Radio spectrum is a limited resource. National and international
bodies assign different frequencies for specific uses, and in
most cases license the rights to use these frequencies. Locally
unused spectrum is commonly called "white space" and may be made
available to other services on a basis of non-interference with
the primary user of the frequencies concerned (if any). This
technique can help "unlock" existing spectrum, for example to
enable the wireless communications industry to provide more
services over frequencies associated with unused television
channels. An obvious requirement is that white space uses must
not interfere with the primary use of the spectrum. This is
achieved through spatial and/or temporal separation of the
primary user and whitespace user with due consideration made to
the radio characteristics of the two uses.
The fundamental problem is enabling a radio device to determine, in
a specific location and at specific time, if any white space is
available for secondary use. There are two parties to such an
1. A database containing records about the protected contours (in
space and time) of primary spectrum users. Typically, such databases
will be populated by information provided by the appropriate spectrum
regulation bodies and by spectrum licensees.
2. A radio device that wishes to query such a database. Typically, the
nature of the query will depend on the needs of the device.
The contents of white space databases, and the needs of radio devices,
are being defined elsewhere. However, these parties need a protocol
for communication that will enable radio devices to find out what white
space is available at a given time in a given location.
It is expected that white space databases will be reachable via the
Internet, and that radio devices too will have some form of Internet
connectivity, directly or indirectly. Therefore, it is appropriate
to define an Internet-based protocol for querying white space databases
and receiving responses from such databases.
In rough outline, such a protocol would enable a radio device that
knows its location and the current time to complete the following tasks:
1. Determine the relevant white space database to query.
2. Connect to the database using a well-defined communication method.
3. Provide its geolocation and perhaps other data to the database
using a well-defined format for querying the database.
4. Receive in return a list of available white space spectrum
with their characteristics, using a well-defined format for
5. Report to the white space database anticipated spectrum usage
at a suitable granularity.
Once the device learns of the available white space (e.g., in a TV
white space implementation, the list of available channels at that
location), it can then select one of the bands from the list and
begin to transmit and receive on the selected band. If the device's
parameters have changed (e.g., if some amount of time has passed or if
the device has changed location beyond a specified threshold), it might
need to query the database again to determine what white space is still
The overall goals of this working group are to:
1. Standardize a mechanism for discovering a white space database.
2. Standardize a method for communicating with a white space
3. Standardize the data formats to be carried over the defined
database communication method.
4. Ensure that the discovery mechanism, database access method,
and query/response formats have appropriate security levels in place.
By "standardize" is not meant that the working group will necessarily
develop new technologies. In completing its work, the group will:
- Evaluate existing discovery mechanisms to determine if one of
them provides the necessary application features and security
properties (or can be extended to do so) for discovering a
white space database. Examples might include DNS.
- Evaluate existing application-layer transport protocols to
determine if one of them provides the necessary application
features and security properties (or can be extended to do so)
for use as a building block for communication between location-
aware devices and white space databases. If such a method
exists, the group will reuse it; if not, the group will develop
one. Examples might include HTTP.
- Develop a method for querying a white space database. Such
a method will utilize, so far as possible, the features of
the application-layer transport protocol and not re-implement
them in the new protocol. It will include mechanisms to verify
that the requests and responses come from authorized sources,
and that they have not been modified in transit. Examples might
- Define extensible formats for both location-specific queries and
location-specific responses for interaction with radio white
space databases. The group will consider whether existing data
formats can be reused.
The protocol must protect both the channel enablement process and the
privacy of users. Robust privacy and security mechanisms are needed
to prevent: device identity spoofing, modification of device requests,
modification of channel enablement information, impersonation of
registered database services, and unauthorized disclosure of a device's
location. The group will consider whether existing privacy and
security mechanisms can be reused.
The task of defining the structure and contents of the databases
themselves is out of scope. The group will standardize formats for
communication between devices and databases, but not the information
models for the databases, since those models are likely to be
country-specific or application-specific. In addition, the particular
data exchanged between a device and a database might depend on the
ranges of radio spectrum that are to be used, the requirements of the
database operators and their governing regulations, and other factors.
Therefore, the database access method and the query/response data
formats that are exchanged using that method need to be designed for
extensibility rather than being tied to any specific spectrum, country,
or phy/mac/air interface. For example, the working group should define
extension points for the database access method and the query/response
formats, so that use cases other than those currently envisioned can be
addressed in the future if a community of interest wishes to do so.
However, the access method and query/response formats will incorporate
relevant aspects of the parameters needed for the currently envisioned
use cases to ensure proper operation.
In accordance with existing IETF processes, the group will communicate
and invite participation with other relevant standards bodies and
groups, and if necessary reuse existing liaison relationships or
request the establishment of new liaison relationships, including but
not limited to IEEE 802.11af and IEEE 802.22. In order to ensure that
it takes into account a broad range of possible use cases and
requirements, the group should also reach out to other potential
"customers" for a white space database access method and consider input
from regulatory entities that are involved in the specification of the
rules for secondary use of spectrum in specific radio bands.
1. A description of the relevant use cases and requirements. This
document shall be Informational. Subject to working group consensus,
draft-probasco-paws-overview-usecases and draft-patil-paws-problem-stmt
might be used as a starting point.
2. A specification of the mechanism for discovering a white space
database, the method for accessing a white space database, and the
query/response formats for interacting with a white space database.
This document shall be Standards Track.