最近這幾年，正值行動網路革新的年代，不僅僅用戶使用的數量每年的爆炸性增長且也要因應往後互聯網的時代，所以在頻譜資源有限下以往的多工技術包含分頻多工接取(FDMA)、分時多工接取(TDMA)與分碼多工接取(CDMA)皆已無法負荷這麼大量的通訊需求，而在最近幾年稀疏碼多工存取(SCMA)被認為是下一代5G通訊有潛力的關鍵多工技術，透過每個用戶獨自的碼本來區分，並且引入了稀疏展頻的概念，不僅僅提升了錯誤率的表現，並且也讓接收端能以訊息交換演算法(MPA)解調，複雜度大大的下降，以適應往後巨量多機器型態通訊(mMTC)的場景，而考慮到解調時間，5G中有無允諾上傳能夠節省避免訊號碰撞的排程時間，所以在無允諾的SCMA上傳系統中，若沒有活用戶檢測(AUD)的話反而會帶來很多不必要的運算，且在以往AUD中利用正交匹配追蹤(OMP)來檢測，受限於內積的運算，導致在高sparsity的時候無法檢測正確，且因為不知道當時上傳用戶數量，導致OMP終止條件易受環境影響，而在本文提出另一個觀點，使用MPA來檢測用戶，不僅僅避免了高sparsity在OMP易誤判的情況，也避免OMP中的變動運算時間對於硬體的設計困難，而最後結果也得知MPA在用戶偵測方面皆比OMP還要來的適合。
而在本文中也結合了光纖無線通訊系統(ROF)並且以實驗展示，展示了SCMA在接收光功率(ROP)的表現，以及用戶偵測的兩個算法的表現。

In recent years, the era of mobile network innovation is not only the explosive growth of the number of users every year, but also in response to the Internet era in the future. If using the previous multiplexing technology including frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA), it will not be able to handle such a large amount of communication demand. Therefore, sparse code multiple access (SCMA) is considered as a potential key multiplexing technology for next-generation 5G communications. It is distinguished by each user’s own codebook. And the concept of sparse spread spectrum is introduced, which not only improves the error rate performance, and also allows the demodulate with the message passing algorithm (MPA). So the complexity is greatly reduced, to adapt to the massive machine type communication (mMTC) scene in the future. Considering the demodulation time, there is Grant-Free uplink in 5G that can avoid the scheduling time of signal from different users. Therefore, in the Grant Free Uplink SCMA system, if there is no active user detection (AUD), it will bring a lot of unnecessary operation. In the past, AUD used Orthogonal Matching Pursuit (OMP) to detect, which was limited by the calculation of the inner product then caused difficult detection at high sparsity. And because the number of the active users is unknow, the OMP termination conditions are easily affected by the environment. In this article, I put forward another point. Using MPA to detect active user not only avoids the misjudgment of high sparsity in OMP, but also avoids the variable computing throughput in OMP. And in this article, the radio over fiber system (ROF) is demonstrated through experiments, showing the performance of the SCMA in the received optical power (ROP) and compare of the two algorithms for user detection.

摘要 i
ABSTRACT ii
致謝 iii
目錄 iv
圖目錄 vi
表目錄 ix
第 1 章 緒論 1
1.1 前言 1
1.2 研究目的與動機 4
1.3 論文架構 5
第 2 章 訊號介紹與實驗元件介紹 6
2.1 正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM) 6
2.2 非正交多工存取(Non-Orthogonal Multiple Access, NOMA) 11
2.2.1 Power-domain NOMA 12
2.3 稀疏碼多工存取(Sparse Code Multiple Access, SCMA) 14
2.3.1 SCMA 發射端 15
2.3.2 SCMA 接收端 16
2.3.3 訊息交換演算法(Message Passing Algorithm, MPA) 17
2.3.4 SCMA碼本設計 23
2.4 光載射頻(Radio over Fiber, ROF) 28
2.4.1 電-光調變器(Mach-Zehnder Modulator, MZM) 29
2.4.2 光學正交分頻多工系統的直接接收機制 31
第 3 章 SCMA無允諾上傳之用戶偵測 34
3.1 聯合訊息交換演算法(Joint Message Passing Algorithm, JMPA) 39
3.2 壓縮感測技術(Compressed Sensing, CS) 41
3.2.1 正交匹配追蹤(Orthogonal Match Pursuit, OMP) 43
3.3 MPA之用戶偵測 46
3.4 AUD-MPA 與 OMP 性能比較 51
第 4 章 實驗設置與結果 57
4.1 光纖無線通訊整合系統 57
4.2 實驗架構 59
4.3 實驗結果 60
4.3.1 SCMA 訊號解調 60
4.3.2 False Alarm & Miss Detection 62
4.3.3 用戶偵測 64
第 5 章 結論 67
參考文獻 68

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