基于Matlab的离散通信信道设计与仿真
摘要
通信信道代表了发射机与接收机之间的物理媒介，而信道模型则以数学的或算法的形式来表征信道的I/O关系；完成一个有3条固定路径的AWGN多经信道的Matlab设计与仿真，并基于该信道分析仿真QPSK系统的BER性能。通信系统的一般模型为信源（信息源，也称发终端）的作用是把待传输的消息转换成原始电信号。信源输出的信号称为基带信号。所谓基带信号是指没有经过调制（进行频谱搬移和变换）的原始电信号，其特点是信号频谱从零频附近开始，具有低通形式，。根据原始电信号的特征，基带信号可分为数字基带信号和模拟基带信号，相应地，信源也分为数字信源和模拟信源。 发送设备的基本功能是将信源和信道匹配起来，即将信源产生的原始电信号（基带信号）变换成适合在信道中传输的信号。
本文利用Matlab软件中的Communication Toolbox（通讯工具箱）进行对数字通信的仿真和设计，其中可以直接调用工具箱中的函数，也可以使用Simulink构建自己的仿真模块。仿真包括基带传输的仿真和载波提取分析。傅立叶变换在MATLAB中的技术原理：阐述傅立叶变换，其中体现离傅立叶级数，快速傅立叶变换：阐述Z变换的概念，解释Z变换和傅立叶变幻的关系：最后实现Z变换在MATLAB中的实现。
关键词：通信信道；离散通信信道；Matlab软件；
Abstract
Communication channel represents the physical medium between transmitter and receiver, and the channel model places in the form of mathematics or algorithms to characterize the I / O relationship channel; completed a three fixed path of Matlab design AWGN multipath channel through and simulation, and analysis of simulation based on the channel BER performance of QPSK system. A general communication system as the source (source of information, also known as terminal hair) role is to convert the message to be transmitted into the original electrical signal. Signal source output is called a baseband signal. The so-called baseband signal without modulation means (spectrum transform and move) the original electrical signal, which is characterized by near zero frequency signal spectrum from the start, a low-pass form. According to the characteristics of the original electrical signal, the baseband signal can be divided into digital baseband signal and an analog baseband signal, and accordingly, the source is also divided into a digital signal and analog sources. The basic function of the transmission device is to source and channel match the original electrical signal (baseband signal) is about to produce the source is converted into a signal suitable for transmission channel.
In this paper, Matlab software Communication Toolbox (Communication Toolbox) performed on digital communication simulation and design, which can be called directly toolbox function can also be used to build your own Simulink simulation module. The simulation includes a baseband transmission carrier extraction simulation and analysis. Fourier Transform principle in MATLAB: This paper Fourier transform, which reflect from the Fourier series Fast Fourier Transform: This paper describes the concept of Z transform, Z-transform and Fourier explain the changing relationship: the final realization of the Z-transform in MATLAB implementation.
Keywords: communication channels; discrete communication channel; Matlab software;
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