tailieunhanh - Báo cáo hóa học: " Robust Downlink Power Control in Wireless Cellular 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: Robust Downlink Power Control in Wireless Cellular Systems | EURASIP Journal on Wireless Communications and Networking 2004 2 261-272 2004 Hindawi Publishing Corporation Robust Downlink Power Control in Wireless Cellular Systems Mehrzad Biguesh Department of Communication Systems University of Duisburg-Essen Bismarckstrasse 81 47057 Duisburg Germany Em ail biguesh@ Shahram Shahbazpanahi Department of Communication Systems University of Duisburg-Essen Bismarckstrasse 81 47057 Duisburg Germany Department of Electrical Computer Engineering McMaster University 1280 Main Street West Hamilton ON Canada L8S 4K1 Email shahbaz@ Alex B. Gershman Department of Communication Systems University of Duisburg-Essen Bismarckstrasse 81 47057 Duisburg Germany Department of Electrical Computer Engineering McMaster University 1280 Main Street West Hamilton ON Canada L8S 4K1 Email gershman@ Received 30 November 2003 Revised 13 July 2004 A serious shortcoming of current downlink power control methods is that their performance may be severely degraded when the downlink channel information is known imprecisely at the transmitter. In this paper a computationally and implementationally simple centralized downlink power control method is proposed for cellular wireless communication systems using code division multiple access CDMA or space division multiple access SDMA . Our method provides a substantially improved robustness against imperfect knowledge of the wireless channel by means of maintaining the required quality of service for the worst-case channel uncertainty. In the SDMA case the proposed technique can be straightforwardly combined with any of the existing transmit beamforming methods. Simulation results validate substantial robustness improvements achieved by our approach. Keywords and phrases power control cellular system CDMA SDMA downlink beamforming. 1. INTRODUCTION Power control is an intelligent way of adjusting the transmitted powers in cellular systems so that the total transmitted .