應用於地面數位電視廣播系統之時序同步化設計

Abstract

對於正交分頻多工的通訊系統而言，時序同步化是非常重要的，影響傳輸效能甚大，本論文的目的是設計一套時序同步化機制其中包含符號同步和取樣頻率同步。在此我們選擇地面數位電視廣播系統作為研究主題，我們在Matlab上建立了一個完整的模擬平台其中包含傳送端、通道模型以及接收端，我們會先對平台做一個完整介紹，並且把各種通道模型做一份完整的分析。 在同步系統的第一步，我們利用週期尖峰的特性偵測傳輸模式與防護區間的長度，之後我們對許多簡略符號同步的演算法做了一個詳盡的比較，為了找到更精確的符號邊界，我們提出了一套具有創新的尖峰偵測策略的低複雜度精準符號同步方法。在取樣頻率同步的部分，我們提出一套全數位的同步機制，其中包括一個內含內插與降頻功能的重新取樣器，以及新提出的以線性最小平方法理論為基礎的取樣頻率飄移偵測設計，再加上可多級變動係數的循環濾波器。我們會秀出整個系統的效能以及對都卜勒效應的容忍度，最後，我們會對每塊模組做硬體架構上的說明。

The synchronization of symbol timing and sampling clock is very important for the OFDM communication system. In this thesis, a whole timing synchronization scheme including symbol synchronization and sampling clock synchronization is presented. The DVB-T (Digital Video Broadcasting – Terrestrial) system is chosen for the research topic. A complete simulation platform which contains transmitter, channel and receiver is built in Matlab. The overview of DVB-T system is presented first. Then the various channel distortions like multipath fading, Doppler, CFO and SCO will be analyzed clearly. Employing flat peak period decision, the blind Mode/GI detection is exploited as the first stage of synchronization. A detail comparison of different coarse symbol synchronization algorithms is then presented. For more accurate symbol timing, we will illustrate the proposed low complexity fine symbol synchronization with new peak detection strategy. In sampling clock synchronization, a proposed resampler combining interpolator with decimator can reduce nearly half of power consumption. Subsequently, a SCO estimation based on LLS algorithm with the multi-stage tracking loop is proposed which improves the conventional designs. At last of this thesis, the architecture design of each block is presented respectively.