具混合式自動重傳機制和動態調變編碼之無線合作通訊系統之設計與分析

Abstract

在現今的高速無線通訊系統之下，我們需要更穩定可靠的傳輸技術，為了克服通道的衰減與變化，通常我們會使用一些分集技術。利用多輸入多輸出的技術來得到空間上的分集增益已是一項廣為人知的解決方法，然而，因為硬體上的限制，我們很難在行動裝置上面實作多根天線。很幸運地，我們可以利用合作傳輸的方法來產生虛擬的多輸入多輸出系統進而得到空間上的分集增益。除此之外，為了得到額外的分集增益，我們使用混合式自動重傳技術藉由不同時間點的重傳來得到時間上的分集增益。再者，為了使系統的吞吐量最大化，我們使用動態調變編碼技術來適應通道的衰減與變化。在這篇論文裡，我們設計了一個具有混合式自動重傳機制與動態調變編碼的合作通訊系統，藉此結合上述的各項好處進而達成穩定可靠的高速無線傳輸。為了得到更實際的結果，我們在高速下行分組接入系統的環境下測試我們的設計。

Reliable transmission is necessary in recent high-speed wireless communication systems. To overcome the fading channel, we may employ some diversity techniques. The use of multiple-input multiple-output (MIMO) technique is a well-known solution because it has an advantage in space diversity. However, due to hardware limitations, multiple antennas are hard to implemented in mobile devices. Fortunately, the use of cooperative transmission can generate a virtual MIMO system and achieve the space diversity. Besides, in order to obtain another diversity gain, we may utilize the hybrid automatic-repeat-request (HARQ) technique to obtain the time diversity gain via the retransmissions in different time slots. Furthermore, to maximize the system throughput, we may introduce the adaptive modulation and coding (AMC) technique to adapt to the fading channel. In this thesis, we designed a relay-based cooperative communication system with HARQ and AMC to combine the above benefits for reliable high-speed wireless transmission. To get more practical results, we tested our systems based on the high speed downlink packet access (HSDPA) system.