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 Rate-Optimal and Reduced-Complexity Sequential Sensing Algorithms for Cognitive OFDM Radios | Hindawi Publishing Corporation EURASIP Journal on Advances in Signal Processing Volume 2009 Article ID 421540 11 pages doi 2009 421540 Research Article Rate-Optimal and Reduced-Complexity Sequential Sensing Algorithms for Cognitive OFDM Radios Seung-Jun Kim and Georgios B. Giannakis Department of Electrical and Computer Engineering University of Minnesota 200 Union Street SE Minneapolis MN 55455 USA Correspondence should be addressed to Georgios B. Giannakis georgios@ Received 19 February 2009 Revised 22 May 2009 Accepted 14 July 2009 Recommended by Ananthram Swami Sequential sensing algorithms are developed for OFDM-based hierarchical cognitive radio CR systems. Secondary users sense multiple subbands simultaneously for possible spectrum availabilities under hard misdetection constraints to prevent interference to the primary users. Accounting for the fact that the sensing time overhead can often be significant a novel performance metric is introduced based on the effective achievable data rate. An optimization problem is formulated in the framework of optimal stopping problems to maximize the average effective data rate by determining the best time to stop taking samples and proceed to data transmission. A basis expansion-based suboptimal algorithm is developed to reduce the prohibitive complexity of the optimal solution. The numerical results presented verify the efficacy of the proposed approach. Copyright 2009 . Kim and G. B. Giannakis. 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. 1. Introduction The cognitive radio CR paradigm aims to design intelligent radios that can sense the environment and adapt the transceiver parameters as well as the resource allocation decisions in order to exploit the spectrum availability aggressively 1 . The motivation stems from the observation .
