DTMB地面数字电视技术在电视直播中的应用

介绍了中国地面数字电视标准DTMB在电视直播中的应用。DTMB电视直播系统由摄像机挂接式发射机、接收机、车载转发式发射机等几种设备组成。介绍了DTMB电视直播系统的卫星转发、车载转发和移动转发等3种应用方式,给出了湖南电视台在长沙市的应用实例。     

Phase Noise Correction Based on TPS Symbols for the Chinese DTTB System

In orthogonal frequency division multiplexing (OFDM) system, phase noise (PHN) from oscillator can severely reduce the performance by causing: common phase error (CPE) and inter-carrier interference (ICI). The impact of PHN on received signal can be characterized by the circular convolution of the transmitted signal and the discrete Fourier transform (DFT) of PHN signal in frequency domain. Digital television/terrestrial multimedia broadcasting (DTMB), announced as the Chinese digital television terrestrial broadcasting (DTTB) standard, adopted the time-domain synchronous OFDM system (TDS-OFDM) system which has 36 continuous transmission parameter signaling (TPS) symbols in frequency domain which be used for PHN suppression. Based on a linearized parametric model for PHN, least squared (LS) estimation and fast Fourier transform (FFT) approaching method for PHN correction are proposed in this paper. The effects of the PHN on channel estimation in both TDS-OFDM system and conventional cyclic prefix OFDM (CP-OFDM) are also investigated. Simulations show that the proposed algorithm can effectively reduce the PHN and improve the symbol error rata (SER) of TDS-OFDM systems over both additive white Gaussian noise (AWGN) and broadcasting multipath channel. In practice, the FFT-approaching method can be applied to the DTMB receiver-chip design directly with low implementation cost.      

DTMB系统的单频网接收性能预测

给出了一种基于信道容量分析预测DTMB多载波工作模式和单频网环境中接收信噪比门限的方法,并由实验室测试结果证实了该方法的准确性。根据这一方法,可以快速、准确地估计出单频网覆盖重叠区内的人工多径对接收信号性能的影响。     

Novel synchronization for TDS-OFDM-based digital television terrestrial broadcast systems

As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency-division multiplexing (OFDM) is extensively used in modern digital television terrestrial broadcasting (DTTB) systems to support high performance bandwidth-efficient multimedia services. In this paper, novel synchronization schemes, including timing, frequency offset estimation, and phase error tracking, are proposed for the time domain synchronous OFDM (TDS-OFDM) based DTTB systems. Simulations under different channel situations verify the efficiency of the proposed schemes.     

一种新的地面数字多媒体/电视广播传输系统

针对传输信道线性时变的宽带传输信道特性，设计了一种时域同步正交频分复用（简称TDS－OFDM）的多载波调制方式。这种调制方式既适用于具有多径干扰和多普勒频移的地面数字电视广播传输信道，也适用于其它宽带数字传输系统。为了进一步提高传输效率，提出的地面数字多媒体／电视广播DMB－T传输系统还采用了最新的纠错编码和交织编码技术，在额定的8MHz带宽中，净载数据传输率可达32．511Mbps。     

基于DTMB信号的无源探测定位实验

介绍了数字地面多媒体广播( DTMB)信号帧结构,根据录取的DTMB信号的实际数据开展实验研究,分析、验证了DTMB信号的特性,评估了DTMB信号作为非合作照射源的无源探测定位系统的目标探测性能,通过实验数据的研究验证了DTMB信号模糊函数副峰抑制的效果以及无源探测定位目标探测结果。     

认知电力物联网电视频谱感知方法

基于认知无线电(CR)技术的电力物联网(IOTIPS)通过频谱感知实现对空闲授权频段的接入,可以有效提高频谱利用率,由于电力物联网的通信环境复杂,载波频偏无法避免,提出一种适用于电视频段授权用户数字地面多媒体广播(DT-MB)的复合相关检测算法,可以在大载波频偏条件下保持对DTMB信号稳定的检测性能,提升了通信网络的可靠性.同时基于复合相关检测的协作频谱感知,可以有效降低隐藏终端对感知性能的不利影响,提高认知电力物联网的通信效率.     

