一种适应于通信协议自稳定性的恢复算法

主要提出了一种适应于通信协议自稳定性的恢复算法 .先论述了适用于该算法的有关概念及形式描述方法 ;接着描述了该恢复算法 ,并给出了该算法的正确性证明及复杂性分析 ;最后通过一个多进程通信协议的实例研究 ,验证了该算法的正确性和有效性 .     

RMP：一种具有高可伸缩性的随机成员协议

针对组播通信协议中所使用的成员协议的伸缩性差的问题，提出了一种新的随机成员协议(RMP)。RMP通过使用随机的响应组成员的加入请求，建立一个每个节点仅仅维护logN个其它成员信息的连接图，并可以为可靠的报文扩散提供基础。文中对RMP的算法在数学上进行了分析，并通过仿真进行验证，结果表明，RMP是一种具有很强可伸缩性的成员协议。     

Modified distributed snapshots algorithm for protocol stabilization

This paper assesses the use of Chandy and Lamport's distributed snapshots algorithm (DSA) for stabilizing a communication protocol, a special type of distributed system. We show that when a loss of coordination occurs during the distributed execution of the protocol, DSA is not guaranteed to terminate, and therefore it sometimes fails to obtain a global state or snapshot. We propose some modifications to DSA to solve this problem. Finally, we discuss how, in the case of a loss of coordination, the modified algorithm can be used to stabilize a communication protocol, and we assess the suitability of the global state obtained by DSA as a recovery point to be used later in a backward recovery procedure.     

A Token-Based Fault-Tolerant Distributed Mutual Exclusion Algorithm

In this paper, we propose a token-based distributed mutual exclusion algorithm that is resilient to site and communication failures. The protocol uses the notion of logical time to detect the loss of the token and to recover the state of the lost token. Unlike other approaches, this results in the integration of token recovery due to failures with the protocol itself. Thus, we eliminate the need for expensive election protocols that are generally used in token-based algorithms to regenerate lost tokens. We also introduce the notion of weakly consistent replicated queues that are used to ensure freedom from starvation.     

Consensus of linear multi-agent systems with reduced-order observer-based protocols

This paper considers the consensus problems for both continuous- and discrete-time linear multi-agent systems with directed communication topologies. Distributed reduced-order observer-based consensus protocols are proposed, based on the relative outputs of neighboring agents. A multi-step algorithm is presented to construct a reduced-order protocol, under which a continuous-time multi-agent system whose communication topology contains a directed spanning tree can reach consensus. This algorithm is further modified to achieve consensus with a prescribed convergence rate. These two algorithms have a favorable decoupling property. In light of the modified algebraic Riccati equation, an algorithm is then given to construct a reduced-order protocol for the discrete-time case.     

一种复制数据库恢复协议研究

数据复制是提高数据库系统性能和可用性的重要技术。近年来出现的基于组通信技术的数据库复制协议较之传统的数据库复制协议因其实现简单灵活、性能较优,在构建实用复制数据库系统时得到广泛应用,维持各节点副本一致性是数据复制技术研究的核心问题。本文讨论了当故障节点恢复后重新加入系统或增加新节点后如何恢复、维护系统节节点副本间的一致性的问题。本文提出了一个针对分布复制数据库系统的恢复协议,该协议结合基于组通信技术的复制协议,可在不影响系统正常事务处理的情况下,实现故障恢复后节点或全新节点重新加入系统时的系统正确恢复,并给出了理论证明。同时还证明,该恢复协议对于分布在不可靠网络上的复制数据库的恢复问题同样适用。     

基于对称W态和身份认证的安全量子通信协议

由于W态纠缠的强鲁棒性,它被认为是更适用于量子信息处理和量子安全通信的信息载体。针对4粒子W态或3粒子非对称W态量子直接通信效率低下或物理实现困难等缺陷,利用3粒子对称W态和量子身份认证机制,提出了一种新的确定型安全量子通信协议。该协议由认证码生成、量子态准备、量子态分发、安全检测与身份认证和消息通信五阶段组成,通信双方只需进行两粒子Bell基、单粒子Z基或X基测量,通信效率也有所提高,即1个3粒子W态传输1经典比特信息。安全分析证明该协议能有效抵抗各类窃听者Eve攻击和伪装攻击,具有较好的安全特性。     

