應用於LTE接收端頻域上之時間同步器

Abstract

隨著無線通訊技術的快速發展，超高速傳輸系統已成為新一代無線通訊系統的發展核心，然而高速傳輸需要更快的取樣頻率，這將使得「大量取樣頻率偏移」此問題發生的機率增加，這將造成訊號嚴重的衰減。因此，本論文致力於研究在1024-FFT下超高速多天線(MIMO)正交分頻多工(OFDM)系統中，頻率域上的時間同步器，達到同步取樣的目的。 本論文所提出的演算法，主要應用在於3GPP 所制定的無線區域網路標準 LTE上，藉著封包間格式固定的參考信號，利用其彼此的相關性對取樣誤差作估計，並以調節取樣相位的方式以及插值器補償取樣時脈誤差。另外，透過2維的通道估計器，我們能夠處理前向補償的剩餘部分，使得整個過程可以有效地和快速地執行取樣同步。

Due to the explosive growth demand for wireless communication, the next-generation wireless communication systems are expected to provide high-speed and high-throughput. However, high-speed transmission needs high sampling rate, which would cause wide sampling clock offset. Based on phase adjustment, this work investigates a frequency-domain timing synchronizer to perform coherent sampling for 1024-FFT Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) timing recovery. In the proposed algorithm, we use a multiphase all-digital clock management (ADCM) which can generate more than 16 phases over GHz to adjust sampling phases and utilize the reference signals in one sub-frame to estimate the sampling phase error. Moreover, by combing the 2-dimensional channel estimator and equalizer, we are able to deal with the remaining part of the previous compensation. The entire process can perform the sampling clock synchronization efficiently and quickly.