基于数据包长度的网络隐蔽通道

在传统隐蔽通道模型的基础上,利用数据包的长度域,设计一种基于数据包长度的网络隐蔽通道模型(LAWB模型),给出其形式化描述。对该模型进行了分析,并分别在IPv4和IPv6上对该模型进行了实验。     

基于链路分析法的复合隐蔽通道检测

在研究隐蔽通道的检测方法时，可以将隐蔽通道分成两大类：单一隐蔽通道和复合隐蔽通道。复合隐蔽通道具有了跨越多主机的特点，简单的主机入侵检测体系结构很难对此进行检测，而数据融合技术可以有效地解决这个问题。文中提出了基于数据融合思想的链路分析法，并对复合隐蔽通道的特点、链路分析法检测复合隐蔽通道的理论以及软件的设计进行描述。     

一种基于通道的AVISPA扩展方法研究

针对AVISPA工具在分析某些消息需要依靠具有特定属性的信道传递的安全协议或服务中存在的问题, 提出了一种基于抽象通道的扩展方法。抽象通道具有相关的安全性质保证如认证性, 能够对提供安全性质保证的底层服务建模, 并基于密码机制和标签等实现了抽象通道。利用扩展后的AVISPA工具分析有无消息源认证机制的Diffie-Hellman密钥交换协议的安全性, 表明了方法的有效性, 并且能够简化协议建模过程和增强AVISPA工具协议描述分析能力。     

光纤通道与CWDM系统接口的设计与实现

通过对光纤通道（Fibre Channel，FC）物理层结构的分析，结合粗波分复用（Coarse Wave Division Multiplexing，CWDM）技术，提出了一种光纤通道与CWDM系统之间接口实现的解决方案，克服了传统光纤通道技术中传榆距离太短的局限性，为实现城域范围内的远程存储系统提供了可能。     

通过通道实现对选区的控制

通道是图形图像学上一个重要的概念，文章分析了各种通道的概念及形式，比较了三种不同形式的通道在图像处理中对选区的控制作用，揭示了通道转换成选区后是按照不透明度来填充整个图像区域的原理，但是要注意不透明度的计算方法在不同的情况下是不同的。     

数据库系统隐蔽通道分析的设计

从隐蔽通道概念入手，阐述了隐蔽通道分析在Oracle中的设计思想，讨论了隐蔽通道分析的内容与层次、隐蔽通道的标识方法、隐蔽通道带宽的计算与测量、隐蔽通道的处理，就如何提高Oracle 9i安全性能提供了一种途径。     

通信协议形式化模型的研究

本文提出了适应于通信协议的一类抽象形式化模型：抽象行为模型和抽象结构模型．前者主要包括事件、输入／输出、内部／外部和状态等子模型；后者主要包括交互点和分层子模型．文中讨论了这类形式模型的有效性和适用性，运用该类模型对通信协议的主要概念及性质进行了形式定义和描述．重点给出了基于该类模型的协议安全性及活性的形式定义，研讨了安全性及活性的验证，以及某些典型形式描述技术FDT（Estelle，LOTOS，SDL）之间的语义联系，从而为通信协议的研究提供了一种有效的形式基础．     

实例剖析Photoshop通道

通道在PhotoShop中被认为是一个较难理解的概念，通过实例分析可知通道的本质就是灰度。由于图像的不同区域其像素灰度不同．因此所拥有的基色浓度也不相同，从而使图像呈现出斑斓的景色。也正是由于灰度明暗反映了图像的颜色信息，人们就能充分利用通道对图像实施多种特殊效果的处理。     

隐通道及其搜索方法

根据TCSEC规定，开发B2及以上安全系统时必须进行隐通道分析，该文简要介绍了隐通道的概念及分类，并在比较现有隐通道搜索方法优缺点的基础上，详细给出了共享资源矩阵法的隐通道分析操作步骤。     

基于IGMPv2的隐蔽通道

目前IP组播技术应用越来越广泛，其应用的协议是IGMP，该协议不断完善，版本不断升级，安全性也得到了提高。但是，在目前应用最广的IGMPv2中，可以实现隐蔽通道，最明显的是协议包中的“路由器检测选项”字段和“最大响应时间”字段。该文主要针对如何使用这两个字段实现隐蔽通道加以讨论。介绍了隐蔽通道和IGMP的基本概念，说明了该隐蔽通道的实现原理，描述了软件设计，最后对该方法进行了分析。     

Hadamard quantum broadcast channels

We consider three different communication tasks for quantum broadcast channels, and we determine the capacity region of a Hadamard broadcast channel for these various tasks. We define a Hadamard broadcast channel to be such that the channel from the sender to one of the receivers is entanglement-breaking and the channel from the sender to the other receiver is complementary to this one. As such, this channel is a quantum generalization of a degraded broadcast channel, which is well known in classical information theory. The first communication task we consider is classical communication to both receivers, the second is quantum communication to the stronger receiver and classical communication to other, and the third is entanglement-assisted classical communication to the stronger receiver and unassisted classical communication to the other. The structure of a Hadamard broadcast channel plays a critical role in our analysis: The channel to the weaker receiver can be simulated by performing a measurement channel on the stronger receiver’s system, followed by a preparation channel. As such, we can incorporate the classical output of the measurement channel as an auxiliary variable and solve all three of the above capacities for Hadamard broadcast channels, in this way avoiding known difficulties associated with quantum auxiliary variables.     