An ID-based authenticated dynamic group key agreement with optimal round

Group key agreement protocols are crucial for achieving secure group communications.They are designed to provide a set of users with a shared secret key to achieve cryptographic goal over a public network.When group membership changes,the session key should be refreshed efficiently and securely.Most previous group key agreement protocols need at least two rounds to establish or refresh session keys.In this paper,a dynamic authenticated group key agreement(DAGKA) protocol based on identity-based cryptography is presented.By making use of the members’ values stored in previous sessions,our Join and Leave algorithms reduce the computation and communication costs of members.In the proposed protocol,Setup and Join algorithms need one round.The session key can be refreshed without message exchange among remaining users in Leave algorithm,which makes the protocol more practical.Its security is proved under decisional bilinear Diffie-Hellman(DBDH) assumption in random oracle model.     

改进椭圆曲线密码体制在SET协议中的应用

在电子商务中,安全电子交易（SET）协议作为目前安全性较高的协议之一,解决了一定的安全问题.然而,由于SET加解密方案安全强度不足,其安全性逐渐受到人们的怀疑.由此,提出一种改进的椭圆曲线密码体制用于替代原有私钥加密算法,提高协议的速度、性能及安全性.针对ECC加解密过程中点乘法运算耗时较多而影响数据加解密速度的问题,通过对几种改进的数乘算法进行比较,提出一种改进的NAF算法.比较可得出改进算法相对于现有算法拥有更好的时间复杂度并使用更少的计算资源.同时融合使用MD5哈希生成算法进一步提高了现有椭圆曲线密码体制的安全性.     

基于认知无线电的DVB-S2信号接收与解析

DVB-S2协议作为第二代数字电视卫星广播协议,因具有突出的信号传输性能,在国际上得到了广泛的应用。现有的DVB-S2信号接收多采用标准的商用设备,不便于对信号接收的各个环节进行具体分析。基于此协议,开展了利用认知无线电USRP X310设备和Matlab数字算法实现信号接收解析的研究,同时分析各算法参数对信号接收质量的影响。该研究成果为信号协议进行更深层次的分析和研究以及后续的DVB-S2信号产生、通信对抗等提供可靠的设计指导。为了实现通信系统最大透明化,仅使用认知无线电设备对空间模拟信号进行放大和采样,其余部分全由数字信号处理领域的相关算法完成。文中详细阐述了整个接收平台的硬件设备参数设置和软件系统框架及其内部关键环节的算法实现。关键环节包括符号同步、物理层帧头检测与解析和载波同步等,其中符号同步和载波同步通用于其他通信系统,而物理层帧头检测与解析为针对DVB-S2协议特定设计的环节。最后,以亚洲五号卫星Ku波段上的一个特定节目为例详细说明了DVB-S2信号在接收过程中的处理流程及结果,原始数据传输流最终被正确恢复,该节目视频和音频亦成功播放。     

身份认证的密钥交换算法

密钥交换是通信双方建立会话密钥的过程，Diffie—Hellman协议是一种有代表性的算法，但是这种算法不能够抵抗中间人攻击。为了抵抗中间人攻击，陆续出现了几种具有身份认证功能的算法，但是这些算法运算比较复杂。Seo等提出了一种简单的算法（SAKA），可以抵抗中间人攻击，并且运算简单。但是SAKA以及其的增强算法均有缺陷，该文提出了一种改进算法，在具有原有协议优点的同时可以避免这些缺陷。     

Efficient indirect all-to-all personalized communication on rings and 2-D tori

All-to-All personalized communication is a basic communication operation in a parallel computing environment.There are a lot of results appearing in literature.All these communication algorithms can be divided into two kinds:direct communication algorithm and indirect communication algorthm.The optimal dircet all-to-all communication algorithm on rings and 2-D tori does exist.But,for indirect all-to-all communication algorithms,there is a gap between the time complexity of the already existing algorithm and the lower bound,In this paper an efficient indirect algorithm for all-to-all communication on rings and 2-D square tori with bidirection channels is presented.The algorithms is faster than any previous indirect algorithms.The main items of the time complexity of the algorithm is 2^2/8 and p^3/2/8 on rings and 2-D tori respectively,both reaching the theoretical lower bound,where p is the number of processors.     

