DVB-T2系统信道估计算法的研究

信道估计技术是OFDM宽带无线通信系统中的关键技术之一.提出一个DVB-T2系统新的信道估计算法,根据接收到的导频点的信道响应并进行时域插值的结果,优化DVB-T2系统中不同导频图样下频域插值器的开销和性能,从而达到不同导频图样下频域插值器的开销和性能的最优化.     

DVB-T与地面数字电视国标信道估计算法分析

介绍了DVB-T基于导频的信道估计算法与国标基于PN序列的迭代相关检测信道估计算法,对其进行了估计精度、均衡后的误码率性能、运算量、信道估计对冗余开销的影响等方面的比较,并理论推导出DVB-T基于导频的信道估计方法加入虚拟载波后导致的误差,最后得出国标信道估计具备令人满意性能的结论.     

OFDM系统中联合信道估计的载波同步算法的研究

针对采用正交频分复用（OFDM）调制的欧洲数字电视地面广播系统（DVB—T），详细分析了剩余载波频偏对信道估计的影响，并根据DVB—T特有的信道估计方式提出了与信道估计相结合的频域相位调整和时域补偿两种同步方案，仿真结果表明，在多径信道条件下，这两种同步方案能完全消除剩余载波频偏对信道估计的影响，且具有令人满意的性能。     

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.      

CD3-OFDM: a novel demodulation scheme for fixed and mobilereceivers

This paper describes a novel channel estimation scheme identified as coded decision directed demodulation (CD3) for coherent demodulation of orthogonal frequency division multiplex (OFDM) signals making use of any constellation format [e.g., quaternary phase shift keying (QPSK), 16-quadrature amplitude modulation (QAM), 64-QAM]. The structure of the CD3-OFDM demodulator is described, based on a new channel estimation loop exploiting the error correction capability of a forward error correction (FEC) decoder and frequency and time domain filtering to mitigate the effects of noise and residual errors. In contrast to the conventional coherent OFDM demodulation schemes, CD3-OFDM does not require the transmission of a comb of pilot tones for channel estimation and equalization, therefore yielding a significant improvement in spectrum efficiency (typically between 5-15%). The performance of the system with QPSK modulation is analyzed by computer simulations, on additive white Gaussian noise (AWGN) and frequency selective channels, under static and mobile reception conditions. For convolutional coding rate 1/2, the results indicate that CD3-OFDM allows one to achieve a very fast adaptation to the channel characteristics in a mobile environment (maximum tolerable Doppler shift of about 80 Hz for an OFDM symbol duration of 1 ms, as differential demodulation) and an E_b /N₀ performance similar to coherent demodulation (e.g., E_b/N₀=4.3 dB at bit-error rate (BER)=2·10 ^-4 on the AWGN channel). Therefore, CD3-OFDM can be suitable for digital sound and television broadcasting services over selective radio channels, addressed to fixed and vehicular receivers     

A novel CDD-OFDM scheme with pilot-aided channel estimation

Cyclic delay diversity (CDD) is a low-complexity standard-conformable transmit diversity scheme for coded orthogonal frequency division multiplexing (OFDM) systems. However, it makes channel estimation more challenging due to the increased frequency-selectivity of the equivalent single-input single-ouput channel. In this paper, we propose a novel CDD-OFDM scheme with pilot-aided channel estimation for any number of transmit antennas. By alternating and optimizing the cyclic delay parameter over adjacent OFDM symbols, we design a simple yet efficient channel estimation scheme and illustrate its excellent performance for the DVB-T application.     

