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Báo cáo hóa học: " Bandwidth Efficient OFDM Transmitter Diversity Techniques"

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: Bandwidth Efficient OFDM Transmitter Diversity Techniques | EURASIP Journal on Applied Signal Processing 2004 10 1508-1519 2004 Hindawi Publishing Corporation Bandwidth Efficient OFDM Transmitter Diversity Techniques King F. Lee Multimedia Architecture Lab Motorola Labs Schaumburg IL 60196 USA Email king.lee@motorola.com Douglas B. Williams School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332-0250 USA Email douglas.williams@ece.gatech.edu Received 17 December 2002 Revised 2 September 2003 Space-time block-coded orthogonal frequency division multiplexing OFDM transmitter diversity techniques have been shown to be efficient means of achieving near-optimal diversity gain in frequency-selective fading channels. However these known techniques all require a cyclic prefix to be added to the transmitted symbols resulting in bandwidth expansion. In this paper iterative space-time and space-frequency block-coded OFDM transmitter diversity techniques are proposed that exploit spatial diversity to improve spectral efficiency by eliminating the need for a cyclic prefix. Keywords and phrases space-time coding space-frequency coding transmitter diversity OFDM channel estimation pilot symbols. 1. INTRODUCTION The last decade has witnessed an explosive growth of wireless communications especially in mobile communications and personal communications services PCS . With the continuing expansion in both existing and new markets and the introduction of exciting new services such as wireless internet access and multimedia applications the wireless communications market is expected to continue to grow at a rapid pace. Furthermore the ever-increasing demand for faster and more reliable services to support new applications has created strong interests in developing high data rate wireless communications systems. With existing and emerging wireless applications all competing for a limited radio spectrum the development of high data rate wireless communications systems that are spectrally efficient is .