数字电视地面广播COFDM系统传输方案的研究

随着数字化时代的到来，数字电视也相应地得到了快速地发展。本文首先简要介绍了数字电视地面广播、接着在分析正交频分复用（OFDM）技术基本原理的基础上，进一步探讨了以欧洲数字电视地面广播（DVB-T）为基础的COFDM传输方案原理，分析了该方宁所具有的特点。OFDM/COFDM已经在数字音频广播中实现，并准备应用于地面数字电视和HDTV广播中。最后还对我国数字地面电视的发展做了分析与展望。     

基于FPGA的DVB-T COFDM调制模块的设计

研究了DVB-T标准中的COFDM编码调制模块,阐述了COFDM编码调制的基本原理,并以FPGA为硬件平台进行了半实物仿真。最后结合DVB-T标准分析了COFDM适用于地面数字电视广播的特性。     

BDB-T系统中频域同步的FPGA实现

通过对欧洲数字视频地面广播(DVB-T)COFDM传输系统的研究分析，提出一种新的宽带数字电视地面广播BDB-T同步部分的解决方案，设计出基于FPGA的频域同步硬件电路，经BDB-T功能样机在实际无线环境中的传输测试，证明了所给方案的易实现性及良好性能。     

HDTV中的信道内插与均衡技术

以欧洲数字视频地面广播（DVB-T）系统的调制方案为基础，以正交频分复用OFDM为核心技术，通过对基于导频信号的信道估计方法中各种信道内插算法的仿真对比分析，总结出适用于COFDM系统，易于FPGA实现的信道估计与均衡方法。     

Paxson公司已在提交给FCC的申请书上签字

Paxson通讯公司已宣布:公司已在Sinclair广播集团公司提交FCC的申请书上签字,申请书要求FCC应许可广播机构采用COFDM技术来发送数字电视信号。作为广播电视台的最大经营者,Paxson公司同意向FCC提交申请,这里代表了72个企业的意向,在这72个企业中,有的归Paxson公司所有,有的Paxson公司在那里有股份。如果FCC同意修改数字调制的现有法规,那么广播机构就能够采用COFDM或8VSB技术来发送自己的数字信号,而FCC目前只支持8VSB技术。Paxson公司同其它15家广播集团一起支持COFDM申请,这里代表了所有支持这一高级数字电视标准的商业…     

地面数字电视上行传输MAC层协议研究

分析了在数字电视地面广播使用COFDM技术实行单频网、蜂窝化和基站化的基础上,进一步实现双向化的结构和接入方式,就上行信道S＿CDMA多址接入方式设计了Internet接入的MAC层协议-竞争/冲突解决机制,分析表明该协议简单有效,易于实现。     

DVB-T名词一览

地面数字电视的传播条件复杂，容易受到地形、高楼遮挡及海面反向波的影响。同时还有模拟和数字同频信号、邻频信号及地面脉冲等的干扰。传送质量、可靠性及覆盖范围受到限制，特别是实现车载移动高质量接收的难度更大。由于数字电视地面广播的传输环境恶劣，频谱资源有限。应用需求分散，其制式目前在各国仍有争议。目前，国际上地面数字电视广播传输系统有单载波和多载波COFDM两种传输方式，美国的ATSC方案采用的是8VSB单载波调制方式；欧洲的DVB方案采用的是COFDM多载波调制方式；     

电视与广播

TN932006021380COFDM系统在非理想定时同步条件下的信道估计/王勇,葛建华,艾渤(西安电子科技大学综合业务网国家重点实验室)//电子与信息学报.―2005,27(2).―239～242.该文深入研究了数字电视地面无线广播COFDM解调方案中的信道估计与内插技术,针对接收系统前端符号定时同步误     

浅谈数字音频广播DAB

本文简要介绍了数字音频广播DAB的优点,COFDM传输方式等。     

DVB-T解内交织器的FPGA实现

数字电视广播技术是当前研究的热点问题。欧洲的DVB-T标准由于采用COFDM多载波调制方式,在性能上比其余的几种标准优越。本文介绍了DVB-T标准中解交织模块的算法并给出了在FPGA上的实现方式。     

COFDM: an overview

The research and development of OFDM/COFDM for digital television broadcasting has received considerable attention and has made a great deal of progress in Europe. OFDM/COFDM has already been implemented in digital audio broadcasting and is being considered for terrestrial digital television and HDTV broadcasting. The advantages of COFDM claimed by the advocates in Europe have also caught the attention of US broadcasters and generated enthusiasm although a digital modulation technique called 8-VSB has been selected by the FCC Advisory Committee on Advanced Television Service (ACATS) for the final testing. There is considerable debate in the industry over the use of COFDM vs. VSB or QAM for terrestrial HDTV broadcasting. In this paper, the history of research and development on OFDM and COFDM is reviewed. Then, the basic principles, performance and implementation of OFDM and COFDM are examined. Analysis is given to enable the selection of key elements for meeting the constraints of the required applications. Based on the ATV channel model, performance expectation of COFDM under imperfect channel conditions and implementation issues are examined in details     