Effects of HPA nonlinearity on frequency multiplexed OFDM signals

The paper analyzes the performance of the downlink channel of a multimedia interactive service system which transmits the desired information by the frequency multiplexing of several OFDM signals compliant with the DVB-T standard. The effects of the nonlinear distortions introduced by a high power amplifier on the system performance are evaluated both in terms of the bit error rate (BER) degradation in AWGN channels and of the spectral regrowth. The performance comparison to the case of a single DVB-T signal as well as the benefits of an ideal predistortion is also considered by comparing analytical results to computer simulations     

Turbo码在数字地面电视广播系统中的仿真研究

Turbo码以其优异的纠错性能被应用到许多领域,尝试把先进的Turbo码技术引入到数字地面电视广播系统的信道编码方案中,并利用仿真系统针对译码算法、交织器技术、通信信道等不同的系统参数对改进后的系统的性能影响进行仿真研究。仿真结果表明,引入Turbo码的系统性能优于原DVB-T系统。     

DVB-T中非自适应和自适应信道估计算法的实现

信道估计的精确性对整个DVB-T接收系统的性能提高至关重要.在现有信道估计的算法中,线性估计和多项式估计不适用于环境恶劣的信道;FFT和IFFT估计实现代价太大;盲反卷积估计需要预先知道信道的统计参数,而信道统计参数的获得需要额外的代价;经典Wiener估计不仅需要获得信道的统计参数,而且需要对矩阵进行求逆,这就大大增加了算法的计算量.本文提出了两种信道估计的算法--二维FIR信道估计和二维自适应Wiener信道估计,这两种方法不需要预先知道信道的统计参数信息,不仅减少了运算复杂性,而且在实际中具有很好的性能.     

Pilot Based Channel Estimation in IEEE 802 16a OFDM System

1　Introdution　IEEE 802 16[1] is a specification for fixed broadbandwireless Metropolitan Access Networks (MAN). The stan dard is expected to bring low cost and more bandwidth prod ucts for broadband wireless access in the next years. Thisstandard specifies the physical (PHY) and Medium AccessControl layer (MAC) of the air interface of interoperablepoint to multipoint and optional Mesh topology broadbandwireless access system. The specification enables access todata, …     

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.     

COFDM系统的信道估计算法

本文通过对欧洲数字视频地面广播调制方案的分析,结合计算机仿真和工程应用,深入研究了基于DVB－T标准、适用于编码正交频分复用（COFDM）系统的信道估计算法,Matlab仿真及FPGA电路实现表明该算法具有可靠性高、复杂度低及易于实现的良好性能。     

一种多载波MFSK信道编码方案

目前随着硬件和编码技术的提升,逐渐成熟的多载波技术在通信过程中得到广泛的推广和应用。为了在较严重的多径衰落条件下获取更高的频谱利用效率,采用静态多抽头信道建模的方式对无线信号传播进行模拟。以信道冲击响应数据的误码率作为分析基础,设计了一种引进正交频分复用及多天线技术概念进行改良的多载波MFSK编码方案,并验证了在多径衰落条件下的频谱使用效率及误码率,从而证明了该方案在提高频谱效率方面的可行性。     

基于差分编码的OFDM系统ICI消除方法的研究

在高速移动通信环境下,OFDM 系统在传输过程中出现的多普勒频移和收发两端本地振荡器之间的频率偏差,形成子载波间干扰(ICI)并造成系统性能降低。该文在分析子载波间干扰机制的基础上,从信道估计的角度提出了一种高效的ICI自消除差分编码方案。该方案提高了传统ICI自消除方案频谱利用率。仿真表明,在系统归一化频率偏差大于0.1时,该方案具有4 的信道估计增益,消除了因ICI带来的地板效应。     

Multiple Adaptive Frequency Filtering for OFDM Channel Estimation

In orthogonal frequency division multiplexing (OFDM) systems using pilots, channel estimation is performed on pilots and then interpolated over the time and the frequency axis. As time-interpolated estimates have a different mean square error than pilot estimates we propose the use of multiple adaptive filters for exploiting the frequency correlation of the channel. Each filter operates on a different configuration of pilot and time-interpolated estimates and is adapted independently from the other filters. As a simpler suboptimal solution we consider also the use of a single filter, whose adaptation however takes into account the reliability of the various estimates. Performance results are reported with reference to the DVB-T and DVB-T2 standards showing that the proposed technique performs similar or better than existing approaches at a much lower complexity.      

