近年來，由於行動裝置普及率的指數成長，第四代行動通訊(4G)的正交分頻多工技術(Orthogonal Frequency Division Multiplexing, OFDM)逐漸跟不上使用者的裝置數量的需求，在有限的資源頻譜下可以容納的用戶有限。在近幾年的第五代行動通訊(5G)討論中，稀疏碼多工存取(Sparse Code Multiple Access)被認為是NOMA(Non-orthogonal Multiple Access)技術的選項之一，透過使用多維碼本，並且搭配稀疏展頻的配置，使得更多的用戶能夠在同一個子載波下進行傳輸，增加可使用的用戶數量，並且透過使用訊息交換演算法來進行解調，搭配稀疏展頻的配置，使得錯誤率的表現與最大概似機率(Maximum Likelihood)接近，並且有著更低的複雜度。
在SCMA無允諾上傳的場景下，用戶端透過傳送特徵來告知基地台用戶活躍的情形，而在以往的用戶偵測中主要利用正交匹配追蹤的方式來進行用戶偵測，然而此種方式在用戶稀疏性較高時會有較差的表現，並且在用戶偵測的情況下，由於無法得知用戶的稀疏性，因此必須使用雜訊來做判斷，在低SNR時的表現較差。在本文中透過利用單一用戶使用多重碼本的方式並且利用訊息交換演算法來當作用戶偵測的方法，此種方式進行用戶偵測不僅是不需要得知用戶的稀疏度，並且也透過多重碼本的設計得到碼多樣性。最後也結合了毫米波無線通訊系統並進行實驗展示，驗證多重碼本SCMA系統在毫米波無線通訊下的表現，以及多重碼本MPA與OMP的用戶偵測表現。

In recent years, due to the exponential growth in the number of mobile devices, the Orthogonal Frequency Division Multiplexing(OFDM) technology of the fourth generation mobile communication is gradually unable to keep up with the demand of the number of devices, and the number of simultaneously accessible user is proportional to the number of available resources. In the fifth generation mobile communication(5G), Sparse Code Multiple Access(SCMA) technology is a promising candidate for Non orthogonal multiple access(NOMA). By using multi-dimensional codebooks and sparse spreading spectrum, different users are overlapped non-orthogonally in the same subcarrier for increasing simultaneously accessible users. In decoder, SCMA is implemented with message passing algorithm(MPA), which can obtain near optimal bit error rate and much lower complexity compare with maximum likelihood(ML).
In SCMA grant-free access, users transmit the transmission signature to base stations for active user detection. In conventional active user detection using orthogonal matching pursuit(OMP) to detect active list, however, high sparsity reduce the OMP performance, and the unknown sparsity in active user detection cause the OMP need to use noise for termination condition, which conduct the bad performance in low SNR.
In this article, we consider a new approach that using message passing algorithm with multi-codebook sets for active user detection. It is shown that not only obtain code diversity in multi-codebook, but also avoid the misjudgment of high sparsity in OMP .
Finally, we demonstrate the Millimeter wave wireless system through the experiments, showing the performance of multi-codebook SCMA in the real-time wireless system and compare multi-codebook MPA with OMP in active user detection.

摘要 i
ABSTRACT ii
致謝 iii
目錄 iv
圖目錄 v
表目錄 viii
第 1 章 緒論 1
1.1 前言 1
1.2 研究目的與動機 5
1.3 論文架構 6
第 2 章 系統架構介紹 7
2.1 正交分頻多工 7
2.2 非正交多工存取 11
2.2.1 Power-domain NOMA 13
2.3 稀疏碼多工存取 15
2.3.1 SCMA上行鏈路架構 17
2.3.2 MPA接收機 19
2.3.3 SCMA 多重碼本設計 23
2.3.4 MC-SCMA與SC-SCMA性能比較 29
第 3 章 多重碼本SCMA無允諾上傳用戶偵測 31
3.1 無允諾上傳用戶偵測 31
3.2 正交匹配追蹤 37
3.3 多重碼本MPA用戶偵測 39
3.3.1 SC-SCMA用戶偵測 40
3.3.2 MC-SCMA用戶偵測 40
3.4 AUD不同方法性能比較 44
第 4 章 實驗設置與結果 47
4.1 實驗架構 47
4.2 實驗結果 49
4.2.1 多重碼本SCMA實驗分析 49
4.2.2 Miss Detection與False Alarm實驗分析 53
4.2.3 用戶偵測實驗分析 55
第 5 章 結論 59
參考文獻 60

