馮世邁臺灣大學：電信工程學研究所黃燦煌Wong, Chan WongChan WongWong2007-11-272018-07-052007-11-272018-07-052004http://ntur.lib.ntu.edu.tw//handle/246246/58847在無線通訊系統中，由訊號的多重路徑傳播所造成的前後符號之間干擾(Inter-symbol Interference, ISI)一直被視為導致系統效能下降的重要因素。如果不把ISI的效應加以消除，它會使系統有很高的錯誤率。雖然決策回授等化器(Decision Feedback Equalizer, DFE)因其簡單的可實現性而被普遍採用，但它亦受到錯誤延遞(Error Propagation)的影響而使效能下降，不過，我們可以行用雙向等化法來加強決策回授等化器的效果。雙向決策回授等化器(Bidirectional Decision Feedback Equalizer, BiDFE)是由兩部份組成，除了包括傳統的正向(Forward) 決策回授等化器外，還包括一個在時間軸上反向 (Reverse)　的決策回授等化器。在本論文中，我們提出了兩個定義在格狀圖 (Trellis Diagram) 上對於兩個決策回授等化器出現結果不同時的衝突排解演算法。我們亦會說明在計算複雜度沒有增加很多的情況下，格狀型衝突排解 (Trellis Based Conflict Resolution, TBCR) 和片段最大概似序列估測器 (TBCR-piecewise Maximum Likelihood Sequence Estimation, TBCR-PWMLSE) 是更為強健的演算法。另外，對於決策回授等化器的係數計算方法，我們亦提出了兩個利用正向係數來推算反向係數的方法，這兩個方法約可把計算量降低至原來的一半。In wireless communication system, intersymbol interference (ISI) is long identified as a major impairment. ISI, if left uncompensated, causes high error rates. A suboptimal detector, namely the decision feedback equalizaer (DFE), is widely use in practice for ISI mitigation due to its simple implementation. DFE suffers from error propagation that causes performance degradation. Bidirectional equalization of the received signal can be used to enhance the performance of DFE. Bidirectional DFE consists of a traditional DFE in parallel with another DFE operating on the time-reversed sequence of the received signals. In this thesis, we propose two approaches, which are based on the observation in the trellis diagram, for resolving conflict events between the outputs of two DFEs. We also demonstrate that, with only little increase in computation complexity, the proposed trellis based conflict resolution (TBCR) and TBCR-piecewise maximum likelihood sequence estimator (TBCR-PWMLSE) are more robust than other algorithms. We also propose two methods for calculating the reverse DFE’s coefficients from that of forward DFE, thus reducing the complexity of computing the DFEs’ coefficients by half.Abstract ii Acknowledgement iii 1 Introduction 1 1.1 Background 2 1.2 Motivation 3 1.3 Organization 4 2 MIMO Communication System Model 7 2.1 Baseband Equivalent Signal Model 8 2.2 MIMO MMSE DFE 11 2.3 SISO MMSE DFE 17 3 Bi-directional Decision Feedback Equalizer (BiDFE) Algorithms 21 3.1 Maximum Likelihood Sequence Estimation (MLSE) 22 3.2 Time Reversal Diversity 23 3.3 Several BiDFE Algorithms 26 3.3.1 Selective Time-Reversal DFE 26 3.3.2 Linear Combining BiDFE (LC-BiDFE) 27 3.3.3 Bidirectional Arbitrated DFE (BAD) 28 3.3.4 BiDFE with Contradictory Block Arbitration (BiDFE-CBA)30 4 Proposed Trellis Based Bi-directional DFE Algorithm 33 4.1 Trellis Based Conflict Resolution (TBCR) 34 4.2 Piecewise Maximum Likelihood Sequence Estimation (PWMLSE) 37 4.3 Discussions 40 4.4 TBCR Extended to MIMO System 41 5 Coefficient Computation 49 5.1 Coefficient Relationship 50 5.2 Method 1 --- Modified Jacobi Algorithm 52 5.2.1 Jacobi Algorithm 53 5.2.2 Modified Jacobi Algorithm 55 5.3 Method 2 --- Modified Generalized Schur Algorithm 56 5.3.1 Schur Algorithm 57 5.3.2 Generalized Schur Algorithm 59 5.3.3 Modified Generalized Schur Algorithm 62 6 Simulation Results 67 7 Conclusions 77 Bibliography 81 Appendix A 85767357 bytesapplication/pdfen-US格狀型衝突排解雙向決策回授等化器Bidirectional DFETrellis BasedConflict Resolution[SDGs]SDG16thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/58847/1/ntu-93-R91942040-1.pdf