Analysis of an EMST-based path for 3D meshes

For several 3D data applications such as data-hiding or compression, data ordering is a major problem. We need to know how to achieve the same 3D mesh path between the coding and decoding stages. Various algorithms have been proposed in recent years, but we focus on methods based on Euclidean Minimum Spanning Trees (EMST). In this paper, we analyse the sensitivity of the EMST structure to obtain a more robust synchronization. We present a new theoretical analysis and a way to visualize EMST robustness. Moreover, this analysis can be useful in 3D data-hiding in order to detect fragile area and to predict the 3D object robustness during transmission on a noisy channel.     

抗几何攻击的双层隐秘通信体制

本文以特征点为基础,提出了一种新的抗几何变形攻击的双层隐秘通信体制。我们将图像看作双层信道,一层信道嵌入隐秘通信信息,另一层嵌入可用来估计几何形变的几何同步信息。图像本身由其特征点经过Delaunay三角剖分得到一组三角形区域,三角形的中心坐标作为同步信息嵌入到所在三角形区域内,并用CRC校验码和Golay码保护。检测测时分析提取出的同步信息,用最小二乘法估计出几何形变,并对图像进行几何校正,解决失同步问题,提取出隐秘通信信息。实验证明,本隐秘通信体制对平移、旋转、缩 放、剪切等几何攻击有很强的鲁棒性,且本方法可以用于抗几何攻击的MPEG视频信息隐藏系统中。     

A high‐performance robust control method based on the gain and phase information of uncertainty

The well‐known small‐gain and passivity approaches to robust control only make use of either the gain or the phase information of uncertainty in system design. This results in a limitation on the achievable control bandwidth in practical applications. To relax the limitations associated with these approaches, we explore the possibility of utilizing both the gain and the phase information of uncertainty in robust control design. In this paper, the modeling of uncertainty accounting for both gain and phase is discussed first. Then conditions for robust stability and robust performance (sensitivity and bandwidth) are derived respectively. These robustness conditions are described as phase or gain constraints on the nominal system in different frequency bands. Further, it is revealed, both theoretically and via a hard disk drive benchmark, that a much higher robust performance can be achieved by using the gain and phase information of uncertainty. Copyright © 2013 John Wiley & Sons, Ltd.     

一类带边信息的时变数字水印信道容量分析

在对数字水印信道容量分析时,通常假设水印攻击信道的概率分布是完全已知的,但实际中对水印攻击信道的信息在某种意义上是不完整的,如信道估计误差、拉伸和几何攻击等。该文提出了一类带边信息的时变水印信道模型,它包含时变攻击的确定和随机两部分,在对水印信道的概率分布作很少假设条件下,获得了这类水印信道容量的上界和下界,同时也证实了在实际应用中加性高斯噪声信道模型不足以描述水印信道,最后用数值仿真验证了这个结论。     

一种基于人工噪声的MISO相关信道物理层安全方法

现有基于人工噪声的物理层安全方法都假设信道是相互独立的,但是多天线通信系统中存在的信道空间相关性会降低系统安全容量。针对这一问题,设计了一种基于人工噪声的多入单出(MISO)相关信道物理层安全方法。通过合法用户信道参数的协方差矩阵得到发送端的信道相关矩阵,利用该矩阵与合法用户信道参数乘积的零空间作为人工噪声的生成空间,随机生成人工噪声对窃听方实现干扰。仿真结果表明,在存在信道空间相关性的情况下,本方法比现有方法的平均系统安全容量提高了约0.5 bit/s/Hz。     

Robust power allocation algorithm for analog network coding with imperfect CSI

Power allocation promises significant benefits in wireless networks. However, these benefits depend on knowledge of the channel state information （CSI）, which is hardly perfect. Therefore, robust algorithms that take into account such CSI uncertainties play an important role in the design of practical systems. In this paper, we formulate the power allocation problem as the maximum individual outage probability minimization subject to total power consumption for analog network coding （ANC） protocol of a two-way relay system. We show that these problems can be cast as convex optimization problems. Non-robust power allocation algorithm is first developed under the ideal assumption of perfect CSI. Then we introduce robust optimization methodology that accounts for the imperfect CSI. We show that ignoring CSI uncertainties in our designs can lead to drastic performance degradation. On the other hand, the proposed robust power allocation provides significant performance gain over non-robust power allocation and uniform power allocation in terms of overall system outage probability over a wide range of channel estimation errors. This work highlights the importance of the proposed robust algorithm in realistic two-way relaying networks.     

