Watermarking system based on quantization index modulation （QIM） is increasingly popular in high payload applications,but it is inherently fragile against amplitude scaling attacks.In order to resist desynchronizati...Watermarking system based on quantization index modulation （QIM） is increasingly popular in high payload applications,but it is inherently fragile against amplitude scaling attacks.In order to resist desynchronization attacks of QIM digital watermarking,a low density parity check （LDPC） code-aided QIM watermarking algorithm is proposed,and the performance of QIM watermarking system can be improved by incorporating LDPC code with message passing estimation/detection framework.Using the theory of iterative estimation and decoding,the watermark signal is decoded by the proposed algorithm through iterative estimation of amplitude scaling parameters and decoding of watermark.The performance of the proposed algorithm is closer to the dirty paper Shannon limit than that of repetition code aided algorithm when the algorithm is attacked by the additive white Gaussian noise.For constant amplitude scaling attacks,the proposed algorithm can obtain the accurate estimation of amplitude scaling parameters.The simulation result shows that the algorithm can obtain similar performance compared to the algorithm without desynchronization.展开更多
提出了一种无数模转换器(Digital to Analog Converter,DAC)的全数字跳频(Frequency Hopping,FH)系统。通过Δ∑调制(delta-sigma modulation,DSM),数字域中的FH模拟信号可以被转换为比特序列,然后通过I/O端口传输。与传统的模拟载波跳...提出了一种无数模转换器(Digital to Analog Converter,DAC)的全数字跳频(Frequency Hopping,FH)系统。通过Δ∑调制(delta-sigma modulation,DSM),数字域中的FH模拟信号可以被转换为比特序列,然后通过I/O端口传输。与传统的模拟载波跳频系统相比,该系统具有较低的复杂度和较高的频率选择灵活性。与现有的数字基带跳频系统相比,全数字FH系统更容易在数字信号处理(Digital Signal Processing,DSP)中实现DSM,而不是利用高采样率DAC。实验通过正交幅度调制(Quadrature Amplitude Modulation,QAM),在20 km光纤和1 m无线链路上成功实现了2.4 GHz、3.5 GHz、3.51 GHz和5.5 GHz的跳频信号的发送和接收。展开更多
基金National Natural Science Foundation of China(No.61272432)Qingdao Science and Technology Development Plan(No.12-1-4-6-(10)-jch)
文摘Watermarking system based on quantization index modulation （QIM） is increasingly popular in high payload applications,but it is inherently fragile against amplitude scaling attacks.In order to resist desynchronization attacks of QIM digital watermarking,a low density parity check （LDPC） code-aided QIM watermarking algorithm is proposed,and the performance of QIM watermarking system can be improved by incorporating LDPC code with message passing estimation/detection framework.Using the theory of iterative estimation and decoding,the watermark signal is decoded by the proposed algorithm through iterative estimation of amplitude scaling parameters and decoding of watermark.The performance of the proposed algorithm is closer to the dirty paper Shannon limit than that of repetition code aided algorithm when the algorithm is attacked by the additive white Gaussian noise.For constant amplitude scaling attacks,the proposed algorithm can obtain the accurate estimation of amplitude scaling parameters.The simulation result shows that the algorithm can obtain similar performance compared to the algorithm without desynchronization.
文摘对广播电视无线数字化系统中应用到的多项核心技术进行了深入剖析和探讨。首先,分析调制技术,介绍了调频(Frequency Modulation,FM)/调幅(Amplitude Modulation,AM)调制的原理,并阐述了数字调制技术如正交幅度调制(Quadrature Amplitude Modulation,QAM)、正交频分多址(Orthogonal Frequency Division Multiple Access,OFDMA)等的工作机制与优势。其次,探讨数字电视广播的传输技术,包括地面数字电视传输标准和卫星传输技术。再次,重点分析音视频编码、信道编码等信号处理技术,说明它们在压缩数据、抗干扰方面的作用。最后,介绍多频网(Multi Frequency Network,MFN)和单频网(Single Frequency Network,SFN)两种网络配置方式的不同。通过应用这些技术,我国已构建起规模庞大、技术先进的广播电视无线发射网络,为人们获取音、视频信息提供保障。
