個別通道特性評估技術應用於正交分頻多工訊號調變系統

Abstract

隨著近代科技的快速發展，手持式行動裝置與大量線上多媒體服務已成為時代的趨勢，通訊系統也隨之發展出更新的應用層面與技術。為了滿足如超高畫質電視(UHDTV)、3D電視、互動式多媒體等高速多媒體影音服務需求，解決資料壓縮與解壓導致的訊號失真與延遲問題、提高資料傳輸速率已是必然的趨勢。提高訊號載波頻率以及頻譜效率是增加資料傳輸速率的兩大關鍵。但是高頻的訊號無論是在傳統同軸電纜或是大氣中都會受到相當大的傳輸損耗，導致傳輸距離受到限制。 為了解決以上問題，將正交分頻多工技術(OFDM)應用於被動式光纖網路(PON)上被視為是極具潛力的選項之一，此方法可以提供足夠的頻寬並且解決傳輸損耗的問題。然而傳統OFDM-PON系統被人質疑的缺點在於使用者的訊號安全性和需要接收多餘的訊號。本論文在傳統OFDM-PON的基礎上加入了個別通道特性的評估，藉此減少用戶端設備成本和運算時間，透過對訊號做預先處理的方式提高使用者訊號的安全性。成功在32 Groups的情況下將取樣率和FFT Size減少至傳統方法的1/32倍，並且能成功應用在高頻RoF和基頻EML系統上。

With the rapid development of modern technology, handheld mobile devices and extensive online multimedia services have become a trend. Therefore, communication system has developed more application and technology, such as UHDTV, 3D TV, and interactive multimedia which demanded for high-speed multimedia services. To meet the front of the technology, have to solve the signal distortion, delay problem and increasing the data rate. Including carrier frequency and spectral efficiency were key points to increase data rate. But high carrier frequency signal has great power lose for signal transmission either in the air or the coaxial cable. There were limitations at transmission distance. To solve the above problems, orthogonal frequency-division multiplexing passive optical network is viewed as an outstanding candidate, because of its superior performance, such as its high spectral efficiency, and has less power loss than traditional coaxial cable. But the most trade-off for traditional orthogonal frequency division multiplexing passive optical networks (OFDM-PON) system is the insecurity and the redundancy of data receptions. In this paper, we added channel characteristic division technology at OFDM-PON system to reduce the cost and computation requirement at the user side, so that the security is further strengthened. In this thesis, when the Group number is 32, the sampling rate and FFT size can be reduce to 1/32 of traditional meth. This technology can apply in RF band at Radio-over Fiber (RoF) system and baseband signal at electro-absorption modulated laser (EML) system.