基于往返延迟抖动区分丢包的TCPW改进

针对TCP Westwood(TCPW)在高误码率无线网络环境下不能区分无线丢包和拥塞丢包的问题,提出了一种基于往返延迟抖动区分丢包的TCPW改进协议,称之为TCPWBJ。它根据测得的往返延迟抖动划分拥塞等级,区分无线丢包和拥塞丢包,并根据拥塞等级进行相应的拥塞控制。仿真结果表明,TCPW BJ算法在高误码率无线网络中,显著提高了带宽利用率和吞吐量,并保持良好的公平性与友好性。     

基于DupAck的Ad Hoc网络TCP性能改进

为改进传输控制协议(TCP)在无线网络环境下的性能,分析Ad Hoc网络数据丢失的原因,提出一种区分无线丢包和拥塞丢包的算法。该算法通过在发送端检测返回的重复Ack的相对单向传输时延,探测到网络真实的拥塞状况,以便采取合理的拥塞控制措施。仿真结果表明,该算法能够正确区分无线丢包和拥塞丢包,改善Ad Hoc网络的TCP性能。     

无线/有线混合网络下基于平均丢包率差值的Fuzzy丢包评判算法

在对最后一跳为无线的无线/有线混合网络下,对无线误码丢包和网络拥塞丢包的平均丢包率差值统计概率分布特点进行了分析和验证,在此基础上提出了一种基于平均丢包率差值的Fuzzy丢包区分算法,利用Fuzzy模式识别区分丢包原因.仿真验证表明,该算法效果比较理想.     

基于丢包事件统计的TCP-Veno改进算法

针对TCP-Veno在轻负载网络环境中不能有效利用带宽,在重负载网络环境中不能准确区分拥塞丢包和无线随机丢包而造成频繁拥塞等问题,提出一种改进算法TCP-Veno+。通过对一定时间段内拥塞丢包事件和无线随机的丢包事件的数量统计,计算两种不同类型丢包事件的发生概率,在此基础上改进原TCP-Veno的丢包区分算法,提高了丢包区分的准确性。仿真实验结果表明,改进算法在无线异构网络中提高了网络传输性能,同时具有较好的公平性和稳定性。     

无线TCP友好拥塞控制研究

分析了流媒体业务在无线环境下传输所存在的问题,在TFRC算法研究的基础上,提出了一种适用于流媒体业务传输的无线TCP友好拥塞控制机制WL_TFRC,在接收端引入了丢包区分机制来区分拥塞丢包和无线丢包。     

基于Fuzzy丢包区分的TCP拥塞控制算法

针对传统传输控制协议(TCP)应用于异构网络的局限性,在研究灰色关联度基础上,分析网络参数,提出一种基于往返延迟抖动积区分丢包的TCP-N算法.根据测得的往返延迟抖动积构建隶属函数,区分无线误码丢包和网络拥塞丢包,并依据隶属度进行相应的拥塞控制.仿真实验结果表明,与传统TCP协议相比,TCP-N算法在异构网络中能够较准确地区分无线误码丢包和网络拥塞丢包,提高带宽利用率和吞吐量.     

基于误码丢包率监测的无线TCP改进

针对无线环境下TCP错误调用拥塞控制算法致使性能下降的情况,提出一种基于误码丢包率监测的无线TCP改进方法。利用显式拥塞通知的路由器配合区分分组丢失性质,在数据发送端采用实时误码丢包率监测,并根据监测结果调整TCP段尺寸。仿真结果表明,改进后的TCP吞吐量在误码率为1E-4时超过TCP_SACK和TCP_Reno近1倍。     

一种无线Mesh网络跨层丢包通告机制

现有TCP机制无法有效区分网络丢包是拥塞丢包还是“失聪”丢包。针对该问题,提出一种在无线Mesh网络环境下跨层显示“失聪”丢包通告机制。该机制在系统使用定向天线条件下采用基于忙音的媒体接入控制机制区分数据丢包原因,通过IP和TCP跨层设计显示通告帧和定义的多跳转发规则向源端进行正确的通告。利用该机制对线性无线Mesh网络进行理论推导和分析,并通过数值实验证明其可行性和有效性。     

