基于云模型的无线传感器网络拥塞及速率控制策略

针对无线传感器网络拥塞带来的网络丢包、能量损耗等问题,提出了一种基于云模型的无线传感器网络拥塞及速率控制策略。节点周期性地计算本地队列拥塞度,利用云模型的模糊随机性控制速率调节因子来决策节点输入速率,再通过公平性策略进行上游节点及本地速率分配。仿真实验结果表明,本文的拥塞及速率控制机制具有良好的公平性和节能性,能够有效缓解网络拥塞,降低网络丢包率,延长网络寿命。     

无线传感器网络中一种实用的公平性控制模型

公平性问题是拥塞控制中的重要级问题,目的是确保所有数据源共享同等的端到端网络带宽.为了适应传感器网络的特点,扩展了传统公平性的定义,提出了一种基于信息量的公平性定义,并基于该定义提出了一套公平性控制模型CFRC.与现有工作不同,CFRC不需要预先确定数据源,对路由结构没有限制,节点上也不需要维护任何数据流信息和全局状态信息,而是动态地实现公平性控制.CFRC使用一种基于感知面积的信息量计算算法,每个节点只需简单的本地计算而无需复杂的计算开销.在带宽分配上,提出了一种干扰源感知的带宽分配方法,以拥塞节点为中心找到所有干扰源,根据干扰源的信息量来分配信道带宽,充分实现公平性目标.模拟结果表明,CFRC能根据各数据源产生报文的信息量进行公平性控制,降低丢弃报文数目.     

度联合信息熵的网络重要节点识别

随着网络科学的快速发展,复杂网络中重要节点识别已是一个重要的研究热点。为了突出邻节点局部结构对节点重要性的影响,本文提出度联合信息熵的网络重要节点识别算法,引入信息熵作为权重来量化各邻节点对节点重要性的贡献,并考虑节点及其邻节点的度值来反映节点在网络中的重要性。在8个真实网络上进行了大量实验。实验结果表明,DE算法相比于其他5种算法能更好地识别网络中的重要节点。     

主动可靠组播拥塞控制协议研究

本文在组播拥塞控制通用模型的基础上,研究对ACC（ActiveCongestionContr01）协议的主要算法和实施过程。ACC策略选取发送者发送速率作为进行拥塞控制的参数。依据最差链路的公平性准则,在主动节点和组播发送者同时进行拥塞参数的过滤,并最终由发送者确定拥塞控制参数。     

AD hoc网络中的机会分组调度算法

无线多跳Adhoc网络中节点在业务发送过程中需要竞争共享信道,容易发生局部拥塞导致网络性能下降,而且节点内部采用的先入先出（FIFO）队列容易使队头阻塞,影响队列中后续分组的发送。本文提出了一种机会分组调度算法CBOS,发送节点采用多播RTS的方式同时指向多个接收节点,可以支持可变长分组,提高了Adhoc网络的空间重用率,接收节点根据拥塞程度按照一定概率返回CTS,有利于节点网络的拥塞控制。仿真结果表明,该算法提高了网络端到端的饱和吞吐量和信道利用率,并提高了业务流之间的公平性。     

无线传感器网络能源有效的拥塞控制算法

提出了一种能源有效的无线传感器网络拥塞控制算法。该算法基于缓冲队列使用情况进行拥塞检测,通过扩大拥塞反馈消息的覆盖范围来提高拥塞的缓解速度,使用倍数降低、线性增加的速率调节策略来保证网络吞吐量的稳定,并且在节点拥塞时根据一定策略丢弃数据包以提高网络传输的公平性。仿真实验表明,提出的算法不仅能有效地缓解网络拥塞、降低网络丢包率,还具有较好的能源有效性和网络传输的公平性。     

AD hoc网络中的机会分组调度算法

无线多跳Ad hoc网络中节点在业务发送过程中需要竞争共享信道,容易发生局部拥塞导致网络性能下降,而且节点内部采用的先入先出(FIFO)队列容易使队头阻塞,影响队列中后续分组的发送。本文提出了一种机会分组调度算法CBOS,发送节点采用多播RTS的方式同时指向多个接收节点,可以支持可变长分组,提高了Ad hoc网络的空间重用率,接收节点根据拥塞程度按照一定概率返回CTS,有利于节点网络的拥塞控制。仿真结果表明,该算法提高了网络端到端的饱和吞吐量和信道利用率,并提高了业务流之间的公平性。     

对网络QoS中拥塞控制的研究

拥塞控制是解决网络拥塞问题的重要策略。本文主要从流量预测和流量整形两个方面提出了降低拥塞率的通用方法,对传统的漏桶算法和RED算法做了改进,使得它们在降低拥塞率的同时又照顾到了公平性和效率。     

基于加权公平的DiffServ服务质量模型的研究

针对在核心节点实现的主动队列管理（AQM）以预见和防止拥塞,并且能够较公平地分配带宽,介绍了一种加权公平的主动队列管理算法,提出一个基于公平性的拥塞控制机制,即将这种AQM算法部署在可提供QoS服务的区分服务模型中,最后介绍仿真过程并分析该模型的性能．     

软覆盖熵及其在多属性群决策中的应用

结合软覆盖与信息熵,提出软覆盖信息熵.定义软覆盖信息熵、软覆盖联合熵、软覆盖条件熵,并研究这些熵之间的关系及它们的重要性质.最后给出两种基于软覆盖条件熵的多属性群决策的算法,举例说明这两种算法的结果具有一致性.     

