One Kind of Auto-Adapted Adjustment Jitterbuffer Size Algorithm

在利用IP电话进行语音通话时,话音的QOS(QuAlITy Of SErVICE)是衡量IP电话好坏的重要指标。为了提高IP电话的QOS,当前已经提出了很多提高语音QOS方面的策略,其中比较著名的方案有:InTSErV/rSVP(集成服务/资源预留),dIffSErV(区分服务)、MPlS(多协议标签交换协议)等。中文主要是基于语音的接收端,设计一种自适应调整抖动缓冲区的大小的一种算法,从而消除语音时延抖动,提高语音通话质量。When carries on conversation making use of the IP telephone,to judge the IP telephone,the QoS(quality of service) nothing but is the important index.In order to improve the IP telephone's QoS,it has already appeared a lot of strategies for enhancing voice.Among them,quite famous plan has:IntServ/RSVP,DiffServ,MPLS.This paper is mainly based on the receiving terminal,design one kind of auto-adapted adjustment buffer's algorithm which eliminates the delay jitter and improves the pronunciation connection quality.福建省自然科学基金项目(A0410004);厦门大学院士基金(0630-E23011);厦门大学新世纪优秀人才基金(0000-X07116

分散式角色激活管理中的角色查找

【摘 要】: 角色激活是基于角色的访问控制中的重要环节, 用户通过激活系统为他分配的角色子集来执行与角色相对应的权限。目前基于角色访问控制主要特点是用户主动、系统被动, 从而给用户带来记忆各种角色-权限分配情况的负担。本文提出一种分散式的基于查找的角色激活管理方法, 与传统方法不同之处在于它是一种用户为被动、 系统为主动的智能访 问控制, 在对企业环境下的动态约束提供有效支持外, 减轻了在传统角色激活方式下用户需要掌握角色- 权限分配情况的负担。基金项目: 中山市科技项目( 2006A157) ; 厦门大学院士基金(0630- E23011); 厦门大学新世纪优秀人才基金(0000- X07116)

Analysis of Linux Real - time Mechanism

摘　要:随着Linux 操作系统在嵌入式实时系统中的广泛应用,有效地提高Linux 有限的实时性能是一个重要问题,而 Linux 内核可抢占调度是实时性能的改进的关键。对Linux 内核调度器的工作原理进行了深入分析,并阐述了调度延迟是 其实时性不强的原因,然后介绍通过可抢占机制对Linux 内核进行改造,测试了改进后的内核的实时性。Abstract :With the wide application of Linux operation system in embedded real - time system fields , the enhancement of Linux real - time performance becomes more and more important . Preemptive kernel is a decisive condition of a system’s real - time performance. This paper analyzes of Linux scheduler and presents that the scheduler latency is the major cause of Linux OS’non - real - time. Then pre2 sent a solution to enhance the real - time performance of Linux. In the end , the simulation results are represented

A New Algorithm for VoIP Adaptive Buffer

网络延迟与缓冲的矛盾是VOIP应用中的一个重要问题。介绍了VOIP应用中几种当前主要的缓冲算法,分别分析了它们的优缺点,提出了新的自适应缓冲算法,称为fISd算法,对现有的代表性算法以及fISd算法分别进行了仿真实验。结果表明,在网络延迟抖动较大时,新算法可以有效地提高语音质量。The contradiction between network delay and the buffer is an important issue of the application of VoIP.Introduces several major current buffer algorithms in the application of VoIP,and analyses their advantages and disadvantages respectively.Then a new adaptive buffer algorithm is proposed,which is named FISD algorithm.The representation of the existing algorithms and FISD algorithm simulation experiments were carried out.The results show that when the network delay jitter is intense,the new algorithm can effectively improve voice quality.福建省2004年自然科学基金资助项目(A0410004);厦门大学院士基金资助项目(0630-E23011);厦门大学新世纪优秀人才支持基金(0000-X07116

A fault2tolerant real2time schedul ing algorithm supporting tasks of multilevel critical ity