改善无线TCP性能的新技术

文章研究了一种被称为累积显式传输错误通知(CETEN)的新技术,它利用网络提供的信息使得TCP长期平均发送速率更加接近仅由拥塞丢包决定的带宽。讨论了几种获取拥塞丢包率和误码丢码率的方法。研究了两种更加适合的利用此信息的拥塞控制方式。初步的仿真表明CETEN可以有效地改善无线TCP的性能。     

高误码率无线环境的TCPW改进算法

针对TCP Westwood（简称TCPW）拥塞避免算法在高误码率无线网络环境下不能区分丢包原因和性能仍显不足的问题,在中间节点提出了一种简单有效的拥塞标记机制,称为CM（Congestion Marking）,它是基于ECN的,将拥塞程度划分为无拥塞、轻度拥塞和重度拥塞三种情况,与TCP Westwood算法结合,形成了基于ECN的TCPW CM算法,能有效地区分拥塞丢包和无线丢包。仿真实验表明,改进后的算法在高误码率情况下提高了网络利用率和吞吐量,同时仍具有良好的公平性和友好性。     

层次网络中的拓扑压缩算法及性能比较

随着Internet规模的迅速扩大,QoS路由面临复杂度过高的问题。在大规模网络中实现QoS路由的主要困难在于链路QoS信息的频繁更新和QoS最优路径的计算。链路QoS信息(带宽和时延)处于不断变化的状态,需要将这些变化及时地扩散出去以使路由程序做出正确的计算。然而频繁地更新QoS信息无疑会增加网络负载,降低了可扩展性,因此尽量减少链路QoS信息的更新对于提高QoS路由算法的可扩展性起到至关重要的作用。减少链路QoS信息更新的措施包括;减少信息量和减少     

基于移动Agent的分布式路由算法研究

移动Agent技术能较好地适应Internet分布式的特点，将其引入网络分布式路由计算领域是对Internet路由系统的革新。本文指出了传统路由算法存在的问题，提出基于移动Agent的分布式路由算法，就路由表的初始化、通信网络中Agent的数量控制、网络链路故障后路由表的更新、后向Agent的消亡等方面进行了讨论，并进行了仿真实验和性能分析。     

WSN中基于多波束转换天线的网络拓扑控制算法

针对 WSN 中节点分布不均问题,提出采用区域划分策略基于多波束转换天线的网络拓扑控制算法SRADTC.算法通过关键邻居节点数将网络划分为若干个相互重叠的稀疏区域和稠密区域,稀疏区域按最小生成树算法进行拓扑控制,稠密区域按K邻居拓扑控制算法进行拓扑控制.用有边界的Pareto分布建模节点分布,仿真表明：SRADTC算法在保证网络连通性的同时,相比传统拓扑控制算法提高了网络的性能.     

Effective bias reduction methods for passive source localization using TDOA and GROA

For passive source localization based on both TDOA and GROA, this paper proposes two bias reduction methods for the well-known Weighted-Least-Squares (WLS) estimator. We first derive the passive source localization bias from the two-step algebraic closed-form solution. This bias is found to be considerably larger than the Maximum Likelihood Estimator (MLE) and limits the WLS estimator’s practical applications. In this paper, We develop two methods to reduce the bias. The first one called Bias-Subtraction-Method (BSM) directly subtracts the expected bias from the solution of the WLS estimator, and the second one called Bias-Reduction-Method (BRM) imposes a constraint to the equation error formulation to improve the source location estimate. The noise covariance matrix must be known exactly in calculating the expected bias in BSM, and we only need to know the structure of it in BRM. For far-field sources localization when the noise is Gaussian and not too large, both of the two proposed methods can reduce the localization bias effectively and achieve the Cramér-Rao Lower Bound (CRLB) performance very well, and the BRM almost has the same performance as the MLE estimator. Simulations corroborate the performance of the two proposed methods.     

