PRED:一种具有优先级自适应的队列管理新算法

现有的拥塞控制采用以TCP为核心的基于窗口技术的端到端控制,具有丢包、响应速度慢等缺陷.本文提出的基于优先级的队列管理算法(PRED),使路由器更加精确地管理队列,算法的主要参数能够适应网络负载的动态变化,有效地克服了现有拥塞控制的缺陷.实验结果表明,在相同的配置下,采用PRED的网络在降低丢包率、减少队列抖动等性能上均优于端到端拥塞控制.     

基于选择性迭代的KSP低轨卫星负载均衡路由方法

低轨卫星(Low Earth Orbit,LEO)系统具有传输时延低、路径损耗小和运行周期短的特点,但大规模卫星部署和地面业务非均匀性的特点,导致卫星网络局部拥塞和局部空闲,为优化卫星网络全局负载均衡和回避拥塞问题,文章提出一种基于选择性迭代的K最短路径算法(Selective Iteration of K Shortest Paths,SI-KSP)。与传统K最短路径方法相比,所提的SI-KSP负载均衡路由方法网络吞吐量增加且丢包率大幅下降;与CA-KSP方法相比,所提方法网络吞吐量相近但丢包率和平均时延均降低。该文所提方法能实现根据全局负载情况选择路径分布,有效避免链路拥塞,达到更优化的负载均衡效果。     

单源多径路由网络拥塞链路识别

针对多径路由带来的端到端测量路径不确定性以及布尔模型不能很好地解决多拥塞链路的问题,该文在识别端到端测量路径的基础上,提出一种基于扩展状态空间的网络拥塞链路识别算法。首先基于探测流时延相关性进行自适应聚类,进而得到各路径与探测流之间的映射关系。其次采用多门限的方式,将具有不同丢包程度的拥塞路径赋予不同的拥塞状态。最后将拥塞链路识别问题转化为一个约束最优化问题,并提出基于扩展状态空间的拥塞链路识别算法(ESSCLI)算法求解该问题。仿真结果表明,ESSCLI算法能够在多种不同网络场景下取得比当前算法更高的拥塞链路检测率。     

WMN中一种基于干扰感知的负载均衡路由协议

无线信道干扰和负载分布的不均衡严重影响无线Mesh网络吞吐量、端到端延时和资源利用率。在已有基于信噪比和邻居节点个数的干扰模型基础上,进一步研究了无线Mesh网络的链路干扰。在综合考虑了无线Mesh网络流间干扰和和流内干扰的基础上,提出路由判据PIL（Path Interfer-ence Level）。在此基础上,提出一种新的基于干扰感知的负载均衡路由协议IA-DSR（Interference-Aware DSR）。IA-DSR考虑无线网络拥塞并选择受到干扰最小的路径。仿真结果表明,在不显著增加开销的情况下,IA-DSR可以有效地提高网络的整体吞吐量,降低网络端到端时延和丢包率。     

一种适用于DTN网络的新型拥塞控制策略

DTN网络具有间断连接特性,信息在传递过程中会经历长或不确定的时延,并且大部分时间不存在端到端的连接,因此普通的拥塞控制策略不能满足DTN网络的需求。文章提出一种基于消息权值和转发时延的拥塞控制策略WDCCS（message Weight and transfer Delay based Congestion Control Strategy）。WDCCS基于消息的传输成功率和传输代价计算消息的保存权值和转发时延。在拥塞发生时,通过对保存权值和转发时延的计算确定丢包策略和出包策略,提高整个网络的交付率并降低整个网络的传输延迟。仿真实验结果表明,在采用Epidemic路由环境下,与默认拥塞控制策略相比,WDCCS使整个网络交付率提升了17.8%,延迟降低了20.3%。     

基于排队时延和丢包率的拥塞控制

作为拥塞度量,排队时延具有很多优点,但仅利用排队时延并不能完全避免丢包,而在链路缓存不足出现丢包时,排队时延已不能有效反应网络拥塞情况。该文提出了一种基于排队时延和丢包率的拥塞控制模型,该模型采用双模控制的方法。在瓶颈链路上有足够缓存时,模型利用排队时延作为拥塞度量,使各流获得稳定的动态性和成比例公平性。当瓶颈路由器上没有足够缓存不可避免要丢包时,模型利用丢包率作为拥塞度量,使各流仍能获得与不丢包情况下相近的流特性。模型在两种模式的切换中保持稳定,实现平滑过渡。     

一种适用于地空通信的负载分布算法

针对地空通信系统传输时延较高、吞吐量较低的问题,提出了一种拥塞感知负载分布（Congestion-aware Load Distribution,CALD）算法。算法通过通信路径质量的变化,估计对应路径的拥塞窗口变化情况,自适应地调整每次子流分配大小,降低端到端的延迟,以应对地空通信的低带宽和高时延特性。同时基于搭建的多路径端到端服务器进行了实验,结果表明,所提算法在吞吐量性能和端到端延迟等方面都优于现有的子流分配算法。     

