线性优先级不等差保护LT码的设计

LT码作为一种无码率的编码,能显著地提高网络数据吞吐量。在不同优先级的网络数据传输中,不等差保护（ UEP）是一种必要的方法。所以,设计一个性能良好的具有不等差错保护功能的LT码有很大的应用价值。文中设计了一类具有线性优先级不等差保护特性的LT码（ UEP-LT）。也就是说,对数据层的保护水平是线性分布的。提出的UEP-LT码能以极低的译码开销恢复大多数高优先级的数据。同时,这种UEP-LT码在合理的译码开销下具有比等差保护（ EEP）低的误码率,更好地满足了多媒体传输中对不等差错保护的要求。     

基于Punctured卷积码的UEP方案在FMT系统中的应用

论文将信道编码与多载波调制——滤波多音(FMT,filtered multitone)调制技术相结合,并应用到图像的传输中,通过采用调整Punctured卷积码不同的码率实现图像传输的不等错误保护(UnequalErrorProtection),增加了系统的可靠性,又提高系统传输效率,满足在具有不等错误保护要求的无线环境下对传输图像质量的要求。     

Energy-Constrained Distortion Reduction Optimization for Wavelet-Based Coded Image Transmission in Wireless Sensor Networks

Image transmissions in Wireless Multimedia Sensor Networks (WMSNs) are often energy constrained. They also have requirement on distortion minimization, which may be achieved through Unequal Error Protection (UEP) based communication approaches. In related literature with regard to wireless multimedia transmissions, significantly different importance levels between image-pixel-position information and image-pixel-value information have not been fully exploited by existing UEP schemes. In this paper, we propose an innovative image-pixel-position information based resource allocation scheme to optimize image transmission quality with strict energy budget constraint for image applications in WMSNs, and it works by exploring these uniquely different importance levels among image data streams. Network resources are optimally allocated cross PHY, MAC and APP layers regarding inter-segment dependency, and energy efficiency is assured while the image transmission quality is optimized. Simulation results have demonstrated the effectiveness of the proposed approach in achieving the optimal image quality and energy efficiency. The performance gain in terms of distortion reduction is especially prominent with strict energy budget constraints and lower image compression ratios.      

基于SPECK和Turbo码的鲁棒图像传输

针对信源与信道编码各自的特点,提出了一种基于SPECK（set partitioned embedded block coder）算法和Turbo码相结合的信源信道联合编码方案.由于图像经SPECK算法编码后的数据流对信道噪声非常敏感,所以可采用此方案来提高图像对信道错误的鲁棒性.该方案通过SPECK算法来产生具有不同容错性的子流,信道编码采用删余Turbo码,用不同码率的信道编码来对这些子流进行非平等保护,以改善数据流抗信道差错的整体性能.这种方案充分利用了信源编码后的数据流的特性,从而使误码率与码长达到了一个较好的平衡.实验结果表明,该方案不仅能够在较高的压缩比下,使解码图像具有较高的峰值信噪比,并且由于Turbo码的优异性能,使得图像在较低信噪比条件下进行传输仍具有较强的鲁棒性.     

利用不对等保护提高JPEG2000图像鲁棒性的研究

论文提出了一种新的对JPEG2000图像进行不对等保护的算法,综合考虑了质量层和小波变换子带两种因素,较单纯考虑质量层因素的不对等保护方法,该方案对数据流中的重要数据和次要数据进行了更为明确的划分,经过实验对比证明,该方案的保护效果优于单纯以质量层为划分依据的UEP方案。     

LDPC码在小波压缩图像传输中的应用

LDPC码是一种具有低复杂度,强纠错能力的信道编码结构,SPECK算法是嵌入式小波图像压缩编码中性能较好的一种。本文充分考虑SPECK算法和改进LDPC码的特性,提出了根据信源编码后数据在重建时的重要程度进行不等纠错保护的信源信道联合编码方案。实验表明,该方案有利于压缩图像在噪声信道上的可靠传输,提高系统整体纠错性能。     

An optimal high capacity reversible data hiding scheme using move to front coding for LZW codes

Reversible Data hiding techniques reduce transmission cost as secret data is embedded into a cover image without increasing its size in such a way that at the receiving end, both secret data and the cover image can be extracted and recovered, respectively, to their original form. To further reduce the transmission cost, the secret data can be embedded in the compression codes by some popular reversible data hiding schemes. One of the popular and important reversible data hiding method is high- performance data-hiding Lempel–Ziv–Welch (HPDH-LZW) scheme which hides the secret data in LZW codes. In this paper, the HPDH-LZW scheme is modified in order to increase its hiding capacity and compression ratio. First, the proposed work modifies the Move to Front (MTF) encoding technique to hide the secret data and also to increase the similarity among the element of the cover media. Then, LZW encoding technique is applied on the resultant cover data to obtain LZW codes, which are used to hide further secret data. Experimental results show that the proposed scheme has significantly increased the data hiding capacity and have good embedding and extraction speed in comparison to other state of the art schemes.

