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| SDR-Based Blind Channel Estimation of Time-varying OFDM Systems |
| Fang Cheng-zhi①②; Du Si-dan①; Ni Liang-fang① |
| ①Department of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China;②College of Optoelectrical Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China |
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Abstract Some Quadratic Programs (QP) have been presented for the blind channel estimation and signal detection of the time-varying OFDM systems. In this paper a method is proposed to turn the QP problem into the optimization of a Semi-Definite Program (SDP) based on the Semi-Definite Relaxation (SDR) technique. Compared to the original QPs which reach the optimal solution with exponential complexity, the SDP could be solved efficiently in polynomial time. In order to reduce the complexity involved in the transform from the solution of the SDPs to the solution of the original QPs, the correlation property of the OFDM time-frequency response between adjacent subchannels or time-slots is exploited to devise a novel randomization strategy. The simulation proves the effectiveness of the new method.
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Received: 29 January 2007
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2008, Vol. 30 
