Ad Hoc网络中一种基于自裁减的广播算法

为解决简单泛洪式广播算法所引起的AdHocN络的广播风暴问题,提出了一种基于自裁减的广播算法。算法根据自裁减广播策略,通过设定延时机制和优先转发机制对网络节点是否需要转发广播包进行判定。最后,将算法应用于AODV协议,并与标准AODV协议在不同节点最大移动速度的场景下进行了转发节点数、到达率、端到端平均时延和归一化路由开销等参数的比较,以验证提出算法的有效性。     

应用于Ad Hoc网络中的密度自适应泛洪广播策略

针对Ad Hoc网络中泛洪广播机制可能带来的大量资源浪费问题,本文提出了一种新型的泛洪广播机制——密度自适应的泛洪广播策略.该策略根据发送节点的邻节点密度,以最密集节点的一次发送将覆盖较多节点为出发点,选取尽可能少的邻节点作为转发节点,减少了分组在网络中的重复传输,大大改善了网络的性能.仿真结果表明,密度自适应泛洪广播策略的性能明显优于普通的泛洪广播策略.     

一种基于能耗均衡的ZigBee网络高效混合路由算法

针对目前ZigBee网络混合路由算法寻找开销偏大、能耗不均的问题,提出一种高效混合路由算法( EHCA)。通过采用跨层泛听与优先使用深度大、剩余能量多的节点进行路由的方式,减少部分泛洪寻路分组的转发,均衡节点能耗。仿真结果表明,EHCA的节点能耗均衡、路由开销和网络寿命等性能均优于混合路由算法和树路由算法。     

多跳无线网络中无需邻节点信息的空间覆盖广播算法

针对多跳无线网络中广播的转发冗余问题,该文提出了一种无需邻节点信息的空间覆盖广播(Space-Covered Broadcast,SCB)算法。SCB算法通过优化转发节点的空间分布达到利用最少数目的转发节点实现对网络空间的覆盖,从而在保证较高送达率的同时明显降低了广播的转发次数。由于无需邻节点信息和网络拓扑信息,SCB算法降低了带宽和存储计算等开销;并且,转发节点的选择由接收节点通过延时转发机制来完成,因而SCB算法能够自动适应信道状况,避免信道变化造成的传输错误。仿真结果表明：该算法在不同的节点密度和网络负载条件下能够明显提高广播的传输效率。     

一种改进的候选邻居节点的VANET路由协议

车载自组网的大多路由协议都使用泛洪算法来传递路由更新包,而基本的泛洪算法会有很高的重传率,高重传率直接会导致数据包的碰撞以及网络的阻塞,这些都极大影响了网络的性能。为此,提出一种高效泛洪算法,在发送的RREQ中包含4个最稳定候选邻居节点的地址,只有这4个节点对收到的RREQ进行转发,其余节点则丢弃。仿真结果表明该算法降低了丢包率,提高了网络的吞吐量。     

支持延时约束的覆盖多播路由协议的研究

研究有度和延时约束的覆盖多播路由问题,提出了一个新的覆盖多播路由协议-延时受限的树协议(DBTP)。该协议采用分布式和树优先的策略,使多播组成员之间能自组织地构建一棵基于源的覆盖多播树。DBTP协议采用了一种新的启发式局部优化算法,通过调节启发因子,能灵活地在延时和代价之间进行折衷。仿真实验表明,无论在静态还是动态节点模型下,选择适当的启发参数,DBTP都能获得较高的节点接纳率。     

基于泛洪约束的MANET按需组播路由协议

降低路由控制开销是MANET网络组播路由协议节省节点能量,提高带宽利用率的关键因素之一。本文研究了组播路径近邻节点对路由维护的作用以及链路的连通性,分别提出了一个新的泛k-洪约束算法和一个混合泛洪模式。基于泛k-洪约束算法和混合泛洪模式,提出一个新的按需组播路由协议ODMRP-CF,ODMRP-CF协议通过选择k-路由近邻节点转发泛洪分组来提高泛洪效率。ODMRP-CF协议不仅保持了ODMRP协议所具有的简单,对节点移动鲁棒性好的优点,而且有效地降低了ODMRP-CF协议的控制开销。     