摘　要: 针对当前对支持多关键度的实时系统没有涉及容错功能的研究情况,本文提出了支 持多级关键度任务的容错实时系统模型,通过对模型中任务出错后关键度任务集合的响应时 间分析,提出了新的算法,我们称之为补任务启动及容错优先级确定算法,算法假设在运行该 算法的时刻开始系统不会再次出错,基于这个假设计算每个任务的响应时间,从而决定要不要 启动出错任务的补任务以及容错优先级如何分配. 该算法在保证系统的容错能力的同时提高 了任务的完成率,使系统吞吐量损失最小,从而提高系统的可靠性. 最后经过实例对该算法进 行验证.Abstract : Based on the current research area of the real2time system of supporting tasks of multilevel criticali2 ty not including fault2tolerance technology , a fault2tolerant real2time system model supporting tasks of multi2 level criticality is proposed. With the worst2case response time schedulability analysis when an fault happen , a new algorithm that decide whether to startup the alternative task and how to assign the fault2tolerant priority is proposed too. Not only does this algorithm enable the system to recover errors , it also keep the system’s throughout as much as possible. The effectiveness of the approach is evaluated by an instance.基金项目: 广东省自然科学基金(06029667) ;厦门大学院士基金(06302E23011) ;厦门大学新世纪优秀人才基金(00002X07116) ;福建省 自然科学基金(2008J0034

Access Control of Active Networks Based on Decentralized Role Activation Management

可编程性使主动网络面临更严重的安全威胁,虽然已经提出了大量的安全策略和安全机制,但它们的实现多以静态为主,无法满足主动网络的动态需求。提出一种基于分散式角色激活管理的访问控制策略,包括身份认证、授权和权限验证,对动态约束提供了灵活有效的支持,比传统的基于角色的访问控制更适应主动网络的动态特性。最后在此基础上设计了主动节点的安全机制。Programmability makes active networks more vulnerable to security threads.Although many security policies and mechanisms are provided, most of them are implemented in static ways and can not meet the dynamic requirement of active networks.Proposes a decentralized role activation in RABC for active networks,which includes authentication,authorization and permission verification.The mechanism provides a flexible way to support dynamic constraints and is more suitable for the dynamic characteristic of active networks than the traditional RABC.Based on this work,a security mechanism of active node is brought forward in the end.福建省2004年自然科学基金(A0410004);; 厦门大学院士基金资助(0630-E23011);; 厦门大学新世纪优秀人才支持基金(0000-X07116);; 广东省自然科学基金(06029667);; 中山市科技项目(2006A157

The bl ind scheme for channel estimation with high accuracy

摘要：基于多载波 OFDM 系统 ,提出了一种新的时变步长修正软加权判决递归二 乘信道估计盲方法( TVCPMSDWRLS) 。该法通过对常规算法步长进行自适应的科 学设计以便跟踪信道特征变化 ,同时利用接收机判决信息函数修正权系数 ,解决了常 规 RLS盲方法收敛速度慢、 信道估计性能不高的缺点。仿真证明:对于不同的时延 扩展、 时间以及信噪比(SNR) ,该法均表现出比常规方法更优的性能。同时 ,该法亦 可用于估计通信、 雷达、 航天等领域的其他特征参数。英文摘要：A blind channel estimation scheme , named as time2variance convergence parameter and cor rect sof t decision weight RLS ( TVCPMSDWRL S) met hod , based on orthogonal f requency division multiple (OFDM) systems was proposed. The no2 vel scheme could t race adaptively t he channel characteristic t hrough special timevariance gain design. And t he decision information f unction in receiver was al so adapted to correct t he gain. Simulation showed t hat the novel scheme had bet ter per2 formances with high accuracy and fast converges t han t hat of t he RL S met hod , especially via different time delay spread , time and SNR. Furt hermore , the scheme can also suitable in the ot her areas such as communication , Radar , spaceflight to estimate the ot her characteristic parameter s.　 基金项目:广东省自然科学基金资助项目(D06300640) ;广东省中山市科技计划项目 (2006A155) ;电子科技大学中山学院青年科技基金资助项目(2005Y12 和 2006Y02以及 2006Y05) ;福建省自然科学基金资助 项目(A0410004) ;厦门大学院士基金资助项目(06302E23011) ;厦门大学新世纪优秀人才基金资助项目(00002X07204

