60GHz無線通訊系統相位雜訊消除方法之研究

Abstract

由於無線通訊系統所需的傳送速率不斷提升，新一代的無線區域網路傳輸標準相繼被提出。IEEE 802.11ad標準使用的是不同以往的60GHz頻帶來傳送數據，其傳輸速率與可支援的容量皆有明顯的提升。IEEE 802.11ad使用的傳輸模式可分為正交分頻多工系統與單載波區塊傳輸系統。因為60GHz頻帶訊號容易衰減，除此之外還需克服一些其他技術上的問題，其中一個問題即為相位雜訊。造成相位雜訊的原因為傳送端與接收端震盪器的不穩定，而通常相位雜訊主要會產生兩個影響，分別為共同相位錯誤與子載波間干擾效應。本篇論文將於IEEE 802.11ad標準下討論消除相位雜訊的方法，分別使用了相位雜訊抑制演算法(Phase Noise Suppression Algorithm)來消除共同相位錯誤產生的影響，子載波間干擾修正法(ICI Correction Algorithm)來降低子載波間干擾效應，以及利用循環字首中不受碼際干擾區域與原來相對應的傳送訊號符元作線性組合的方法來改善子載波間干擾效應，並可降低系統複雜度。最後，我們再經由電腦模擬比較各個方法的系統效能。

Recently, as the data rate in wireless communication systems increases rapidly, new wireless transmission standards for local area network systems have been proposed. IEEE 802.11ad, one of new wireless local area network standards, uses two transmission schemes in physical layer, which are OFDM and SCBT respectively. In addition, IEEE 802.11ad utilizes 60GHz band to transmit the signal, and therefore enhances the data rate and throughput. However, since 60GHz belongs to millimeter frequency band, IEEE 802.11ad suffer from high signal attenuation. Besides, there are several other problems in IEEE 802.11ad. One of these problems is phase noise. Phase noise results from the imperfection of the local oscillators and causes common phase error(CPE) and inter-carrier interference(ICI). In this thesis, we examine phase noise suppression methods for IEEE 802.11ad. Specifically, this study uses the Phase Noise Suppression Algorithm to mitigate the CPE and implements ICI Correction Algorithm to combat the ICI. Furthermore, we linearly combines the ISI-free samples in cyclic prefix with the corresponding samples in the transmitted symbol to reduce ICI and also reduce the complexity of system. Finally, we compare the system performances of different phase noise suppression methods.