一种考虑节点拥塞情况的DTN概率路由算法*

容迟网络是一种新型网络,其概率路由算法根据历史相遇频率对相遇概率进行计算与更新,通过相遇概率判断是否转发报文。当节点缓存受限时,在网络中采用概率路由算法使得节点很容易发生拥塞,对报文的传送产生影响。为了减小拥塞对概率路由算法的影响,提出了一种考虑节点拥塞情况的概率路由算法,将节点相遇的概率和节点拥塞的情况综合起来,得到一个报文的递交概率,降低了由于拥塞对网络性能的影响,提高了报文的递交率,减小了报文在缓存中排队等候的时间。仿真结果表明,与传统的概率路由算法相比,在改进后的概率路由算法中报文递交率显著提高,平均延迟也在降低。     

直线引导的Torus结构路由算法

为了提高片上网络在Torus拓扑结构下的路由通信效率,提出了一种基于直线引导思想的路由算法Tline。该路由算法将Torus拓扑结构的片上网络拓展为类似Mesh结构的坐标平面,以数据包的源节点和目的节点构成的直线为路由转发方向,并根据周围邻近节点的拥塞状况选择传输路径方向实现部分自适应路由。实验结果表明,与XY、OE路由算法相比,在热点流量模式下Tline路由算法具有较好的路由性能,且平均能耗降低约8%。     

ERC2:具有拥塞控制策略的DTN传染路由方法

针对延迟容忍网络（DTN）拓扑结构动态变化和节点存储空间有限的问题,提出一种具有拥塞控制策略的DTN传染路由（ERC²）方法。该方法基于一种动态存储状态模型（DSSM）,节点可通过感知网络状况动态调整节点半拥塞状态的门限降低网络发生拥塞的可能性,增加ACK索引以及消息管理队列,使节点存储状态随着网络负载的随机变化而动态更新并主动删除冗余包,并根据不同拥塞状态结合传染路由和Prophet路由的优点选择单一或混合模式进行消息转发,从而达到预防、避免、解除拥塞的目的,实现节点自适应缓存管理以及网络的动态拥塞控制。在模拟器ONE上采用Working Day Movement模型进行仿真,其中与Prophet相比,ERC²方法在消息递交率上提高66.18%,平均时延降低48.36%,转发次数提高22.83%。仿真结果表明,在拥塞程度不同的场景中,ERC²与Epidemic、Prophet路由算法相比具有更好的网络性能。     

基于蚁群算法的容迟网络概率路由算法

容迟网络的概率路由算法根据节点与信宿节点之间相遇的概率判断是否转发报文,但相遇概率不能真正准确地反映报文递交成功的概率.针对该问题,提出一种基于蚁群算法的概率路由算法,结合蚁群算法的基本原理改进信息素浓度的更新机制和报文转发机制.仿真结果表明,与传统的概率路由算法相比,改进后的概率路由算法报文递交率较高,开销率较小.     

直线引导的片上网络路由算法

为了提高片上网络路由通信效率及降低能耗,提出一种新颖的路由算法——Beeline路由算法.该算法以数据包源点和终点构成的直线为传输引导方向,首先计算当前路由节点所在的网格其他3个节点到该直线的距离,获得离该直线距离最近的路由节点;然后计算最近路由节点与当前路由节点的路由跳数,根据跳数及邻近路由节点的拥塞状况选择最佳传输路由节点;最后将路由算法与基于结构级模型的No C能耗模拟软件相结合.与XY,OE路由算法进行比较的实验结果表明,Beeline路由算法具有较好的路由性能,并且平均能耗下降约6%.     

