有線通道數位傳輸時序回復法之研究

Abstract

雜訊與碼際干擾(ISI)為影響數位資料傳輸系統性能的兩個主要因素。一個適當的時序相位可以有效消除接收訊號的碼際干擾成份，而不適當的時序相位則會增大其成分。為了要克服上述的問題，吾人需設計一時序回復器來自動調整至最佳的時序相位。一般而言，可靠的時序回復演算法需基於通信通道的特性來發展。在本論文中，吾人將介紹一些時序回復器的方法及其原理，而其演算法為使用最陡降落梯度法演算法，並能自動調整時序相位直到最佳的結果。經由電腦模擬，吾人比較了各時序回復器之優缺點並對其限制加以論述。另外，吾人研究Mueller and Muller detector(MMD)在實際傳輸上之特性，並將其應用在脈衝響應較長的通道。由模擬結果可證實MMD在有線通道上傳輸十分可靠而其他方法則在收斂性上較佔優勢。

Noise and intersymbol interference(ISI) are the main factors which adversely affect the performance of the digital data communication system. An proper timing phase may result in the cancellation of the aliased components of the received signal, while a improper timing phase may result in the augmentation of the components. To overcome the above problem, a timing recovery scheme is designed to automatically adjust the optimum timing phase. A reliable timing recovery algorithm has to developed based on the characteristics of the communication channel.In this thesis, we will introduction some timing recovery schemes and their principles. These algorithms work with the steepest descent gradient algorithm and are able to automatically adjust timing phase to achieve the best result. Through a set of computer simulations, we compare the advantages and disadvantages of each scheme and discuss on their restrictions. In particular, we study Mueller and Muller detector(MMD) in practical transmission and apply it to the channel with a long impulse response. It is shown that MMD performs quite reliable for digital transmission over wired channel, while others have advantages in convergence.