基于无线网络数据广播算法的多媒体信息传输技术与应用

随着无线网络的迅猛发展,传统声音、文字通讯模式已发生巨大的改变,本文以无线网络数据广播算法为基础,对多媒体信息传输技术进行了研究.通过分析TFB算法、节点选择、转发节点选择、相近转发节点的消除,建立了基于无线网络数据TFB三点转发广播算法的多媒体交互系统构架,采用UDP+ CDN传输协议中转模式,在Windows XP上,采用TFB三点转发广播算法,进行无线移动网络多媒体发包与丢包的测试,通过CDN服务器,连续发5 000个包,实验结果表明,两次发包间不延时,无线网络未出现丢包现象,丢包现象主要发生在发送节点侧与接受节点侧,丢包范围在0.3％ ～2.3％之间,这对用户体验不会造成影响.     

基于路径优先度的VoIP中继选择算法

在覆盖网络中为VoIP业务计算端到端路径时,需要保证该路径的时延小于150 ms;由于覆盖网络中反三角现象普遍存在,因此,为了保证VoIP业务时延要求,应用中继技术计算从源节点通过中继节点到目的节点的路径,取代端到端路径,成为覆盖网络提供VoIP业务的关键技术。基于已有中继技术存在的部署难、未考虑路径差异及结果不是最优等问题,提出基于路径优先度的VoIP中继选择算法,该算法首先提出路径优先度的概念,描述时延和默认IP路径的差异性,再基于路径优先度构建中继路由表,在中继路由表中挑选最优中继节点;提出基于路径优先度的两跳中继选择算法进一步减少转发时延。仿真证明所提算法能够减少VoIP业务的传输时延,提升VoIP业务的用户体验。     

一种多跳无线网络中的高效广播算法

广播是多跳无线网络中的一种基本操作。现有的广播算法中普遍存在转发冗余过多的问题。该文首先分析了覆盖网络所需的最少转发节点数目,然后以此为基础,提出了一种简单高效的广播算法。该算法中,每个节点最多只需选择3个转发节点,从而明显地减少了广播的转发次数,提高了节点能量和网络资源的利用率;同时,所有转发节点实现了对整个网络接近双重的覆盖,能够保证较高的传输可靠性;此外,对不同的网络规模和拓扑的动态变化,该算法具有较好的可扩展性。仿真结果显示,该算法在多种常见的网络环境下具有比现有方法更优越的性能。     

A novel convex hull-based flooding scheme using 1-hop neighbor information for mobile ad hoc networks

Flooding is one of the most essential and commonly used operations in mobile ad hoc networks. Different sender-based and receiver-based flooding algorithms have been presented separately in the literature. To integrate the advantages of sender-based and receiver-based flooding algorithms, this paper proposes a novel joint 1-hop neighbor information-based flooding scheme that consists of two sub-algorithms: the sender-phase algorithm and the receiver-phase algorithm. The sender-phase algorithm of our flooding scheme helps a node select a subset of its 1-hop neighbors to forward the flooding message. Based on the convex-hull concept, this algorithm selects forwarding nodes with the highest contribution to flooding message dissemination. On the other hand, the receiver-phase algorithm complements the sender-phase algorithm, allowing our flooding scheme to guarantee full delivery. We prove that our flooding scheme requires lower time complexity O(n log h), where h is the number of forwarding nodes, than the best known 1-hop neighbor information-based flooding algorithms proposed by Liu et al. and Khabbazian et al. Additionally, to alleviate the local optimal problem caused by sender-based flooding algorithms, we relax the full delivery requirement and modify our flooding scheme to discard more redundant rebroadcasting operations. Simulation experiments are conducted to compare the performance of our flooding schemes with those of Liu et al.??s and Khabbazian et al.??s flooding algorithms. The simulation results show that our flooding schemes accomplish a lower ratio of broadcasting nodes and a higher message delivery ratio simultaneously under various network conditions. Moreover, since our flooding schemes have lower ratios of broadcasting nodes, they incur fewer packet collisions on the network. Consequently, message disseminations applying our flooding schemes have a smaller effect on other transmissions of different message types.     