多媒体传感器网络中跨层优化的实时路由协议

提出一种能量均衡的实时路由算法。通过MAC层和路由层协同设计,在路由转发策略中,充分考虑节点的剩余能量和可靠性。在拥塞控制机制中,基于节点的缓存队列长度并结合收发数据速率来检测拥塞。仿真实验显示,该路由算法有效地保证了数据的实时传输,降低了通信能量的开销。     

DTN中基于时间因素的拥塞感知路由算法

为了解决散发等待路由算法中,中继节点的选择存在盲目性的问题,提出一种基于时间因素的拥塞感知路由算法CARA。该算法考虑时间因素对转发概率的影响,改进Prophet算法中的转发概率。根据改进的转发概率选择中继节点,动态分配报文转发数目,并以拥塞感知自适应的方式实现拥塞控制的优化。仿真结果表明,CARA算法和网络投递率及延迟表现最好的CS-DTN算法相比,投递率提高了10.21%,延迟降低了7.05%,同网络开销表现最好的BSW算法相比,开销降低了8.16%。     

移动自动网中基于位置和节能的路由算法研究

综合考虑了移动自组网中投递成功率及网络连通寿命两项性能指标,提出一种基于位置和节能的路由算法,该算法根据下一跳节点所处区域的节点稠密度、下一跳节点的剩余能源、转发功耗和转发效果决定分组转发路由.讨论了实现该路由算法所需要的局部信息收集机制.最后介绍了算法的仿真实验及测试结果.实验结果表明,在能源受限的移动自组网中,所提出的路由算法在分组投递成功率和网络连通寿命方面均取得很好的效果.     

MRABM:一种新的基于mesh结构的多径路由算法

针对移动AdHoc网络提出了一种新的基于mesh结构的多径路由算法MRABM(MultipathRoutingAlgorithmBasedonMeshStructure),该算法采用目的节点建立和更新mesh结构的机制。该算法不仅为每个源节点、中间节点提供了到目的节点最优路径,而且为每个节点建立了到目的节点的多条路径。当节点移动造成链路断开时,该算法能避开断开的链路,迅速沿其它路径转发数据,不需要路由修复和路由重建过程,从而降低了丢包率和端到端的延时。对大流量数据的传输,该算法能有效利用网络资源,减少网络拥塞。因此该算法能很好地适应网络拓扑结构的动态变化。     

一种区分服务的DTN概率路由算法

针对DTN网络中不同优先级的数据包需要区分服务的问题, 提出了区分服务的概率路由算法SDRP。该算法提出了参考概率这一概念, 相遇节点针对不同的数据包优先级定义了不同的参考概率, 若相遇节点的参考概率大于发送节点的转发概率则将数据包转发, 否则不转发。仿真表明, SDRP算法使不同优先级数据包的递交率呈层次化分布, 高中低优先级数据包的递交率由高到低依次排列。该算法使DTN网络在不改变原有网络通信性能的基础上, 较好地实现了根据数据包优先级的不同而区分服务的功能。     

The role of congestion in probabilistic broadcasting for ubiquitous wireless multi-hop networks through mediation analysis

Broadcast schemes play an important role in the performance of mobile ad hoc networks, which are a clear example of ubiquitous wireless multi-hop networks where nodes collaborate in a distributed way. They are widely used as a dissemination mechanism and as a part of the discovery phase of routing protocols. The simple flooding algorithm is the usual mechanism employed in mobile ad hoc networks, but its inefficiency has been demonstrated in congested scenarios due to the high number of collisions and contentions. However, these problems can be partially alleviated by using a probabilistic broadcast approach in which every node forwards the incoming packets according to a certain forwarding probability. In this paper, we use a simple probabilistic broadcast protocol to evaluate the effects of congestion on the performance of broadcasting in ad hoc networks through a mediation analysis. We hypothesize that the congestion mediates in the relationship between the forwarding probability (independent variable) and the output metric (dependent variable). We consider several output metrics according to the application of the broadcasting protocol such as reachability, broadcasting delay, packet delivery fraction and end to end delay. The simulation results show the existence of the mediating effects and how such effects may be counterbalanced depending on the target use of the probabilistic broadcast scheme.     