Eh-star方法测试杂散损耗算法的研究

针对Eh-star方法测试电机杂散损耗的算法进行研究。首先,通过与几种测试方法进行对比,揭示Eh-star方法的可行性和优越性。接着,在Eh-star方法的测试原理的基础上,通过公式推导和分析,对此方法的算法进行详细分析,得到杂散损耗的推导公式,为下一步将整个算法嵌入计算机,实现自动数据自动采集和计算奠定基础。     

具有双通道数据包丢失的Delta算子系统故障检测

研究同时存在双通道数据包丢失和时变时延的Delta算子网络控制系统（NCSs）故障检测问题.假定数据包丢失发生在控制器到执行器、传感器至控制器的数据传输过程中，并且利用两个相互独立的伯努利随机变量描述是否发生丢包.将上述的NCSs建模为网络切换系统，提出任意切换律下故障检测滤波器的设计方法.利用线性矩阵不等式（LMIs）方法、Lyapunov-Krasovskii泛函和平均驻留时间等得出所考虑的网络切换系统具备指数均方稳定性的充分条件.证明了所用的网络切换系统满足H_∞性能，并推导出了滤波器参数的显式表达.数值仿真结果验证了所提方法的有效性.     

Hash-based and index-based join algorithms for cube and ringconnected multicomputers

The authors compare the performance of two join algorithms on both cube and ring interconnections for message-based multicomputers, and investigate the effects that the number of processors and the type of interconnection scheme have on the performance. First, the parallel hybrid-hash join algorithm and the parallel join-index join algorithm for both the cube and ring connected multicomputers are presented. The performance of these algorithms is then compared through analytical cost modeling. The result shows that the join-index join algorithm gives good performance only when the join selectivity is very small, and the hybrid-hash join algorithm performs consistently well under most situations. It is shown that the cube topology yields better execution time than the same algorithm on the ring topology. Furthermore, increasing the number of processors has a more significant improvement on the execution time of the cube than for the ring configuration. The applicability of join indexes on the parallel database algorithms is also discussed     

Quaternion-based attitude synchronisation for multiple rigid bodies in the presence of actuator saturation

This paper concentrates on the quaternion-based attitude synchronisation problems of networked rigid bodies under fixed and undirected communication topology without relative angular measurements in the presence of actuator saturation. We first consider the leaderless attitude synchronisation problem with zero final angular velocity. In this case, we not only discuss the performance under the acyclic communication topology with the proposed bounded control algorithm, but also analyse that if there exist cycles in the topology, the proposed bounded algorithm guarantees that all equilibrium points are unstable except that the attitudes of networked rigid bodies achieve synchronisation. We also expand the result to the case of attitude tracking synchronisation with a static leader in the presence of actuator saturation. Next, the tracking synchronisation problem with the desired time-varying attitude is addressed in the presence of actuator saturation. Numerical examples are provided to validate the effectiveness of the proposed bounded schemes and illustrate the performances of multiple rigid bodies.     

Lyapunov-Based Model Predictive Control of Nonlinear Systems Subject to Data Losses

In this work, we focus on model predictive control of nonlinear systems subject to data losses. The motivation for considering this problem is provided by wireless networked control systems and control of nonlinear systems under asynchronous measurement sampling. In order to regulate the state of the system towards an equilibrium point while minimizing a given performance index, we propose a Lyapunov-based model predictive controller which is designed taking data losses explicitly into account, both in the optimization problem formulation and in the controller implementation. The proposed controller allows for an explicit characterization of the stability region and guarantees that this region is an invariant set for the closed-loop system under data losses, if the maximum time in which the loop is open is shorter than a given constant that depends on the parameters of the system and the Lyapunov-based controller that is used to formulate the optimization problem. The theoretical results are demonstrated through a chemical process example.     

存在数据丢包的网络控制系统的控制

将存在数据丢包的网络控制系统描述为跳跃系统。基于一个李雅普诺夫泛函,只需满足4个线性矩阵不等式,便可通过带状态观测的状态反馈控制使闭环系统达到稳定。由于得到的条件不是严格的线性矩阵不等式条件,将不具有严格线性矩阵不等式条件的非凸可行解问题转化为具有严格线性不等式的非线性最小化问题,得到了求解状态反馈控制器增益和状态观测器增益的算法。数值仿真结果验证了该算法的有效性。在所设计的状态反馈控制器的校正作用下,闭环系统的响应是渐近稳定的。