     

基于JPEG2000和WIPCLDPC的联合信源信道编码

提出了一种联合信源信道编码(JSCC)方案。首先,构造了一种具有重量递增奇偶校验矩阵的非规则LDPC码(WIPC-LDPC),实现非规则LDPC(Irregular LDPC)码比特节点按列重递增的顺序排列。然后,针对JPEG2000码流分层结构的特点,把不同质量层的JPEG2000码流成功地映射到WIPC-LDPC不同度数的比特节点上,以达到对不同重要级别码流的不等错误保护(UEP),从而达到优化重建图像质量和视觉效果的目的。仿真结果表明,与采用随机构造校验矩阵的非规则LDPC码进行等错误保护(EEP),以及采用RCPC、RS码进行不等错误保护的JPEG2000码流相比,JSCC方案提高了重建图像的PSNR,改善了重建图像的主观视觉效果。     

LDPC码的不等差错保护策略在SVC中的应用

在分析信源信道联合编码的基础上,提出了一种使用LDPC码对SVC比特流进行不等差错保护的策略,能够使端到端的视频序列失真最小化。该不等差错保护策略根据各帧对重建图像的贡献量大小为其进行合理的比特分配,并对每一帧的各质量层实施最佳的非均衡差错保护。实验结果表明,与基于拉格朗日的优化方法相比,该方法更为简单,重建视频的峰值信噪比（PSNR）性能也有明显改进。     

基于不同等差错保护和动态子载波分配技术的图象传输系统性能研究

充分考虑小波变换后的图象码流、Turbo码以及多载波系统的特性,提出了一种新颖的基于不同等差错保护和动态子载波分配技术的图象传输系统.对图象码流中重要性不同的信息比特,进行不同码率的Turbo码,并在不同信道状态的子载波上传输,对于重要信息采用低码率Turbo编码,并为其选择高信噪比的子载波进行数据传输.这种联合信源信道编码方案以及动态子载波分配技术能够有效的保护图象码流的重要信息,提高了图象码流传输过程中的抗误码性能,改善了静态图象在噪声信道中传输的效果.     

Two-Dimensional Channel Coding Scheme for MCTF-Based Scalable Video Coding

The motion-compensated temporal filtering (MCTF)-based scalable video coding (SVC) provides a full scalability including spatial, temporal and signal-to-noise ratio (SNR) scalability with fine granularity, each of which may result in different visual effect. This paper addresses a novel approach of two-dimensional unequal error protection (2D UEP) for the scalable video with a combined temporal and quality (SNR) scalability over packet-erasure channel. The bit-stream is divided into scalable subbitstreams based on the structure of MCTF. Each subbitstream is further divided into several quality layers. Unequal quantities of bits are allocated to protect different layers to obtain acceptable quality video with smooth degradation under different transmission error conditions. Experimental results are presented to show the advantage of the proposed 2D UEP scheme over the traditional one-dimensional unequal error protection (1D UEP) scheme. Comparing the proposed method with the 1D UEP scheme on SNR layers, our method gives up to 0.81-dB improvement for some video sequences     

多级编码调制在图像传输保护中的应用

该文提出了一种应用于Rayleigh衰落信道下图像传输系统中的两级不等错误保护(UnequalErrorProtection,UEP)方案。方案采用了多级编码调制(MultilevelCodes,MLC)技术,通过对重要数据提供最高的传输保护,恢复图像无论在视觉效果上还是在其峰峰值(PeakSignaltoNoiseRatio,PSNR)性能上都获得了明显的提高。     

Robust transmission of scalable video stream using modified LT codes

LT codes are convenient and popular kind of rateless codes that could easily tolerate different patterns of loss in erasure channels. In this paper an LT code with unequal packet protection (UPP) property is proposed. The proposed code could provide unequal packet recovery to any importance-sorted data packets. Simulation results indicate the enhanced performance of the suggested scheme and its ability to increase the probability of early decoding of more important parts of data rather than the rest. Also it is shown that the proposed scheme could provide comparable bit error rates in comparison to the one of the well known previous methods. The code with modified encoding graph has been utilized for transmitting of the scalable data-partitioned video stream. Simulation results also illustrate the performance of the suggested approach in early delivery of the most important parts of a video sequence.     

