降低TDS-OFDM信号峰均功率比的方法

针对具有大量子载波的时域同步正交频分复用(TDS-OFDM)系统,提出了应用星座图扩展降低TDS-OFDM系统的峰均功率比(PAPR),同时增加保护间隔的能量以增大信号的平均功率,使得TDS-OFDM的PAPR进一步降低.最后给出了相应的仿真结果.     

一种适用于宽带无线移动通信系统下行链路的TDS-OFDM发送方法

本文将主要介绍宽带无线城域网系统(BRadio)中下行链路的TDS-OFDM(时域同步正交频分复用)发送方法.TDS-OFDM是针对宽带无线传输信道设计的一种多载波调制方式,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,也适用于其他宽带数字传输系统.TDS-OFDM技术已经在地面数字多媒体/电视广播(DMB-T)传输系统中得到了应用,在此基础上,本文结合对已有的宽带无线移动通信系统的研究,对宽带无线移动通信系统的帧结构、OFDM符号组成、子载波分配方案进行了改进,使TDS-OFDM能够适用于宽带无线移动通信系统,满足其需求.     

TDS-OFDM系统中PN序列的研究

文中介绍了数字电视地面广播传输系统中的TDS-OFDM技术，阐述了PN序列在TDS-OFDM系统中可以作为OFDM块的保护间隔，还可以被用作系统同步和信道估计等。仿真结果表明，TDS-OFDM系统在多径条件下具有满意的性能。     

存在非线性失真和相位噪声影响的CP-OFDM与 TDS-OFDM数字电视地面广播传输系统的性能分析

本文概述了数字电视地面广播传输系统中存在的非线性失真和相位噪声影响因素;用模型统一表达了CP-OFDM和TDS-OFDM的OFDM复包络信号;从理论上分析了循环前缀和不断插入的导频训练序列会导致基于CP-OFDM的数字电视地面广播传输系统比在同等的外界条件下的基于TDS-OFDM的数字电视地面广播传输系统具有更低的有效数据符号信噪比水平;详细推导了在非线性失真和相位噪声共同影响下的CP-OFDM系统和TDS-OFDM系统的有效数据符号的统一信噪比表达式;定义并统一表达了在非线性失真和相位噪声共同影响下的CP-OFDM系统和TDS-OFDM系统的性能恶化指标;从理论和计算机仿真两方面比较分析了受到各种不同非线性失真和相位噪声影响的基于CP-OFDM和基于TDS-OFDM的两种不同数字电视地面广播传输系统的性能恶化程度.     

一种TDS-OFDM系统的载波恢复算法

提出一种新的适用于TDS-OFDM系统的频偏估计算法,利用PN序列的时域循环特性进行预频偏调整,然后用变步长扫频进行大频偏的估计,定时同步之后再利用PN的时域循环特性进行细偏估计.给出了推导过程与仿真结果,并与各种算法进行了比较.结果表明,在高斯和多径信道下此算法均能快速纠正大范围的频偏.     

非基2的FFT的实现原理及在数字电视地面传输系统中的应用

在宽带OFDM系统的实现中FFT处理器是一个关键部分,本文介绍任意非基2点的FFT的实现原理,及在数字电视地面传输系统TDS-OFDM中的实际应用.FFT的基本思想就是将一维的运算,通过地址映射转化为多维运算,从而达到减少运算次数,减轻设计复杂程度的目的.非基2的FFT地址映射方法多种,本文将洋细介绍一种适用于FPGA的将PFA,WDFTA 及Cooley-Tukey FFT算法结合实现非基2的FFT的方法.     

