Providing secondary access to licensed spectrum through coordination

Most wireless systems receive a license that gives them exclusive access to a block of spectrum. Exclusivity guarantees adequate quality of service, but it also leads to inefficient use of spectrum. Even when the license holder is idle, no other device can use the spectrum. This paper explores an alternative paradigm for secondary access to spectrum, where a secondary device can transmit when and only when the primary license holder grants permission. In this spectrum usage paradigm, each secondary device makes a request for temporary access to spectrum by providing a primary license holder with information such as its required bandwidth, its required signal to interference ratio, its transmit power, and its location, which is essential for a primary license holder in making an admission decision. This explicit coordination makes it possible to protect the quality of service of both primary and secondary, while gaining the efficiency of spectrum sharing. In this paper, we consider the case where the primary license holder is a GSM-based cellular carrier. We show that our proposed sharing scheme works well even with simple admission control and primitive frequency assignment algorithms. Moreover, imprecise location information does not significantly undermine the performance of our scheme. We also demonstrate that our scheme is attractive to a license holder by showing that a cellular carrier can profit from offering a secondary device access to spectrum at a price lower than it would normally charge a cellular call. Sooksan Panichpapiboon is currently a Ph.D. candidate in the Electrical and Computer Engineering (ECE) Department at Carnegie Mellon University (CMU), Pittsburgh, PA. He received both B.S. and M.S. degrees in electrical and computer engineering from CMU in 2000 and 2002, respectively. His research interests include wireless networks, sensor networks, and performance modeling. Home page: www.andrew.cmu.edu/~sooksan Jon M. Peha (M 87, SM 96) is Associate Director of the CMU Center for Wireless and Broadband Networking at Carnegie Mellon University, and a Full Professor in the Department of Engineering and Public Policy and the Department of Electrical and Computer Engineering. He has served as Chief Technical Officer of successful networking start-ups with products related to wireless networks, video and voice over IP, and secure network payment systems. He has been a member of Legislative Staff in the US Congress, and a member of technical staff at SRI International, AT&T Bell Laboratories, and Microsoft. Dr. Peha also launched a US Government program to assist developing countries with information infrastructure. He holds a Ph.D. in electrical engineering from Stanford. Home page: www.ece.cmu.edu/~peha