Distributed Source Coding in the Presence of Byzantine Sensors

The distributed source coding problem is considered when the sensors, or encoders, are under Byzantine attack; that is, an unknown group of sensors have been reprogrammed by a malicious intruder to undermine the reconstruction at the fusion center. Three different forms of the problem are considered. The first is a variable-rate setup, in which the decoder adaptively chooses the rates at which the sensors transmit. An explicit characterization of the variable-rate achievable sum rates is given for any number of sensors and any groups of traitors. The converse is proved constructively by letting the traitors simulate a fake distribution and report the generated values as the true ones. This fake distribution is chosen so that the decoder cannot determine which sensors are traitors while maximizing the required rate to decode every value. Achievability is proved using a scheme in which the decoder receives small packets of information from a sensor until its message can be decoded, before moving on to the next sensor. The sensors use randomization to choose from a set of coding functions, which makes it probabilistically impossible for the traitors to cause the decoder to make an error. Two forms of the fixed-rate problem are considered, one with deterministic coding and one with randomized coding. The achievable rate regions are given for both these problems, and it is shown that lower rates can be achieved with randomized coding.     

Efficient Set Operations in the Presence of Malicious Adversaries

We revisit the problem of constructing efficient secure two-party protocols for the problems of set intersection and set union, focusing on the model of malicious parties. Our main results are constant-round protocols that exhibit linear communication and a (practically) linear number of exponentiations with simulation-based security. At the heart of these constructions is a technique based on a combination of a perfectly hiding commitment and an oblivious pseudorandom function evaluation protocol. Our protocols readily transform into protocols that are UC secure, and we discuss how to perform these transformations.     

Computationally Secure Pattern Matching in the Presence of Malicious Adversaries

We propose a protocol for the problem of secure two-party pattern matching, where Alice holds a text t∈{0,1}^? of length n, while Bob has a pattern p∈{0,1}^? of length m. The goal is for Bob to (only) learn where his pattern occurs in Alice’s text, while Alice learns nothing. Private pattern matching is an important problem that has many applications in the area of DNA search, computational biology and more. Our construction guarantees full simulation in the presence of malicious, polynomial-time adversaries (assuming the hardness of DDH assumption) and exhibits computation and communication costs of O(n+m) group elements in a constant round complexity. This improves over previous work by Gennaro et al. (Public Key Cryptography, pp. 145–160, 2010) whose solution requires overhead of O(nm) group elements and exponentiations in O(m) rounds. In addition to the above, we propose a collection of protocols for important variations of the secure pattern matching problem that are significantly more efficient than the current state of art solutions: First, we deal with secure pattern matching with wildcards. In this variant the pattern may contain wildcards that match both 0 and 1. Our protocol requires O(n+m) communication and O(1) rounds using O(nm) computation. Then we treat secure approximate pattern matching. In this variant the matches may be approximated, i.e., have Hamming distance less than some threshold, τ. Our protocol requires O(nτ) communication in O(1) rounds using O(nm) computation. Third, we have secure pattern matching with hidden pattern length. Here, the length, m, of Bob’s pattern remains a secret. Our protocol requires O(n+M) communication in O(1) rounds using O(n+M) computation, where M is an upper bound on m. Finally, we have secure pattern matching with hidden text length. Finally, in this variant the length, n, of Alice’s text remains a secret. Our protocol requires O(N+m) communication in O(1) rounds using O(N+m) computation, where N is an upper bound on n.     

Distributed Detection in the Presence of Byzantine Attacks

Distributed detection in the presence of cooperative (Byzantine) attack is considered. It is assumed that a fraction of the monitoring sensors are compromised by an adversary, and these compromised (Byzantine) sensors are reprogrammed to transmit fictitious observations aimed at confusing the decision maker at the fusion center. For detection under binary hypotheses with quantized sensor observations, the optimal attacking distributions for Byzantine sensors that minimize the detection error exponent are obtained using a ldquowater-fillingrdquo procedure. The smallest error exponent, as a function of the Byzantine sensor population, characterizes the power of attack. Also obtained is the minimum fraction of Byzantine sensors that destroys the consistency of detection at the fusion center. The case when multiple measurements are made at the remote nodes is also considered, and it is shown that the detection performance scales with the number of sensors differently from the number of observations at each sensor.     

