离散多频音调制系统子信道的分级利用方法

A Hierarchical Scheme for Utilizing Subchannels of Discrete Multi tone System

离散多频音调制将信道划分成许多子信道，可分别加以处理和利用。子信道如果加上编码，可获得４～５ｄＢ增益，但使复杂度和时延增大。一般不对称数字用户环路允许在全编码和全不编码之间作选择。本文提出的子信道分级利用方案，针对不同业务对实时性、可靠性的不同要求，仅对部分信道进行编码，以得到较大的灵活性。为此推导了一套比特分配、能量分配的设计公式，物理概念清楚。

Discrete Multi tone(DMT) technique divides a channel into many subchannels that can be processed and utilized respectively. With the aid of encoding,subchannels can obtain gain of 4 to 5 dB,but result in increased complexity and delay. Generally, ADSL(Asymmetric Digital Subscriber Loop)allows all the channels to be encoded or not to be encoded. To obtain larger flexibility,this article presents a hierarchical scheme for utilizing subchannels which encodes subchannels partially for the different requirements of real time property and reliability of different services. A set of design formulas about bit assignment and energy assignment are derived which have clear physical meaning and practical value.