60 GHz 光載微波訊號系統中以單載波分頻多重存取技術傳輸並提供適應性位元負載演算法

Abstract

近幾年來，在人們廣泛的使用行動裝置及多媒體應用程式推陳出新下，人們在無線傳輸的需求大量激增，進而對無線傳輸的要求(例如:資料品質、傳輸速度及資料傳輸量)大幅的提升。 因此拓展更寬的頻寬來提高資料傳輸量是必然的趨勢，而美國聯邦通信委員會在高頻 60-GHz上釋出了7-GHz免認證頻寬，此舉能有效的提升資料傳輸量。然而在傳輸高頻訊號時 ，使用了光載無線(Radio-over-fiber)系統，以光纖取代傳統的同軸電纜。相較於同軸電纜，光纖能承載更高頻的訊號及擁有較低的功率損耗，因此能夠有效的延長高頻訊號傳輸的距離。然而傳輸訊號時，光通訊上廣泛使用的正交分頻多工調變訊號有峰均值較高的問題存在，系統上的非線性響應將造成訊號品質明顯的變差。因此在本論文中以單載波分頻多重存取技術來傳輸訊號，其調變後訊號擁有較低峰均值比，在系統上能有效的避免非線性響應，因此擁有較好的訊號品質，並提出多重使用者的適應性位元負載演算法，根據通道的響應分配資料傳輸的QAM數以提高資料傳輸率，而在論文中，分割7GHz頻寬為兩個各3.5GHz的頻寬，並產生訊號傳輸在10km光纖、3公尺的無線中，訊號分別達128 QAM 和64 QAM，資料傳輸率成功地從42Gbps提升為45.5Gbps。

Recently, mobile devices and multi-media applications become more and more widespread. The desire of wireless communication is explosively higher than before. So the requirements of transmission are asked for better such as signal quality and data rate. United State Federal Communications Commission released an unlicensed band at near 60 GHz (57-64 GHz) and large bandwidth enables to provide higher data rate. In order to transmit 60 GHz signal, Radio-over-fiber system is proposed for it. Due to low power consumption and sufficient bandwidth, optical fiber is a much better choice than coaxial cable. So RoF system is able to deploy system widely and extend coverage. When OFDM signal is transmitted in system, high peak-to-average power ratio is a big issue. Due to signal with high PAPR easily suffers non-linear effect, it makes signal quality worse. In the thesis, signal with SC-FDMA modulation has lower PAPR and performance of signal will be better. According to channel response, signal with proposed adaptive bit-loading algorithm enables to increase data rates. Results show that transmitted signal which combines two 3.5GHz groups is able to achieve 45.5Gbps data rate in the system with 10km fiber and 3m wireless transmission.