可移動式通訊系統與高速無線網路存取一直驅使無限寬頻通訊的需求不斷增加，而通道容量是滿足此需求的關鍵。在1998年，Foschini和Gans、Teletar同時證明了多重天線系統能達到遠高於單天線系統的通道容量。
時間空間碼在近幾年已被證明為利用多重天線之強大科技，從1998年起，Alamouti、Tarokh、Stephen…等人提出各種時間空間碼的設計，並不斷加以改進。在2005年，鄭博士與呂教授發表一篇論文有關時間空間碼的設計，搭配以連續相位頻移鍵控調變，此種編碼方式能得到相當好的成效。
在這篇論文中，我們提出一個新的時間空間編碼方式，可以搭配正交振幅調變或是相移鍵控調變，此種編碼包含一個迴旋編碼器以及一個空間編碼器。在時間相關性衰退通道的情況下，我們加入一個交錯器，置於迴旋編碼器和空間編碼器之間，可以有效降低時間相關性衰退的影響，且所用的交錯器層級越多，達到的效果越好。在接收端包含一個解交錯器以及一個Viterbi解碼器，以此得到最佳錯誤率解碼。在此編碼之設計標準之下，我們可以以相當簡單的空間編碼器，以及之前陳博士與呂教授所研發的演算法得到的迴旋碼，來達成我們的目標。我們提出的編碼方式可以減輕一個時間空間碼長久以來的問題─在傳輸速率以及多重性(diversity)之間的交換(tradeoff)，所需付出的代價僅是電腦運算的複雜度。另外，此種時間空間碼能得到的多重姓增益（diversity gain）為迴旋碼的有效碼長度（ECL）與傳送端、接收端天線個數三者的乘積。最後我們以電腦模擬證明此編碼方式可以得到相當好的成效。

In this thesis, we proposed a new space-time encoding scheme for
QPSK modulation over frequency-nonselective fading channels. This
scheme alleviates the tradeoff between the diversity and the rate of space-time coding
by increasing decoding complexity. We derived the space-time code design
criteria over fast fading channels.
This scheme consists of a systematic convolutional encoder over a ring and
a spatial encoder, and in addition, an interleaver to combat with correlated fading.
Simulation results have confirmed the excellent performance of our proposed scheme.

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