Spectrum Sharing Without Licenses: Opportunities and Dangers

Durga P. Satapathy and Jon M. Peha
Department of Electrical and Computer Engineering
Carnegie Mellon University

Abstract

The current spectrum management policy typically gives
exclusive and unlimited access to license-holders within
their domain, and offers meager transmission opportunities for
non-license-holders. This paper addresses spectrum management
techniques in which no licensing is required and individual devices
have real-time access to shared spectrum. An example is the
30 MHz of unlicensed spectrum allocated by the Federal Communications
Commission in the new Personal Communications Services band,
and industry is already requesting hundreds of MHz more of the
same. Such spectrum has several advantages. It eliminates
the delays of the licensing process. It facilitates mobility,
as a license is not required wherever a system may operate. It
also promotes spectrum sharing, as one device may transmit while
others in the area are idle. This paper discusses some of the
challenges to be overcome. Foremost among these is an inherent
Tragedy of the Commons resulting from the fact that device designers
lack an incentive to conserve the shared spectrum resource. This
phenomenon is quantitatively demonstrated in a practical scenario.
Some options for this problem are also discussed.