MIMO two-way relay channel with superposition coding and imperfect channel estimation

This paper deals with the superposition coding (SPC) scheme in multiple-input multiple-output two-way relay channels subject to imperfect channel estimation. In this scenario, two multiple antenna terminals, which are unable to communicate directly, exchange information with each other via a multiple antenna relay. We determine the impact of the channel estimation error degradation on the achievable rate region for two main SPC techniques: (a) SPC without channel state information (CSI) at the users, (b) SPC with an imperfect CSI at the users where a waterfilling power allocation is employed. We demonstrate that imperfect CSI significantly improves the achievable rate at low signal-to-noise ratios (SNRs) while it becomes less critical at high SNRs. In addition, a SPC power allocation technique that incorporates the average channel statistics and does not require any instantaneous CSI is also investigated. We show how the available power is split between the two bi-directional (superimposed) data flows in order to maximize the system performance and to support fairness as well as to maximize the achievable sum-rate.     

Mobile Agents in Interaction Spaces

Mobile agent systems are difficult to reason about and implement efficiently and safely. Theoretical work, most notably process calculi, provide solid semantics for mobile systems. However, the theory is often too abstract to match with the requirements of practical implementations. To fill this gap, intermediate models must be proposed. We present in this paper such a model named Interaction Spaces, a metaphor of geometrical spaces in which agents interact through simple transformations. The framework captures high-level distributed semantics, most notably asynchronous, multicast communications on FIFO channels. It also refines and implements the channel passing feature of the pi-calculus, together with the mobility of agent themselves. Above interaction spaces, we propose a full-fledged agent calculus and its associated operational semantics.     

低密度校验码在瑞利衰落信道中的性能分析

低密度校验（LDPC）码具有编码增益高，译码速度快，可并行译码等特点，是当前编码界的一个研究热点，但是目前已有的研究成果都集中在高斯信道上，该文分析和讨论了LDPC码在瑞利衰落信道下的性能，应用联合界技术推导了一个规则友的性能限，并给同了仿真结果，且发现LDPC码在瑞利衰落信道下也具有非常好的性能。     

Partial 3D Shape Retrieval by Reeb Pattern Unfolding

This paper presents a novel approach for fast and efficient partial shape retrieval on a collection of 3D shapes. Each shape is represented by a Reeb graph associated with geometrical signatures. Partial similarity between two shapes is evaluated by computing a variant of their maximum common sub-graph.
By investigating Reeb graph theory, we take advantage of its intrinsic properties at two levels. First, we show that the segmentation of a shape by a Reeb graph provides charts with disk or annulus topology only. This topology control enables the computation of concise and efficient sub-part geometrical signatures based on parameterisation techniques. Secondly, we introduce the notion of Reeb pattern on a Reeb graph along with its structural signature. We show this information discards Reeb graph structural distortion and still depicts the topology of the related sub-parts. The number of combinations to evaluate in the matching process is then dramatically reduced by only considering the combinations of topology equivalent Reeb patterns.
The proposed framework is invariant against rigid transformations and robust against non-rigid transformations and surface noise. It queries the collection in interactive time (from 4 to 30 seconds for the largest queries). It outperforms the competing methods of the SHREC 2007 contest in term of NDCG vector and provides, respectively, a gain of 14.1% and 40.9% on the approaches by Biasotti et al. [ BMSF06 ] and Cornea et al. [ CDS*05 ].
As an application, we present an intelligent modelling-by-example system which enables a novice user to rapidly create new 3D shapes by composing shapes of a collection having similar sub-parts.     

Metadata-based image watermarking for copyright protection

In this paper, we propose a practical application for copyright protection of images with watermarking. The EXIF metadata of images and error-control codes are integrated into our algorithm and corresponding applications. Application for robust watermarking is one of the major branches in digital rights management (DRM) systems and digital forensics. Here, we focus on the copyright protection for images taken by ordinary cameras. By use of robust watermarking, it generally alters selected coefficients of the contents to accomplish the embedding process. Should the received image be in question, the watermark embedded beforehand can be extracted to indicate the copyright owner of such an image. We consider not only the image contents itself, but we also employ the EXIF metadata, which serves as the role of watermark, to be integrated into our scheme to make copyright protection possible. Moreover, for enhancing the performance for copyright protection, channel coding is employed and better protection capability can be expected. Taking the manufacturer, camera model, date and time stamp, and other important information in the EXIF metadata into account, conventional watermarking techniques can be applied to ordinary pictures taken by ourselves, and watermarked images with good quality can be produced. Even when the marked image has been intentionally modified, the original EXIF with selected information can mostly be recovered from the channel decoding process. Simulation results present the effectiveness of such an implementation.     

