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 interaction:
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 returning information.
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 available.
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 database.
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 include LDAP.
- 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.
Submit 'Use Cases and Requirements for Accessing a Radio White Space Database' to the IESG for publication as Informational
Submit 'Accessing a Radio White Space Database' to the IESG for publication as Proposed Standard