tailieunhanh - Báo cáo hóa học: " Maximum Likelihood Turbo Iterative Channel Estimation for Space-Time Coded Systems and Its Application to Radio Transmission in Subway Tunnels"

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: Maximum Likelihood Turbo Iterative Channel Estimation for Space-Time Coded Systems and Its Application to Radio Transmission in Subway Tunnels | EURASIP Journal on Applied Signal Processing 2004 5 727-739 2004 Hindawi Publishing Corporation Maximum Likelihood Turbo Iterative Channel Estimation for Space-Time Coded Systems and Its Application to Radio Transmission in Subway Tunnels Miguel Gonzalez-Lopez Departamento de Electrónica y Sistemas Universidade da Coruna Campus de Elvina s n 15071 A Coruna Spain Email miguelgl@ Joaquin Miguez Departamento de Electrónica y Sistemas Universidade da Coruna Campus de Elvina s n 15071 A Coruna Spain Email jmiguez@ Luis Castedo Departamento de Electrónica y Sistemas Universidade da Coruna Campus de Elvina s n 15071 A Coruna Spain Email luis@ Received 31 December 2002 Revised 31 July 2003 This paper presents a novel channel estimation technique for space-time coded STC systems. It is based on applying the maximum likelihood ML principle not only over a known pilot sequence but also over the unknown symbols in a data frame. The resulting channel estimator gathers both the deterministic information corresponding to the pilot sequence and the statistical information in terms of a posteriori probabilities about the unknown symbols. The method is suitable for Turbo equalization schemes where those probabilities are computed with more and more precision at each iteration. Since the ML channel estimation problem does not have a closed-form solution we employ the expectation-maximization EM algorithm in order to iteratively compute the ML estimate. The proposed channel estimator is first derived for a general time-dispersive MIMO channel and then is particularized to a realistic scenario consisting of a transmission system based on the global system mobile GSM standard performing in a subway tunnel. In this latter case the channel is nondispersive but there exists controlled ISI introduced by the Gaussian minimum shift keying GMSK modulation format used in GSM. We demonstrate using experimentally measured channels that the training sequence length can be reduced