基于压缩感知的SAR图像鲁棒编码传输

目的 尽管传统的联合信源信道编码方案可以获得高效的压缩性能,但当信道恶化超过信道编码的纠错能力时会导致解码端重构性能的急剧下降;为此利用压缩感知的民主性提出一种鲁棒的SAR图像编码传输方案,且采用了一系列方法提高该方案的率失真性能。方法 考虑到SAR图像丰富的边缘信息,采用具有更强方向表示能力的方向提升小波变换(DLWT)对SAR图像进行稀疏表示,且为消除压缩感知中恢复非稀疏信号时存在的混叠效应,采用了稀疏滤波方法保证大系数的精确恢复,在解码端采用了高效的Bayesian重建算法获得图像的高性能重建。结果 在同等码率下,与传统的联合信源信道编码方案CCSDS-RS相比,本文方案可以实现更加鲁棒的编码传输,当丢包率达到0.05时,本文方案DSFB-CS获得的重建性能明显要高于CCSDS-RS;与基于Bayesian重建算法TSW-CS的传统方案相比,本文方案可提高峰值信噪比(PSNR)3.9 dB。结论 本文方案DSFB-CS 实现了SAR图像的鲁棒传输,随着丢包率的上升,DSFB-CS获得的重建性能缓慢下降,保证了面对不稳定信道时,解码端可以获得相对稳定的重构图像。     

A novel multimodal fusion network based on a joint-coding model for lane line segmentation

There has recently been growing interest in utilizing multimodal sensors to achieve robust lane line segmentation. In this paper, we introduce a novel multimodal fusion architecture from an information theory perspective, and demonstrate its practical utility using Light Detection and Ranging (LiDAR) camera fusion networks. In particular, we develop a multimodal fusion network as a joint coding model, where each single node, layer, and pipeline is represented as a communication channel, and forward propagation equates to information transmission in the channel. This enables us to qualitatively and quantitatively analyze the effect of different fusion approaches. We argue that an optimal fusion architecture is related to essential capacity and allocation based on the source and channel models. To test this multimodal fusion hypothesis, we progressively formulate a series of multimodal models based on our proposed fusion methods and evaluate them on benchmark KITTI and the A2D2 datasets. Our optimal fusion network achieves 85%+ lane line accuracy and 98.7%+ overall accuracy. We conclude that the performance gap with state-of-the-art models demonstrates the potential of our fusion architecture to serve as a new benchmark resource for the multimodal deep learning community.     

Performance limitations for single-input LTI plants controlled over SNR constrained channels with feedback

This paper studies control problems for discrete-time single-input linear time-invariant plants when controlled over a signal-to-noise ratio (SNR) constrained channel. Our focus is on the performance limitations in an architecture that uses channel feedback. We explicitly characterize the interplay between stabilization, optimal performance, and SNR constraints, highlighting the way in which plant dynamical features affect the best achievable performance. We also apply our results to the study of networked control systems where communication takes place over a power constrained erasure channel. In that scenario, we first show that stabilization problems, and problems involving stationary second-order moments, can be dealt with by focusing on a related SNR constrained networked situation. This observation allows one to obtain results valid in the alternative scenario as corollaries of the results obtained when a single SNR constraint is present.     

A robust cardinality-constrained model to address the machine loading problem

Several deterministic models have been proposed in the literature to solve the machine loading problem (MLP), which considers a set of product types to be produced on a set of machines using a set of tool types, and determines the quantity of each product type to be produced at each time period and the corresponding machine tool loading configuration. However, processing times are subject to random increases, which could impair the quality of a deterministic solution. Thus, we propose a robust MLP counterpart, searching for an approach that properly describes the uncertainty set of model parameters and, at the same time, ensures practical application. We exploit the cardinality-constrained approach, which considers a simple uncertainty set where all uncertain parameters belong to an interval, and allows tuning the robustness level by bounding the number of parameters that assume the worst value. The resulting plans provide accurate estimations on the minimum production level that a system achieves even in the worst conditions. The applicability of the robust MLP and the impact of robustness level have been tested on several problem variants, considering single- vs multi-machine and single- vs multi-period MLPs. We also consider the execution of the plans in a set of scenarios to evaluate the practical implications of MLP robustness. Results show the advantages of the robust formulation, in terms of improved feasibility of the plans, identification of the most critical tools and products, and evaluation of the maximum achievable performance in relation to the level of protection. Moreover, low computational times guarantee the applicability of the proposed robust MLP counterpart.     

