| Summary: | 碩士 === 國立臺灣海洋大學 === 通訊與導航工程學系 === 102 === The combination of MIMO, STBC and OFDM techniques, called the MIMO STBC-OFDM system, has becomes one of standards in the fourth-generation (4G) mobile wideband communication. Recently, the subspace decomposition methodsapplied in channel estimation have become more popular. These methods estimate channel impulse response utilizing the orthogonal property that the range space of channel parameter matrix is orthogonal to the noise subspace. However, the subspace-based semi-blind channel estimation only could be applied to real transmitted signals, for example BPSK modulation signals. Therefore, the subspace decomposition method could not estimate the complex transmitted signals, such as QPSK or 16-QAM etc.
In the study, we applied a general STBC code for complex signals by using the modulating technique. The corresponding inverse Fourier transformation of the modulated STBC codes have backward conjugate and symmetry characteristics. Thus, we combine the general STBC code with MIMO-OFDM system and propose a forward-backward averaging estimation (FBE) method by utilizing the structural characteristics of the signals. The FBE method estimates channel impulse response by combining the forward and backward sample data. By the way, the FBE can improve the efficiency of channel estimation and reduce the bit error rate (BER).
Key words : Multiple Input Multiple Output (MIMO)、Orthogonal Frequency Division Modulation (OFDM)、Space Time Block Code(STBC)、Subspace Decomposition、Semi-blind Channel Estimation、Forward Backward Averaging Estimation(FBE)
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