一种基于QoS的空间延迟/中断容忍网络拥塞控制方法

为缓解网络拥塞对空间延迟/中断容忍网络产生的影响,该文提出一种基于QoS的网络拥塞控制算法。该算法包括接触拥塞判断和基于QoS的数据转发两种机制,分别从接触剩余可用容量和节点剩余存储空间两方面对每一段接触的拥塞程度进行预测,将接触划分为不同的拥塞等级。在计算路由时,以整段路径中所包含接触的最高拥塞等级为该路径的拥塞等级,并根据该拥塞等级发送不同优先级的数据。实验表明,基于QoS的拥塞控制算法可以提高低优先级数据的传递率并在节点存储空间不足时降低最高优先级数据的传递时延。     

基于模糊流感知的动态优先公平调度算法

为适应网络的动态性,提高调度公平性和资源效率,流感知优先公平调度机制需要动态的多业务区分转发。与链路负载状态相关的模糊流感知能够实现路径上的一致性业务区分,而基于模糊流感知的动态优先公平调度算法通过调整优先队列负载门限在流式流和弹性流之间实现转发优先权的动态交替,在链路轻载时实现不同流间的相对公平调度,在链路重载时则强调实时业务的绝对优先权以保证其时延要求。算法公平性分析和仿真计算显示提出算法的动态区分转发通过适度增加优先业务队长能够大幅度提高弹性流的接纳率,具有较高的链路平均吞吐量和资源效率。     

Environment-Driven Opportunity Forwarding Cross-Layer Optimization for Ubiquitous Wireless Networks

In this paper, an environment-driven cross-layer optimization scheme is proposed to maximize packet forwarding efficiency. The proposed algorithm is aimed to improve the performance of location-based routing protocol in respect of greedy forwarding and avoid void regions for ubiquitous wireless networks. In greedy forwarding mode, we use a new routing metric IAPS which can estimate the forwarding distance, link quality and the difficulty of channel access during the process of the next hop node selection. When the packet forwarding comes into a local minimum, the proposed scheme uses an opportunistic forwarding method based on competitive advantage to bypass the void regions. NS2 simulation results indicate that the proposed algorithm can improve network resource utilization and the average throughput, and reduce congestion loss rate of wireless multi-hop network comparison with existing GPSR algorithm.     

面向船舶AIS自组织网络的地理位置路由算法

针对船舶自动识别系统（Automatic Identification System,AIS）的自组织网络路由算法设计问题,提出了一种基于优化的贪婪边界无状态路由（Greedy Perimeter Stateless Routing,GPSR）的技术方案。该方案利用AIS时分多址接入协议,为消息报文提供信道接入方法。首先,设计了位置报文的自适应转发策略,使船舶节点根据网络环境自主决策位置报文的转发行为;其次,通过缩小GPSR贪婪转发的选择范围,减少了因节点运动导致的边缘路由失败情况。仿真结果表明,所提方案实现了AIS船舶节点的有效组网。与现有转发策略相比,自适应转发策略降低92.7%的位置报文转发量,并降低了79.6%的时隙冲突率,可有效提高网络资源的利用率。      

A Study on Differentiated Service Queuing Scheme with an Overflow Buffer Allocation Within a UMTS Core Network

According to the QoS features of the four types of UMTS traffic, this study proposes a priority-based queuing scheme to support differentiated services among all UMTS traffic; it bases on packet transmission priorities of four types of UMTS traffic to handle packets forwarding in a gateway within a UMTS core network. In the proposed queuing scheme, a static dedicated logical queuing buffer allocation and a dynamic overflow buffer allocation are used to support packet enqueuing/dequeuing jobs. In this study, the ns2 network simulator is used as a simulation platform and different categories of simulation scenarios are executed. Moreover, the IETF DiffServ scheme is used as a comparison to understand the packet forwarding performance of the proposed scheme. By analyzing simulation data, two important points can be drawn. The proposed queuing scheme supports a differentiated packet forwarding behavior among four types of UMTS traffic. And, the differentiated packet forwarding behaviors with the proposed queuing scheme are similar to the packet forwarding behavior with the IETF DiffServ scheme.     

