tailieunhanh - Báo cáo hóa học: " Research Article Throughput Maximization under Rate Requirements for the OFDMA Downlink Channel with Limited Feedback"

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 Throughput Maximization under Rate Requirements for the OFDMA Downlink Channel with Limited Feedback | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2008 Article ID 437921 14 pages doi 2008 437921 Research Article Throughput Maximization under Rate Requirements for the OFDMA Downlink Channel with Limited Feedback Gerhard Wunder 1 Chan Zhou 1 Hajo-Erich Bakker 2 and Stephen Kaminski2 1 Fraunhofer German-Sino Lab for Mobile Communications Fraunhofer Institute for Telecommunications Heinrich-Hertz-Institut Einstein-Ufer 37 10587Berlin Germany 2 Alcatel-Lucent Research Innovation Holderaeckerstrasse 35 70499 Stuttgart Germany Correspondence should be addressed to Gerhard Wunder wunder@ Received 1 May 2007 Revised 12 July 2007 Accepted 26 August 2007 Recommended by Arne Svensson The purpose of this paper is to show the potential of UMTS long-term evolution using OFDM modulation by adopting a combined perspective on feedback channel design and resource allocation for OFDMA multiuser downlink channel. First we provide an efficient feedback scheme that we call mobility-dependent successive refinement that enormously reduces the necessary feedback capacity demand. The main idea is not to report the complete frequency response all at once but in subsequent parts. Subsequent parts will be further refined in this process. After a predefined number of time slots outdated parts are updated depending on the reported mobility class of the users. It is shown that this scheme requires very low feedback capacity and works even within the strict feedback capacity requirements of standard HSDPA. Then by using this feedback scheme we present a scheduling strategy which solves a weighted sum rate maximization problem for given rate requirements. This is a discrete optimization problem with nondifferentiable nonconvex objective due to the discrete properties of practical systems. In order to efficiently solve this problem we present an algorithm which is motivated by a weight matching strategy stemming from a Lagrangian .