單載波分頻多重存取系統分集技術之研究

Abstract

長期演進 (LTE) 為3GPP制定之最新一代行動通訊系統標準。LTE 之上行鏈路中使用單載波分頻多重存取系統，而下行鏈路則使用正交分頻多工系統。此篇論文介紹在多重路徑衰減通道下，如何利用分集技術改善錯誤率效能。在接收端分集技術中，我們分別介紹選擇式分集技術、等增益合併和最大比值合併分集技術。在結合傳送與接收端分集技術中，我們在兩根與四根傳送天線下，分別介紹空時區碼 (STBC)、分頻區碼 (SFBC)與傳輸波束成型(transmit beamforming)等方法。我們接著介紹降低峰值對平均功率比(PAPR)的方法，其中分為兩種：第一種為使用不同映射方式之方法，例如 SC-SFBC 與 SC-QOSFBC；另一種為使用clipping方法達到降低PAPR。我們比較以上分集技術在單載波分頻多重存取系統與正交分頻多工系統之錯誤率效能，也比較以上降低PAPR方法在單載波分頻多重存取系統下之PAPR效能，最後針對電腦模擬結果做一些討論及結論。

Long Term Evolution (LTE) is the latest standard for the next generation mobile telecommunication system from the 3rd Generation Partnership Project (3GPP) group. LTE is based on Single-Carrier Frequency Division Multiple Access (SC-FDMA) on the uplink, and based on Orthogonal Frequency Division Multiple Access (OFDMA) on the downlink. In this thesis, we investigate diversity schemes which are effective for improving the Bit Error Rate (BER) performance in a multipath fading channel. With receive diversity, there are three techniques which are Selection Diversity (SD), Equal Gain Combining (EGC), and Maximum Ratio Combining (MRC). And with transmit and receive diversity, we present two methods: Space Time Block Code (STBC) and Space Frequency Block Code (SFBC) for two transmit antennas, then we extend it for four transmit antennas and investigate the transmit beamforming scheme. Afterwards, we investigate two methods called SC-SFBC and SC-QOSFBC, and the clipping method to reduce the peak-to-average power ratio (PAPR). Finally, we compare SC-FDMA and OFDMA systems with the above mentioned diversity schemes in BER performance, and also in PAPR performance for the three PAPR reduction methods. According to our simulation results, we have some discussions and make the conclusions.