Terrestrial DVB (DVB-T): A Broadcast Technology for Stationary Portable and Mobile Use

Digital video broadcasting-terrestrial (DVB-T) is the name of the terrestrial transmission system which was developed by the DVB Project. DVB-T is in operation in many countries around the world. This paper analyzes the features of the system. It describes its capabilities with a special emphasis on mobile reception and looks at the introduction of DVB-T in Germany using the launch of DVB-T in this country as a case study. In order to analyze how an MPEG transport stream at the input of a DVB-T modulator is turned into a DVB-T signal, we consider the channel coding and modulation used. Then we look at various aspects of the system performance. The next section deals with mobile reception. Network planning issues, antenna diversity concepts for mobile receivers, and handover procedures will be considered. Finally, the introduction of DVB-T in Germany is presented as a case study. In contrast to various other countries Germany decided to offer DVB-T as a means of providing the "anywhere TV" experience. This implies that DVB-T signals can be received with mobile and portable receivers. In regions with DVB-T coverage analogue terrestrial TV services were discontinued just a few months after the launch of DVB-T.     

DVB-T/H and T-DMB: Physical Layer Performance Comparison in Fast Mobile Channels

Terrestrial or Handheld Digital Video Broadcasting (DVB-T/H) and Terrestrial Digital Multimedia Broadcasting (T-DMB) are two popular broadcasting standards that enable digital television transmissions to handheld receivers. This paper presents a comprehensive performance comparison between the physical layers of DVB-T/H and T-DMB when employed for mobile communications. By exploiting a recently proposed fast simulation model, we assess the BER of the two coded OFDM systems in several realistic scenarios, taking into account Rayleigh and Rice channels, different mobile speeds, inner and outer channel coding, channel estimation, and one or two receive antennas. Our comparison shows that the DVB-T/H physical layer performance highly depends on the delay spread of the channel, whereas T-DMB is less sensitive to the frequency selectivity of the channel. As a result, DVB-T/H yields better performance than T-DMB in typical Rayleigh channels with significant delay spread. On the contrary, at high SNR, T-DMB outperforms DVB-T/H in Rice channels with low delay spread. As a side result, we show the performance improvement of DVB-H produced by MPE-FEC at the data link layer.      

Parallel structures for joint channel estimation and data detectionover fading channels

Joint data and channel estimation for mobile communication receivers can be realized by employing a Viterbi detector along with channel estimators which estimate the channel impulse response. The behavior of the channel estimator has a strong impact on the overall error rate performance of the receiver. Kalman filtering is an optimum channel estimation technique which can lead to significant improvement in the receiver bit error rate (BER) performance. However, a Kalman filter is a complex algorithm and is sensitive to roundoff errors. Square-root implementation methods are required for robustness against numerical errors. Real-time computation of the Kalman estimator in a mobile communication receiver calls for parallel and pipelined structures to take advantage of the inherent parallelism in the algorithm. In this paper different implementation methods are considered for measurement update and time update equations of the Kalman filter. The unit-lower-triangular-diagonal (LD) correction algorithm is used for the time update equations, and systolic array structures are proposed for its implementation. For the overall implementation of joint data and channel estimation, parallel structures are proposed to perform both the Viterbi algorithm and channel estimation. Simulation results show the numerical stability of different implementation techniques and the number of bits required in the digital computations with different estimators     

DVB-T在移动接收中的问题与对策

阐述了移动接收环境给接收机带来的载噪比损耗情况,对影响DVB-T接收机移动接收性能的因素进行了分析,介绍了提高DVB-T接收机移动接收性能的天线分集技术.     

基于导频的OFDM信道估计方法及分析

对OFDM系统中基于导频的信道估值器进行了比较分析,分析了DVB-T系统中导频的分布,在DVB-T系统基础上结合最大似然准则和最小均方误差准则,提出了信道估计的方法,并在Reyleigh信道模型下,运用Matlab实现仿真.     

