LTE下傳系統中基於部分相關聯合偵測法之細胞搜尋程序

在現行的蜂巢式網路系統中，使用者設備(User Equipment；UE)端必須先執行所謂的細胞搜尋程序，這個步驟是為了讓UE端能夠取得同步的資訊。並且UE端利用這些資訊盡快的與附近擁有最好服務品質的基地台(Base Station；BS)作連結的動作。在本篇論文裡，我們將會介紹完整的細胞搜尋程序應用於第三代合作夥伴計畫(3rd Generation Partnership Project；3GPP)的長期演化(Long Term Evolution)下傳系統。我們所提出的細胞搜尋程序包含了三個步驟，分別是最大相似(Maximum Likelihood；ML)估測法、聯合偵測法、同調偵測法。 ML估測法是利用循環字首(Cyclic Prefix；CP)的特性來估測出符元時間及小數載波頻率偏移(Fractional Carrier Frequency Offset；FCFO)。接著我們利用頻域上的聯合偵測取得分區識別及整數載波頻率偏移(Integer Carrier Frequency Offset；ICFO)的資訊。此外，我們也探討二種不同的聯合偵測方法並且比較了它們的效能。在上述步驟完成之後，我們可以假設已知道次要同步訊號(Secondary Synchronization Signal；SSS)序列上的通道資訊。因為我們已先完成主要同步訊號(Primary Synchronization Signal；PSS)序列的偵測，並利用此PSS來作通道的估測。所以最後我們利用同調偵測的方法來取得群組識別的資訊。模擬結果證明我們所提出的方法相較於文獻的方法具有較低的偵測錯誤率及更強健的效能。

關鍵字

長期演化；細胞搜尋程序；載波頻率偏移；次要同步訊號；主要同步訊號

並列摘要

Within recently cellular systems, user equipment (UE) must perform the cell search procedure in order to acquire synchronization information. Because of having the best serving base station, the UE needs to establish connection as fast as it can. In this thesis, we are going to introduce a cell search procedure in 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) downlink systems. The proposed cell search procedure contains three steps, which are Maximum Likelihood (ML) estimation, joint detection and coherent detection. The ML estimation uses the characteristics of cyclic preﬁx in order to obtains the symbol timing and fractional carrier frequency offset (CFO). Then, we also need to acquire the sector identification (ID) and integer CFO from joint detection in the frequency domain. Furthermore, we investigated two kinds of joint detection method and compared their performances. After the above steps, the channel information on the Secondary Synchronization Signal (SSS) sequence can therefore be assumed to be known base on the Primary Synchronization Signal (PSS) sequence. So, we can detect group ID by coherent detection. Simulation results demonstrate that the proposed method with lower detection error rate is effective and robust compared with literature method.

並列關鍵字

LTE ； cell search procedure ； CFO ； SSS ； PSS

參考文獻

[2] 3GPP TS 36.211 V8.4.0 (2008-09) (Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation).

[5] Pei-Yun Tsai and Hsiang-Wei Chang, “A New Cell Search Scheme in 3GPP Long Term Evolution Downlink OFDMA Systems”. in proc. IEEE WCSP, 2009.

[7] D.T. Harvatin, R.E. Ziemer, “Orthogonal frequency division multiplexing performance in delay and Doppler spread channel,” in Proc. IEEE VTC, pp.1644-1648, May 1997.

[8] S. B. Weinstein, P. M. Ebert, “Frequency domain data transmission using reduced computational complexity algorithms,” IEEE Trans. Commun., vol.19, pp. 628-634, 1971.

[9] A. Peled, A. Ruiz, “Data transmission by frequency- division multiplexing using the discrete Fourier transform,” in proc., IEEE Inf. Conf., Speech, Signal Processing, pp. 964-967, 1980.

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LTE下傳系統中基於部分相關聯合偵測法之細胞搜尋程序

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