新一代的通訊系統採用正交分頻多工(Orthogonal frequency-division multiplexing)作為傳輸技術，除了傳輸技術的改變，支援高速移動中的使用者，確保移動時不會有斷話的情形發生，也是新一代通訊系統重要的課題之ㄧ。在移動通道中，都卜勒擴散(Doppler spread)會破壞子載波之間的正交性，將導致子載波間互相干擾(Inter Carrier Interference)，嚴重影響系統效能。

使用者遠離時，因為與基地台的距離發生變化，導致接收訊號越來越差，此時想要維持良好的服務品質(Quality of Services)，基地台可以利用適應性調變與編碼(Adaptive Modulation and Coding)技術，適時的改變調變與編碼方式，以維持服務品質。

本論文主要在討論調變(Modulation)、編碼(Coding)以及多天線技術（Multiple-Input Multiple-Output），在高速環境下，對於系統效能的影響，並且提供在不同訊雜比(Signal Noise Ratio)、不同速度下，使用何種調變與編碼的建議表。

Most generation wireless communication systems are based on Orthogonal frequency-division multiplexing transmission technology. Besides the transmission technology changes, to avoid break down when users communicate by phone and support users in high speed environment are important. In a moving channel, doppler spread will cause inter carrier interference. It will affect performance seriously.

When the users far away form base station, the received signal will become weak. If we want to keep good quality of services, we can use adaptive modulation and coding technology to change the combination of modulation and coding.

In this paper, we will discuss the performance in different modulation, coding, and MIMO system in high speed environment and give an adaptive modulation and coding table in different speed and signal noise ratio.

目錄
第一章 緒論	1
1.1 研究動機與目的	1
1.2 章節介紹	2
第二章 通道模型	3
2.1 都卜勒效應	3
2.2 快速衰落模型	4
第三章 無線通訊系統架構	8
3.1 MIMO系統	8
3.2 系統模擬架構	11
3.3 不同速度下之效能模擬	13
3.4 不同速度下之BER極限值	19
第四章 高速度下之適應性編碼與調變選擇	21
4.1 調變與碼率之增益比較	21
4.2 不同速度下之適應性調變與編碼建議表	28
第五章 基地台距離模擬	29
5.1 距離與SNR的關係	29
5.2 通道損失模型	31
5.3 不同調變編碼之基地台距離表	34
5.4 不同速度對於系統Throughput之影響	36
第六章 結論與未來展望	37
參考文獻	39
圖目錄
圖2.1：都卜勒效應對於子載波的影響	3
圖2.2：具有直射波(Line of sight, LOS)	5
圖2.3：不具有直射波(Line of sight, NLOS)	5
圖2.4：Rayleigh Fading之訊號強度示意圖	6
圖2.5：傑克斯模型	7
圖3.1：Alamouti二傳二收系統架構圖	8
圖3.2(a)：傳送端系統架構	11
圖3.2(b)：接收端系統架構	11
圖3.3：QPSK(2/3)模擬結果	13
圖3.4：QPSK(1/2)模擬結果	14
圖3.5：QPSK(1/3)模擬結果	14
圖3.6：16-QAM(2/3)模擬結果	15
圖3.7：16-QAM (1/2)模擬結果	15
圖3.8：16-QAM (1/3)模擬結果	16
圖3.9：64-QAM (2/3)模擬結果	16
圖3.10：64-QAM (1/2)模擬結果	17
圖3.11：64-QAM (1/3)模擬結果	17
圖4.1：改變碼率的效能比較	21
圖4.2：改變調變的效能比較	22
圖4.3：時速250 km/hr下QPSK(2/3)和16-QAM(1/3)效能比較	23
圖4.4：時速350 km/hr下QPSK(2/3)和16-QAM(1/3)效能比較	24
圖4.5：時速500 km/hr下QPSK(2/3)和16-QAM(1/3)效能比較	24
圖4.6：時速250 km/hr下16-QAM(1/2)和64-QAM(1/3)效能比較	25
圖4.7：時速350 km/hr下16-QAM(1/2)和64-QAM(1/3)效能比較	26
圖4.8：時速500 km/hr下16-QAM(1/2)和64-QAM(1/3)效能比較	26
圖5.1：模擬情境示意圖	29
圖5.2：雜訊比與距離關係	30
圖5.3：路徑損失模型	33
圖5.4：距離與Throughput之變化	34
圖5.5：三種速度下兩種MIMO系統之Throughput比較	36
圖6.1：考慮速度的適應性調變與編碼表	38
圖6.2(a)：傳送端系統架構	38
圖6.2(b)：接收端系統架構	38
表目錄
表3.1：二傳二收傳送符碼表	9
表3.2：四傳四收實數傳送符碼表	10
表3.3：四傳四收複數傳送符碼表	11
表3.4：系統模擬參數	12
表3.5：時速為250 km/hr的BER極限值	19
表3.6：時速為350 km/hr的BER極限值	20
表3.7：時速為500 km/hr的BER極限值	20
表4.1：調變與碼率的選擇	27
表5.1：基地台距離表	35

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