基于差分Pattern时延差编码和海豚whistles信号的仿生水声通信技术研究

为解决传统的隐蔽水声通信方法带来的通信性能降低问题, 提出了一种将差分 Pattern 时延差编码通信体制与海豚whistles信号相结合的仿生水声通信技术. 海豚whistles信号频带较窄且各信息码元间隔不等、码元之间互相关性较弱, 选取whistles信号作同步码和Pattern 码, 并以相邻whistles信号之间的时延差值携带信息. 这种仿生的水声通信信号不易被敌方探测、截获, 且差分Pattern时延差特殊的编码方式也不易使信息被破译, 因此该水声通信技术具有较强的隐蔽性和保密性, 且在抗码间干扰以及抗多普勒效应方面具有优异性能. 本文对系统进行了水池实验, 在信噪比为0 dB、存在相对运动时实现了通信速率为67 bit/s的低误码数据传输, 验证了系统的有效性、稳健性和隐蔽性. 关键词： 仿生水声通信 差分Pattern时延差编码 海豚whistles信号 隐蔽性     

基于时间反转扩频的隐蔽水声通信方法

针对低信噪比条件下水下小尺度平台与通信浮标间进行隐蔽水声通信时,强多径干扰导致通信困难的问题,提出了一种基于时间反转技术的直接序列扩频隐蔽通信方法。该方法利用多通道主/被动时间反转的空时聚焦效应,提高了低信噪比条件下直接序列扩频通信的抗多径干扰能力,并且具有良好的低检测概率通信能力。仿真和水池实验结果表明:该方法满足水下小尺度平台处理结构简单、低功耗的要求,实现了水下单阵元平台与通信浮标之间的双向隐蔽通信。     

NETEST: Estimating a Terrorist Network's Structure—Graduate Student Best Paper Award, CASOS 2002 Conference

Since the events of September 11, 2001, the United States has found itself engaged in an unconventional and asymmetric form of warfare against elusive terrorist organizations. Defense and investigative organizations require innovative solutions that will assist them in determining the membership and structure of these organizations. Data on covert organizations are often in the form of disparate and incomplete inferences of memberships and connections between members. NETEST is a tool that combines multi-agent technology with hierarchical Bayesian inference models and biased net models to produce accurate posterior representations of a network. Bayesian inference models produce representations of a network's structure and informant accuracy by combining prior network and accuracy data with informant perceptions of a network. Biased net theory examines and captures the biases that may exist in a specific network or set of networks. Using NETEST, an investigator has the power to estimate a network's size, determine its membership and structure, determine areas of the network where data is missing, perform cost/benefit analysis of additional information, assess group level capabilities embedded in the network, and pose what if scenarios to destabilize a network and predict its evolution over time.     

A Novel Quantum Covert Channel Protocol Based on Any Quantum Secure Direct Communication Scheme

By analyzing the basic properties of unitary transformations used in a quantum secure direct communication (QSDC) protocol, we show the main idea why a covert channel can be established within any QSDC channel which employs unitary transformations to encode information. On the basis of the fact that the unitary transformations used in a QSDC protocol are secret and independent, a novel quantum covert channel protocol is proposed to transfer secret messages with unconditional security. The performance, including the imperceptibility, capacity and security of the proposed protocol are analyzed in detail.     

一种利用海豚叫声的仿生水声通信方法

针对水下通信隐蔽性的需求, 克服传统固定载波调制方式带来的声源暴露问题, 提出一种基于海豚叫声的仿生伪装水声通信方法, 使通信信号被当作海洋生物噪声排除, 达到隐蔽通信的效果. 研究了海豚叫声信号特点, 利用海豚哨声信号实现同步与识别, 采用差分脉冲位置调制方法, 信息调制在相邻海豚嘀嗒声信号的时间间隔, 采用压缩传感体制下的匹配追踪技术估计信道, 虚拟时反技术实现信道均衡. 湖试结果验证了该方法的有效性和可行性, 接收声信号与发射信号声音上具有很高的相似度, 可以达到伪装隐蔽的效果. 实验中水平距离2 km, 通信速率不小于29 bps时,误码率可以达到10^-4以下. 关键词： 水声通信 仿生 海豚 隐蔽     

信息隐藏的空间概念模型构建

为弥补目前基于信息论的信息隐藏模型缺陷，充分利用信息隐藏活动离散化特点，提出了信息隐藏的空间概念模型．该模型利用集合论和矩阵空间概念对信息隐藏各元素进行了空间概念表示，同时对信息隐藏过程进行了空间转换描述，然后推导出了隐藏评价指标的定量计算公式．结果表明该模型能有效阐释现有信息隐藏技术，在隐藏系统的歼发中更具有可操作性．