DTMB中系统的高精度频率跟踪方法

分析了适用于地面数字电视广播国家标准DTMB系统的频率跟踪方法,在此基础上提出了一种改进的高精度频率跟踪方法--卡尔曼滤波法.在AWGN和典型的DTTB多径信道下的仿真结果和分析表明,该方法同时具备了传统频率跟踪方法中两种不同环路带宽下收敛速度快、频率跟踪抖动小的优点,频率跟踪的精度达到了0.15%.     

数字电视DTTB标准的一种同步设计方案

为了解决数字电视地面广播中信号同步的难题,提出了一种新的正交频分复用的定时同步算法,该算法针对最新出台的中国数字电视地面广播传输系统国家标准的帧结构构思定制.它能根据国标中信号帧前缀PN头的良好自相关特性,无需本地PN序列而直接进行帧同步,基于最大似然估计并加以改进,在此基础上再利用其双向循环前后缀的特性进行频偏校正,效果良好.     

Robust CFO Acquisition in PN‐Padded OFDM Systems

As an alternative to the traditional pilot‐aided orthogonal frequency division multiplexing (OFDM), the time‐domain pseudonoise (PN)‐padded OFDM provides a higher spectral efficiency. However, the carrier frequency offset (CFO) attenuates peaks of the conventional PN correlation output, which limits the CFO estimation range of the OFDM synchronizer. An improved correlation is proposed in this letter to remove the CFO‐induced amplitude attenuation of correlation peaks. For a synchronizer adopting the designed correlator, a larger range of CFO acquisition is obtained through using wider correlation windows with a smaller interval between them. The proposed method of CFO acquisition is verified in a digital terrestrial multimedia broadcast receiver, in which the synchronizer is able to acquire CFOs up to ±320 kHz in the DVB‐T F1 channel. Furthermore, the acquisition range can be expanded in more favorable channels.     

基于导频信号的MIMO-OFDM同步技术

MIMO-OFDM技术将成为第4代移动通信系统的关键技术,因MIMO-OFDM对时间和频率偏移非常敏感,因此MIMO-OFDM同步显得尤为重要。提出了一种新的MIMO-OFDM定时同步和频偏同步技术。以GCL序列为基础设计了一个新的符合MIMO-OFDM同步技术的导频序列,通过对该导频序列进行2次相关得到频率估计,并将所得频率运用到定时同步中,得到更为准确的时间估计。仿真结果表明,在相同的信噪比情况下,该方法可以使得系统的误码率和帧传送误码率相对传统方法得到进一步减小。     

低信噪比下SMCC+系统精确大频偏估计方案

该文基于由电子科技大学提出的作为中国地面数字多媒体电视广播传输标准候选方案之一的SMCC+系统和OFDM系统,提出了一种在低信噪比下利用特殊构造的短PN序列进行快速精确的大范围频率同步的方法。经仿真证明,信噪比在-20 dB范围以上时,该法在AWGN,单抽头瑞利衰落信道和等值双径瑞利衰落信道环境纠正大范围频偏的性能比Tufvesson等人(1999)同类常规算法性能更优,从理论上而言,该算法可以估计1/2带宽范围内的频率偏移,显然,该算法优于常规同类算法。     

地面数字电视小功率多频网覆盖应用实践

针对中国数字电视地面广播需求,通过DTMB技术的覆盖试验,测试结果表明:小功率多频网是地面数字电视覆盖和应用的理想方案.     

Cutoff rate and outage probability performance comparisons between DVB-T and DMB-T systems under mobile multipath channels

As an effective technique for combating multipath fading and for high-bit-rate transmission over wireless channels, orthogonal frequency-division multiplexing (OFDM) is extensively used in modern terrestrial digital television broadcasting systems to support high performance bandwidth-efficient multimedia services. Cutoff rate and outage probability are two important criteria to evaluate the performance of a practical communication system in radio engineering. In this paper, the cutoff rate and outage probability performance are compared between two important terrestrial digital television broadcasting systems, the cyclic prefix OFDM based DVB-T system and the time domain synchronous OFDM based DMB-T system, under different mobile multipath channel conditions. The DVB-T system and the DMB-T system are summarily introduced. The cutoff rate and outage probability expressions are developed, and simulation results are given for both the DVB-T system and the DMB-T system.     