应用加权高斯模型的非理想稀疏信道估计

在高速通信系统中,由于多径信道通常存在一些小的散射体,使得抽头向量不满足理想的稀疏特性,导致经典的稀疏估计算法存在一定的性能损失。针对上述非理想稀疏特性问题,提出了一种基于酉变换近似消息传递(Unitary Transform Approximate Message Passing,UT-AMP)和加权高斯(Weighting-Gaussian,WG)先验模型的稀疏估计算法。首先,由非理想稀疏信道的构造分析,导出了WG先验模型和参数;其次,利用贝叶斯公式对正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)系统进行因式分解和因子图建模,归纳了在消息传递框架内期望最大化(Expectation Maximization,EM)算法嵌入方式,推导了联合UT-AMP和EM的信道估计算法;最后,建立仿真环境对所提算法进行复杂度分析和数值仿真。仿真结果表明,所提算法能够以同阶复杂度实现信道估计性能和频带利用率的提升,具有很高的应用和推广价值。     

一种适用于DVB-T系统的信道估计算法

提出了一种基于导频的信道估计算法,该算法在最小平方误差(LS)算法的基础上采用两维插值的方法估计出无线信道的频域响应,即在时域上进行线性插值,然后利用最大似然(ML)算法进行频域插值。在地面数字视频广播(DVB-T)系统中的仿真结果表明,该复合算法具有较高的性能。     

WRAN系统中基于自适应内插的信道估计算法

提出了一种基于自适应复系数内插的信道估计算法,改善了无线区域网络（WRAN）系统对抗动态多径时延的能力。WRAN是第一个采用认知无线电技术改善频谱效率的宽带接入标准,系统在下行链路中采用了正交频分复用（OFDM）调制技术,而信道估计技术对于采用相干解调的OFDM系统十分重要。传统的OFDM信道频域响应（CFR）估计算法通常采用实系数频域内插的方式,在对抗WRAN系统长多径时延信道时,不能有效地工作。该文在研究实系数FIR内插变换域响应的基础上,提出了一种复系数内插算法。为了同时适用于短时延信道,提出了一种低复杂度、自适应匹配信道最大多径时延的算法。通过仿真,验证了该算法能够对抗更大的多径时延,提高信道估计的精度,改善系统误码性能。      

一种基于傅里叶变换和信道估计的脉冲噪声消除方法

对受到脉冲噪声干扰和未受到脉冲噪声干扰的DVB-T信号分布进行了统计、分析和比较,在此基础上结合正交频分复用符号的快速傅里叶变换和信道估计,提出了一种脉冲噪声频域消除的实现机制,最后对这种实现机制进行了仿真测试,证明了其有效性.     

0.5-μm CMOS circuits for demodulation and decoding of anOFDM-based digital TV signal conforming to the European DVB-T standard

In the context of digital terrestrial TV based on the DVB-T standard, four 0.5-μm CMOS IC's (IC1-IC4) are presented. IC1 integrates an 8-K fast Fourier transform for orthogonal frequency division multiplexing demodulation, IC2 performs channel estimation/correction, and IC3 is a forward error corrector implementing a Viterbi and a Reed-Solomon decoder. IC4, which is based on a digital signal-processing core, performs the synchronization tasks of the complete receiver. These four chips have been designed and manufactured using a 0.5-μm, 3,3-V, triple-metal CMOS process. Their global complexity is about 500 kgates of standard cells and 1.5 Mbits of memory, which represents a total die area of 435 mm² in 0.5 μm. The total power dissipation is about 3.5 W when working at nominal frequency. More generally, these four IC's constitute the digital front-end part of a global chipset receiver (specified within the European project DVBird), also including an analog front end and a MPEG2 demultiplexer IC