GeoSpray: A geographic routing protocol for vehicular delay-tolerant networks

Vehicular networks are characterized by a highly dynamic network topology, and disruptive and intermittent connectivity. In such network environments, a complete path from source to destination does not exist on the most part of the time. Vehicular delay-tolerant network (VDTN) architecture was introduced to deal with these connectivity constraints. VDTN assumes asynchronous, bundle-oriented communication, and a store-carry-and-forward routing paradigm. A routing protocol for VDTNs should make the best use of the tight resources available in network nodes to create a multi-hop path that exists over time. This paper proposes a VDTN routing protocol, called GeoSpray, which takes routing decisions based on geographical location data, and combines a hybrid approach between multiple-copy and single-copy schemes. First, it starts with a multiple-copy scheme, spreading a limited number of bundle copies, in order to exploit alternative paths. Then, it switches to a forwarding scheme, which takes advantage of additional contact opportunities. In order to improve resources utilization, it clears delivered bundles across the network nodes. It is shown that GeoSpray improves significantly the delivery probability and reduces the delivery delay, compared to traditional location and non location-based single-copy and multiple-copy routing protocols.     

On improving the efficiency of truthful routing in MANETs with selfish nodes

In Mobile Ad Hoc Networks (MANETs), nodes depend upon each other for routing and forwarding packets. However, nodes belonging to independent authorities in MANETs may behave selfishly and may not forward packets to save battery and other resources. To stimulate cooperation, nodes are rewarded for their forwarding service. Since nodes spend different cost to forward packets, it is desirable to reimburse nodes according to their cost so that nodes get incentive while the least total payment is charged to the sender. However, to maximize their utility, nodes may tell lie about their cost. This poses the requirement of truthful protocols, which maximizes the utility of nodes only when they declare their true cost. Anderegg and Eidenbenz recently proposed a truthful routing protocol, named ad hoc-VCG. This protocol incurs the route discovery overhead of O(n³), where n is the number of nodes in the network. This routing overhead is likely to become prohibitively large as the network size grows. Moreover, it leads to low network performance due to congestion and interference. We present a low-overhead truthful routing protocol for route discovery in MANETs with selfish nodes by applying mechanism design. The protocol, named LOTTO (Low Overhead Truthful rouTing prOtocol), finds a least cost path for data forwarding with a lower routing overhead of O(n²). We conduct an extensive simulation study to evaluate the performance of our protocol and compare it with ad hoc-VCG. Simulation results show that our protocol provides a much higher packet delivery ratio, generates much lower overhead and has much lower end-to-end delay.     

Maximum data delivery probability-oriented routing protocol in opportunistic mobile networks

Some recent studies utilize node contact patterns to aid the design of routing protocol in Opportunistic Mobile Networks (OppNets). However, most existing studies only utilize one hop contact information to design routing protocol. In order to fully utilize nodes’ collected contact information to improve the performance of data forwarding, in this paper we focus on exploiting node contact patterns from the multi-hop perspective. We first give the definition of opportunistic forwarding path, and propose a model to calculate the maximum data delivery probability along different opportunistic forwarding paths. Second, based on the maximum data delivery probability, we propose a novel approach to improve the performance of data forwarding in OppNets based on two forwarding metric. The proposed forwarding strategy first manages to forward data copies to nodes have higher centrality value at the global scope. Afterwards, maximum data delivery probability to the destination is evaluated, to ensure that data is carried and forwarded by relays with higher capability of contacting the destination. Finally, extensive real trace-driven simulations are conducted to compare the proposed routing protocol with other existing routing protocols in terms of delivery ratio and delivery cost. The simulation results show that our proposed routing protocol is close to Epidemic Routing in terms of delivery ratio but with significantly reduced delivery cost. Additionally, our proposed routing protocol outperforms Bubble Rap and Prophet in terms of delivery ratio, and the delivery cost of our proposed routing protocol is very close to that of Bubble Rap.     

