現今的行動通訊系統中，3GPP LTE/LTE-A獲採行為第四代無線通訊的主要規格之一，主要技術採用正交分頻多工存取調變，並且訊號中攜帶的同步訊號對於高頻選擇性通道有較強的抵抗能力，本論文採用3GPP LTE/LTE-A的訊號規格以及通道參數來進行鄰近細胞搜尋演算法的模擬並實作硬體。 演算法中分為四個部分，在進行和基地台同步前我們必須要先知道基地台的識別碼，識別碼又分為分區細胞索引(sector cell index)跟細胞識別碼組(cell ID group)，針對移動中的使用者設備(user equipment)提供換手(handover)前置作業時，勢必會收到原先的服務細胞基地台與前往的鄰近細胞基地台兩種訊號，我們要從這些訊號中得到分區細胞索引與細胞識別碼組來組合成原先服務細胞基地台的識別碼與鄰近細胞基地台的識別碼，提供換手時基地台的最基本資訊，這四個演算法進行順序為偵測服務細胞的主要同步訊號、偵測鄰近細胞的主要同步訊號、偵測服務細胞的次要同步訊號最後是偵測鄰近細胞的次要同步訊號，我們利用片段交互相關(partial correlation)來減少通道之間的相位差異性，並且在偵測鄰近細胞的主要與次要同步訊號時，以消去服務細胞為主要目標的方式，消除干擾以便準確的偵測鄰近細胞。 硬體方面我們建立四套硬體分別處理我們演算法中的四個部分，主要共通的硬體為partial correlation的部分，我們建立一套correlation bank，剩下的即是四套演算法的序列產生和序列運算，務求將硬體降低且同時維持我們演算法的效能。 我們的非同調鄰近細胞搜尋演算法即使在360km/hr的環境下也有良好的表現，與其他方法比較過後，效能仍然突出，並且以維持良好效能的目標下，盡量減少硬體使用資源來實作硬體，足以彰顯本論文的演算法在硬體資源降低時的可靠性。 A new neighbor cell search algorithm for LTE/LTE-A systems is presented in this paper. To improve the interference problem in channel estimation for coherent SSS detection in the conventional neighbor cell search approaches, we propose a non-coherent scheme that takes advantage of the similarity of channel responses at adjacent subcarriers. The proposed neighbor cell search procedure not only includes both PSS and SSS detection, but also can combat different carrier frequency offsets that the home cell signal and the neighbor cell signal may suffer. The removal of the home cell synchronization signals in our algorithm converts the neighbor cell PSS and SSS into new sequences for recognition, respectively. By examining the cross-correlation properties of the new sequences, we show that partial correlation can well detect the neighbor cell sector ID and group ID through the new sequences. From simulation results, it is also clear that the proposed algorithm has good detection results and outperforms the conventional coherent approaches. As to the hardware design, we have the common hardware design, the correlation bank. The correlation bank operates the partial correlation in our four parts of non-coherent neighbor cell algorithm. The remaining part of hardware design is about the sequence generation and sequence verification to determine the result of sector cell index and cell ID group. It is verified to have satisfying performance under mobility of 360 km/hr. In the end, we compare not only performance but also hardware resources to other method to demonstrate our proposed algorithm: Non-coherent Neighbor Cell Search for LTE/LTE-A system is robust.
