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研究生： 陳宏都
Hong-Du Chen
論文名稱： 適用於多重輸入多重輸出系統之時空格子碼解碼器
Space-Time Trellis Codes Decoder for Multiple-Input Multiple-Output Systems
指導教授： 黃元豪
Yuan-Hao Huang
口試委員:
學位類別： 碩士
Master
系所名稱： 電機資訊學院 - 通訊工程研究所
Communications Engineering
論文出版年： 2008
畢業學年度： 96
語文別： 中文
論文頁數： 74
中文關鍵詞： 時空 、格子碼 、解碼器 、多重輸入多重輸出
外文關鍵詞： space-time, Trellis Codes, Decoder, Multiple-Input Multiple-Output
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    • 在本篇論文中，我們所要介紹的是使用在無線多重輸入多重輸出(Multi-Input and Multi-Output)通訊上的時空格子編(Space-Time Trellis Codes)碼解碼器之設計與實現。儘管作為時空格子編解碼原理的維特比演算法(Viterbi algorithm)是一項相當基本的技術原理，但是依照我們所提出的設計架構為目標，是朝著能夠適用於無線多重輸入多重輸出通道中所需處理的繁重運算操作，並且能夠改善維特比演算法中的所帶來的運算複雜度。除此之外，維特比演算法的運算複雜度也會隨著天線使用數增加(無論是傳送天線的數目或是接收天線的數目)與調變系統的階數增高有著明顯的成長。我們為了減少運算複雜度所造成的硬體上的負擔。於是，我們便提出了一種以幾何觀點的角度去計算分支路徑值(Branch Metric)的新系統。另外，在更多的傳送與接收天線使用量之情形與採用更高階的調變系統下，新系統能夠有著越是顯著減少運算複雜度的效果。除此之外，使用我們所提出的4值輸入之大小比較器去改善處理效率也在論文中被提及，假設在訊雜比(SNR)大於6dB的白色高斯雜訊(AWGN)通道中，我們可以明顯觀察到其效果就相當接近於一般傳統使用的2值輸入比較器。因此，我們可以說，在我們所提出的系統是為了期望實現在下一代通訊系統上，能夠使用較高階的調變系統，以及使用更大量天線與高複雜度之時空碼的可能性。

    In this thesis, the design and implementation of STTC decoder architecture for wireless multiple-input multi-output (MIMO) communications are introduced.
    Viterbi algorithm is the basic technique for space-time trellis codes (STTC) decoding but the proposed architecture aims to perform massive operations over wireless MIMO channels and improve computational complexity of Viterbi algorithm. Moreover, the computational complexity also increases significantly if the number of antennas and the order of modulation increase. To reduce the computational burden, we propose a new method to compute the branch metrics in the geometric view. Furthermore, more complexity reduction can be achieved when more antennas and higher order of modulation are applied. In addition, 4-input magnitude comparator is implement to improve throughput in this thesis.
    If the SNR of AWGN channel is bigger than 6 dB, we can observe that the performance of 4-input magnitude comparator is close to the performance of tradition 2-input magnitude comparator. Therefore, the proposed method will make the implementation of high-order modulation, large antenna number, and high complexity space-time code possible for next generation communication systems.

    1 Introduction 1 2 Space-Time Codes 5 2.1 Fading Channel Model . . . . . . . . . . . . . . . . 6 2.2 Diversity . . . . . . . . . . . . . . . . . 7 2.2.1 Diversity Techniques . . . . . . . . . . . . . . . . 7 2.2.2 Diversity Combining Methods . . . . .. . . . . . . . 8 2.2.3 Transmit Diversity . . . . . . . . . . . 10 2.3 Space-Time Trellis Codes . . . . . . . . . . . 10 2.3.1 Generator Description . . . . . . . . . . . 11 2.3.2 Generator Polynomial Description . . . . . 13 2.3.3 Example . . . . . . . . . . . . . . . . . . 14 2.4 Performance of STTC Codes . . . . . . . . . . . . . 15 3 STTC Decoding Algorithm 31 3.1 Viterbi Algorithm for STTC . . . . . . . . . . . 31 3.1.1 Branch Metric Calculation . . . . . . . . . 33 3.1.2 Add-Compare-Select . . . . . . . . . 33 3.1.3 Update Paths and Metrics . . . . . . . . . . . 34 3.2 Proposed Methods . . . . . . . . . . . 34 3.2.1 Slow Method . . . . . . . . . . . . . . 35 3.2.2 Fast Method . . . . . . . . . . . . . . . 40 3.2.3 Multiple-Input Add-Compare-Select . . . . . . . 41 4 Architecture 43 4.1 Proposed Branch Metric Generator . . . . . . . . . 44 4.2 Proposed Add-Compare-Select . . . . . . . . . 49 4.3 Proposed Update Paths and Metrics . . . . . . . 54 5 Chip Implementation 61 5.1 RTL Simulation . . . . . . . . . . . . . . . . . 61 5.2 Layout . . . . . . . . . . . . . 66 6 Conclusion 71

    [1] B. Vucetic and J. Yuan. Space-Time Coding. John Wiley & Sons, LTD, England,2003.

    [2] N. Seshadri V. Tarokh and A. R. Calderbank. "Space-Time Codes for High Data Rate Wireless Communication: Performance Criterion and Code Construction".IEEE Trans.Inform. theory, 44(2):744-765, Mar. 1998.

    [3] A. J. Viterbi. "Error Bounds for Convolutional Codes and an Asymptotically Optimum Decoding Algorithm". IEEE Trans. Inform. theory, IT-13(2):260{269, Apr.1967.

    [4] A. P. Paulraj, etc. "An overview of MIMO communications - a key to gigabit wirelss". IEEE Proceeding, Vol.92(2):198-218, Feb. 2004.

    [5] Kai-Ting Shr and Yuan-Hao Huang. "Low-Complexity Branch Metric Calculation for Space-Time Trellis Decoding". Accepted by IEEE APCC, 2007.

    [6] R. J. McEliece. The Theory of Information and Coding, 2nd. Cambridge, UK:Cambridge University Press, 2002.

    [7] Hamid Jafarkhani. Space-Time Coding: Theory and Practice. Cambridge, 2005.

    [8] Stephan Baro, Gerhard Bauch, and Axel Hansmann. "Improved Codes for Space-Time Trellis-Coded Modulation". IEEE Communications Letters, Vol. 4, No. 1, January 2000.

    [9] Z. Chen,B. Vucetic, J. Yuan and K. Lo. "Space-time trellis Coded modulation with three and four transmit antennas on slow fading channels". IEEE Communications
    Letters, Vol. 6, No. 2, pp. 67-69, Feb 2002.

    [10] A. R. Hammons and H. E. Gammal. "On the theory of space-time codes for PSK modulation". IEEE Trans. on. Inform. Theory, Vol. 46, No. 2, March 2000, pp.524-542.

    [11] A. Naguib, V. Tarokh, N. Seshadri and A. Calderbank. "A space-time coding modem for high-data-rate wireless communications". IEEE Journal Select. Areas
    Commun., Vol. 16, pp. 1459-1478, Oct. 1998.

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