具相位雜訊抑制能力之IEEE 802.11a OFDM接收機設計

IEEE 802.11a OFDM Receiver Design with Phase Noise Suppression Capability

蔡昀展(Yun-Chan Tsai)

指導教授 ： 黃正光

元智大學/工程學院/電機工程學系/碩士(2003年)

摘要

在本論文中，吾人探討正交分頻多工系統的基本原理以及IEEE 802.11a標準。然後，吾人系統化地介紹如何進行接收機設計，特別是同步演算法，包括碼框偵測，符碼時間同步，頻率偏移估測，相位飄移追蹤以及通道估測。在選擇適當的同步演算法並且決定參數之後，吾人透過電腦模擬來驗證這個設計，其中，通道使用了白高斯雜訊通道以及均方延遲擴展為50ns的頻率選擇性慢速瑞雷衰減通道。模擬結果符合IEEE 802.11a對於封包錯誤率的要求。最後，吾人探討相位雜訊的性質及其對正交分頻多工系統的影響。吾人採用一個基於最小平法法則的共相位估測器並結合最小均方誤差等化來抑制相位雜訊。吾人將此演算法與接收機設計整合，並使用電腦模擬來檢驗這個設計在使用高階調變以及相位雜訊干擾之下的效能。模擬結果依然符合IEEE 802.11a對於封包錯誤率的要求並且證明了吾人所提出之相位雜訊抑制演算法的效能。

關鍵字

保護區間 ； 循環延展 ； 資料符號 ； 多載波 ； 正交分頻多工系統 ； 載波頻率飄移 ； 頻道間干擾 ； 相位雜訊

並列摘要

In this thesis, we study the fundamental principle of OFDM systems and the specification of IEEE 802.11a standard. Then, the receiver design procedures, in particular, the synchronization algorithms are systematically introduced. The synchronization algorithms are composed of packet detection, symbol timing estimation, frequency offset estimation, phase shift tracking and channel estimation. After choosing suitable synchronization algorithms and setting up the parameters, we examine our design via computer simulations in both AWGN and frequency selective slowly Rayleigh fading channel with RMS delay spread of 50 ns. The simulation results conform to the packet error rate requirement of IEEE 802.11a standard. Finally, we study characteristics of phase noise and its impact on OFDM systems. A least -square based CPE estimator is combined with the MMSE equalizer to suppress the phase noise. We integrate this algorithm with our IEEE 802.11a receiver design and investigate its performance with high order modulation and phase noise via computer simulation. The simulation results still meet the packet error rate requirement of IEEE 802.11a standard and the effectiveness of proposed phase noise algorithm is justified.

並列關鍵字

guard interval ； cyclic extension ； data symbol ； multicarrier ； orthogonal frequency division multiplexing ； OFDM ； frequency offset ； Inter-Channel Interference ； ICI ； phase noise

參考文獻

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