Distributed consensus of multi‐agent systems with general linear node dynamics and intermittent communications

Without assuming that the mobile agents can communicate with their neighbors all the time, the consensus problem of multi‐agent systems with general linear node dynamics and a fixed directed topology is investigated. To achieve consensus, a new class of distributed protocols designed based only on the intermittent relative information are presented. By using tools from matrix analysis and switching systems theory, it is theoretically shown that the consensus in multi‐agent systems with a periodic intermittent communication and directed topology containing a spanning tree can be cast into the stability of a set of low‐dimensional switching systems. It is proved that there exists a protocol guaranteeing consensus if each agent is stabilizable and the communication rate is larger than a threshold value. Furthermore, a multi‐step intermittent consensus protocol design procedure is provided. The consensus algorithm is then extended to solve the formation control problem of linear multi‐agent systems with intermittent communication constraints as well as the consensus tracking problem with switching directed topologies. Finally, some numerical simulations are provided to verify the effectiveness of the theoretical results. Copyright © 2013 John Wiley & Sons, Ltd.     

Automatic fine-grained area detection for thin client systems

The widespread availability of cloud infrastructures is fueling new interest in the thin client computing paradigm. However, current thin client protocols are not designed to handle new content types as often encountered in state-of-the-art applications (e.g. multimedia editing, gaming, multimedia playback). Conveying this content using traditional thin client protocols typically results in a combination of excessive resource usage and low visual quality. In this paper, we propose an approach where the content type can vary for different portions of the screen (e.g. combination of static text and video). Once the different content types have been detected, each of them can be encoded using the most appropriate algorithm. We present two algorithms for this runtime detection. The first algorithm is operating at the pixel level, thereby being independent of the actual thin client protocol used. The second algorithm assumes the presence of a rectangle-based thin client protocol (such as the popular VNC protocol), trading independence for improved performance. The appropriate parameter settings for these algorithms are experimentally determined. Furthermore, their influence is studied in detail in terms of detection accuracy, and the time to perform the algorithms is analysed. Accurate hints are derived within less than 10 ms, indicating the high potential of this approach for use in next generation thin client systems.     

一个通用通讯程序设计与测试的研究

通讯程序的应用非常广泛,关于通讯方面的系统协议也多种多样,但是绝大多数系统提供的协议一般都比较复杂,这些协议都没有多链路管理。本文设计一种相对简单通用的、可靠的、多链路管理的通讯程序。该通用通讯程序能唆封装多种底层协议,为上层应用提供统一的调用接口,方便使用。另外,多链路管理也使得通讯更加可靠。在设计和测试的过程中,大量实验表明,本程序具有良好的特性,在模拟环境中使用也起到了不错的效果。     

一种自适应GPS通信协议分析算法的设计与实现

由于缺少GPS通信服务标准,不同的GPS监控设备在GPRS上传输的数据通信协议有较大差别,这给综合性的GPS监控信息接入带来了困难,协议版本的不断变化也加剧了数据分析的困难。基于有限自动机模型,设计了一种自动协议分析算法,能够实现一套程序同时对多种协议进行分析和转换。     

通信协议的并行机制研究

通信技术的迅速发展，通信网络所提供的带宽达到几百Ｍｂｐｓ～Ｇｂｐｓ数量级。一些应用，象多媒体通信，就能利用网络的高吞吐量。但是，目前的通信协议并不能适应高速传输的环境。运输层和其它较高层协议的处理，已成为通信系统的性能瓶颈。本文首先回顾近十年来通信环境所发生的一些变化，并分析其对运输层协议的影响；第二部分分析标准协议并行实现时的一些关键技术；最后介绍了一个运输层系统模型，该模型采用并行机制，向上提供高性能的运输层服务。     

一种可靠可伸缩组通信系统设计与实现

组通信系统是支持一致性和容错的分布式协同系统中非常重要的组成部分.为了满足大规模协同应用的需求,文中采用了基于流言的协议与确定性协议组合的方法设计并实现了一种可靠可伸缩组通信系统SGCS.该系统主要包括可靠消息传输服务与组成员管理服务,其中基于流言的可靠多播协议和确定的消息恢复、流量控制、排序协议的组合,基于流言的失败检测协议与确定的视图一致化协议的组合以及乐观虚同步机制应用使系统具有良好的可伸缩性、可靠性和灵活性.     

基于HART协议的智能仪表通信电路设计

从HART协议智能仪表的功能和协议要求出发,详细分析了HART协议智能仪表通信的设计重点、难点和关键技术,设计了完整的HART协议智能仪表通信的实用电路,可以实现HART协议智能仪表通信的基本功能。该智能仪表可用于实时监测,低功耗并且具有兼容模拟和数字通信的能力。