信道编码技术论文20783.doc.doc

数字通信系统中信道编码技术的研究 摘要 当今社会，随着科学技术的进步、经济的快速发展，在社会的各个不同领域，现代通信技术的不断发展，其应用领域迅速扩大，对无线信道传输数据的能力要求越来越高。人们对在无线信道中传输多媒体数据(包括语音、数据和图像等)日趋重视。无线信道具有时变性、衰减性、带宽资源有限、干扰很大等特点，因此若想在无线信道中实现多媒体数据的鲁棒性传输是一个具有很大挑战性的工作。要实现上述目标，必须考虑两个问题，第一，即是信源编码问题一目的在于尽量减少信号的冗余，增加系统的有效性;第二，即信道编码问题，与信源编码相反，信道编码是在信息序列中添加适当冗余，使系统能够纠正一定程度上的传输错误，增加系统的可靠性。但是在实际应用中，传输数据的无线信道非常复杂。在传输数字信号的时候，由于信道时变性、衰减性、带宽资源有限、干扰大等特点，以及加性噪声的影响，势必会造成接收端接收到的信号存在一定的差错。为提高无线信道传输数据的质量，应该在保证一定编码效率的情况下将误比特率降到最低。信道编码技术正是降低误比特率、提高通信质量的主要技术手段之一。 本文系统的介绍了数字通信系统的框架及基本原理，回顾了信道编码技术的发展历史，对线性分组码、卷积码、Turbo码做了详细介绍及Matlab仿真，并对仿真结果进行分析比较并得出结论，以使通信能无论在良好的环境还是在相对较复杂的环境下，都能高效、可靠的传输数据。 关键词：数字通信, 卷积码, Turbo码 THE RESEARCH AND IMPLEMENTATION ON CHANNEL CODING AND DECODING “TECHNOLOGY IN DIGITAL COMMUNICATION SYSTEM ABSTRACT With the rapid development of the new Technology, wireless communication system are widely used in different areas. The requirement of higher capacity of transmitting data is increasing dramatically for wireless channels.Pay attention to the applications of multimedia data(video,data, image)transmission over the wireless channel. But the wireless channels limited bandwidth resource, time-variation, the severe fading and the high error rates, so that is a big challenge in order to ensure the reliable multimedia data transmission. We must solve two problems, one is source coding that try to compress the source as to improve the high efficience of the system; the other is channel coding what is contrary to the source coding, try to protect the compressed source through adding some controllable bits in order to enhance the reliability of the system. But the wireless channel is complex in piratical application. Due to the properties of time-varying and damped bandwidth limited, disturbance and noises, there may exist large errors in received signals. In order to reduce bit error rate and improve the quality of communication, channel coding technology is one of the main methods. The paper introduces the system framework and basic pr