社会感知多副本车载自组织网络机会路由协议

为提高车载自组织网络(vehicular Ad hoc networks, VANETs)中消息投递的效率, 提出了一种社会感知多副本车载自组织网络机会路由协议(SAMOR)。协议结合了车载自组织网络中节点的社会性特点和多副本路由方案的优势, 采用携带—存储—转发的机会路由方式进行消息投递。利用节点间的相遇历史区分社区节点和全局节点, 并使用所提出的节点社区中心性和网络中心性的度量方法, 得到了节点的效用。在路由过程的扩散阶段, 节点间按效用分配副本, 在转发阶段, 副本继续向效用高的节点转发。仿真结果表明, SAMOR实现了较高的消息投递成功率和较低的延迟。     

ICN中改进的拥塞控制和请求转发策略研究

针对信息中心网络(ICN)中终端用户体验不佳,网络资源利用率低等不足,对ICN中联合多径拥塞控制和请求转发问题展开研究。将该问题看成是以用户吞吐量最大化和总体网络成本最小化为目标的全局优化问题。通过分解策略解决这一全局优化问题,为接收机确定一组最优拥塞控制策略,为网络节点确定一组分布式动态请求转发算法。为了评估本文设计的性能,使用CCNx部署本文协议,并设置测试床用于大规模实验仿真。不同网络场景下的实验评估证明了本文方案的效率和全局公平性,达到最优方案的预期效果,即使面对路径内缓存和网络拥塞导致的延时不确定性也具有稳定的性能。     

基于信任机制的无线传感器网络可靠传输路由协议

在无线传感器网络中,针对异常事件监测时会出现大量数据发送引起网络拥塞、数据包无法可靠传输的问题,提出一种基于信任机制的可靠传输路由协议（RTRPT）。该协议提出了梯度分簇模型以选取簇头节点。在无异常事件发生时,通过转发能量阈值找出传输数据的邻居节点,进行数据传输。同时对这些节点进行转发概率与历史信任度计算得到直接信任度,再通过这些节点交互间接评价得到间接信任度。将直接信任度、间接信任度、距离度量和剩余能量作为评价指标,量化后通过熵权法得到邻居节点的综合信任。在异常事件发生时,节点仅需选择综合信任度最大的邻居节点作为转发节点,建立路由路径。使用OMNeT++进行仿真验证,RTRPT与TSRP、ESRT相比,在传输大量数据包时节点丢包率分别降低69.4%、52.7%;节点传输延迟分别降低53.6%、34.8%;网络生命周期分别延长32.5%、15.7%。仿真结果表明,RTRPT能有效减少丢包、降低传输延迟、延长生命周期。     

An energy-efficient,transport-controlled MAC protocol for wireless sensor networks

In wireless sensor networks (WSNs), one major cause of wasted energy is that the wireless network interface is always on to accept possible traffic. Many medium access control (MAC) protocols therefore adopted a periodic listen-and-sleep scheme to save energy, at sacrifice of end-to-end latency and throughput. Another cause is packet dropping due to network congestion, necessitating a lightweight transport protocol for WSNs. In this paper, we suggest a transport-controlled MAC protocol (TC-MAC) that combines the transport protocol into the MAC protocol with the aims of achieving high performance as well as energy efficiency in multi-hop forwarding. Although TC-MAC also works through a periodic listen-and-sleep scheme, it lowers end-to-end latency by reserving data forwarding schedules across multi-hop nodes during the listen period and by forwarding data during the sleep period, all while increasing throughput by piggybacking the subsequent data forwarding schedule on current data transmissions and forwarding data consecutively. In addition, TC-MAC gives a fairness-aware lightweight transport control mechanism based on benefits of using the MAC-layer information. The results show that TC-MAC performs as well as an 802.11-like MAC in end-to-end latency and throughput, and is more efficient than S-MAC in energy consumption, with the additional advantage of supporting fairness-aware congestion control.     

多力驱动的无线传感器网络QoS路由协议

本文提出一种基于多势场力的QoS感知的无线传感器网络路由MFQR。为了更有效的适应网络环境的变化,MFQR中节点自适应的选取满足时延和投递率要求的转发节点。在网络状况良好时,协议通过深度-能量混合势场力选取转发节点集合,以均衡节点能耗;当网络负载加重时,协议通过深度-队列长度混合势场力选取转发节点集合,以避开拥塞区域。仿真结果表明,MFQR可以有效地适应实时性、可靠性要求的变化,同时提高了网络吞吐量,均衡了节点能耗,延长了网络生命周期。