无线视频错误控制技术研究

无线视频传输中误码和丢包会导致视频质量的严重下降,研究了视频传输中的错误控制相关技术。对已有的无线视频错误控制方法进行了详细分析,在此基础上提出了一种更加有效的无线视频传输中的错误控制框架。将无线误码丢包和拥塞丢包准确区分,改进了以往算法带宽估计公式不准确的问题。并且对视频内容根据在解码端重要性的不同区分保护。在错误控制的同时进行了拥塞控制。     

移动自组网中新的智能丢包区分机制

为了有效区分移动自组网中由于网络拥塞、路由切换和链路错误引起的丢包,通过模糊计算的综合评判模型,在发送端综合端到端往返延时、短期的吞吐量以及乱序数据包3个网络观测参数进行判断。仿真结果表明智能丢包区分算法对丢包原因的判断取得了较好的效果。基于该智能丢包区分算法的TCP改进方案TCP-Fuzzy,能够根据判断出的丢包原因采取恰当的拥塞控制策略,在各种不同的网络环境下都有较好的性能表现。     

无线adhoc网络中的多径源路由

本文针对无线ad hoc网络提出了一种基于DSR(动态源路由)的路由算法,多径源路由(MSR).MSR对DSR中的路由搜索和路由维护机制进行了扩展,用来解决多径路由问题.本文还提出,在多条路径之间基于测量的RTT进行负载分配.仿真结果表明,MSR在只增加少量网络开销的情况下,提高了TCP和UDP的投递率,降低了丢包率,并减少了端到端之间的延迟以及队列长度,从而有效地减少了网络拥塞.     

一种Iub口流控策略在HSPA＋系统中的应用

为了提高系统无线资源的利用率和网络性能,提出一种基于过准入的HSPA＋系统的Iub口流量控制策略。通过Iub口拥塞检测和L2流控处理,避免拥塞和丢包,提高传输利用率。仿真结果表明,该流量控制策略能有效降低拥塞,提高网络性能,并能保证业务的公平性。     

视频监视系统中视频质量优化策略研究

为了对视频监视系统中监视质量的进行优化,提出了3种优化控制策略：零拷贝缓冲区策略、网络拥塞抑制策略、编解码速率协调策略。零拷贝缓冲区策略降低了终端负载,提高了系统处理能力,网络拥塞抑制策略有效地减少了丢包率,编解码速率协调策略平衡了系统延时与流畅性。实验测试结果显示,随着监视时间的增加,优化后系统时延基本稳定、丢包率显著减少、视频播放流畅,系统性能满足一般应用需要。     

Congestion control for multimedia services

The problem of congestion control in high-speed networks for multimedia traffic, such as voice and video, is considered. It is shown that the performance requirements of high-speed networks involve delay, delay-jitter, and packet loss. A framing congestion control strategy based on a packet admission policy at the edges of the network and on a service discipline called stop-and-go queuing at the switching nodes is described. This strategy provides bounded end-to-end delay and a small and controllable delay-jitter. The strategy is applicable to packet switching networks in general, including fixed cell length asynchronous transfer mode (ATM), as well as networks with variable-size packets     

Adaptive Load-Aware Congestion Control Protocol for Wireless Sensor Networks

Congestion control in wireless sensor networks (WSNs) is crucial. In this article, we discuss congestion control and the adaptive load-aware problem for sensor nodes in WSNs. When the traffic load of a specific node exceeds its the available capacity of the node, a congestion problem occurs because of buffer memory overflow. Congestion may cause serious problems such as packet loss, the consumption of power, and low network throughput for sensor nodes. To address these problems, we propose a distributed congestion control protocol called adaptive load-aware congestion control protocol (ALACCP). The protocol can adaptively allocate the appropriate forwarding rate for jammed sensor nodes to mitigate the congestion load. Through the buffer management mechanism, the congestion index of neighboring sensor nodes, and an adjustment of the adaptive forwarding rate, the degree of congestion is alleviated markedly. The performance in allocating the forwarding rate effectively to neighboring sensor nodes also improves. The ALACCP can avoid packet loss because of traffic congestion, reduce the power consumption of nodes, and improve the network throughput. Simulation results revealed that the proposed ALACCP can effectively improve network performance and maintain the fairness of networks.     

