垂直正交分頻分碼多工調變系統中信號同步之研究

Abstract

垂直正交分頻分碼多重進接系統結合了分碼多重進皆與垂直正交分頻多工的優點可提供高傳輸速率，是第四代蜂巢式行動通訊系統熱門的選擇。信號同步則是一通訊系統中很重要的部分，其中包含整數及小數部分載波頻率漂移估計、符元時序估計等。本論文提出兩種信號同步的方法用於下鏈及上鏈垂直正交分頻分碼多重進接系統，主要是以領航訊號和護衛間隔為基礎的兩種方式，將針對其運作原理及演算法做詳細的介紹。 為了驗證同步接收機的效能，我們針對不同的通道環境進行電腦模擬，模擬的內容包含不同的用戶數目，不同方法，不同系統參數下系統的性能表現，以其定出最佳的系統參數，找出最適於系統之同步方法。我們最後提出結論與未來的研究方向。

An OFDM-CDMA system combines the advantages of CDMA and OFDM to provide high data rate transmission, and it is one of the promising choices for the fourth generation cellular mobile communication system. Synchronization is an important part of an OFDM/CDMA communication system, which includes integral frequency offset, fractional frequency offset and symbol timing estimation. In this thesis, we propose two methods of synchronization for both downlink and uplink OFDM-CDMA systems, which are based on the pilot signal and the guard interval. In this thesis we describe the operation principles and the algorithms of these two methods in details. In order to verify the performance of the receiver, computer simulations are conducted under different channel conditions. Our simulation results cover the performance of the two synchronization methods under different system parameters and user numbers. From the simulation results, we can determine appropriate parameters of system and method to use. Finally, we draw a conclusion and comment on possible future research directions.