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1 引言数字传输是数字通信过程中的关键环节,它要适应信道的千变万化,承受各种不同程度的畸变、失真,以及自然与人为的形形色色干扰,还要随着人们需求的增长不断提高频率利用率和可靠性。近年来,随着微电子学、计算机科学、数字信号处理、通信理论以及有关学科的发展,数字传输有了很大发展,以话带MODEM为例,50年代为600b/s,60年代为2400b/s,70年
1 Introduction Digital transmission is a key part of the digital communication process. It has to adapt to the ever-changing variety of channels, withstand various degrees of distortion, distortion, and natural and man-made all kinds of interference. It also needs to increase frequency as the demand of people increases. Rate and reliability. In recent years, with the development of microelectronics, computer science, digital signal processing, communication theory and related disciplines, great progress has been made in digital transmission. Taking the MODEM as an example, there are 600b / s in the 1950s and 2400b in the 1960s / s, 70 years