tailieunhanh - Báo cáo hóa học: " Multiuser Channel Estimation for Ultra-Wideband Systems Using up to the Second-Order Statistics"

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: Multiuser Channel Estimation for Ultra-Wideband Systems Using up to the Second-Order Statistics | EURASIP Journal on Applied Signal Processing 2005 3 273-286 2005 Hindawi Publishing Corporation Multiuser Channel Estimation for Ultra-Wideband Systems Using up to the Second-Order Statistics Zhengyuan Xu Department of Electrical Engineering University of California Riverside CA 92521 USA Email dxu@ Jin Tang Department of Electrical Engineering University of California Riverside CA 92521 USA Email jtang@ Ping Liu Department of Electrical Engineering Arkansas Tech University Russellville AR 72801 USA Email Received 27 September 2003 Revised 11 March 2004 In a pulse-position modulation-based ultra-wideband UWB communication system multiple access is enabled by assigning unique time-hopping sequences to different users. Each user s data information is carried by positions of short pulses which are directly transmitted through an unknown and possibly dense multipath channel. Single-user channel estimation methods have been proposed by maximum likelihood optimization that treats multiple access interference as Gaussian noise. In this paper multiuser channel estimation methods are proposed based on a pulse-rate discrete-time system model and up to the second-order statistics of the channel outputs. The model can be regarded in a trilinear structure and also resembles a code-division multipleaccess CDMA system with newly defined hopping-code dependent matrices and inputs for each user. Considering that either the mean or covariance of received signals contains sufficient information for all unknown channels least squares and covariance matching ideas are successfully applied to estimate all channels blindly. Accordingly closed-form solutions are derived. Those channel estimates can be used to design typical linear receivers. Performance of each proposed estimator is analyzed and also verified by computer simulations. Corresponding receivers performance is also studied numerically. Keywords and phrases ultra-wideband channel .

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