第四代行動通訊系統(又稱LTE: Long Term Evolution) 提供了高數據傳輸量，並且也是目前商業運轉的無線通信系統。其主要的技術為正交分頻多工(OFDM)、多輸入多輸出(MIMO) 以及調適性調變及編碼(AMC)。其中OFDM可降低使用頻率的干擾，MIMO 可接收較強的信號進而增加數據的傳輸量，而AMC可依信號的品質來進行調變及編碼。在台灣地區國家傳播委員會(NCC)釋出了700MHz, 900MHz, 1800Mz 及2600Mz等頻段後。得標營運商皆動用所有可用的資源進行LTE 網路的建設。目前在台灣皆達到八、九成的覆蓋率，並且現在正進行網路的優化工作。
由於目前的營運商也都有提供2G 及3G的網路服務，所以4G系統大多和2G及3G系統為共站的形式來服務用戶，另外也由於天線位置的空間受到限制，所以大多使用雙頻或3頻天線用相同的方位角及俯角來提供服務。但是不同的系統可提供的服務模式皆不相同，而4G系統主要是服務要有高傳輸量需求的用戶。所以在使用共同天線這樣的限制環境下，又要提供4G用戶較佳的服務品質，則是目前營運商目前正在思考的課題。
若要進行4G 天線調整時，其2G及 3G的信號皆會受到影響。對於4G系統來說有MIMO的功能則延伸其應用為束波成形(Beam Forming) 之技術，4G天線也是有兩個信號端(2 ports)，但這已經是具有MIMO 2 x2的功能。但目前為了要確保各基地台及網路基本的KPI(Key Performance Index) 都能維持著，所以目前皆設為初始值即相位設定為0. 因此本研究即在特定地點上以MATLAB進行模擬以找出最佳的手機端相位設定值，進而改善弱信號區用戶端之傳輸速率。

The fourth Generation Mobile Communication System (LTE : Long Term Evolution) provides high data throughput, and it is also the current commercial operation mobile system. The major techniques include OFDM, MIMO and AMC. The OFDM (Orthogonal Frequency Division Multiple) can reduce interference among frequencies. MIMO (Multi Input Multi Output) can get stronger signal and then increase data throughput. The AMC (Adaptive Modulation and Coding) will rely on signal quality to assign modulation and coding. NCC (National Communications Commission) had released 700MHz, 900MHz, 1800MHz and 2600MHz frequency bands for auction in Taiwan. The awarded Operators used all possible resource to build LTE network. The current network coverage had reached 80%~90% in Taiwan. And now, they are working for Network optimization.
Due to the fact that those awarded operators also provide 2G and 3G network service, the 4G system almost co-builds with 2G and 3G site to provide service. And also since the space of antenna location is limited, they often use dual-band or triple-band antenna and assign the same Azimuth and down-tile to provide service. But different systems provide different services. For 4G system, the major service is to provide high data throughput for subscribers. It will be the current major study topic for all operators, that is to use common antenna and also to provide the best service quality for subscribers.
If 4G antenna needs to be adjusted, the 2G and 3G signal will be affected. But for 4G system, the MIMO function can be extended to the application of Beam Forming. 4G antenna has 2 ports with MIMO 2 x 2 function, but operators need to maintain basic KPI (Key Performance Index) for eNode B and Network. The parameter of phase adjustment is default value = 0. This study is for particular cell to use MATLAB simulation to find out the best phase for mobile setup, and then to improve data throughput for the user of weak signal cell.

第一章 緒論 1
1.1 第四代行動通訊時代的來臨 1
1.2 研究動機與目的 3
1.3 章節架構介紹 4
第二章 研究構想 5
2.1 第四代行動電話基礎技術 5
2.1.1 正交分頻多工(OFDM) 6
2.1.2 多輸入多輸出(MIMO) 9
2.1.2.1 多樣性(Diversity) 9
2.1.2.2 多輸入多輸出(MIMO) 9
2.1.3 調適性調變及編碼(AMC) 11
2.1.3.1 正交相位調變(QPSK) 11
2.1.3.2 16位正交振幅調變(16QAM) 13
2.1.3.3 64位正交振幅調變(64QAM) 16
2.1.3.4 頻道品質指標(CQI)之決定 17
第三章 束波成形(Beam Forming)之介紹 19
3.1 束波成形(Beam Forming說明 19
3.2 束波成形(Beam Forming) 之設計 20
第四章 模擬與實現 22
4.1 程式說明及假設 22
4.1.1 頻道矩陣(Channel Matrix : H Matrix) 22
4.1.2 手機APP之應用 25
4.1.3 特徵值λ1 及λ2之求解 27
4.1.3.1 公式說明 27
4.1.3.2 牛頓-拉夫生迭代法及亞可比矩陣 29
4.2 模擬結果 31
4.2.1 實際地點資料輸入及模擬結果 33
第五章 未來發展及結論 38

[1] NCC網站 “http://mbb.ncc.gov.tw/index.html” 所公佈之各家得標結果。
[2] 遠傳電信用於頻譜得標前之試驗性頻率調整(Pilot Re-farming) 及得標後1800MHz 2G/4G頻譜之比較。
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