To whom correspondence should be addressed. E-mail: suxi1982 @ gmail. com Su Xi, born in 1982, she is Ph. D candidate in Beijing University of Posts and Telecommunications. She received her B.S. and M.S. degrees from Shandong University and Tianjin University of technology, respectively. Her research interests include the design of spectrum allo- cation algorithms and the design of spectrum sensing mechanism in cognitive radio network.