一种自适应的无线传感器网络拥塞缓解机制

提出一种自适应的拥塞缓解机制。当无线传感器网络发生拥塞时,尝试在拥塞节点附近建立新路径,路径建立失败时引入公平汇聚机制,按汇聚数据流权重大小比例限制上游节点速率以减少源节点数据发送率。仿真实验表明,该机制减少了能耗,降低了丢包率,使重要的数据能实时、公平地传送到目的节点。     

异构网络中基于MPTCP的协作拥塞控制方案

提出了一种基于MPTCP的协作拥塞控制方案。在拥塞避免阶段,该方案首次以马尔科夫链模型为基础,对异构网络中各条路径上未被确认的数据包个数进行预测,进而计算出各条路径所能承载的最大数据量。若网络拥塞窗口值大于各条路径所能承载的最大数据量中最小值的2倍,则启动协作拥塞控制机制。在协作拥塞控制机制下,根据AIMD算法的加性增加准则调整拥塞窗口,若网络拥塞窗口值大于各条路径所能承载数据量之和,则结束协作拥塞控制机制,执行传统的TCP慢启动算法。为了提高慢启动阶段的带宽利用率,对TCPW(TCP Westwood)带宽估计算法进行改进,使路径可用带宽的估计更准确,从而提高慢启动阈值设置的合理性。仿真结果表明,在保证异构网络负载均衡及单条TCP流公平性的前提下,该方案能够增加成功传输数据包的数量。     

自适应调整TCP阻塞控制窗口算法研究

提出了新的TCP速率调整算法.根据边缘路由器缓冲区中的输入数据报和输出数据报的变化,得到合理阻塞控制窗口,直接通过明确阻塞标记数据报返回到发送终端,从而改变了TCP发送速率.通过对仿真结果的分析,新算法可以明显地控制TCP的业务量,限制边缘路由器的队列的拥塞,大大降低数据报的丢失率,从而提高TCP的延迟性能和带宽分配的公平性.     

Hop-count based probabilistic packet dropping: Congestion mitigation with loss rate differentiation

Network applications and users have very diverse service expectations and requirements, demanding for provisioning different levels of quality of service on the Internet. As the speed of network links has been rising at a pace that exceeds that of the growth in the buffer size, packet loss rate differentiation has been an active research topic. However, none of the existing packet dropping schemes for loss rate differentiation considered an important issue, that is, the retransmission overhead of dropped packets. In this paper, we design a hop-count based probabilistic packet dropper (HPPD) for congestion mitigation and loss rate differentiation. HPPD aims to meet a unique two-fold objective by two-dimensional loss rate differentiation: the primary one is the congestion mitigation that aims to reduce congestion in the first place by dropping intra-class packets differently based on their maturity levels to reduce retransmission cost; the other is inter-class proportional loss rate differentiation. The maturity level of a packet, the number of hops it has travelled, is inferred from its time-to-live value in the IP header. We propose a novel intra-class nth-root proportional dropping scheme. The scheme reduces retransmission cost by giving higher dropping probabilities to less mature packets while all packets have their forwarding chances. The n is a controllable parameter trading off dropping fairness for congestion mitigation. It provides great controllability to network operators. Simulation results show that HPPD can significantly mitigate the congestion by reducing the retransmission overhead of dropped packets and achieve the proportional loss rate differentiation at the same time.     

Configurable active multicast congestion control

A multicast congestion control and avoidance scheme is indispensable for group-based applications to fairly share and efficiently use network resources with unicast applications and maintain the stability of the Internet. It is difficult for the traditional pure “end-to-end” solution to address both TCP-friendliness and inter-receiver fairness [T. Jiang, M.H. Ammar, E.W. Zegura, Inter-receiver fairness: a novel performance measure for multicast ABR sessions, in: Proceedings of ACM SIGMETRICS’98; T. Jiang, E.W. Zegura, M. Ammar, Inter-receiver fair multicast communication over the Internet, in: Proceedings of NOSSDAV’99] by using only one multicast group. In this paper, we present a novel active multicast congestion control scheme (AMCC). Significantly different from the popular end-to-end congestion control approach, AMCC is a router-assisted window-based hierarchical one. With flexible configuration of parameters and effective use of network resources such as buffers at the active routers, AMCC cannot only behave as a TCP-friendly single-rate congestion control scheme, but also have the benefits of a multi-rate congestion control scheme to achieve inter-receiver fairness by limiting the effect of congestion on a specific link to a small region. In addition, when it is used with reliable multicast applications, AMCC has the special mechanisms to regulate repair packets, which are not specifically addressed by the previous work. We implement and evaluate our protocol in NS2 [http://www.isi.edu/nsnam/ns/].     

Active Queue Management Exploiting the Rate Information in TCP-IP Networks

In this paper, we propose a new mechanism called explicit rate notification (ERN) to be used in end-to-end communications. The ERN scheme encodes in the header of transmission control protocol (TCP) packets information about the sending rate and the round trip time (RTT) of the flows. This new available information to the intermediate nodes (routers) is used to improve fairness, increase utilization, decrease the number of drops, and minimize queueing delays. Thus, it induces a better management of the queue. A comparison of our scheme with preexistent schemes, like the explicit congestion notification scheme, shows the effectiveness of the proposed mechanism.      

一种支持公平带宽分配的主动队列管理方案的研究

现在广泛使用的主动队列管理(AQM)是目前队列管理的主流技术,但是它不能很好地区分来自响应流(如TCP会话)和非响应流(如UDP)的包。当拥塞出现的时候,将导致非响应流压制响应流并占有较多的带宽,而响应流却无法获得公平带宽。本文提出了一种闭环拥塞控制(CLCC)方案,大大改善了带宽分配的公平性。