A Novel Congestion Detection Scheme in TCP Over OBS Networks

This paper introduces a novel congestion detection scheme for high-bandwidth TCP flows over optical burst switching (OBS) networks, called statistical additive increase multiplicative decrease (SAIMD). SAIMD maintains and analyzes a number of previous round-trip time (RTTs) at the TCP senders in order to identify the confidence with which a packet loss event is due to network congestion. The confidence is derived by positioning short-term RTT in the spectrum of long-term historical RTTs. The derived confidence corresponding to the packet loss is then taken in the developed policy for TCP congestion window adjustment. We will show through extensive simulation that the proposed scheme can effectively solve the false congestion detection problem and significantly outperform the conventional TCP counterparts without losing fairness. The advantages gained in our scheme are at the expense of introducing more overhead in the SAIMD TCP senders. Based on the proposed congestion control algorithm, a throughput model is formulated, and is further verified by simulation results.      

Upstream congestion control in wireless sensor networks through cross-layer optimization

Congestion in wireless sensor networks not only causes packet loss, but also leads to excessive energy consumption. Therefore congestion in WSNs needs to be controlled in order to prolong system lifetime. In addition, this is also necessary to improve fairness and provide better quality of service (QoS), which is required by multimedia applications in wireless multimedia sensor networks. In this paper, we propose a novel upstream congestion control protocol for WSNs, called priority-based congestion control protocol (PCCP). Unlike existing work, PCCP innovatively measures congestion degree as the ratio of packet inter-arrival time along over packet service time. PCCP still introduced node priority index to reflect the importance of each sensor node. Based on the introduced congestion degree and node priority index, PCCP utilizes a cross-layer optimization and imposes a hop-by-hop approach to control congestion. We have demonstrated that PCCP achieves efficient congestion control and flexible weighted fairness for both single-path and multi-path routing, as a result this leads to higher energy efficiency and better QoS in terms of both packet loss rate and delay.     

一种新的卫星网络传输控制协议

为了解决TCP协议在卫星通信网络中性能差的问题,该文提出了一种适合卫星网络的新型传输控制协议TP-Satellite。为了加速在连接开始阶段拥塞窗口(cwnd)增涨速度,该协议不再采用传统的Slow Start策略,而是采用一种新的窗口增涨策略超起始策略。为了将误码与网络拥塞造成的数据丢失区分开,协议还采用基于不同优先级IP数据交错发送的丢失判断策略。另外,协议采用了主动周期应答策略。通过理论分析和仿真比较,TP-Satellite协议能够迅速提升数据发送速率和有效地区分数据丢失原因,明显提高前向链路的吞吐量,同时降低反向链路的带宽占用。     

An Improved Algorithm of Nonlinear RED Based on Membership Cloud Theory

Concerning on the shortcoming and com-plexity of Random early detection (RED) algorithm in net-work congestion control, a new RED algorithm based on the Hemi-Rise Cloud model (CRED) was proposed, non-linear packet loss strategy was used, and sensitivity and un-certainty of parameters were improved. As a result, queue length could be kept stable in the neighborhood of ref-erence value. Network congestion was well controlled and network resource was used effectively. The stability of the algorithm was studied and the experimental results showed that the proposed algorithm could improve the stability, and had better performance than the RED and Adaptive RED (ARED) algorithms.     

分布式认知无线电网络多路径路由协议研究综述

为了深入研究分布式认知无线电网络的多路径路由问题,阐述了分布式认知无线电网络基本特征以及多路径路由设计面临的问题与挑战。分布式认知无线电网络多路径路由采用多路径并行传输,可有效降低传输时延、增加网络吞吐量与传输可靠性、实现网络负载均衡。根据路由优化目标不同,从吞吐量、带宽、干扰、时延、负载均衡和路由发现六方面对近年来多路径路由协议的主要研究成果进行了分类,然后逐类对多路径路由协议进行了分析和讨论,最后分别从分布式认知无线电网络基本特征的适应性与多路径路由协议特征两个方面进行了比较,并展望了分布式认知无线电网络多路径路由协议需进一步研究的方向。     

Research on adaptive beacon message broadcasting cycle based on vehicle driving stability

Ensuring smooth communication by fixed-cycle message beaconing in vehicular environments is necessary to address vehicles safety. However, fixed-cycle beacon messages cannot accommodate the characteristics of fast vehicle speeds and variable network topologies and can cause problems such as channel congestion when traffic density is too high. Therefore, in order to realize safe and reliable information transmission between vehicles, this paper proposes a strategy for adaptive update of beacon message cycle based on vehicle driving stability. It is based on two rules: one is that the vehicle position prediction error is defined as an unstable vehicle, and the small error is defined as a stable vehicle; and the other is that the adaptive beacon message cycle is ranged, which is determined according to the channel load capacity. The experimental results show that the strategy can effectively avoid the channel congestion problem and improve the driving safety of the vehicle. Compared with the fixed-cycle beacon message, the communication delay is reduced by about 10%, the packet loss is reduced by about 22%, and the energy consumption is reduced.