DSP based OFDM demodulator and equalizer for professional DVB-Treceivers

This work treats the design of base-band processing subsystems for professional DVB-T receivers using 1600 MIPS, fixed point DSPs. We show the results about the implementation of OFDM demodulation, channel estimation and equalization functional blocks, for the 2k/8k modes. The adoption of general purpose DSPs provides a great flexibility in the development of different configurations of the receiver. Furthermore it enables the feasibility of adaptive equalization schemes, where the quality of the channel estimation varies according to both channel characteristics and speed of the channel variations. The 16/32 bit fixed point architecture leads to a very low implementation loss, and a careful optimization of the pipeline architecture of the processor allows the receiver to obtain short processing delays. The flexibility of the software approach along with the obtained performance make the proposed implementation very interesting in professional and high-end receivers for interactive, multimedia applications of DVB-T     

A new method for predicting the channel estimate influence onperformance of TDMA mobile radio systems

Receivers for time division multiple access mobile radio systems usually consist of two functional blocks: A channel estimator and an equalizer. We present a new method for predicting the channel estimate influence on performance of such receivers operating over frequency selective time-varying Rayleigh fading channels. The method can be applied to optimize system parameters. It is shown that global receiver performance can be analytically expressed in terms of the performance characteristics of two blocks considered disjointly, i.e. the equalizer operating over a perfectly known channel and the channel estimator operating over a time-varying channel. The analysis leads to expressions of the error probabilities in a form that can conveniently be used in numerical work. The results obtained from Monte Carlo evaluation agree well with the analytical evaluation of the error probability derived from the proposed method with the benefit of the low complexity and rapidity for the latter     

Channel estimation joint DOAs and time delay correlation in TD‐SCDMA mobile radio systems

An improved channel estimation technique based on the Steiner low‐cost channel estimator is proposed, which is widely used in TD‐SCDMA (Time Division‐Synchronous Code Division Multiple Access) cellular mobile radio systems. TD‐SCDMA is also known as third‐generation mobile systems where adaptive antennas are employed. As additive noise has a great adverse effect on the performance of the Steiner estimator, the proposed method employs time‐correlated post‐processing with a threshold filter to reduce channel noise and compensate channel variations. Furthermore, channel estimation combining direction‐of‐arrivals (DOAs) is performed, which can reduce channel interferences without adding computational complexity, for the information of DOAs has been obtained by the inherent adaptive antenna system. The performance of the improved channel estimator is compared with conventional channel estimation approaches, and numerical results show that the new approach can lead to considerable performance enhancement even in high‐speed vehicle propagation environments. Copyright © 2008 John Wiley & Sons, Ltd.     

DVB系统通用外码解码器的FPGA实现

介绍采用流水线结构的信道外码解码器的FPGA硬件设计和实现,它不仅可应用在地面数字电视广播(DVB-T),也可应用在卫星数字电视广播(DVB-S)和有线数字电视广播(DVB-C)接收端.     

Coupled estimators for equalization of fast-fading mobile channels

This letter presents a new method for identification of fast-fading mobile channels (for which combinations of vehicle speed and carrier frequency give rise to significant fading). Our new algorithm estimates both the channel statistics and the time-varying channel impulse response on-line. Simulation studies demonstrate the performance of the new estimator which couples an augmented Kalman filter with a recursive least squares algorithm     

Next generation of broadcast multimedia services to mobile receivers in urban environments

This paper analyses the possibility of receiving high data rate multimedia services in the non-stationary urban mobile scenario using the digital video broadcast standard DVB-T2. The work focuses on the complex urban mobile environment and presents a comparison between the different configuration parameters and the data rates associated to different video services. The study is based on the experience operating an experimental DVB-T2 network in urban environments, where portable and vehicular reception scenarios have been tested. The results show the system performance and the feasible video quality. The paper explores the coverage for various video services, including HDTV and 3DTV options, and proposes some scenarios for the deployment of broadcasting networks transmitting multimedia services to mobile receivers.     

Mobile broadcasting of DVB-T signals

Utilising the DVB-T specification fully will allow broadcasters choose from different modulation formats including QPSK for transmission of MPEG-2 signals over difficult media. Very rugged signals with excellent power and echo performance can be selected with DVB-T modems for contribution circuits. This paper details preliminary results of the transmission of a 6 Mbit/sec MPEG-2 signal from a mobile vehicle to a main station on an upper adjacent channel to existing PAL I broadcasts. It shows that it is possible to use DVB-T signals for contributions from mobile transmitters without signal degradation     

利用频谱特性的速度自适应信道估计方法

本文利用信道在移动环境下频谱带限和对称的特征,提出一种新的对移动速度自适应的信道估计方法。该方法通过寻找频谱自相关的峰值来确定频域滤波器的长度。相对传统速度自适应方法,该方法不需要估计多普勒频率或移动速度,降低了系统实现的复杂度;也不需要信道的长时统计量或信噪比信息,实时性较高。信号在频域的处理必然会有频谱泄漏问题,传统方法滤除噪声的同时也去掉了部分信号,对此本文同时还提出一种恢复泄漏的频域信号的方法,使估计性能有所提高。仿真结果显示,从步行到高速移动的环境下,本文提出的信道估计方法的均方误差(MSE)都保持在较低的水平,具有良好的对速度自适应的估计性能。     

