  The messaging
       interface needs to be flexible to accommodate the specific needs
       of a regulatory body in the country where the white space device
       is operating and connecting to the relevant database.

4.2.  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 country specific, the device
   will need to discover the relevant database.  The device needs to
   obtain the IP address of the specific database to which it can send
   queries in addition to registering itself for operation and using the
   available spectrum.




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   A database discovery mechanism needs to be specified.  Reuse of
   existing mechanisms is an option and could be adapted for meeting the
   specific needs of cognitive radio technology.

4.3.  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 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.

   Use of XML for specifying a data model is an attractive option.  The
   intent is to evaluate the best option that meets the need for use
   between white space devices and databases.

4.4.  Protocol

   The protocol requirements are simple: registration and query
   transactions are needed.  In some circumstances, a registration
   transaction is required prior to being able to query.  The device
   provides some identifying information, and the database responds with
   an acknowledgement or error.  The query protocol is a simple query/
   response action (primarily location in, available spectrum out), with
   some error conditions.

   It may be possible to use existing protocols (e.g.  LoST [RFC5222])
   or it may be more appropriate to define a new protocol for this
   purpose.  HTTP transport is probably appropriate.


5.  IANA Considerations

   This document has no requests to IANA.


6.  Security Considerations

   The messaging interface between the white space device and the
   database needs to be secured.  Both the queries and the responses
   need to be delivered securely.  The device must be certain it is
   talking to a bona fide database authoritative for the location and
   spectrum band the device operates on.  The database may need to
   restrict interactions to devices that it has some prior relationship
   with, or may be restricted from providing service to devices that are
   not authorized in some manner.



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   As the device will query with it's location, the location must be
   protected against eavesdropping.  Some regulations include personally
   identifiable information as required elements of registration and/or
   query and must similarly be protected.

   All communications between the device and the database will require
   integrity protection.

   Man-in-the-middle attacks could modify the content of a response
   which can cause problems for other networks or devices operating at a
   given location.  Interference as well as total loss of service could
   result from malicious information being delivered to a white space
   device.

   This document describes the problems that need to be addressed for a
   messaging interface between white space devices and databases and
   does not by itself raise any security concerns.


7.  Summary

   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 locaion for
   secondary use.  White space is the general term used to refer to the
   bands within the spectrum which is available for secondary use at a
   given location.  In order to use this spectrum a device needs to
   query a database which maintains information about the available
   channels within a band.  A protocol is necessary for communication
   between the devices and databases which would be globally applicable.


8.  Acknowledgments

   Thanks to ABC, PQR and XYZ for their comments and input which have
   helped in improving this document.


9.  Informative References

   [DDR]      Ofcom - Independent regulator and competition authority
              for the UK communications industries, "Digital Dividend
              Review; http://stakeholders.ofcom.org.uk/spectrum/
              project-pages/ddr/".

   [DTV]      "Digital TV Transition; http://www.dtv.gov".



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   [ECC Report 159]
              Electronic Communications Committee (ECC) within the
              European Conference of Postal and Telecommunications
              Administrations (CEPT), "TECHNICAL AND OPERATIONAL
              REQUIREMENTS FOR THE POSSIBLE OPERATION OF COGNITIVE RADIO
              SYSTEMS IN THE 'WHITE SPACES' OF THE FREQUENCY BAND 470-
              590 MHZ; http://www.erodocdb.dk/Docs/doc98/official/pdf/
              ECCREP159.PDF", January 2011.

   [FCC ruling]
              Federal Communications Commission, "Unlicensed Operation
              in the TV Broadcast Bands;
              http://edocket.access.gpo.gov/2010/pdf/2010-30184.pdf",
              December 2010.

   [RFC5222]  Hardie, T., Newton, A., Schulzrinne, H., and H.
              Tschofenig, "LoST: A Location-to-Service Translation
              Protocol", RFC 5222, August 2008.

   [Spectrum Framework Review]
              Ofcom - Independent regulator and competition authority
              for the UK communications industries, "Spectrum Framework
              Review;
              http://stakeholders.ofcom.org.uk/consultations/sfr/",
              February 2005.


Authors' Addresses

   Basavaraj Patil (editor)
   6021 Connection drive
   Irving, TX  75039
   USA

   Email: basavaraj.patil@nokia.com


   Scott Probasco
   Nokia
   6021 Connection drive
   Irving, TX  75039
   USA

   Email: scott.probasco@nokia.com







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   Gabor Bajko
   Nokia
   323 Fairchild drive 6
   Mountain view, CA  94043
   USA

   Email: gabor.bajko@nokia.com


   Brian Rosen
   Neustar
   470 Conrad Dr
   Mars, PA  16046
   USA

   Email: brian.rosen@neustar.biz



































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