最佳化DMT收發器應用於ADSL迴路上的成效評估

Abstract

近年來, 多載波調變收發器 (DMT Transceiver) 被廣泛地應用在非對稱數位用戶迴路 (Asymmetric Digital Subscriber Line, 簡稱 ADSL) 的傳輸。 大部分的多載波調變收發器是利用離散複立葉逆轉換 (Inverse Discrete Fourier Transform) 矩陣來實現傳送器 (transmitter); 利用離散複立葉轉換 (Discrete Fourier Transform) 矩陣來實現接收器 (receiver)。 我們稱此類收發器為利用離散複立葉轉換來實現的收發器 (DFT based transceiver)。 在這篇論文中, 我們提出了最佳化收發器 (Optiaml transceiver)。 此收發器在固定的出錯率 (probability of error) 以及傳輸速率 (transmission bit rate) 之下, 所需要的傳輸能量 (transmission power) 將會是最少的。 我們將比較利用離散複立葉轉換來實現的收發器以及最佳化收發器兩者的效能。與 DFT based transceiver 相較之下, 實驗數據顯示最佳化收發器能夠以較少頻道數目 (number of subchannels) 而達到相同的效能。 所以, 我們可以使用最佳化收發器來減少系統的複雜度以及系統延遲 (system delay), 達到更優越的效能。

The DMT (discrete multitone modulation) transceivers have been shown to be a very useful technique for ADSL (Asymmetric Digital Subscriber Line) transmission. Most of the DMT systems that have been studied and implemented are DFT based. The transmitter consists of an IDFT matrix. In this thesis, optimal transceivers that minimize the transmission power for a given probability of error and transmission bit rate will be considered for ADSL applications. We will compare the performance of the optimal DMT systems to that of DFT based DMT systems. The experiments show that optimal DMT can have the same performance as DFT based DMT using a significantly smaller number of subchannels. Therefore we can reduce the number of subchannels and also system delay using the optimal DMT system.