正交分頻多工存取系統上傳連結之干擾消除方法

Abstract

近來正交分頻多工存取系統(OFDMA)已經吸引廣泛的注目，由於當此系統提供可靠的多工存取同時也提供了極佳的頻譜效益和能對抗多路徑傳輸之影響。然而載波頻率偏差(CFO)發生在正交分頻多工存取系統當中，會破壞子載波之間的正交性進而產生子載波之間干擾(ICI)和多用戶存取干擾(MAI)；子載波之間干擾以及多用戶存取干擾會使系統的表現下降。在此篇論文當中，作者將提出兩種干擾消除方法:區塊平行干擾消除(Block Parallel Interference Cancellation)和區塊連續干擾消除(Block Successive Interference Cancellation)來解決載波頻率偏差在正交分頻多工存取系統之上連結問題。此兩方法皆是使用在區塊正交分頻多工系統上。在模擬結果可知，此兩方法皆是多級干擾消除架構而能夠有效的壓抑子載波之間干擾和多用戶存取干擾。再者可以利用Trench演算法來搭配實現Toeplitz反矩陣進而只需要O( )的運算量。良好的系統表現和合理的運算量將使這兩個方案在系統實現上更具吸引力。

The technique of Orthogonal Frequency Division Multiple Access (OFDMA) had caused much attention recently because of the excellent bandwidth efficiency and the ability of combating multi-path effects while providing reliable multiple access capability. The Carrier Frequency Offsets (CFOs) in the OFDMA system destroys the orthogonality among the subcarriers and results in the, Inter-Carrier Interference (ICI) and the Multiple Access Interference (MAI). Without proper resolution, the ICI and the MAI will degrade the system performance. In this thesis, we present two interference cancellation schemes: Block Parallel Interference Cancellation (BPIC) and Block Successive Interference Cancellation (BSIC), to solve the CFOs problem in the OFDMA uplink receiver. These two schemes are based on the block based OFDMA system. The simulation results show that the proposed methods can effectively suppress the ICI and the MUI by using multistage cancellation. In addition, we make use of the Trench algorithm to save the computation complexity of the Toeplitz matrix inversion required in the proposed algorithms, The Trench algorithm needs only O( ). Good performance and reasonable computation requirement of the proposed algorithm are attractive in the practical system implementation.