基于小波SPIHT的联合信源信道编码新方法

提出了一种传输小波SPIHT编码图像的联合信源信道编码方法，该方法针对SPIHT编码码流重要性的不同而进行不同程度的保护，并利用无线信道的时变特性自适应地调整信源和信道编码速率，从而在不增加额外带宽的前提下有效地提高了系统的性能和可靠性，在瑞利信道和GE信道下的仿真表明本方法与前文献中提出的EEP方法以及UEP方法相比，在信道条件恶劣的情况下，能够明显提高恢复图像的质量，该方案尤其适用于放大范围内的信噪比波动信道。     

基于部分信息的SLT-LT联合码防窃听方案设计

近年来, 信息的安全传输备受人们关注, 现有的物理层安全技术从信息论的角度出发, 将物理层安全编码与传输信道的动态物理特性进行结合, 实现信息的保密传输。作为一种纠删码, LT(Luby transform)码由于其编码随机性、码率不固定等特性,使得窃听者不能直接从泄露的编码符号中得到有用信息, 只要合法用户在窃听者之前接收到足够数量的编码符号, 便可实现信息的安全传输。而作为一种转移 LT(Shifted LT, SLT)码, SLT 码能高效恢复信息的同时具有更小的译码开销。因此, 我们将 SLT码应用于 Wyner 降阶窃听信道模型进行研究, 提出一种基于部分信息转移的 SLT-LT 联合码防窃听方案, 信源利用接收者已知的部分信息对度分布进行调整, 并对信源符号进行 SLT-LT 码级联编码。由于窃听信道是合法信道的降阶信道, 因此外在的窃听者截获到的消息符号是合法接收者的降阶版本, 在相同时间内, 合法接收者能够收到更多消息符号, 随着编解码过程的不断进行, 合法接收者的优势不断累积, 能够优先完成解码, 而度分布的调整以及级联编码方案使得编码符号的平均度进一步增大,窃听者难以完成解码, 进一步降低了窃听者译出率; 之后, 对所提方案的编解码性能以及安全性进行理论分析, 并通过实验仿真进行验证, 仿真结果表明, 与其他防窃听 LT 方案相比, 本文所提方案仅增加少量的译码开销但具有更好的安全性能。     

Transmission of multimedia contents in opportunistic networks with social selfish nodes

To share multimedia content and provide reliable communication in an intermittently connected environment, most of the existing transmission schemes of opportunistic networks are taking a class of store-carry-forward schemes to improve the delivery. However, they do not take the social selfish nodes into consideration. To deal with the unpredictability in connections and uncooperative behaviors in the nodes, this paper proposes a transmission scheme to help the social selfish nodes to forward messages for other nodes. In the proposed scheme, priority is given to a message according to the cooperation degree, a cache management strategy is applied, and a delivery probability is calculated to guide nodes to select the better nodes as their relays. Simulation experiments show that the proposed transmission scheme protocol is effective and outperforms the existing transmission schemes.     

无线网络抗干扰攻击的自适应无速率通信

针对干扰攻击干扰信号解码、降低通信性能的问题,提出一种具备抗干扰攻击能力的自适应无速率通信机制。它将原始报文拆分为多个编码分片并分别传输,从而降低干扰攻击的影响并充分利用非连续的可用间隙。通过自适应调整分片的长度,在干扰攻击频繁时减少长度以获得更好的鲁棒性,在攻击概率较低时增大长度以提高效率。实验结果表明,当干扰攻击严重时,与直接通信相比,新机制的吞吐量平均提高50%以上,稳定性提高一个数量级。因此,自适应无速率通信可有效抵御干扰攻击并获得较高的通信效率。     

Scalable Video Multicast Using Expanding Window Fountain Codes

Fountain codes were introduced as an efficient and universal forward error correction (FEC) solution for data multicast over lossy packet networks. They have recently been proposed for large scale multimedia content delivery in practical multimedia distribution systems. However, standard fountain codes, such as LT or Raptor codes, are not designed to meet unequal error protection (UEP) requirements typical in real-time scalable video multicast applications. In this paper, we propose recently introduced UEP expanding window fountain (EWF) codes as a flexible and efficient solution for real-time scalable video multicast. We demonstrate that the design flexibility and UEP performance make EWF codes ideally suited for this scenario, i.e., EWF codes offer a number of design parameters to be ldquotunedrdquo at the server side to meet the different reception criteria of heterogeneous receivers. The performance analysis using both analytical results and simulation experiments of H.264 scalable video coding (SVC) multicast to heterogeneous receiver classes confirms the flexibility and efficiency of the proposed EWF-based FEC solution.     

新型信道自适应编码协作体制

针对传统编码协作体制在信道条件动态变化的移动场景中存在较严重的性能损失问题,提出一种码率兼容低密度奇偶校验(LDPC)码与混合自动重传请求(HARQ)协议相结合的新型自适应编码协作体制.假设信道状态信息在每次传输时发生变化,通过不等长增量冗余的自动重传,协作节点与目的节点处的等效码率随信道条件变化而获得自适应非线性调整.推导所提体制的中断概率与吞吐量等系统性能表达式,并给出理论分析及仿真结果.实验结果表明,在适当的兼容码率设计下,所提体制与传统体制和等长传输体制相比较可有效降低系统中断概率,提高系统的吞吐量,改善移动环境下协作通信系统的传输可靠性.     

基于不等错误保护的LDPC编码*

非规则LDPC码具有不等错误保护特性,但随机编码过程使这一特性很难得以充分利用。首先回顾了LDPC码的有效编码,然后在此基础上提出了一种应用于不等错误保护的线性复杂度编码方法。仿真结果表明,采用这种编码方法可以提高系统的整体性能。