基于多视点视频编码的差错控制算法

 多视点视频编码(Multiview Video Coding,MVC)利用运动估计和视差估计取得了较好的编码性能,但在易错的网络环境下传输MVC视频码流,将导致差错在视点内与视点间进行扩散.针对多视点视频的编码特性,提出了一种端到端的失真度估计模型,并将此模型与率失真优化相结合得到一种基于联合信源信道的编码模式选择算法.实验结果表明该方法能够在易错网络环境下有效的提高多视点视频的传输效率.     

无线视频传输中FEC与WZ联合抗误码算法研究

无线视频编码的低抗误性、无线信道带宽的有限性、无线视频业务的高需求决定了高鲁棒性的抗误算法必将成为无线视频通信的核心问题之一.基于FEC与WZ (Wyner-Ziv)两抗误工具的在不同误码率下抗误互补特性,提出了FEC与WZ联合抗误码方案.实验表明:该方案有效地综合了两者优点,提升了平均PSNR.     

SSIM-based Error Resilient Video Coding Over Packet-Switched Networks

The visual quality is a critical factor in prediction video coding over packet-switched networks. However, the traditional MSE-based error resilient video coding cannot correlate well with the perceptual characteristics of the human visual system (HVS). This paper proposes a structural similarity (SSIM) based error resilient video coding scheme to improve the visual quality of compressed videos over packet-switched networks. In the proposed scheme, a SSIM-based end-to-end distortion model is developed to estimate the perceptual distortion due to quantization, error concealment, and error propagation. Based on this model, an adaptive mode selection strategy is presented to enhance the communication robustness of compressed videos. Experiments show that the proposed scheme significantly improves the visual quality for H.264/AVC video coding over packet-switched networks.     

视频流传输中的差错复原视频编码技术

视频压缩技术在采用预测技术、变换编码技术和可变长熵编码技术以减少冗余信息的同时,也降低了视频流的容错能力.传输信道中的差错,不仅严重损害了视频服务质量,甚至会使通信系统崩溃,因此,在有错信道上进行视频传输,差错复原视频编码技术就显得尤为重要.对差错复原视频编码技术进行了概括和总结,首先指出在视频传输过程中存在的由于传输错误而引发的比特流同步丢失及错误蔓延问题,然后研究了解决这些问题的差错复原视频编码方法,最后指出:可伸缩视频编码和多描述视频编码是差错复原视频编码的发展方向;多描述编码同多路径技术相结合,能显著提高压缩视频信号的错误恢复能力和传输信道的性能.     

Optimizing Motion Compensated Prediction for Error Resilient Video Coding

This paper is concerned with optimization of the motion compensated prediction framework to improve the error resilience of video coding for transmission over lossy networks. First, accurate end-to-end distortion estimation is employed to optimize both motion estimation and prediction within an overall rate-distortion framework. Low complexity practical variants are proposed: a method to approximate the optimal motion via simple distortion and source coding rate models, and a source-channel prediction method that uses the expected decoder reference frame for prediction. Second, reference frame generation is revisited as a problem of filter design to optimize the error resilience versus coding efficiency tradeoff. The special cases of leaky prediction and weighted prediction (i.e., finite impulse response filtering), are analyzed. A novel reference frame generation approach, called ?generalized source-channel prediction?, is proposed, which involves infinite impulse response filtering. Experimental results show significant performance gains and substantiate the effectiveness of the proposed encoder optimization approaches.     

无线视频传输的容错编码研究

基于无线视频监控传输技术进行无线信道视频图像传输的过程中,经常面临数据传输错误、带宽变化、网络拥塞导致的视频数据丢失问题,严重影响了图像质量。Joint Video Team(JVT)of ISO/IECMPEG and ITU-T VCEG提出了可伸缩视频编码(SVC),可实现视频空间、时间和图像质量的完全伸缩,本文结合率失真优化算法将可伸缩编码作为容错工具,引入了不同层数据,根据B-D代价函数决定自动重传机制,降低了视频数据丢失对图像质量的影响。仿真结果表明,该方法大大提高了视频码流的抗误码能力和传输的鲁棒性。     

Detecting the Presence of Speech Using ADPCM Coding

When speech is coded using a differential pulse-code modulation system with an adaptive quantizer, the digital code words exhibit considerable variation among all quantization levels during both voiced and unvoiced speech intervals. However, because of limits on the range of step sizes, during silent intervals the code words vary only slightly among the smallest quantization steps. Based on this principle, a simple algorithm for locating the beginning and end of a speech utterance has been developed. This algorithm has been tested in computer simulations and has been constructed with standard integrated circuit technology.     