Authenticated and Key Agreement Protocols Based on Certificateless in P2P Network

目前P2P网络得到了迅猛发展,但由于其本身的结构特点使之面临很多的安全问题。网络安全极大地阻碍了P2P系统的发展。文中在比较传统公钥基础设施(PkI),基于身份的公钥密码系统(Id-PkC)和无证书公钥密码系统(Cl-PkC)各自优缺点的基础上,提出了混合P2P中一种基于Cl-PkC的域内和跨域双向认证和密钥协商协议,并进行了安全性分析。本方案克服了P2P网络中PkI繁琐的证书管理和Id-PkC的密钥托管等问题,提高了双向认证和密钥协商的速度,具有较高的效率,能较好地解决混合P2P网络的安全问题。Now P2P network has been rapidly developed,but it faces a lot of security problems because of the structural characteristics.Network security has greatly hampered the development of P2P systems.Based on the respective analysis of the advantages and disadvantages of the traditional public key infrastructure(PKI),identity-based cryptography(ID-PKC) and certificateless public key cryptography(CL-PKC),proposes one kind of bidirectional authenticated and key agreement protocols in one domain and across multiple domains based on CL-PKC for hybrid P2P network.At last analyses its security.The scheme overcomes the problem of complicated management of PKI certificates and the key escrow of ID-PKC in P2P network.It speeds up the time of bidirectional authenticated and key agreement protocols,proved to be more efficient,and can better solve the security problems in hybrid P2P network.福建省自然科学基金项目(A0410004);厦门大学院士基金(0630-E23011);厦门大学新世纪优秀人才支持基金(0000-X07116

Research on Identity-Based Authentication in SIP

因为简单、灵活和易扩展等特点,SIP将在3gPP中得到广泛应用,但是SIP本身缺少有力的安全机制使其面临很多安全威胁。文中对SIP中的安全问题和安全性要求进行分析,为了解决SIP中认证和消息加密的问题,把基于身份认证这种结构简单、应用容易的安全机制引入到SIP协议中,提出了一种新的认证加密方法。采用基于身份的加密机制使系统初始化简单,不需要繁琐的密钥协商步骤,并且维护容易。同时满足了SIP的安全要求,保证了会话建立和消息通信过程中的完整性、可靠性和不可抵赖性。SIP will be widely applied in 3GPP,because of its simplicity,flexibility and scalability.But a lack of powerful security mechanism,lead it to face many security threats.In this paper,analyse the issues existed and the requirements needed in SIP security mechanism.In order to solve the problems in SIP authentication and information encryption,proposed a new method about authentication by involving identity-based encryption,a security mechanism which has simple architecture and is easy to apply,to the SIP security mechanism.It makes the construction of the system easier.There is no need of complex steps about key agreement,and it is easy to maintain.At the same time it meets the safety requirements of SIP to ensure that the integrity,reliability and incontestability in the process of session establishment and messaging conversation.福建省2004年自然科学基金(A0410004);厦门大学院士基金(0630-E23011);厦门大学新世纪优秀人才基金(0000-X07116

A New Security & Safety Management Mechanism of Active Node Resources

较传统网络而言,主动网络的高复杂性引起了更加严峻的资源安全问题,特别在主动节点方面。尽管在主动网络原型系统中设计了一些安全措施,但是它们都不具通用性。这在主动网络必须和传统网络相兼容的情况下,阻碍了主动网络的发展。文中设计了主动节点资源控制核,然后深入地研究了它与传统网络安全系统的接合问题,提出了对后者的具体修改建议。Active Networks are obviously more complex than traditional networks and raise considerable security & safety (in short, we call them S&S later) problems, especially in active node. Although some S&S technologies are designed in most active networks, all of them cannot be used as a universal way. On condition that active networks must be compatible with traditional IP networks, this situation results in baffling active networks development. Based on some concepts defined in this paper, such as negative error and positive error, this paper designs a resource controlling kernel for active node. In addition, this paper comprehensively studies the problem of tying this kernel in traditional network security system, and then, puts forth some suggestions of modifying traditional network security system in two aspects of security agent lay and security service lay in detail.“十五”国防基金项目 (41 0 0 1 0 1 0 1 0 6