[1] M. Shafi et al., "5G: A Tutorial Overview of Standards, Trials, Challenges, Deployment, and Practice," IEEE Journal on Selected Areas in Communications, vol. 35, no. 6, pp. 1201-1221, June 2017.
[2] N. H. Mahmood, R. Abreu, R. Böhnke, M. Schubert, G. Berardinelli, T. H. Jacobsen
"Uplink Grant-Free Access Solutions for URLLC services in 5G New Radio," 2019 16th International Symposium on Wireless Communication Systems (ISWCS), pp. 607-612.
[3] L. Dai, B. Wang, Y. Yuan, S. Han, I. Chih-Lin, and Z. Wang, "Nonorthogonal multiple access for 5G: Solutions, challenges, opportunities, and future research trends, " IEEE Communication. Mag., vol. 53, no. 9, pp. 74–81, Sep. 2015.
[4] R. Chang and R. Gibby, "A Theoretical Study of Performance of an Orthogonal Multiplexing Data Transmission Scheme," IEEE Transactions on Communication Technology, vol. 16, no. 4, pp. 529-540, August 1968.
[5] L. Dai, B. Wang, Z. Ding, Z. Wang, S. Chen, and L. Hanzo, "A survey of non-orthogonal multiple access for 5G, " IEEE Communications. Surveys & Tutorials., vol. 20, no. 3, pp. 2294–2323, 3rd Quart., 2018.
[6] H. Nikopour and H. Baligh, "Sparse code multiple access, "in Proc. IEEE 24th Annual. Int. Symposium. Pers. Indoor Mobile Radio Communications(PIMRC)., London, U.K., 2013, pp. 332–336.
[7] M. Vameghestahbanati, I. D. Marsland, R. H. Gohary, and H. Yanikomeroglu, "Multidimensional constellations for uplink SCMA systems—A comparative study," IEEE Commun. Surveys Tuts., vol. 21, no. 3, pp. 2169–2194, 3rd Quart., 2019.
[8] M. Taherzadeh, H. Nikopour, A. Bayesteh, and H. Baligh, “SCMA
codebook design,” in Proc. IEEE 80th Vehicular Technology Conference
(VTC Fall), 2014, pp. 1-5, Sept. 2014.
[9] Y.-M. Chen and J.-W. Chen, “On the design of near-optimal sparse code multiple access codebooks,” IEEE Trans. Commun., vol. 68, no. 5, pp. 2950–2962, May 2020.
[10] A. T. Abebe and C. G. Kang, “Grant-free uplink transmission with multi-codebook-based sparse code multiple access (MC-SCMA),” IEEE Access, vol. 7, pp. 169853–169864, 2019
[11] M. B. Shahab, R. Abbas, M. Shirvanimoghaddam, and S. J. Johnson, “Grant-free non-orthogonal multiple access for IoT: A survey,” IEEE Commun. Surveys Tuts., vol. 22, no. 3, pp. 1805–1838, 3st Quart., 2020
[12] E. J. Candès and M. B. Wakin, ‘‘An introduction to compressive sampling,’’ IEEE Signal Process. Mag., vol. 25, no. 2, pp. 21–30, Mar. 2008.
[13] Tropp J., Gillbert A.. Signal recovery from random measurement via orthogonal
matching pursuit[J]. IEEE Transactions on Information Theory, 2007, 53(12): 4655-4666