寬頻分碼多重進接空-時耙狀接收器之演算法及效能評估

Abstract

為了實現第三代無線行動通訊，使用結合了許多先進技術的寬頻分碼多重進接 (W-CDMA) 系統是必然的趨勢。 在本篇論文中，吾人以電腦模擬實現寬頻分碼多重進接系統上鏈端的接收器，並使用陣列天線 (antenna array) 來改進多重進接干擾 (MAI) 之消除。 具體而言，本論文所實現的接收器為所謂之空-時耙狀接收器 (space-time RAKE receiver)，它結合了耙狀接收器 (RAKE receiver)、陣列天線 (antenna array)、傳送功率控制 (transmit power control) 等演算法。 為求進一步消除多重進接干擾，吾人引入多用戶偵測系統 (multiuser detection) 中常用的平行干擾消除演算法 (parallel interference canceller) 而得到一種新的空-時多階平行干擾消除器架構。 此種消除器可以強化空-時耙狀接器的效能並有效消除強干擾。 吾人接著討論時序錯誤的問題，並使用碼擷取 (code acquisition) 的演算法估得粗略的時序，再用碼追蹤 (tracking) 的演算法使時序維持正常而不致偏離。為使強干擾不致影響碼擷取的運作，吾人引入陣列天線來消除強干擾以改善碼擷取的效能。 電腦模擬結果顯示，本論文所提及之強化空-時耙狀接收器能在3GPP規格下之環境有效運作。

To realize the third-generation mobile communication systems, known as International Mobile Telecommunications-2000 (IMT-2000), the wideband DS-CDMA (W-CDMA) incor- porating as many recent technology developments as possible is necessary. In the thesis, we consider the use of antenna array technology for the reduction of multiple access inter- ference (MAI) in the implementation of the W-CDMA uplink receiver. In particular, the array receiver, RAKE reception, and transmit power control (TPC) are combined leading to an uplink space-time (S-T) RAKE receiver. To further reducing MAI, an auxiliary multi- stage multiuser detector using the parallel interference canceller (PIC) is incorporated. The space-time Multistage Parallel Interference Canceller (S-T MPIC) is shown to signi?cantly enhance the S-T RAKE receiver in the presence of strong MAI. We also discuss the timing error problem and employ code acquisition algorithms to roughly estimate the initial tim- ing and tracking algorithms to keep track of the timing. To combat the strong data traAEc interference during the acquisition period, the antenna array is incorporated, leading to a S-T acquisition scheme. S-T acquisition is shown to signi?cantly outperform the conven- tional correlator-based acquisition in the presence of strong interference. The eAEcacy of the proposed enhanced S-T RAKE receiver is con?rmed by numerical results in a simulated environment following the 3GPP speci?cations.