多進制差分調變無線通訊系統之多重符號偵測研究

Abstract

摘 要 高頻譜效率之多進制差分調變已在文獻中被廣泛的探討。本論文中介紹了幾種已被研究及發表的多重符號偵測使用於多進制差分調變，並且研究多重符號偵測使用於16DAPSK系統傳輸在各種通訊環境中。這種方法在AWGN環境裡有高效率的表現。為了在衰落通道下使用多重符號偵測，單步預測被引用於解調器。吾人將原本用於DPSK的等化器應用到16DAPSK並且加上多重符號偵測技術。此外，吾人提出修正的16DAPSK等化器中適應性演算法的誤差訊號。此方法使用LMS演算法在高訊號雜訊比下會提供較好的效能。吾人亦提出改良的16DAPSK非同調判別式迴授等化器，其架構在許多情況下比線性等化器有較好的效能。以上各種架構的效能比較均以電腦模擬所完成。

ABSTRACT The spectral efficient high-level modulation scheme has been widely investigated. In this thesis, several multiple symbol detection (MSD) schemes used with high level modulation are presented. The use of multiple symbol detection to improve the performance of 16DAPSK modulation/demodulation in various communication channels is studied. MSD shows a large performance improvement over additive white Gaussian noise (AWGN) channel. To use MSD in Rayleigh fading channel, one-step prediction is introduced in the demodulation scheme. Equalizer scheme for differential coherent detection used before in DPSK is implemented in 16DAPSK system along with multiple symbol detection. Furthermore, modified error signal for equalizer in 16DAPSK with different adaptive algorithm is proposed. With this modified error signal the equalizer will work better in high SNR using LMS algorithm. Modified non-coherent decision feedback equalizer (DFE) scheme for 16DAPSK is also proposed. This new scheme shows a superior performance in many cases compared to linear equalizer. All the performance comparisons of each scheme stated above are achieved using computer simulation. Multi-Symbol Detection in Multi-level DAPSK Modulation/Demodulation Scheme for Wireless Communication System i Multi-Symbol Detection in Multi-level DAPSK Modulation/Demodulation Scheme for Wireless Communication System ii 摘 要 iii ABSTRACT iv Acknowledgement v Content vi List of Figures viii List of Tables xii Chapter 1 1 Introduction 1 1.1 Thesis background 1 1.2 Thesis outline 2 Chapter 2 3 System Structure and Transmission Model 3 2.1 Modem System of 8DPSK, 16DPSK and 16DAPSK 3 2.2 MDPSK System 4 2.3 16DAPSK System Model and Signal 6 2.4 Channel model 12 Chapter 3 14 Multi Symbol Detection 14 3.1 Multi Symbol Detection Criterion in MDPSK 15 3.2 Multi Symbol Detection Criterion in 16DAPSK 18 Chapter 4 28 Application of MSD in Rayleigh Fading Channel 28 4.1 Source of Irreducible BER in DPSK Modem 28 4.2 DFDD for 16DAPSK based on Linear Prediction 30 Chapter 5 45 Joint Equalization and Differential Detection Scheme using MSD 45 5.1 Adaptive equalizer for differentially coherent detection 46 5.2 Non-coherent adaptive linear MMSE equalization for 16DAPSK signals 48 5.3 Modified adaptive linear MMSE equalization for 16DAPSK signals 50 Chapter 6 67 Conclusion 67 Bibliography 69