基于压缩感知的窄带干扰重构与消除

提出了一种基于压缩感知的TDS-OFDM系统窄带干扰重构方法,通过利用相邻TDS-OFDM帧头的差分采样建立压缩感知模型,能够在不依赖信道估计及在高频谱效率的条件下,精确恢复窄带干扰信号并予以消除,显著提升传输系统传输鲁棒性。     

基于2倍过采样的TDS-OFDM定时恢复算法

提出了一种基于2倍过采样的TDS-OFDM定时恢复算法,与基于4倍过采样的算法相比,降低了接收机的工作频率和复杂度。在多种信道下的仿真结果表明,提出的算法与基于4倍过采样的算法性能相当,可直接应用于TDS-OFDM系统中。本算法已成功应用于电力线通信系统中,实现了在20 MHz带宽的电力线信道上传输上百兆的数据率。     

一种低复杂度的信道估计与均衡模块实现

提出了一种基于TDS-OFDM技术的信道估计与均衡模块的设计方法,并在FPGA上实现,可应用于高速电力线通信中.根据模块特点,分别从整体架构和局部单元进行了优化设计.通过仿真和硬件实测表明.本模块具有很低的硬件复杂度和良好的性能.     

空频发射分集技术在TDS-OFDM中的实现

为提高在衰落信道中数字电视地面广播(DTTB)系统的传输性能,设计了在时域同步正交频分复用(TDS-OFDM)系统中发射分集技术的应用方案,并在FPGA上实现了TDS-OFDM传输系统双天线发射分集的硬件系统。为了能够快速且实时处理,发射端和接收端硬件实现均采用了流水线结构,并对硬件中的核心模块进行了多次复用以节省硬件资源。仿真结果和硬件测试表明,这种发射分集应用方案能够有效提高系统的接收性能,增加信号传输的可靠性。     

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.      

Effects of nonlinear distortion and imperfect parameters estimation on the performance of OFDM-based DTTB 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, such as the cyclic prefix OFDM (CP-OFDM) based DVB-T DTTB systems and the time domain synchronous OFDM (TDS-OFDM) based DMB-T DTTB systems, to support high performance bandwidth-efficient multimedia services. OFDM-based DTTB systems are very sensitive to the nonlinear distortion at the transmitter and the imperfect parameters estimation at the receiver. In this paper, the combined effects of nonlinear distortion and imperfect parameters estimation on the performance of the OFDM-based DTTB systems are investigated, a closed form of symbol error probability of the OFDM-based DTTB systems with nonlinear distortion and imperfect parameters estimation is derived. Theoretical results show closely matching with those obtained by simulations for both the CP-OFDM based DVB-T DTTB systems and the TDS-OFDM based DMB-T DTTB systems.     

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.     

A general SFN structure with transmit diversity for TDS-OFDM system

In the digital television terrestrial broadcasting, the Single Frequency Network (SFN) has much advantage. SFN can serve an arbitrary large area with the same information broadcasted at the same frequency, resulting in the potential diversity gain. To improve the transmission performance of the Time Domain Synchronous-Orthogonal Frequency Division Multiplexing (TDS-OFDM) system in SFN, a general SFN structure with transmit diversity is introduced, theoretically analyzed and computer simulated. The proposed SFN structure is flexible to set up. Simulations show that this method can greatly improve the reliability of the signal transmission over the frequency selective fading channels and is suitable for the TDS-OFDM system in SFN.     

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。     

A Simplified Equalization Method for Dual PN-Sequence Padding TDS-OFDM Systems

Time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) modulation scheme can improve the spectrum efficiency over the traditional Cyclic Prefix (CP) OFDM technology at the cost of computational efforts due to the iterative padding subtraction (IPS) at the receiver to mitigate the inter symbol interference caused by the multipath propagation. In this paper, a simplified equalization scheme is presented for the dual PN-sequence padding (DPNP) TDS-OFDM systems. Although the length of the padded PN sequence needed is double compared to what needed by the IPS, leading to slight decrease of the spectrum efficiency, this method can save about 90% computational effort in practice compared with that of the IPS algorithm. It also outperforms IPS method under the time-varying fading channel in terms of symbol error rate and maximum Doppler frequency, verified by the computer simulation.