无线多跳网络中机会路由效率增强研究(英文)

Opportunistic routing(OR) is an effective way to guarantee transmission reliability in wireless multi-hop networks.However,little research focuses on transmission efficiency.Thus,an analytical model based on open queuing network with Markov chains was proposed to evaluate the efficiency.By analyzing two typical ORs,we find duplicate transmission and collision avoidance overhead are the root reasons behind inefficiency.Therefore,a new scheme called dual priority cooperative opportunistic routing(DPCOR) was proposed.In DPCOR,forwarding candidates are configured with dual priority,which enables the network to classify forwarding candidates more effectively so as to reduce the back-off time and obtain more diversity gain.Theoretical analysis and simulation results show DPCOR achieves significant performance improvement with less time overhead compared with traditional routings and typical ORs.     

一种面向实时业务的Ad Hoc网络MAC协议

为降低AdHoe网络中实时业务的端到端时延,提出了基于802．11DCF的改进协议。协议采用3种机制降低实时业务的时延：面向路径的连续转发机制将RTS中的转发信息携带在ACK中发送,给实时业务提供较高的接入优先级;标签交换机制使得中间节点可以在MAC层获取转发信息,加快了实时业务数据包的转发速度;重传控制机制减少了无效传输的超时数据包。仿真结果表明,在重负载条件下,改进协议中实时业务的时延比802．11DCF有大幅度的下降,网络吞吐量也有所提高。     

Efficient Broadcasting in Mobile Ad Hoc Networks

This paper presents two efficient flooding algorithms based on 1-hop neighbor information. In the first part of the paper, we consider sender-based flooding algorithms, specifically the algorithm proposed by Liu et al. In their paper, Liu et al. propose a sender-based flooding algorithm that can achieve local optimality by selecting the minimum number of forwarding nodes in the lowest computational time complexity O(n logn), where n is the number of neighbors. We show that this optimality only holds for a subclass of sender-based algorithms. We propose an efficient sender-based flooding algorithm based on 1-hop neighbor information that reduces the time complexity of computing forwarding nodes to O(n). In Liu's algorithm, n nodes are selected to forward the message in the worst case, whereas in our proposed algorithm, the number of forwarding nodes in the worst case is 11. In the second part of the paper we propose a simple and highly efficient receiver-based flooding algorithm. When nodes are uniformly distributed, we prove that the probability of two neighbor nodes broadcasting the same messageneighbor nodes broadcasting the same message exponentially decreases when the distance between them decreases or when the node density increases. The analytical results are confirmed using simulation.     

多源多中继无线网络中基于随机线性网络编码的调度方案

现有多中继无线网络中传输调度方案主要针对单信源且转发链路状态相同的情况,多采用顺序转发的调度方式,传输效率较低。针对此问题,该文提出一种基于随机线性网络编码的优先级调度方案。该方案在不同的传输阶段,利用信息包接收状态或编码向量之间的线性关系生成反馈信息,计算中继节点的有效信息包数。在转发链路状态不同的情况下,综合考虑各中继节点的有效信息与链路传输可靠性,确定优先级,从而完成调度。该方案实现了多中继对多信源信息的协同转发,在转发链路状态差异较大时,能自适应地选择最优转发节点和路径,提高信息包的传输成功率。仿真结果表明,相比传统基于单信源或顺序调度的方案,该方案能有效提高网络吞吐量,减少重传次数。