Obtaining Diversity and Coding Gains for Digital Terrestrial Television by Using a Coded Cooperative MIMO Transmission Scheme

Digital terrestrial television is a modern broadcasting technology that has permitted broadcasters to offer television service with excellent image and sound quality. Many countries have been assigned a new digital television standardization process and many studies are underway regarding digital multimedia broadcasting technology. This paper investigates the utilization of a coded cooperative multiple-input and multiple-output (MIMO) transmission scheme in modern digital broadcasting systems to achieve additional transmit diversity and coding gains. The main idea of this work is the implementation of a coded cooperative MIMO scheme based on a low-density parity check code. A coded cooperative transmission can obtain a robust forward error correction. In this way, it is possible to achieve more stable system performance and improved mobility for next generation handheld systems. In order to show the potential for practical implementation, the performance of the proposed method is evaluated on the basis of the Digital Video Broadcasting-Second Generation Terrestrial (DVB-T2) system. The simulation results show that the proposed scheme can be utilized for the development of future DVB broadcasting systems that should support high mobility handheld devices, such as the Digital Video Broadcasting–Next Generation Handheld (DVB–NGH) system.     

An OFDM-based wireless ATM transmission system assisted by acyclically extended PN sequence for future broad-band mobile multimediacommunications

An orthogonal frequency division multiplexing (OFDM)-based wireless asynchronous transfer mode (ATM) transmission system is described that is suitable for the future broad-band mobile multimedia communications. In the proposed system, guard symbols, which are cyclically extended by repeating the information symbols, are inserted before and after serial-to-parallel converted wireless ATM data symbols for OFDM transmission. These symbols are used for both wireless ATM frame synchronization and deciding the discrete Fourier transformation (DFT) start point at the receiver. A cyclically extended pseudorandom noise (PN) sequence is inserted into some of the OFDM transmission subchannels at fixed intervals and used to estimate the phase rotation, frequency offset, and delay characteristics. The proposed system does not use "symbol-by-symbol" guard-interval insertion or removal circuits, as do conventional OFDM systems. With this system, it is easy to estimate the phase rotation, frequency offset, and delay characteristics and to synchronize wireless ATM cells. Computer simulation showed that the bit error rate (BER) performance of the proposed system is better than that of a conventional "symbol-by-symbol" OFDM system     

A Robust and Adaptive Carrier Recovery Method for Chinese DTTB Receiver

This paper presents a robust and adaptive carrier recovery method for Chinese digital terrestrial television broadcasting (DTTB) system in which pilot signal and pseudonoise (PN) sequence are adopted to help carrier recovery. The conventional methods utilize pilot or PN sequence respectively. In this paper, we try to combine the advantage of each method together and propose a well designed state machine to control system state automatically. Moreover, as for using PN sequence, a fine PN tracking state is introduced to ensure the robustness of the proposed method. Software simulations show that the proposed method can provide large acquisition range, short acquisition time and small tracking jitter in severely distorted static and dynamic channels. Lab tests and field trials also prove its good performance in real propagation environments.     

地面数字电视信号与GPS相结合的定位系统

为了解决在城市楼宇间可见GPS卫星常常不足4颗而导致无法定位的问题,通过使用地面数字电视信号,实现了这种恶劣环境下的成功定位.而当GPS卫星数大干4颗时,利用数字地面电视信号可以改善GDOP,提高定位精度.介绍了系统的工作原理,通过计算机软件仿真实现了地面数字电视信号的模拟及单点和多点的移动定位,结果表明通过地面数字电视和GPS结合的定位系统可以提高定位精度,解决CPS卫星不足的问题.     

下一代地面数字电视广播系统关键技术

较全面地介绍了下一代中国地面数字电视广播系统的关键技术,其中包括改进的帧结构、发射分集、先进的信道编码和调制、多业务支持、广播回传信道和时频域定位等。仿真结果表明这些技术的应用使系统性能良好。     

岳家山发射台DTMB地面数字广播电视工程建设

DTMB无线地面数字广播电视技术是我国唯一的地面无线广播电视技术标准规范,通过研究DTMB关键技术及实际应用情况,提高对数字化技术和设备的认识。DTMB是广播电视系统今后发展的趋势,对关键技术特点进行了分析,对设备性能、设计方案和测试情况进行了说明。