COFDM系统在非理想定时同步条件下的信道估计

该文深入研究了数字电视地面无线广播COFDM解调方案中的信道估计与内插技术,针对接收系统前端符号定时同步误差对于信道估计性能的影响,提出了两种适用于COFDM梳状导频系统的信道估计解决方案,并给出了其性能和可适用性分析。     

Hardware nonlinearities in digital TV broadcasting using OFDMmodulation

FFT-based coded orthogonal frequency division multiplexing (COFDM) is one of the techniques for digital TV broadcasting over multipath fading channels. A FFT-based OFDM signal is subject to various hardware nonlinearities in both the transmitter and receiver. Hardware nonlinearities not only affect the in-band performance of an FFT-based OFDM system but also may affect the system performance of an adjacent channel signal because of regenerated sidelobes of the transmitted signal. The paper investigates the in-band and out-of-band behaviour of a 64QAM-OFDM system under various nonlinear devices. It is shown that the inherent signal clipping in the IFFT processors with a limited word length reduces the required RF amplifier output backoff (OBO) where adjacent channel interference is the limiting factor. For a 0.25% clipping rate, an additional 2 dB OBO is required for the COFDM signal to achieve the same level of adjacent channel interference as for the single carrier system. The loss in SNR due to signal clipping is negligible in a coded OFDM system     

Transmission techniques for dab by satellite

This study is a comparison between the CDMA and COFDM transmission techniques for digital audio broadcasting. Since broadcasting is used to establish a mobile or fixed link, it is necessary to set up a transmission technique which allows the optimum use of fading and multipath channels, particularly in urban locations. This paper sums up a comparative case study between the two transmission techniques mentioned above. The interest of this paper is to point out the added value brought by these transmission techniques for requirements such as multiple path problems with digital broadcasting with mobiles, frequency mapping and synchronization, capacity of the system, jamming protection capability, BER specifications, signal processing complexity, power control, spectrum efficiency and error correction operations. Finally, this paper tries to bring the appropriate conclusion which leads the OFDM process in Europe.     

COFDM技术及其在DVB-T系统中的应用

COFDM技术是一种多载波数字通信技术。他是较为完备的移动接收和传输技术,可以大大降低每个子载波内的符号间干扰,节省了用于均衡的系统开销。对欧洲数字地面广播标准DVB T中的COFDM(编码的正交频分复用)调制方式进行了研究,阐述了COFDM技术的基本原理,并且介绍了其适合应用于地面数字电视广播系统的主要特性。     

Multi-resolution 64-DAPSK modulation in a hierarchical COFDMtransmission system

Two alternative modulation schemes of 64-QAM (quadrature amplitude modulation) and 64-DAPSK (differential amplitude and phase shift keying) with a coherent and incoherent demodulation have been proposed for digital terrestrial video broadcasting (DTVB) in combination with the coded orthogonal frequency division multiplexing (COFDM) technique (Schafer 1995, and Engels and Rohling 1995). Additionally, a hierarchical transmission system based on a multi-resolution (MR) 64-QAM is described in Engels and Rohling which extends the service area of a TV programme in decoding a stepwise reduced data rate with increasing transmitter distance (graceful degradation). This procedure corresponds to a decreasing picture quality. In this paper MR concepts for the 64-DAPSK are developed. A performance comparison between the hierarchical transmission systems (MR-64-QAM/OFDM and MR-64-DAPSK/OFDM) is described for the uncoded and coded case     

DVB-T: the COFDM-based system for terrestrial television

In early 1996, the European DVB (Digital Video Broadcasting) Project finalised what is now called the `common 2k/8k specification' for terrestrial television transmission. This specification is an important cornerstone of digital video broadcasting in Europe and numerous other countries in the world. Called DVB-T, it is based on the channel-coding algorithms the DVB Project had earlier devised for digital television on cable and satellite. The modulation scheme that is used for DVB-T is OFDM (orthogonal frequency division multiplexing), which when used in conjunction with channel coding is known as COFDM. Two variants are described, one employing 1705 individual carriers in an 8 MHz channel (`2k variant'), the other employing 6817 carriers (`8k variant'). Each individual carrier can be modulated either by QPSK, 16-QAM, 64-QAM or hierarchical modulation     

中波数字AM广播实现方案

提出一种上下兼容的中波数字广播系统方案。该方案的数字基带传输方式为COFDM,与DRM和IBOC相同,射频调制仍采用保留载波的双边带调幅,不需要对现有广播发射机进行改动或更换,接收机可沿用目前中波收音机的包络检波或采用相干解调,实现复杂度低,便于形成规模生产。讨论了该方案实现的关键技术,并给出了发展和应用前景。     

COFDM数字电视广播系统中使用CSI的维特比译码器

介绍比特交织格状编码调制 ＭＱＡＭ的编译码原理,软判决译码中使用信道状态信息（ＣＳＩ）是ＣＯＦＤＭ在频率选择性衰落和干扰下获得优异性能的关键。研究ＣＯＦＤＭ数字ＴＶ广播系统中使用ＣＳＩ的维特比译码器的一种实现方法。