Channel dynamic adjustment in data broadcast

Data broadcasting has become the preferred method to dispense data to a large number of mobile users. Current researches on on-demand data broadcast mainly propose algorithms based on a single broadcast channel or fixed multi-channel, i.e., fixed channel model. As a result of the dynamic diversity of data characteristics and client demands, the fixed channel model faces significant challenges in parallel broadcast diverse data. Further, the dynamic adjustment of the broadcast channel (dynamic channel model) based on client requests is favorable to service quality because it determines the number and sizes of channels that adapt to client demand in real-time. However, the dynamic channel model has not yet been thoroughly investigated for on-demand wireless data broadcasts. Accordingly, in this paper, a channel dynamic adjustment method (CDAM) is proposed. The innovations behind CDAM lie in three aspects. First, a data item priority evaluation and selection algorithm (S-RxW/SL) is proposed for evaluating the priority of data items and selecting the high priority data items to be considered in a broadcast cycle. Second, a weight and size average cluster algorithm (WSAC) is proposed for mining data item characteristics and clustering them. Third, based on the clustering results of WSAC, a channel splitting and data allocation algorithm (CSDA) is proposed for dynamically splitting the channel and allocating data items to the corresponding sub-channel. We compare the proposed method with some state-of-the-art scheduling methods through simulation. The theoretical findings and simulation results reveal that significantly better request loss rate (LR) can be obtained by using our method as compared to its alternatives.     

一种新的异步广播通信系统物理层设计

基于Turbo喷泉码和小波包分形调制技术，提出一种新的异步广播通信系统FPGA实现方案。系统用并行信源信道Turbo喷泉码实现无损数据压缩和纠错，小波包调制实现发送信号时频图样的自由铺砌。系统可以同时实现接收机的异步接入、单向信道下数据的可靠分发及信源信道联合编码，仿真表明该系统相对普通信源信道编码调制有较大性能改善。     

基于哈夫曼树的无证书公钥广播加密方案

现有的无证书广播加密方案是向用户传输相同的信息量,没有权限的概念。基于哈夫曼树,引入权值,提出了一种新的无证书公钥广播加密方案,实现了对不同权限的用户传输不同的信息量。与已有的广播方案相比,该方案平均计算密钥量少,降低了通信开销,灵活性更高。     

Semantic Access to Multichannel M-Services

M-services provide mobile users wireless access to Web services. In this paper, we present a novel infrastructure for supporting M-services in wireless broadcast systems. The proposed infrastructure provides a generic framework for mobile users to look up, access, and execute Web services over wireless broadcast channels. Access efficiency is an important issue in wireless broadcast systems. We discuss different semantics that have impact on the access efficiency for composite M-services. A multiprocess workflow is proposed for effectively accessing composite M-services from multiple broadcast channels based on these semantics. We also present and compare different broadcast channel organizations for M-services and wireless data. Analytical models are provided for these channel organizations. Practical studies are presented to demonstrate the impact of different semantics and channel organizations on the access efficiency.     

Query optimization for broadcast database

In a mobile environment, the broadcast paradigm has been recognized as an effective way to disseminate frequently requested information to multiple ‘mobile clients’. In this paper, we show that to query the broadcast database efficiently, database items must be organized over the broadcast channel in a meaningful way, reflecting the semantics of the database being broadcast. We define, for the first time, a cost model called the Semantic Ordering Model for identifying the optimal organization of database items over the broadcast channel. Experimental results are also delineated to illustrate the feasibility of our cost model, using relational and object-oriented databases as examples.     

Object Organization on a Single Broadcast Channel in the Mobile Computing Environment

Advances in computation and communication technologies allow users to access computer networks, using portable computing devices via a wireless connection, while mobile. Furthermore, multidatabases offer practical means of managing information sharing from multiple preexisting heterogeneous databases. By superimposing the mobile computing environment onto the multidatabase system, a new computing environment is attained.In this work, we concentrate on the effects of the mobile-computing environment on query processing in multidatabases. We show how broadcasting, as a possible solution, would respond to current challenges such as bandwidth and storage limitations. Organizing data objects along a single-dimension broadcast channel should follow the semantic links assumed within the multiple-dimension objects' structure. Learning from our past experiences in objects organization on conventional storage mediums (disks), we propose schemes for organizing objects along a single broadcast air channel. The proposed schemes are simulated and analyzed.     

一种最小连通支配集的分布式广播算法

研究移动自组网络中的广播算法,提出了一种适用于移动自组网络的基于最小连通支配集的分布式广播算法,并证明了新的广播算法与已有算法相比能够更加有效地解决网络采用洪泛(Flooding)方式进行广播时所可能产生的广播风暴问题。同时,算法是基于并行和分布式运行模式的,因此具有很好的扩展性和实用性。     

Optimal transmission schemes for parallel and fading Gaussian broadcast channels with an energy harvesting rechargeable transmitter

We consider an energy harvesting transmitter sending messages to two users over parallel and fading Gaussian broadcast channels. Energy required for communication arrives (is harvested) at the transmitter and a finite-capacity battery stores it before being consumed for transmission. Under off-line knowledge of energy arrival and channel fading variations, we obtain the trade-off between the performances of the users by characterizing the maximum departure region in a given interval. We first analyze the transmission with an energy harvesting transmitter over parallel broadcast channels. We show that the optimal total transmit power policy that achieves the boundary of the maximum departure region is the same as the optimal policy for the non-fading broadcast channel, which does not depend on the priorities of the users, and therefore is the same as the optimal policy for the non-fading scalar single-user channel. The optimal total transmit power can be found by a directional water-filling algorithm. The optimal splitting of the power among the parallel channels is performed in each epoch separately. Next, we consider fading broadcast channels and obtain the transmission policies that achieve the boundary of the maximum departure region. The optimal total transmit power allocation policy is found using a specific directional water-filling algorithm for fading broadcast channels. The optimal power allocation depends on the priorities of the users unlike in the case of parallel broadcast channels. Finally, we provide numerical illustrations of the optimal policies and maximum departure regions for both parallel and fading broadcast channels.