寬頻高速的資料傳輸服務的需求愈來愈高，而傳統的數據機已經不能符合這樣的需要。數位用戶迴路(Digital Subscriber Loop)是利用一對電話線提供電話服務，並提供一高速率之資料傳輸通道，這個技術的產生是因應今日生活中許多新型的應用，例如視訊點播(VOD)、影像電話、視訊會議，以及網際網路的蓬勃發展，這些都需要非常高的資料傳輸率，因而在光纖尚未全面鋪設前，數位用戶迴路成為寬頻服務的一種可行方法。而VDSL是數位用戶迴路系列中一項最新的技術，當使用在非對稱網路時，它可以提供高達54Mbps的下載速率及6.4Mbps的上傳速率，而當使用在對稱網路時，它可以達到2.3~34Mbps傳輸服務。
射頻干擾 (radio frequency interference) 是離散多載波調變式VDSL傳輸系統中最具威脅性的干擾。為了解決這個問題，已經有許多不同的方法被提出，其中的一種是以數位的方式並運作在頻率域中，而這種方法主要的精神在於利用一些合理的假設及一些已知的訊號來還原頻率域的射頻干擾訊號，並進一步將之扣除。而UPBO技術是解決在VDSL嚴重的串音問題。

在本篇論文中，我們先將比較之前提出的方法在各種情況下的表現，如在不同的VDSL標準、基頻訊號的頻寬、及不同的subtone數目，然後說明這些方法的缺點。最後，我們根據之前所提到的方法並沿用它的射頻訊號數學模型，提出一個改進的射頻訊號消除器。根據模擬結果，這篇論文所提出的演算法能夠有效的消除各種情況下，VDSL系統中的射頻干擾，甚至可以應付多個射頻干擾的情況，並使運算複雜度降低。在UPBO部份，我們將對之前的方法做個總整理，並討論在標準中所規定的方法。最後，一個利用數位訊號處理器所實現的簡易VDSL會被討論。

Recently, the demand of high-speed data access is urgent. Discrete multi-tone (DMT) is one of the key technologies. It can provide broadband services on the existing copper telephone lines. A DMT-based technology called asymmetrical digital subscriber line (ADSL), which can provide downstream data rate up to 8Mbps, and upstream data rate up to 800kbps, has been wildly used. Very high bit-rate digital subscriber line (VDSL) is the latest generation of DSL, which can provide high downstream data rate up to 54Mbps, and upstream data rate up to 6.4Mbps for residential customers and 2.3~34Mbps data rate for businesses.
In this thesis, we propose an enhanced RFI cancellation scheme which provides a great improvement of the RFI suppression in VDSL, and can be easily extended to multiple RFI conditions. The simulation results show that the proposed RFI canceller is advantageous since its high performance and less computational complexity. Besides, due to serious FEXT in VDSL transmission systems, UPBO has to be used in VDSL to improve upstream transmission rate. We summarize several UPBO methods and compare their performances.

Finally, we set up a simplified DMT-based VDSL transmission system. With the help of a powerful digital signal processor, it’s easy and systematical to carry out a digital communication system.

[1]Peter S. Chow, John M. Cioffi, and John A.C. Bingham “DMT-based ADSL: Concept, Architecture, and Performance.” IEE Colloquium on High speed Access Technology and Services, Including Video-on-Demand, Digest No. 1994/192, pp. 3/1 – 3/6, 1994.
[2]Dr. Dennis J.Rauschmayer “ADSL/VDSL principles, a practical and precise study of asymmetric digital subscriber lines and very high speed digital subscriber lines.”
[3]ETSI TS 101 270-2 (V1.1.1): transmission and multiplexing(TM); Access transmission systems on metallic access cables; very high speed digital subscriber line (VDSL); part 2: transceiver specification.
[4]John M.Cioffi, Vladimir Oksman, Jean-Jacques Werner, Thierry Pollet, Paul M. P. Spruyt, Jacky S.Chow, Krista S.Jacobsen, “Very-High-Speed digital subscriber lines.” IEEE Communications Magazine, April, 1999.
[5]ETSI TS 101 270-1 (V1.2.1): transmission and multiplexing(TM); Access transmission systems on metallic access cables; very high speed digital subscriber line (VDSL); part 1: functional requirement.
[6]Denis J. G. Mestdagh, Mikael R. Isaksson, and Per ¨ Odling “Zipper VDSL: A solution for robust duplex communication over telephone lines.” IEEE Communications Magazine, May, 2000.
[7]Byung-Jang Jeong and Kyung-Hyun Yoo, “Digital RFI canceller for DMT based VDSL.” IEE Electronics Letters, vol. 34, No. 17, August 1998.
[8]Chien-Chung Chen, “An RFI Suppression Technique for DMT-Based VDSL Transmission Systems,” Master’s thesis, National Tsing Hua University, Hsinchu, Taiwan, ROC, June 2000.
[9]Shi-Hsin Chen, “Design and Implementation of an RFI Suppression Scheme for DMT-Based VDSL Transmission Systems,” Master’s thesis, National Tsing Hua University, Hsinchu, Taiwan, ROC, June 2001.