Cooperative multiple access channels: Achievable rates and optimal resource allocation

We investigate the multiple access channels (MAC) where sources can cooperate via half-duplex relaying and refer to it as cooperative MAC channels (CMAC). Assuming perfect channel state information (CSI) at the transmitters and the receivers, we determine the bounds on the achievable rate region of a Gaussian CMAC channel and an inner bound on the outage capacity region of a fading CMAC channel. Based on superposition modulation, a half-duplex cooperative relay scheme with optimal resource allocation is proposed to achieve the bounds of capacity region. Analytical results and simulation results show that the achievable rate region of a Gaussian CMAC channel is larger than that of a Gaussian MAC channel with direct transmission (DT) schemes. But they have the same achievable sum rate. Moreover, the proposed scheme can provide higher outage capacity region than DT schemes in a fading MAC channel due to the fact that sources can share the resources with each other to reduce outages. Supported partially by the National Natural Science Foundation of China (Grant No. 60672079), the Natural Science Foundation of Jiangsu Province (Grant No. BK2006701), and the Natinoal High-Tech Research & Development Program of China (Grant No. 2007AA01Z267)     

Architectures and coder design for networked control systems

In networked control systems (NCSs) achievable performance is limited by the communication links employed to transmit signals in the loop. In the present work, we characterise LTI coding systems which optimise performance for various NCS architectures. We study NCSs where the communication link is situated between plant output and controller, and NCSs where the communication link is located between controller and actuator. Furthermore, we present a novel NCS architecture, which is based upon the Youla parameterisation. We show that, which of these architectures gives best performance depends, inter alia, upon characteristics of a related non-networked design, plant disturbances and reference signal. A key aspect of our work, resides in the utilisation of fixed signal-to-noise ratio channel models which give rise to parsimonious designs, where channel utilisation is kept low. The results are verified with simulations utilising bit-rate limited channels.     

Energy- and spectral-efficiency of zero-forcing beamforming in massive MIMO systems with imperfect reciprocity calibration: bound and optimization

In a time-division duplex (TDD) system with massive multiple input multiple output (MIMO), channel reciprocity calibration (RC) is generally required in order to cope with the reciprocity mismatch between the uplink and downlink channel state information. Currently, evaluating the achievable spectral efficiency (SE) and energy efficiency (EE) of TDD massive MIMO systems with imperfect RC (IRC) mainly relies on exhausting Monte Carlo simulations and it is infeasible to precisely and concisely quantify the achievable SE and EE with IRC. In this study, a novel method is presented for tightly bounding the achievable SE of massive MIMO systems with zero-forcing beamforming under IRC. On the basis of the analytical results, we demonstrate key insights for practical system design with IRC in three aspects: the scaling rule for interference power, saturation region of the SE, and the bound on the SE loss. Finally, the trade-off between spectral and energy efficiencies in the presence of IRC is determined with algorithms developed to optimize SE (EE) under a constrained EE (SE) value. The loss of optimal total SE and EE due to IRC is also quantified, which shows that the loss of optimal EE is more sensitive to IRC in a typical range of transmit power values.     

Kerckhoffs-Based Embedding Security Classes for WOA Data Hiding

It has recently been discovered that using pseudorandom sequences as carriers in spread-spectrum techniques for data-hiding is not at all a sufficient condition for ensuring data-hiding security. Using proper and realistic apriori hypothesis on the messages distribution, it is possible to accurately estimate the secret carriers by casting this estimation problem into a blind source separation problem. After reviewing relevant works on spread-spectrum security for watermarking, we further develop this topic to introduce the concept of security classes which broaden previous notions in watermarking security and fill the gap with steganography security as defined by Cachin. We define four security classes, namely, by order of creasing security: insecurity, key security, subspace security, and stegosecurity. To illustrate these views, we present two new modulations for truly secure watermarking in the watermark-only-attack (WOA) framework. The first one is called natural watermarking and can be made either stegosecure or subspace secure. The second is called circular watermarking and is key secure. We show that circular watermarking has robustness comparable to that of the insecure classical spread spectrum. We shall also propose information leakage measures to highlight the security level of our new spread-spectrum modulations.     

Robust capacity maximization transceiver design for MIMO OFDM systems多天线正交频分复用系统中鲁棒性容量最大化的收发机设计

In this paper, we investigated capacity maximization problem for Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing systems with imperfect channel state information (CSI). To the best of our knowledge, the considered problem is still an open problem. However, the transceiver designs for MIMO OFDM systems have been extensively studied. It seems nobody gives closed-form solutions for resource allocation for MIMO OFDM systems with statistical channel estimation errors up to date. In our work, based on practical channel estimation algorithm, the channel estimation errors are first derived and then the robust resource allocation problem has been formulated. The structure of the optimal robust precoder is first derived, based on which the optimization problem will be simplified significantly. Furthermore, based on the Lagrangian dual method, a robust power allocation algorithm is proposed. The proposed power allocation can be considered as a variant of water-filling solution named cluster water-filling solution. Finally, simulation results show that our proposed robust design outperforms the non-robust design in terms of channel capacity.