Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article A Unified Approach to Optimal Opportunistic Spectrum Access under Collision Probability Constraint in Cognitive Radio Systems | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2010 Article ID 148698 15 pages doi 2010 148698 Research Article A Unified Approach to Optimal Opportunistic Spectrum Access under Collision Probability Constraint in Cognitive Radio Systems Qinghai Xiao 1 2 Yunzhou Li 1 Xiaofeng Zhong 1 Xibin Xu 1 and Jing Wang1 1 State Key Laboratory on Microwave and Digital Communications Tsinghua National Laboratory for Information Science and Technology Department of Electronic Engineering Tsinghua University Beijing 100084 China 2 School of Electronic Technology Information Engineering University Zhengzhou 450004 China Correspondence should be addressed to Qinghai Xiao xiaotsinghai@ Received 29 April 2009 Revised 15 September 2009 Accepted 18 November 2009 Academic Editor Ying-Chang Liang Copyright 2010 Qinghai Xiao et al. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited. We consider a cognitive radio system with one primary channel and one secondary user and then we introduce a channel-usage pattern model and a fundamental access scheme in this system. Based on this model and fundamental access scheme we study optimal opportunistic spectrum access problem and formulate it as an optimization problem that the secondary user maximizes spectrum holes utilization under the constraint of collision tolerable level. And then we propose a unified approach to solve this optimization problem. According to the solution of the optimization problem we analyze and present optimal opportunistic spectrum access algorithms in several cases that the idle period follows uniform distribution exponential distribution and Pareto or generalized Pareto distribution. Theoretical analysis and simulation results both show that the optimal opportunistic spectrum access algorithms can maximize
