tailieunhanh - Báo cáo hóa học: " Research Article Practical Approaches to Adaptive Resource Allocation in OFDM Systems"

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 Practical Approaches to Adaptive Resource Allocation in OFDM Systems | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008 Article ID 160307 10 pages doi 2008 160307 Research Article Practical Approaches to Adaptive Resource Allocation in OFDM Systems N. Y. Ermolova and B. Makarevitch Department of Electrical and Communications Engineering Helsinki University of Technology . Box 3000 02015 TKK Finland Correspondence should be addressed to N. Y. Ermolova Received 30 April 2007 Revised 6 September 2007 Accepted 28 September 2007 Recommended by Luc Vandendorpe Whenever a communication system operates in a time-frequency dispersive radio channel the link adaptation provides a benefit in terms of any system performance metric by employing time frequency and in case of multiple users multiuser diversities. With respect to an orthogonal frequency division multiplexing OFDM system link adaptation includes bit power and subcarrier allocations. While the well-known water-filling principle provides the optimal solution for both margin-maximization and ratemaximization problems implementation complexity often makes difficult its application in practical systems. This paper presents a few suboptimal low-complexity adaptive loading algorithms for both single- and multiuser OFDM systems. We show that the single-user system performance can be improved by suitable power loading and an algorithm based on the incomplete channel state information is derived. At the same time the power loading in a multiuser system only slightly affects performance while the initial subcarrier allocation has a rather big impact. A number of subcarrier allocation algorithms are discussed and the best one is derived on the basis of the order statistics theory. Copyright 2008 N. Y. Ermolova and B. Makarevitch. 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 .