无线自组织网络的网络编码技术

网络编码作为一种新的技术在宽带无线自组织网络中有很好的应用,通过网络编码,中间节点可以将接收信息进行编码并发送出去,提高了网络吞吐量和健壮性。为不对现有网络的软硬件设备和相应的协议做很大的修改,可以选择在高层实现网络编码。无线传感器网络、无线格状网（Mesh）等无线自组织网络都可以使用网络编码技术显著提高多跳链路的传输性能。目前网络编码的研究热点集中在网络编码节点选取方案、网络编码算法的设计、网络编码复杂度分析、网络编码的性能分析、网络编码与系统安全性分析、网络编码在无线分布式网络中的应用等方面。     

新一代无线通信网中的网络编码

介绍了网络编码的基本原理,比较了网络编码的构造方式及其优缺点,在高斯信道以及多址信道中描述了基于传统网络编码和物理层网络编码的联合编译码方案.最后,通过分析联合编码的优缺点评述了基于MIMO和协作分集技术的网络编码方案,并结合LTE-A中将出现的新问题讨论了网络编码进一步的研究方向.     

无线通信中的网络编码技术

网络编码是一种提高网络吞吐量和性能的新技术,预计将成为未来网络的一项关键技术.本文概述了无线网络中的网络编码技术,无线网络被认为是网络编码最可能得到应用的领域之一,网络编码技术使无线媒质的广播属性可以得到充分利用,无线网络和传感器网络为网络编码的应用提供了巨大的机会.本文结合不同无线场景介绍了网络编码的各种编码方法,包括传统的网络编码、物理层网络编码、模拟网络编码以及复数域网络编码,并对未来发展给出了展望.     

Rate-Distortion Optimized Motion-Compensated Prediction for Packet Loss Resilient Video Coding

A rate-distortion optimized motion-compensated prediction method for robust video coding is proposed. Contrasting methods from the conventional literature, the proposed approach uses the expected reconstructed distortion after transmission, instead of the displaced frame difference in motion estimation. Initially, the end-to-end reconstructed distortion is estimated through a recursive per-pixel estimation algorithm. Then the total bit rate for motion-compensated encoding is predicted using a suitable rate distortion model. The results are fed into the Lagrangian optimization at the encoder to perform motion estimation. Here, the encoder automatically finds an optimized motion compensated prediction by estimating the best tradeoff between coding efficiency and end-to-end distortion. Finally, rate-distortion optimization is applied again to estimate the macroblock mode. This process uses previously selected optimized motion vectors and their corresponding reference frames. It also considers intraprediction. Extensive computer simulations in lossy channel environments were conducted to assess the performance of the proposed method. Selected results for both single and multiple reference frames settings are described. A comparative evaluation using other conventional techniques from the literature was also conducted. Furthermore, the effects of mismatches between the actual channel packet loss rate and the one assumed at the encoder side have been evaluated and reported in this paper     

面向移动立体电视的高容错编码方案设计

提出了一种与H.264标准相兼容、且容错性强的立体视频编码方案.该方案采用H.264标准中的场编码模式,顶场存放左视点图像,底场存放右视点图像,利用灵活宏块排序(FMO)技术,将左右视点图像交织成棋盘型后实现立体编码.实验结果表明本方法既具有良好的率失真性能,又能提高传输的容错性.     

网络编码在网络安全中的应用

网络编码的思想在1999年由杨伟豪和张珍首次提出,由Ahlswede等人进一步发展和扩充,安全的网络编码也随即提出。蔡亍和杨伟豪首先针对单信源有向无圈网络给出了安全网络编码的定义和模型,其他研究者也各自提出了不同的安全模型,如J P Vilela提出了轻量级安全的网络编码,K Bhattad提出了弱安全的网络编码等,另外还有抗拜占庭攻击的网络编码。网络编码理论亦在网络纠错中得到了应用,杨伟豪和蔡宁推广了经典纠错码,引入了网络纠错码,杨胜豪在杨伟豪和蔡亍研究的基础上,研究了线性网络编码的重量性质。     

联合信道网络编码研究综述

网络编码技术可以提高网络吞吐量和传输性能,均衡网络负载。在无线传感器网络中,应用网络编码和信道编码联合编码技术可以降低节点数据处理复杂度,大幅提升系统整体性能。基于传统网络编码模型,在节点中加入数据调制功能,可以实现网络编码和信道编码的联合编码,信道编码则采用各方面性能较好的Turbo码和LDPC码。结果表明,在10-4误码率下,联合编码方案的信噪比相比于传统编码方案有1.5 dB的节省。