数字信道

Firstly it describes the development ,basic principle and application and propagation characteristic of mobile channel , then investigates the system structure of DAB transmitter and receiver separately and the key technology of realization of the digital audio broadcast system.And then discusses the system component of FFT －the demodulation module of OFDM .The 409- points FFT module employs a radix-4 decimation-in-frequency algorithm, includes arithmetic element , read and write address element ,twiddle factor element and control element , is realized by FPGA. In the end , the result is verified in the matlab .

首先概述了OFDM的发展、基本原理和应用以及移动信道的传播特性，接着分别研究了数字音频广播接收机和发射机的系统结构，以及数字音频广播系统实现的关键技术，然后详细论述了OFDM解调模块FFT的系统结构，主要研究了4096点FFT采用基－4按频率抽取实现的算法，整个FFT模块包括了运算单元、读写地址单元、旋转因子单元以及控制单元，并且在FPGA中进行了硬件实现，并在matlab环境下对结果进行了验证。

Because it is more superior than that of the binary scale FSK and OOK that the binary scale moves the looks key and accuses of the system in resisting noise performance and channel communication frequency band utilization ratio etc., widely used in digital communication.

二进制移相键控方式是受键控的载波相位按基带脉冲而改变的一种数字调制方式。由于二进制移相键控系统在抗噪声性能及信道通信频带利用率等方面比二进制FSK及OOK的优越，因而被广泛应用于数字通信中。

Because it is more superior than that of thebinary scale FSK and OOK that the binary scale moves the looks keyand accuses of the system in resisting noise performance andchannel communication frequency band utilization ratio etc., widelyused in digital communication.

二进制移相键控方式是受键控的载波相位按基带脉冲而改变的一种数字调制方式。由于二进制移相键控系统在抗噪声性能及信道通信频带利用率等方面比二进制FSK及OOK的优越，因而被广泛应用于数字通信中。

In order to improve the transmission quality and reliability of the digital communication system, channel coding is proposed.

详细说明：为了改善数字通信系统的传输质量，提高数字通信系统传输的可靠性引入信道编码。

Radio channel modeling and parameter estimating is important to design and research of the mobile communication system.

无线信道的参数估计和信道建模对数字移动无线通信系统的研发具有重要意义。

According to the system specification of DRM given by ETSI, the channel coding scheme applied to the system is a set of combination schemes of the multilevel coding and modulation.

根据欧洲电信标准化委员会提供的数字调幅广播系统说明书可知，该系统采用的信道编码方案是一套基于删除卷积码的多级编码和调制的组合方案，它机制灵活，可以针对不同的数据通道和不同的信道条件选择不同码率的分量码和星座图。

Digital signal transmission in the wireless channel, due to the various conditions of access, such as...

数字信号在无线信道中传输时，由于受到各种信道条件的影响，如多经径、衰落、干扰和噪声，接收信号不可避免地会发生错误。

In a more elevated definition, a bearer channel is 64,000 bits per second full duplex. It's the basic building block of the digital signaling hierarchy.

更为崇高的定义是，承载信道是64Kbps全双工信道，是数字信令结构中的基本组成部分。

When the digitalsignal carries on the long distance transmission, the high frequencycomponent weaken increases along with the distance increases, theelectric cable median line also advances to the betweenelectromagnetic radiation along with the frequency intensifies, thusthe clipped wave transmitting range and the transmission quality,simultaneously in the channel often also exists separates the directcurrent electric capacity and the coupling transformer, they cannottransmit the direct component and have a bigger weaken to the lowfrequency component, therefore high frequency and low frequency arepartial regarding the common channel is limited.

当数字信号进行长距离传输时，高频分量的衰减随距离的增大而增大，电缆中线对之间的电磁辐射也随着频率的增高而加剧，从而限制信号的传输距离和传输质量，同时信道中往往还存在隔直流电容和耦合变压器，他们不能传输直流分量及对低频分量有较大的衰减，因此对于一般信道高频和低频部分均是受限的。

In BRI, you get two bearer B-channels at 64 kilobits per second and a data D-channel at 16 kilobits per second.

BRI和 PRI（初级速率接口 BRI中，有两个64 Kbps承载 B 信道和一个16 Kbps 数字D信道。

This brought fixed cost, but it also is meant at the same time use a source to won't make you singlehanded assume a problem.

这带来了一定的成本，但它同时也意味着使用开源不会让你独力承担问题。

He gained a small fortune in real estate.

他在房地产上发了一笔小财。