新的時間同步演算法應用於3GPP LTE Downlink細胞搜索

Abstract

在長期演進技術(LTE)系統下，我們提出一個好的時間同步方法和初始細胞搜索流程。初始細胞搜索流程主要分成四個步驟，第一步驟必須將接收端所接收到的訊號，經過低通濾波器將同步訊號以外的資料濾掉；第二步驟執行時間同步，利用第二同步訊號的共軛對稱，對載波頻率偏差較不敏感的特性，可以提高時間同步的準確性，找出第二同步訊號的起始點；第三步驟利用找到的第二同步訊號的起始點，經過結合循環字首盲檢測與主同步訊號偵測得到主同步訊號的位置和細胞第二編號，並解決載波頻率偏移問題，第四步驟則是利用所得到的細胞第二編號進行第二同步訊號的偵測，得到細胞第一編號，藉由結合第一編號與第二編號，可以得到完整的細胞編號，細胞搜索也就此完成。

The invent is a method of a new timing synchronization method and 3rd Generation Partnership Project (3GPP) Long Tern Evolution (LTE) cell search procedure is proposed. The procedure can be divided into four steps. Firstly, received signal has passed a low-pass filter to remove other data which are not synchronization signals. Secondly, timing synchronization is performed by Secondary synchronization signal’s conjugate symmetry that is immune to carrier frequency offsets (CFO). The property can raise the timing synchronization accuracy. Thirdly, in time or in frequency domain, use detected SSS starting position and perform joint of blind cyclic prefix (CP) detection and primary synchronization signal (PSS) detection to find out CP length, PSS position, and . The CFO problem can be also solved in this step. Finally, secondary synchronization signal (SSS) detection is adopted. After going through procedure we can get physical-layer cell identity (Cell-ID) and cell search is accomplished.