廣義空間調變(Generalized Spatial Modulation)，是一種在多輸入多輸出(Multi-Input Multi-Output)系統下的調變方式，是近年比較熱門拿來運用在多天線輸出(MIMO)架構上的技術，此作法在每一個時間點，不啟動全部的天線在傳輸資料，而是只有特定一組的天線組合會啟動來發射訊號，由此一來，在接收端就不需要太多的射頻 (Radio Frequency)電路，而相比於多天線輸入多天線輸出系統，它也能解決通道間干擾(Inter-Channel Interference)的問題。
在一般的通訊系統中常見的解調方法有許多種，像是ML(maximum likelihood)或MMSE(minimum mean squared error)等等，而ML解調方法雖然是所有解調方法中錯誤率最好的，但是它的複雜度也是所有方法中最高的。而球體解碼也是一種應用於MIMO中的解調方法，透過持續的降低搜索半徑，去大大的減少所要搜尋的點，同時錯誤率還能跟ML解一樣好，是一種非常有效率的解調方式，然而它的複雜度還是很高。
在本篇論文中，我會針對在GSM架構下，提出一種較低複雜度版本的球狀解碼，排序球狀解碼(S-SD)，在降低複雜度的同時，也不會犧牲掉太多的錯誤率，其原理為先透過排序天線演算法，求出當次傳輸每一組天線組合的機率大小，再去做排序，再根據排序的結果去修剪樹的大小，同時也參照可靠值去決定要搜尋幾組天線組合。

Generalized Spatial Modulation (GSM) is a modulation method under the Multi-Input Multi-Output (MIMO) system. It is a popular technology used in the MIMO architecture ,in recent years. The principle of this method is that at each time, not all antennas are activated to transmit data, but only a specific set of antenna combinations will be activated to transmit signals. As a result, there is no need for too many radio frequency circuits at the receiver. Compared with the MIMO system, we also have to solve the interference among antennas.
There are many detection methods in the receiver, such as the maximum likelihood (ML)detection and minimum mean squared error (MMSE) detection, etc. Although the ML detection method has the optimal performance, its complexity is also quite high.The sphere decoding (SD) is an efficient method for the MIMO system,and it can efficiently attain the ML detection, although its complexity is increased with decreasing signal-to-noise ration (SNR).
In this thesis, we propose a lower complexity version of the SD algorithm under the GSM architecture. The proposed algorithm is expected to reduce the complexity and maintain efficient performance.

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