Filtre correcteur de phase pour égaliseurs sous-optimaux

We propose a receiver structure intended for high bit rate transmissions. In order to ensure a good compromise between performance and complexity, the receiver is composed of a transversal phase- corrective filter followed by an equaliser, which takes only partially the channel impulse response into account. We propose a non-iterative technique to adjust the filter tap coefficients, based on the cepstral properties of a minimum phase response. The performance of the filter is evaluated and shown by simulating a transmission system including a multipath mobile radio channel, the filter and a dfse equaliser (decision feedback sequence estimator).     

Adaptive channel estimation and dedicated pilot power adjustmentbased on the fading-rate measurement for a pilot-aided CDMA system

Adaptive channel estimation (ACE) and dedicated pilot power adjustment based on the fading-rate measurement is investigated for the pilot-aided direct-sequence (DS) code division multiple access (CDMA) system. A novel adaptive channel estimator is presented, which makes use of an optimum integral duration or selects the optimum finite-impulse response (FIR) filter coefficients based on the fading-rate measurement. Dynamic adjustment of the dedicated pilot power is further proposed for the purpose of increasing the system capacity, based on the fact that the power of the dedicated pilot channel (DPCH) can be reduced when the mobile station moves slowly. Theoretical analysis and computer simulation results show that significant performance improvement can be achieved by using the proposed adaptive channel estimator and the dynamic pilot power adjustment method     

OFDM系统中的自适应信道估计

分析了现有的基于导频的OFDM信道估计技术,提出了一种低复杂度的自适应信道估计方法,并给出了最大时延扩展的实时估计方法,最后通过计算机仿真,给出了多径信道下MSE曲线,以及在DVB-T系统中的BER仿真曲线,验证了其可靠性和良好的性能。     

TDS-OFDM系统的设计

介绍了TDS-OFDM系统的调制编码方式和接收端实现技术.与欧洲DVB-T循环前缀OFDM的性能对比中,TDS-OFDM在地面电视广播等领域中表现出显著的优势.     

宽带CDMA中一种新的自适应信道估计方法

在衰落信道中进行相干解调必须知道瞬时的信道参数，但由于信道是时变的，所以信道估计器的频率响应和带宽应该是由衰落信道的统计特性和系统的信干比决定。利用瞬时信道估计的自相关函数，本文提出了信道估计的一种新的自适应算法。在平坦瑞利信道中的计算机仿真表明本方法在3G标准支持的所有多普勒频率范围内都能获得良好的均方误差性能。     

A comparative investigation on channel estimation algorithms for OFDM in mobile communications

A comparative investigation on various channel estimation algorithms for OFDM system in the mobile communication environment is presented and analyzed in terms of computational complexity, mean square error, and bit error rate in this paper. As a result, Wiener filter estimation shows the best error performance. Concerning the computational complexity as well as the performance, however, the piecewise linear estimator is considered as a proper choice when the reference signal spacing is relatively narrow. And the cubic-spline estimator is a good alternative to the Wiener filter estimation if the reference signal spacing is wider than the coherent bandwidth of transmission channel.     

Efficient Non-Pilot-Aided Channel Length Estimation for Digital Broadcasting Receivers

Channel estimation and equalization techniques are crucial for the ubiquitous broadcasting systems. Conventional receivers for most broadcasting or wireless standards preset the channel length to the maximal expected duration of the channel impulse response for the adopted channel estimation and equalization algorithms. The excessive channel length often significantly increases the implementational complexity of the wireless receivers and leads to the redundant information which would induce the additional estimation errors. Moreover, such a scheme does not allow the dynamic memory allocation for variable channel lengths. This could further increase the power consumption and reduce the battery life of a mobile device. The knowledge of the actual channel length would, in principle, help the system designers decrease the complexity of the channel estimators using maximum likelihood (ML) and minimum-mean-square-error (MMSE) algorithms. In this paper, we address this important channel length estimation problem and propose a novel autocorrelation-based algorithm to estimate the channel length without the need of pilots or training sequence. The associated threshold for the channel length estimation depends on the sample size, the signal-to-noise ratio and the leading/last channel coefficients. In addition, we provide the mean-square analysis on the effectiveness of the proposed non-pilot-aided channel length estimator through Monte Carlo simulations.