隨機線性分散時空碼的效能分析

Abstract

隨著行動通訊的普及與影像資料的傳送需求，傳送速率被要求增加，多輸入輸出天線系統(Multiple-input Multiple-output,MIMO)也因應而生。系統的傳輸效能因此大幅增加，而且頻譜效益(spectral efficiency)也有顯著的提升。在傳輸技術上，編碼與解碼的方式也有許多的討論。本論文針對時空區塊碼中的黃金碼與完美時空區塊碼的效能與高斯隨機線性分散碼進行比較。在接收端的解碼方式使用的是樹狀搜尋球形解碼演算法。 黃金碼在低訊雜比時的表現與高斯隨機線性分散碼幾乎相近，隨著訊雜比的提升，黃金碼的字碼錯誤率就比高斯隨機線性分散碼低，兩者之間的差異也隨著訊雜比的增加而增加，由於黃金碼是經由最佳化的結果，其編碼增益已經達到最大，因此其字碼錯誤率效能比高斯隨機線性分散碼好。4X4的完美時空區塊碼並沒有達到最佳化的效果，因此其在低訊雜比時，其字碼錯誤率比高斯隨機線性分散碼高，隨著訊雜比的增加，兩者字碼錯誤率交會於 之間，然後隨著訊雜比的增加，4X4完美時空區塊碼其字碼錯誤率的表現就遠比高斯隨機線性分散碼更好。

The transmission rate is increasing due to the video data information are transmitted through the mobile communication system. In order to satisfy the requirement of high transmission rate, the Multiple-input Multiple-ouput (MIMO) were invented. The spectral efficiency had great improvement in MIMO system. There are lots of studies on how to improve the performance of MIMO system. The space time block code is one of the studies. The performance of the golden code and perfect space time code versus Gaussian Random dispersion code are discussed in this thesis. The sphere decoder which is tree search algorithm is used to decode the code. The golden code and the Gaussian random code had almost the same performance during low SNR. As the SNR increasing, the code error rate of the golden code had better performance than the Gaussian code. This is because the golden code is optimal. Because the 4X4 perfect space-time block code was not optimal, the Gaussian random linear dispersion code had better performance than the perfect space-time block code in low SNR. There was an intersection between the codeword error rate from to . As the SNR increasing, the code error rate of the perfect space-time block code was much lower than the Gaussian random code.