tailieunhanh - Báo cáo hóa học: " Rate-Optimal Multiuser Scheduling with Reduced Feedback Load and Analysis of Delay Effects"

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: Rate-Optimal Multiuser Scheduling with Reduced Feedback Load and Analysis of Delay Effects | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2006 Article ID 36424 Pages 1-7 DOI WCN 2006 36424 Rate-Optimal Multiuser Scheduling with Reduced Feedback Load and Analysis of Delay Effects Vegard Hassel 1 Mohamed-Slim Alouini 2 Geir E. 0ien 1 and David Gesbert3 1 Department of Electronics and Telecommunications Norwegian University of Science and Technology 7491 Trondheim Norway 2 Department of Electrical Engineering Texas A M University at Qatar TAMUQ Education City . Box 5825 Doha Qatar 3 Mobile Communications Department Eurecom Institute 06904 Sophia Antipolis France Received 30 September 2005 Revised 13 March 2006 Accepted 26 May 2006 We propose a feedback algorithm for wireless networks that always collects feedback from the user with the best channel conditions and has a significant reduction in feedback load compared to full feedback. The algorithm is based on a carrier-to-noise threshold and closed-form expressions for the feedback load as well as the threshold value that minimizes the feedback load have been found. We analyze two delay scenarios. The first scenario is where the scheduling decision is based on outdated channel estimates and the second scenario is where both the scheduling decision and the adaptive modulation are based on outdated channel estimates. Copyright 2006 Vegard Hassel 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. 1. INTRODUCTION In a wireless network the signals transmitted between the base station and the mobile users most often have different channel fluctuation characteristics. This diversity that exists between users is called multiuser diversity MUD and can be exploited to enhance the capacity of wireless networks 1 . One way of exploiting MUD is by opportunistic scheduling of users giving priority