在近年來的無線通訊發展中，多天線輸入輸出(MIMO)已成為不可或缺的關鍵技術，而其中接收端更是大量的使用到許多高效率的多天線訊號偵測演算法。多虧了通訊學者們的努力，多天線輸入輸出系統至今已發展出許多優秀的解調技巧，像是ZF解調、MMSE解調、球狀解碼等等都是多天線輸入輸出系統中重要的解調方法。多天線輸入輸出可以增加資料傳輸的吞吐量(throughput)或是獲得分集增益(diversity gain)等優點。所謂的增加資料吞吐量可以靠著多根傳送天線同時送出不同的資料來達成，而此種多天線系統又稱V-BLAST架構。本篇論文的重點將集中在V-BLAST架構上來進行分析研究。
本篇論文將著重於降低複雜度的球狀解碼，並介紹改良後的解調方法及動態軟值演算法。在球狀解碼的過程中，我們會看到樹是如何有效率地搜尋走訪，除此之外樹中每一層還可能會有不同的搜尋範圍，最後透過動態軟值演算法決定每一層的軟性值，我們將可在模擬結果發現此方法可在降低複雜度的情況下得到貼近ML解調的錯誤率

In recent years, for the development of wireless communications, Multi-Input and Multi-Output (MIMO) has become an indispensable key technology. In the receiver, one needs efficient algorithms for detection in the MIMO system. Thanks to the efforts of researchers, they have been many excellent detection techniques in MIMO system. For example, ZF detection, MMSE detection, sphere decoding, etc. are all of the important methods for detection in the MIMO system. MIMO can increase the throughput of data transmission or get diversity gain. Each antenna in the transmitter can send different data to increase data throughput. It is known as V-BLAST architecture. This thesis will focus on the V-BLAST architecture for analysis and research.
We focus on complexity reduction for the sphere decoding, and propose the new detection method and the dynamic soft algorithm. In the course of the sphere decoding, we study how to efficiently search the tree. In addition, each level of the tree may have different search range. Finally, we give a method to determine the soft of each level using the dynamic soft algorithm. The simulation results show that our method can reduce the complexity and achieve the performance close to ML detection.

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