長期演進技術(Long term evolution, LTE)已成為第四代行動通訊技術(the fourth generation of mobile phone mobile communication technology standards, 4G) 的標準, 在下行鏈路技術的選擇上, 採用正交分頻多工(Orthogonal frequency division mul-tiplexing, OFDM) 和多輸入多輸出(Multi-input Multi-output, MIMO) 技術, 可因應近年行動通訊的使用人數與數據傳輸量的爆炸性增長, 所衍生出龐大傳輸速率的需求。因此, 本論文的系統環境將以LTE 為主軸進行討論。
為輔助通道估測, 傳送端會發送一已知訊號, 稱為導頻訊號, 藉由導頻訊號可獲得通道的資訊, 對受到環境影響而失真的訊號進行復原。本論文旨在說明LTE 下行鏈路的通道估測方法: 具體將以最小平方(LS) 法以及最小均方誤差(MMSE) 法為基礎, 並以軟體進行均方誤差(MSE) 的性能比較。此外, 藉由估測通道作為基礎, 透過運算之後可以精準的估測該環境的訊雜比, 最後將本論文的研究成果以軟體無線電平台實現。

Long term evolution (LTE) has become the fourth generation of mobile phone mobile communication technology standards (4G). Orthogonal frequency division
multiplexing and MIMO technology has been used in the downlink channel because this technique can serve the huge demand due to the explosive growth of the large number of data sent by users. The system studied in this thesis is based on LTE.
To perform the channel estimation, the transmitters send a pre-defined signal called pilot signal and then the channel can be estimated based on the pilot signal. Based on the estimated channel, the data symbols distorted by the propagation channel can be recovered by the channel information. This thesis aims to examine
the LTE downlink channel estimation methods including the least squares and the minimum mean square error approaches, and then we compare the performance by mean square error. In addition, signal-to-noise ratio of the system can be estimated precisely based on the estimated channel information. The results of this thesis are implemented in the LTE multi-antenna measurement software radio platform.

審定書i
誌謝ii
摘要iii
Abstract iv
目錄v
圖次viii
表次x
1 緒論1
1.1 引言以及動機. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 OFDM 原理. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 通道模型. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 MIMO 技術. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 LTE 系統. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4.1 資源網格. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.4.2 參考訊號. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.5 目標和論文安排. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2 通道估測演算法簡介11
2.1 線性內插法. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2 最小平方法. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.3 最小均方誤差法. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.1 相關性矩陣. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.4 時域內插. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.5 低複雜度最小均方誤差法. . . . . . . . . . . . . . . . . . . . . . . . . . 19
3 基於LTE 下行鏈路之通道估測效能分析22
3.1 窗口大小. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2 強健性. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.3 時域內插. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.4 低複雜度最小均方誤差法. . . . . . . . . . . . . . . . . . . . . . . . . . 27
4 訊號雜訊比估測28
4.1 訊雜比計算. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1.1 SISO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1.2 SIMO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.1.3 MIMO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2 訊雜比估測. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
4.3 OFDM環境下訊號雜訊比估測之效能評估. . . . . . . . . . . . . . . . . 32
4.3.1 SISO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.3.2 MIMO 2 × 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.3.3 MIMO 4 × 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.3.4 LTE標準. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.4 通道容量計算. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
5 LTE MIMO 智慧終端驗證平台41
5.1 平台介紹. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.2 OTA測試. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.3 LTE 8 × 4 MIMO 智慧終端驗證平台. . . . . . . . . . . . . . . . . . . 48
6 結論54
參考文獻55

[1] Cisco, “Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, 2015 2020,” Cisco white paper, 2016.
[2] Ericsson, “Ericsson Mobility Report,” November 2015.
[3] GSA, “Evolution to LTE Report,” Global mobile Suppliers Association, October 2015.
[4] 3GPP TS 36.211, http://www.3gpp.org/dynareport/36211.htm
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[7] M. Noh, Y. Lee and H. Park, “Low complexity LMMSE channel estimation for OFDM,” IEE Proceedings on Communications, vol. 153, no. 5, pp. 645-650, October 2006.
[8] L. Hanzo, M. Munster, B. Choi, and T. Keller, OFDM and MC-CDMA for Broadband MultiUser Communications, WLANs and Broadcasting. John Wiley - IEEE Press, 2003.