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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: Non-Data-Aided Feedforward Carrier Frequency Offset Estimators for QAM Constellations: A Nonlinear Least-Squares Approach | EURASIP Journal on Applied Signal Processing 2004 13 1993-2001 2004 Hindawi Publishing Corporation Non-Data-Aided Feedforward Carrier Frequency Offset Estimators for QAM Constellations A Nonlinear Least-Squares Approach Y. Wang Department of Electrical Engineering Texas A M University College Station TX 77843-3128 USA Email wangyan@ee.tamu.edu K. Shi Department of Electrical Engineering Texas A M University College Station TX 77843-3128 USA Email kaishi@ee.tamu.edu E. Serpedin Department of Electrical Engineering Texas A M University College Station TX 77843-3128 USA Email serpedin@ee.tamu.edu Received 21 February 2003 Revised 17 March 2004 Recommended for Publication by Tomohiko Taniguchi This paper performs a comprehensive performance analysis of a family of non-data-aided feedforward carrier frequency offset estimators for QAM signals transmitted through AWGN channels in the presence of unknown timing error. The proposed carrier frequency offset estimators are asymptotically large sample nonlinear least-squares estimators obtained by exploiting the fourthorder conjugate cyclostationary statistics of the received signal and exhibit fast convergence rates asymptotic variances on the order of O N-3 where N stands for the number of samples . The exact asymptotic performance of these estimators is established and analyzed as a function of the received signal sampling frequency signal-to-noise ratio timing delay and number of symbols. It is shown that in the presence of intersymbol interference effects the performance of the frequency offset estimators can be improved significantly by oversampling or fractionally sampling the received signal. Finally simulation results are presented to corroborate the theoretical performance analysis and comparisons with the modified Cramer-Rao bound illustrate the superior performance of the proposed nonlinear least-squares carrier frequency offset estimators. Keywords and phrases synchronization cyclostationary non-data-aided .
