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.     

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.     

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.     

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。     

一种TDS-OFDM系统的信道估计方法

提出了一种适用于时域同步正交频分复用(TDS-OFDM)系统的信道估计方法.首先详细介绍了算法流程,然后通过计算机仿真,证明了该方法在各种复杂的无线广播信道下可以完成信道估计,进而完成数据均衡.     

TDS-OFDM系统中同步方法的研究

讨论了一种在TDS-OFDM系统中利用PN保护间隔进行系统同步的方法,用本地生成的PN序列和接收到的时域数据进行相关,找到相关峰位置,利用相关峰位置完成定时同步,同时采用二次相关完成载波频率同步.通过仿真证明本同步方案具有较好的同步性能.     

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PN序列的OFDM时频同步技术研究

本文基于中国数字电视地面广播DTMB标准多载波模式,设计出基于PN序列的TDS-OFDM系统的时频同步算法。所设计的同步算法通过MATLAB在AWGN信道模型和BrazilA信道模型下进行仿真,并通过均方误差(MSE)表征算法估计性能。仿真结果及分析表明所设计算法的可行性。     

一种应用于数字电视地面广播的OFDM多载波调制方法

介绍了数字多媒体电视广播协议（DMB-T）中的信号帧结构，该结构引入PN码帧头用于时域同步。从理论上分析了时域同步正交频分复用多载波调制（TDS-OFDM）的参数选取策略。重点说明了子载波数量确定为3780的选择步骤。在这种信号结构下，TDS-OFDM信号的通带带宽为7.56MHz，既满足了电视带宽的要求，又满足了奈奎斯特采样定律。最后简要介绍了实现3780点快速傅立叶变换（FFT）的算法。其计算复杂度和容量复杂度都与标准的4096点FFT算法相当。     

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.     

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.      

基于OFDM的LDPC误码测试系统设计

通过比较国内外几种LDPC误码平台测试系统,设计了一种基于OFDM的用于测试LDPC解码误码性能的窄带系统,采用了时域同步正交频分复用调制方式,具有抵抗多径干扰和多普勒频移的能力.该系统用FPGA予以实现,不仅可用于实验室测试,也可用于测试真实多径环境下的误码性能,还能作为通用系统用于其他信道纠错码的解码误码测试.     

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.      

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。     

Low-Complexity Equalization for TDS-OFDM Systems Over Doubly Selective Channels

Time variation of a multipath channel leads to interchannel interference (ICI) in orthogonal frequency-division multiplexing (OFDM) systems. It results in the performance degradation, therefore, limits the achievable throughput. Some methods have been proposed to suppress ICI, unfortunately, they are either computationally complex or at the price of spectral efficiency. In this paper, a low-complexity equalization method for time-domain synchronous OFDM (TDS-OFDM) systems is proposed under the assumption that the channel impulse response (CIR) varies in a linear fashion within a block period. The rationale behind our method is to use a finite power series expansion for the inverse of the equalization matrix. This method provides a desired tradeoff between the performance and the processing complexity. Theoretical analysis and simulation results demonstrate that the proposed method can effectively mitigate ICI caused by the channel variations with low computational complexity.